1

Continental J. Engineering Sciences 3:1 - 12, 2008 ©Wilolud Online Journals, 2008.

INVESTIGATIVE STUDY OF ARCHAEO-METALLURGY OF KATSINA STATE

A. B. Aliyu, Hassan Yunusa, A A Adamu Department of Mechanical Engineering, Bayero University, Kano, Nigeria

ABSTRACT This project studied both historical as well as metallurgical aspect of metal working. It compared the ancient metallurgical technology of Katsina state with modern ones; its development and collapse of the industry. Some metallurgical examinations and tests were carried out on some of the blacksmiths to asses the level of development attained by these practices. Based on the study carried out, ways of improvement were suggested. KEYWORDS: Archeometallurgy, Katsina State, Blacksmiths, Primitive Furnaces, Smelting, Smithing.

INTRODUCTION Iron smelting in Hausaland predated the Jihad of 1804. Available evidence indicated that Katsina zone of Hausaland, where iron working has been going on for over 1000 years (Okafor, 1997), was the most active in this activity. This is because of the abundant iron ore deposits found in most parts of this area. Notable in this area are Pauwa, Katsina and Lafiaro, where the ore deposits are found in stony lands. The introduction of steel during the colonial era put a halt to iron mining and smelting, and was in fact completely abandoned, with a very few of the miners and smelters turning to blacksmiths. The two most common ways of detecting the presence of the ore by the local miners were by noticing its presence on the earth’s surface and by noticing the ore’s particle-heaps deposited by ants around their habitats. The ore was then mined (usually by a group of miners and always during the dry season) by digging a trench to the depth at which the ore deposit was met. The mined ore was then transported to the area designated for smelting, usually where there was abundant presence of water, wood and grass. The smelting operation comprised of building a furnace, which is a granary-like structure made of fine clay and which usually took about ten days (including the drying period). Meanwhile, a ditch, about 20 ft deep was dug and filled with grasses. Next, about four nozzles (Tuyeres) were built around the ditch. The furnace was then placed over the ditch and nozzles. Next, about five baskets of charcoal were placed inside the furnace, followed by about nineteen baskets of the raw ore, on top of which substantial logs of hard wood were placed. Fire was then made and allowed to burn until the ore smelted into iron. This took between 30 and 36 hours. Normally, the slog product soaked away into the ground through the grasses. The resulting pig iron took 2 to 3 days to completely cool before it was removed. The pig iron was then sold to the blacksmiths who then used it to manufacture such iron wares as locks, guns, hoe blades, etc. This work is aimed at studying the ancient iron working processes in Katsina state of Nigeria, from ore mining stage through the smelting to the smithing stages. These processes would then be compared with the modern methods and ways of improving the ancient one suggested.

2

A. B. Aliyu et al: Continental J. Engineering Sciences 3:1 - 12, 2008 Table 1: Comparison of the primitive furnace with the modern blast furnace. Primitive Furnace Modern (Blast) Furnace The height of the primitive furnace was not more than 2m, and the diameter was about 0.5m at the top and 2m at the bottom.

The height of the blast furnace is about 20m or more from the bottom to the top of the furnace.

Made of clay mixed with grasses. Generally made of thick steel shell lined with refractory bricks on the inside.

Charcoal used as fuel. Coke used as fuel. The maximum temperature attained by any means did not exceed 1000ºC and as such only the slag could be melted while the spongy iron formed bloom.

Can attain up to 2000ºC and as such both the slag and iron can be melted as the melting point of iron is 1500º.

Each furnace was capable of smelting at most only about 0.3 tons of iron at a time and could be done in 30 to 36 hours.

Capable of producing substantial amount of iron on hourly basis, with the furnace operating for several years nonstop.

During smelting operation, special sand was used as flux which gave the slag some suitable composition.

Calcium carbonate or limonite is used as flux and the slag has suitable composition in iron reduction.

Had between 4 to 5 tuyeres and were bellows-driven and forced draught.

Has as many tuyeres as possible, depending on the capacity of the blast furnace and the tuyeres are forced draught.

A single furnace could only be used for smelting four times at the most after which it was discarded for a new one.

Once it is in use, it can be in operation for many years without shut down.

HISTORICAL BACKGROUND AND ARCHEOLOGICAL EVIDENCE The earliest known occurrence of iron smelting in tropical Africa comes from Taruga (southern Kaduna, Nigeria) and dated back to 400 BC. Evidence of the development of iron technology in Africa comes fro two sources: archeology and ethnography [Andah, 1997]. In Katsina state, there are many iron smelting sites [Okafor, 1997], including Katsina, Lafiaro, Daura, Kankara (Pauwa) and Tama, where many slag blocks, fragments of clay nozzles (tuyeres), baked red mud walls of furnaces, and other industrial debris could still be found today. In fact, the significant role played by the Kankara region in iron working is seen by some writers as the main iron production centre in the whole of Hausaland. Katsina smiths have been involved for many centuries in the manufacture of essential metal ware products for both local consumption and for sale outside the region. The production, organization, distribution, and exchange of these goods involved, at different stages, miners, smelters, dealers, traders from far and near, the smiths, and the commission agents. The smiths, as a rule, did not smelt or mine ores, which are normally done by professional ore miners and smelters. The smiths from rural areas would travel around the various mining camps to buy iron for themselves and for other smiths back home. The blacksmiths who were skilled enough to mine and smelt their own ore would first have to sought permission from their chief in the area. Perfection of skills which lead to very high skills was enhanced by the exchange of ideas between industrialists from other areas like Kano, Sokoto, and Zamfara who converged at these areas like Pauwa for production and manufacture of iron wares. There were also skills specializations by different groups dating back from the pre-colonial era. This is evidenced by the fact that smiths from Gwangwan and Kofar Kaura wards specialized in such horse-riding equipment as stirrups and swords; those from Kofar Keke in swords; Saulawa in manufacture of door locks; and those from Masanawa in agricultural implements like ploughs, hoes and axes. The skills were so perfected that hardly did the key to one lock unlocks another, for example.

3

A. B. Aliyu et al: Continental J. Engineering Sciences 3:1 - 12, 2008 Though smithing was basically a family profession that was passed down from generation to generation of the family, apprenticeship, involving others with no smithing background, was also practiced. The apprentice did not pay tuition and could come and go as he pleased. Table 2: Chemical constituent of slag from bloomery iron smelting

Constituent Sample 1 Sample 2 Mean weight (%) Standard

Deviation Mean weight (%) Standard

Deviation FeO 66.28 0.27 68.76 0.34 Al 2O3 7.26 0.79 7.67 0.53 MgO - - - - SiO2 21.39 0.60 21.70 0.13 TiO2 0.97 0.10 1.04 0.17 MnO 1.55 0.14 0.05 0.03 P2O5 0.82 0.06 0.46 0.09 CaO 1.06 0.11 0.17 0.02 S 0.05 0.07 - - V2O5 0.11 0.11 0.15 0.18 K2O 0.50 0.02 - - Total 99.99 - 100 -

The smiths market their products through middlemen who buy the products in bulk for sale in the markets. However, smiths located in the markets’ immediate environments, such as those at Gwangwan, could also sell their wares directly in the market. STAGES OF IRON WORKING Field visits were taken to various ancient mining, and smelting sites, as well at to some existing blacksmiths’ workshops. It was observed in particular, that the blacksmiths’ choice of materials, heat treatment sequences, and shaping and joining operations left some room for improvement if the potentials of iron working in these areas are to be fully realized. Source of Iron Throughout a great part of Africa (including Nigeria), there has been, especially in the past, an extensive tree cover to provide fuel, and sizable deposits of ores of iron are also found, extensively in the form of hematite or limonite which are also essential constituents of laterites and other widespread derived or residual rocks. Another source of iron extensively used by primitive smelters is magnetite. Magnetite occurs as a constituent of the river and stream sands in many parts of Africa, and can often be seen, after heavy rain, as a deposit of black sand on the beds of shallow streams. The relative iron content of these ores is: magnetite (Fe3O4), 72.4%; hematite (Fe2O3), 70%; and limonite, 20-55%. The iron ore resource of Katsina is mainly a residual ferrugnised laterite – a hard compact and sometimes perforated rusty brown rock that occurs in layers, either capping weathered inselbergs or as a layer below the top soil in some laterite pits. Important locations include Makurdi Hills, Dan-ali Hills, Lafiaro and Pauwa. This ferrugnised laterite contains the iron mineral limonite. It is, of course, low grade from the mineral content point of view. Before the introduction of European scrap iron, much of the iron worked by smiths in Katsina and other areas like Kano, were mined and smelted in southern Katsina. Katsina smelters also supplied iron to Sokoto and other places in Hausaland. The Primitive Furnace and Smelting Operations As far as can be deduced from archeological evidences, the shaft type of furnace seem to be the earliest, and it is the most widespread in areas of Katsina, Kano and Zaria in particular and in Hausaland in general. The quality of this furnace depends on the kind of earth used, how it was heat-

4

A. B. Aliyu et al: Continental J. Engineering Sciences 3:1 - 12, 2008 treated, and how many times it could be used. If it can be used more than one time, then it would be only the tuyeres that would require changing. The furnace was built of clay mixed with grass. It was usually 2 metres high (figures 1 and 2) and an average man could encircle it with his arms. It has a small hole about half way up through which happenings inside the furnace could be viewed and another hole at the bottom through Table 3: Hardness values from laboratory tests.

ROCKWELL HARDNESS (HRV) AVERAGE HARDNESS (HRV)

Sample 1 2 3

Unforged 50 49 50 49.67 Chisel (forged item)

98 100 97 98.33

Hoe blade (forged item)

91 85 89 88.33

which the slag ran into a pit. Air is blown into the furnace through openings at a level above the bottom. The space below the air entrance provided a place for the sponge to form, where it would not be exposed to oxygen from air, which otherwise would combine with the reduced iron to form iron oxide The furnaces were bellows-driven. The bellows consisted of two bladders made from goat skin, with wooden handles fixed to the tops and with wooden tubes leading from the bottom of the bellows into the tuyeres which delivered the air into the furnace. Conditions prevalent in the shaft furnace were favourable to carbon absorption: high temperatures could be attained and reduction of iron ore began at considerable level above the combustion zone so that any reduced iron would be in contact with hot carbon for a longer time at higher temperatures than say in the pit or hearth type furnaces. The carbon from charcoal used as fuel, apart from supplying the necessary heat, also provided the chemical agent to reduce the iron from its oxide, protected the reduced iron from being re-oxidized so long as it was surrounded by hot carbon; and could provide alloying material for the reduced iron to form iron-carbon alloys of several types. These furnaces have the limitations of not being able to attain melting point temperature of iron; excessive heat loss through the walls and top; absence of slag tapping provisions in some of them, which calls for demolition and rebuilding of another furnace whenever the slag pit was filled; cracking of the walls at high temperatures since they have no shields and so stopping the smelting operations to avoid collapse of the furnace; and negligible pre-heating of the air. Figure 1 depicts these primitive furnaces. Table 1 compares the primitive furnace with the modern blast furnace. Smelting – the reduction of iron ore – takes place at a temperature of about 700ºC in the primitive furnace. This temperature is by far below the melting point of iron (1500ºC). in the modern industrial blast furnaces, the iron from the ore separates from the slag (and being heavier than the later) runs to the bottom of the furnace from where it is poured into casting moulds to form pig iron while the slag is run off. The method of producing iron in the primitive furnace is much more complicated than it is in the modern furnace. In the former, iron ore together with a special charcoal (produced from hard wood) were charged into furnace from the top and then the charcoal was lighted. The carbon from the charcoal burns and combines with oxygen from the air to form carbon monoxide. The hot gas passes up through the furnace and reacts with the iron oxide (ore) by removing oxygen from it, forming carbon dioxide and leaving pure chemically deposited iron (bloom). The reduction process actually begins at very low temperature, probably about 450ºC [Enozie, 1992]. The reaction equations are:

5

A. B. Aliyu et al: Continental J. Engineering Sciences 3:1 - 12, 2008

232

2

323

Heat 22

COFeCOOFe

COOC

+→++→+

The iron produced in this process has not melted; it has been chemically deposited in very small quantities which, due to the influence of the higher temperature near the bottom, become soft and adhere to one another or to the slag and unconsumed charcoal to form a loosely coherent mass known as sponge iron.

Figure 1: A drawing of the primitive furnaces on a smelting site. Impurities in the iron ore, such as silica combined with some of the iron oxide for form a liquid siliceous slag of high iron content, at leas part of which permeated the pores of the sponge iron, while the remainder ran out of the furnace bottom opening into the pit. After a sponge of sufficient size had formed, it was suitable for making tools so the blacksmiths refined it. This was done by reheating the iron with charcoal and repeatedly hammering it so as to express the remaining slag and weld the iron crystals together. The smelting of iron is a task needing and using up much energy and very much complicated by ritual which, if not properly observed, it was believed, the smelting process would fail. Bloomery Slags Bloomery slags in the primitive iron smelting process were once solidified molten silicate matter that resulted from the reduction of iron ore, which was composed of gangue material from the iron ore, fuel ash and refractory materials. When chemically analyzed, slag from smelting operations contain higher proportion of silica than the that from smithing operations. On the other hand, smithing slag has a higher proportion of manganese than did that from smelting [Andah, 1997]. Tap slag was the most prominent in shaft furnace used in Hausaland in bloomery iron smelting. Here the furnace was provided with an aperture for draining the molten slag out of the furnace while the smelting was in progress. The molten slag solidified outside the furnace. Such tap slag was flattish in form with lava-like ripple appearance. Chemically, the bloomery slag was composed mainly of iron oxide and silicate which together made up over 90% of slag constituent. Iron silicate slag from bloomery iron smelting was generally fayalitic (2FeO.S2O2) in composition. However, there was slag in which MnO, MnO, or CaO replaced the FeO in the iron silicate to form manganese, magnesium, or calcium silicate respectively. In some other metal working operations such as smithing and forging of blooms in the hearth, as well as the smelting of copper and lead ores, where iron ore was used to flux the smelt, produced fayalitic slag. Table 2

6

A. B. Aliyu et al: Continental J. Engineering Sciences 3:1 - 12, 2008 shows the chemical constituents found in various samples of the slag from bloomery iron smelting sites that were analyzed. Factors upon which slag mineral composition depend were observed to include: ore composition; chemical composition of fuel used; chemical composition of the refractory material used; chemical composition of any flux(es) used; the rate of air blast; the state of the slag as it is removed from the furnace (i.e. whether it was tapped in molten state or removed after solidification in the furnace); and the surrounding conditions of the slag since it was formed. SMITHING While the blacksmiths worked mild steel and obtained their raw materials from the local miners and smelters, the whitesmiths – who worked brass, gold, silver, etc – obtained their raw materials mostly from imports from Asia, and Europe. Among this later smiths, tin was the only metal obtained and

Figure 2: Sections through a primitive furnace. smelted locally up to 1913 [Enozie, 1992]. On the other hand, blacksmithing is the one considered to be wholly indigenous before the eighteenth century. Though blacksmithing is an ancient craft who’s forging techniques is the progenitor of the various metal-forming operations in use today, the process among the local people still remains primitive and rudimentary that it is hardly employed as a viable means of commercial production of metal ware. The various operations undertaken by the local blacksmiths include the following: Heating: in which the work piece is buried in a mass of charcoal at the exhaust of the bellows in the hearth and then heated to cherry-red hotness – corresponding to temperatures in the austenite range – and held there for about 20 to 30 minutes. Forging: in which the heated piece is hammered, punched or chiseled into a desired shape. Casting: which is carried out only by the whitesmiths as the blacksmith is unable to reach sufficient temperatures to melt the steel in the hearth, whereas the whitesmith’s metals have lower melting temperatures and is able to cast metals. In the open mould method, the molten metal was poured into an open mould and allowed to solidify, after which the solid metal was hammered to strain-harden and then heated and bent to shape. This was mostly utilized to produce bangles. In the lost wax method, a model o the object was made and was then covered with clay mixed with termite earth. This was then baked, whereupon the wax ran out of the mould and leaving it exactly of the desired shape. The casting was then made by pouring the molten metal into the baked mould. After cooling, the mould was broken, leaving the casting intact.

7

A. B. Aliyu et al: Continental J. Engineering Sciences 3:1 - 12, 2008 Mixing the clay with termite earth made the clay more focused, thereby helping in eliminating cavity defects. This method has been revived in the last century in the casting of gas turbine blades. Tempering: for tools like the chisels in which only the cutting parts need hardening, the blacksmiths heat the tool to cherry-red hotness, and quenching only the cutting edge. The cooled end was then cleaned and the heat from the shank of the tool was allowed to temper the cutting edge to the correct colour, after which the whole tool was quenched. Normalizing: here, the blacksmith heated the steel to red hotness and soaked it for sometime – depending on the thickness of the article – in a medium such as water or oil. It was then allowed to cool in air. A softer material was obtained in the end. Joining: metals were joined by the smiths by brazing and welding. In brazing (and soldering), the two surfaces to be joined were held in place over fire and finely ground pieces of bottle glass (which acted as flux) was spread over the surfaces. A piece of brass (solder) was then placed at the top and heated until it melted and spread onto the spaces between the surfaces. A strong joint was formed after cooling.

Plate 1A: Unforged Sample (Normalized Structure)

Plate 1B: Forged Sample (From a hoe blade)

Plate 1C: Forged Sample (from a quenched chisel cutting edge)

In welding, the parts to be joined were immersed in wet clay sand (flux) and heated to cherry-red hotness and then the hot pieces were hammered to unite the surfaces over an anvil. The flux combined with the iron oxide produced by heating to high temperature and formed a fusible slag which was scattered by the hammer blows. Quenching: the local blacksmiths largely employed water as a quenching medium. Though rarely, they also used groundnut oil especially where the degree of hardness required was not appreciable. LABORATORY TESTS One sample each from the blacksmiths forge item and from the unforged material (the blacksmith’s input material) was laboratory-tested at the Materials Science Laboratory, Mechanical Engineering Department, Bayero University, Kano, Nigeria. May, 1995. The forged sample was sectioned, ground flat and rough-polished on glycerol-lubricated silicon carbide paper. The grinding and polishing were done very slowly to avoid heating and oxidation, the depth of grinding and polishing being sufficient to eliminate damage arising from specimen preparation. The sample from the unforged material was also similarly prepared for testing. The harness test was conducted on the samples using only the Rockwell B-scale, as the deformation and heat-treatment employed by the blacksmith was not expected to yield higher hardness in the mild steel he employed.

8

A. B. Aliyu et al: Continental J. Engineering Sciences 3:1 - 12, 2008 For the microstructure observations, the fine-polished and etched specimens were mounted on the metallurgical microscope and the observed images were sketched. The etching reagent used was 2% nitric acid-methyl alcohol. Test results are shown in Table 3 and in Appendix A. DECLINE OF THE INDIGENOUS IRON INDUSTRY No doubt, the coming into contact with Europeans contributed significantly to the decline of the iron smelting in Katsina. As some of the blacksmiths interviewed put it, that though tools made from locally smelted iron were stronger than those made from imported iron – obtained in forms of rods and bars from iron containers of paints, engine oil, corrugated iron sheets, etc – they preferred the imported iron because it was easy to work, cheap to buy and readily available. Among the factors that contributed to the decline include the following: The British Conquest Immediately after the conquest of Katsina emirate in 1900 by the British, the later prohibited the bearing and production weapons. This effectively cut the potential of the blacksmith by more than half since the society for which he worked was war-faring and mainly agrarian. Further, in 1902, the British enacted a lands proclamation edict number thirteen [Mukhtar, 1990] which vested ownership of all lands and the resources therein in the hands of Britain, which also regulates the utilization of the land and its resources. The edict deprived the entire people of the area the ownership of any unoccupied and uncultivated lands and also deprived them access to any minerals from the lands. This contributed immensely to the collapse of indigenous mining and smelting. For example, in 1925 [Mukhtar, 1990] in Pauwa, the colonial state not only made all independent mining illegal, but also closed down eighteen local iron smelting furnaces. The colonialists also established forest reserves where no wood was obtained for any purpose as well as taxing of the trees used in places not reserved. This made it further difficult for local smelting which depended largely on wood fuel, i.e. even if the smelting could be done illegally. The creation of boundaries by the British constituted barriers to population movements, interactions, trade and exchange of ideas and skills. Thus, trade between communities collapsed and so did the seasonal migration to the centres of iron mining and smelting. This was further aided by the imposition of discriminatory custom duties against local resources and products. These duties favoured European products whose markets gradually replaced those of their indigenous counterparts. The British, by its imports policy, flooded the markets with European scraps and manufactured goods. The supply and distribution of these to all areas in northern Nigeria were greatly increased after 1911 when the railway reached Zaria and Kano. This further contributed to the decline in local iron production. It is probable that by the end of the 1930’s, locally mined iron had been replaced almost completely by the imported scrap metal [Gregory, 1972]. Considering the poor economic status of the miners, smelters and blacksmiths, imported iron was not cheap by any standard. This, coupled with the special tax imposed on blacksmiths, forced many of them to abandon the craft for other professions. The few that held on to the craft resorted to securing metal supplies from the railways in Kano and Zaria. Consequently, theft of railway iron became rampant. Lastly, the maintenance of the emir’s palace and the central prison – a responsibility assigned to the city blacksmiths under the direction of the “Chief of Blacksmiths” – was taken over by the then newly established public works department. These artisans thus lost their function and importance. The result of all these factors was the stagnation and deterioration of the techniques and skills involved in the industry, leading finally to its collapse. Other Factors 1. Importation of Firearms: One of the early salient factors for the decline of iron working is the importation of firearms. During the last decade of the nineteenth century, imported firearms became generally available in northern Nigeria. Thus, the market for the locally made ones by the blacksmiths

