Continuous Hydrothermal Gasification of Glycerol Mixtures: Autothermal Operation, Simultaneous Salt Recovery, and the Effect of K3PO4 on the Catalytic Gasification

Abstract

We have developed a continuous process for the catalytic hydrothermal gasification of wet biomass to synthetic natural gas (SNG). Salts contained in the biomass and released during the liquefaction step are continuously withdrawn in the supercritical salt separation step upstream of the catalytic reactor. The catalytic reactor is operated at temperatures of 400–450 °C and pressures of 25–35 MPa. In this article we provide a detailed description of the process and demonstrate the proof of concept as well as the process operation characteristics, based on a systematic study of the continuous gasification of aqueous solutions of glycerol with and without K3PO4 with simultaneous salt recovery. Glycerol was gasified efficiently to a methane-rich gas without the formation of tars or char. The gas composition corresponded to the thermodynamic equilibrium. The process could be operated in an autothermal mode, although the large surface-to-volume ratio and the imperfect insulation of the laboratory-scale reactor w...