煤炭燃烧过程中重金属迁移及控制规律的热力学模拟

Thermodynamic simulation of heavy metals' emissions and control in coal combustion

选择对人体和环境危害程度较大的有害元素汞(Hg)、铅(Pb)和铬(Cr)作为研究对象,利用FactSage软件模拟煤炭燃烧过程中温度、压力对3种重金属的迁移情况并探究若干种元素及化合物对其控制作用影响。结果表明,温度较压力对重金属迁移影响更为显著。Hg在燃烧全程以不同形态接近100%的迁移量进入气相;Pb在850℃开始大量迁移;Cr在1150℃产生迁移趋势。从热力学角度Hg无法被固定;Pb会与Al_2O_3形成高熔点的化合物得到有效抑制;Cr与碱金属、碱土金属形成高熔点的化合物被赋存在固相或液相中,MnO对Cr也存在间接抑制作用。3种重金属对Cl元素尤为敏感,高氯煤的燃烧除了其本身存在污染外势必会与重金属形成低沸点化合物产生强烈气相迁移并造成进一步的生态破坏。

Mercury （Hg）, plumbum （Pb） and chromium （Cr） which are harmful to humans and the environment were selected to inves- tigate their emissions and ways to control the emission in coal combustion by using FactSage software. The emission behaviors of the three heavy metals were studied by varying the temperature and the pressure, and they were controlled by introducing several elements and compounds in coal combustion. It is found that the temperature played a significant role compared with the pressure on heavy met- als＇ emission. In the combustion process, 100% Hg migrated to the gas phase, while Pb and Cr begin to migrate at 850℃ and 1150℃ respectively. The reason is that Hg cannot react with other elements, while Pb and Cr react with Al2O3, alkali metals and alkaline earth metals to form compounds with high melting points. In addition, MnO had an indirect inhibitory effect on Cr. The three metals were found to be sensitive to Cl. They form compounds with low boiling points in the process of combustion of high-chlorine coal which may enhance the gas-phase mobility and lead to ecological pollution. Keywords： coal combustion; FactSage; heavy metal; thermodynamic equilibrium; simulation