Hydrogen Production by Coal Gasification in a Supercritical Water Fluidized Bed: Dynamic Modeling of an Industrial-Scale Reactor

This work presents two dynamic models of the supercritical water fluidized bed (SCWFB). One is a onedimensional (1D) model that only considers the upward flow of solid and fluid phases, and the other is a 1.5-dimensional (1.5D) model that uses "core-annular" construction. The two models are compared to obtain the differences. The error in the hydrogen molar fraction reproduced by the 1.5D model is 5.48%, which is lower than that of the 1D model. The bed temperature and hydrogen yield of the 1.5D model stabilized faster and reached higher steady-state values because of the particle backmixing. The effect of coal-to-water ratios, supercritical water temperature, and boundary conditions on gasification are studied based on the 1.5D model. The results show that high water-to-coal ratio and supercritical water temperature cause high bed temperature and shorten the stabilization time. The stabilization time of the bed temperature is 20 min when the jacket water flow rate is 80 kg/min, and the stabilized bed temperature is 690.9 degrees C, which is similar to those at a wall temperature of 500 degrees C. The dynamic characteristics of the reactor are important for the design, operation, and control in an industrial-scale system for supercritical water gasification of coal.