9

A. B. Aliyu et al: Continental J. Engineering Sciences 3:1 - 12, 2008 rapidly declined as they were forced to abandon the making of such items as paddled amour, spears and swords mostly used for defence and hunting. 2. Lack of Planned Apprenticeship: Apprenticeship was very informal: no binding contract; no payment of fees involved; and no fixed apprenticeship duration. So the apprentice may come and go as he pleases and may pay little or no attention to the craft. The long-term impact of this is that the art would be poorly transmitted from generation to generation. 3. Lack of Research Culture: No body – not even the artisans themselves – engaged in research in this area to seek to improve the quality of their work. Thus, no one sought to know why things happened the way they do; certainly, curiosity about certain aspects of their work would have enlightened them on not only how things happened and so improve on their work and products, but also pave way for future developments. 4 Conservatism: The artisans were not willing to be introduced to new technological innovations, even if those things meant improving on the primitive methods. The attitude was one of “whatever was good for our ancestors is also good for us”. For example, they used charcoal from ‘Kirya’ tree (Pro Sopic Africa) which was scarce and obtained from long distances, when coke was more available and effective and could have been used. 5. Lack of Encouragement/Government Assistance: Because these artisans largely depended for their means of livelihood more on farming than on the art of iron working, their key functions, importance and value to themselves and to the society were eclipsed. They ought to have been encouraged by government, both financially and by way of easy access to the resources they used. These would have boosted their production capacity. 6. Change of Attitude: Because of the poor economic status of the smiths and smelters, the later generations of young men were less interested in these arts and would rather look for jobs with better prospect of pay. 7. No Formation of Guilds: In the words of [Yusuf, 1996], “generally, in the whole of Hausaland, there was the lack of highly developed and regular cooperation between the artisans in the conventional guild. Instead, we had a situation in which each of the separated clusters of blacksmiths was essentially autonomous, with the individual smiths of each group organizing their work quite independently of each other, and setting their own prices and standards of production”. This limited the transfer of skills between artisans and this further retarded the progress of the craft. In the equivalent European industry, it is instructive to note that, in addition to the machinery, a most decisive factor in the growth of the industry was the change-over from domestic production to the factory system, with the guild making the intermediate stage. DISCUSSION The austenite phase change is the most critical in the diversification of mechanical properties of steel in the sense that every equilibrium phase transformation has to pass through this phase. The measure, therefore, of the adequacy of the blacksmith’s heat treatment depends largely on whether or not the austenite region was attained. If it is then air-cooled, the product should reveal fine-pearlite structure. Temperature A comparison of plate 1A with other plates (1B, and 1C) reveals that the equilibrium (pearlite) phase transformation occurred in the forged samples – indicating the austenite phase change. Hence, the blacksmith’s operations are viable as a means of imparting versatile micro-structures and therefore mechanical properties of the steel. Degree of Deformation This is limited by human strength, as well as by the blacksmith’s disinclination to go to higher temperatures such as yellow-white hotness or to re-heat the job frequently between forging blows. However, remarkable extents of deformation were achieved in some cases, such as when a digger or a

10

A. B. Aliyu et al: Continental J. Engineering Sciences 3:1 - 12, 2008 hoe is flattened from 2-inch round bar to a bladed end only 1/8 as thick as the original thickness. This represents a very severe deformation. Matchets, sickles, axes and hoes, unless they are made from coils (strips), which are not yet made locally, represent even more severe deformations. Thus, the blacksmith’s operations are adequate in this regard. The degree of deformation gives rise to the significant alteration of mechanical properties evident in Table 3. Mechanical Properties The result of hardness test and the micro-structure details are shown in Table 3 and on Plates 1A, 1B and 1C, respectively. The hardness is seen to be higher in the forged samples than in the unforged samples. This means that the tensile strength is also higher in the forged samples. Since ductility decreases with increasing hardness, it can be said that the ductility of the forged samples would be lower compared to the unforged material. The high strength is significant and is in agreement with expectation. The martensite structure observed in plate 1C indicates that the sample was quenched and further confirms that austenite will be obtained without the materials being heated to the austenite range. The clear resolution of pearlite in these structures indicates that equilibrated plain carbon steels. The microstructure results in plates 1A to 1C all point to a probable composition of the beginning of material – mild steel. Remarkable directional property was also achieved where the grains were observed to elongate in the direction of forging. This directionality is parallel to the force that will be applied to the tool in its working life, which means longer life for the tool. Uniformity of Deformation In blacksmithing, deformation of material is very severe and it is seldom uniform over the entire forged zone. This is evident in the significant scatter of the data in Table 3. It was observed that the blacksmith’s forging blows are far from uniformity in the hot zone. The piece is usually turned over in between blows delivered by a hammer. More often than not, the job is done by one man for better coordination; the job is held in one hand and the hammer in the other hand. Generally, only five to ten blows are delivered before the piece cools and hardens. The severe deformation imparted after the workpiece has cooled below the annealing temperature range only serve to produce severe work-hardening. The result is patchy surface finish and inhomogeneous internal deformation, leading to inhomogeneity in mechanical properties. Such inhomogeneous deformation of steel, couple with the normalizing treatment (air-cooling) and failure to perform follow-up anneal, means a good deal of residual stresses in the product. The worsened by the fact that only few implements are heated and forged all over; in most cases only the working end (blade edge) is heated and forged. Thus, severe variation in structure and properties exist over the implement. The result does not only impair mechanical properties, but also makes the implement prone to corrosion. This limits long-term use, particularly in sea water or in salt-laden air of coastal and tropical areas. Inhomogeneity of structure and properties in blacksmith’s products is probably the greatest shortcoming in the work of the blacksmiths. Starting Material The blacksmith’s choice of a starting material is predicated upon convenience, availability and ease of hot-deformation. He comes up with mild, plain carbon steel. This is an excellent choice from the standpoint of versatility in the development of structure and property as discussed above. He could easily generate a great variety in the mechanical properties, hence applications of his products using this starting material; if only he understood the power of heat treatment in materials. The hardness and strength required in the blacksmith’s products are not so high as to necessitate going to alloy or tool steels for the mean time. However, corrosion resistance and aesthetic appeal might become important factors; in that case, plain carbon steels would no longer be adequate. It is unlikely, however, that a blacksmith untutored in the science of metal alloying could master the intricacies of delicate phase balance needed in working with such alloys as stainless steels. General Discussion An attempt has been made here to present an account of local iron working processes as accurately as possible. Until quite recently, and even now, properly recorded processes could probably be counted on

11

A. B. Aliyu et al: Continental J. Engineering Sciences 3:1 - 12, 2008 the fingers of one’s hand. Different versions of the iron smelting processes were given by different smiths interviewed. There are many references to iron-smelting in journals concerned with iron and anthropology, but very often, the accounts are clearly inaccurate in certain respects, and it then becomes difficult to place any reliability on them. A common mistake is to describe how the iron melts and runs into a lump at the bottom of the furnace into moulds which are placed around the furnace. In truth, the iron never melts in primitive furnace; if it did, it then would have formed cast iron, which would be useless to a smith because he would be unable to work it by the methods at his disposal. The very few remaining smiths still practicing here today posses still posses the artifice, skill and talent, although most of them are illiterates with regard to western education which would have helped them in improving their artifice. RECOMMENDATION The main aim of this work has been to study the processes employed in iron working in Katsina state right from the iron ore minting to smelting and through to blacksmithing stages; to compare these processes with the modern methods; to give the processes some scientific explanation; and to suggest ways by which the some of the processes still being practiced from the old ways can be improved upon. Some of the suggested improvements considered fundamental are given below. Temperature Measuring Techniques: The major essence of heat-treatment is to alter the properties of a material and this can be achieved largely by control of temperature in the heating process, time for soaking, and the cooling speed. There is therefore the need to know the temperatures attained during heating. Bearing in mind that the local smiths cannot read temperature-measuring instruments like the thermometer, a more practical way to guide them on temperature estimations is needed. Thus, such methods suggested include: Indicating paints and crayons (for small-scale heat-treatment): which change colour or appearance at given temperature ranges. Hence, the paint or crayon could be used to make a mark on the workpiece. Temper Colours: when a quenched steel is heated, it changes colour which is dependent on the temperature reached. This method is similar to the first one; so all the smiths need do is to drop a quenched steel in the hearth and observe the colour it turns to have an idea of the temperature attained. This method would be applicable to only steel and no other metal. Carburizing: A method of carburizing is to grind charcoal and using this to cover the workpiece in a casing (whose material can withstand the carburizing temperatures) and then heating to the carburizing temperature. The blacksmiths could be taught this simple method. Casting: In small casting small items like plates and rings the blacksmiths use the lost wax method. In this process, the wax extension above the wax ring acts as a riser and therefore there are no problems of shrinkage. However, for bigger castings, the blacksmith needs to be told to provide a riser to compensate the shrinkage effects. Quenching methods: To minimize distortions, the blacksmith needs to know that long cylindrical articles need to be quenched vertically; flat section edge-wise; and that thick ends should enter the bath first. Eliminating soft spots: to prevent steam bubbles forming soft spots, the quenching bath should be agitated. In other words, components should be shaken well in the medium during quenching. Forging: this should be carried out by a simple mechanical press so as to have uniformity in the deformation or by using a simple drop forging mechanism, in order to save effort. Quenching media: the two media that the smiths are familiar with are water and groundnut oil. He needs to be taught that some modifications like adding salt to the water or warming the water will alter the cooling speed of the medium. The oils to could be extended to include mineral, animal and plant oils, each of which has different cooling speed.

12

A. B. Aliyu et al: Continental J. Engineering Sciences 3:1 - 12, 2008 Furnace: improvements in furnace design should be based on the limitations discussed earlier. The blowers, for example, may replace the bellows in the smiths forge so as to reduce the effort. CONCLUSION The technical aspects of the smelting and smithing processes were discussed right from the mining of the ore, through smelting to the smithing stages. The smith’s methods of hot-working, degrees of deformation, and casting methods among others were also critically analyzed and suggestions were put forward. For sound uniform and versatile development of microstructures and mechanical properties in the entire products it is very necessary for the smith to adopt a structural approach to pre- and post-fabrication heat treatment. For this, the smiths need some scientific knowledge of the behaviours of metals and alloys. In view of the foregoing study, metallurgical industries that exist today are only remnants of the viable, sound and developing industries of the pre-colonial period. We have also seen how and why the industries declined and the point in time this declination began. Also, a concrete basis for development could be established on a foundation of viable indigenous industries and technology. The professional experience and spirit of excellence of this practice could be used to assist in laying that foundation. The past is gone and cannot be retrieved or revived but its spirit and experience can be borrowed to transform our present situation. REFERENCE Andah, B. W. (1997) ‘The Epistemology of West African Settlements’. West African Journal of Archeology, University of Nigeria, Nsukka. Pp 32 – 51. Enozie, F. (1992) ‘Early Iron Technology in Igboland’. West African Journal of Archeology, University of Nigeria, Nsukka. Pp 88. Gregory, C. E. (1972) ‘A Concise History of Mining’. Pergaman. Mukhtar, M. (1990) ‘The Decline and Collapse of Indigenous Iron Industries in Northern Nigeria, 1903 – 1989 AD’. Smelting and Smithing, Kano, February, 1990. Okafor, E. E. (1997) ‘Early Iron Smelting in Africa’. West African Journal of Archeology, University of Nigeria, Nsukka. Pp 83 – 97. Terkel, R. ‘Principles of Extractive Metallurgy’. McGraw-Hill Book Company, London. 1983. Yusuf, J. K. (1996) ‘Bi-annual Historical and Cultural Magazine’. History and Culture Bureau, Katsina. Pp 26 – 36. Received for Publication: 10/03/2007 Accepted for Publication: 05/06/2007 Corresponding Author: A. B. Aliyu, Department of Mechanical Engineering, Bayero University, Kano, Nigeria E-mail - abaliyu@yahoo.com

13

Continental J. Engineering Sciences 3:13 - 20, 2008 ©Wilolud Online Journals, 2008.

THE APPRAISAL OF LOCAL FOOD PACKAGING MATERIALS IN NIGERIA

Adejumo, B.A. and Ola F.A. Department of Agricultural Engineering, P.M.B 4000, Ladoke Akintola University of Technology,

Ogbomoso Nigeria.

ABSTRACT Packaging is a complex subject and its role to the food industry and to the consumers includes protection, containment, transportation, preservation, and advertisement to the food industry. Defective packaging has the potential of negating all the food processor has attempted to accomplish by the most meticulous method of manufacturing processes. Nigerians have diverse ready-to-eat foods, diet and drinks varying from one tribe and geographical locations to another, with different packing materials and methods adopted. The aim of this work is to appraise the various properties of the local food packaging material used in Nigeria with particular reference to its suitability to the packaged food. A survey was carried out to ascertain the various type of local packaging materials used in Nigeria; samples of locally prepared and packaged foods were purchased from various sales outlets in Ogbomoso town, southwest Nigeria; the samples were stored at room temperature. Results shows that the common type of materials used to package food in Nigeria includes discarded bottles and jars, old stock of paper prints, leaves, maize-sheath, glass-sided boxes, jute sacks, poly sacks, polyethylene bags among others. The advantages of these materials includes availability and low cost price; while the disadvantage includes easy contamination of packaged food ,easy deterioration of packaging materials, easy spillage of packaged products, poor shelf-life of packaged food among others. It is observed that the role of packaging is not accomplished in the use of these materials; also no standard of regulatory body has been effective in ensuring the safety of ready-to-eat food. KEY WORDS: Bottles and jars, food, glass-sided boxes, leaves, sack, paper, plastic bags.

INTRODUCTION Packaging is a complex subject, it has been defined in several ways and its role to the food industry and imperativeness to the consumer highlighted to include protection, containment, transportation, preservation and advertisement to the food industry. Karel and Heidelbaugh (1975) in their view indicated the imperativeness of food package as an essential element requiring adequate attention to forestall the potential of defective packaging negating all a food processor has attempted to accomplish by the most meticulous forms of manufacturing processes. Food packaging is known to employ a very wide variety of materials including the rigid metals (Cans and drums), flexible metal (aluminum and tin foils), glass (jars and bottles), rigid and semi-rigid plastics (canisters and squeeze bottles) (BPF, 2006). Others include flexible plastic of a wide variety of types that include pouches, and meat wrappers, rigid board, paper and wood products. Flexible paper and laminates or multi-layers may combine paper, plastic and foils to achieve properties unattainable with any single component (Porter, 1986).Food packaging has indeed been adjudged to assume a complex form in recent centuries; sophisticated industries have evolved to meet up with the divergent needs of food products. As technological know–how appreciates, several renown food industries in conjunction with several technological universities have immensely re-oriented the food packaging phenomena (Oyelade, 2005).

14

Adejumo, B.A. and Ola F.A: Continental J. Engineering Sciences 3:13 - 20, 2008 Several earlier workers have highlighted factors that influence the choice of food packaging materials such as geometric properties (shape and size), chemical property (pH), Physical properties (color, aero and hydrodynamic properties.) and thermal properties (Porter, 1986), Essentially, the geometric features of food are known to be important in packaging, in controlling fill – in weight, freezing and canning among others. The pH level of the food product intended to be packaged known to be either its

Plate 1: Roasted ground nut packaged in bottles

degree of alkalinity or acidity is of considerable importance. This is important because acidic food products have the tendency to react with certain element of the packaging material, which can lead to a sort of contamination (Porter, 1986). The colour, aero and hydro – dynamic properties due to their influence on food products particularly in terms of general acceptability are also relatively significant in packaging technology. Accordingly, the density and porosity of the food material to be packaged determines greatly how the packaging material will be. The porosity of the material has tendency to influence the moisture sorption characteristic of the food products stored, hereby having a cumulative effect on the shelf - life of the food products. Factors known to influence the choice of packaging material of food products include permeability characteristic, mechanical strength, light transmission and temperature change. Thus, the degree of permeability of the packages to water vapor, gases and volatile odor compounds according to Porter (1986), is pertinent in packaging consideration. Food with high equilibrium relative humidity such as meat and cheese will tend to loose moisture to the atmosphere, which can result in a loss of weight and deterioration in appearance and texture. (Klicka, 1974). Products with low equilibrium relative humidity tend to absorb moisture particularly in high humidity atmospheres and this can cause significant textural distortion Foods with high fatty acids require a greaseproof package to prevent grease or oil spoiling the appearance of the pack and possibly damaging the printing and decoration. Grease proof and vegetable parchment papers and hydrophilic films provide varying degrees of grease proofness for different application (Hernandz-Munoz et al 1999) Also; package material should be able to withstand the change in temperature which is likely to be encountered without any loss in performance or appearance. Therefore the rate of change of temperature and the type of heat may influence the choice of packaging material (Guise, 1989). Shelf-life is explained in relation to the period of time during which the food product will remain safe and retain desired sensory, chemical, physical and microbiological characteristics and comply with any label declaration of nutritional data, when stored under the recommended conditions (IFST, 1992). Shelf life of a product is determined by a great deal of developmental work to arrive at what is termed adequate and satisfactory. Over the years, the forecasting of shelf – life has become increasingly important with serious consequences if incorrect. It is recognized that each type of food products needs its own procedure and methods by which such forecasting is done (Blendford, 1992).

15

Adejumo, B.A. and Ola F.A: Continental J. Engineering Sciences 3:13 - 20, 2008 The importance of shelf-life should therefore be tenaciously considered with respect to each of the significant groups involved in the food chain. The groups include the consumer, growers, other material suppliers, manufacturers, distributors (wholesalers and caterer) and retailers. For the distributors, wholesalers, and caterers in particular, the shelf life of a food product is intimately linked to the distribution systems in addition to the basic facts that different types of products require different types of distribution. Also in any given distribution systems, changes in the climatic conditions, handling practices and abuse can have drastic effects on products shelf-life. A total quality in the

Plate2 (a): Agidi (made from maize wrapped in leaves (b) Agidi with fungi growth after 4 days of storage

system will need to extend right through the distribution system and it has potential of becoming the weakest part of the chain which stretches from manufacture to the consumer. In relation to this, there are special problems of distribution in the rural areas. The wholesale and catering sectors also have the potential of representing major vulnerable areas within the food chain. This is because where sufficient control is lacking, valuable shelf-life can be lost (IFST, 1992). However in Nigeria there are diverse and numerous types of locally produced ready-to-eat foods sold in public places for immediate consumption. The packagings of these foods are usually meant for containment with little or no attention paid to the safety of the consumers and the shelf-life of the food. The hygienic state of the packaging materials and its appropriateness for the food products are not considered in its selection. The role of packaging in the food industry which includes protection, containments, transportation, preservation and advertisement are not achieved in all most all of the packaging method used in Nigeria. This in turn results in a huge loss of the food product not only during packaging processes but also during transportation and sales. The only regulatory body in Nigeria, “National Agency for Food and Drug Administration Control” (NAFDAC) has made tremendous progress in controlling the safety aspect in some of the food industry in Nigeria, such as in the confectionaries, sachet water industry and pharmaceutical industry. However, little or no efforts are made on the local food industry which is the most common in the country. There is a need therefore to analyze the properties of the various types of food packaging materials used and their suitability to the packaged food MATERIALS AND METHODS. A survey of the various types of locally available food packaging materials was carried out to investigate and determine (i ) the properties of the various types of food packaging materials, (ii) their advantages and disadvantages, (iii) the effects of these materials on the food products,(iv) their suitability for the food products,(v) health and safety standards. The experiment was set up in the process laboratory of the department of Agricultural Engineering LAUTECH, Ogbomoso. Fresh samples of locally prepared food items were obtained from the sales outlets in the local markets, in Ogbomoso. The collected food items were then packaged in different packaging materials and stored at a temperature range of 28.5 to 32.00C and a relative humidity range of 65.5 to 75.0 %. The ambient condition was determined using a HM 34C Humidity and temperature meter. Observations were made

16

Adejumo, B.A. and Ola F.A: Continental J. Engineering Sciences 3:13 - 20, 2008 of the variations in the physical properties of the food and the packaging material to ascertain their suitability for the packaged food. RESULTS AND DISCUSSIONS. The results of the survey showed that virtually all the food products packaged by the local processors and vendors in Nigeria are unlabelled. No indication is given of the name of the products, its source or its composition nor any information on appropriate storage conditions or instruction for use. This is one reason street foods are displayed open and unwrapped. Sellers and consumers alike take this for granted.

Plate 3(a): Donkunu wrapped in maize sheath (b) Donkunu having fungi growth after 4days of storage

The packaging materials used by food vendor in Nigeria include both flexible and rigid types. A large proportion of ready to eat foods are packed in soft or flexible materials including broad leaves, paper and plastic film wraps. The principal hard or rigid containers used on a large scale are glass and bottles. Glass-sided boxes, cane baskets and jutes or woven plastic sacks are also used in the bulk packaging of products such as smoked fish and gari, flour respectively. The various types of food packaging materials, types of food packaged, their characteristics, advantages and disadvantages are as classified and discussed below: Packaging in hard containers. Jars and bottles. Glass containers used for food includes old jars and bottles that originally held manufactured products such as beer, soft drinks, cream and pomade. They are obtained from dealers in discarded containers, who collect them from homes, and in some cases, from refuse dumps. Jars and bottles are used even if they have minor defects at the top. They do not have any special crown or cover. Products packaged in bottles and jars includes roasted groundnut, as shown in Plate 1(a), palm wine, ”kunu”(local drink produced from cereals),Burukutu”(local alcoholic drink produced from cereals),local gin, ”Zobo”(local drink produced from Roselle plant) among others.

In general, the food packaged in bottles and jars contains natural or added sugar and therefore attract flies. Unfortunately, the products packaged are not sterilized before or after it is packaged and may remain uncovered during sales. With the exception of few drinks, which are strong liquor, the products have a very short shelf life at ambient temperatures and are meant to be sold within a day.

Glass containers are re-used as long as they remain undamaged. They do not react with foods and can be washed. Products packed in glass have an aesthetic appeal. Products sold in glass containers are not labeled. Purchase and use therefore depends on previous experience with or knowledge of the foods.

17

Adejumo, B.A. and Ola F.A: Continental J. Engineering Sciences 3:13 - 20, 2008

Glass-sided boxes.

