Modeling the slag layer in solid fuel gasification and combustion – Two-way coupling with CFD

A steady-state model has been developed to describe the flow and heat transfer characteristics of slag that takes into consideration the contribution of the momentum of captured particles and the possibility of slag resolidification along the walls. The model also incorporates a criterion for particle capture or rebound. Captured particles flow with the local slag average velocity. Some of these particles may contain combustibles and they continue to burn at a different rate. To take this into account, a wall consumption submodel is proposed to predict a correction factor for the porous char consumption models. The slag flow model, along with the particle capture and consumption submodels are two-way coupled with a Computational Fluid Dynamics (CFD) of coal combustion, resulting in changing the discrete phase and temperature boundary conditions of the bulk flow simulations. The coupled CFD simulation shows that the wall traps about 56% of the coal particles fed to the combustor, while the wall temperature and heat flux to the wall are not significantly affected by the inclusion of a slag layer.