Fuels in Solid, Liquid & Gaseous State

Introduction

Solid Liquid Gaseous

Coals Cokes BriquettesSolid pitch

Gasoline Kerosene DieselFuel oilsCoal tar fuelsTar

Natural GasLPGBlast furnace gas Coke oven gas Producer gasCoal gas

Factors involve in the selection of fuelsNumber of factors are to be considered

when fuel is chosen for a particular purpose.The main factors are: The type of heating w. r. t. size or whether a continuous

or intermittent (irregular) operation is involved. The availability and reliability of supply of fuels. The price of the fuel delivered to the place where it is

required, as some fuels need storage and feeding equipment.

The efficiency of the heating operation with selected fuels.

Cont… The ratio of the cost of heating operation to the cost of the

finished product. If the ratio is low then a high grade expensive fuel need to be considered.

The adverse effect of fuel on the quantity/quality of finished product.

Adequate storage space for the fuels should be available. The degree of closed technical control necessary to ensure a

high quality of finished product. The clean and hygiene of working conditions The fuel chosen should achieve smokeless combustion

Solid Fuels

Coal It is a readily combustible black or brownish-black sedimentary

rock. It is composed primarily of carbon along with variable quantities of

other elements, chiefly sulfur, hydrogen, oxygen and nitrogen. Coal was formed from plant remains that were protected by water

and mud against oxidization and biodegradation, thus trapping atmospheric carbon in the ground.

Over time, the chemical and physical properties of the remains were changed by geological action to create a solid material.

Coal, a fossil fuel, is the largest source of energy for the generation of electricity worldwide, as well as one of the largest worldwide source of carbon dioxide emissions.

Types of Coal Peat, considered to be a precursor of coal, has industrial

importance as a fuel in some regions, for example, Ireland and Finland.

Lignite, also referred to as brown coal, is the lowest rank of coal and used almost exclusively as fuel for electric power generation.

Sub-bituminous coal, whose properties range from those of lignite to those of bituminous coal and are used primarily as fuel for steam-electric power generation.

Bituminous coal, dense mineral, black but sometimes dark brown, used primarily as fuel in steam-electric power generation, with substantial quantities also used for heat and power applications in manufacturing and to make coke.

Anthracite, the highest rank; a harder, glossy, black coal used primarily for residential and commercial space heating.

Graphite, technically the highest rank, but difficult to ignite and is not so commonly used as fuel: it is mostly used in pencils and, when powdered, as a lubricant.

Solid fuels

Coke Coke is a solid carbonaceous residue derived from low-ash, low-

sulfur bituminous coal from which the volatile constituents are driven off by baking in an oven without oxygen at temperatures as high as 1,000 °C (1,832 °F) so that the fixed carbon and residual ash are fused together.

Metallurgical coke is used as a fuel and as a reducing agent in smelting iron ore in a blast furnace. The product is too rich in dissolved carbon, and must be treated further to make steel

Cont…Briquettes A briquette (or briquet) is a

block of flammable matter which is used as fuel to start and maintain a fire.

Common types of briquettes are charcoal briquettes and biomass briquettes.

Some briquettes are compressed and dried brown coal extruded into hard blocks. This is a common technique for low rank coals.

They are typically dried to 12-18% moisture, and are primarily used in household and industry.

Cont…

Solid pitch Pitch is the name for any of a

number of highly viscous liquids which appear solid. Pitch can be made from petroleum products.

Pitch was traditionally used to help the seams of wooden sailing vessels

It was heated, Pitch was also used to waterproof wooden containers, and is sometimes still used in the making of torches.

It is black in color, hence the adjectival phrase, "pitch-black".

Properties and testing of CoalProximate analysis of Coal

Determination of moisture, volatile matter,

ash and fixed carbon in coal comprises its

proximate analysis.

Determination of moisture content in coal

% Moisture in Coal =

Loss in weight of coal/ wt of coal in initially taken*100

Cont…

Determination of volatile matter It is the loss in weight of moisture free

powdered coal when heated in a crucible fitted with cover in a muffle furnace at 950 degree C for 7 minutes.

% Volatile Matter =

Loss in weight of moisture free coal/ Wt of moisture free coal * 100

Cont…

Determination of ash in coal It is the weight of residue obtained after burning a weighed

quantity of coal in open crucible (i.e. in presence of air) at 750 degree C in a muffle furnace.

% Ash in Coal =

Wt of residue ash formed / wt of coal initially taken * 100

Modern Theory

According to the this theory petroleum is formed by the decay and decomposition of marine animals as well as the vegetable organism of the pre historic forests.

Due to action of prolonged action of high temperature and pressure in the interior of the earth, the biological matter decomposed into the petroleum.

Cont…

This theory explain the following facts: Presence of brine & Coal in the vicinity of the

petroleum. Presence of N & S compounds. Presence of chlorophyll & optically active

compounds.