A variety of ready to eat foods are displayed for sale in large boxes with transparent glass sides. Over the last few years these boxes have become popular for the sale of pastries and other fried or baked foods such as puff-puff, Akara,(beans-cake), groundnuts, pop corn, doughnut, pies, and so on. These items previously were kept in open trays, large pans and bowls and many vendors still use these containers. The base and top of the boxes are made of wood, which holds one or more glass in place. The boxes are available in sizes of about 20x30cm with a height of 10 to 30cm or larger. They may be opened either at the top or from the sides. These boxes protect the food from flies and dirt. This has improved the way in which foods are displayed to customers. However, it may be warm and damp inside the boxes and frequent opening and closing admits flies. Also, the foods may be handled many times by different customers for inspection before purchase, such practices provides avenues for contamination

Plate 4(a): Iru (locust beans seed) wrapped in leaves. (b) Decomposed Iru with maggot after storing for 5-days

and microbial growth. However some of these boxes which are stationary are usually lighted with electrical bulb to provide warmth for the product and to make it visible at night. Packaging in flexible material. Leaves. Leaves commonly used for wrapping food include those of Thespesia populnea (malvaceae family), Marantodea spp (marantacaeae family) and plantain (Musa sinensis) and the sheaths of maize (corn, Zea mays). Some items are packaged raw before cooking, e.g. moimoin, ekuru, while others are wrapped in leaves after cooking while they are still hot e.g. Agidi.as shown in plate 2a. Fungi growth occurs in the product after four days in storage as shown in figure 2b. Donkunu, which is another maize product are usually wrapped in maize sheath (plate 3a), the product also shows fungi growth after three days of storage as shown in plate 3b. Iru, which is a local food seasoning is produced from fermented locust beans seed, are usually wrapped and sold in leaves are as shown in plate 4a. The product shows the presence of maggots after three days of storage at ambient atmospheric conditions as shown in plate 4b. Products wrapped in leaves after cooking generally have a shelf life of two to three days. Cooked rice and beans are stored in bulk in a large pan and sold wrapped in leaves of T.populnea. They cannot be stored for more than 12 hours in the leaves. Leaves for packaging are poorly handled and transported. They are often dirty and are kept in the open with little or no provision for washing before use. They may therefore be a source of microbial contamination of food. When broad leaves are stored for more than a week they deteriorate through drying out or decay.

18

Adejumo, B.A. and Ola F.A: Continental J. Engineering Sciences 3:13 - 20, 2008 Paper. Paper is used extensively to package a variety of ready to eat foods; with newsprint the most, commonly used. Paper wrappers are not pre-formed into any shape, but pieces are torn from a bigger sheet depending on the type of products. Akara (Beans-cake) are usually displayed in open trays and sold wrapped in newspaper (plate 5a). The newspaper print usually stains the food wrapped in them. The akara shows fungi growth after three days of storage as shown in plate 5b.

From the point of view of sanitation, the quality of paper is generally poor. Any old newspaper, multi-wall Portland cement sacks, magazine and old stationary from schools and offices are used. The Paper is not stored properly and cannot be cleaned. Such poor hygienic practices coupled with the harmful effect of printing ink make the use of paper for wrapping food a health hazard. The product packaged in paper includes Akara, fish (smoked or fried), pastries such as doughnuts, meat pies, cakes, puff-puff etc, bread, yam (fried or roasted) groundnut etc. The foods that are wrapped in paper are normally displayed in a pan, tray or transparent glass box and are wrapped in paper when purchased. The paper facilitates handling of the product but provides very little protection from damage or spoilage. Parcels may be loose and the food can easily spill out.

Plate 5 (a) Akara wrapped and sold in (b) Decomposing Akara with mould growth after

newspaper 3-days of storage

Plastic bags. Transparent plastic films formed into bags are becoming increasingly important in the packaging of a variety of foods. Low density polyethylene (commonly called polyethylene) is the best known. The adoption of these bags in packaging has significantly improved the display of ready-to-eat foods from aesthetic and hygienic point of view. Unfortunately, many food vendors are not familiar with the suitability or otherwise of the various types of plastic films for different products. This can however lead to deterioration in quality of the food during storage.

Polyethylene bags are manufactured locally and are available in different sizes, ranging from narrow strips of 3x5cm to larger bags measuring 25x40cm. These films wraps are desirable for packaging food because they are much less permeable to water vapour and gases than paper and leaves and are chemically inactive with food. They are used to package both solid and liquid foods. Polyethylene bags are useful for dry products such as gari, sugar, milk and cocoa powder e.g. bourvita, as the items remain dry for a long time if properly sealed. Since heat-sealing devices are not readily available, for many vendors, the open ends of the bags are usually tied into firm knots after the food is inserted.

Bread and other pastries are packed in polyethylene bags on a large scale. Many vendors expose their products to the sun while sealed in the bags. Moisture condenses inside the bags, and this facilitates mould growth. Sometimes air is blown into bags with the mouth to open them. This introduces vapour and microorganisms, which sets the stage for spoilage when foods are placed in the bags.

19

Adejumo, B.A. and Ola F.A: Continental J. Engineering Sciences 3:13 - 20, 2008 Home-made ice lollies, which are commonly sold in plastic cups and beverages such as kunu zobo, normally served in calabashes, are now sometimes packaged in small polyethylene bags for sale. Water is also sold in plastic bags in response to official directives aimed at curbing the unhygienic practice of using a single cup to distribute water to many customers. Some vendors package vegetables such as carrot, cabbage and tomatoes, in polyethylene bags with tied ends this speed the rate of deterioration since the exchange of moisture and gas with the atmosphere is cut off.

Heavier-weight polyethylene film wraps have limited application for food except for bulk packaging or covering such items as cooked rice, boiled yam, boiled corn, porridge and others that require heat and moisture to be retained. Sacks. The commonly used sacks in Nigeria are the jute and poly sacks. They are used to packaged crops such as cocoa, groundnuts, maize, guinea corn, rice, beans, gari among others. They are locally manufactured or obtained from discarded stock. It makes bulk packaging and transportation of crops easy. However, it gets easily torn due to continuous handling and re-uses leading to losses of products during storage and transportation CONCLUSIONS Food packaging materials used in Nigeria are though cheap and readily available, but are however unhygienic, easily depreciable and leads to losses of the packaged food. The packages of most ready-to-eat foods primarily serve as containers for the products. They are normally not intended as a means of extending shelf-life. The development of suitable packaging materials for most traditional staples is hindered by lack of standards. Variations exist in the composition, shape, weight, and methods of preparation of products from different sources; and so it is not easy to design simple, inexpensive ready-made containers for such a wide range of items. There are no regulatory bodies controlling the packaging and sales of ready-to-eat food, hence putting the health of the consumers at risk. The Nigerian government should put in place a body to regulate the packaging and safety standards for ready-to-eat foods. This will help in safe guarding the health of a common Nigeria. REFERENCES Blenford, D. F. (1992). In Shelf Life of Foods Guideline for its Determination and Prediction. A

Publication of the Institute of Food Science and Technology. U.K. British Plastics Federation – BPF (1st Dec.2006): Plastic packaging www.bpf.co.uk. Guise,B (1989). Microwave Pasteurization. Food Processing.58 (6):37-38 Hernandz-Munoz,P;Catala,R and Gavara,R (1999). Effect of Sorbed Oil Food Aroma Loss Through Packaging Materials. Journal of Agric.Food Chem..47(10) 4370-4374. IFST (1992). Shelf – Life of Foods – Guidelines for its Determination and Production. A Publication of

the Institute of Food Science and Technology (U.K). Klicka, M.V(1974). Space food and their development.In:Encyclopedia of Food Tech.AVI Publishing

Co.Westport Connecticus. Karel, M. and Heidelbaugh, N. D. (1975). Effects of Packaging and Nutrients in Nutritional Evaluation of

Food Processing. 2nd Edition. AVI Publishing Co. Westport, Connecticus. Oyelade, O. J. (2005): Moisture Sorption Phenomena and their Effects on Film Packaging of Cassava,

(Manihot esculenta, Crantz), Yam (Discorea rotundata, Poir) and Maize (Zea mays, Linn) Flour. Unpublished Ph.D Thesis. Department of Agric Engineering, University of Ibadan, Nigeria.

Porter, N. N. (1986). Food Science. 4th Edition. AVI Publications. Westport Connecticut. 590 – 597

20

Adejumo, B.A. and Ola F.A: Continental J. Engineering Sciences 3:13 - 20, 2008 Boko, M and Heideveld,A (1997) Introducing Leaf Packaging in the Netherlands, A Survey.A UNB/ UVA

/ UNEP-WG-SPD Collaborative Project, National University Benin (UNB) Received for Publication: 20/01/2008 Accepted for Publication: 05/03/2008 Corresponding Author: Adejumo, B.A. Department of Agricultural Engineering, P.M.B 4000, Ladoke Akintola University of Technology, Ogbomoso Nigeria. E-mail:- funmibitan@yahoo.com

21

Continental J. Applied Sciences 3: 21 - 29, 2008 ©Wilolud Online Journals, 2008.

DESIGN CONSTRUCTION AND TESTING OF AN INCREMENTAL SHAFT ENCODER FOR MEASUREMENT OF ANGULAR VELOCITY OF A SHAFT

Danladi A and Nathan C +Department of Physics, Adamawa State University, Mubi and Department of Agricultural Engineering,

Adamawa State College of Agriculture, Mubi

ABSTRACT An incremental shaft encoder has been designed and developed for measuring angular velocity of a shaft. The construction of the circuit was achieved using disc of a plastic materials with fifteen slots. Infrared light emitting diode, comparator, photo transistor (sensor), 555 timer, encoder, decoder, differentiator (control logic) and display. Bubble resolver was also included in the circuits to eliminate ± 1 counting error which is inherent in most digital device. The incremental shaft encoder designed and developed was able to measure maximum speed of 2500rpm and the corresponding frequency of 625Hz of a 12V dc motor after proper calibration in laboratory and testing. The circuit designed and developed is a prototype of an industrial incremental shaft encoder, which replace the imported incremental shaft encoders because of its reliability. KEYWORD: Speed (rpm), Frequency (Hz), digital instrument

INTRODUCTION Today in the field of electronic instrumentation measurement, digital electronic instruments are preferred instead of analogue instruments, the use of electronic instruments enhance accuracy of measurement, minimizes loading effect and reducing electrical noise (Efedua, 2002). Incremental shaft encoder is used generally to monitor the speed of motors and generators shaft, this work utilized a practical arrangement of incremental shaft using opto-interupt device(OID); opto-interrupt device is a device that combines light emitting diode (LED) and photo transistor in close proximity (Efedua, 2002). The OID shown in fig. 1 is a package configuration equally spaced slots around the disc which allow light from the light emitting diode to reach the photo sensor. The rotating disc attached to the shaft of a motor is usually non-conducting materials. If there are disc has 15 slots around the disc, the OID output is 15 pulses for each complete rotation of the disc. The set may be used to sense the change in angular position of a motor shaft or speed of the motor. For regular spaced slots in the disc, the angular interval between any slots may be 360/n degree (John, 2002). Thus if there are 15 slots for example, the slot are spaced 240 interval. This is the maximum angular displacement that can be detected. A count of total number of pulses thus relates the angular displacement of the shaft. If the motor speed is ω revolution per minutes or ω/60 revolution per second, the frequency of the pulse may be expressed as

60

ωnf = (1)

Where n is the number of pulses (Thomas, 2001)

22

Danladi A and Nathan C: Continental J. Applied Sciences 3: 21 - 29, 2008

Fig. 1: Block diagram of an incremental shaft encoder DESIGN METHODOLOGY Brief Description of the Instrument The circuit of incremental shaft encoder uses an opto-interrupt, device (OID) that combines light emitting diode and photo transistor in close proximity, the disc with 15 slots is attached to the shaft of the dc motor. Schmitt trigger consist of comparator UA741 is connected to the emitter of the photo transistor and output of the Schmitt trigger is also connected to the binary counters for digital display as shown in Fig.1 Analysis of results The results in Table 1, is plotted on the graph to establish the correlation between the frequency (Hz) and speed (rpm).

Slope = frequencyinChange

rpmfrequencyinChange )(

= 200500

8002000

−−

4rpm/Hz Component Design The design used an opto-interrupt device that combines light emitting diode and phototransistor in close proximity. An infrared light emitting diode emits light with a operating current of

1R

VVI dcc

d

−= (2)

Where Id and Vd are diode current and diode drop respectively (Robert & Louis, 1982). The light from the Infrared light emitting diode passes through the slots and incident on the photo sensor base that operates the phototransistor with a reference voltage of

ccref VRR

RV

43

4

+= (3)

Slot ω

1sb msb

Schmitt trigger

OID

Motor

Shaft Disc

23

Danladi A and Nathan C: Continental J. Applied Sciences 3: 21 - 29, 2008

0

500

1000

1500

2000

2500

3000

0 100 200 300 400 500 600 700

Frequency (Hz)

Sp

eed

(rp

m)

Fig.2: Relationship between Angular Speed (rpm) and Frequency (Hz)

24

Danladi A and Nathan C: Continental J. Applied Sciences 3: 21 - 29, 2008 Table1: Cost Analysis The complete list of the components used in the design of the model of the incremental shaft encoder are enumerated below; Component Quantity Unit price (N) Total (N) Transformer 240/220V 1 400 400 Diode IN4001 8 15 120 555 timer 1 60 60 UA741 comparator 1 60 60 Counter (4510) 4 150 600 Decoder (4511) 4 150 600 Display 4 150 600 IC Socket (16 pins) 10 25 250 D flip-flop 1 100 100 Quard NAND Schmitt trigger 1 100 100 IC socket (8 pins) 2 20 40 Connecting wires - 100 100 IC voltage regulator 2 50 100 dc Motor 1 200 200 LED 4 10 40 IR LED 1 120 120 Photo transistor 1 150 150 Zener diode (5V) 1 10 10 Capacitor 220µF, 50V 1 70 70 Total - - 3,700 And input voltage of

ccin VRR

RV

42

2

+= (4)

Where Vref and Vin are the reference and input voltage respectively (Paul & Windfield, 2001) as shown in Fig.2. These voltages make the photo sensor to conducts offers low resistance/low voltage at the non inverting terminals of the comparator, the comparator then compares the reference voltage and the input voltage to generate a LOW pulse; when the light does not strikes the photo sensor base, the photo sensor does not conducts and offers high resistance/high voltage at the non-inverting terminal of the comparator then a HIGH pulse is generated. The trains of pulse generated at the output of the comparator depends on the frequency/speed in rpm of the shaft. A 555 timer used in this design is configured as astable multi-vibrator that generate a gating pulse of constant time duration (∆T) of 4s which serves as the means of opening and closing of the logic gate (AND gate) for the trains of the pulse coming from the output of the comparator to be counted by the counter. The period when the gating pulse is HIGH is given by (Green, 2003) T1=ln2(R5+R6)C1 (5) While the period when the gating pulse is LOW is also given by T2=ln2R6C1 (6) Then the total time required for trains of pulse to be counted is given by (Ronald & Neal, 2001). T=T1+T2 (7)

25

Danladi A and Nathan C: Continental J. Applied Sciences 3: 21 - 29, 2008 Table 2: Result of performance and frequency analysis after test Test Speed (rpm) Frequency (Hz)

1 250 63

2 500 125

3 750 188

4 1000 250

5 1250 313

6 1500 378

7 1750 478

8 2000 500

9 2250 563

10 2500 625

And frequency of the oscillation is also determined using (Millman, 1998).

Tf

11 = (8)

The frequency required to the reset counting process is given by (Jacob, 1986).

372 2

1

CRf

π= (9)

Design Procedures The design takes the following steps Disc Design Consider the disc in Fig.3; the slots are drilled at regular interval of 240

Slot

disc

Fig.3: Plastic disc

26

Danladi A and Nathan C: Continental J. Applied Sciences 3: 21 - 29, 2008 Let X be the speed in rpm. The number of pulse generated per minute depends on the number of slots in the disc. Since there are 15 slots in the disc we have 15X pulse per minute, one minutes is equal to 60 seconds; Therefore 15X pulses per 60s

460

15 XX =

This means that a clock pulse will come in every 4s Transmitter circuit (IR LED) Design Fig.4: Transmitter circuit of IR LED Assume that Id =20mA and Vd =2V R1 was obtained from equation (2) as R1=333Ω, for practical purpose the value of R1 was chosen from the data as 330Ω as the nearest value. Receiver and comparator circuit Design Fig.5 Receiver & comparator circuit R3 was set to 100Ω and R4 was chosen from data book as 1kΩ, the reference voltage was determined as 11V from Equation (3). For the value of R2 the reference voltage was made approximately closed to the input voltage as 11.8V (Vin≈Vcc) and R2 was obtained from Equation (4) as 2240Ω but for practical convenience R2 was chosen from data book as 2.2kΩ as the nearest value.

IRLED

R1

Vcc

Vcc=12V

- +

Vcc=12V

R3

Vref

R4

Photo Transistor

IR light

R2

V in

27

Danladi A and Nathan C: Continental J. Applied Sciences 3: 21 - 29, 2008 Time base (555 timer) Design From the disc design T1=4s Fig. 6: Time base circuit From Equation (5); when the gating is HIGH, R5 was determined as 20,028Ω with R6 and C1 chosen from data book as 1kΩ and 220µf respectively. R5 was also chosen as 20kΩ from data as the next available value. The period when the gating pulse is LOW was determined using Equation (6) as 0.15s while the total time when the gating period is HIGH or LOW was determined from Equation (7) as 4.15s, then the frequency of oscillation was also obtained from Equation (8) as 0.24Hz. Control logic circuit (Differentiator) Design Fig.7: Control logic circuit The frequency of the oscillation is equal to the frequency required to reset the counting process, this was computed as 0.24Hz, and the value of C3 was obtained as 33.02 x 10-9F, but C3 was chosen from the data as 33µF as the next preferred value Power Supply Unit The power supply used in this design incorporate two integrated circuits regulator, which have fixed voltage regulators producing +5V and +12V. The transformer is a 240V ac input and 24V, 12V output. The rectifier is a full wave bridge, which makes use of four rectifier diodes of required rating. The output of the ac voltage is filtered by 50V, 220µF capacitor and fall to the input of the regulator. The 12V regulator

555

∆T Gating pulse

R5

R6

C2

C1

4 8

1 5

7

6

2

Vcc

3

C3

R7

28

Danladi A and Nathan C: Continental J. Applied Sciences 3: 21 - 29, 2008 makes use of the KA7812 regulator via 50V, 10µF smoothing capacitor, the 12V is further passed through a KA7805 regulator to produce +5V regulated output and 1µF capacitor are used to removed any ripple in the design from the regulator that could cause error in the ICs used. Construction Details The construction of the circuit did not commence until the circuit was tested on breadboards and found to be working well. The circuit was tested using three breadboards, the counter-decoder units was mounted on the breadboard, a 555 timer was configured as an oscillator and used to check the working of the counters and the decoders. The comparator stage was also connected on the breadboard and tested for proper functioning; a little adjustment was made on the variable resistor before the circuit could respond to the infrared rays from the infrared LED, the time base differentiator and bubble resolver stage and AND gate that is the control units was also connected and checked for proper functioning. After this preliminary test, all were transferred to the Vero board. The power supply circuit, the control unit, the time base, the comparator circuit were all housed in one Vero board. During the construction of this stage LED’s were used to monitor the output of the time base, the comparator’s output and also of the power stage. The seven segment displays were all mounted on one Vero board. The disc used on the motor shaft was cut to shape with a diameter of 80mm, the 15 slots were then marked out with compass and protractor, the angular spacing of the slots is 240C. The holes in the disc were drilled with the aid of a 4mm drill bit using the drilling machine in the machine laboratory. Cost Estimate The designed developed incremental shaft encoder cost (N3, 700.00) which is three times less than the market price of the imported price. If accepted in Nigerian industries, it would tremendously solve the problems of importation. Performance Testing and Results The time base unit was calibrated to give precisely a gating duration of 4 seconds. The signal generator in the laboratory was set to a frequency of 250Hz(square wave) and the gating pulse duration was adjusted with the help of the adjustable resistor in the time base unit until it gave a reading of 1000rpm. To further confirm accuracy of the calibration, the frequency was increase to 500Hz and the incremental shaft encoder gave a reading of 2000rpm. To ascertain the relationship between frequency and speed, test of speed verse frequency was carried out, the result is shown in Table 1. Fig.2 described fully the relationship between the angular seed (rpm) and frequency in (Hz) as the speed increase the frequency also increases. DISCUSSION The circuit designed as earlier stated is a prototype of an industrial incremental shaft encoder, which be employed in the field of electrical and electronic instrumentation in Nigeria industries. The imported industrial incremental shaft encoder are very expensive, if this designed is developed and used it will cost many time less than the ones imported. Incremental shaft encoder is hardly used in Nigeria industries except in a vital unit of operations where they become indispensable. The design used throughout the CMDS version of integrated circuits because mixing it up with other family will definitely requires an interface which would be another design problem to tackle. The TTL, ECL logic family were avoided because of incompatibility with the CMDs circuitry. From test results, this circuit is functional, cheap and simple to maintain.

29

Danladi A and Nathan C: Continental J. Applied Sciences 3: 21 - 29, 2008 CONCLUSION Digital instrument like an incremental shaft encoder used digital method and circuitry with numerical readouts. Some of the transducers commonly encountered in the modern electronic instrumentation gives output signal suitable for direct processing. The digital methods have been popularized in areas of data acquisition, processing and display of availability of inexpensive digital integrated circuits, microprocessor and digital counters. The aim and objectives of this work has been practically achieved using experimental techniques in electronic engineering, if this design would be accepted in Nigeria in no distant time, an incremental shaft encoder will be as common as any other digital instrument. But the performance of the circuit could be improved by the various techniques such as: Incorporate programmable speed window to detect and indicate over or under speed of the motor or generator shaft. Replace UA741 comparator with a very fast response device such as NE527 at several thousand volts per microsecond. Increase the number of slots in the disc to improve the sensitivity of the circuit. REFERENCES Efedua, J.E. (2002): Principles of instrumentation, Leo Prints Benin City, Nigeria Green, D.C. (2003): Digital Electronic, Pearson Education; New York, USA. Jacob, M.(1986): Microelectronics, Digital and analogue circuits and system. McGraw-Hill ; New York, USA. John, F.W.(2002): Digital design principles and practice John Wiley; London Millman, H. (1998): Integrated electronics analogue and digital circuits and systems. McGraw-Hill; USA Moris, M.M.(2001): Digital design, John Willey and Sons; USA. Paul, H. and Winfield (2001): The Arts of electronics press. Syndicate New York, USA. Robert, B and Louis, N. (1982). Electronic devices and circuits theory, Prentice Hall Inc; New Delhi Ronald, J.T and Neal, S.W. (2001). Digital system principles and application, Pearson Education, Pte, Ltd; USA Thomas, L. F(2001). Digital fundamental, 482, F.I.E. Patparganj; Singapore Received for Publication: 27/02/2008 Accepted for Publication: 05/03/2008 Corresponding Author: Danladi A Department of Physics, Adamawa State University, Mubi, Adamawa State. Email: deshalangs3g@yahoo.com

30

Continental J. Engineering Sciences 3: 30 - 36, 2008 ©Wilolud Online Journals, 2008.

