Supercritical water gasification of hydrothermal char

In this work samples of HTC char deriving from corn silage were gasified in batch micro-autoclaves at supercritical conditions (400°C, 30 MPa). Residence times between 1 and 5 hours were considered. Reactors made of stainless steel and Inconel® 625 were used to investigate over the influence of the reactor material. Gas yields and composition were determined, as well as solids production. Results showed gas yields around 20% wt., whereof 25% wt. represented by combustible compounds (hydrogen and light hydrocarbons), can be achieved. Finally, solid char deriving from the process was observed through SEM microscopy after every hour of reaction. This allowed observing that SCWG char forms small spherical structures sticking on the HTC char and helped in understanding the mechanism involved in the gasification process.