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Large eddy simulations (LES) are used in a CFD model to simulate air-and oxy-fired pulverised coal combustion in a 0.5 MWth combustion test facility. Simulations are carried out using two different burners, namely, a triple staged low-NOx wall fired burner and an IFRF Aerodynamically Air-Staged Burner (AASB). Non-gray radiation is considered in order to deal with the spectral nature of absorption and emission by high levels of combustion products in oxy-fuel combustion.Predictions using LES are compared with Reynolds-Averaged Navier-Stokes (RANS) calculations using variants of the k-ε model for turbulence and against available experimental measurements. The results suggest that LES can offer improvements over RANS in predicting recirculation zones and flame properties of the pulverised combustion systems investigated. Flame flickering frequencies from the LES simulations are calculated and validated against available measurements. The work presented demonstrates the potential importance of using LES turbulence models for coal combustion.

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a b s t r a c tOxyfuel combustion, where the fuel is combusted in a mixture of pure oxygen and recycled flue gases instead of air, is one of the leading options for carbon capture from coal-fired power plants. Accurate simulation of the operation of such plants is critical for successful development of the technology. A major challenge of such a simulation is how to account for the fundamental differences in gaseous physical and thermal properties; in particular the radiative and convective heat transfer coefficients.In this paper a combined CFD-process approach is developed whereby a detailed CFD model is utilised to represent the complex gas-phase combustion and radiative heat transfer to the furnace walls and the radiant section of the boiler. This is then combined with a full plant process simulation which includes modifications to the heat transfer components to account for differing gas compositions.The novel integrated calculations have been completed for air-firing and for oxyfuel under a range of conditions and a comparison reveals that there is a possible 'working range' of oxygen concentrations/ recycle ratios under which the distribution of heat transfer in the system is similar to air firing and hence the steam conditions can be controlled to set-point temperatures and flows.

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