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

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 atmosphere, 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.