Extraction of Alumina from Coal Fly Ash

Fly Ash

Aluminum

Fly AshFly ash, also known as flue-ash, is one of the residues generated in combustion, and comprises the fine particles that rise with the flue gases. Ash which does not rise is termed bottom ash. In an industrial context, fly ash usually refers to ash produced during combustion of coal.

Fly ash is one of the residues created during the combustion of coal in coal-fired power plants.

Fine particles rise with flue gasses and are collected with filter bags or electrostatic precipitators

Fly ash is a waste by-product material that must be disposed of or recycled

Nearly 75.49 Million tons of fly ash was produced in India in 2013.

Production

Production Process

Fly Ash Utilization in the India .

Table 2 exaplain the utilization of fly ash in India

Fly Ash Utilization in India Since 1996-97 to 2010-11 increase in fly-ashproduction is observed so the consumption (9.63 % in 1996-97 to 54.53 % in 2011-12, (Central Electricity Authority 2011-12)).India achieved utilization of 63percentages, a highest level of fly-ash utilization in 2009-10 and only 54.33 percentages in 2012-13.In India the utilization of fly ash is very less There is no recovery of chemical compounds like aluminum , silicon Ect. In INDIA

Class F Fly Ash 200x mag.

Fly ash Bulk fly ash

Because fly ash is a by-product material chemical constituents can vary considerably but all fly includes:Silicon Dioxide (SiO2) Calcium Oxide (CaO) also known as Lime Iron (III) Oxide (FeO2)Aluminum Oxide (Al2O3)

Depending on source coal may include on or more toxic chemicals in trace amounts:Arsenic, Beryllium, Boron, Cadmium, Chromium, Cobalt,

Lead, Manganese, Mercury, Molybdenum, Selenium, Strontium, Thallium, and Vanadium.

T he major compounds in fly ash 1 are SiO.sub.2 approximately 40% and AL.sub.2 O.sub.3 approximately 31%

Chemical Composition

Fly ash analysis

Extraction of Alumina from Coal Fly AshThis invention relates generally to metallurgical processes, and more particularly to a process for the recovery of alumina from fly ash.It has been known for many years that the fly ash from coal burning power plants contained relatively high amounts of alumina; on the order of thirty percent by weight of the fly ash being alumina

The area of research that is called 'High Technology Ash Application' in the United States . This research focuses on the development of technologies for ash processingwith recovery of valuable minerals and metals in particular for the recovery of aluminum.

The recovery of aluminum, iron and silica from coal ash, produced by utilities. Alkaline technologies for coal fly ash processing were developed that made it possible to separate the main components of fly ash (SiO, , AI,O,,Fe,O,) and utilizethem separately, producing a large variety of useful products. Some of these technologies have already been successfully tested in pilot programs.

PROCESSThe process for recovery of alumina from fly ash by mixing a prescribed amount of CaO or the equivalent amount of Ca(OH).sub.2 for the amount alumina in the dry fly ash, and utilizing a steam treatment at 80 C., then dissolving in nitric acid for one hour, followed by filtration and precipition with ammonia. SZEPESI reports that 95% of the Al.sub.2 O.sub.3 content of the fly ash can be obtained as iron free alumina.

EXPERIMENTALChemical and Mineralogical Description of Ash SamplesChemical analysis of typical fly ash derived from Ekibastuz coal are given in Table 3

Extraction of Alumina from Coal Fly Ash with Sulfuric Acid Leaching Method by

Materials and Reagents

Experimental and Analytical Instruments

Methodology

Extraction of Alumina from Coal Fly Ash with Sulfuric Acid Leaching Method Materials and ReagentsThe main composition of CFA is given in Table 4.The concentrated sulfuric acid and caustic soda are in technical purity. Redistilled water is used in theexperiments. The other reagents are in analytical purity.

Experimental and Analytical InstrumentsA 4-mouth flask and heating jacket (2NHW-1000 mL with precision of ±1 ) were used in ℃acid leaching experiments. The phase composition and microstructure of samples were analyzed by XRD (D/max-2500PC, Rigaku, Japan) and SEM (SSX-550, Shimadzu, Japan). Their thermogravimetric change and weight loss were determined by SDT 2960 Simultaneous DSC−TGA (TA Instruments, USA).

Methodology1. The CFA sample pulverized by mechanical method and

concentrated sulfuric acid were put into the 4-mouth flask in proportion, heated with the heating jacket and agitated with an agitator The aluminum sulfate was dissolved by hot water and separated from the acid leaching residue with filtration.

2. The optimum conditions of acid leaching process were determined through single factor and orthogonal experiments.

3. The CFA, intermediate product (aluminum sulfate), γ-Al2O3 and α-Al2O3 were identified by XRD. The main components, including alumina, silicon oxide, ferric oxide, in CFA and the residue of acidl eaching were detected with XRF device. Contents of Al, Si and Fe in solutions were detected with chemical analysis methods

Using the entire processes, virtually all of the alumina 40 is recoverable from the non-magnetic fraction 4 and the resultant alumina 40 is very pure. Even so, without the magnetic separation 2, recovery of 99.4% of the alumina 40 in the fly ash resulted, and the alumina 40 was of very high purity with but only trace amounts of impurities.