INFLUENCE OF RECYCLED CONCRETE AGGREGATE (RCA) ON COMPRESSIVE STRENGTH OF PLAIN CONCRETE

O.A.U UCHE CIVIL ENGINEERING DEPARTMENT, BAYERO UNIVERSITY, KANO

ABSTRACT This paper presents the findings of an investigation on the influence of recycled aggregate concrete (RCA) as a substitute for virgin coarse aggregate in the compressive strength of `plain concrete. Recycled aggregate concretes were produced together with virgin coarse aggregates and subjected to empirical tests which include grading, specific gravity, bulk density, water absorption, aggregate impact value (AIV) and aggregate crushing value (ACV) to ascertain their performances. Mix design was carried out for grade 30 concrete according to DoE (1975) and RCA percentages of 0, 25, 50, 75, and 100 were used in replacing the virgin aggregate proportion in the mix. The test results showed that the use of recycled concrete aggregate (RCA) reduces the compressive strength and this reduction increases with the increase in percentage of the RCA. Maximum decrement of about 33% in strength or about 67% of compressive strength development occurs when 100% of RCA was used as substitute to virgin coarse aggregate. It also reveals that about 25% of virgin coarse aggregate can be replaced with RCA in structural concrete work with out compromising the characteristic strength of the concrete. This result will not only eliminate the development of waste stockpiles of concrete as recycled material but also elicit the use of RCA in concrete work, thus providing environmentally friendly and economically viable solution as substitute for virgin aggregate as well as provide savings in the final cost of projects. KEY WORDS: Cement, Concrete, Virgin aggregates, Recycled concrete aggregates (RCA), compressive strength.

INTRODUCTION The need and importance of concrete in construction industry is ever increasing since its discovery. Lomborg (2007) reported that the use of concrete is more than any other man made material on the planet. As about 2005, six billion cubic meters of concrete are made each year with countries like China currently consuming about 40% of world cement production, (Wikipedia, (2007). Most of the times, facilities constructed using concrete materials need to be repaired or replaced with passing time either because their end of service life is reached or the original design no longer satisfy the needs due to the growth in population or traffic or even an error in construction. These activities have always led to construction, demolition and excavation waste. The waste materials does not only constitute environmental problem but also put pressure on the available constituent materials used in concrete production- like the aggregate. The facts have remained how do we satisfy the growing demand for construction aggregates and, secondly how do we take care of the ever increasing amount of construction waste. FHWA (2004), report shows that two billion tonnes of aggregate are produced each year in the United States and production is expected to increase to more than 2.5 billion tonnes per year by the year 2020. This has raised concerns about the availability of natural aggregates and where they will find new aggregate sources.

31

O.A.U UCHE: Continental J. Engineering Sciences 3: 31 - 37, 2008 Generally, millions of aggregate tonnes are produced each year in developing countries and is expected to increase tremendously in the future as more concrete material is used. This has raised concerns about the availability of natural aggregates and where to find new aggregate sources. Table 1: Grading Table for Fine Aggregate (sharp Sand)

Sieve Numbers

(BS)

Opening Size of Sieve

(mm)

Cumulative Fraction Passing

(%)

3/8’’ 10.00 99.60

3/16’’ 5.00 99.15

5 3.35 96.03

7 2.36 90.07

14 1.18 80.52

25 0.600 68.02

36 0.425 60.94

52 0.300 51.90

72 0.212 45.06

100 0.150 44.12

200 0.075 38.93

On the other hand, the report also confirmed that the construction waste produced from building demolition alone in US is estimated to be 123 million tonnes per year. Table 2: Grading Table for Virgin and Recycled Coarse Aggregates

Sieve Numbers

(BS)

Opening Size of

Sieve

(mm)

Cumulative Fraction

Passing (%)

(Virgin Aggregates)

Cumulative Fraction

Passing (%)

(RCA) 2” 50 100 100

11/2” 37.5 100 100 1” 20 76.6 73.6 - 14 18.1 15.20

3/8” 10 6.8 3.65 - 6.3 3.05 1.60 4 5 2.8 1.40 5 3.35 0.3 1.25 8 2 0.17 1.20

Pan Pan 0.0 0.0 Historically, the most common method of managing this material has been through disposal in landfills. As cost, environmental regulations and land use policies for landfills become more restrictive, the need to seek for alternative uses of the waste material increases. This situation has led State Agencies and the aggregate industry in the US to begin recycling concrete debris as an alternative aggregate. The report further said that commercial construction industry has been leading the reuse of this debris, but with the State

32

O.A.U UCHE: Continental J. Engineering Sciences 3: 31 - 37, 2008 Transportation Agencies (STA) recognizing the engineering, economical and environmental benefits that can be achieved for using recycled concrete aggregates (RCA), prompting its use for highway work to be on the increase. Also several studies by Wilburn, and Goonan (1998); Kerkhoff and Siebel (2001); Sagoe-Crentsil,(2001); Katz, (2002); Olorunsogo and Padayachee(2002) and Salem, et al (2003), show that RCA Table 3: Aggregates Result of Mechanical Properties. is a valuable resource, and by proper engineering, it can be used for pavement aggregate base, and other miscellaneous concrete work. They inferred that the material is too valuable to be wasted, and landfill. The report identified that some of the best aggregates used for highway, bridge, and building construction are already in use in most of the highways and bridges, and effective recycling is a means to re-use these materials. Despite the obvious benefits derivable from the use of recycled concrete, as is practiced in developed and developing countries, Nigerian construction industry is yet to adopt the practice of RCA as aggregate substitute in structural grade concrete, although in some cases, they use has been established for roadwork as sub-base or base, backfills and/or flooring. Considering the ever increasing construction work coupled with the antecedent demolition/failure of structures in major cities of the country resulting in large tonnes of concrete debris an investigation on the effect of RCA on structural concrete becomes necessary. This paper reports the findings of an investigation on the suitability of use of recycled concrete aggregates (RCA) as substitute to virgin aggregates in structural concrete work. Aggregates constitute about 75% by weight of concrete and it is considered to not only influence the volume stability, strength and durability of the composite material but also makes it more economical in value (Neville, 2003). JUSTIFICATION: The use of recycled concrete aggregates (RCA) in new construction work will eliminate the development of waste stockpiles of concrete as recycled material can be used within the same metropolitan area; this can lead to a decrease in energy consumption from hauling and producing aggregate, and can help improve air quality through reduced transportation source emissions. Also the supply of virgin aggregates in many areas in the country is becoming limited; the use of recycled concrete aggregates will serve as an environmentally friendly and economically viable solution as substitution of RCA for virgin aggregate can provide savings in the final cost of projects. The reuse of concrete demolition will eventually reduce unsightly stockpiles of concrete rubble, animal infestation of stockpiles, and an overall environmental improvement.

Property Virgin Aggregates (Crushed Rock)

Recycled Concrete Aggregates (RCA)

Specific Gravity 2.70 2.47 Aggregate Impact

Value(AIV) %

23

23 Aggregate Crushing

Value(ACV) %

20

25 Bulk Density

(Kg/m3) 1641.10 1502.20

Water Absorption (%)

0.38 4.04

33

O.A.U UCHE: Continental J. Engineering Sciences 3: 31 - 37, 2008 MATERIALS AND METHODS: Materials:

1. Cement: The cement used for the research is the ordinary Portland cement manufactured by Ashaka cement company Plc. Care was taken to ensure that it was of recent supply and free from adulteration.

2. Aggregates: The fine aggregates used are clean sharp sand, graded to be of zone 2 and the virgin

coarse aggregates are crushed granite of maximum size of 20mm, both obtained from supplies for laboratory work in Civil Engineering department of Bayero University Kano.

3. Recycled Concrete Aggregates(RCA):

The recycled concrete aggregates were obtained from a demolished building structure located along old Bayero University Road, Kano. The old concrete lumps were broken into smaller pieces on the site. This was further broken down to pieces manually using sledge hammer and the steel reinforcements, dowels and tie bars removed after which sieving was carried out using 5mm BS sieve to remove the unwanted recycled fines. Further sieving using 20mm sieve was done to ensure the maximum aggregate size of 20mm.

4 Water: The water use for the research is portable water fit for drinking Table 4: Compressive Strength Test Result on RCA Concrete Specimens

Methods: Both the virgin and recycled aggregates were subjected to mechanical tests in accordance to British Standards: BS 812 (1975); BS 882 (1992).These are aggregate Impact value (AIV), aggregate crushing value (ACV), specific gravity, water absorption and bulk density as well as grading test. Mix design was carried out for concrete grade 30 using the procedure for the design of normal concrete mixes (DoE, 1975). The virgin coarse aggregates proportion of the mix design is partially replaced with RCA of 0%, 25%, 50%, 75% and 100% by weight respectively. The 0% replacement with RCA served as control test. The constituent materials were batched by weight, mixed thoroughly, and cast into 150mm x 150mm x 150mm cube moulds and compacted mechanically to the required density. A total of Forty five (45) concrete cubes were cast. Three (3) cubes each were tested for compressive strength at 3, 7, and 28 days of curing in clean water and 24 hours of air drying in the laboratory and at various percentages of replacement of virgin aggregates with RCA. The compression test was done in accordance to BS 1881(1983), using Avery Denison universal testing machine with maximum capacity 2000KN. The machine applied load axially on the cube specimen at a constant rate until a maximum load, which correspond to the ultimate compressive load is reached at failure point.

RCA Replacement

(%)

Average Compressive Strength N/mm2 3 days Change in

Strength %

7days Change in Strength %

28days Change in Strength. %

0 25.20 - 30.10 - 40.10 - 25 24.90 -1.19 29.48 -02.06 38.83 -03.17 50 24.59 -2.42 28.74 -04.52 37.50 -06.48 75 22.96 -8.89 25.93 -13.85 34.07 -15.04 100 18.82 -25.30 25.32 -15.88 27.11 -32.29

34

O.A.U UCHE: Continental J. Engineering Sciences 3: 31 - 37, 2008

Fig.1: Compressive Strength of RCA Plain Concrete

0

5

10

15

20

25

30

35

40

45

3 7 28

AGE(Days)

CO

MP

RE

SS

IVE

ST

RE

NG

TH

(N

/mm

2)

0% RCA

25% RCA

50% RCA

75% RCA

100% RCA

FIG.2 :PERCENTAGE REDUCTION IN COMPRESSIVE STRENGTH WITH INCREASE IN RCA

-35

-30

-25

-20

-15

-10

-5

0

0 25 50 75 100

RCA REPLACEMENT OF VIRGIN AGGREGATE (%)

CO

MPR

ESS

IVE

STR

EN

GTH

(N

/mm

2)

3 Days

7 Days

28 Days

PRESENTATION AND DISCUSSIONS OF RESULTS The physical and mechanical properties tests on the virgin and recycled concrete aggregates (RCA) are as in tables 1, 2, 3. Table1 revealed that the natural fine aggregates falls within zone 2 of BS 882 grading limits. This indicates that the sharp sand is of good grade for structural plain concrete. The grading table for virgin coarse aggregates and recycled concrete aggregates (RCA) in table 2 show that both aggregates contains similar size proportions with the RCA having more fines than the virgin aggregates. This indicates possibility of greater water absorption when RCA are implored in concrete making. Table 3 shows that the virgin coarse aggregate has Specific gravity, Aggregate impact value (AIV), Aggregate crushing value(ACV) and Bulk density of 2.7, 23%, 20% and 1641.10Kg/m3 respectively while the RCA has its Specific gravity, AIV, ACV and Bulk density as 2.47, 23%, 25% and 1502.20Kg/m3 respectively. These values are clearly within the BS 812 limits for aggregates needed for both highway and structural concrete work. The result of workability test conducted with various percentages of RCA replacement of virgin aggregate in concrete specimen show that 0% RCA (control test) has slump of 28mm, while the slump values for

35

O.A.U UCHE: Continental J. Engineering Sciences 3: 31 - 37, 2008 25%, 50%, 75% and 100% RCA are 22mm, 18mm, 13mm and 11mm respectively. These values show that as the percentage of RCA replacement of virgin aggregates increases the slump values decreases. This may not be unconnected with proportion of fines in RCA as seen in table 2. Also the presence of residual cementatious materials on RCA increases its water absorption potentials, hence the decrease in workability. This is also confirmed by the water absorption test presented in table 3, which show that the virgin aggregates has 0.38% as compared to 4.04 % of the RCA concrete. The results of the compressive strength test presented in table 4, figures 1 and 2 show generally that the strength increases with age, which is expected. The 3, 7, 28 days average strength with 0 % RCA has the compressive strength of 25.20 N/mm2, 30.10 N/mm2 and 40.10 N/mm2 respectively. This increase tends to decrease as the percentages of the RCA in the concrete increases from 0 -100%. For instance, the compressive strength of specimens with 25 %, 50%, 75% and 100% RCA at 28 days age of curing are 38.83N/mm2, 37.50N/mm2, 34.07N/mm2 and 27.11N/mm2 respectively. The decreases when compared to the control test (0% RCA) showed a lower compressive strength at all ages of the concrete from 1.19% reduction at 3day-strength to 32.29% reduction at 28 day- strength as shown in figure 2. The reduction in strength reached the peak value at 100% RCA replacement of virgin coarse aggregate as the 28-day compressive strength reduced to about 77% of the normal virgin aggregate concrete. The reduction in strength also confirmed the earlier view by some researchers that compressive strength of RCA concrete is about two-third of the virgin aggregate concrete, Frandistous-Yannas (1977). The decrement can be attributed to weaker interface between the recycled concrete aggregates (RCA) which is surrounded by residual cementatious matrix of cement and sand before the new concrete mix. Other possible reasons for reduction in compressive strength include the flakiness and angularity of the RCA which makes compaction limited and hence reduced bulk density. It is also noticeable that at 75% or less RCA replacement that the concrete compressive strength is well above the designed characteristic strength of grade 30 concrete hence it can be implored for structural grade concrete work. CONCLUSION: 1. The use of recycled concrete aggregates (RCA) as alternative to natural or virgin aggregate in structural concrete reduces the strength development of the concrete. 2. A combination of RCA with natural virgin coarse aggregates in cases where high compressive strength and durability is not a priority with percentage replacement of 50% or less RCA is suitable for structural work. 3. More water is needed to maintain suitable workability of fresh concrete when RCA is used in concrete work. Further research work is recommended in areas of flexural strength, drying shrinkage, creep and age effect of the RCA in concrete work REFERENCES: British Standard Institution, BS 812: Part 2 (1975): Method of Testing of Aggregates, BSI, London.

British Standard Institution, BS 882 (1992): Method of Testing Aggregates from Natural sources for concrete, BSI, London. British Standard Institution, BS 1881: Part 116 (1983): Method of Testing Concrete for Strength, BSI, London. Department of Environment, DoE(1975): Design of Normal Concrete Mixes, HMSO, London Pp6-25.

36

O.A.U UCHE: Continental J. Engineering Sciences 3: 31 - 37, 2008 Frandistou-Yannas, S (1977): Tests on Waste Concrete as aggregates for new concrete. Journal of American Concrete Institute, 74(8) pp373-376. Federal Highway Administration, FHWA (2004): State of the Practice National Review “Transportation Applications of Recycled Concrete Aggregate”, U.S. Department of Transportation, Federal Highway Administration. Katz, A. (2002): “Properties of Concrete Made with Recycled Aggregate from Partially Hydrated Old Concrete”. Cement and Concrete Research 33 (2003) pages 703-711. Elsevier Science Ltd. Kerkhoff, B., and Siebel, E.(2001) Properties of Concrete with Recycled Aggregates (Part 1),“ Beton, Publishers, pages 47-50. Lomborg, B. (2007): Measuring the Real State of the World, the Skeptical Environmentalist, p138. Neville, A.M (2003): ‘’Properties of Concrete”, 4th edition, London Scientific and Technical limited, England.Pp119-136 Olorunsogo, F. and Padayachee, N. (2002): “Performance of Recycled Aggregate Concrete Monitored by Durability Index”. Cement and Concrete Research 32 pages 179-185. Elsevier Science Ltd. Sagoe-Crentsil, K., Brown, T., and Taylor, A (2001). “Performance of Concrete Made with Commercially Produced Coarse Recycled Concrete Aggregate”. Cement and Concrete Research 31 (2001) pages 707-712. Elsevier Science Ltd. Salem, R., Burdette, E., and Jackson, M. (2003) “Resistance to Freezing and Thawing of Recycled Aggregate Concrete”. ACI Material Journal, V.100, No.3, May-June. Wilburn, D. and Goonan, T. (1998): U.S. Geological Survey. Aggregates from Natural and Recycled Sources, Economic Assessments for Construction Application – A Material Flow Analysis: Circular 1176. http://www.wikipedia.org. (2007): Concrete Received for Publication: 21/02/08 Accepted for Publication: 18/04/08

37

Continental J. Engineering Sciences 3: 37 - 41, 2008 ©Wilolud Online Journals, 2008.

DESIGN, CONSTRUCTION AND IMPLEMENTATION OF A 3 METER SATELLITE DISH

ANTENNA (PARABOLOID REFLECTORS)

Danladi A1 and Jerome G2.

1Department of Physics and 2Department of Mathematical Sciences, Adamawa State University Mubi.

ABSTRACT, The objective of this work is to design, construct and implement a 3m diameter paraboloid reflector with a frequency allocation of 3GHZ and above. The design was achieved with the help of wire mesh, aluminum span, mild steel, aluminum foil and glass fiber. The designed model was able to pick up signal from Arabian Satellite CNN, Adamawa Broadcasting television station and other channels with the help of low noise amplification block (LNB) KEYWORDS: Signal, frequency allocation, background noise, frequency spectrum and efficient transmission.

INTRODUCTION Antennas are fundamental components of radio systems and use free space as the carrying medium. They are used to interface the transmitter or receiver to free space, antenna have quite number of important parameters, and those of most interest include the gain, radiation pattern, polarization, beamwidth, bandwidth, directivity, voltage standing wave ratio (VSWR), efficiency and impedance matching (Haykin, 2001 & Website, 2002a). In some years ago, developments in broadcast technology have caused demand for more frequency allocation since the present frequency in used is inadequate for efficient transmission. (Green, 2000). Also there is the need to use frequencies where background noise is less effective that is why use of frequency of radio spectrum of above 1-2GHZ is being made (Saunders, 1999) At these frequencies, the use of parabolic reflector type antenna is a must for transmission and reception, therefore only practical form of antenna for receiving these frequency is the parabolic dish reflector antenna. This now prompted the emergency of this design. DESIGN METHODOLOGY Brief Description of the parabolic reflectors The dish is 3m diameter wide of depth 0.6m, the LNB is attached to the feed horn which has provision for the supply of power through a radio frequency (RF) cable (coxial cable) by the R.F connector. COMPONENT DESIGN The basic parabolic antenna generally has a define formula given by

d

DF

16

2

=

(1) And general equation of a parabola is also given by

Frk 42 = (2) Combining Equations (1) and (2), we have

rd

Dk

4

22 =

(3)

38

Danladi A and Jerome G: Continental J. Engineering Sciences 3: 37 - 41, 2008 Table 1: Cost Estimate for the manufacture

Items Quantity Price (N)

Wire mesh 2x1m N10,000 Aluminum span 1span N11,000 Mild steel 1m N 4,200 Aluminum foil 2m N340 Fiber glass N2,000 Pipes 2/4” x 1 and ¾”x3 N6000 Total N33,540

Table 2: Design Results r 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 k 1.99 2.81 3.45 3.98 4.45 4.87 5.27 5.63 5.97 6.29 Antenna radiation pattern Measured antenna Fig1: Parabolic antenna with radiation pattern Where F is the focal focus of the dish measured in meters; D is the diameter of the dish in meters; d is the depth of the dish and r,k are chosen variable for the parabolic antenna design. (Bajpai et al, 1981and Erwin, 1989) If D = 3m, the ratio of F/D is equal to 0.33, from equation (3) d becomes 0.6m. Assume r = 1 to 10 the corresponding values of k were determined as shown in Table 2.

.

.

OOOO

39

Danladi A and Jerome G: Continental J. Engineering Sciences 3: 37 - 41, 2008

design values r vs k

012

34567

89

10

0 5 10

k

r

Fig 2: Interpretation of the chosen variable r and k. Antennas have some important parameters parameters as stated before, this work took into consideration all parameters. Voltage Standing Wave Ratio (VSWR) Determination The VSWR used in this design define the radio of voltage standing at maximum wave per voltage standing at minimum wave given by

VSWR = //1

//1

ρρ

−+

and

(4) oL

oL

ZZ

ZZ

+−

=ρ

(5) Whereρ is the reflection coefficient, Zo and ZL are the characteristics impedance and load impedances

respectively (Pozar, 1997). In this design VSWR = 1, ρ = o for proper matching and maximum power

transfer. Efficiency Determination Efficiency (β ) is determine by the total radiated power per total input power given by

Pi

Pr=β

(6) Where Pr is the total power radiated and Pl is the total input power (Website, 2002b).

