Utilization of biomass ash for upgrading petroleum coke gasification: Effect of soluble and insoluble components

In this paper, the catalytic effect of different components in biomass ash on petroleum coke (PC) gasification was studied. Cotton straw ash with high content of AAEMs and low content of silica, was prepared and pretreated by washing to obtain the soluble (ash leachate) and insoluble (washed ash) components. These ash-based catalysts were added to PC via physical mixing or impregnation. The catalytic gasification performance and kinetics were investigated using a thermal-gravimetric analyzer (TGA), and the carbon structure evolution was determined by Raman spectroscopy. The results showed that all of these ash-based catalysts, even for the washed ash, had catalytic effect on PC gasification. The soluble component, mainly containing K, could speed up the gasification rate especially at the late stage. The catalytic activity of the soluble component was sensitive to temperature and conversion, while that of the insoluble component was steady. Moreover, the modified random pore model and nucleation and growth method were applied to analyze the gasification kinetics. In addition, the washed ash could inhibit the graphitization during gasification, whereas the ash leachate and original ash could enhance the generation of amorphous carbon. Possible mechanisms of catalytic gasification were proposed to explain these phenomena.