Structural Optimization And Analysis Of The Aggregate Drying Pulverized Coal Burner

The burner is one of the key equipments for drying and heating of the aggregate.At present,the fuels used in the burner include light oil,heavy oil,coal,natural gas and coal water slurry,etc..If the pulverized coal is used as the fuel of the burner,the running cost of the aggregate drying can be effectively reduced.However,the combustion efficiency of pulverized coal is not high.In order to improve the combustion efficiency of pulverized coal burner,the analysis and optimization of the structure of the pulverized coal fired burner are performed in this paper.The aggregate drying process requires a certain amount of heat,which is supplied by the burner.The combustion of pulverized coal is a complex physical and chemical reaction with turbulent flow,coke combustion and thermal radiation etc..It is a prerequisite to construct a simplified mathematical model for the internal flow field of pulverized coal burner.The influence of the structure parameters on the combustion efficiency of pulverized coal burner is analyzed by Fluent software based on whether the coke is completely burnt.Then,the structural optimization variables of pulverized coal burners are determined and optimized by response surface methodology.The researches are as follow:1.In order to establish a simplified mathematical model for the dynamic field of pulverized coal burner,the combustion process of pulverized coal is analyzed on the basis of the requirements of the aggregate drying process.Using the standard k-? model to describe the turbulent flow in the combustion process of pulverized coal and using P1 model to describe the phenomenon of thermal radiation.Choosing the particle stochastic trajectory model to describe the discrete phase and choosing the constant model,the eddy dissipation model and the kinetics/diffusion-limited model to describe the volatile devolatilization,gas phase turbulence combustion and char combustion in the combustion process of pulverized coal.2.The influence of structural parameters of pulverized coal burner is analyzed based on the combustion effect of coke.The results of numerical simulation show that the straight length,the radius,the inlet diameter of primary air,the front cone angle,the rear end cone angle,the inlet diameter of tertiary air and the inlet size of secondary air affect the combustion efficiency of pulverized coal burner with varying degrees.3.Determining the optimization variables and the optimization target of the pulverized coal burner and optimizing the structural parameters of the pulverized coal burner by response surface method.The straight length,the radius,the inlet diameter of primary air,the front cone angle,the rear end cone angle,the inlet diameter of tertiary air and the inlet size of secondary air are served as optimization variables and the least amount of CO produced by incomplete combustion of coke is taken as the optimal target.Box-Behnken Design response surface was established to optimize 7 structural parametersby grouping.Then,the results show that when the straight length of pulverized coal burner is 1.02 M,the radius is 0.5m,the inlet diameter of primary air is 244 mm,the front cone angle is 59.5 degrees,the rear end cone angle is 30 degrees,the inlet diameter of tertiary air is 150.5mm,the inlet size of secondary air is 25 mm,the generation of CO is the least and the combustion efficiency is the highest.The research results will provide theoretical basis for the structure design and improvement of pulverized coal burner.