Kinetic Models for Coal Hydrogasification and Analyses of Hydrogasification Characteristics in Entrained-Flow Gasifiers

Coal hydrogasification (CHG) is a promising technology for clean and efficient coal utilization. However, the kinetic mechanism of CHG has not been fully understood, and multidimensional numerical simulations of CHG in entrained-flow gasifiers are still rarely reported. To evaluate and optimize hydrogasification parameters in an entrained-flow-bed gasifier, it is necessary to develop a reasonable CHG kinetic model and carry out the corresponding numerical simulations. In this work, a CHG kinetic model, including five homogeneous reactions and three heterogeneous reactions, is established. Thereinto, for the heterogeneous reactions, a novel combined random pore and shrinking-core model with pressure correction (CRPSC–PC) is put forward to predict the char–gas reaction process. When the CHG model is set up, it is then loaded to the commercial computational fluid dynamics (CFD) package, Fluent, via the user-defined function (UDF), and the simulation results are validated against literature-available experimental data for entrained-flow coal hydrogasifiers. Good agreements between the simulation results and the experimental data are detected, which indicates that the model is reliable and can be used to predict the effects of different operating parameters on entrained-flow CHG. Finally, the CHG properties in the cylindrical entrained-flow gasifiers are analyzed on the basis of the experiments reported in the literature, and the CH4 concentration in the gasification product is found to increase with the increasing H2O concentration of the gasification agent, the increasing inlet temperature of the gasification agent when the H2O concentration is high, and the increasing gasification pressure when the H2 concentration is high.