Combustion and slagging characteristics of hydrochar derived from the co-hydrothermal carbonization of PVC and alkali coal

Abstract

This work investigated on the effect of co-hydrothermal carbonization (co-HTC) of polyvinyl chloride (PVC) and alkali coal on combustion and slagging characteristics of the generated fuels (hydrochar). Fuel properties were assessed in terms of ultimate and proximate analysis, functional groups evolution, and ash melting characteristics. The loss of C–O functional groups in coal would be accompanied by the liberation of some elements such as Na and Ca, which were often associated with such groups. The hydrochars presented higher ignition temperature and average combustion rates compared with raw coal. The hydrochar generated from co-HTC at 250 °C showed the best combustion performance due to the enhancement of air contacting and transformation, which was attributed to its porous structure, smaller uniform particle, and relative higher surface area. The activation energy of hydrochars was increased at the ignition stage while was decreased at the combustion stage according to the kinetic analysis. The fusion temperature was increased resulting from the removal of alkali and alkaline earth metals (AAEMs) during the co-HTC process. From the perspective of waste-to-energy, the co-HTC of high-alkali coal and PVC seems to be a feasible solution to improve combustion and slagging characteristics.