3D CFD simulation of a 250 MWel oxy-fuel boiler with evaluation of heat radiation calculation

Abstract

The oxy-fuel process is a promising technology for capturing carbon dioxide from power plants. The fuel, in this case coal, is burned with pure oxygen instead of air in the oxy-fuel process. Since combustion with pure oxygen results in very high temperatures, flue gas must be recirculated and returned to the combustion chamber to lower and control the combustion temperature. This in turn leads to significantly higher concentrations of carbon dioxide and water vapor in the flue gas of the power plant boiler compared to the regular air-fired process, which result in increased radiant heat transfer to the evaporator tubes along the combustion chamber walls. Efficient models are available that can be applied to the numerical simulation of combustion chambers. A widely used model is the Weighted Sum of Gray Gases Model (WSGGM).In this work, the combustion chamber of an oxy-fuel power plant on a demonstration scale with an electrical output of 250 MWel was simulated to compare the results of different gas and particle radiation models. The gas radiation was modelled with the different WSGG model formulations. In addition, the influence of particle radiation was investigated. Therefore the emissivity of the particles were correlated to experimental data. The results corresponds in all cases with the output design of the power plant. The combustion exit temperature is slightly over-predicted for all models and particle properties. It has shown that the particle radiation has a strong influence on the heat wall flux in the burner region where the particle load is high.