Steam gasification of hydrochar derived from hydrothermal carbonization of fruit wastes

Abstract

This study presents a numerical investigation of steam gasification of hydrochar derived from fruit wastes. Four fruit wastes, apple chip pomace, grape pomace, rotten apple, and apple juice pomace, were used as feedstocks. Aspen Plus was used to simulate the gasification process. The syngas composition, hydrogen to CO ratio (H2/CO), CO to CO2 ratio (CO/CO2), and heating value (HHV) of the resulting syngas were analyzed. Results show that hydrothermal carbonization (HTC) increases the CO and reduces the CO2 content of the syngas after gasification. Accordingly, H2/CO reduces, and CO/CO2 increases after HTC treatment. Hydrothermal treatment also improves the HHV of the syngas. The obtained HHV of syngas from hydrochar gasification ranged from 10.1 to 15.3 MJ/Nm3 depending on the process parameters. Additionally, effects of process parameters were studied. Increasing the steam to biomass ratio (SBR) leads to a higher H2/CO, enriching the syngas with hydrogen (up to 64.7 vol%). Higher SBR also lowers the CO/CO2 ratio due to the consumption of CO and a rise in CO2. HHV increases with increasing pressure, and hydrochars exhibit more changes in HHV than raw feedstocks. The reaction temperature contributes to an increase in the fraction of CO in the syngas (up to 39.6 vol%). Although hydrogen increased initially with temperature, a slight reduction was observed for the gas at elevated temperatures, reducing the H2/CO ratio and increasing the CO/CO2 ratio.