Numerical Simulation Research Of Nox Reduction By Fractional Combustion In 6000TBD Precalciner

With the increase of cement demand year by year,the scale of cement production line is expanding day by day.Aim at the precalciner in the cement production line with the scale of 6000 TPD and above,available for reference and the actual operating data is relatively small.Numerical calculation is used to predict the distribution and motion of flow field in the precalciner,it can provide detailed and reliable operating parameters for technicians.Therefore,it is necessary to find an appropriate calculation method to simulate the internal flow field in the precalciner in large-scale cement production line.Fluent software is used in this paper to simulate the gas-solid coupling reaction process and NOx reduction process in the precalciner by using the method of coupling calculation model combine with UDF.Specific work and research results are as follows:The coupling calculation model suitable for the working condition is established for precalciner in 6000 TPD cement production line.For the gas-solid multiphase flow model,the Euler model is used.The standard k-? model is used in the turbulence model and the P-1 model is used in the radiative heat transfer model.For the combustion of natural gas fuel,a finite rate / eddy dissipation model is used.For the simulation of the decomposition reaction of raw material,the heterogeneous component transport model is used.According to the design parameters,the geometric model of the basin of precalciner is built by using Pro/E.The hexahedral mesh division of the basin is completed by using ICEM CFD with a variety of meshing technologies.The boundary conditions of the basin are set up properly on the basis of satisfying the grid independence.The heterogeneous reaction rate model of Fluent has been secondary developed by using UDF to realize the import of custom raw material decomposition reaction rate.The calculate results of distribution of velocity field,temperature field,mixture field and the result of raw material decomposition are analyzed with actual working condition.The simulation results are compared with the actual measurement results,and the accuracy of the simulation results is verified.At the same time,it also showsthe reliability of the coupling calculation model and calculation method used in this paper.The NOx reduction process in the precalciner was simulated on the basis of gas-solid coupling flow field.The correctness of the NOx reduction model is verified by comparing with the actual measurement results.We improve the structure and operation parameters such as air separation ratio?burner installation height?burner installation angle and fuel staging ratio in fractional combustion.Compared with the original working condition,the reduction rate of NOx was increased by 14.6%,reaching a high of 45.1%,and a better NOx emission reduction effect was obtained after improvement.According to the simulation results under the new coupling model and the mechanism study of NOx reduction by fractional combustion,it can better guide the optimization design of precalciner,and have great value in engineering application.At the same time,it is of great significance for energy saving and emission reduction of cement industry.