热解压力及气氛对神府煤焦气化反应活性的影响

Effects of pyrolysis pressure and atmosphere on gasification reactivity of Shenfu char

利用加压热重分析仪研究了热解压力和气氛对神府煤焦CO2气化反应活性的影响。实验表明,在氮气中,加压热解导致焦油发生再沉积和再聚合反应,即焦油的二次反应,在煤焦颗粒表面上形成二次反应产物层,其活性很差,覆盖煤焦微孔的开孔,影响煤焦的初期气化反应性。氢气中热解,氢气与煤焦中的碳发生加氢气化反应,生成甲烷和其他碳氢化合物,在煤焦颗粒上产生活性位,对煤焦起到活化作用,高压加氢热解有利于加氢气化反应和提高产物煤焦的气化反应活性。加氢气化反应可以在一定程度上消除焦油二次反应的负面影响,并活化煤焦。

The effects of pyrolysis pressure and atmosphere on the CO2-gasification reactivity of Shenfu char were investigated by using a pressurized-TGA. It is found that tar redeposition and repolymerization which occur during pressurized-pyrolysis under N2, i.e. tar secondary reaction, could influence the initial gasification reactivity of char significantly. The tar cracking product produced by tar secondary reaction would cover the surface of char particle and form a less reactive layer, which could overlay the inlet of micro-pores of char particle to decrease the accessibility of reactant to the reactive sites inside the particle and slow down the initial gasification reactivity of char. Hydro-gasification during hydro-pyrolysis consumes the less reactive layer and the carbonaceous part of chars, which forms more reactive sites on chars. Higher hydrogen pressure is favorable for the hydro-gasification and the increase of chars gasification reactivity. Compared with the pyrolysis under N2 , hydro-pyrolysis is advantageous to increase the gasification reactivity of chars. Under N2 atmolsphere, tar secondary reaction would decrease the reactivity of chars. However, in the case of hydro-pyrolysis, the negative effects brought by tar secondary reaction can be rule out by the activation of the char by the hydrogasification. It is noted that under the experiment conditions used in this study, hydro-pyrolysis is favorable for increasing the gasification reactivity of chars either at atmospheric pressure or at higher pressures.