A numerical study on gasification of a single char particle in supercritical water for hydrogen production

Supercritical water gasification technology provides a promising way for the efficient and clean utilization of coal. Char conversion in supercritical water is a complex coupled process of flow, heat transfer and reaction, and particle-scale study can provide important details for its in-depth understanding. A numerical work was conducted in this paper to investigate the influence of multiple factors on the gasification behavior of a single char particle in supercritical water. The results showed that the increase of temperature significantly benefited the char conversion and hydrogen production. Convection promoted the char gasification mainly by enhancing the heat transfer, and its improvement on effective mass transfer was quite limited. The existence of radiation is conducive to the char conversion, and cannot be ignored in some cases. The results derived from surface Damköhler number indicated that the gasification lied in kinetically controlled regime and tended to move towards diffusion controlled regime with larger inflow temperature, lower Reynolds number and larger particle size.