Technical Renovation Design Of A Rare Earth Production Line With Fluorine Waste Gas Treatment System

China is one of the few industrial giants in the world,and it is also one of the largest countries in the world with the largest reserves of rare earth resources and one of the largest countries in the world.The rough development of the rare earth industry has led to the purification effect of flue gas in the production process of rare earths has not been very satisfactory.In the new century,China has proposed a path of sustainable green development and accelerated ecological civilization construction,requiring industrial pollutants to meet emission standards.Therefore,this study has carried out detailed research on the removal and purification of fluorine-containing pollutants in the exhaust gas produced by the rare earth industry.This paper has carried out a detailed analysis of the production process of a rare earth production line in Jiangxi Province.The source and composition characteristics produced.Then,it analyzes some problems existing in the process of exhaust gas treatment and purification of the original exhaust gas treatment system and proposes corresponding transformation plans.Finally,after the construction of the renovation plan,the on-site operation and commissioning will be carried out to analyze the transformation effect.In response to the retrofit design of the exhaust gas treatment system,the following conclusions were drawn:1)Fluorine-containing exhaust gas emissions from rare earth electrolytic smelting have the characteristics of low emission rate and high temperature.Due to the demand for processes in rare earth electrolysis production,the design of the side suction hood is higher than that of the upper type.It can effectively improve the absorption efficiency of exhaust gas.After the design of the side-by-side suction hood,the dust and fluorine-containing waste gas in the production workshop were greatly reduced,and the collection rate of the exhaust gas reached 99%.The concentration of dust and fluorine compounds in the workshop and plant area are within the standard values of the "Rare Earth Industrial Pollutant Emission Standards".2)For the exhaust gas generated by rare earth electrolytic smelting,it is more suitable to adopt the method of lengthening the lower gravity settlement roadway than the bag type dust removal method.The down-grid gravity settlement roadway can not only achieve a certain dust removal effect,but also greatly reduce the loss of the exhaust gas pressure of the power consumption pipeline.3)The statistic values of dust and fluoride in the exhaust gas from the original first-stage washing and spraying tower are 56.02 mg/m3 and 4.65 mg/m3,and the compliance rates are 31.43%and 57.14%,respectively.The exhaust gas purification effect is not satisfactory.Through design,the spray tower is designed as a two-stage spray rinsing,the first stage is 5L/s water leaching,the second stage is 5L/s lime water leaching;after the construction,the current debugging monitoring uses the second stage.In the way of spraying,the dust concentration in the exhaust gas is 30.02 mg/m3 and 3.16 mg/m3,and the compliance rate is 100%.The design can ensure the purification effect of fluorine-containing pollutants in the electrolytic waste gas.4)The original spray wastewater treatment has the problems of poor treatment effect and large amount of wastewater;the neutralization sedimentation tank is added through design modification,and additional lime powder is added to the wastewater to increase the sedimentation effect of the pollution in the wastewater,and the wastewater is precipitated in the sedimentation tank.After stratification,the supernatant is circulated to the spray tower for use and the sediment is centrifuged for dewatering.5)For the overall exhaust gas treatment system commissioning and monitoring,it is calculated that this transformation can reduce the emission of fluoride by 0.21 tons and dust by 4.62 tons per year,and the emission reduction rates are 18.52%and 35.81%;respectively.The pollutant emission reduction effect is remarkable.6)The modification of the exhaust gas treatment system has produced certain economic and environmental benefits.The fluorine-containing compounds in the workshop and the plant area are significantly reduced.The collection of waste gas dust has certain economic benefits through recycling.In addition,the design optimization the electric energy consumption of the exhaust gas treatment system can save 2,953.28 RMB per day.