4. What is fly ash ?
Fly ash is one of the coal combustion product composed of fine
particles
Ash that falls in the bottom of the boiler is called bottom ash .
Fly ash is also known as pulverized fuel.
5. Components of fly ash.
Depending upon the source and makeup of coal components of fly
ash vary considerably but fly ash include substantial amount of SiO2,
Al2O3 and CaO.
6. Applications of fly ash.
• Desulphurization
• Geo polymer
• Ceramics
• Concerete
• Waste water treatment
7. Desulphurization by using fly ash absorbents
Introduction
Mechanism
• Preparation of absorbent
• Working
• Factors effecting aborbent.
• Results
8. Introduction
• Coal burning pollution is the primary form of air pollution .
• The major component of coal burning pollution is SO2.
• SO2 emission has deleterious effects on human health, plants, and
animals.
• To reduce the emission of SO2, flue gas desulphurization (FGD)
process utilizing absorbent synthesized from mixture of coal fly ash is
used widely.
9. Preparation of absorbent.
• For the preparation of absorbent, CaO was added to distilled water at
90 degree. Coal fly ash and CaSO4 were then added to the slurry
simultaneously. The slurry was heated upto 95 degree and
maintained at the temprature for 10hrs for hydration process to
occur.
10. • The resulting slurry was then filtered and dried at 200 degree for 2hr
producing dry powder type absorbent.
• The powder type absorbent were then palletized, crushed and sieved
to produce particle size.
11. Working
• Desulphurization experiments were performed using fixed bed
reactor. The absorbent was packed in the center of reactor supported
by glass wool.
• A stream of feed gaseous mixture containing SO2, NO, CO2, O2 and
balance nitrogen was passed through the absorbent.
12.
13. • The N2 gas stream was humidified using a humidified system.
• The concentration of SO2 in the flue gas was measured using
portable flue gas Analyzer before and after absorption process.
14. Factors effecting absorbent.
• Effect of absorbent particle size.
• Effect of temperature.
• Effect of relative humidity
• Effect of feed concentration of SO2.
15. Effect of absorbent particle size.
• Flue gas desulphurization utilizing absorbent synthesized from coal
fly ash involved solid gas reaction between absorbent and SO2.
• In a solid gas reaction absorbent particle size play important role.
• When the particle size increases the desulphurization capacity of
absorbent decreases.
16.
17. Effect of temperature.
• When the temperature was increased a modest increase in the
absorbent ability for SO2 removal was observed.
18.
19. Effect of relative humidity
• When the relative humidity increases the desulphurization rate
increases.
• This is due to the water sorption on the absorbent surface which
increases the formation of active species Ca+2, OH-, and SO3.
• The presence of these ions promote the reaction between absorbent
and SO2.
20.
21.
22. Effect of feed concentration of SO2
• The absorbent capacity of absorbing SO2 decreases with increasing
feed concentration of SO2.
• At higher feed concentration of SO2 the number of SO2 molecule
available for absorption will also be high causing limitation of total
active sites capable of absorption.
23. Results
• The desulphurization capacity of absorbent increases with higher
humidity but with decreasing SO2 inlet concentration and particle
size.
• The reaction temperature has negligible effect on desulphurization
activity.
24. Limitations of fly ash
• Advantages of fly ash overweigh the disadvantages.
• Radioactive materials present in fly ash produce radioactive.
• The fly ash from coal combustion disperse in atmosphere causes
health risks.
25. Conclusion
• As are many disadvantages of fly ash but fly ash is also used for many
useful purposes.
