GAS COFIRING FOR PERFORMANCE IMPROVEMENT AND EMISSIONS REDUCTION IN COAL AND WOOD-FIRED BOILERS

Cofiring a small amount of gas in solid-fuel fired boilers is an efficient and economical way to resolve a variety of emissions and performance problems. Gas Research Institute has developed and demonstrated a specialized cofire retrofit package featuring dual, opposed high pressure drop gas burners to control the combustion over the solid fuel. Earlier demonstrations on coal-fired stokers have shown cofire to reduce emissions, enhance performance, increase efficiency and lower operating costs. In the present work, the cofire package has been applied to two coal and two wood-waste fired industrial boilers. At the first coal site, cofire reduced particulate up to 60 percent for 20 percent gas firing. At the second coal site, gas cofire was used to reduce NO x emissions by 20 percent for 20 percent cofire. For wood firing, the strongest driver for gas cofire is to correct for performance degradation caused by wet wood. At the two sites, gas cofire in the 10 to 15 percent range gave recovery of lost capacity derate and up to 90 percent reduction in carbon monoxide emissions.