How to get Petroleum Product?

Gasoline

Gasoline is the most widely used liquid fuel. Gasoline, as it is known in United States and

Canada, or petrol in India, Britain, Australia, New Zealand, South Africa and many English speaking countries, is made of hydrocarbon molecules forming aliphatic compounds, or chains of carbons with hydrogen atoms attached.

Production of gasoline is achieved by distillation of crude oil at the temperature of 30 - 200oC

Kerosene

Kerosene once used in kerosene lamps as an alternative to whale oil, is today mainly used in fuel for jet engines (more technically Avtur, Jet A, Jet A-1, Jet B, JP-4, JP-5, JP-7 or JP-8).

One form of the fuel known as RP-1 is burned with liquid oxygen as rocket fuel.

Kerosene is sometimes used as an additive in diesel fuel to prevent gelling or waxing in cold temperatures.

Kerosene is obtain at the temperature of 140 – 290oC

Diesel

Diesel is similar to gasoline in that it is a mixture of aliphatic hydrocarbons extracted from petroleum.

Diesel may cost more or less than gasoline, but generally costs less to produce because the extraction processes used are simpler.

Diesel is obtain at the temperature of 140 – 300oC

Properties of Petroleum Product

Flash point Fire point Cloud point Pour point Smoke point Aniline point

Flash Point

According to ASTM, which first standardized the test in 1924, the flash point is the lowest temperature at which an ignition source causes the vapors of the specimen to ignite under specified conditions.

Flash point gives the idea about: Nature of boiling point diagram Amount of low boiling point fraction present in the liquid fuel Explosion hazardous Volatility of liquid fuels

Fire Point

It is the lowest temperature at which vapors given off by oil ignites and continues to burn for at least 5 seconds.

The fire-point, the test is continued until the application of the test flame causes the test specimen to ignite and sustain burning for a minimum of 5s.

In most cases the fire point is 5 - 40oC higher than flash pointIt gives the idea about: Fire hazards during storage Use of oil

Cloud Point

The temperature at which oil becomes cloudy or hazy is called cloud point.

This haziness is due to the separation of crystals of wax or increase of viscosity at low temperature.

Pour Point

The temperature at which the oil just ceases to flow is called pour point.

It determines the temperature below which, an oil can not be use as lubricant.

Smoke Point

Smoke point is an indicator of the combustion qualities of aviation turbine fuels and kerosene.The fuel sample is burned in the Smoke Point Lamp, and the maximum flame height obtainable without smoking is measured.

Aniline Point

Aniline point is defined as the temperature at which equal volumes of aniline and diesel oil are completely miscible.

The value gives an indication of the aromatic content of diesel oil, since aniline is an aromatic compound which is dissolved on heating by the aromatics in diesel oil.

Diesel Index

An alternative method of expressing the quality of diesel oil by the use of the diesel index . It is given by

DIESEL INDEX = (ANILINE POINT of) (API GRAVITY))/100

Calorific Value

It is defined as the quantity of heat librated by the combustion of unit quantity of fuel.

There are two types of calorific value Higher gross CV Lower or net CV

Higher or Gross C.V. It is defined as the total amount of heat librated

when one unit of fuel is burnt completely and the combustion products are cooled to room temperature.

Lower or net C.V. It is defined as the amount of heat librated when one

unit of the fuel is burnt completely and the combustion product are allowed to escape.

Advantages of Liquid fuels

It can be stored more compactly than solid fuels.

It occupies much less space for equal heating output.

It can handle easily with little labor. It has no ash and clinkering problems. It is not liable to spontaneous combustion

and deterioration during storage. It can be used in I.C. engine.

Disadvantages of liquid fuel

Special provision for storage in the way of tanks, heaters, lagging and pipelines is to be made.

Sulphur content in the most of the petroleum oils is high compared to coal .

Vanadium compound present on oils form corrosive deposits on the hot pressure parts of boilers.

Gaseous Fuels

Gaseous fuels are those which are burnt is gaseous state in air or oxygen to give heat or utilization in domestic/commercial sector.

Natural gas

Natural gas is a hydrocarbon, which means it is made up of compounds of hydrogen and carbon.

The simplest hydrocarbon is methane; it contains one carbon atom and four hydrogen atoms.

Cont…

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Natural gas can be found by itself or in association with oil. It is both colorless and odorless and is in fact a mixture of hydrocarbons.

While mainly methane, the other hydrocarbons include ethane, propane, and butane.

Water, oil, Sulphur, carbon dioxide, nitrogen, and other impurities may be mixed with the gas when it comes out of the ground.

These impurities are removed before the natural gas is delivered to our homes and businesses.

Cont…

Natural gas can be measured in a variety of ways, although the most common unit of measurement is the Giga joule (GJ), which signifies one billion joules, the metric measure for heat or energy. Other measures are Mcf (thousand cubic feet) and Btu (British Thermal Unit).

