TECHNOLOGY
Extractive separation of REE concentrates in cascades of centrifugal extractors, model EC-1000PB
Historically, the first industrial technology of separation of REEs included extraction with 100% TBP from nitrate solutions with a salting agent and was implemented in cascades of box-type mixing-settling extractors. For extractive separation of REE carried out from concentrated aqueous solutions with a density of the aqueous phase ≥1.5 g / dm3, accompanied by the formation of a saturated viscous organic phase, the phase separation rate is the limiting stage, therefore this equipment has a low productivity and low efficiency of the stage. The composition of REE concentrates contains from 15 to 17 individual elements that are similar in chemical properties, therefore, for their separation, a large number of extraction cascades with a large number of stages are required. Production of rare-earth concentrate (REC) separation of the leading world powers (USA, USSR, Canada, China), built in the 80-90s, when their consumption was intensively developed in the world, is characterized by high material and energy intensity, occupy large areas. As a result, such production requires large-scale technical support, enormous capital investments and working capital, in addition, they are characterized by a large volume unfinished production.
It should be noted that in Russia at present there are no industrial capacities for the separation of rare-earth metals, which is the main inhibiting factor in the matter of restoring the rare-earth industry in the Russian Federation. At the same time, it is obvious that in the existing economic situation it is in principle unrealistic to provide financing for such large-scale costs for the creation of industrial production for the separation of REC with obtaining individual REE, based on the outdated technological approach.
The Laboratory of Innovation Technologies of the Group of Companies «Skygrad» has developed a unique technology for separating various types of REC with obtaining concentrates of the moderate- heavy REE group and high-purity compounds of cerium, lanthanum, neodymium, praseodymium, including the processes of electrochemical oxidation of cerium in electrolyzers with a ceramic corundum diaphragm and extraction in automated cascades of own design and manufacture. The technology of separation and design of innovative equipment, ensuring the effective implementation of the technology, are protected by patents of the Russian Federation (No. 2605751, 2623542, 2566137, 150234, application for obtaining patent No. 2018146343 dated December 25, 2018).
The main advantages of the developed technology:
The raw material used for separation at this stage is a REC produced by JSC «Solikamsk Magnesium Plant». The processing volume is up to 140t ∑REO per year.
PROCESS DESCRIPTION
Historically, the first industrial technology of separation of REEs included extraction with 100% TBP from nitrate solutions with a salting agent and was implemented in cascades of box-type mixing-settling extractors. For extractive separation of REE carried out from concentrated aqueous solutions with a density of the aqueous phase ≥1.5 g / dm3, accompanied by the formation of a saturated viscous organic phase, the phase separation rate is the limiting stage, therefore this equipment has a low productivity and low efficiency of the stage. The composition of REE concentrates contains from 15 to 17 individual elements that are similar in chemical properties, therefore, for their separation, a large number of extraction cascades with a large number of stages are required. Production of rare-earth concentrate (REC) separation of the leading world powers (USA, USSR, Canada, China), built in the 80-90s, when their consumption was intensively developed in the world, is characterized by high material and energy intensity, occupy large areas. As a result, such production requires large-scale technical support, enormous capital investments and working capital, in addition, they are characterized by a large volume unfinished production.
It should be noted that in Russia at present there are no industrial capacities for the separation of rare-earth metals, which is the main inhibiting factor in the matter of restoring the rare-earth industry in the Russian Federation. At the same time, it is obvious that in the existing economic situation it is in principle unrealistic to provide financing for such large-scale costs for the creation of industrial production for the separation of REC with obtaining individual REE, based on the outdated technological approach.
The Laboratory of Innovation Technologies of the Group of Companies «Skygrad» has developed a unique technology for separating various types of REC with obtaining concentrates of the moderate- heavy REE group and high-purity compounds of cerium, lanthanum, neodymium, praseodymium, including the processes of electrochemical oxidation of cerium in electrolyzers with a ceramic corundum diaphragm and extraction in automated cascades of own design and manufacture. The technology of separation and design of innovative equipment, ensuring the effective implementation of the technology, are protected by patents of the Russian Federation (No. 2605751, 2623542, 2566137, 150234, application for obtaining patent No. 2018146343 dated December 25, 2018).
