Synergistic co-combustion of carbon-rich fraction from coal gasification fine slag and corncob char: Performance, mechanism, kinetics, and thermodynamics

Abstract

Coal gasification fine slag (FS) is a coal-based solid waste with high carbon content, and landfill-based disposal causes water-soil-gas composite pollution. Co-combustion is a common method of solid waste thermal disposal, and corn cob is used as an auxiliary fuel for co-combustion because of its energy density and ease of handling and processing. In this paper, the thermal degradation characteristics, interaction mechanism, kinetics, and thermodynamics of co-combustion RC (carbon-rich fraction obtained by flotation) and CC (corncob char) were studied. The results showed that physicochemical properties suggested that RC and CC will complement and promote each other in the combustion process. The addition of CC reduced the RC ignition temperature and improved the overall combustion performance. The interaction effect was mainly due to metal catalysis, the effect of the porous carbon structure, the thermal effect, and the hindering effect of ash. The activation energy was reduced due to the blending of RC-CC, and the activation energy was lowest (132.19 kJ/mol) when the RC adding ratio was 60%. The co-combustion process was controlled by the F3 model (chemical third-order reaction kinetics), and it was a typical gas-solid phase reaction with a progressive process from the outsides toward the insides. Thermodynamic analysis showed that the co-firing process was an extremely complex multi-stage reaction. The results of this study provide a theoretical reference for the synergistic resource utilization of coal gasification fine slag and waste biomass.