Experimental And Numerical Analyses On Thermal Dynamic Characteristics And Flue Gas Emissions In A Rotary Kiln

Rotary kiln is a kind of important industries equipment.In order to reduce surface heat loss and pollution gas emissions,both experimental and numerical studies are performed to obtain relationship between the thermal dynamic characteristics and flue gas emissions of the rotary kiln and their affecting factors in this paper.The heat transfer characteristics of rotary kiln are experimentally studied,and the methods for reducing polluting gas emissions are provided.A three-dimensional numerical model with ANSYS software is set up to research the fluid flow,combustion and gas composition of rotary kiln under different working conditions.The main work is as follows:1.The experimental scheme is designed and the experimental platform is built,and the performance of the rotary kiln is set up.The shell temperature,coating thickness and O2,CO,CO2,NO,NO2 emissions of the kiln were measured,which show in field thermal dynamic characteristics and flue gas emissions of the rotary kiln.In the same time,the error analysis of the experimental data has confirmed the reliability and accuracy of the experimental data.2.The physical model of the Rotary Kiln was established,the model is validated by grid independence,the appropriate number of mesh have been determined.The appropriate solver settings and reasonable boundary conditions are set up.The thermal dynamic characteristics of rotary kiln under different working conditions are studied by numerical simulation method.Numerical simulation results presented reasonable agreement with experimental data.Results indicate that the burner structure has effects on the coal combustion and flue gas convection.Fugitive constituent of coal,pulverized coal concentration,excess air ratio and oxygen content can influence the characteristics of the combustion and heat transfer processes.Numerical simulation presents that the high-temperature combustion zone both gradually move toward the kiln hood with the increased fugitive constituent or concentration of coal powders.What's more,as the increase of excess air coefficient,the larger high-temperature combustion zone gradually moves toward the back-end of kiln.In addition,the burning position gradually moves toward the kiln hood as the oxygen proportion increased,3.The gas composition of rotary kiln under different working conditions is studied by numerical method.Results show that the O2 emissions of the studied kiln is high,in the same time,the CO emissions is low,which indicate the O2 is enough for the combustion.The NO emissions can be reduced by controlling the fugitive constituent of coal,pulverized coal concentration,excess air ratio and oxygen content.With the increased fugitive constituent of coal and excess air ratio,the NO emissions are gradually increased.With the increased oxygen proportion,the NO emissions firstly increases and then decreases.What's more,as the increase of concentration of coal powders,the NO emissions firstly decreases and then increases.