| This essay,based on current situation and main problem of mixed carbonate rare earth elements extraction and separation lines of Inner Mongolia Aerospace JinXia Chemical Industry Co,LTD whose annual capacity is 5000 tons,puts forward advice on the improvement on operational plan in the grades of separation lines' outlets between lanthanum and cerium,and the outlets settings between cerium and praseodymium,optimizing the operational plan of mixed carbonate rare earth elements extraction,and improving quality of separated products.In addition,in order to achieve quality control in finished and semi-finished products after separation,the analytic method of samarium,europium,and gadolinium feed concentration is improved;the gravimetric method of sulfate in the mixed rare earths liquid is exploited;ICP-AES of aluminum ion in Praseodymium-Neodymium Oxides is developed;the analytic method of finished and semi-finished products after separation is optimized.Main contents are as follows:1.The mixed carbonate rare earth elements extraction and separation lines of Inner Mongolia Aerospace JinXia Chemical Industry Co,LTD(JinXia Chemical Indurstry)of which annual capacity is 5000 tons adopts the extraction and separation technology with 88 cascades which usually produces lanthanum chloride liquid at the 8th outlet.But it leads the mass of liquid exceed the given standard,and does not accord with the requirement,because the liquid contains too much Na+?Ca2+?Mg2+and other non-rare earth impurities,which causes the liquid to agglomerate and difficulty in discharging.To address this issue,it is proposed in this paper to upgrade the residence time and the outlet grade from 8th to 12nd when processing lanthanum chloride liquid,through experiment examining the contents of rare earth and non-rare earth impurities in the liquids produced at each grade.Through this adjustment,the contents of non-rare earth impurities in the lanthanum chloride liquid is decreased--Na+ from 0.37%to 0.23%,and Ca2+ from 2%to 1%respectively.In addition,it achieves feeding smoothly in the process of concentration without clogging as feed in the boiler is in high density,and ensures that one boiler of feed can be concentrated within 24 hours and that the grade of lanthanum chloride concentrated products can reach 45%and above,which is 1 to 2%higher than before.2.In the 110-cascade mixed carbonate rare earth elements extraction and separation lines of JinXia Chemical Industry of which annual capacity is 5000 tons,the contents of Na+?Ca2+?Mg2+ and other non-rare earth impurities in the lanthanum-cerium liquid produced through the outlet of cerium-praseodymium separation line are too high because the setup of extraction tank's outlet is unreasonable.Furthermore,the partition between lanthanum and cerium does not satisfy the requirement when the raw material is the rare earth from the south of China(35%of lanthanum and 65%of cerium).Moreover,it also causes the feed is easy to agglomerate and difficult to be discharged in the subsequent process of concentration.To address this issue,it is recommended in this paper to increase the number of feed outlets of cerium-praseodymium separation line from 2 which are the 8th and 100th feed outlets originally to 3—the 8th,22rd and 100th outlets,through experiment determining the contents of rare earth and non-rare earth impurities in the liquids produced through outlet at each grade in the cerium-praseodymium separation line.Because of this optimization,the rate of purity of lanthanum and cerium produced at the 22nd feed outlet is largely increased,while the contents of Na+?Ca2+?Mg2+ and other non-rare earth impurities decrease significantly—Na+ from 0.31%to 0.1%,and Ca2+ from 1.8%to 0.8%.3.The density of samarium,europium,gadolinium liquid which is produced at the 44th outlet in the mixed carbonate rare earth elements extraction and separation lines of JinXia Chemical Industry of which annual capacity is 5000 tons is usually tested by the national standard volumetric method and gravimetric method.However,when the content of iron is high,testing with volumetric method can cause large error,in excess of the allowable limit.And testing with gravimetric method costs too much time,which will influence efficiency of the whole technological process.To this problem,this paper proposed to add process before determination,which means that increase oxalic acid to separate out Samarium,europium,and gadolinium,then eliminate iron impurity through complete wash,then turn the rare earth precipitation into Samarium,europium,and gadolinium liquid,and then determine its concentration with volumetric method.This analytic method not only decrease the time required for feed analysis,but also increase the accuracy of liquid concentration determination;therefore,the efficiency can be assured.4.Inductance coupling and other ICP-AES methods are used to determine Al3+in the praseodymium-neodymium liquid,carbonate praseodymium-neodymium liquid,and praseodymium-neodymium oxides which are produced in the mixed carbonate rare earth elements extraction and separation lines of JinXia Chemical Industry of which annual capacity is 5000 tons.In order to eliminate the influence from the groundmass to aluminum,praseodymium-neodymium liquid is added as groundmass to calibrate at the peak when preparing the standard liquid.But this approach waste time and a large amount of praseodymium oxide and neodymium oxide as primary reagent as preparing the standard liquid;as a result,an optimized assay method is needed urgently in order to cut the costs.To this problem,the assay method of the content of aluminum is improved by changing the calibration at the peak to off-peak calibration and the operational process is reflected at the preparation of standard liquid which is used to determine the content of aluminum.There from,the way of preparing standard liquid is improved,the process of stoving praseodymium oxide and neodymium oxide is omitted because the back end of the peak can be deducted automatically by the instrument,and the process of evaluating aluminum ion is simplified,which saves costs and time for preparing standard liquid.5.The mixed carbonate rare earth elements extraction and separation lines of JinXia Chemical Industry of which annual capacity is 5000 tons is started from the process of dissolve,and in this process,it is necessary to test the sulfate ion in the mixed rare earth liquid.Usually,spectrophotometric method is applied for testing,and if using this method,stabilizer is needed to stabilize the sedimentary sulfate ions;however,the error is relatively significant,because the variety of stabilizer may result in instability of the results.To address this issue,it is proposed in this paper to determine the sulfate ions in the mixed rare earth liquid with gravimetric method.Modify the liquid into faintly acid,and then add excessive barium chloride liquid to turn the sulfate ions in the mixed rare earth liquid into precipitated barium sulfate.After filtrating,washing,drying,and weighing,calculate the content of sulfate ions,in order to achieve the accurate result.With this method,the accuracy and stability of the result of sulfate ions determination is significantly increased,comparing with using spectrophotometric method. |
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