1. Rare earth beneficiation
Mineral processing is the use of different mineralization methods between the various minerals that make up the ore. Different mineral processing methods, different mineral processing techniques, different mineral processing equipment, the useful minerals in the ore are enriched to remove harmful impurities. A mechanical process that separates it from gangue minerals.
At present, rare earth ore mined in China and other countries in the world, the content of rare earth oxides is only a few percent, or even lower. In order to meet the production requirements of smelting, the ore minerals and gangue minerals will be processed before smelting. and other useful minerals apart to increase the content of rare earth oxide, a rare earth to meet the obtained rare earth ore metallurgical requirements. The beneficiation of rare earth ore is generally carried out by flotation, and is often supplemented by re-election and magnetic separation to form a variety of combinations of beneficiation processes. The rare earth deposit of the Baiyun Obo mine in Inner Mongolia is a carbonate rock deposit of iron dolomite. It is associated with rare earth minerals in the main component iron ore (in addition to fluorocarbon antimony ore, monazite, there are also several kinds of antimony and rare earth minerals). The produced ore contains about 30% iron and about 5% rare earth oxide. First in the mine
After the large ore is broken, it is transported by train to the concentrating plant of Baotou Iron and Steel Group Co., Ltd. The task of the concentrator is to increase the Fe2O3 from 33% to more than 55%. First, grind and classify on a conical ball mill, and then use a cylindrical magnetic separator to select a primary iron concentrate of 62 to 65% Fe2O3. The tailings continue to undergo flotation and magnetic separation to obtain a secondary iron concentrate containing 45% Fe2O3 or more. The rare earth is enriched in the flotation foam and the grade is 10-15%. The enrichment can be selected from a coarse concentrate having a REO content of 30% by a shaker, and after reprocessing by the ore dressing equipment, a rare earth concentrate having a REO of more than 60% can be obtained.
Second, rare earth smelting methods
There are two kinds of rare earth smelting methods, namely hydrometallurgy and pyrometallurgy.
Wet metallurgy metallurgy metallurgy, the whole process is mostly in solution, solvent, such as the decomposition of rare earth concentrate, rare earth oxides, rare earth compounds, single rare earth metal separation and extraction process is the use of precipitation, crystallization, redox, solvent Chemical separation process such as extraction and ion exchange. The most common application is the organic solvent extraction method, which is a general process for industrial separation of high purity single rare earth elements. The hydrometallurgical process is complex and the product purity is high.
The pyrometallurgical process is simple and has high productivity. Rare earth pyrometallurgical smelting mainly includes the preparation of rare earth alloy by silicon thermal reduction method, rare earth metal or alloy by molten salt electrolysis method, and rare earth alloy by metal thermal reduction method. The common feature of pyrometallurgy is that it is produced under high temperature conditions.
1. Decomposition of rare earth concentrate
Rare earth rare earth concentrate, generally in the form of a water-insoluble carbonates, fluorides, phosphates, oxides, silicates, or the like. The rare earth must be converted into a compound dissolved in water or inorganic acid by various chemical changes, and dissolved, separated, purified, concentrated or calcined to form various mixed rare earth compounds such as mixed rare earth chlorides as products or separations. A single rare earth raw material, such a process is called rare earth concentrate decomposition, also known as pretreatment. There are many ways to decompose rare earth concentrates. In general, they can be divided into three categories, namely, acid method, alkali method and chlorination. The acid decomposition is further divided into hydrochloric acid decomposition, sulfuric acid decomposition, and hydrofluoric acid decomposition. Alkali decomposition is further divided into sodium hydroxide decomposition or sodium hydroxide melting or soda roasting. Generally, according to the type of concentrate, grade characteristics, product plan, easy to recycle and comprehensive utilization of non-rare earth elements, conducive to labor hygiene and environmental protection, economic and reasonable principles, select the appropriate process.
Production of rare earth carbonates and rare earth chlorides:
This is the two most important primary products in the rare earth industry. Generally speaking, there are currently two main processes for producing these two products.
One process is a concentrated sulfuric acid roasting process in which a rare earth concentrate is mixed with sulfuric acid and calcined in a rotary kiln. When the calcined ore is leached with water, the soluble rare earth sulfate enters the aqueous solution, which is called a leachate. Then, ammonium hydrogencarbonate is added to the leachate, and the rare earth is precipitated as a carbonate, and after filtration, a rare earth carbonate is obtained.
Another process is called the caustic soda process, referred to as the alkali process. Generally, 60% of the rare earth concentrate is mixed with the concentrated alkali solution, and the reaction is melted at a high temperature. The rare earth concentrate is decomposed, the rare earth is changed into rare earth hydroxide, and the alkali cake is washed with water to remove the sodium salt and the excess alkali, and then The washed rare earth hydroxide is dissolved in hydrochloric acid, the rare earth is dissolved into a rare earth chloride solution, the acidity is removed to remove impurities, and the filtered rare earth chloride solution is concentrated and crystallized to obtain a solid rare earth chloride.
2. Separation of rare earth elements
At present, 16 rare earth elements other than Pm can be purified to a purity of 6N (99.9999%). Separating and extracting a single pure rare earth element from the mixed rare earth compound obtained by decomposing the rare earth concentrate is complicated and difficult in chemical process. There are two main reasons. First, the physical properties and chemical properties between the lanthanides are very similar. Most of the rare earth ions have a radius between adjacent two elements, which are very similar, and are stable in the aqueous solution. Rare earth ions have a large affinity with water. Due to the protection of hydrates, their chemical properties are very similar, and separation and purification are extremely difficult. Second, the mixed rare earth compounds obtained after decomposition of the rare earth concentrate have more impurity elements (such as uranium , thorium , krypton, neodymium, titanium , zirconium , iron, calcium, silicon, fluorine, phosphorus, etc.). Therefore, in the process of separating rare earth elements, not only the separation of these dozens of rare earth elements with extremely similar chemical properties but also the separation between the rare earth elements associated with the rare earth elements must be considered. The separation method (wet production process) used in the production of rare earths now has: (1) a stepwise method (grading crystallization method, a fractional precipitation method, and a redox method); (2) an ion exchange method; and (3) a solvent extraction method.
(1) Step by step method
From the yttrium (Y) discovered in 1794 to the ruthenium (Lu) discovered in 1905, the single separation between all naturally occurring rare earth elements, as well as the radium discovered by the Curie couple, was isolated by this method. Step-by-step method is to use compounds in solution
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