MILD combustion of co-firing biomass and pulverized coal fuel blend for heterogeneous fuel NO and PM2.5 emission reduction

Abstract

A sawdust and bituminous coal blend is studied experimentally under MILD combustion conditions, and the PM2.5 emissions of MILD combustion are measured. MILD combustion is established by low-temperature preheated air in a 200-kW pilot-scale furnace. The pilot tests consist of the conventional flame combustion through a swirl nozzle, MILD combustion through symmetrical double straight nozzles, and MILD combustion through an asymmetrical single straight nozzle. Compared to conventional swirl flame combustion, the MILD combustion of the sawdust blend can reduce the fuel-NO emission by at least 45.5%. The results further reveal that the PM2.5 emissions are decreased by over 37%. The burnout rates of the sawdust blend MILD combustion are higher than 95%. Considering the in-furnace distribution, low NO and PM2.5 emissions, and high burnout rate, MILD combustion is an effective way to utilize biomass fuel blends on a large scale. This work extends fuel adaptation of MILD combustion to biomass blends. Compared with previous MILD combustion studies, this investigation further confirms the inhibitory effect of MILD combustion on the formation of fine particles.