Effect of calcium oxide on high-temperature steam gasification of municipal solid waste

•CaO shows a good capacity of CO2 adsorption at devolatilization stage of MSW.•CaO acted as a catalyst both in MSW devolatilization and char steam gasification.•Good dispersion and mobility of calcium in char were observed.•Catalytic mechanism during devolatilization and char gasification were discussed.

Steam gasification of municipal solid waste (MSW) using a CaO additive was investigated in a batch-type fixed bed, to examine the effects of CaO addition on the heat transfer properties, the devolatilization characteristics of MSW, CO2 adsorption capacities of CaO, and char gasification in the presence of steam. Evolutionary behaviors of syngas molar compositions and individual gas flow rates at both MSW devolatilization and char gasification stages were examined at different CaO/MSW mass ratios with a fixed MSW mass. The effect of temperature varying from 700 to 900 °C was also considered in this test. In both stages, hydrogen concentrations were found to increase and CaO was found to have a catalytic effect. Finally, using from the experimental observations and the results of SEM/EDS analyses of the obtained residues, the mechanism underlying the catalytic effects of calcium species in both reaction stages was discussed.