Supercritical water gasification of glycerol for Hydrogen production using response surface methodology

Supercritical water gasification is a promising technology for the treatment of wet biomass and hydrogen. In this work, supercritical water gasification of glycerol was carried out in mini autoclaves to conduct a hydrogen production optimization study, using the central composite design of experiments. The effect of five operating conditions on the production of syngas by supercritical gasification has been studied namely, temperature (400-600°C), residence time (5min30s-124min30s), initial concentration of glycerol (3,79-25,21% weight), pressure (20.21 MPa-29.76 MPa) and KOH catalyst quantity (0-2% weight). The results revealed that a high temperature and a long residence time are desirable for hydrogen production and gasification efficiency, the temperature is the most positive effect on both responses, and the presence of potassium hydroxide as a catalyst has a considerable effect on hydrogen production. However, a long residence time is not necessary when handling at high temperature. Also, the increase in the initial glycerol concentration has a negative effect, while the pressure change has no significant effect. According to the models, a maximum of hydrogen produced and gasification efficiency are obtained when the operating conditions are temperature = 599.89°C, residence time of 60.7957 min, a pressure of 21.3 MPa for an initial glycerol concentration of 3.79 wt% and in the presence of 0.102 wt% KOH.