Hydrogen production by sewage sludge gasification in supercritical water with high heating rate batch reactor

Sewage sludge gasification in supercritical water was studied with high heating rate batch reactor. Effect of temperature, pressure, residence time and catalyst were investigated. The hydrogen yield, gasification efficiency, carbon gasification efficiency and hydrogen yield potential were mainly affected by temperature. The maximum values of them reached 20.66 mol/kg, 73.49%, 61.16% and 41.34% without catalyst at 750 °C and 30 min respectively. The modified detailed kinetics indicated steam reforming, water-gas shift and pyrolysis promoted the formation of H₂ and CO₂ when temperature was ranged from 550 to 750 °C at the initial residence time. As residence time increased, the water-gas shift was dominant. Meanwhile, the formation of CO and CH₄ were inhibited when temperature and residence time increased. The addition of mixed catalysts promoted the three reactions and formation of hydrogen better at lower reaction condition. The mixed use of both catalysts could enhance the gasification and the formation of hydrogen better. The increased loading of RNi-Mo2 could enhance the formation of hydrogen better because the heterogeneous catalyst could promote steam reforming and alkali catalyst could promote water-gas shift reaction better.