=β 67%. In this design, but in real situation 75% is very good although 50% is acceptable in most

antenna design. (Website, 2002a)

40

Danladi A and Jerome G: Continental J. Engineering Sciences 3: 37 - 41, 2008 Antenna gain/3D pattern Determination Antenna gain is directly related to frequency and antenna capture area. The number of wavelength in its signal – capture area determines the gain of an parabolic antenna given by

G = 7.5 + 20 log (f) + 20 log (D) (7)

Where f is the frequency and G is the antenna gain (Frank, 2001) in this design the antenna gain of the parabolic antenna was determined as G = 30.66dBi because of the wideness of the dish, although in smaller diameter antenna the gain may be between 2dBi – 3dBi (Website, 2002b) Directivity Determination This is similar to gain, but heat losses (i.e. the affectivity) are disregarded. We will then get a pattern as a dotted line shown in Fig 1; the value of directivity is obtained using

a

cD =

(8) Where c represent total power and a represents average power which can also be written as (Website, 2002a)

avp

PD =

(9) Beamwidth Determination This is the directiveness of a directional antenna used in this design as the angle between half – power points either side of the main lobe of radiation. -3dB was obtained as the angle between two half powers. (Website, 2002a). Bandwidth Determination Is the region where there is no losses given by

B = ii LH ff −

(10)

Where iHf is the highest frequency attended while

iLf is the losses of the amplifier at that frequency

(Edeko,2004). The larger the bandwidth the higher the signal transmitted. Impedence Matching An ideal situation antenna has an impedence of 50Ω (Ludwig 1997) all the way from the transceiver to the antenna. So to get the best possible matching impendence between transceiver, transmission line and antenna as used is this design, since the ideal condition do not exist in reality, this design used impedence matching in the antenna interface, often must be compensated by the means of matching network, i.e. a net build with inductive or capacitive components. The VSWR was optimized by choosing the proper layout and components values for the matching net and maximum potential of the antenna shown in Fig 1. CONSTRUCTION DETAILS All measurements were done accurately in engineering Laboratory federal polytechnic Mubi, before the materials were assembled to form a parabolic dish of 3m wide and 0.6m depth. Little adjustment was made to determine the approximate principle focus where most of the signals concentrate that is both wanted and unwanted signals before amplification by LNB, for transmission in to the reception. The parabolic shape was cut – out to specification from the cardboard paper and then transferred to the metal pipe. Several of these metals pipes were joined together by welding to the parabolic frame. The Ohmic resistance of joints was given serious attention by ensuring professional welding

41

Danladi A and Jerome G: Continental J. Engineering Sciences 3: 37 - 41, 2008 COST ESTIMATE One of the major aims of this paper is to show how a 3m diameter parabolic antenna can be designed and constructed using locally available materials at a cheaper price compared to the current price in market today. A typical 3m diameter antenna will cost about N50, 000.00 in the market depending on the manufactures product name for example DSTV, STRONG and so on. The designed and the constructed parabolic antenna cost far less than the imported parabolic antenna as shown in Table 1. PERFORMANCE TEST AND RESULTS The testing of the disc was done when the antenna and accessories including the feed horn, LNB receiver and television/monitor were placed in order. The LNB was attached to the feed horn which has provision for the supply of power through a radio frequency cable by RF connector, this passed directly to a TV set for monitoring the signal. The output of the receiver was monitored, the dish was pointed to the exact sport of orbital satellite we wished to get the signal, and Arabian satellite was trapped with clear reception and many others like CNN, ATV and so on. CONCLUSION A 3m parabolic antenna has been designed, constructed and implemented using engineering experimental technique locally reliable and readily available materials were used in the construction of the 3m parabolic antenna. The design ensures that the system delivers up to 3GHz and above. This designed antenna can be used in a very verse communication areas including global system for mobile communication (GSM) REFERENCES Bajpai A.C., Calus, I.M., Fairley, J.A, and Walker D. (1981): Mathematics for Engineers and Scientists, John Wiley and Sons. Great Britain Edeko, F.A (2004): Analogue communication and Advance electronics. University of Benin Master note Book, Unpublished. Erwin, K. (1989): Advance Engineering mathematics. John Wiley and Sons. United State of America. Frank, J.J. (2001): Fundamental of radio link Engineering, John Wiley and Sons. United State of America. Green, D.C. (2000); Radio communication, Longman. New York. Haykin, S. (2001): Radio communication. John Wiley. Canada. Ludwig, R.and Bretchko, P. (1997): Radio frequency design; Prentice Hall of India. New Delhi. Pazor, D.M. (1997): Microwave Engineering; John Wiley and Sons.United State of America. Saunder, S.R. (1999): Antenna and propagation for wireless communication system; Wiley and Sons. Canada. Website, (2002a): http://www.gsmworld.com/technolgy/fliq.htm Website, (2002b): http://www.gigaant.com/antenna basics Received for Publication: 27/02/2008 Accepted for Publication: 25/04/2008 Corresponding Author: Danladi A. Department of physics, Adamawa State University Mubi. Email: deshalangs3g@yahoo.com

42

Continental J. Engineering Sciences 3: 42 - 49, 2008 ©Wilolud Online Journals, 2008.

DESIGN AND THERMODYNAMIC SIMULATION OF A SOLAR ABSORPTION ICEMAKER

M. Umar1 and A. B. Aliyu2

1Mechanical Engineering Department, Kano University of Science and Technology, Wudil and 2Mechanical Engineering Department, Bayero University, Kano

ABSTRACT A solar absorption icemaker was designed. It is an intermittent system and uses Calcium Chloride and Ammonia as absorbent and refrigerant respectively. The single glazed collector/absorber/generator unit uses a plane glass sheet as the outer cover. Overall collector plate exposed area is 1.0m2. A thermodynamic simulation of the icemaker has been performed in order to investigate the effect that the generator temperature and collector efficiency have over the Coefficient of Performance (COP). The average solar coefficient of performance of the system is 0.78 It was found that for a constant efficiency at the solar collector, there is an optimum temperature to be used as the generator temperature. KEY WORDS: Solar energy, simulation, absorption, ammonia, calcium chloride, icemaker

NOMENCLATURE

( )−WQp Heat gain produced by occupants

( )−WQw Latent heat gain brought by moisture gain

( )−2mAi surface area of a part of building structure overall

( )−KmWU i2 heat transfer coefficient

( )−hrsTcool time of cooling per day

( )−mKWk j heat conductivity of the material of thj − layer according to air

−m mass flow rate

−h enthalpy

coefficient of performance −T temperature −η efficiency

−g acceleration due to gravity

−η Collector efficiency

−COP Coefficient of performance

INTRODUCTION The climatic profile, socio-economic development and energy supply infrastructures in Kano indicate a high demand for cooling applications and strongly suggest the use of solar and renewable energy powered systems. Cold storage of food products and medicines, especially immunization vaccines, are important application of solar refrigeration. Many agricultural products like fruits, vegetables, meat, fish etc., can be maintained in fresh conditions for significantly longer period of time if they are stored at low temperatures. At present in Kano large quantities of these products are lost annually due to poor storage facilities. This situation is even worse in the remote rural areas where these fresh food materials are produced. As a result sharp differences in food supplies

43

M. Umar and A. B. Aliyu: Continental J. Engineering Sciences 3: 42 - 49, 2008 exist between the harvest and off harvest periods. High market value agricultural products are usually abundant and cheap during the harvest season and expensive at other times. Solar refrigeration can assist to reverse this trend. Solar powered refrigeration has been very attractive during the last twenty years, since the availability of sunshine and the needs for refrigeration both reach maximum level in the same season. One of the most effective forms of solar refrigeration is the production of ice, as ice can accumulate much latent heat, thus the size of the icemaker can be made small (Sumathy,1999). Absorption refrigeration relies on the absorption of a refrigerant gas into an absorbent at low pressure and subsequent desorption by heating. Solar absorption icemaker consists of a solar collector, a condenser and an evaporator that is placed in a refrigeration box. The solar absorption cycle is similar to the mechanical vapour compression cycle in that it employs volatile refrigerant, which alternately under low pressure in the evaporator vapourizes by absorbing latent heat from the material being cooled and condenses under high pressure in the condenser by surrendering the latent heat to the condensing medium. DESIGN OF SYSTEM AND COMPONENTS Many absorbent/refrigerant combinations have been designed in the past, either experimentally or commercially. These include CaCl2/NH3, SrCl2/NH3, LiNO3/NH3, NaSCN/NH3, LiBr/H2O, glycol ether/R21, with the most popular being H2O/NH3. The absorbents, particularly in the first four above, are able to generate large quantities of refrigerant, such as HN3, at low temperatures of the order of 1000C, making it possible for low temperature heat sources, such as waste heat and solar thermal radiation, to be used. In reference (Iloeje, 1995) a comparison was made between CaCl2/NH3, SrCl2/NH3 and LiNo3/NH3, H2O/NH3, NaSCN/NH3 systems. Operating conditions were assumed to be 400C ambient temperature, 0.55-0.45 solar collector efficiency, 5 h generation, 12 h absorption, and a total radiant flux of 1040 W/m2. The tests shows the superiority of the solid absorbents over the liquid absorbents, with CaCl2 being slightly better (and cheaper) than SrCl2. 2.1 DESIGN PARAMETERS

Solar radiation 931w/m2 Ambient temperature (outside) 32oC Ambient (Room) temperature 28oC Condensing temperature 37oC Evaporating temperature -10oC Collector/generator temperature 100oC Final ice temperature -5oC Generation period 6hrs Absorption period 12hrs Evaporator water mass 4kg Refrigerant/absorbent pair Ammonia/calcium chloride

From reference data for Kano, the average daily solar radiation for the 12 months calendar year is 26.83 MJ/m2 (Musbahu,2008) Assuming that our design 6hr day solar radiation which is about 75% of the daily value is uniformly distributed through out the 6 hours period; hence 931W/m2 was estimated. Ammonia can evaporate at temperature below 0oC. In fact evaporating temperature of -12oC had been achieved for liquid absorbent systems (Farber, 1970). Consequently, an evaporating temperature of -10oC and evaporator water temperature of -5oC was considered reasonable for sizing the system. A passive evaporative condenser constructed for the system. A passive evaporative condenser constructed for the system (Neilson,1977) gave a temperature of

44

M. Umar and A. B. Aliyu: Continental J. Engineering Sciences 3: 42 - 49, 2008 6oC below ambient, under humid condition. Assuming a condenser temperature of 5oC above ambient, a condensing temperature of 37oC was estimated, assuming an ambient temperature of 32oC. Simulated absorption/generation test in (Iloeje, 1995) showed that 5h generation and 11h absorption were enough to produce 80% of maximum possible generation and absorption. 6hrs and 12h were therefore chosen for the generation and absorption periods for the system respectively. THERMODYNAMIC PROPERTIES ABSORPTION AND GENERATION PROCESSES OF Calcium chloride

The reaction of calcium chloride and ammonia are as given below: CaCl2 + 2NH3 CaCl2 . 2NH3 ± Q1 (at T1) CaCl2 . 2NH3 + 2NH3 CaCl2 . 4NH3 ± Q2 (at T2) CaCl2 . 4NH3 + 4NH3 CaCl2 . 8NH3 ± Q3 (at T3) The equilibrium reaction temperature – pressure curves (T – P curves) are given in figure (2) for equations i and ii and iii. At condensing temperature of 37oC, P3 = 13.5 bar, T3 = 90o C and T2 = 100oC at an evaporating temperature of –10oC, P3 = 3 bar, T3 = 53o C and T2 = 63oC. Reaction (i) occurs at temperatures beyond those possible in flat plate collectors. Thus, 8 moles of NH3 may be absorbed per mole of CaCl2, during initial charging, but only 6 moles will be available for refrigeration. We shall assume no heat and pressure losses in components and lines. In order to analyse the system, mass and energy balance is performed at each components

Fig. 1.0 Schematic Diagram of Calcium chloride – ammonia Refrigeration Cycle ENERGY BALANCE OF THE SYSTEM Component Calculation Energy (Watt)

Gain Losses

Evaporator Total cooling load as calculated 24.70 _ Condenser

−= 21

.

. hhmQ refc

_ 25.57

Generator

−= 41

.

hhmQ refg 0.871 _

Balance 25.57 25.57

45

M. Umar and A. B. Aliyu: Continental J. Engineering Sciences 3: 42 - 49, 2008 The schematic diagram of the absorption refrigerator assembly is as shown in Fig. 1.0. It consists of a combined collector/absorber/generator of collector plate actual area 1.25m2 and effective exposed collector area of 1m2. The collector plate was of galvanized corrugated sheets with 76mm corrugation pitch, and painted with black oil paint. There were two collector tubes, each of 59mm od x 54mm i.d. x 1000mm long galvanized steel pipe. The collector tubes were painted with black oil paint. The annular space between the inner and outer tubes was charged with 1.0 kg of absorber granules per tube, which occupied about 80% to 85% of the annular volume. The collector plate and tubes assembly was mounted on the rear plate insulation inside a galvanized steel box. Its glazing was a clear plane glass. The insulation consists of 50.8mm thick expanded polystyrene chips. The collector/absorber/generator component was inclined at the latitude of °05.12 (which is that of Kano),was supported at its base and raised 1m above the ground level on an angle iron support frame. In a low pressure system, such as the one designed, the condenser and the evaporator must necessarily be closed to each other and the collector. Thus, they are located directly under the collector/generator/absorber unit such that the refrigerant flows into them is by gravity. The condenser steel piping is 7.18m length of 21mm od x 18mm id coiled. It is of galvanized steel tube. The separate evaporator consisted of a spirally coiled 21mm od x 18mm id tube galvanized steel tube of total length 1.13m.The liquid receiver and the evaporator vessel placed inside separate box of inside dimensions 300mm wide x 300mm breadth x 300mm high x 50.8mm thick. The gap was filled with expanded polystyrene insulation. The box or the ice cabinet was made up of galvanized metal sheets as the out side wall, while aluminum sheets were used as the inner walls in order to reduce transmission and absorption of heat. The design was carried out in Kano, Nigeria using the locally available materials. Solar and other relevant data used during the design were also of Kano. Simulation Analysis Mathematical model Figure 1.0 illustrates the main components of the solid absorption icemaker. In order to analyse the system, mass and energy balances were performed at each component. For the current study, it is assumed that the refrigerant vapour is 100% ammonia. At the expansion,

..

3

.

2 refmmm ==(Total mass balance)

And

32 hh = (Energy balance)

At the evaporator, ..

43

.

refmmm ==

( ).

.

34 hhmQ refe −=

Or,

34

..

hh

Qm e

ref−

=

At the condenser,

2

.

1

.

mm = (Total mass balance)

46

M. Umar and A. B. Aliyu: Continental J. Engineering Sciences 3: 42 - 49, 2008

−= 21

.

. hhmQ refc

At the generator

1

.

4

.

mm = (Mass balance)

44

.

11

..

hmhmQg −−=

−= 41

.

hhmQ refg

The COPof the absorption system is given by

g

e

Q

QCOP =

Computational model In order to analyze how the system react to different operating conditions, its necessary to simulate the variables that effect its performance, with the intention of obtaining the maximum COP out of the system. The operating conditions choose were: Tg = 70 – 140°C Tc = 37°C Ta = 32°C Te = -10°C Refrigerant mass flow mref = 0.000022746kg/s From Antonio, (2006) the liquid and vapour enthalpies of the refrigerant NH3 can be calculated from equations 1 and 2 respectively.

( ) ( )∑=

−=3

0

15.27i

iil TbTh

1

( ) ( )∑=

−=3

0

15.27i

iiv TcTh

2 The coefficients for equations 1 & 2 are presented in the table 2.0 below Table 2.0 coefficients for equations 1 – 2 (Antonio, 2006)

I ib ic

0 1.99E+02 1.46E+03 1 4.46E+00 1.28E+00 2 6.28E-03 -0.011501 3 1.46E-04 -0.00021523 4 -1.5262E-06 1.91E-06 5 -1.8069E-08 2.56E-08 6 1.91E-10 -2.5964E-10

47

M. Umar and A. B. Aliyu: Continental J. Engineering Sciences 3: 42 - 49, 2008 RESULTS AND DISCUSSIONS The operating boundaries of the system were examined by conducting simulations for various values of generator temperature, Tg , the operating ranges were 70°C < Tg < 140°C. The results were showed in Fig. 2.0 represents the COP Vs generator temperature for 100% efficiencies at the collector for a fixed evaporator temperature and condenser temperature. It shows that the COP increases as the generator temperature increases and the COP approaches uniformity as the generator temperature continue to increase. This may be explained by the fact that all the absorbed ammonia was separated from the calcium chloride and thus no more refrigerant flow to the condenser.

0.780

0.790

0.800

0.810

0.820

0.830

0.840

0.850

70.00 80.00 90.00 100.00 110.00 120.00 130.00 140.00

Generator Temperature(deg)

CO

P

COP

Fig. 2.0 COP variation as a function of generator temperature for 100% efficiency at the Collector

0.784

0.785

0.786

0.787

0.788

0.789

0.79

0.791

0.792

70.0 80.0 90.0 100.0 110.0 120.0 130.0 140.0

Generator Temperares(deg)

CO

P

COP 2

Fig. 3.0 COP variation as a function of the generator temperature for 75% collector efficiency

48

M. Umar and A. B. Aliyu: Continental J. Engineering Sciences 3: 42 - 49, 2008

0.784

0.785

0.786

0.787

0.788

0.789

0.79

0.791

0.792

0.793

0.794

70.0 80.0 90.0 100.0 110.0 120.0 130.0 140.0

Generator Temperatures(deg)

CO

PCOP 3

Fig. 4.0 COP variation as a function of the generator temperature for 50% collector efficiency

0.78000000

0.79000000

0.80000000

0.81000000

0.82000000

0.83000000

0.84000000

0.85000000

70.00 80.00 90.00 100.00 110.00 120.00 130.00 140.00

Generator Temperatures(deg)

CO

P

COP1

COP2

COP3

Fig. 5.0 COP variations as a function of the generator temperature for different values of collector efficiency The system COP for 75% efficiency at the solar collector for fixed evaporator temperature and condenser temperature is depicted in fig. 3.0. The system COP decreases as the generator temperature increases. It reaches minimum and then increases progressively as the generator temperature continues to increase. This may be explained by the fact that the generator temperatures corresponding the decreased COPs are below desorption temperature for the solid absorption refrigeration cycle, as such it is at the absorption phase of ammonia gas by the absorbent. Fig. 4.0 shows that the COP decreases as the generator temperature increases for a greater portion of the chart and then later starts to increase. This may be explained by the same manner above. The increase in COP means that more heat was absorbed in the evaporator. In other words, full amount of refrigerant is absorbed during absorption. The generator temperature effects over the system COP for different efficiencies at the solar collector is shown in fig. 5.0. The chart can be described as follows; For a given generator temperature; the system COP increases as the efficiency augment.

49

M. Umar and A. B. Aliyu: Continental J. Engineering Sciences 3: 42 - 49, 2008 CONCLUSION AND RECOMMENDATIONS Ammonia – calcium chloride solar absorption icemaker was designed and constructed. The refrigeration cycle was analyzed with their thermodynamic properties expressed in polynomial equations. The coefficient of performance (COP) of the cycle versus the generator temperature at different collector efficiencies was analysed and it was noticed that the collector efficiency is an important factor to consider for the optimum temperature at which the solar absorption cycle operates. The collector efficiency determines the maximum temperature that should be used at the generator in order to achieve the maximum COP out of the system. The COP obtained were in the range of 0.78 – 0.83 which are in agreement with what was obtained by Nelson et al (1977) which gave a COP of 0.75. Also an experimentally based simulation model of a solar powered water chiller reported in Best et al (1992) gave the cycle COP as 0.75. Other activities on solid absorption refrigerators reported in Worsoe (1983), give the cycle COPs in the range of 0.4 – 0.8. These previous results validate what is obtained in this simulation analysis. The simulation was carried out on specific temperatures at the generator, condenser and the generator. A lot of research and development are needed to prove the economic viability of solar absorption ice making technology using locally available materials, in order to compete favourably with vapour compression refrigeration systems. REFERENCES Antonio J.B (2006).” Thermodynamic simulation of a solar absorption refrigeration system, Generator- Heat exchanger”Universidad del Norte. Barranquilla, Colombia. Best R, (1992). “Evaluation of Solar Air conditioning System Operating in Mexicalli. Second world Renewable Energy Congress Reading.Baja, California. Farber E.A, (1970). Design and performance of a compact refrigeration system. Engineering progress at the University of Florida, 24 (2): 17. Iloeje O.C (1995) “Treatments of Calcium Chloride for use as a Solid Absorber in Solar Powered Refrigeration”, Technical Report No. SE-I, Oct 1982, Solar Energy Project, Univ. of Nigeria, Nsukka. Musbahu U. (2008): Design, Construction and Performance Analysis of Solar Absorption Icemaker. M. Eng. Thesis, Department of Mechanical Engineering., Bayero University, Kano. Nielson P. (1977). “Development of Solar-Powered Solid-Absorption Refrigeration System,-Part 1: Experimental Investigation of the Generation and Absorption Process”. Report No. F30-77, The Technical Unvi. of Denmark, Refrigeration Laboratory, Sumathy, K and Zhongfu. (1999) A Solar- Powered Ice-maker with the solid adsorption of activated carbon and methanol. International Journal of Energy Research, 517-527. Worsoe-Schmidt, (1983). “Solar Refrigeration for Developing Countries using Solid Absorption Cycle, International Journal Ambient Energy 4(3): 115 - 124 Received for Publication: 20/04/2008 Accepted for Publication: 15/05/2008 Corresponding Author: A. B. Aliyu Mechanical Engineering Department, Bayero University, Kano Email: abaliyu@yahoo.com

50

Continental J. Engineering Sciences 3: 50 - 55, 2008 ©Wilolud Online Journals, 2008.

PROCESSING AND PROPERTY EVALUATION OF MUBI CLAY TOWARDS GLAZED FLOOR TILES PRODUCTION

Nathan .C.

C/O Iliya Kaigama: Department Of Chemistry, Adamawa State University, Mubi, P.M.B 25, Mubi Adamawa State Nigeria

ABSTRACT Five different types of clay samples were mixed with various percentages of Silica sand to produced glazed ceramic floor tiles. Manual compression force was used to compress the mixture to produce ceramic tiles. The tiles were dried and heated using an electric furnace at a temperature of 1250OC. the tiles produced were experimentally tested for their porosity, hardness and impact. The results of the properties of the ceramic tiles produced were found to fulfill or present reasonable values with the imported floor tiles in market. The aim of the present work is to produce ceramic glazed floor tiles and investigate the effects of locally available clay samples and additives on the quality and its properties. KEYWORDS: Ceramic, glaze, porosity, hardness, impact, furnace.

