褐煤焦中的矿物质对气化动力学的影响

Effect of minerals in lignite char on kinetics of steam gasification

利用热重分析仪研究了水蒸气气氛下霍林河褐煤焦和脱灰褐煤焦的气化动力学特性,并考察了脱灰前后褐煤焦孔结构的变化。结果表明:褐煤原焦气化反应速率在反应初始阶段(转化率<30%)高于脱灰褐煤焦,但在反应后期低于脱灰焦,这是因为煤焦中灰分的脱除一方面去除了矿物质的催化作用,另一方面增大了煤焦的孔径,因而减小了气化剂的扩散阻力。灰层扩散控制的缩核模型可以描述褐煤焦水蒸气气化过程,而脱灰后褐煤焦水蒸气气化过程用均相模型可以很好地表示。

The steam gasification experiments of Huolinhe lignite char and demineralized lignite char were carried out by using thermogravimetric analyzer（TGA）,and the pore structural characteristics of initial lignite char and demineralized char were also tested.The results show that the reactivity of demineralized char is lower than that of undemineralized char at former stage（conversion rate 30%）;while at latter stage,the demineralized char is higher than undemineralized char.This is because the removing ash in lignite char decreases the catalytic effect of minerals,and increases the pore size of char leading to the declined diffusion resistance of gas agent.The experimental results of lignite char during steam gasification can be well described by shrinking core model with ash layer diffusion controlled.However,the best kinetic model which can explain the reactivity of demineralized char is homogeneous model.