Numerical Simulation Study on Interaction and Burnout Characteristics of Coal Blending Combustion in a 200 MW Tangential Firing Boiler Under O2/CO2 Atmosphere

A numerical simulation is conducted to investigate the interaction and burnout characteristics of mixed coal under O2/CO2 atmosphere in a 200 MW tangential firing boiler. Multiple models are utilized to simulate the flow and combustion processes inside the furnace, and a three-dimensional full-furnace model is constructed using an improved Weighted-Sum-of-Gray-Gases (WSGG) model. Using two types of coal and their mixed coal, the combustion of mixed coal under four O2/CO2 atmospheres is examined. Results show that there exists a significant interactive effect of promoting ignition and inhibiting burnout between difficult-to-ignite coal and easy-to-ignite coal. Increasing the proportion of easy-to-ignite coal helps improve the ignition performance of mixed coal. With a high proportion of easy-to-ignite coal, the oxygen-grabbing ability is enhanced. Increasing the inlet oxygen concentration can facilitate coal ignition and effectively enhance the burnout rate of difficult-to-ignite coal, mitigating the adverse effects of burnout inhibition. Among five typical oxidant-stream distribution methods, the positive pagoda oxidant-stream distribution can satisfy the combustion requirements of each layer, achieve relatively high burnout rates for difficult-to-ignite coal and mixed coal, and demonstrate the optimal comprehensive combustion performance. The findings can provide valuable references for optimizing oxygen-enriched combustion in boilers, thereby promoting the sustainability of coal-fired power generation.