Engineering Optimization And Application Of Flow Field And Temperature Field In Vertical Rare Earth Fluorination Furnace

At present,one of the most important equipment for preparing high purity rare earth fluoride in industrial production is vertical rare earth fluoride furnace which is a typical high temperature gas-solid reactor.In the vertical rare earth fluoride furnace used in industrial production at present,the gas flow rate in the furnace is not uniform and the temperature distribution in the furnace is quite different,so the fluorination efficiency of the whole furnace in the vertical fluorination furnace is not high.In this paper,the computational fluid dynamics method is combined with ANSYS FLUENT software to study and analyze the flow field and temperature field in the vertical fluoride furnace to find out the structural defects and improve them.After improving the structural parameters of the existing vertical fluoride furnace,two improved structural furnace types are obtained.Through the analysis,the advantages of the two improved furnace types over the existing one are obtained.The specific work is as follows:(1)The mathematical and physical model of existing vertical fluoride furnace is established and the flow field and temperature field are solved by FLUENT software.At the same time,the data are processed by Origin software.The results show that there are more dead zone of gas eddy current in the existing vertical fluoride furnace.The results show that there are many eddy dead zones in the existing vertical fluoride furnace,the gas flow stagnation is serious,and the hydrogen fluoride gas can not flow quickly to the upper reaction zone to participate in the fluorination reaction.The temperature fluctuation in the furnace is relatively large,only the upper half of the furnace can reach the ideal temperature range of fluorination reaction,while the bottom of the furnace has a relatively large low temperature region,so the overall fluorination efficiency in the furnace is low.(2)Through analysis,it is concluded that the above-mentioned problems are caused by the defects of the inlet position,inner liner structure,charging plate structure and gas collector structure of the existing vertical fluoride furnace.After improving the above-mentioned structures,two improved structure furnace models are obtained.Through solving the flow field and temperature field of two kinds of improved structure furnace model and comparing with the results of the existing furnace shape,The results show that the gas eddy current phenomenon in the twoimproved furnaces is greatly reduced and the gas flow distribution is more uniform.At the same time,the temperature distribution in the two improved furnaces is more uniform.Under the same conditions,the temperatures above the second layer tray in the two improved furnaces are higher than those in the corresponding regions of the existing furnaces.(3)Since the initial temperature of the incoming gas is too low,there is still a low temperature region in the bottom region of the two improved structure furnaces.Therefore,the preheating temperature of the introduced gas is studied,and the furnace temperature distribution at the initial temperature of the five gases is performed.The comparative analysis shows that as the initial temperature of the gas increases,the lowest temperature in the furnace gradually increases,the average temperature in the furnace increases continuously,the temperature fluctuation gradually decreases,and the temperature distribution becomes more uniform.And the analysis shows that the initial temperature of the gas that can make the temperature of all the reaction zones in the furnace reach the ideal temperature range required for the fluorination reaction should not be lower than 705 K.(4)In actual production,the internal fluorination efficiency of two furnaces was measured and the curve of fluorination efficiency was plotted compared with that of the existing furnace.The results showed that when the inlet gas was not preheated,the fluorination efficiency curve was compared with that of the existing furnace type.The average fluorination efficiency of the two improved furnaces increased by 20.4% and14.9% respectively.The average fluorination efficiency of the two improved furnaces was increased by 39.4% and 36.1% respectively after preheating the gas into the furnace to 705 K.The improvement of fluorination efficiency is the largest in the furnace with improved structure,and the optimum optimization effect can be achieved in the furnace shape.