Numerical Simulation Of Low NO_X Gas Burner

Heating furnace is an important source of NOx emission in refining and chemical enterprises.Excessive NOx emission will cause a series of environmental and health problems.The NOx in the flue gas of the heating furnace is mainly produced in the combustion process.The burner is the key equipment to determine the combustion condition of the heating furnace and the generation of NOx.Due to the complexity of the structure and combustion process of industrial burners,it is difficult to obtain detailed flame temperature and flue gas composition data from experimental research,while numerical simulation can provide detailed physical field distribution and composition information.Therefore,this paper will use the method of combining experimental verification and numerical simulation to study the NOx generation mechanism and the main influencing factors of the gas burner of the heating furnace,so as to provide guidance for the development of the new low NOx burner.Firstly,the single-hole blunt body burner is taken as the research object,and the reliability of the simulation scheme is verified by comparing the simulation data of gas diffusion combustion process with the experimental data under similar conditions with the industrial burner.The results show that using SSG turbulence model and WD1 methane combustion reaction mechanism to simulate gas diffusion combustion process can meet the requirements of engineering calculation.On this basis,the influence of operating parameters（different heat load,excess air coefficient,air temperature and air humidity）of single-hole blunt body burner was investigated.The results show that reducing heat load,lowering air temperature reduce the excess air coefficient when the excess air coefficient is small and increasing air humidity can effectively reduce NO production.Then,the influence of structural parameters（different orifice diameter,nozzle structure and orifice shape）of single hole and blunt body burner was studied.The results show that the NO generation can be effectively reduced by reducing the nozzle diameter,changing the circular nozzle into a plane nozzle,and changing the circular nozzle into a slit nozzle under the precondition of constant flow velocity of the nozzle.Finally,according to the simulation condition of the single-hole blunt body burner at 178 m/s,the generation of NO is analyzed in detail,and the conclusion was drawn that the thermal NO was mainly generated in the side with higher O₂ content in the high temperature zone.The wall of cylinder furnace with porous and complex gas burner was simulated.The simulation results of physical field and NO concentration under four working conditions were obtained by comparing the four working conditions of cylindrical furnace without furnace wall,full opening of furnace wall,bottom opening of furnace wall and plugging of furnace wall.The results show that the concentration of NO increases with the decrease of the opening ratio of the furnace wall.When the hole was blocked in the furnace wall,the NO content at the exit was the highest,which reached 7.23 mg·kg^-1.The results show that the reactants with faster reaction rate tend to react at the bottom of the flame,and the range of high reaction rate zone is small.The high reaction rate region of NO is wider than that of CH₄.