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costs for the creation of industrial production for the separation of REC with obtaining individual REE, based on the outdated technological approach.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 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 technology is implemented on the experimental production of LLC «LIT» for the separation of rare-earth concentrates with obtaining a concentrate of the moderate-heavy REE group and oxides of cerium, lanthanum, neodymium, praseodymium, with the assistance of the Ministry of Industry and financial support of the Industry Development Fund (IDF) - at the end of 2016 the project received a preferential loan under the flagship program "Development Projects". Production of LLC «LIT» is fully automated.
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