神府煤焦与水蒸气、CO_2气化反应特性研究

Characteristic of the Shenfu coal char gasification with steam and carbon dioxide

采用高温微量热天平和自制水蒸气发生装置进行神府煤焦与水蒸气和CO2气化实验,考察热解速率、不同气化剂(CO2和水蒸气)以及温度对气化反应的影响。用扫描电镜和吸附仪测定煤焦的初始结构。两种煤焦孔径为2nm～170nm的孔占总孔容的90%以上。神府快速煤焦(FP)与水蒸气气化活性比慢速煤焦(SP)高4.16倍,FP比SP挥发分脱除快,破坏其孔结构,减少缔合机会和二次反应。SP的BET比表面积为1.0777m2/g,FP的BET比表面积为1.8939m2/g。SP与水蒸气气化活性是CO2的9.94倍,FP与水蒸气的气化活性是CO2的7.15倍,水蒸气比CO2气化时进入的孔径范围广及水蒸气比CO2更容易解离。同种煤焦与水蒸气和CO2气化时的气化速率与转化率之间的趋势相近。用随机孔模型拟合并求取反应动力学参数,温度对SP与水蒸气、CO2反应速率,以及FP与水蒸气反应速率影响相似,而对FP与CO2反应速率影响明显比前三个反应要小。

The effects of the heating rate of pyrolysis, the different reaction agents (steam and carbon dioxide) and temperature on the gasification of Shenfu coal char at ambient pressure and 850°C-1000°C by TGA were investigated. The initial structure of coal char was analyzed by SEM and N2 physisorption apparatus. The pore volume of the pore size of 2nm^170nm accounts for above 90% of the total pore volume. The BET surface area of SP (slow pyrolyze char) is 1.0777 m2&middotg-1, and the BET surface area of FP (fast pyrolyzed char) is 1.8939 m2&middotg-1. The reactivity index of the fast pyrolyzed char gasification with steam is 4.16 times higher than that of slow pyrolyzed char, which is resulted from the destruction of the structure of pore and retarding of secondary reaction because of the higher escaping rate of volatile from fast pyrolysis. The gasification reactivity index of the SP char and the FP char with steam is 9.94 and 7.15 times higher than with carbon dioxide respectively, because steam can come into wider range of pores and be dissociated easier than carbon dioxide. The experimental data was fitted by the random pore model and the kinetic parameters were obtained. Gasification temperature has a similar effect on the gasification reaction rate of the SP char with steam and carbon dioxide and the FP char with steam, however, a smaller effect on the FP char gasification with CO2 is found.