Hydrogen-rich gas production from hydrochar derived from hydrothermal carbonization of PVC and alkali coal

Abstract

This work targets to produce hydrogen-rich syngas by steam gasification of hydrochars obtained from co-hydrothermal carbonization (co-HTC) of polyvinyl chloride (PVC) and alkali coal. Hydrochar properties were assessed in terms of ultimate analysis, proximate analysis and the content of typical elements. The syngas, tar and char properties were investigated to explore the steam gasification performace of hydrochars. The co-HTC facilitated the destruction of the hydrophilic groups based on the O/C atomic ratio. The co-HTC increased the yield of H2 and CH4, while the CO2 yield was concurrently reduced. A relative high H2/CO ratio of around 1.65–3.96 was achieved when gasified hydrochar under the various temperature. This temperature was supposed to be an acceptable operational window for yielding H2-rich syngas. The catalytic effect of alkali and alkaline earth metals (AAEMs) on H2 production was weakened due to the AEEMs removal during the co-HTC, while the H2 production could be remedied by the PVC addition. The evolution of poly-aromatic hydrocarbons (PAHs) convinced the event of primary or secondary tars transformed into the tertiary tar. The rich pore structure of char indicated that char have good potential in adsorption, and the adsorption experiment of malachite green confirmed this point of view.These findings will offer comprehensive data on the coal upgrading and hydrochar gasification.