The main advantages of the developed technology:
- The oxidation of cerium is carried out in a two-chamber electrolyzer, in which the cathode chamber is separated from the anodic by porous ceramic diaphragm made by the plasma-chemical method. Instead of the platinum mesh used previously, as the anode is used titanium plate with an activating iridium dioxide coating. The use of this technological approach allows to increase the economic efficiency by ~ 1.5 times;
- Separation of REEs is carried out in cascades of centrifugal extractors of own design and manufacture, which, with relatively equal overall dimensions than in the previously known apparatus have 25-30 times less extractant loading volume, and at the same time 30 times more performance. The loading of working solutions and extractant into a cascade of centrifugal extractors of 65 stages is 200 times less than in a cascade of box-type extractors of a similar productivity. The use of a new method of REC separation allows to increase the economic efficiency of production by 25-30 times.
- In the technology, an optimally diluted extractant (75-80% TBP in RED-3M) is used as an extractant, which, with high saturation of REE, quickly exfoliates in an emulsion with concentrated solutions of REE. This reduces the direct loss of the extractant while maintaining the high performance of the separation process;
- The binding of extractors (steps) for input and output of the extractant, working solutions and finished products is carried out in such a way that the aqueous solutions which is removed from the cascade are washed from the emulsified extractant in the additional step (extractor) of the cascade, which reduces the extractant losses and equipment costs and increases purity of the products;
- Separation cascades of centrifugal extractors have low inertia, which allows you to quickly change the cascade's operating mode, overload the cascades without loss of production, which is especially important when switching to another concentrate composition - the unfinished production will be 25-30 times smaller (by volume), while re-tuning cascades takes less than one work shift. In fact, the cascade of REC separation , working on the new technology, are universal;
- The new version of separation technology is easy to automate, which reduces the risk of the "human factor" influence on production management, significantly increases production safety and process productivity.
The raw material used for separation at this stage is a REC produced by JSC «Solikamsk Magnesium Plant». The processing volume is up to 140t ∑REO per year.
PROCESS DESCRIPTION
Dissolving REC
A rare-earth concentrate produced by JSC «SMP» is supplied for dissolution. The output product is a nitrate solution containing 350-370 g/l of oxides of rare-earth metals.
A rare-earth concentrate produced by JSC «SMP» is supplied for dissolution. The output product is a nitrate solution containing 350-370 g/l of oxides of rare-earth metals.
Electro-oxidation Ce
The nitrate solution of rare earth elements obtained after dissolution is sent to the stage of electrochemical oxidation of cerium. The process of cerium oxidation is carried out in electrolyzers SKYCEL-500 (own design, protected by patent No. 2605751), where cerium (+3) is oxidized to cerium (+4). Figure 3-4 shows fragments of the stage of electro-oxidation of cerium and the design of the electrolyzer
The nitrate solution of rare earth elements obtained after dissolution is sent to the stage of electrochemical oxidation of cerium. The process of cerium oxidation is carried out in electrolyzers SKYCEL-500 (own design, protected by patent No. 2605751), where cerium (+3) is oxidized to cerium (+4). Figure 3-4 shows fragments of the stage of electro-oxidation of cerium and the design of the electrolyzer
Extractive separation of cerium (+4)
The extractive separation of oxidized cerium takes place in a cascade of centrifugal extractors, which includes the stages of extraction, washing, reduction of cerium to Ce (+3) and re-extraction. The initial solution in the separation process forms two products: raffinate and re-extract. The re-extract containing 99.99% or more of cerium is going for further processing to produce cerium carbonate and, if necessary, cerium oxide. The raffinate containing the remaining REE is sent to the extractive separation by the Pr / Ce line to separate lanthanum.
The extractive separation of oxidized cerium takes place in a cascade of centrifugal extractors, which includes the stages of extraction, washing, reduction of cerium to Ce (+3) and re-extraction. The initial solution in the separation process forms two products: raffinate and re-extract. The re-extract containing 99.99% or more of cerium is going for further processing to produce cerium carbonate and, if necessary, cerium oxide. The raffinate containing the remaining REE is sent to the extractive separation by the Pr / Ce line to separate lanthanum.
Cerium Carbonate Production
The cerium re-extract fed into precipitation reactor, where cerium carbonate is precipitated with a solution of ammonium carbonate. The method of precipitation of carbonates is protected by the application for the invention, the registry № 2018147104, 12.28.2018). Cerium carbonate pulp is filtered on a drum vacuum filter. Moisture content of the obtained cerium carbonate is 38-45% and corresponds to TU 20.13.65-002-92697718-2018.
