Numerical Study on Combustion Characteristics of Biogas Cocombustion in a 300MW Coal-Fired Boiler Furnace

To further explore cocombustion technology with biogas and coal, a series of numerical simulations have been carried out to analyze the effects of the cocombustion ratio xi, height of biogas nozzle H-GN, and tilt angle of burner theta(BN) on combustion characteristics in a 300 MW four-corner tangential boiler furnace. Three types of biogas are gasified from straw, sawdust, and raw wood when air serves as the gasification agent. The velocity field, temperature field, and NO emissions have been comprehensively analyzed when the values of xi, H-GN, and theta(BN) range, respectively, from 0.02 to 0.12, from 17.3 to 20.3 m, and from -15 degrees to +15 degrees. Results showed that the NO concentration at the furnace outlet monotonously decreased with xi. The injection of biogas reduces both the peak temperature of the entire boiler furnace and the NO concentration at the furnace outlet. The NO emission concentration decreases with the increased xi value for all types of biogases. The cocombustion with sawdust biogas indicates the least NO emission at a fixed cocombustion ratio. Furthermore, reducing the furnace height at H-GN = 17.3 m or titling down the burner at theta(BN) = -15 degrees contributed to a greater NO concentration at the furnace outlet.