Numerical simulation on pulverized coal combustion and NOx emissions in high temperature air from circulating fluidized bed

High temperature air combustion is a prospecting technology in energy saving and pollutants reduction. Numerical simulation on pulverized coal combustion and NO_x emissions in high temperature air from circulating fluidized bed was presented. The down-fired combustor, taken as the calculation domain, has the diameter of 220 mm and the height of 3000 mm. 2 cases with air staging combustion are simulated. Compared the simulation results with experimental data, there is a good agreement. It is found that the combustion model and NO_x formation model are applicable to simulate the pulverized coal combustion and NO_x emissions in high temperature air from circulating fluidized bed. The results show that there is a uniform temperature profile along the axis of the down-fired combustor. The NO_x emissions are lower than those of ordinary pulverized coal combustion, and the NO_x emissions are 390 mg/m³ and 352 mg/m³ in Case 1 and Case 2, respectively. At the range of 300–600 mm below the nozzle, the NO concentration decreases, mainly resulting from some homogeneous reactions and heterogeneous reaction. NO concentration has a little increase at the position of 800 mm below the nozzle as the tertiary air supplied to the combustor at the position of 600 mm below the nozzle.