CFD modeling for coal size effect on coal gasification in a two-stage commercial entrained-bed gasifier with an improved char gasification model

Computational fluid dynamics (CFD) modeling of coal gasification in an E-Gas™ gasifier was conducted with an improved char gasification model using commercial code, ANSYS FLUENT 14.0, in order to study the effect of the coal size on the gasification performance. The CFD modeling was carried out by solving the three-dimensional, steady-state Navier-Stokes equations with the Eulerian-Lagrangian method. Gas-phase chemical reactions were solved using the finite-rate/eddy-dissipation model. In order to solve char gasification reactions, the random pore model with bulk and pore diffusion effects was considered via a user-defined function (UDF). For each coal size, the species mole fractions, exit gas temperature, carbon conversion efficiency, cold gas efficiency, and distributions of the gas temperature and species in the gasifier were calculated through modeling. The CFD results were reasonable in terms of the species mole fractions and the temperature at the exit as confirmed through a comparison with the operating data of the Wabash plant. The carbon conversion efficiency and cold gas efficiency were maximized with a coal size of 100 μm.