Simulation Of Combustion And NOx Formation Process On 1900t/h Boiler

About 67% of the Nitrogen oxides (NO_x), one of the most important emissions, are generated by burning coal. In order to reduce emissions and improve thermal efficiency of the boiler, the efficient ways for using coal are more and more important. NO_x emission control has become a major issue in thermal power plants. Therefore, the study of NO_x formation mechanism and control methods during the combustion process has practical significance in enhancing economic development and improving ecological environment.The flow and combustion characteristics of a 1900t/h pulverized coal boiler are studied to analysis the NO_x formation process. According to its structure and the flow characteristics, the furnace is divided into five blocks, namely the burner block, the block of upper part of the burner, the block of lower part of the burner, the furnace corner block, and the horizontal flue block. Because speed and temperature of fuel and products in the burner block change sharply, the mesh in this block is quite tense; In the block of lower stage of the burner and the horizontal flue block, the mesh changes gradually to loose; the mesh in corner block is tense. The direction of grid lines in the burner block is consistent with the direction of pulverized coal jet, which can reduce false diffusion in the simulation. Realizable k ?εmodel is used for turbulent gas flow; the eddy dissipation concept (EDC) model coupling detailed chemical reaction mechanism is used for gas turbulent combustion modeling; stochastic model is used for the flow of coal particles; devolatilization process is modeled by two competing reaction model; and P1 radiation model is used for the calculation of radiation heat transfer.By choosing the above models, the flow and combustion process and the process of NO_x formation are simulated. The comparison of NO_x concentration at the exit of the boiler between the actual testing results and the simulating results shows that this simulation method can reveal the combustion and NO_x formation characteristics accurately. Simulation results also show that the concentrations of some species are very important for NO_x formation. This microcosmic analysis method provides a good theoretical foundation for the control and systematic optimal design of NO_x emission.