加压热解半焦特性及有害元素演化行为研究
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摘要
通过固定床加压热解模拟实验,考察了不同煤焦特性及有害元素演化行为;借助FactSage热力学计算对有害元素在热转化过程中的形态进行了分析。结果表明,加压显著提高煤焦比表面积和总孔容积,为反应物扩散提供有利条件。较高的反应温度导致矿物质熔融或表面烧结,阻塞煤焦孔隙,不利于内部产物扩散。加压热解过程中,70%以上的Hg、As和Se挥发进入气相中,表现出高挥发性;F、Cd和Pb的挥发率随温度升高显著增大。热力学计算结果显示,当温度高于800℃时,主要生成HF(g)、Hg(g)、AsH_3(g)、H_2Se(g)、Cd(g)、PbS(g)和Pb(g)等有害元素化合物。
Coal chars were prepared using a pressurized pyrolysis reactor and their physic-chemical properties were studied. And the releasing behaviors of harmful elements were investigated by means of Fact Sage simulation. Results indicate that pressurized pyrolysis significantly achieve higher specific surface area and pore volume, and then accelerates the releasing of reactants. The higher temperature will give rise to the agglomeration and sintering of internal minerals, and thus block the pores of coal char. To some extent, it will restrain the dispersion of reactants. More than 70% of Hg,As and Se in coal volatilize into the gas phase during pressurized pyrolysis, reflecting their high volatility characteristic. The releasing behaviors of F,Cd and Pb are obviously affected by temperature; and their volatilities increased significantly with the temperature rising. Speciation prediction shows that, the species, such as HF(g),Hg(g),AsH_3(g),H_2 Se(g),Cd(g),PbS(g) and Pb(g),could potentially exist in the gas phase when pyrolysis temperature is higher than 800 ℃.
Coal chars were prepared using a pressurized pyrolysis reactor and their physic-chemical properties were studied. And the releasing behaviors of harmful elements were investigated by means of Fact Sage simulation. Results indicate that pressurized pyrolysis significantly achieve higher specific surface area and pore volume, and then accelerates the releasing of reactants. The higher temperature will give rise to the agglomeration and sintering of internal minerals, and thus block the pores of coal char. To some extent, it will restrain the dispersion of reactants. More than 70% of Hg,As and Se in coal volatilize into the gas phase during pressurized pyrolysis, reflecting their high volatility characteristic. The releasing behaviors of F,Cd and Pb are obviously affected by temperature; and their volatilities increased significantly with the temperature rising. Speciation prediction shows that, the species, such as HF(g),Hg(g),AsH_3(g),H_2 Se(g),Cd(g),PbS(g) and Pb(g),could potentially exist in the gas phase when pyrolysis temperature is higher than 800 ℃.
引文
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