碱金属对煤热解和气化反应速率的影响

摘要

The effect of alkali metal (AM) on crystallite structure of chars prepared by the pyrolysis of original and acid-washed coal without and with AM at 800-1050℃ in tubular furnace was investigated by XRD (X-ray diffraction) technique. The pyrolysis of coal samples and the gasification of chars were studied by PTGA (pressurized thermogravimetric analysis). The results show that both coal pyrolysis and gasification is affected by AM. At pyrolysis stage, the existence of AM inhibits the progress of char graphitizing, promotes the pyrolysis reaction and reduces its activation energy; at char gasification stage,AM is a catalyst, reduces gasification activation energy, goes up rate and prolongs the time to reach the maximum gasification rate. Modified random pore model can be used to describe the char-CO2 gasification process properly.%通过对原煤、酸洗原煤、负载碱金属的酸洗原煤在800～1050℃热解制得焦样,用X射线衍射技术考察了碱金属对煤焦微晶结构的影响,在加压热天平(PTGA)上考察了煤样的热解过程,以及焦样的二氧化碳气化活性.结果表明:碱金属对煤的热解和气化阶段都有影响.在热解阶段,碱金属的存在抑制了煤焦的石墨化进程,降低了热解反应活化能,促进了热解反应的进行;在气化阶段,作为催化剂的碱金属,降低了气化反应活化能,延长了反应速率达到最大值的时间.修正的随机孔模型可以较好地描述煤焦-CO2的气化反应过程.