温度对松木刨花CO_(2)气化过程NO_(x)和SO_(2)排放特性影响

Effect of temperatures on emission characteristics of NO_(x) and SO_(2) for pine shaving under CO_(2) gasification

CO_(2)气化技术是一种利用CO_(2)作为气化剂生产高品质可燃气体的新型技术,可以协同实现CO_(2)和农林固废的资源化利用,然而CO_(2)气化过程中NOx和SO_(2)的排放特性鲜有报道。针对松木刨花在固定床反应器上开展了CO_(2)气化实验,系统研究了温度的影响。结果表明:在700、800、900℃进行CO_(2)气化时,CO产率分别为0.24、0.52和0.95 m^(3)/kg,明显高于H2和CH4的产率,CO是气化产气的主要成分;碳转化率分别为18.36%、36.15%和66.09%;气化效率分别为13.04%、41.59%和92.99%,高温促进了松木刨花的热化学转化。在700~900℃时,NOx中NO的质量浓度峰值和对应时长分别为248、129、138 mg/m^(3)和140、195、320 s,NO_(2)的质量浓度峰值和对应时长分别为339、191、107 mg/m^(3)和115、150、265 s,SO_(2)的质量浓度峰值和对应时长分别为3299、3065、2882 mg/m^(3)和130、175、180 s。NOx和SO_(2)的质量浓度峰值均随温度升高而逐渐降低,对应时长均逐渐增加,表明增加温度有利于降低NOx和SO_(2)的生成速率。然而,NOx和SO_(2)转化率随温度升高而逐渐增大,在900℃分别为49.73%和68.87%,提高温度会强化原料氧和CO_(2)的氧化作用,进而提升NOx和SO_(2)转化率。随着温度升高,NO转化率增加而NO_(2)转化率下降,炉内以CO为主要成分的还原性氛围促使NO_(2)被还原为NO,提高松木刨花的CO_(2)气化温度有利于通过提高CO产率强化该还原作用。

CO_(2) gasification is a novel technique that uses CO_(2) as a gasifying agent to produce syngas with a high calorific value for the synergistic utilization of CO_(2) and biomass waste.However,the emission characteristics of NO_(x) and SO_(2) for biomass waste under CO_(2) gasification are rarely investigated.CO_(2) 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 m^(3)/kg at 700,800,and 900℃,respectively,significantly higher than the yields of H_(2) 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 CO_(2) 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 CO_(2) gasification.Moreover,the peak 3 concentrations and the durations required to reach the peaks of NO in produced syngas are 248,129,and 138 mg/m and 140,195,and 3320 s,respectively;those for NO2 are 339,191,and 107 mg/m and 115,150,and 265 s,respectively,and those for SO2 are 3299,3065,and 2882 mg/m^(3) 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 NO_(x) and SO_(2).However,the conversion yields of NO_(x) and SO_(2) gradually increase as the temperatures increase,reaching 49.73%for NO_(x) and 68.87%for SO_(2) at 900℃.This shows that a higher temperature can enhance the oxidation effect of oxygen in raw material and gasifying agent(CO_(2))on the sulfur and nitrogen in pine shaving,further promoting the conversion yields of NO_(x) and SO_(2).Furthermore,the conversion yield of NO increases while that of NO_(2) decreases with increasing temperatures.The reducing atmosphere in the furnace with CO as the major component contributes to the NO_(2) being reduced to NO.Therefore,increasing the temperatures of CO_(2) gasification for pine shaving can promote the reduction process of NO2 by increasing the yield of CO.