CFD modelling of air-fired and oxy-fuel combustion in a large-scale furnace at Loy Yang A brown coal power station

This is a computational fluid dynamics (CFD) modelling study developed to investigate the Victorian brown coal combustion in a 550MW utility boiler under the air-fired and three oxy-fuel-fired scenarios. The air-fired firing case was modelled based on the real life operating conditions of Loy Yang A power plant located in the state of Victoria/Australia. This study of oxy-fuel combustion in a large-scale tangentially-fired boiler is important prior to its implementation in real-life power plant. The multi-step chemical reaction mechanisms were carried out on the pulverized lignite particles. The simplified approach of the chemical kinetics has been modelled to calculate the fuel and the thermal NO formation. The predicted results showed a reasonably good agreement against the measured data. [Display omitted] ► A CFD model is developed to investigate the Brown coal oxy-fuel-fired in a 550 MW utility boiler. ► This oxy-fired study in a large-scale boiler is important prior to its implementation in a real-life. ► A noticeable decrease in the NOx formation were observed under all oxy-fuel combustion scenarios. ► O2-enriched atmospheres of oxy-fuel-fired cases showed slight increase in the carbon burnout rate. Oxy-fuel combustion technique is a viable option to reduce several types of greenhouse gases (GHGs) emissions from the pulverized coal (PC) combustion systems. In this paper, a computational fluid dynamics (CFD) modelling study has been developed in order to investigate the Victorian brown coal combustion in a 550MW utility boiler under the air-fired (reference case) and three oxy-fuel-fired scenarios. The reference firing case was modelled based on the operating conditions of Loy Yang A power plant located in the state of Victoria, Australia. While Chalmers’ oxy-fuel combustion approach was selected for the present oxy-fuel combustion simulations, which referred to as OF25 (25vol.% O2), OF27 (27vol.% O2), and OF29 (29vol.% O2). User-defined functions (UDFs) were written and incorporated into the CFD code to calculate the following mathematical models: the PC devolatilization, char burnout, multi-step chemical reactions, mass and heat transfer, carbon in fly-ash, and NOx formation/destruction. A level of confidence of the CFD model was achieved validating four different parameters of the conventional combustion case, as well as the previous preliminary CFD studies that conducted on a 100kW unit firing propane and lignite under oxy-fuel combustion environm