生物质气与煤混燃锅炉运行及污染物排放特性分析

发布时间：2018-07-14 15:08

【摘要】：生物质气与煤混燃不仅可以高效利用生物质,而且替代部分燃煤,减少污染物的排放,并且有益于锅炉的燃烧以及运行。论文以某300MW燃煤锅炉为研究平台,基于Aspen Plus流程模拟软件对生物质与煤的间接混合燃烧技术,即用生物质气化合成气代替部分煤粉与煤进行混燃的污染物排放特性和锅炉性能影响进行模拟研究,主要的研究内容和结论如下:(1)利用Aspen Plus建立生物质气化模型,进行生物质气化过程的研究,确定气化过程的最佳空燃比。生物质选取低位热值较高的松木,对不同含水率的松木进行气化,随着空燃比增大,气化合成气H2、CH4、CO_2的体积分数均减小,CO先增大后减小,H2O先减小后增大,N2产量增加;气体热值和气化效率均随着空燃比的增大呈先增加后减小的趋势,且都在某一空燃比下达到最高,确定该空燃比即为最佳空燃比。(2)基于Aspen Plus建立生物质气与煤混燃模型,对不同含水率的松木气化合成气与煤混燃过程进行模拟研究。将含水率分别为10%、20%、30%的松木在各自最佳气化工况下的合成气送至锅炉与煤混合燃烧,随着生物质气掺烧比例和含水率的增加,最高燃烧温度逐渐降低;排烟体积和排烟温度均随含水率的增加而增大,而锅炉效率降低。(3)选取三种不同品质的烟煤与含水率为20%的松木气化合成气混合燃烧,研究和分析煤种与掺烧比例对混燃污染物和锅炉运行性能的影响。不同掺烧工况对应的最高燃烧温度均随着煤种品质的降低和掺烧比例的增加而降低;随煤种品质降低,混燃产生的污染物NO_x减少,而SO_2增多,但都随掺烧比例的增加而减少;优质煤掺烧后的排烟体积最多,排烟温度最高,锅炉效率最低,而劣质煤掺烧后的锅炉效率最高。(4)对纯煤燃烧和生物质气与煤按不同掺烧比例混燃的CO_2减排量、NO_x、SO_2排放浓度及减排率进行计算和分析,生物质气与煤的混燃不仅可以节约煤耗,而且降低污染物的排放。
[Abstract]:The mixed combustion of biomass gas and coal can not only efficiently use biomass, but also replace some of the coal combustion, reduce the emission of pollutants, and be beneficial to the combustion and operation of the boiler. In this paper, a 300MW coal-fired boiler is used as the research platform, and the indirect mixed combustion technology of biomass and coal based on Aspen Plus process simulation software is used. The pollutant emission characteristics and boiler performance effects of mixed combustion with biomass gasification syngas instead of some pulverized coal and coal are simulated and studied. The main contents and conclusions are as follows: (1) the biomass gasification model is established by Aspen Plus. The optimum air fuel ratio of biomass gasification process was determined. With the increase of air-fuel ratio, the volume fraction of H _ 2H _ 4C _ 4C _ 2 of gasified gas is decreased firstly and then decreased by H _ 2O _ 2O, then increased by increasing N _ 2 yield. The biomass of pine wood with high low calorific value is gasified by gasification of pine wood with different moisture content. The gas calorific value and gasification efficiency increase first and then decrease with the increase of air-fuel ratio, and both reach the highest at a certain air-fuel ratio. (2) based on Aspen Plus, the biomass gas and coal mixed combustion model is established. The mixed combustion process of pine gasification syngas and coal with different moisture content was simulated. The syngas of the pine with water content of 10% and 20% and 30% respectively was sent to the boiler and coal for mixed combustion under their optimum gasification conditions. With the increase of biomass gas blending ratio and moisture content, the maximum combustion temperature decreased gradually. The volume and temperature of exhaust gas increased with the increase of moisture content, but the boiler efficiency decreased. (3) three different quality bituminous coal and pine wood gasification syngas with 20% moisture content were mixed combustion. The effect of the ratio of coal to mixed combustion on the mixed combustion pollutant and boiler performance is studied and analyzed. The maximum combustion temperature corresponding to different blending conditions all decreased with the decrease of coal quality and the increase of blending ratio, and with the decrease of coal quality, the no _ x produced by mixed combustion decreased, while so _ 2 increased, but all decreased with the increase of blending ratio. The volume of exhaust gas is the largest, the temperature of exhaust gas is the highest, and the boiler efficiency is the lowest after mixed burning of high quality coal. But the boiler efficiency after mixed burning of inferior coal is the highest. (4) to calculate and analyze the emission concentration and emission reduction rate of CO-2 emission reduction quantity and emission reduction rate after mixed combustion of pure coal and biomass gas with coal in different blending proportion, the combustion of biomass gas and coal can not only save coal consumption. And reduce the emission of pollutants.
【学位授予单位】：华北水利水电大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TK229.6;TK6

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