煤化学链燃烧中CaSO_4/膨润土复合载氧体的反应特性

Investigation on Reactivity of CaSO_4/Bentonite Oxygen Carrier in Coal Direct Chemical-Looping Combustion

以工业级硫酸钙和膨润土为原料，通过机械混合法，制备了具有高强度的钙基载氧体。同时，在小型高温流化床上，以水蒸气为气化剂，考察了不同温度下载氧体与煤的反应活性和循环反应性。实验结果表明， CaSO4/膨润土载氧体具有高的机械强度。在820～900℃，载氧体与煤反应性随温度升高而增强。反应温度为900℃时，气体产物中CO2平均浓度为89.52%，基本不存在CO和CH4。随着还原/氧化循环数增加，载氧体表现良好的反应性，7次循环反应后，碳转化率在70%以上，CO2的平均体积含量保持在80%左右。X射线衍射分析表明，载氧体的还原产物为CaS，未生成CaO副产物。

In this paper, CaSO4/bentonite particle was prepared with industrial grade materials using mechanical mixing methods. The experiments were carried out in a fluidized bed, where the steam acted as the gasification fluidization medium. The effects of temperature in the reactor and cyclic reduction number on reactivity of CaSO4/bentonite with coal were discussed. It showed that the reactivity of the oxygen carriers was enhanced as temperature was increased from 820 ℃ to 900 ℃. At 900 ℃, the average dry basis concentration of CO2 approached 89.52% and there were no CH4 and H2 existing. The seven redox tests demonstrated that the CaSO4/bentonite oxygen carrier particles were featured by the high reactivity and excellent cycling stability. The carbon conversion rate was above 70%and CO2 concentration kept at 80%over seven redox cycles. X-ray diffraction analysis revealed that CaSO4 could be reduced into CaS which is also almost oxidized into CaSO4 without CaO generating.