The rare earth ore is used as raw material, and the process of separation, extraction and ion exchange is used to prepare the rare earth smelter workshop design of various rare earth compounds. There are rare earth minerals bastnasite, monazite, ion adsorption type rare earth ore and xenotime. After the rare earth mineral is decomposed, the mixed compound is extracted from the decomposing liquid, or directly separated into an enrichment and a single rare earth compound.
The products in this workshop are: chlorides, fluorides, nitrates, hydroxides, oxides of various rare earth enriched materials, and oxide-based rare earth compounds with a purity of ≥99-99.99%.
The process of selecting rare earth extraction process adopts general chemical method, the separation process mostly adopts liquid-liquid extraction method, and the production of a small amount of high-purity rare earth is combined by liquid-liquid extraction method and ion exchange method, or extraction color layer method.
Comprehensive process of various concentrates, representative process of rare earth extraction and separation principle is shown in the figure.
When the rare earth extraction and separation is carried out, the rare earth ore is used as the raw material, and the rare earth compound is extracted by the sulfuric acid roasting. The fatty acid is extracted with the fatty acid, and then extracted by HCl solution and concentrated to REO about 200g/L. Then, the P204 or P507 extraction group was separated. This method is more suitable for the separation of light and medium heavy rare earth elements into a single rare earth. It is also possible to use P204 directly from the aqueous extract. The extraction is separated by a group. Although the process is relatively simple, the concentration of rare earth sulfate is low (only 27 to 37 g/L), and the equipment volume is too large and uneconomical.
After the monazite is boiled by caustic soda, RE(OH) 3 is washed with water, completely dissolved with HNO 3 , and then separated by TBP to separate uranium , thorium and rare earth. The rare earth is further extracted and separated, or converted into chloride, and then P204 or P507 was extracted and separated into a single compound.
The ion-adsorbed rare earth concentrate and the xenotime ore are dissolved in HCl (or HNO 3 ), and then subjected to P507 extraction and separation into a single compound.
The main difference and starting point of choosing P204 or P507 is that the extraction separation coefficient of P204 for rare earth elements is slightly lower than that of P507, and the stripping acidity is higher, but the price of P204 is much lower than that of P507. In general, P204 is suitable for light rare earth group separation; P507 is suitable for medium and heavy rare earth separation. In the extraction process design, using the "three-outlet" or "multi-outlet" technology, one or two pure products can be obtained in one extraction system, and one or several enrichments can be obtained at the same time, which can simplify the process and reduce equipment.
Multi isolated using Europium Eu + significantly different chemical properties Eu + 2 and 3, but with the zinc powder is reduced to Eu +2 Eu +3 separation, may be further extracted and purified by P507.
When a small amount of single rare earth is produced from the enrichment material, the P507 chrome resin color layer method can be used to simplify equipment and operation, reduce plant area and reduce product cost.
The main equipment for equipment selection of rare earth extraction and separation workshop is concentrate ore kiln and extraction tank.
The roasting of Baotou rare earth ore and bastnasite is carried out using an internal heat rotary kiln. Capacity can be estimated as follows:
G=GVV, t/d
Where G is the capacity of the internal heat rotary kiln, t/d; V is the total volume of the rotary kiln, m 3 ; GV is the daily capacity per unit volume, t / (m 3 • d), by semi-industrial test or according to similar production Determined based on the statistics of the kiln. The rare earth sulfuric acid roasting kiln with heavy oil as fuel has a GV ≈ 0.45 t / (m 3 • d); the kiln body inclination is 0.02 to 0.025, and the diameter and length ratio are D: L = 1:19.
Decomposition of monazite caustic soda, steel tank with steam jacket heating or electric heating oil bath. The latter has a higher heating temperature, which is conducive to the decomposition of concentrate.
For the grouping and separation of rare earths, a box-type mixing clarification extraction tank is often used. In the fractionation extraction system, the effective volume calculation formula of the mixing chamber of the tank type mixing clarification extraction tank extraction section is:
V=QÏ„,L
Where V is the effective volume of the mixing chamber of the extraction section, L; Q is the flux of the material in a certain production scale, the sum of the flow rate of the extract liquid, the organic phase and the washing liquid, L/min; Ï„ is the water phase measured by the experiment The time required for the organic phase to reach mass transfer equilibrium, min.
The mixing chamber volume of the washing section and the stripping section is smaller than the volume of the extraction section, but when the production scale is not large, in order to facilitate the necessary adjustment of each stage in the processing and production process, the mixing chamber volume is often made and extracted. The same. The volume of the extraction tank clarification chamber is determined by the required clarification time measured by the test. Since the physicochemical properties of rare earth elements are similar to each other, the separation coefficient is small, and the number of extraction stages is large. In order to stabilize and timely reflect the extraction parameters, to stabilize product quality, improve recovery rate and yield, in the large-scale production, set closed-loop feedback Online analytical device. For the production of rare earth products with small batch size and high purity requirements, ion exchange columns can also be used.
The composition of the workshop and the configuration of the rare earth extraction and separation workshop are generally divided into several sections such as concentrate decomposing, rare earth separation, chemical treatment and finished products.
1. Concentrate decomposition section. a workshop using Baotou mixed rare earth ore and bastnasite as raw materials.
Including sulfuric acid roasting, roasting tail gas and water leaching slag treatment section; workshops using monazite as raw materials, including caustic soda digestion, acid dissolution and trisodium phosphate recovery section; workshops using ion-adsorbed rare earth concentrates as raw materials, including acid dissolution And the liquid preparation and adjustment section.
2. Rare earth separation section. It includes extraction liquid, organic phase and various washing liquids, stripping solution, eluent preparation and extraction group separation process.
3. Chemical treatment section. The method comprises the following steps: concentrated crystallization of rare earth chloride or extraction of chlorinated light rare earth solution, concentrated crystallization, hydroxide preparation, extraction and separation of various rare earth chloride (nitrate) solutions for oxalic acid (or ammonium hydrogencarbonate) precipitation and washing And filtration process. Generally, a purification step of a reagent such as hydrochloric acid or oxalic acid is also included.
4. Finished work section. It includes drying, calcining and packaging of rare earth oxalates, carbonates and hydroxides.
The configuration of the rare earth extraction and separation workshop should minimize the pollution surface of a small amount of radioactivity and various harmful gases to ensure the safety and sanitation of personnel; avoid interference with various environmental factors inside and outside the workshop to ensure product purity; and make the numerous pipelines as short as possible And do not cross and so on.
Technical features:
1. There are many trace radioactive elements associated with rare earth concentrates. In the design of extraction and separation workshops, comprehensive prevention and control of radioactivity should be considered; as well as strict anti-corrosion requirements for buildings, equipment and electrical appliances due to the use of strong acid and alkali.
2. There are many varieties and specifications of rare earth products, and the market demand for products often changes. Therefore, in the design, it is necessary to fully consider the flexibility of adjusting the production process.
3. The properties of rare earth elements are very different from each other, the extraction and separation process is lengthy, and the control state of various process parameters must be reflected in many processes to reflect product quality. In order to ensure product quality stability and improve product recovery rate, special attention should be paid in the design to stabilize the process parameters of each process, strengthen the central control analysis, and set up an online analysis device with feedback control in key parts.
The main technical and economic indicators are different due to the different rare earth concentrates used, the varieties and specifications of the products are different, the process flow is quite different, and the management level factors, the technical and economic indicators of each factory are also different.
1. The unit consumption of rare earth products in some factories is shown in Table 1.
2. The total recovery rate of rare earth products in some factories is shown in Table 2.
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