25-08-2017, 09:32 PM
Fly ash is one of the numerous substances that cause air, water and soil pollution, disrupt ecological cycles and set offenvironmental hazards. The combustion of powdered coal in thermal power plants produces fly ash.The high temperature of burning coal turns the clay minerals present in the coal powder into fused fine particles mainly comprising aluminium silicate. Fly ash produced thus possesses both ceramic and pozzolanic properties. When pulverised coal is burnt to generate heat, the residue contains 80 percent fly ash and 20 percent bottom ash. The ash is carried away by flue gas collected at economiser, air pre-heater and ESP hoppers. Clinker type ash collected inthe water-impounded hopper below the boilers is called bottom ash. The World Bank has cautioned India that by 2015,disposal of coal ash would require 1000 square kilometres or one square metre of land per person. Since coal currently accounts for 70 per cent of power production in the country, the Bank has highlighted the need for new and innovative methods for reducing impacts on the environment. The process of c
HOW FLY ASH IS HAZARDOUS?
Fly ash is a very fine powder and tends to travel far in the air. When not properly disposed, it is known to pollute air and water, and causes respiratory problems when inhaled.When it settles on leaves and crops in fields around the power plant, it lowers the yield. The conventional method used to dispose of both fly ash and bottom ash is to convert them into slurry for impounding in ash ponds around the thermal plants. This
method entails long-term problems.
MIXING OF FLY Ash
3.4.6 PHYSICAL PROPERTIES OF FLY ASH
The physical properties of the pond ash sample which were determined are presented in Table No.4 given below.
Table No.4 Physical properties of fly ash
S No.
Parameter
Value
1.
Specific Gravity(G)
2.10
2.
Plasticity
Non Plastic
3.
Maximum Dry Density (kN/m3)
11.01 kN/m3
4.
Optimum Moisture Content(%)
27.4%
5.
Angle of internal friction(f)
33o
6.
Cohesion (kN/m2)
1 kN/m2
7.
Permeability (cm/sec)
1.24 x 10-4 cm/sec
8.
Coefficient of uniformity(Cu)
8.56
9.
Coefficient of curvature (Cc)
1.41
3.4.7 CHEMICAL PROPERTIES OF POND ASH
The chemical properties of the pond ash sample are presented in Table No.5 given below. These properties were collected from office of Guru Gobind Singh Super Thermal Power Plant, Ropar.
Table No. 5 Chemical properties of pond ash
S No.
Constituents present
Value
1.
Loss of ignition
4.52
2.
Silica(SiO2)
56.32
3.
Alumina(Al2O3)
30.87
4.
Iron Oxide(FeO2)
4.94
5.
Magnesium Oxide(MgO)
1.58
6.
Calcium Oxide(CaO)