INTRODUCTION Tiles are thin slabs used for flooring, paving or making drains. They may be made of clays burnt in kilns (ceramic tiles) and concrete (concrete tiles) The manufacture of ceramic tiles involves careful preparation of clay and compression moulding or extrusion process to be followed by drying and firing operation and/or finally glazing operation. A mixture of clay and water has unique plastic properties which can be shape and fired inn the kiln at the sintering temperature, the alkali flux gives rise to a molted glass which partly dissolves the other oxides constituents and binds the together on cooling. Therefore, the tiles are glazed by applying to the surface an appropriate powder mix which forms a glass on firing. Ceramic materials are relatively cheap and easily located across the country. Characteristic of floor Tiles. The most noticeable of ceramic floor tiles is that they are hard and brittle at room temperature. Mechanical properties are influenced by their structure. Variation in mechanical behavoiur result from the various combination of covalent, ionic and Vanderwaals bonds that exist within the structure. Ceramic floor tiles are usually non – conducting to Electricity. The electrical resistivity decrease with the introduction of impurities in their structure. The have high melting points than commonly used metals and their thermal conductivity fall between those of metals and polymers. Thermal shock resistance is a function of thermal conductivity and expansion co – efficient. Ceramics with a lower thermal expansion coefficient and higher conductivity usually exhibit better thermal resistance.

MATERIALS AND METHODS Five different types of locally available clays namely: Digil clay (A), Vimtim clay (B) Lokuwa clay (C) Lamurde clay (D), Works clay (E), were used singly as base clays with others as additive and silica as flux (Table 1). The clay lumps as sourced were crushed to smaller sizes, dried and finally grounded into five clay particles. The physical properties of the five clay samples plus the silica sand were determined as given in table 2. The binder used was sodium silicate (waiter glass). This is used to obtain a stable, quick – casting slip in order to have as specific gravity together with a pourable condition. It also gives a firms cast. Fields per was also added to improve the strength of the tiles. The quantity was 5% per volume of the plastic body. This work was carried out in the department of agric engineering, college of Agriculture Adamawa state.

51

Nathan .C: Continental J. Engineering Sciences 3: 50 - 55, 2008 FIG 1. CASTING STAGES

Clay paste

Stage 1

Stage 2

Rammer

Stage 3

Clay Mould

Stage 4

Wet tile

Slab

52

Nathan .C: Continental J. Engineering Sciences 3: 50 - 55, 2008 Table 1: Composition and Location of clay’s Sample investigated weight. Base clays Location Varying % main composition % additives composition

Clay (A) Digil area of Mubi North Adamawa State.

Silica + Clay A(60%) 20% Clay B 20% Flux (feldspar)

Clay (B) Vimtim area of Mubi Adamawa State.

Silica + Clay B(65%) 22.5% clay C, 12.5% Flux (feldspar)

Clay (C) Lokuwa area of Mubi North Adamawa State.

Silica + Clay C(60%) 22.5% clay A, 10 clay D, 15% Flux (feldspar)

Clay (D) Lamurde area of Mubi North Adamawa State.

Silica + Clay D(65%) 10% clay D, 10% clay a, 15 Flux (feldspar)

Clay (E) Works area of Mubi North Adamawa State.

Silica + Clay E(60%) 20% clay D, 20% Flux (feldspar)

The composition mixes were based on the clays on the clays compositions mixes for the manufacturing of hard porcelain products.

Table 2: Physical properties of clay S/N Physical

Properties Clay A Clay B Clay C Clay D Clay E Silica

1 Colour Reddish brown

Creamy grey

White White Creamy white

Creamy

2 Specific gravity

2.31 2.03 2.00 2.01 2.62 .2.73

3 Clay content 4 % Moisture

content As received crushed

2.56 1.28 1.29 19.7 18.5 5.67

5 Grain fineness ratio

86.5 69.87 83.82 9.73 64.92 65.4

TILES PRODUCTION The collected clays were ground to small pellets and then soaked in a drum of water for four days, on the fifth day the wet clays was sieved. A 500цm mesh was used. The purpose of the sieving was to remove sand and other organic materials, such as plant roots and dead matter. After sieving the wet clay was poured in a container and allowed to settle to the bottom of the container. The settlement took two days to achieve. After the two days, the remaining water drained off and the wet clay brought out to an open space to allow for more straining of water at standard temperature of about 23%. This process is known as aeration of the wet clay. The aim of the aeration is to bring the clay to a workable state and enable the composition to loose about 60% moisture to the atmosphere. It also makes the composition more plastic. After the aeration feldspar and water glass 5% each were added to the composed clay body. The water mixed clay mixture was kneaded until the mixed clays become plastic and workable. The clay mixture were rolled into ball shape and tempered to store away in a warm dark place for between 5 to 7 days. The tempered clay’s samples were moulded by pressing it in a 20cm x 20cm x 0.5 cm to produce a tile of square dimension. The casting was done in four stages.

Stage 1: The plastic body was well kneaded and poured into the mould box, this material fill the box which was placed on a flat board of dimension of 20cm x 20cm 0.5cm.

Stage 2: A piston was used to ram the body well into the box. The piston is also made of wood with square based.

53

Nathan .C: Continental J. Engineering Sciences 3: 50 - 55, 2008

Table 3: Volume of water absorbed by the tiles Tile Initial volume of water (V1)cm3 Final volume of water

(V2)cm3 A B C D E Imported Tiles

1000 1000 1000 1000 1000 1000

995 995 995 995 995 995

V1 – V2 = V Where V2 = Final volume V1 = Initial volume V = volume of water absorbed by the tiles

Table 4: Comparison of properties between Local and imported floor tiles. Tiles Porosity (cm)3 Hardness (mob) Impact (Joules) A 5.0 20.0 138.0 B 2.0 19.0 139.0 C 5.0 20.0 140.0 D 10.0 15.0 110.0 E 5.0 20.0 131.0 Imported tiles 5.0 20.0 140.0

Stage 3: Further ramming of the body was obtained, the expected thickness of the tile is 0.5cm and the 0.10cm extra is to allow for any shrinkage during the drying and firing process.

Stage 4: The box was opened from the sides and the casting left on the board. It was allowed to dry under normal atmosphere conditions for 14 days. This was done to avoid cracking during fist firing.

Porosity Test A knowledge of the porosity of the tiles is important for it serves as a measure of maturity and also allows the evaluation of the clay body for a specific purpose. The entire specimen (imported tiles and locally produced tiles) were immersed in different containers containing equal volume of water, which was measured to be 1000cm3. The tiles were left for a period of 5 days after which they were brought out simultaneously. The volume of water left was measured and tabulated in Table 3. Hardness Test The hardness test was done using a scratch test approach. In the test two control test materials were used. A block of limestone and a block of igneous rock. In the an attempt was made to scratch the surface of both the imported and locally produced tiles with first block of limestone and secondly with a block of igneous rock. In the first test, the limestone was able to scratch both tiles, in the second test the igneous rock was unable to scratch, all tiles, the hardness of all tiles lies between the number of igneous rock and the number of limestone. Impact Test The machine used for the test is the sharply impact testing machine. The test was done first for the local floor tiles and then for the imported floor tile. In conducting the test a notch was made on each test specimen. The specimen was supported so that it was loaded horizontally as a simple beam between two anvils with the notch at mid – span.

The striking edge of the pendulum weight strikes the specimen opposites the notch, the energy expended in rupturing the specimen was found by the formula;

54

Nathan .C: Continental J. Engineering Sciences 3: 50 - 55, 2008 Wh – Wh (2)

Where W = impact load of swinging the weight from a vertical height, h = strike and rapture of the notched specimen and then the load stops at a vertical height (h)

RESULTS AND DISCUSSION Table 1 shows the composition mixes and location of clay’s sample investigated by weight. The reason for mixing the % additives in table 1 is, at a composition mixes less than the one’s in table 1 for the various base clays A to E, before drying crakes were all over the tiles and at a composition mixes greater than the one’s in the table, the tiles also cracks. Different and several trials were conducted but non could produce a tile after drying. The percentages used were able to give stable and hard tiles that the properties were compared reasonable with the imported tiles in market. Table 2 shows the physical properties such as specific gravity, clay content, etc. For clay samples and silica sand used for the production of ceramic floor tiles. Composition of properties between local and imported floor tiles were give in table3. For tiles produced from clay sample A, B, C and E their porosity is the same. The water absorbed by the tiles 5cm3 each, which is the same with the imported floor tiles. Tiles D gave relatively high water absorption 20cm3. This higher amount of water may be as a result of the composition mixes. The hardness test of the locally produced tiles is the same, or compare reasonable with the imported floor tiles which is 20mob. Tiles produced from sample D gave Low hardness of 15mob. The impact test conducted for both the locally produced floor tiles and the imported floor tiles is the same 140 Joules, except for slight decreased in sample A, B and E. Tiles produced from sample D gave low impact test which is 110 Joules. Linear expansion and shrinkage test could not be done because the glaze will not allow for accounts result. And since the tiles will be used at temperature above 100OC these test were ignored. It is obvious that the locally produced floor tiles have almost the same strength and quality with the imported tiles. The slight difference in quality might be as a result of the type of binder used for the local production of the tiles, which might be different from are used for the imported tile. It can also be seen that only D composition mixes could not be used to compare reasonable with the imported clay tiles. CONCLUSION. This research work was carried out to shows that we can actually produced or own local floor tiles using the abundant clay we have in Mubi north local government area of Adamawa state, thereby reducing our importation of foreign of tile; this was confirmed by the result obtained from the test conducted. It can be seen clearly that only tiles D composition mixes cannot be used to compare reasonable with the imported clay tiles. The cost of executing the project is relatively cheap, although, it could have been cheaper if a local kiln was used and more tiles produced.

REFERENCES: Gilliot, E.J. (2001): “Clay in engineering Geology” 1st Edition Eslevier Grimehaw, R.W(2003): “The Chemistry and Physics of clays” Ernest Ben Publishers, London. Peter, S.M. (1998): “Understanding clay, Recognition and processing” Volunteers in Technical assistance, (VITA), USA.

55

Nathan .C: Continental J. Engineering Sciences 3: 50 - 55, 2008 Prienion, A.R. (200): “Glass ceramics, white wares porcelain enamel”, A.S.T. M 15:02 Prienion, A.R. (1988): “Construction A.S.T.M 4:05. Ryan, W. (1998): “Properties of Ceramics Raw materials” Devices Publishe House Ltd New Hilvik. Samuel, J.O (1995): “Manufacturing of ceramic tiles using firing techniques” M.Eng Research Project Department of Mechanical Engineering University of Ilorin, Ilorin – Nigeria. Singh, S.(1979): Engineering materials”. Vikas Publishing House Ltd, New Delhi. Stafford, C.E (1980): “Modern industrial ceramics” 1st Edition Bobs – Merrill Co Publishers, New

York. Website (2007): Scielo.br/php, pp1 – 8. Received for Publication: 25/03/2008 Accepted for Publication: 15/05/2008

56

Continental J. Engineering Sciences 3: 56 - 63, 2008 ©Wilolud Online Journals, 2008.

A MICROCONTROLLER-BASED HIGHWAY-RAILWAY LEVEL CROSSING TRAFFIC CONTROLLER

J. A. Enokela1 and E.J. Ibanga 2 1Department of Electrical Engineering, University of Agriculture, P.M.B 1273, Makurdi, Nigeria

2Department of Physics, Nasarawa State University, P. M. B. 1022, Keffi, Nigeria.

ABSTRACT Highway-railway level crossings across the country have witnessed a number of fatal accidents in the past. Many of the level crossings in the rural areas are not protected by level crossing gate signals. In the urban areas where these provisions are put in place, the operation of the level crossing gate is usually entrusted to the level crossing keeper- who opens and closes the gate against road traffic at times that he deems necessary. This results in the closing and opening of the gate earlier or later than necessary as well as the intervention of a human superintendent who may not be on duty at the correct time. These factors cause difficulties and possible accidents for the highway/railway users. This work describes a control system that uses a microcontroller to handle traffic flow across a major and typical highway-railway level crossing located in an urban centre. It is seen that the incorporation of computer methods into the operation of the level crossing improves its safety, speed and reliability. KEYWORDS: Highway, Railway, level crossing, control, traffic, microcontroller,

INTRODUCTION Highway-Railway level crossing traffic signal controls in the country have traditionally been operated by level crossing keepers who use flags and signal lamps mounted on gates to warn highway users of the approach of a train. These keepers, on sighting a train, physically close the railway gate against road traffic until the train has passed after which the gate is opened (Nigerian Railway Corporation: General Rules, 1979) . This traditional method is very much dependent on the human factor and has important shortcomings:

(i) There is no preemption in the system to alert the highway users of the approach of a train before the railway gate is closed against the road traffic.

(ii) The gate is generally closed against road traffic for a longer period than absolutely necessary to secure the safety of the public and train.

(iii) The entire operation depends on the level crossing keeper who may not show up for his duty on time as has been known to happen especially in poor weather conditions.

These shortcomings have led to lots of inconvenience for both the railway and highway users as well as the occurrence of accidents on such level crossings.

Traffic controls at level crossings are generally required to have some form of preemption. This is the transfer from normal operations of signals to a special control mode. Rail traffic preemption often occurs when a train approaches highway-rail grade crossings (Metrolinks Ttrain, 2004 and Institute of Transport Engineers, 2004). Preemption defines various times and these include:

(a) Advanced Preemption time which is the notification of an approaching train that is forwarded to the highway traffic signal controller unit for a period of time prior to activating the railway active warning devices.

(b) Pedestrian Clearance time is the time provided for a pedestrian crossing on a crosswalk after leaving the curb or shoulder, to travel to the centre of the farthest traveled lane or to a median. At a normal walking speed of at least 1.2m/s the walk interval should be at least 7 seconds.

57

J. A. Enokela and E.J. Ibanga: Continental J. Engineering Sciences 3: 56 - 63, 2008

Figure 1: Traffic control System (Enokela and Ogah, 2005).

(c) Queue Clearance time is the time required for the design vehicle stopped within the minimum track clearance distance to start up and move through the minimum track clearance distance.

(d) Minimum Warning time is the least amount of time active warning devices shall operate prior to the arrival of a train at a highway-rail grade crossing.

The knowledge of these times are necessary to enable us calculate the length of time required for the gate to be closed against the road traffic (Institute of Transport Engineers, 2004). The effective time that the crossing would be blocked by a train can be estimated from equation (1)

( ) )1(47.135 LLsLr +=

Where; L = train length and s = train speed.

The factor of 35 assumes approximately 25 seconds before the train enters the crossing plus 10 seconds after it clears the crossing that the crossing would still be blocked by gates. These times may be adjusted us necessary for individual crossings (Institute of Transport Engineers, 2004). Various methods have been used to design traffic controllers at highway-railway level crossings (K.L.E. Society’s Polytechnic, Hubli, 2003; James David Chapman’s web site, 2004; and Goja, and Orhungur 2004). This work uses a microcontroller for the design of the traffic controller. The advantages of this method include low power consumption since less hardware is required, and a high reliability that is comparable to that achievable using a full-scale microprocessor. MATERIALS AND METHODS The traffic controller has been designed using the Microchip’s PIC18F2585 microcontroller. This microcontroller has up to 48K bytes of flash program memory space, 4K bytes of RAM as well as 1K bytes of EEPROM. It also features a CPU having a standard set of 75 instructions (Microchip Technology Inc. 2004). The design was done in 2005 at the Electronics Laboratory, University of Agriculture, Makurdi, Nigeria. System Operation The traffic controller system that has been developed is indicated in figure 1 (Enokela and Ogah, 2005). The system consists of two sensors placed 1000m apart, one on each side of the road. The sensor employed is a simple dc type which operates such that a train on the section of the affected track will trigger the switch thus generating an interrupt for the control unit circuitry. The control unit then enters the preemption mode. Visual and audible warning signals are sent out to alert the highway users of the

58

J. A. Enokela and E.J. Ibanga: Continental J. Engineering Sciences 3: 56 - 63, 2008 approach of a train. The visual signals consist of red, yellow, and green lights mounted on the gate while the audible signal is a loud siren. Once the approach of a train has been detected, the control unit

Define Processor

Load device specific files

Configure Processor

Initialize program counter

No train: Turn on Green light

Interrupt Routine

Start

Any interrupt? Yes

Wait for interrupt

No

Fig. 2: Flow Chart for Traffic Controller

59

J. A. Enokela and E.J. Ibanga: Continental J. Engineering Sciences 3: 56 - 63, 2008 triggers a siren and the yellow light is activated for 20 seconds so that all road users will have adequate time to cross the rail. This period represents the warning time. Warning times should not exceed 40-50

?

Interrupt

Turn off green light

Turn on siren

Turn on yellow light

Delay 20 seconds

Close gate

Turn off yellow light

Turn on red light

Delay 90 seconds

Further 90 seconds delay

Turn off siren

Turn off yellow light

Turn off red light

Open gate

Turn on green light

No

Yes

Second sensor tripped?

Return

Fig. 3: Interrupt Service Routine

60

J. A. Enokela and E.J. Ibanga: Continental J. Engineering Sciences 3: 56 - 63, 2008

seconds so that undesirable driver behaviour such as attempting to drive around gates can be avoided (Federal Highway Association, 2004).

At the expiration of the warning time the gates are closed against road traffic and the warning light turns red. The audible signal is still turned on. The gate remains closed against road traffic for a period

G2

° °

°

°

° °

R2

R4

S2 T2

+Vcc +Vcc

J

CK

K CLR

FF2

Q

Q

G4 OS2

INT2

C2

R6

+Vcc

R8

T4

+Vcc

R10

°

° °

° °

°

R1

R3

S1

T1

+Vcc +Vcc

J

CK

K CLR

FF1

Q

Q

G3 OS1 INT1

C1

R5

+Vcc

G1

R7

T3

+Vcc

R9

Fig. 4: Sensor and Interrupt Control Circuit

61

J. A. Enokela and E.J. Ibanga: Continental J. Engineering Sciences 3: 56 - 63, 2008

determined approximately by equation (1). When the train triggers the second sensor the gate light turns yellow for 20 seconds after which the gate opens and the gate light turns green. The audible signal turns off thus completing the cycle. Program Developments The global flow chart for the traffic controller is indicated in figure 2. The program has been developed using the assemble language. The processor used is defined in accordance with the assembler (Microchip Technology Inc. 2005a). The processor’s specific files are loaded and the processor is appropriately configured. The program then goes into an infinite loop while checking for interrupts. In the absence of a train the green light at the gate is turned on and the gate is opened to road traffic. The arrival of a train is acknowledged by the generation of an interrupt signal from the sensor.

Various events occur in the interrupt routine (figure 3). These consist of turning on the siren and the yellow traffic light to warn the highway users of the approach of a train. This is followed by a 30-second warning time to enable all road traffic to clear off the railway. The gate is then closed against road traffic and the red light is turned on. The control system goes into a delay mode to allow the train to pass. When the train trips the second sensor there is a further delay to allow the last train coach to pass through the gate which opens thereafter. The siren is then turned off while the green light is turned on to indicate the “all clear” for the road users. It should be observed that once the first sensor from either direction has been tripped and the gate closed, the gate will remain closed indefinitely until the second sensor from either direction is tripped. This situation allows for a train to stop between the sensors after tripping the first sensor from either direction.

PIC

18F

2585

28

27

26

25

24

23

22

21

18

17

16

15

14

13

12

11

1

2

3

4

5

6

7

10

9

RB7

RB6

RB5

RB4

RB3

RB2

RB1

RB0

RC7

RC6

RC5

RC4

RC3

RC2

RC1

RC0

RA0

RA1

RA2

RA3

RA4

RA5

RA6

RA7

MCLR VDD

10k

20

+5V

Red Light

Yellow Light

Green Light

Motor signal-open gate

Motor signal-close gate

Audio signal

INT1

INT2

VSS

8, 19

Fig. 5: Traffic Controller Circuit Showing Various Control signals

62

J. A. Enokela and E.J. Ibanga: Continental J. Engineering Sciences 3: 56 - 63, 2008 Hardware Design The sensor and interrupt control circuit is given in figure 4. The flip-flops FF1 and FF2 are configured as T-type (Hill and Peterson 1981) and are cleared (Q = 0) at power on. This condition is assured by the power-on reset circuits G1 and G2. When the train wheels march the sensor switch S1 the flip-flop FF1 is clocked and the one-shot circuit (OS1) fires a pulse which constitutes the interrupt INT1 for the processor. INT2 is generated in a similar manner. If INT1 occurs first while INT2 occurs later then INT1 controls the turning on of siren, yellow light, closing of gate and turning on of red light while INT2 turns off the siren, the yellow light, the red light, opens the gate and turns on the green light. However if INT2 occurs first the roles are reversed. This behaviour of the system is accomplished in software. The question of whether INT1 or INT2 occurs first depends on the direction of approach of the train. The microcontroller connection showing various control signals at the I/O pins is shown in figure 5. The interrupt signals (INT1, INT2) are inputs to the microcontroller while the other signals are output from the microcontroller and are used for various control functions. RESULTS AND DISCUSSIONS The program for the traffic controller was written with the aid of Microchip’s MPLAB IDE version 7.50 (Microchip Technology Inc. 2005b). After assembling the program, software simulation was carried out and the program was comprehensively debugged using the MPLAB IDE’s simulator. The components were then wired together in software environment using the NI Multisim Circuit Design suite version 10.0.1 (National Instruments, 2007). Normal operation of the circuit without interrupts was observed. The circuit was interrupted by operating the switches S1 and S2 and the sequence of lighting of the LEDs connected to the port pins was observed to be correct. LEDs were used in place of the motor drive signals. The circuit was then built on a circuit board with the components properly soldered together. The hexadecimal (hex) file generated from the assembly process was transferred into the program memory of the microcontroller with the aid of the MPLAB In-Circuit Debugger MPLAB ICD2 (Microchip Technology Inc. 2005c) and a hardware simulation was carried out to observe the performance of the physical circuit. Once more light emitting diodes were used in place of the motors. The lights turned on and off as desired. CONCLUSION AND RECOMMENDATION A highway–railway level crossing traffic controller that operates without the intervention of a human gate keeper has been designed and implemented. The design has utilized a microcontroller for cost effectiveness. The traffic controller can be interfaced with a high-powered motor required to operate the gate and an audio system that would put out a loud warning signal. REFERENCES

Enokela, O.K, and Ogah, D.A. (2005) “Design and construction of a microprocessor based railway traffic controller”, B.Eng. Thesis, University of Agriculture, Makurdi, unpublished.

