Effect of corn stalks on coal catalytic hydrogasification in a pressurized fluidized bed for manufacturing CH4

Coal catalytic hydrogasification (CCHG) is a straightforward approach for producing substituted natural gas with a high CH4 yield and thermal efficiency. To reduce fossil fuel consumption for CH4 manufacturing, this work proposed a integrated process combining CCHG and biomass hydrogasification. Using a pressurized fluidized bed, the effect of corn stalks (CS) on CCHG was carefully analyzed in terms of product formation behavior, catalysis process, and feedstock adaptability. Experimental results showed that CS benefits CCHG in terms of reactivity, CH4 production, and CO2 emissions. Specifically, adding 30 wt% CS resulted in a maximum CH4 formation rate of 94.9 ml/g·min, production capacity of 1.38 Nm3 CH4/kg coal, and CO2 emissions of 26.37 g/mol CH4, which were 2.25, 1.29, and 0.69-folds that of cobalt-catalyzed hydrogasification alone, respectively. In the rapid pyrolysis stage, CS volatiles promoted Co dispersion and restrained coal structure ordering by mediating the interactions between cobalt catalysts and coal, favoring the subsequent hydrogasification. Meanwhile, the cobalt-containing char catalyzed methanation of CS-pyrolyzed volatiles, increasing CH4 formation while decreasing CO, CO2, C2-C3, and tar yields. In the gasification stage, Ca and Mg compounds in biomass ash gradually promoted the catalytic hydrogasification of coal char via potential Lewis basic-acid interactions. These mutual behaviors of CS and catalyst-containing coal were found to be universal in hydrogasification and helped strengthen cheaper but less active Fe/Ni catalysts. This work will provide theoretical guidance for future research on the production of CH4 with a low carbon footprint via co-hydrogasification of biomass and coal.