Numerical Simulation Of Low-NO_X Staging Combustion And Optimization Research In DD Prcealciner

Precalciner is not only a key heat equipment, but also an important optimized equipment to implement the low NOx technology in cement industry. In recent years, how to achieve energy conservation and emission reductions by using the theory or experimental method to optimization research of the precalciner's structure and process parameters has become a key problem in precalciner design. In the study, the numerical simulation method with combining qualitative and quantitative analytical way was used to study parameters of staging combustion in precalciner and optimization design of these parameters. Through research of raw real decomposition rate, pulverized coal burnout rate and NO reduction rate which can characterize performance of staging combustion to optimize parameters of staging combustion, what obtain significant referenced value for low NOx staging combustion technology in precalciner.In this paper, a numerical model of actual size precalciner which could produce6000tons of cement per day was built. Using commercial CFD software Fluent simulated physical-chemical processes in precalciner. In the simulation, the standard two k-ε model(using standard wall function to simplify the flow near the wall) is used, coal is modeled by discrete phase and random walk model, coal-vol volited in one-competing-rates and char combustion is controlled by kinetics/diffusion-limits. Raw meal decomposited in limit rates model. The finite volume method is used to discrete the differential equations. Using SIMPLE method solved. The simulations disclosed the information of flow, combustion, decomposition and coupling relationship among them in quantitily in precalciner. In addition, staging combustion is simulated, which included simulations by research of adding denitration coal-nozzle in conical part and changing air-staging way, proportion of air, coal and raw material, etc. And proceeded further optimization design by NO emission and raw real decomposition rate, etc. The main conclusions are as follows:(1) For DD-based6000t/d of decomposition of the model furnace is more accurate and more reasonable distribution of income flow. Temperature, the decomposition rate of the system concide with the actual production needs;(2) Research of the adding denitration nozzle in conical part shows that:when denitration nozzle and air-inlet form into parallel position, coal sending out angle from the nozzle is up of15degrees, installation height of the nozzle on precalciner is2m and coal proportion in the nozzle is20%, those are the best denitration nozzle working parameters;(3) Research of air-staging way shows that:when a pair new air-inlets and the original air-inlets form into parallel position and area of new air-inlets is half of the original air-inlets's is better staging way.(4) Research of proportion of the staging combustion shows that:result of coal-staging and air-staging at the same time is better air-staging only. When air proportion is7.78%and coal proportion is40%is better staging-combustion conditions;(5) Research of proportion of the staging raw material shows that:when proportion of raw material is50%is best working parameters.