Some of the many uses for aluminium metal are in:Transportation (automobiles, aircraft, trucks, railway cars, marine vessels, bicycles, etc.) as sheet, tube, castings, etc.Packaging (cans, foil, frame of etc.)Construction (windows, doors siding, building wire, etc.).[43]

A wide range of household items, from cooking utensils to baseball bats, watches.[44]

Street lighting poles, sailing ship masts, walking poles etc.Outer shells of consumer electronics, also cases for equipment e.g. photographic equipment, MacBook Pro's casingElectrical transmission lines for power distribution

RESULTSBy recovering aluminum from Fly ash we can reduced pollutions

Many uses from aluminium metal

Portland Cement and GroutBrick and CMUEmbankment/ Structural Fill and Mine ReclamationRoad SubbaseSoil StabilizationFlowable Fills (CLSM)Waste Stabilization and SolidificationRaw Feed for Cement ClinkersAggregateAshphaltic Concrete Mineral FillerNumerous Agricultural Applications

Other uses of fly ash

Fly Ash Utilization for various perposs

Fly ash offers several advantages over soil fills Lower unit weight reduces dead loads

and induced settlement of sub-soilHigh shear strength compared with its

low unit weight for good bearing support

Ease of placement and compaction can reduce construction time and cost

DisadvantagesDust control measures may be neededFly ash is subject to erosion which must be

accounted for• Lot of pollution

Pros Reduces green house gas emission as a cement

replacement materialFor every one ton of cement produced about 6.5

million BTUs of energy is consumed. Replacing that 1 ton of cement with fly ash would save enough electricity to power the average American home for almost a month.

For every one ton of cement produced about one ton of carbon dioxide is released.

Reduces volume of landfill space used for disposal of fly ash

Environmental Impacts

ConsPossibility of leaching toxic substances in into

soil, water, atmosphere.EPA has proven that heavy metals have been leached

from fly ash into ground water and underground aquifers in 39 locations in the U.S.

The extent of leaching and hazardousness to humans of fly ash leachate is still unclear but the EPA is investigating it currently

Large ruptures of fly ash ponds, dams, or retention walls can cause catastrophic environmental damage to ecosystems and contaminate large areas with toxic substances.

Environmental Impacts

MAKING OCEANS AS SHINK WITH FLY ASH

TVA Coal Ash Pond Rupture- 2008

CONCLUSIONS(1) The metallurgy alumina was prepared by concentrated sulfuric acid leaching of CFA.(2) The feasibility of acid leaching process was demonstrated with thermodynamic calculation.(3) The optimum conditions of acid leaching process of CFA were obtained through experiments, they were the temperature of 200∼210℃, leaching time of 80 min, volumetric ratio of acid to CFA of 5:1 and stirring speed of 300 r/min. The extraction rate of Al2O3 could be stabilized at about 87% under these conditions.(4) The kinetic equations of leaching process were obtained with irreversible thermodynamics, in the prior stage (before 40 min) the reaction was controlled by both internal diffusion and interface-chemical reaction, but in the later stage (after 40 min) the reaction controlled by interface-chemical reaction.

http://www.flyash.com/ http://www.epa.goCARE Journal of Applied Research (ISSN 2321-4090) References

[1] Mahendra.K.V and Radhakrishna. K, Castable composites and their application in automobiles, Proc. IMechE Vol. 221 Part D: J. Automobile Engineering, (2007): pp. 135-140

[2] Mohanty Samrat, Chugh Y.P., Development of fly ash-based automotive brake lining, Tribology International 40 (2007): pp. 1217–1222

[3] Rohatgi P.K,Weiss D, and Gupta Nikhil, Applications of Fly Ash in Synthesizing Low-Cost MMCs for Automotive and Other Applications, Journal of the Minerals, Metals and Materials Society, vol 58,(2006): pp 71-76

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References

4] Sarkar S., Sen S. and Mishra S. C, Aluminum – fly ash composite produced by impeller mixing, Journal of reinforced plastics and composites,(2008):pp 1-6

[5] William D. Callister, Jr., Materials Science and Engineering-Materials Science and Engineering-An Introduction. Asia, John Wiley & Sons, 2001

[6] Rizam. S.S. Hafizal.Y, Effect of particle coating on matrix-reinforcement bonding, IcoSM (2007): pp174-177

[7] Sarkar S Mohan S, Panigrahi S.C, Effect of particle distribution on the properties of aluminum matrix in-situparticulate composites, Journal of reinforced plastics and composites, vol. 27(2008):pp 1177-1187 [8] Radhakrishna M. Ramachandra K., Effect of reinforcement of flyash on sliding wear, slurry erosive wear and corrosive behavior of aluminium matrix composite, Wear 262 (2007): pp1450–1462.