Fate of sodium and chlorine during the co-hydrothermal carbonization of high-alkali coal and polyvinyl chloride

Abstract

This paper offered a synthetic co-hydrothermal carbonization (co-HTC) process to remove the sodium and chloride from high-alkali coal and polyvinyl chloride (PVC) to address the issue of contamination caused by high-alkali coal and chlorinated wastes. This work examined the effect of the mass ratio of PVC to coal (Rp/c) ranging from 0 to 0.20 (g/g) and the co-HTC temperature ranging from 225 to 300 °C on the dechlorination efficiency (DE), the sodium removal efficiency (RE), and the higher heating value (HHV) of hydrochar. Both of the temperature and Rp/c have noteworthy effect on the improvement of DE and RE in the co-HTC process. In this process, the temperature and Rp/c have significant effect on the morphology of hydrochar. Cracks on the surface of hydrochar became more visible with the increase of Rp/c, which could benefit to remove sodium ions from coal matrix. The co-HTC process was conducive to the improvement of HHV. The co-HTC process is cost-effective because sodium and chloride were removed from raw materials simultaneously without chemical additives. Thus, this work presents an innovative insight into the technological development of waste-to-energy and high-alkali-coal cleaner production.