[Objective] Xinjiang high-alkali coal offers low mining costs and stable supply, making it an attractive option for cost reduction in coal-fired power plants through co-firing. However, its high alkali content and low ash fusion temperature lead to severe slagging, limiting the engineering application of high -proportion co -firing schemes. To clarify the influence of blending ratio on combustion characteristics, NO x emissions and slagging behavior in a large -scale tangentially fired boiler, this study conduc ts numerical simulations. 

[Methods] A 660 MW supercritical tangentially fired boiler is taken as the object. A coupled gas-solid combustion and ash particle 2 deposition numerical simulation method is employed, integrating the Standard k -ε turbulence model, P1 radiation model, PDF gas-phase combustion model, and DPM discrete phase model with the stochastic trajectory model for particle tracking to establish a three -dimensional steady -state furnace model. Ash deposition probability is evaluated using the criti cal viscosity criterion with a threshold of 10 5 Pa· s. Grid independence is verified using four grid systems from 1.0 to 2.5 million cells, and the model accuracy is validated against field test data, with relative errors within 5% for furnace outlet gas te mperature, oxygen concentration and NO x emissions. Two Xinjiang coals, Hongyi and Honger, are blended with Menghun reference coal at mass ratios of 20%, 40%, 60% and 80%, respectively. The temperature field, species concentration field, NO x formation and w all slagging distribution under each condition are systematically analyzed. 

[Results] As the Xinjiang coal blending ratio increases, the flame center shifts upward, the furnace outlet flue gas temperature rises by 17~21 K, and the outlet oxygen concentration decreases monotonically. The CO concentration increases in the primary combustion zone but decays faster in the burnout zone, indicating a pronounced backward shift of combustion share. NOx emissions decrease significantly with increasing blending ratio , with the peak concentration in the burner zone dropping by 24%~35% and the furnace outlet reduction ranging from 19% to 26%. Hongyi coal, with a fuel nitrogen content of only 0.58%, exhibits lower NO x emissions than Honger coal under all blending ratios. Regarding slagging behavior, the alkaline components in Hongyi coal ash continuously react with the silica -alumina components of Menghun coal as the blending ratio increases, monotonically aggravating slagging. In contrast, Honger coal, containing 36.75% Fe 2O3, forms an optimal low -temperature eutectic composition at 40%~60% blending ratio, resulting in the most severe slagging; however, at 80% blending ratio, the high -iron ash dilutes this composition and weakens the eutect ic reaction, thereby alleviating slagging and exhibiting a non -monotonic trend. 

[Conclusion] Considering the trade-off among burnout efficiency, NO x emissions and slagging risk, the blending scheme with 60% Menghun coal and 40% Hongyi coal is recommended a s optimal. This scheme ensures controllable slagging, low NO x emissions and satisfactory burnout, providing a theoretical basis for safe and economical high-alkali coal co-firing in existing power plants.