CFD & AMP Center
Department of Mechanical & Aerospace Engineering
West Virginia University
Oxy-coal combustion with flue gas recirculation is a promising technology intended to reduce the anthropogenic emissions of CO2 and other pollutants such as NOx and SO2 into the atmosphere. This technology is being implemented in existing air-based equipment, such as boilers and furnaces. Another unique application of oxy-coal combustion is the activation of chemical reactions using the very high temperatures that can be generated with char/O2/CO2 mixtures. This application entails an economical alternative to the electric arc furnace process for production of chemicals. In this application, the desired chemicals will be produced in the molten slag of the reactor. This reactor is currently being developed at WVU. It is an entrained flow reactor type with swirling flow for flame stabilization and flow of molten slag on the walls. In this work, a methodology for design is applied using a CFD model for turbulent combustion along with a model for slagging. The CFD model for turbulent combustion utilizes the Reynolds-averaged Navier-Stokes (RANS) approach for fluid flow, heat transfer, and turbulent-chemistry interaction. The multiphase character of the flow in the combustor chamber is considered using the Eulerian (gas phase) – Lagrangian (Particle phase) treatment. The interaction between continuous and discrete phase is taken into account by using source terms in the coupling equations for mass, momentum and energy. The slagging model is based on an integral approach of the boundary layer theory with modified properties for very high temperature conditions. The CFD model for turbulent combustion provides the inputs for the slagging model, such as boundary conditions and source terms. Different O2/CO2 atmospheres with different molar oxygen concentrations are taken into consideration. The validation process of the oxy-coal turbulent combustion phenomena is done using previous experimental measurements and CFD results. Preliminary results for the turbulent reacting flow field show a stable combustion process with a well-defined burner recirculation zone. Results for combustion of coal indicate that a complete coal devolatilization is attained, as well as a char burnout of 97% approximately. Results also suggest that the gas temperatures required for the activation of chemical reactions are obtained for O2/CO2 oxidant mixtures with molar oxygen concentrations higher than 50%.