生物质型煤制备参数优化及燃烧污染物释放特征
Optimization of preparation parameters of biomass briquette and emission characteristics of combustion pollutants
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摘要: 民用固体燃料低效燃烧产生了大量污染物。根据我国经济发展水平和各地现实情况,消费适合农村和乡镇的清洁固体燃料是减少面源大气污染物排放的有效途径。用无烟煤分别与不同比例的生物质(小麦、玉米和水稻)秸秆混合、压制成型,制备民用固体燃料,通过正交试验研究优化无烟煤-秸秆生物质型煤的冷压成型工艺参数,并在典型的民用灶具上对生物质型煤的燃烧热效率和主要污染物排放因子进行了测试和分析。结果表明,在生物质质量分数20%、粒度上限1 mm、成型压力25 MPa、粘结剂质量分数10%等优化的制备工艺参数下,制得生物质型煤的抗压强度最高,达到15.98 kN/个,对应的落下强度值为99.87%;秸秆生物质型煤热效率增加了81%~137%,PM2.5的排放因子降低了90~98%,CO的排放因子降低了48%~92%,NO2和SO2以及PM2.5颗粒物中有毒元素As、Se、Pb的排放因子也大幅度降低。生物质和无烟煤混合燃烧的协同作用是节能减排的重要原因,生物质的加入,降低了型煤的热解温度、着火点和燃烬温度,其热解气体助燃无烟煤颗粒、燃烬后体积收缩且多孔又为无烟煤的进一步燃烧提供了发达的气体通道,利于氧气与固相充分接触、燃烧,热效率提高,污染物的排放降低。Abstract: A large number of pollutants are produced by the inefficient combustion of civil solid fuels. According to China’s economic development level and the reality of various regions,the consumption of clean solid fuels suitable for rural areas and towns is an effective way to reduce the emission of non-point source air pollutants. Anthracite was mixed with different proportion of biomass (wheat,corn and rice) straw to prepare civil solid fuel. The process parameters of cold briquetting of anthracite-straw biomass briquette were optimized by orthogonal experiment. The combustion thermal efficiency and main pollutant emission factors of biomass briquette were tested and analyzed on typical civil stove. The experimental results show that the maximum compressive strength of briquette is 15.98 kN/pellet,and the corresponding drop strength is 99.87% under the optimized conditions of biomass dosage 20%,particle size upper limit 1 mm,molding pressure 25 MPa,binder 10%; The thermal efficiency of biomass briquette was increased by 81%~137%,the reductions of emission factors were 90~98% for PM2.5 and 48%~92% for CO,and the emission factors of NO2,SO2 and toxic elements As,Se and Pb in PM2.5 were greatly reduced as well. The synergistic effect of biomass and anthracite is an important reason for energy saving and emission reduction. The addition of biomass reduces the pyrolysis temperature,ignition point and burn out temperature of briquette. The pyrolysis gas of biomass supports the combustion of anthracite particles. Besides,the volume of biomass shrinks and is porous after burning out,which provides a developed gas channel for further combustion of anthracite. Due to the full contact between oxygen and solid phase,the combustion is full,the thermal efficiency is improved,and the emission of pollutants is reduced.