温度对载氧体还原过程中汞的析出特性及形态分布的影响

Characterization of mercury releasing during reduction of oxygen carriers with coal in chemical looping combustion

化学链燃烧是近年来提出的一种具有高效、内分离CO_2特点的新型燃烧方式。本文在立式管式炉实验装置上研究了温度对基于Fe_2O_3载氧体的煤化学链燃烧载氧体还原过程中汞析出特性的影响,探讨了不同燃烧温度下燃料反应器(FR)出口烟气组分的变化及其对汞迁移变化的影响。结果表明:在高温条件下(≥800℃),煤中的汞在载氧体还原过程中基本全部析出,180s时基本达到90%,并且随着温度升高而增加;FR出口烟气中的汞主要以单质态(Hg^0)形式存在,各工况下的单质态汞占烟气中气态总汞比例都在88%以上,随着温度的升高,烟气中Hg^0/Hg^T略有降低;温度对烟气组分具有影响,随着温度的升高,CO、NO和SO_2浓度上升;对于汞而言,SO_2会抑制Cl及Cl_2的形成从而抑制Hg^0向Hg^(2+)转化,NO会直接或间接促进汞的氧化过程,FR烟气中以CO为主的还原性气氛不利于汞的氧化。

Chemical looping combustion is one of the promising technologies to capture CO_2 with low cost.The effect of temperatures on mercury speciation and transport during coal chemical looping combustion based on Fe_2O_3 oxygen carriers were studied in a vertical tube furnace device.The change of flue gas components at different temperatures and the oxidation mechanism of elemental mercury on flue gas from fuel reactor were also investigated.The results showed that mercury in coal was completly released and the discharge rate reached 90%in 180s at high temperature in FR.The major mercury species was Hg^0 and the ratio Hg^0/Hg^T was 88%.The rate of Hg^0/Hg^T decreased with increasing temperature.Different temperature affected the components of flue gas.The elevated temperature could cause an increase in the SO_2,NO and CO.SO_2 could inhibit the oxidation of mercury by inhibiting the formation of Cl/Cl_2.The NO could promote the oxidation of mercury,but CO had an opposite effect.