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ANNEX 1

Table A1.1: Comparison of Combined SO2/NOx Control Processes


Process Advantages Disadvantages
Adsorption/ Regeneration High-temperature gas is not required
High removal efficiency
Low volume of wastes
Potentially marketable byproduct
Solids recirculation is complex
High sorbent costs
High flue-gas pressure loss
Flue Gas Irradiation High temperature gas is not required
SO2, NOx, and particulate removal in one device
Potentially marketable byproduct
High auxiliary power
High-cost reagent (ammonia)
Potential for secondary emissions (e.g., N2O)
Byproduct difficult to dispose of
Wet Scrubbing Additive for NOx Removal Easily retrofittable to scrubbers
One vessel for SO2 and NOx removal
Process chemistry also suitable for high-sulfur coals
Complex and precise process control needed
Wastes contain nitrogen/sulfur compounds
Flue-gas reheating may be required
Gas/Solid Catalytic Operations No solids recirculation
High SO2 and NOx removal
Potentially marketable byproduct
High temperature gas needed
Acid collection adds complexity
Catalysts must be replaced periodically
Electromechanical Mechanically simple
One device for both SO2 and NOx removal
No reagents needed
No high volume wastes
High auxiliary power required
High-temperature gas required
Dry Alkali High temperature gas not required
Easily retrofittable to dry scrubbers
High simultaneous SO2 and NOx removal may not be possible
Wastes difficult to dispose of
Potential for secondary emissions (e.g., NO2)

Source: Power Magazine (1990)

From Technological Alternatives to Reduce Acid Gas and Related Emissions from Energy-Sector Activities in Northeast Asia by David Von Hippel