Technology for Air Pollution Control – Part1. Techniques Without Using Emissions Control Devices . Process Change Wind, Geothermal, Hydroelectric, or Solar Unit instead of Fossil fired Unit. Change in Fuel e.g. Use of Low Sulfur Fuel, instead of High Sulfur fuel. Good Operating Practices
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Change to Low Sulfur Fuel
Use Desulfurized Coal and Oil Increase Effective Stack Height
The major flue gas desulfurization ( FGD ), processes are :
CaCO3 + H2O + 2SO2 ----> Ca+2 + 2HSO3-+ CO2
CaCO3 + 2HSO3-+ Ca+2 ----> 2CaSO3 + CO2 + H2O
The reactions occurring during lime scrubbing are :
CaO + H2O -----> Ca(OH)2
SO2 + H2O <----> H2SO3
H2SO3 + Ca(OH)2 -----> CaSO3.2 H2O
CaSO3.2 H2O + (1/2)O2 -----> CaSO4.2 H2O
Schematic process flow diagram – SO2 scrubbing and recovery system
The flue gas is pre - treated to remove the particulate. The sodium sulfite neutralizes the sulfur dioxide :
Na2SO3 + SO2 + H2O -----> 2NaHSO3
NO and NO2 are the most common of the seven oxides listed above. NOx released from stationary sources is of two types
Schematic process flow diagram – NOX control
4 NO + 4 NH3 + O2 -----> 4N2 + 6H2O
2NO2 + 4 NH3+ O2 -----> 3N2 + 6H2O
30% to 50% reductions in NOx emissions are achieved.
Note : CO & NOx control strategies are in conflict.
(x-axis units are teragrams of CO2 equivalent)
(y-axis units are teragrams of CO2 equivalent)
Source: Seingeur, 2004 and Mason and Sheu, 2002.
Worldwide Distribution of Emissions
Source: Presentation by J. Pacyna and J. Munthe at mercury workshop in Brussels, March 29-30, 2004
Particles of activated carbon are injected into the exit gas flow, downstream of the boiler. The mercury attaches to the carbon particles and is removed in a particle control device
It is a process which extracts partially burned coal from a pulverized coal-fired combustor using a suction pipe, or "thief," and injects the resulting sorbent into the flue gas to capture the mercury.
Range: 20 to 40000 mg/m**3
First step: Process control
Second step: Use of collection device
( satisfactory for air and ground transportation )
Gravity and Momentum collectors
Ci inlet concentration
Co outlet concentration
Note: The smaller the particle, the lower is
efficiency of removal.
Assuming an initial feed of 100%, determine the percentage of the stream fed to the ESP.
100% - (100% x 0.75) = 25%
Determine final composition after ESP.
25% - (25% x 0.9) = 2.5%
Determine overall efficiency
hoverall = (initial – final)/ initial
= 100% - 2.5%100% = 97.5%