Insights into radiation property prediction for numerical simulation of pulverized coal/biomass oxyfuel combustion

The radiation property of flue gas in pulverized coal/biomass oxyfuel combustion distinguishes obviously from that in air combustion. Moreover, the particle emissivity and scattering factor can vary during its thermal conversion. Both phenomena challenge the accurate prediction of radiative heat transfer in coal/biomass oxyfuel combustion. As one solution to surmount this challenge, a new efficient exponential wide band model + particle radiation property model is proposed in this work. For validation, the proposed model is compared with other parallel models, and their predictions are compared against experimental data. It is found that the efficient exponential wide band model + particle radiation property model can give reliable predictions at different operating conditions. The maximum relative errors between the prediction and the experimental surface incident radiation are within 7% at the burner outlet and 2.5% at the peak point. Moreover, the iteration time consumptions are 0.55 and 0.87 s for the 0.5 MW case, and 35.45 and 35.66 s for the 600 MW case with the parallel radiation model and the proposed model. After validation, the feasibility and characteristics of the coal/biomass oxyfuel co-combustion process in a 600 MW tangentially fired boiler are predicted. It is found that the boiler can run stably and the CO2 mass fraction in the discharged flue gas can be around 90%. A new efficient exponential wide band model plus particle radiation property model is proposed for application to pulverized coal/biomass oxyfuel combustion. The model is compared with other parallel models, and their predictions are compared against experimental data.