Radiation Simulation for Air and Oxy-fuel Combustion using Computational Fluid Dynamics

Coal consumption is predicted to account for about 21% of the total global primary energy in 2040 and this continues to be a challenge for global warming and air pollution. Oxyfuel combustion is one of the leading options for carbon capture and storage (CCS) technologies to reduce the impact on the environment. Initially this technology has been studied successfully on small-scale facilities but it needs to be developed for large-scale applications. CFD has been demonstrated to be a key tool for the development and optimisation of pulverised coal combustion processes and it is still an important tool for new designs and retro-fitting of conventional power plants for oxyfuel combustion. Radiation heat transfer plays an important role, influencing the overall combustion efficiency, pollutant formation and flame ignition and propagation. This thesis focuses on the radiation properties of the particles as well as gas property models on the overall influence of the prediction of the formation of NOx pollutants in pulverised coal combustion. The radiative properties of the particles are investigated with a focus on the effect of the optical properties and approximate solutions to determine the radiative properties, with different experimental data for the optical properties and approximate solutions being employed. The effects of the radiative properties on the radiative heat transfer are investigated in three dimensional enclosures for small and large-scale furnaces and implemented on a 250 kW pilot scale combustion for both air and oxyfuel conditions. The results from the study highlights the best selection for the particle properties for simulations in small and large-scale pulverised coal furnaces and employing radiation models for the gases and particles to improve the NOx predictions in pulverised coal combustion under air and oxy-fired environments.