煤与甲烷共转化过程中煤焦二氧化碳气化动力学研究

A kinetic study of CO_2 gasification of a Chinese coal char during combined coal gasification and CH_4 reforming

以煤与甲烷共转化为背景,运用热重方法进行了由煤焦、甲烷和二氧化碳组成的共转化反应体系中碳的反应动力学研究。在1173 K^1273 K考察了温度对碳转化的影响。结果表明,该反应体系中碳的表观反应速率比煤焦的纯二氧化碳气化速率慢一倍左右,且表观上碳不能完全被气化。通过改变甲烷和二氧化碳的比例考察了气相组成变化对共转化反应中碳转化速率的影响,发现甲烷浓度的增加和二氧化碳浓度的减少都会降低碳的转化速率,且随着甲烷浓度的增加,表观上碳最终所能达到的转化率也会降低。通过数据分析发现,该反应适合采用均相反应模型进行描述,关联得到其表观活化能为312.4 kJ/mol,甲烷的反应级数为-0.13,二氧化碳的反应级数为0.3。

The kinetics of CO2 gasification of a Chinese coal char during combined coal gasification and methane reforming have been studied using a thermo-gravimetric analyzer. The effect of methane on CO2 gasification of the char from 1173 K to 1273 K was examined. The results show that the coal char conversion rate increases with increasing temperature but decreases with increasing CH4 concentration. Carbon deposition, due to CH4 cracking, is reduced as temperature and carbon dioxide concentration increase. Two standard gas-solid reaction kinetic models, viz. the constant particle size （or progressive-conversion） model and the shrinking-core model, were applied to describe the overall carbon conversion of the char. It is found that the constant particle size model fits the experimental data better than the shrinking-core model. Accordingly the activation energy, reaction orders in CH4 and CO2 based on the constant particle size model are determined to be 312.4 kJ/mol, - 0. 13 and 0.3, respectively. The presence of methane slows down the gasification rate of coal char.