The cerium re-extract fed into precipitation reactor, where cerium carbonate is precipitated with a solution of ammonium carbonate. The method of precipitation of carbonates is protected by the application for the invention, the registry № 2018147104, 12.28.2018). Cerium carbonate pulp is filtered on a drum vacuum filter. Moisture content of the obtained cerium carbonate is 38-45% and corresponds to TU 20.13.65-002-92697718-2018.
Pr/Ce extractive separation
The raffinate obtained during the extractive separation of cerium (+4) is evaporated until the content of the REO is ~ 350 g/l and used as an initial solution for the extractive separation by the Pr/Ce line. The separation process takes place in a cascade of centrifugal extractors and includes the stage of extraction, washing and re-extraction. The resulting raffinate, containing 90-95% lanthanum, goes to further obtaining of the individual lanthanum compounds — a nitrate solution, carbonate or oxide. The re-extract containing the remaining REE is directed to the extractive separation by the Sm/Nd line.
The raffinate obtained during the extractive separation of cerium (+4) is evaporated until the content of the REO is ~ 350 g/l and used as an initial solution for the extractive separation by the Pr/Ce line. The separation process takes place in a cascade of centrifugal extractors and includes the stage of extraction, washing and re-extraction. The resulting raffinate, containing 90-95% lanthanum, goes to further obtaining of the individual lanthanum compounds — a nitrate solution, carbonate or oxide. The re-extract containing the remaining REE is directed to the extractive separation by the Sm/Nd line.
Obtaining individual La compounds
The raffinate obtained from the Pr/Ce separation line fed into precipitation reactor with ammonium carbonate obtaining lanthanum carbonate, which is filtered on a drum vacuum filter. The obtained lanthanum carbonate has a moisture content of 40-45% and contains 90-95% lanthanum. In the future, if necessary, lanthanum carbonate is dissolved in nitric acid to obtain a solution of lanthanum nitrate according to the Specifications of the Russian Federation 243000-01-92697718 - 2018 grades A, B and B (180 g/l according to ΣREO, 90%, 70% and 65% lanthanum oxide from REO amounts, respectively).
The raffinate obtained from the Pr/Ce separation line fed into precipitation reactor with ammonium carbonate obtaining lanthanum carbonate, which is filtered on a drum vacuum filter. The obtained lanthanum carbonate has a moisture content of 40-45% and contains 90-95% lanthanum. In the future, if necessary, lanthanum carbonate is dissolved in nitric acid to obtain a solution of lanthanum nitrate according to the Specifications of the Russian Federation 243000-01-92697718 - 2018 grades A, B and B (180 g/l according to ΣREO, 90%, 70% and 65% lanthanum oxide from REO amounts, respectively).
Sm/Nd extractive separation
The re-extract obtained from the Pr/Ce separation cascade is evaporated to a REO content of ~ 350 g/l and used as an initial solution for the extractive separation by the Sm / Nd line. The separation process takes place in a cascade of centrifugal extractors, including the stage of extraction, washing and re-extraction. The resulting raffinate containing praseodymium and neodymium, goes to the extractive separation by the line Nd/Pr. The re-extract containing moderate-heavy REE goes to the precipitation with ammonium carbonate and filtration to obtain carbonates of moderate-heavy REE.
The re-extract obtained from the Pr/Ce separation cascade is evaporated to a REO content of ~ 350 g/l and used as an initial solution for the extractive separation by the Sm / Nd line. The separation process takes place in a cascade of centrifugal extractors, including the stage of extraction, washing and re-extraction. The resulting raffinate containing praseodymium and neodymium, goes to the extractive separation by the line Nd/Pr. The re-extract containing moderate-heavy REE goes to the precipitation with ammonium carbonate and filtration to obtain carbonates of moderate-heavy REE.
Nd/Pr extractive separation
The raffinate obtained from the Sm/Nd separation line is evaporated to a REO content of ~ 350 g/l and used as an initial solution for the extractive separation by the Nd/Pr line. The separation process takes place in a cascade of centrifugal extractors, including the stage of extraction, washing and re-extraction. The resulting raffinate, containing ~ 60-70% praseodymium goes to the purification with the further production of individual praseodymium compounds - a nitrate solution, carbonate or oxide with a praseodymium content of up to 99.99% or more. The re-extract containing not less than 99.9% of neodymium, goes to the further production of individual compounds – nitrate solution, carbonate or neodymium oxide.
