Investigation of the Vortexing Effect on Sawdust Combustion in a Fluidized Bed Combustor

Abstract

The vortexing effect on reducing pollutant emission was verified via the combustion of three groups of sawdust with different diameters in a vortexing fluidized bed combustor (VFBC). The temperatures and pollutant emission distributions along the combustor were measured simultaneously. The combustion fraction in four zones of the VFBC were also calculated on the basis of the oxygen consumption. Additionally, the effects of operating variables, such as the in-bed stoichiometric oxygen ratio and the excess oxygen ratio, on the pollutant emissions were also investigated. The results show that the combustion fractions in the bed and freeboard zones increase with larger particle sizes. However, an inverse trend occurred in other zones. The CO emissions from the three sawdust combustions decrease with an increase in the particle size, excess oxygen ratio, and inbed stoichiometric oxygen ratio, whereas the NO x emissions exhibit an inverse trend. The vortexing effect, which is caused by secondary air injection, demonstrated its effectiveness in prolonging the residence time of sawdust in the high-temperature zone. However, the lowest value of CO emission is still much higher than the minimal requirements of the Taiwan Environmental Protection Agency regulations. Increasing the particle size or compacting the sawdust into pellets are two possible solutions for decreasing the CO emission.

5th Sino-Australian Symposium on Advanced Coal and Biomass Utilisation Technologies

“…Han et al (10.1021/acs.energyfuels.5b02265) compare the combustion characteristics of distilled spirit lees in a circulating fluidized bed and a dual fluidized bed. Duan et al (10.1021/acs.energyfuels.5b01976) investigate the effect of vortexing on sawdust combustion in a fluidized bed. Tilghman and Mitchell (10.1021/acs.energyfuels.5b02480) investigate the gasification behaviors of the chars formed during devolatilization when co-firing coal/biomass blends.…”

“…Yang et al (10.1021/acs.energyfuels.5b02258) 14 prove the concept of type IV gasification for achieving a stand-alone cold gas efficiency over 95% lower heating value. Chen 22 investigate the effect of vortexing on sawdust combustion in a fluidized bed. Tilghman and Mitchell (10.1021/acs.energyfuels.5b02480) 23 investigate the gasification behaviors of the chars formed during devolatilization when co-firing coal/biomass blends.…”