LAUSR

Abstract The influence of water-soluble inorganic constituents on combustion of raw grape pomace (RGP) and its chars was investigated. Water leaching pretreatment was performed and the leached grape pomace (WLGP) and RGP samples were subsequently characterized by TGA to investigate the combustion under low heating rate. Then, the WLGP and RGP pyrolysis was carried out at slow (5 °C/min) and fast (120 °C/min) heating rates and the gas and char products were characterized. Finally, the combustion of RGP, WLGP, RGP chars and WLGP chars was analyzed in a drop tube furnace (DTF) to determine the influence of water-soluble inorganic matter on burnout and gas emissions. The water leaching pretreatment removed considerable amounts of K, B, Mg and P. The TGA results showed that the inorganic matter reduction negatively affected the combustion reaction rates, leading to a displacement to higher temperatures of ignition and burnout. Nevertheless, the DTF results showed no relevant effect on combustion efficiency between the RGP and WLGP samples. On the other hand, the pretreatment effect was pronounced during the WLGP chars combustion, in which the burnout of WLGP chars combustion was 30% lower compared to the RGP chars and 50% lower compared to the burnout obtained for raw samples. Additionally, the pretreatment affected the NO and CO formation, increasing the gas species concentrations during WLGP and WLGP chars’ combustion.