Effect of coal rank and circulating fluidized-bed operating parameters on nitrous oxide emissions

The effects of operational parameters and coal type on N 2 O emissions in a pilot-scale circulating fluidized-bed combustor (CFBC) were examined. Operational parameters included combustor temperature, excess combustion air, limestone feed rate, and primary:secondary combustion air split. Seven coals ranging in rank from lignite to high-volatile A bituminous were used to study coal-related effects. At typical operating conditions (20% excess air, 1120 K), N 2 O emissions ranged from 30 to 170 ppmv at 3% excess O 2 or 16 to 100 mg N 2 O/MJ heat input due to variations in coal type. The relative impact of operational parameters on N 2 O emissions is given for Salt Creek coal by the relation: temperature > excess air, primary/secondary air split > sorbent feed