Federal Highway Association, (2004), “Guidance on traffic control devices at highway-rail grade

crossings”, Executive summary, www.safety.fhwa.dot.gov/media

Goja, A.J. and Orhungur, M. (2004) “Design and construction of a traffic control system at a railway crossing”, B.Eng Thesis, University of Agriculture, Makurdi, , unpublished.

Hill, F.J., and Peterson, G.R (1981) Introduction to switching theory and logical design, John Wiley and Sons, New York, 3/e, 1981.

Institute of Transport Engineers, (2004), Preemption of traffic signals near railroad crossings, www.ite.org/standards.

James David Chapman’s web site, (2004) “Traffic light project”, www.users.gloalnet.co.uk/~jchap

K.L.E. Society’s Polytechnic, Hubli, (2003), Microprocessor based railway control system, www.vidyapatha.com/student.proj/electronics.

Metrolinks train, (2004), Preemption guidelines for highway–rail grade crossing, www.metrolinkstrains.com.

63

J. A. Enokela and E.J. Ibanga: Continental J. Engineering Sciences 3: 56 - 63, 2008

Microchip Technology Inc. (2004) Data Sheet PIC18F2585/2680/4585/4680, 2355 West Chandler blvd., Chandler, Arizona.

Microchip Technology Inc (2005a) MPASM Assembler, MPLINK Object Linker, MPLIB Object Librarian User’s Guide, , 2355 West Chandler blvd., Chandler, Arizona.

Microchip Technology Inc. (2005b), MPLAB IDE User’s Guide, , 2355 West Chandler blvd., Chandler, Arizona.

Microchip Technology Inc (2005c), MPLAB ICD 2 In-Circuit Debugger User’s Guide, 2355 West Chandler blvd., Chandler, Arizona.

National Instruments (2007), Multisim user guide, 11500 North Mopac Expressway, Austin, Texas.

Nigerian Railway Corporation: General Rules, 1964, (as amended in 1979), Re-printed by the Railway Press, Ebute-Metta, Lagos.

Received for Publication: 07/05/2008 Accepted for Publication: 25/05/2008 Corresponding Author: E.J. Ibanga Department of Physics, Nasarawa State University, P. M. B. 1022, Keffi, Nigeria. E-mail: enojamesibanga@yahoo.com

64

Continental J. Engineering Sciences 3: 64 - 71, 2008 ©Wilolud Online Journals, 2008. ADMIXTURE OF USED ENGINE OIL BLENDED WITH KEROSENE AS A SUBSTITUTE FOR

INDUSTRIAL FUEL

Aji I.S, El-Jummah A.M, Aji M.A and Ifeanyi N.D. Department of Mechanical Engineering, University of Maiduguri

ABSTRACT The admixture of used engine oil blended with kerosene as a substitute for industrial fuel was experimented to determine it’s viability for use as an industrial fuel in foundry workshop. Various types of industrial fuel exist, some of which include diesel containing 84.4% of carbon, 11.7% of hydrogen, 1.4% of nitrogen and 0.60% of sulphur, a boiling point of about 5500F (287.780C), of 250oF (121.110C) and it fractionated pouring temperature of 5150F(268.330C). Equipment used for the experiment include crucible furnace, fuel tank , inlet pipe, wire gauze, flexible hose, the injector nozzles, the electric motor blower, the delivery hose, the control knob, the mixture chamber, the combustion chamber, and the crucible pots (the excavators). Four liters of the mixture of used engine oil to kerosene at a varying ratio of 2:1, 3:2, 5:3,5:2, 3:1, 4:1, 5:1 and 6:1 was used to carry out the test. Most appropriate result of the experiment was obtained at a combination ratio of 6:1 with four liters of the mixture melting 10kg of zinc in 22 minutes. KEY WORDS: Melting, mixture, fuel, furnace, combustion

INTRODUCTION This work was carried out with the desire to reduce the cost of fuel used in our furnaces and burners by making use of used engine oil mixed in a certain proportion with kerosene; the used engine oil taking the higher proportion of the mixture. This will serve as an alternative to diesel, coal, and other hydrocarbons which will be used for firing industrial equipments like boilers and in a foundry workshop. Industrial fuel is normally sourced from crude oil. Most scientists believed that oil and natural gas were formed millions of years ago, but the only living then were tiny sea plants and sea creatures called plankton. The seas were full of plankton, the water was like thick soup, and the suns energy helped the plankton to grow. Everything around us is made of chemicals; these chemicals are of two types, carbon and oxygen. When the plankton died oxygen left their bodies. This is only why carbon and hydrogen are in the remains of the tiny plankton that later turned into oil and natural gas. This natural gas (crude oil) is extracted from the ore in the soil, which is being refined into industrial fuels such as gasoline, diesel oil, kerosene and black oil. (Sauvain,1987). Aim and objectives This work is aimed at producing a cost effective industrial fuel as an alternative to the present fuel which is majorly expensive, for use in industrial boilers and foundry workshop. This will help reduce the cost of generating heat in small and medium scale industries and also help reduce environmental pollution by recycling used engine oil instead of throwing it away. Scope of the work This work will be limited to using engine oil that has been used by an automobile vehicle after its original lubrication value has been used up and then mixed with kerosene. LITEREATURE REVIEW Industrial fuels are fuels used for the consumption in industrial machines. They include diesel fuel, black oil, kerosene and gasoline fuel etc. (Nelson, 1958) Various types of industrial fuel exist, some of which include diesel containing 84.4% of carbon, 11.7% of hydrogen, 1.4% of nitrogen and 0.60% of sulphur, a boiling point of about 5500F (287.780C), of 250oF (121.110C) and it fractionated pouring temperature of 5150F (268.330C). (Lowson, 1970)

65

Aji I.S et al: Continental J. Engineering Sciences 3: 64 - 71, 2008 It is used in heavy vehicle such as trucks and buses, and is becoming increasingly popular in cars and vans as light diesel engine technology develops. They are used in factories and building, for stationary equipment such as generator, furnace and small boilers. (Timasher,Sakharo et al 1989) Black oil is another type of industrial fuel obtained from waste products collected after the major refining has taken place. Black oil has a boiling point of about 7800F (415.560C), flash point of 4000F (204.440C), dark brown in color and not as finely processed as light oil. They are widely used and sought after for ship propulsion, steam generator and power plants. (Lowson, 1970) Kerosene is one of the refined products gotten from crude oil. It has the following chemical analysis 85.6% carbon, 12.4% of hydrogen and 0.37% of sulphur. Kerosene has a boiling point of about 3350f (168.330C), its vapor pressure is 2110F (99.440C) while the flash point of 1100F (43.330C) and its fractionated pouring temperature of 3050F (151.670C). It is the lightest, most volatile of the distillate fuel grades. It also has the following properties; Appearance-Clear and Bright; Colour (Saybolt), (min) + 20; Specific gravity at 15oC is 0.800 – 0.825 kg/m3 Petroleum (gasoline) is the major product in an industry of many by products. The chemical analysis of petroleum is 85.5% of carbon, 14.2% of hydrogen and some has 36% of oxygen. It has boiling points of about 800F (26.670C), its vapor pressure of about 20psi, and has fractionated pouring temperature of 60 0F (15.560C) The flash point of a fuel is the lowest temperature at which vapor giving off will ignite when an external flame is applied under standard condition. The oil is said to be “flashed” appears and instantaneously, propagates itself over the center surface. The oil flashes because a flammable mixture results when it is heated sufficiently causing vapor to emerge and mix with oxygen in the air. (Nelson, 1958) The flash point is defined to minimize fire risk during storage and handling the minimum flash point, for the machinery space of a merchant ship is govern by the International Legislation and the value is 600C for fuels use for emergency purposes external to the machinery space, the flash must be greater than 430C. The normal maximum storage temperature of a fuel is 100C below the flash point, unless arrangements are otherwise made. (Nelson, 1958) Some of the other properties required of a good fuel are Density which is the absolute relationship between mass and volume at a stated temperature. The S.I unit is kg/m3 at a reference temperature 150C. (Clair, 1979); Viscosity which is a property of the internal resistance of a fluid that opposes the motion of adjacent layers. The unit of measure of the resistance in S.I unit is Pascal; Pour point which is the lowest temperature at which a fuel can be handled without excessive amount of wax crystal forming out of solution. If a fuel is below the pour points, wax will begin to separate out and this will block filter; it’s carbon residue which is the tendency to form carbon deposited under high temperature conditions in an inert atmosphere. For straight run fuels, the typical value of carbon residue is between 10-12%mm, while for fuel derived from secondary conversion processing the value depends upon the severity of the process applied. On a global basis, this is typically 15-16%mm but in some areas can be as high as 20%MN/M. (Clair,1979); Sulphur content which is a natural occurring element in the crude oil and concentrate in the residual component of the crude oil distillation process. Hence, the amount of sulphur in the fuel oil depends mainly on the source of the crude oil due to a lesser extension on the refining process. Typically for residual fuel on a world-wide basis, the value is in the order of 2-4% m/m. Sediment By extraction can be defined as the insoluble residues remaining after extraction by toluene. These insoluble residues are contaminants such as sands, dirt and resist scales that are not derived from the fuel. Such definition and test method are suitable for clear distillate fuels but are not applicable to residual fuels which are of greater importance to the total sediment contents of the fuel including hydrocarbon material which relates to stability. Stability or residual fuel may be defined as the ability of fuel to remain in unchanged condition despites circumstances which may tend to cause change or more simply as the resistance of oil to breakdown. Conversely, instability would be the tendency of a residual fuel to produce a deposit of aspbaltenic sludge as a function of time or temperature.

66

Aji I.S et al: Continental J. Engineering Sciences 3: 64 - 71, 2008 In 1980s, three sediments test method were developed, where each relates to various aspects of the sediments. They are the total sediment extent (TSE), total sediment accelerate (TSA) and total sediment potential (TSP) methods. Each of the method is of filtration through a double filter paper and each differs in the treatment of the fuel sample prior to filtration. In the case of the TSE procedure, there is specific sample preparation and the sediment result relates to the dirt in the sample. For TSA procedure, the sample is mixed with 10% ce-tane –C16H34 (a colorless oily hydrocarbon) and is being heated for 1 hour at 1000C before filtration. In the case of TSP test the sample is heated for 24hours at 1000C to stimulate thermal ageing of the fuel. In the event of lack of stability of a fuel it is likely that, filter blockage and combustion problems will be experienced. If there is any difficulty in identifying the nature of these materials, a small portion should be placed in an open container and be allowed to float in a vessel containing water at a temperature of 60 to 700C. Many materials will therefore melts but an asphaltenic sludge will not (fig 1)

(Timasher, Sakharo; et-al 1989) Compatibility Every fuel is manufactured to be stable within tendency itself, with this, it does not have the tendency of producing asphaltenic sludge and it does not necessarily follow that two stable fuels are compatible when blended or mixed together while incompatible is the tendency of a residual fuel to produce a deposit on dilution or on blending with other fuel oils. Problems of incompatibility within fuels are more but when they happen, there results are severe. Typical problems are sludging and blockage of bunker and service tank pipe runs, filters and centrifuge bowls. In extreme circumstances, the only remedy is the manual removal of the sludge build up. It is impossible to give precise advice on probability of compatibility problems between two fuels but the risk of incompatibility can be ranked. A blend is regarded as being stable if it is homogenous immediately after preparation. The remains in normal storage, at no time produce or tend to produce sludge on a significant scale. Under these circumstances, the fuels that form the blend are being considered as compatible with each other. By definition, residual fuels are the remains of the crude oil after the more valuable component have been extracted from the manufacture of petroleum product. The chemical composition of residual fuels is difficult to define as it depends upon the source of the crude oil and the manufacturing process used in the extraction of the petroleum products.

Sediment Screen

Stability Screen

Fig1: Sediments test method of fuel samples by filtration

TSE

TSA TSP

Fail, reject

Fail, reject

Fail, reject Pass OK4

67

Aji I.S et al: Continental J. Engineering Sciences 3: 64 - 71, 2008 However, when considering the chief consistent of residual fuel an appreciation that can be made on the sludge forming mechanism. These constituents of a residual fuel include asphalt, resins and liquid hydrocarbon. The generic terms ‘asphaltanes ‘covers a wide range of heavier hydrocarbon structures. Besides, having high molecular weight and high hydrocarbon ratios, they may also contain small amount of other elements, depending on the source of the crude oil. Asphaltanes are delivered to exist in residual fuel as ‘micelles’. The resins can be considered as low molecular weight asphaltanes and these resins produce time solutions (i.e. molecular dispersion). The resin molecules in an oil medium of residual fuel are known as ‘maltanes’ while the liquid hydrocarbons are in oily weight than the resins, which acts as a solvent for the other constituents. Thus a residual fuel oil is generally considered to contain a disperse phase of asphaltanes complex with high molecular weight component of the maltenes (resins) and liquid hydrocarbon in the form of a micelle . The continuous of intermiceller phase consist of ion molecular weight constituent of the maltenes. In this ways one can visualize a general decrease in carbon/hydrogen ratio and molecular weight from the center of the micelle through to the continuous phase. This is shown diagrammatically in the figure; although, the hypothetical zones are shown separately. Although, they merge with each other so there is no distinct interphase between the micelle and intermiceller phase. In conditions shown, equivalent exists and the ‘micelles’ are considered to be ‘peptized ‘(i.e. colloidal dispersed). If, however, the carbon/hydrogen ratio of the Maltese is lowered, say by the introduction of a paraffin diluents, the resin which are absorbed in the asphaltanes are to a certain extent, absorb. This result in the asphalt particles got is being completely surrounded by resins and they are mutually attracted. This leads to a precipitation which appears as sludge. Fuel A Fuel B High risk low density density Moderate risk high risk high density Lowest risk low density high density The profit margins of fuel delivery are often very small and it is tempting to improve this by water addition that is often difficult to dictate in a visual examination. Reputable suppliers will deliver fuel with water content far below ISO-8217 maximum limits. In practice, the nature of the actual water present may be fresh, blackish or salty depending on the level of sodium as determined by the elementary analysis. On a worldwide basis the salt content of sea water varies but usually in first other terms 100mg/kg of sodium is associated with 1% of sea water. Grass water contamination will be removed by the centrifuge. (Sauvain, 1987) Specific Energy The specific energy of a fuel expressed in mg/kg depends on the composition. For residual fuel, the main constituent are carbon and hydrogen both of which releases energy on combustion. Sulphur also releases energy on combustion but to a lesser extent than carbon and hydrogen. The fuel density is mainly proportional to the ratio of carbon and hydrogen atoms in the fuels Ignition Quality The ignition quality of a fuel is a measure of the relative ease by which it will ignite. For distillate fuels this is measured by ce-tane number. Ce-tane number is determined by testing is a special engine with a variable compression ratio. The higher the number the more easily the fuel will ignite in the engine. For residual fuel, there are two accepted empirical equation both based on the density and viscosity of the fuel. They are calculated carbon aromaticity index (CCAI) and calculated ignition index (CII) The CCAI gives members in the range of 800 – 870, while the CII gives values in that same order as a ce-tane index for distillate fuels of the two equations CCAI values are more frequently quoted. The figure is monogram, which incorporates both CII and CCAI. If the viscosity is fixed and the density is raised the CII value falls and the CCAI value increases. Similarly, the density is fixed and the viscosity is lowered, the CII value falls and the CCAI value is increased, in general values less than 30. For CII and greater than 870, for CCAI are considered problematic if required, further guidance on acceptable on acceptable quality value should be obtained from the engine manufactured. (Clair, 1979)

68

Aji I.S et al: Continental J. Engineering Sciences 3: 64 - 71, 2008 Ash - The ash value is related to the inorganic materials in the fuel oil. The actual value depends upon three factors, firstly the inorganic materials naturally present in the crude oil, secondly the refinery process employed. (Sauvain, 1987) Factors affecting fuel-oil combustion Combustion of fuel This is the amount of heat liberated when a unit quantity of a fuel is burned. It is termed heating value or heat of combustion. This is simply the burning of fuel oil through the mixture of oil and air in the combustion chamber with the right atomizing power to produce the necessary firing. Factors Affecting Fuel and Combustion There are various properties of fuel oil that has effect on it’s combustion. Its presence are endlessly in the fuel oil. They are contained as fuel oil element. Sulphur This is a naturally-occurring element in crude oil. The level of sulphur has a marginal effect on specific energy on combustion process. In diesel engine, its presence in the fuel can potentially give rise to corrosive wear which can minimize the rate of combustion. (Lowson, 1970) Water and Sediment The presence of high level of water contamination in the oil is known to be actually risen to the flash point. Water contaminations can also give a false low flash, particularly in certain mini-flash systems that use change in pressure to detect flash. The boiling off of the water can give a false positive on fuel for instance this can also snuff out the flame in cases when a gas pilot is used. Sediment These are deposits, which exist on insoluble residues. They are contaminant such as sands, dirt and rust scale which give rise to incomplete combustion of fuel in the combustion chamber of the furnace burner. Vanadium and Sodium - Vanadium is a metal that is present in all crude oil in an oil-insoluble form. Vanadium and sodium in combination are high levels which can results in high temperature corrosion damage to value and turbo changer components. Aluminum and Silicon - These are generally accepted that an indication of Aluminum represents the potential presence of catalyst fines. These fines are particles of spent catalyst arising from the catalytic cracking process in the refinery. These fines are in the form of complex Alumino-silicates. If not reduced by the suitable fuel treatment, the abrasive nature of the fines does damage the engine oil particularly the fuel pumps, injectors, pistons, rings and liners. METHODOLOGY This experiment was carried out in Ramat Polytechnic and University of Maiduguri at the end of the year 2007. The equipments employed to carry out the work include crucible furnace, fuel tank , inlet pipe, wire gauze, flexible hose, the injector nozzles, the electric motor blower, the delivery hose, the control knob, the mixture chamber, the combustion chamber, the crucible furnace and the crucible pots (the excavators). The experiment was tested first with diesel and then with the used engine oil so as to compare their efficiency and economic viability. Four liters of industrial fuel (diesel) was poured into the tank and the valve was tightly locked (air and fuel). Ten kilograms of zinc scraps was placed inside the crucible pot and placed inside the furnace. The furnace was lit by pouring some quantity of paper into the furnace and ignited. As the paper was burning the control valve of the fuel and the air control valve was opened; the blower control switch was switched on for the combustion to take place. The starting time for the firing was noted, the control points of the valve was also noted and marked for further control levels. The fuel was allowed to burn off and the final reading of the time was taken. The valves were locked and the electric blower was switched off. The melted scrap inside the crucible pot was emptied into a container. The same procedure was adopted using used engine oil and kerosene. Various ratio of the used engine oil to kerosene was tested.

69

Aji I.S et al: Continental J. Engineering Sciences 3: 64 - 71, 2008

The mixture should be thoroughly mixed to avoid dense fuel burning first (used engine oil) while the kerosene settles and burn last. The mixture is also filtered very well to avoid particles of stones, sand, metal chips, wood e.t.c passing into the system which will block the injector nozzles RESULTS AND DISCUSSION The experiment conducted was used to determine the correct proportion of mixture of used engine oil with kerosene that will help achieve optimum result in foundry application. The results were obtained relative to the rate of burning and the intensity of the firing. The ratios used for the experiment and the times taken to melt 10kg of zinc were as shown in table 1 Table 1 Determination of appropriate combination of mixture

Proportion Time (minutes) Qty (liter) 6:1 22 4 5:1 21 4 4:1 19 4 3:1 17 4 5:2 16 4 5:3 17 4 3:2 17 4 2:1 16 4

Quantity of fuel used 4 liters

Fig. 2: Testing of different types of fuel samples The result showed that with higher percentage of kerosene in the mixture, the intensity of burning is very high. This may not be good for casting that requires gradual melting. As the quantity of the used engine oil increases while the kerosene decreases, the intensity of burning gradually decrease while the time of melting increase (Fig 2). At a ratio of 6:1 of used engine oil and kerosene, gradual and effective

Used Engine oil

Diesel Fuel

Kerosene

70

Aji I.S et al: Continental J. Engineering Sciences 3: 64 - 71, 2008 melting occurs even though the time required to melt the material; in this case zinc, increases. Figure 3 shows this gradual but effective melting of sample in relation to proportion of mixtures. Even though used engine oil has a high flash point, its rate of burning is low. This can be attributed the presence of impurities inside.

35

Used engine oil

30

25

20 Diesel oil

Time (Minute) 15

Kerosene

10

5

1/6 1/5 ¼ 1/3 5/2 5/3 3/2 2/1 Proportion of mixture (liters) Fig. 4.2 Proportion of mixture in relation to time of melting CONCLUSION AND RECOMMENDATION From the experiment carried out, it has being observed that kerosene and used engine oil can be used in foundry workshop for firing crucible furnace effectively. For economy in large scale operation, the admixture of used engine oil blended with kerosene at a ratio of 6:1 can be an alternative to these industrial fuels when the used engine oil has been properly treated. That is, removal of un-wanted sediments that may be harmful to castings e.g. sulphur. This kind of foundry workshop can be utilized for the purpose of teaching/training student in our various institution of learning and can help to save cost of running foundry workshop.

71

Aji I.S et al: Continental J. Engineering Sciences 3: 64 - 71, 2008 REFERENCES Lowson M. H., Our Industrial Petroleum. (1970), Published by British Petroleum Company limited, London 4th Edition. Nelson W. L., Petroleum Refinery Engineering 3,434. (4th ed, 1958) London. Clair Richardson Norma St., Mineral Resources and Engineering Geology. (1979), Australia. Sauvain Phillip, Oil and Natural Gas. (1987), Published by Basingstoke, Macmillan; Title series on Exploring Enegry. Timasha A.N., Sakharor V.A,and Sereda N.G. Manual for Oil and Gas Industry. (1989). Published by BLM Manuals and Hand Book, New Delhi. Received for Publication: 14/05/2008 Accepted for Publication: 16/06/2008 Corresponding Author: Aji I.S Department of Mechanical Engineering, University of Maiduguri suleimanaji@yahoo.com

72

Continental J. Engineering Sciences 3: 72 - 79, 2008 ©Wilolud Online Journals, 2008.

