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
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%