Natural Gas - Sources

Natural gas is a fossil fuel. This means it originates from the remains of plants and animals that lived many millions of years ago.

These organisms were buried and exposed to heat as a result of being highly compressed underneath thousands of metres of soil and rock.

These forces transformed the once living organisms into natural gas.

Natural Gas - Transportation

The transportation of natural gas from a gas well to our homes and businesses requires an extensive network of interconnected pipelines, designed to move natural gas quickly and effectively, sometimes over great distances.

The pipeline system moves the natural gas from the point of origin to areas of high consumer demand.

There are essentially three main types of transportation pipelines:

Gathering pipelines, Transmission pipelines, Distribution pipelines.

Gathering pipelines transport raw natural gas directly from the wellhead to the gas processing plant.

The highly pressurized natural gas is gathered into increasingly larger pipelines, almost always underground, until it reaches the large transmission pipelines where it is often transported over large distances.

The gas flows into a low-pressure distribution system. As a safety precaution, utility companies add an odorant to the gas (so we can smell it in the unlikely event of a leak) and then send it to us through a network of smaller pipelines.

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Liquefied Petroleum Gas (LPG)

Liquefied petroleum gas (also called LPG, GPL, LP Gas, or autogas) is a mixture of hydrocarbon gases used as a fuel in heating appliances and vehicles, and increasingly replacing chlorofluorocarbons as an aerosol propellant and a refrigerant to reduce damage to the ozone layer.

It is prepared by the wet natural gas and gases.

Uses

As motor fuel As refrigerant As cooking fuel

Producer Gas

The mixture of flammable gases (principally carbon monoxide and hydrogen) and nonflammable gases (mainly nitrogen and carbon dioxide) made by the partial combustion of carbonaceous substances, usually coal, in an atmosphere of air and steam.

A combustible mixture of nitrogen, carbon monoxide, and hydrogen, generated by passing air with steam over burning coke or coal in a furnace and used as fuel.

Producer gas has lower heating value than other gaseous fuels, but it can be manufactured with relatively simple equipment; it is used mainly as a fuel in large industrial furnaces.

Composition of producer gas

Constituents Volume%

CO 20 – 30

H2 11 – 20

CO2 4 – 6

N2 46 – 55

CH4 0 – 3

Fuels for producer gasmanufacturing Producer gas can be made form practically

any solid fuel: Wood Waste Peat Coals of all ranks Coke

Cont…

Nature of fuel High volatile bituminous coal gives a richer gas

containing small proportion of methane. Tar vapors also enriches the gas when is used hot. Coke gives a gas free of tar vapor.

Operating temperature Low temperature favors high production of CO2.

High temperature favors high production of CO.

Cont…

Effect of steam Water in the coal feed or steam in air blast

increase the proportion of H2 and CO in the gas. If steam is not added there are chance of clinker formation.

Impurities in Producer Gas

Steam: Lower the flame temperature. Tar: Increase the flame temperature Dust: It would foul and choke the gas mains Sulphur: It can cause corrosion & pollution Ammonia: It cause the endothermic water

gas reaction.

Uses

It is used as fuel in furnace. It is used as the source of hydrogen for the

synthesis in fertilizer plants.

Blast Furnace Gas

Blast furnace gas is a by-product of blast furnaces that is generated when the iron ore is reduced with coke to metallic iron.

Composition of B.F. Gas

Properties & Uses of B.F. Gas

Properties It is very poisonous gas due to the presence of CO. B.F. gas pipes and vessels should be leak proof. Under some conditions mixture of gas and air forms

an explosive mixture which explodes when coming in contract with any source of fire.

Uses Boilers Foundry ovens

Coke Oven Gas

It is produced during high temperature carbonization of coal. It is the most important fuel in an integrated steel plants.

In a by-product coke oven the evolved coke oven gas leaves the coke oven chambers at high temperatures approaching 2000oF.

This hot gas is immediately quenched by direct contact with a spray of aqueous liquor.

The resulting cooled gas is water saturated and has a temperature of 176oF.

This gas is collected in the coke oven battery gas collecting main.

Composition of Coke Oven Gas

Factors Effecting Composition ofCoke Oven GasEffect of temperature With increase in the temperature of carbonization ,

hydrogen content of the coke oven gas increase because of cracking of hydro carbons.

Effect of time With increase in the time of carbonization at a given

temperature, the hydrogen and the hydrocarbons content decreases resulting in the greatly reduced C.V. of the gas.

Advantages of Gaseous Fuels

It has no ash or clinker trouble. Burning is quite clean without any smoke.

It is easier to maintain oxidizing or reduction atmosphere inside the furnace with gaseous fuels.

Gaseous fuel may be prepared at a central place and distributed over wide area through pipelines.

Disadvantages

Some gaseous fuels are highly poisonous and explosive in nature; hence careful handling and utilization is needed.