POWER MANAGEMENT SCHEME FOR WIRELESS TELEPHONY SERVICE PROVIDERS

Aboaba, A. Abdulfattah1; Amoo, L. Abdullahi2 and Yusuf, Ahmad 3

1Computer Engineering Department, University of Maiduguri, Maiduguri, 2Electrical and Electronic Engineering Programme, Abubakar Tafawa Balewa University, Bauchi, 3Department of Electrical and

Electronics Engineering, Federal Polytechnic, Bauchi

ABSTRACT The relationship between the mobile phone service providers and their service consumers since the about seven years ago when mobile phone became fully integrated into Nigeria society is to say the least rough. Accusations of poor services coupled with high charges are levied against the service providers and in defense the service providers blame it on high running cost especially fuelling and maintenance of generating sets for power supplies. Hence, for mobile phone service providers to provide satisfactory service to their customers, there is need for efficient power management system. This work finds the average power supply per day, cost of the Base Transceiver Station (BTS) generating set, cost of installing the generating set, fuel consumption of the generating set per certain periods based on BTS equipment data provided by one of the service providers, routine maintenance cost of the generating sets, etc and compare these with Photovoltaic (PV) system. The findings reveal that an environmental friendly renewable energy technology, a photovoltaic system is a potent alternative power source especially when life cycle cost (LCC) analysis is invoked and the site management scheme proposed is adopted. PV system has been found to be cost competitive with the conventional system. KEYWORDS: Photovoltaic (PV) array, Balance of system, Life cycle cost (LCC), Cost benefit analysis, PV hang-on, & Site management scheme,

INTRODUCTION Statistics have shown that the wireless mobile telephony is growing tremendously just over one and a half decade of its existence. For instance, in Nigeria there are about 40 million active subscribers to wireless telephony operators by the close of 2007 and Nigerian teledensity stood at 29.98 (NCC, 2008). Nigeria with a population of one hundred and forty million three, thousand five hundred and forty two (140,003,542) in 2006 and at a growth rate of 3.2 percent was about 143,363,627 by the end of 2007. Using the teledensity of about 30 percent, forty three million, nine thousand and eighty eight (43,009,088) people are having access to telephone line as at the stipulated time if we assume one line per person. Thus, it can be projected that with about ten (10) wireless telephony operators in the first quarter of year 2008 and if the rate of penetration remains steady, by the next decade, over 50 individual wireless telephony operators may have emerged. With the BTS radial coverage of about 4.5 kilometers for urban cells and 10 kilometer or higher for rural cells, each wireless telephony operator may have 1000 base transceiver stations (BTS) for adequate and effective coverage, which will aggregate to 50,000 BTS for Nigerian network alone. Moreover, by the present state-of-art owing Nigeria perpetual energy problem, each BTS in most urban areas has at least a dedicated generator while in the rural areas where there is no grid they two dedicated generators approach is usually employed per BTS. Then the fuel consumptions and environmental impact will on the long run become very alarming and prohibitive. Therefore, the call for alternative scheme is inevitable for sustainability of the industry with the view of offering mobile service at reduced cost for the providers and invariably to their customers. History of Wireless Telephony The Global System for Mobile Communications (GSM) is a European digital communications standard which provides full duplex data traffic to any device fitted with GSM capability, such as a phone, fax, or pager, at a rate of 9600 bps using Time Division Multiple Access (TDMA) communications scheme. In the l980s GSM began as an analog cellular telephone system in Europe. Initially, there was problem of equipments incompatibility around European countries where the systems were experiencing rapid growth. The mobile equipments were limited to operation within national boundaries, which in a unified Europe, were increasingly unimportant because an economy of scale was absolutely difficult and substantial saving could not be realized. The Europeans realized this early on, and in 1982 the

73

Aboaba, A. Abdulfattah et al: Continental J. Engineering Sciences 3: 72 - 79, 2008 Conference of European Posts and Telegraphs (CEPT) formed a study group called the “Groupe Special Mobile (GSM)” to study and develop a pan-European public land mobile system. This acronym accidentally coincided with GSM. According to Scourias (1995), commercial service was started in mid-1991, and by 1993 there were 36 GSM networks in 22 countries, with 25 additional countries having already selected or considering GSM. In the beginning of 1994, there were 1.3 million subscribers worldwide. In a span of a year, that is, by the beginning of 1995, there were over 5 million subscribers. By the standardization and advances in digital techniques, the GSM is now purely a digital system. It can easily interface with other digital communications systems such as Integrate Switched data network (ISDN), and digital devices, such as Group 3 facsimile machines. Along the line the American standard of wireless communication using Code Division Multiple Access (CDMA) came into being. For most part, mobile phones require the use of either Subscriber Identity Module (SIM) or User Identity Module (UIM) card. These small electronic devices are approximately the size of a credit card and all of the user information is recorded on it. This includes data such as programmed telephone numbers and network security features, which identify the user. Without this module, the mobile equipment (ME) will not function. This allows for greater security and also greater ease of use as this card may be transported from one phone to another, while maintaining the same information available to the user. Technology Basis of Wireless Telephony The GSM uses a combination of time division multiple access (TDMA) and frequency division multiple access (FDMA) techniques. GSM digitizes and compresses data, then sends it down a channel with two other streams of user data, each in its own time slot. The American standard uses the code division multiple access (CDMA) which is the third of the multiplexing techniques. Wireless telephony is presently operating within three band namely: between 850 MHz to 900 MHz called 900 MHz; 1800 MHz to 1900 MHz called 1800 MHz frequency hands; and 450 MHz to 480 MHz called 450 MHz frequency hands (Telecommunications Research Associates, 2007) & (Starcom, 2008). Architecture of the Wireless Telephony Network A wireless network is composed of several functional entities whose functions and interfaces are specified. The wireless network can be divided into three broad parts. The subscriber carries the Mobile Station. The Base Station Subsystem controls the radio link with the Mobile Station. The Network Subsystem, the main part of which is the Mobile services Switching Center (MSC), performs the switching of calls between the mobile users, and between mobile and fixed network users. The MSC also handles the mobility management operations. Not shown is the Operations and Maintenance Center, which oversees the proper operation and setup of the network. The Mobile Station and the Base Station Subsystem communicate across the Um interface, also known as the air interface or radio link. The Base Station Subsystem communicates with the Mobile services Switching Center across the A interface. Of the wireless telephony network architecture, the part of interest to this paper is the base station subsystem because it is the interface between the subscriber unit (mobile station) and the network subsystem and when it malfunctions the subscriber is cutoff and of course one of the most frequent of the base station subsystem problems is power supply. Base Station Subsystem The Base Station Subsystem is composed of two parts, the Base Transceiver Station (BTS) and the Base Station Controller (BSC). These communicate across the standardized Abis interface, allowing (as in the rest of the system) operation between components made by different suppliers. The Base Transceiver Station houses the radio transceivers that define a cell and handles the radio-link protocols with the Mobile Station. In a large urban area, there will potentially be a large number of BTS deployed, thus the requirements for a BTS are ruggedness, reliability, portability, and minimum cost. The Base Station Controller manages the radio resources for one or more BTS. It handles radio-channel setup, frequency hopping, and handovers. The BSC is the connection between the mobile station and the Mobile service Switching Center (MSC). Powering the Base Station Subsystem Of the wireless telephony architecture, the base station subsystem (BTS & BSC) formed peoples knowledge of the presence or not of wireless telephony in a particular location with only the exception of operators that uses direct satellite link to their subscribers. Depending on which frequency band a

74

Aboaba, A. Abdulfattah et al: Continental J. Engineering Sciences 3: 72 - 79, 2008 BTS and BSC is operating on, which mainly determines the coverage area, the number of BTS and BSC deployed in a geographical entity could be enormous and considering the fact that an average BTS consist of electrical and electronics items like transceiver equipment aviation light ,air-conditioners and other lightening all of these consume a total of about 27 KW of electricity, this of course constitute a drain into our already insufficient and epileptic power supply (Aliyu,1998) and (Somolu,2007). Having understood the Nigerian terrain in terms of poor electricity supply, all the operators design their BTS and BSC to have both connection to grid and diesel generating set(s) and for those BTS sites that are located off grid and those in locations where there is acute power outage , a two diesel generating sets approach is adopted. Taking into consideration the amount of money in excess of normal operation cost the utilization of diesel generating sets had brought on the operators, it thus becomes inevitable that consumers had to pay more for the same service compared to other place with stable electricity. This was exactly the faith of wireless telephone users in Nigeria right from the onset GSM/ Wireless telephony in 2001. While the consumers cry foul, the operators had been defending the reason why high-call-cost should continue perpetually with bogus claims such as the one debunked by Aluko (2004). Apart from high-call-cost that is blamed on high running cost, even poor services is also linked with use of diesel generating set and this could be true if no mischief is intended because generating sets have to be periodically maintained besides, even though seldom, breakdown maintenance. Thus a challenge is thrown to the academic community in Nigeria to channel a way of reducing call-cost and improving the services of the wireless telephony from the angle of, but not limited to, powering the Base Station Subsystem. The Photovoltaic Cell (PVC) Alternative The sun is a nuclear power plant producing all the heat and light experienced on earth by nuclear fusion reactions in the sun’s core .The radiant energy produced by sun is about 3.8 X 1023 kilowatts out of which about 1.8 X 1014KW is intercepted by the earth. Again about 60% of this penetrates the earth’s atmosphere to reach the earth surface. The atmosphere and clouds absorbs or scatter the other 40 percent. However, the total energy receives on earth is fairly constant from year to year with only 0.2% change in 30 years (Microsoft, 2007). Hence, the solar energy alternative to power generation using solar cell or photo voltaic cell (PVC) and balance of systems which has been in use for about 40 years now is instructive. The infamousness of PVC as an alternative energy source to the conventional types was due to some of its odds like cost per watt and space (site size). However, according to renewable energy policy project in the USA (2003), PV module cost has gone down by half from 1991 to 2001 and Foster, et al (1998) said: “PV systems cost decrease significantly on a per watt basis as PV system size is increased”. The assertions above have made the use of PV more popular and acceptable as evident in the works of (Foster, et al (1998) and (Moore, et al, 2003) especially for large projects of the kinds of BTS and BSC. Figure 1 shows in schematic diagram form the PV and the balance of system arrangement. Cost of PV System The capital cost (that is the initial cost) of the PV system typically contains four costs viz: PV array; balance of system; transport and installation; and project management, design and engineering. Generally, the relative contributions of these costs to the total price of an installed system depend on the application, the size of the system and its location. PV technology is on the threshold; costs falling each year invariably make PV commercially mature in many applications where it can compete with higher installation costs of long links to the grid or expensive generation from diesel set (FJC/SIS, 1999). According to Islam (2007) a 125 KW PV installation capacity cost 70 million naira for the PV array at the rate of 4 dollar per watt of PV cell, while its balance of system cost 42 million naira. Cost of Connection to Grid By the present state-of-art, PV generation of energy cannot be compared with conventional systems in terms of capital cost except where connection to grid is above 1.25 miles (Moore, et al, 2003) as in the case of off-grid areas, and in situations of unstable power supply (too-poor-power-supply) where grid connection is combined with the use of diesel generating set. For instance, according to (Mtel, 2007) it costs only 3.6 million for a contractor to purchase and install a 100 KVA transformer to a site and the operator only pays an average of 27,000 naira as monthly consumption of energy even though it is for

75

Aboaba, A. Abdulfattah et al: Continental J. Engineering Sciences 3: 72 - 79, 2008

FIG. 1: SCHEMATIC DIAGRAM of PV ARRAY and BALANCE of SYSTEM ARRANGEMENT. an average of around four (4) hours per day, meaning the operator would have paid only 162,000 naira monthly and 1,944,000 naira annually if supply is for 24 hours. More over, the too-poor-power-supply scenario best describe Nigeria and that is what wireless telephony operators are encountering. Hence, the comparison will be between first; PV versus conventional cum diesel generating set; secondly between PV and diesel generating set as is often the case in off-grid locations. In both cases, varying hours of generator utilization is used to generate many curves. Cost of Installing, Operating and Maintaining Generating Sets The analysis of data from (Mtel, 2007) revealed that it cost 3.6 million naira for a contractor to purchase and install a 27 KVA diesel fuel generating set with a fuel storage capacity of 2000 litres, the generating set consumes 3.5 litres of fuel per hour and for efficient and durability the generating set(s) are made to work for 6 hours at a stretch. More over, after every 250 hours of work minor maintenance is done on the generating set. Also major maintenance is carried out after every 7000 hours of work. Electricity supply is said to be at an average of 3 to 4 hours per day within Maiduguri metropolitan, more than that around Biu area of the state and less than that in the northern part of the state. For the minor maintenance, the following items are used: 10 litres of engine oil, 1 number of oil filter, 1 number of fuel filter, and 1 number of air filter. And finally information shows that diesel is supplied at a contract rate of 115 naira per litre. Data Analysis From the foregoing, in respect of PV cost, using the $4 per watt of PV cell (Renewable energy Policy Project, 2003), and drawing proportionality from Islam (2007) cost of PV array and balance of load given above, and using exchange rate of 120 naira to American dollar (CBN, 2008), the cost of 27 KVA PV array will be 12, 960,000 naira. Hence balance of load will be 7,760,479 naira. Putting transport and installation cost at 1% of PV array cost for large installation, that component of the bill will be 129,600 naira. The forth component of PV lifecycle cost (LCC), that is, (O&M) will be calculated based on (Moore, et al 2003) who said “Operation and Maintenance (O&M) represents the forth component takes 4 percent of the capital cost for small system of 500W and 0.6 percent for a range of PV system providing daily energy of 2 to 10 KWh”. Therefore, O&M will be about 125,000 naira annually, and the PV system would last for 25 years (Renewable energy Policy Project, 2003). Regarding diesel generating set, assuming an average power supply of 6 hours per day based on Mtel (2007), the generating set would work for 18 hours in a day which give the number of generator at two per BTS to guarantee uninterrupted telephone service. Thence, each will work for 9 hours per day, and each will be due for minor maintenance 27.7 days (approximately one month) and major maintenance every 778 days (approximately two years). More so, each generator will consume 31.5 litres per day

SOLAR ARRAY

BLOCKING DIODE

VO

LTA

GE

R

EG

ULA

TO

R

LOAD

FUSE

STORAGE BATTERY

76

Aboaba, A. Abdulfattah et al: Continental J. Engineering Sciences 3: 72 - 79, 2008 making a total of 63 litres daily. To make the determination of lifecycle cost (LCC) easy, we estimate N10,000.00 per minor maintenance and 100,000.00 for major maintenance. And finally according to (Moore, et al 2003). Lifecycle Cost (LCC) Analysis of PV, Grid and Generating Set From information regarding cost of PV, grid and generating set, table 1 is drawn for easy comparison for 27 KVA of PV and Generating set and 100 KVA distribution transformer. TABLE 1: SUMMARY OF LIFECYCLE COST (LCC) OF PV, GRID & DIESEL GENERATOR

Photovoltaic Grid Generating Set

PV array: N12,960,000 Installation of Distribution Xformer: N3,600,00

Installation of generator: N3,600,000

Balance of System: N7,760,479 Monthly Bill in 1 year: N324,000

Cost of monthly fuel consumption: N108,675

Transport and installation: N129,600

Cost of annual maintenance: N10,000

Cost of annual maintenance: N120,000

Total: N20,850,079

Cost of biennial maintenance: N100,000

Operation and Maintenance per annum: N125,100

DISCUSSION OF RESULTS Based on data from table 1 four LCC curves were plotted each depicting different combination of PV, grid and generator. The plot of figure 2 is the best situation in which PV is compared with the combination of grid and generator supplies with grid supplying for 18 hours and generator for 6 hours. Figure 3 represent the next best situation where both grid and generator supply for 12 hours each, and only one generator is used. This is followed by the most common situation in Nigeria where grid only supplies for 6 hours and generator for 18 hours and of course, two generators are used. Lastly is the off-grid situation in which two generators are employed.

PV Vs Grid cum Generator (Grid 18 Hrs & Gen 6 Hrs)

05,000,000

10,000,00015,000,00020,000,00025,000,00030,000,00035,000,00040,000,000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

Year

Am

ou

nt

PV System Grid & Generator

FIG. 2: LCC CURVE FOR PV VERSUS GRID CUM DIESEL GENERATOR (GRID 18 HRS. & GENERATOR 6 HRS.) Both numerical and graphical results show that even in the best possible situation in Nigeria, PV system is still better in the long run as PV system balance up with grid cum generating set before the fifteenth year.

77

Aboaba, A. Abdulfattah et al: Continental J. Engineering Sciences 3: 72 - 79, 2008

PV Vs Grid cum Generator (Grid 12 Hrs & Gen 12 Hrs)

0

10,000,000

20,000,000

30,000,000

40,000,000

50,000,000

60,000,000

70,000,000

1 3 5 7 9 11 13 15 17 19 21 23 25

Year

Am

ou

nt

PV System

Grid & Generator

FIG. 3: LCC CURVE FOR PV VERSUS GRID CUM DIESEL GENERATOR (GRID 12 HRS. & GENERATOR 12 HRS.) In this situation where one generator is used to generate for 12 hours and grid supply is also 12 hours PV system was able to catch only within eight years.

PV Vs Grid cum Generator (Grid 6 Hrs & Gen 18 Hrs)

0

20,000,000

40,000,000

60,000,000

80,000,000

100,000,000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

Year

Am

ou

nt

PV System Grid &Generator

FIG. 4: LCC CURVE FOR PV VERSUS GRID CUM DIESEL GENERATOR (GRID 6 HRS. & GENERATOR 18 HRS.) The LCC curve of figure 4 is the ideal situation for Nigeria and as can be seen PV system is proved better just before five years.

PV Vs 2 Generator

0

20,000,000

40,000,000

60,000,000

80,000,000

100,000,000

120,000,000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

Year

Am

ou

nt

PV System Generator Only (2/ site)

FIG. 5: LCC CURVE FOR PV VERSUS 2 SET OF DIESEL GENERATORS The last scenario is the rural or off-grid situation where two generators work for 12 hours each per day, again PV system demonstrates it economic advantage. Tackling Site Size At this juncture, the only problem that may militate against the use of PV system especially for BTS and BSC sites located in urban areas is the space requirement of PV array. This problem could be solved if PV cells could be arranged on the station’s mast as shown in figure 6, and using ideas from “Life Cycle Design Research” the whole mast structure could be examined to see if it could be made of PV material.

78

Aboaba, A. Abdulfattah et al: Continental J. Engineering Sciences 3: 72 - 79, 2008

FIG. 6: PROPOSED MODEL OF THE MAST WITH PV CELL HANG-ON SUMMARY The LCC curves of figures 2 to 5 have shown that PV alternative is better for BTS and BSC supply at all times. First, it catches up with the best of situation in Nigeria within fifteen years, the second best situation within eight years, Nigerian ideal situation within six years, and the off-grid situation within five years. More so, the proposed site plan makes it unnecessary to expand the present BTS/ BSC sites size for arrangement of PV array. CONCLUSION From the foregoing, LCC results have shown that the used of PV cell as a sole alternative power supply to BTS and BSC is economically viable over a period of time than diesel generating set or combination of generator and conventional supply. The only exception is when conventional method can deliver electricity supply for 24 hours uninterrupted, effectively and for a long period of time. More so, when the “Cost Benefit Analysis” is done, the use of PV and indeed renewable energy will be seen to be far superior to conventional methods. In addition to that, the use of mast to hang PV cells makes the idea plausible. RECOMMENDATIONS Having seen the results above, it is recommended that the managements of wireless telephony firms should quickly embrace the PV alternative proposed in this paper. Furthermore, the Nigerian government should sponsor more research into non-conventional methods of electricity generation to address the country’s acute power supply problems.

REFERENCES Aliyu, U.O. (1998). Some though on Nigerian energy demeand outlook into the next century: Prospects, problem and R & D directions. 8th inaugural lecture series, Abubakar Tafawa Balewa University, Bauchi. Aluko, M. (2004). GSM: Cutting cost of power generation, The Punch, Tuesday 13 January, 2004. P. 16 Central Bank of Nigeria, (2008). www.cenbank. Org. ng/ FJC/SIS, (1999). Photovoltaics: Cost and economics, FJC/SIS www.fjc/sis.org Foster, R., Cisneros, G., & Hanley, C. (1998). Lifecycle cost analysis for photovoltaic water pumping systems in Mexico, 2nd World conference on photovoltaic solar energy conversion, 6 – 10 July, Vienna, Austria.

79

Aboaba, A. Abdulfattah et al: Continental J. Engineering Sciences 3: 72 - 79, 2008 Islam, M. S. (2007). Assessment of electricity supply for critical load, Ph D seminar, Abubakar Tafawa Balewa University, Bauchi. Microsoft, (2007). Microsoft Inc, Microsoft Encarta. GSM Moore, L. M., Malczynski, L. A., Strachan, J. W., & Post, H. N. (2003). Lifecycle cost assessment of fielded photovoltaic systems, Sandia National Laboratories, NCPV and Solar Program Review Meeting, USA Mtel PLC Maiduguri Office, (2007). Title, place of publication etc National Communication Commission (NCC), (2008). www.ncc.org.ng/ Renewable Energy Policy Project in the USA (2003). Cost benefit analysis for photovoltaic program: A case study of Arizona, USA. www.repol.org/arizona Scourias, J. (1995). Overview of global system for mobile communications, waterloo, University of waterloo. USA. Somolu, F.A. (2006). The yesterday, today and the future of power system engineering in Nigeria….so that Nigeria may have electricity. The Nigerian Society of Engineers’ October lecture, 6th October 2006, National Engineering Centre, Victoria Island, Lagos Nigeria. Starcom Nig. Ltd. Maiduguri Office, (2008). Title, place of publication etc Telecommunications Research Associates. (2007). Understanding the basics of wireless communications. Kansas (USA). Telecommunications Research Associates (TRA) LLC. http://www.tra.com Received for Publication: 24/04/2008 Accepted for Publication: 16/06/2008 Corresponding Author: Aboaba, A. Abdulfattah Computer Engineering Department, University of Maiduguri, Maiduguri, Bornu State. adeabdul2002@yahoo.co.uk