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.
Supercritical water gasification is a promising technology for pollution treatment and syngas production from biomass. The produced gas is composed of hydrogen, carbon dioxide, methane, carbon monoxide and traces of ethane and other light hydrocarbons. This work aims to give a comprehensive experimental study of the supercritical water gasification of glycerol using a full factorial design of experiments (DOE). The effect of five factors, namely: temperature [458 C-542 C], residence time [40-90 min], pressure [23-27MPa], initial concentration of glycerol [10-19wt%] and KOH catalyst quantity [0.60-1.475 wt%], were investigated on several responses such as the gasification efficiency (GE), syngas composition and lower calorific value (LCV) of the produced gas. First order mathematical models correlating each considered response in terms of the considered factors were developed and validated. Also, the significance of the factors effect was validated using analysis of variance. The results showed that the produced gas composition and quality were strongly influenced by temperature and initial concentration. The largest gas production was detected at a temperature of 542 C, a residence time of 40 min, a pressure of 27 MPa, a concentration of 10 wt% glycerol and a KOH catalyst percentage of 1.475 wt%.
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