Numerical Simulation Of Combustion In High-Temperature Shaft Kiln For Sintered Corundum And Optimization Of Lining Structure

As the main thermal equipment for the production of calcining corundum,high temperature shaft kiln has many problems in the production process,such as high energy consumption,uneven product quality,easy destruction of furnace linings and easy breakages of alumina green bodies.Due to the high temperature and harsh working conditions in kiln,Conventional experimental methods cannot be used to carry out the research directly.So,in this paper,the combustion of CH₄ in kilns was studied via numerical simulation,the factors affecting of temperature distribution,energy consumption and product quality were analyzed,and thermal process parameters,burner arrangement and particles packing styles were optimized.The heat transfer calculation and vibration modal analysis were carried out with changing the lining structure.The main factors affecting of the energy consumption and lining life of kiln were studied,and the lining material and lining structure were optimized designed.According to the simulation of heat transfer and vibration mode of the furnace lining,the lining materials and structure were optimized.Lastly,the critical stress of particle breakage was studied by experiment and numerical simulation,which offered guidance for the design of heating and cooling curves.The results showed that:?1?When the ratio of CH₄ and primary air was 1:9,the temperature in kiln was highest,while the ratio was in the range of 1:12 and 1:13,the temperature distribution was uniform,and the value was about 1960?,which was suitable for sintering corundum calcination.In high temperature shaft kiln,the excess air coefficient increased from 6.9 to 12.2.With the increase of cooling air volume,the combustion degree of methane was not promoted,but the temperature in the kiln gradually decreased.When the burner on the vertical downward angle was 30°,the temperature distribution was in the main range of 1800¹930?on the calcine zone,which was suitable for alumina calcination,the temperature distribution was uniform too,which beneficial to calcine uniform quality of products.Changing particle diameters and particle gradations would affect the porosity and resistance coefficient.With the increase of the particle diameter and porosity,the flame height of decreased gradually.?2?Lining insulation was best when aluminum silicon castable A were used as the permanent lining layer.The highest temperature of the outer wall was approximately58?and the lowest temperature was about 45?.The natural frequency of furnace lining can be improved by using u-shaped ring plate,which enhanced the anti-vibration performance of furnace lining.Moreover,the anti-vibration performance of u ring board with spacing of 2.4 m was the best.?3?According to the results of the experiment and numerical simulation,the limit temperature of alumina green body breakage was 380?and the critical stress at this temperature was about 40 MPa.Therefore,the heating rate of alumina particles could not be too fast.Corundum particles did not breakdown when the temperature difference was 680?and the simulation results showed that the maximum thermal stress of the alumina particles 954 MPa under this condition.This meant that the strength of corundum particle was very high and they could be cooling fast and discharging with a high rate.