Control of pollutants in the combustion of biomass pellets prepared with coal tar residue as a binder

Abstract

This study involved comprehensively investigating pollutant emissions and control methods of NO, SO2, polycyclic aromatic hydrocarbons (PAHs) and dioxins (PCDD/Fs) in the combustion of biomass pellets prepared with hazardous waste of coal tar residue (CTR) as a binder. The NO emissions from moso bamboo pellets and SO2 emissions from wheat straw pellets corresponded to the highest emissions among the three biomass pellets. In contrast, NO and SO2 emissions from the sawdust pellet corresponded to the lowest emissions among three biomass pellets. When the biomass pellets were prepared with 30wt% CTR binder, the pollutant emissions of NO, SO2, PAHs and PCDD/Fs were significantly lower than those in the direct combustion of only CTR. The SO2 emissions of wheat straw pellets with 30wt% CTR binder gradually increased when the furnace temperature increased from 800°C to 1300°C. Conversely, the NO emission gradually decreased because more volatiles derived from biomass pellets locally generated stronger reducing atmospheres at a higher temperature to restrict the NO production. The SO2 emission of wheat straw pellets with 30wt% CTR binder decreased by 55.6%–71.0% when limestone was added with a molar ratio of Ca/S at 2, while emission factors of PAHs and total I-TEQ of PCDD/Fs decreased by 13.3% and 59.9%, respectively, at 1200°C.