A comprehensive CFD combustion model for supercritical CFB boilers

A combustion model of a large-scale supercritical circulating fluidized bed (CFB) boiler was developed for comprehensive computational-fluid-dynamics analysis. The model incorporates gas–solid hydrodynamics, coal combustion, heat transfer on heat exchange surfaces in the furnace, and heat transfer between furnace and working medium in the heat transfer tubes. In simulating the dense and dilute phases in the furnace, the gas–solid hydrodynamics is based on the Euler–Euler model and energy-minimization multiscale drag model. Coal combustion entails evaporation, devolatilization, char combustion, gas homogeneous reaction, and pollutant emission. The coefficient of heat transfer between gas–solid and the waterwall is estimated using the cluster renewal model, and for radiation, the discrete ordinate model is used. Moreover, thermohydraulic processes in the membrane wall are also included in the heat transfer process. The model was successfully applied in simulations of a 350-MW supercritical CFB boiler. Detailed distributions of solids concentration, oxygen, heat flux, and working medium temperature in the boiler furnace are presented.