Co-production of hydrogen and biochar from methanol autothermal reforming combining excess heat recovery

Abstract

This research conducted an innovative hydrogen and biochar co-production system via methanol autothermal reforming (ATR) combing excess heat recovery. Using the oxygen/carbon (O2/C) ratio, steam/carbon (S/C) ratio, and preheating temperature as the operating conditions for the hydrogen production, methanol conversion and hydrogen yield are in the ranges of 70.36–99.52 % and 1.44–1.98 mol∙(mol CH3OH)−1, respectively. The temperature of the gas product from ATR is between 300 and 500 °C. An H2 yield prediction model based on the decision tree equipped in MATLAB is established using the obtained experimental data. The torrefaction of spent coffee grounds (SCG) is integrated with methanol ATR, and the excess heat in high-temperature gas products is used as the heat source. Compared with raw SCG (18.20 MJ∙kg−1), the higher heating value of produced biochar can be up to 22.46 MJ∙kg−1, and the fixed carbon increases from 45.91 wt% up to 54.55 wt%. The contact angle also rises from 81.75° to 102.63°. Therefore, the integrated system not only enhances the energy value of biomass but also presents a dual-benefit strategy for sustainable biomass utilization and waste management, exemplifying waste and waste heat valorization.