Effect of temperatures on emission characteristics of NOx and SO2 for pine shaving under CO2 gasification
CO2 gasification is a novel technique that uses CO2 as a gasifying agent to produce syngas with a high calorific value for the synergistic utilization of CO2 and biomass waste.However,the emission characteristics of NOx and SO2 for biomass waste under CO2 gasification are rarely investigated.CO2 gasification experiments were carried out on a fixed bed reactor for pine shaving in order to provide a temperature reference for thermochemical conversion utilization and pollutant emission control of biomass waste.The results show that the yield of CO is 0.24,0.52,and 0.95 m3/kg at 700,800,and 900 ℃,respectively,significantly higher than the yields of H2 and CH4.Thus,CO is the major component of the produced syngas.In addition,the carbon conversion yield is 18.36％ 、36.15％ ,and 66.09％ ,respectively,and the CO2 gasification efficiency is 13.04％ ,41.59％ ,and 92.99％ at 700-900 ℃,respectively.These phenomena indicate that increasing temperatures can contribute to the thermochemical conversion of pine shaving under CO2 gasification.Moreover,the peak concentrations and the durations required to reach the peaks of NO in produced syngas are 248,129,and 138 mg/m3 and 140,195,and 320 s,respectively;those for NO2 are 339,191,and 107 mg/m3 and 115,150,and 265 s,respectively,and those for SO2 are 3 299,3 065,and 2 882 mg/m3 and 130,175,and 180 s,respectively.The peak concentrations of both NOx and SO2 gradually decrease and the required durations increase as the temperatures increase,suggesting that the increase in temperature contributes to a reduction in the yields of NOx and SO2.However,the conversion yields of NOx and SO2 gradually increase as the temperatures increase,reaching 49.73％ for NOx and 68.87％ for SO2 at 900 ℃.This shows that a higher temperature can enhance the oxidation effect of oxygen in raw material and gasifying agent(CO2)on the sulfur and nitrogen in pine shaving,further promoting the conversion yields of NOx and SO2.Furthermore,the conversion yield of NO increases while that of NO2 decreases with increasing temperatures.The reducing atmosphere in the furnace with CO as the major component contributes to the NO2 being reduced to NO.Therefore,increasing the temperatures of CO2 gasification for pine shaving can promote the reduction process of NO2 by increasing the yield of CO.
pine shavingCO2 gasificationgasification efficiencyNOxSO2emission characteristics
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