Co-hydrothermal carbonization of polyvinyl chloride and lignocellulose biomasses: Influence of biomass feedstock on fuel properties and combustion behaviors

Co-hydrothermal carbonization (co-HTC) of lignocellulose biomass (LB) and chlorinated waste could produce value-added co-hydrochar while simultaneously removing inorganic metal salts and organic chlorine to the liquid phase. However, there is a lack of understanding of the influence of LB feedstocks on the fuel properties and combustion behaviors of co-hydrochars. Therefore, co-hydrochars derived from co-HTC of pine, bamboo, corncob, wheat stalk, and corn stalk with polyvinyl chloride (PVC) at the mass ratio of 9:1 under 260 °C for 30 min were tested. PVC facilitated the hydrolysis, dehydration, and polymerization of LB compositions (hemicellulose, cellulose, soluble lignin, and insoluble lignin). In turn, these LB compositions could prevent PVC aggregation and promote PVC substitution. Hydrochar fragments could coat the PVC surface and hinder its hydrolysis. Interactions between LB compositions and PVC improved the fuel properties and combustion behaviors of co-hydrochars derived from bamboo, corncob, wheat stalk, and corn stalk while decreasing the fuel properties and combustion behaviors of co-hydrochar derived from pine (HC-PPE). Except for HC-PPE, the fuel ratio (fixed carbon/volatile matter) of co-hydrochars increased to 0.90–1.18 and their HHVs reached approximately 17.5–32.45 MJ/kg without an increased risk of chlorine corrosion. The combustion of co-hydrochars was easier and more stable due to their higher ignition and burnout temperatures and lower activation energies. These findings provide comprehensive knowledge of the LB feedstocks influence on fuel properties and combustion behaviors of co-hydrochars, which would contribute to the cost-effective use of LB and chlorinated wastes.