Numerical investigation on gasification characteristics of irregularly-shaped coal particles in supercritical water for hydrogen production

The morphology of coal particles plays a crucial role in the supercritical water gasification (SCWG) of coal for hydrogen production, as it significantly influences both mass and heat transfer processes. Most existing studies assume coal particles to be regularly-shaped, typically spherical, with an invariant morphology of shrinking reaction front inside. In this study, we employ three-dimensional (3D) numerical simulations to investigate the temporal evolution of multi-species diffusion and heat transfer within irregularly-shaped coal particles undergoing gasification in supercritical water. Compared to the conventional shrinking core model, coal particles with variable reaction front morphology exhibit a reduction in average gasification rate ranging from 21.7 % to 34.1 %. Additionally, compared to spherical particles, the gasification rate of irregularly-shaped coal particles increases by 7.1 %–68.4 %. Furthermore, the average gasification rate is found to be inversely proportional to the 1.7th power of particle sphericity and directly proportional to the 0.13th power of 3D roundness. These findings provide theoretical insights for optimizing coal particle preparation to enhance the efficiency and cleanliness of coal conversion in SCWG for hydrogen production.