The raffinate obtained from the Sm/Nd separation line is evaporated to a REO content of ~ 350 g/l and used as an initial solution for the extractive separation by the Nd/Pr line. The separation process takes place in a cascade of centrifugal extractors, including the stage of extraction, washing and re-extraction. The resulting raffinate, containing ~ 60-70% praseodymium goes to the purification with the further production of individual praseodymium compounds - a nitrate solution, carbonate or oxide with a praseodymium content of up to 99.99% or more. The re-extract containing not less than 99.9% of neodymium, goes to the further production of individual compounds – nitrate solution, carbonate or neodymium oxide.
Obtaining individual compounds Nd and Pr
Purified raffinate obtained from the Nd/Pr separation cascade fed into a precipitation reactor, with ammonium carbonate obtaining praseodymium carbonate, which is filtered on a drum vacuum filter. The resulting praseodymium carbonate has a moisture content of 40-45% and contains up to 99.9% of praseodymium.
Purified raffinate obtained from the Nd/Pr separation cascade fed into a precipitation reactor, with ammonium carbonate obtaining praseodymium carbonate, which is filtered on a drum vacuum filter. The resulting praseodymium carbonate has a moisture content of 40-45% and contains up to 99.9% of praseodymium.
The re-extract obtained from the Nd/Pr separation cascade containing ≥99.9% neodymium is also fed into the precipitation reactor, to obtain neodymium carbonate, which is filtered on a drum filter. The resulting neodymium carbonate has a moisture content of 40-45%. Neodymium carbonate is calcined in a hearth furnace to produce neodymium oxide according to TU 20.13.65-004-92697718-2018 of grades B - the content of neodymium oxide is at least 99.995% and C is the content of neodymium oxide at least 99.9%.
The following patents have been obtained for the technology of obtaining individual REE compounds and equipment:
1) Patent for invention (RU) No. 2566137 "Centrifugal extractor", priority of the invention dated 10.22.2013, the authors, A. M. Abramov et al.
2) Patent for utility model (RU) No. 150234 "Centrifugal extractor", priority of the invention from September 15, 2014, by the authors A. Abramov et al.
3) Patent for the invention (RU) No. 2605751 of 12/30/2015 "Electrolyzer", authors Abramov AM and others.
4) Patent for invention (RU) No. 2623542: dated 08/10/2016 "The method of electrochemical oxidation of cerium", the authors Abramov AM et al.
5) Patent for invention (RU) No. 2645136 "Hydropneumatic device", priority of the invention dated May 30, 2017, authors Galieva Zh.N. et al.
6) Application for invention (RU) "Method of extractive separation of rare-earth elements", reg. No. 2018146343 from 12/25/2018, authors Galieva Zh.N. et al.
7) Application for invention (RU) "Method for producing carbonates of rare-earth elements", registration. No. 2018147104 dated 12.28.2018, authors Gerya V.O. et al.
The following patents have been obtained for the technology of obtaining individual REE compounds and equipment:
1) Patent for invention (RU) No. 2566137 "Centrifugal extractor", priority of the invention dated 10.22.2013, the authors, A. M. Abramov et al.
2) Patent for utility model (RU) No. 150234 "Centrifugal extractor", priority of the invention from September 15, 2014, by the authors A. Abramov et al.
3) Patent for the invention (RU) No. 2605751 of 12/30/2015 "Electrolyzer", authors Abramov AM and others.
4) Patent for invention (RU) No. 2623542: dated 08/10/2016 "The method of electrochemical oxidation of cerium", the authors Abramov AM et al.
5) Patent for invention (RU) No. 2645136 "Hydropneumatic device", priority of the invention dated May 30, 2017, authors Galieva Zh.N. et al.
6) Application for invention (RU) "Method of extractive separation of rare-earth elements", reg. No. 2018146343 from 12/25/2018, authors Galieva Zh.N. et al.
7) Application for invention (RU) "Method for producing carbonates of rare-earth elements", registration. No. 2018147104 dated 12.28.2018, authors Gerya V.O. et al.
