煤焦CO_2气化反应动力学及内扩散对气化过程的影响分析

Reaction kinetics of coal char gasification with CO_2 and the effect of internal diffusion on the gasification

采用热重分析仪考察了气化温度(850-1 150℃)和煤焦粒径(<60、505、950、1 515、2 000μm)对常压下神木煤焦气化反应的影响。在此基础上,运用体积模型、缩核模型和随机孔模型研究了煤焦常压二氧化碳气化反应动力学,分析了内扩散对煤焦气化反应的影响。结果表明,随机孔模型能够准确预测反应速率随煤焦转化率的变化。基于本征动力学数据,通过对Thiele模数、内扩散效率因子的计算,并将其与实验效率因子相比较,发现计算效率因子能够评估内扩散对初始气化反应的影响,但不能准确评估整个气化过程中内扩散对气化反应的影响。

The effects of temperature （850-1 150 益）and particle size （〈 60, 5 05,9 50,1515 and 2 000 μm ） on the gasification of Shenmu coal char with CO2 were investigated by using thermogravimetric apparatus （T G A ） under atmospheric pressure. Three kinetic models of volumetric, shrinking core and random pore were applied to validate the experimental results, which illustrates that the random pore model can accurately predict the conversion rate for coal char gasification. Thiele modulus and effectiveness factor were determined on the basis of the intrinsic kinetic rate at 850-1 000℃;a comparison between calculated and experimental effective factors suggests that the calculated effective factor can give a quantitative estimation of the effect of internal diffusion on the initial stage of gasification, but cannot describe the whole gasification process.