[SMM Science Popularization] to understand the types, mineral processing, decomposition, smelting and distribution of rare earth ores

Brief introduction of rare Earth products

Rare earth is the general name of 17 chemical elements, known as "vitamins of modern industry". In the periodic table of chemical elements, lanthanide, scandium and yttrium, which are closely related to lanthanide, are called rare earth elements.

According to the atomic electron layer structure and physical and chemical properties of rare earth elements, as well as their symbiosis in minerals and the characteristics that different ion radii can produce different properties, seventeen rare earth elements are usually divided into two groups:

Light rare earths include lanthanum, cerium, praseodymium, neodymium, zinc, samarium and europium.

Heavy rare earths include gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium and yttrium.

The rare earth industry chain is mainly composed of the exploitation of rare earth resources in the upstream, the preparation of rare earth materials in the middle reaches, and the application fields downstream. In the upstream, rare earth elements are generally extracted from minerals such as monazite, yttrium phosphate, fluorocarbon cerite and ion adsorption rare earth ores to form rare earth oxides, rare earth metals and so on.

In the middle reaches, rare earth materials are prepared, and the ores mined in the upper reaches are smelted and purified into all kinds of rare earth materials, such as rare earth catalytic materials, rare earth permanent magnet materials, rare earth hydrogen storage materials, rare earth luminescent materials and so on.

Downstream is mainly used in the military, petrochemical, glass ceramics, new materials, precision electronic components and other industries. Rare earth permanent magnet materials account for nearly 50% of China's rare earth consumption, and it is the most important track in the lower reaches of the rare earth industry chain.

Rare earth mineral types

Rare earth ores are mainly divided into monazite, fluorocarbon cerite, yttrium phosphate, weathering crust leaching type rare earth ores.

Monazite: monazite, also known as phosphocerium lanthanite, the content of rare earth oxides in mineral composition can reach 500.68%. The appearance is yellowish brown, brown, red, occasionally green, translucent to transparent, streaks white or light reddish yellow. With strong glass luster, hardness 5.0-5.5, brittle, specific gravity 4.9-5.5. The electromagnetism is weak, it emits green light under X-ray and does not emit light under cathode ray. The main resources of monazite with economic mining value are alluvial or seashore placer deposits. The most important seashore placers are along the coasts of Australia, Brazil and India. In addition, Sri Lanka, Madagascar, South Africa, Malaysia, China, Thailand, South Korea, North Korea and other places all contain monazite heavy sand deposits. The production of monazite shows a downward trend in recent years, mainly due to the radioactivity of thorium in the ore, which is harmful to the environment.

Fluorocarbon cerite: occurs in rare metal carbonate rocks, granite and granitic pegmatites, quartz veins related to granite syenite, quartz ferromanganese carbonate dikes, placers. It is an important mineral raw material for the extraction of cerium group rare earth elements. Cerium family elements can be used to make alloys to improve the elasticity, toughness and strength of metals. they are important parts for making jet aircraft, missiles, engines and heat-resistant machinery. It can also be used as a protective shell against radiation, etc. In addition, cerium family elements are also used to make all kinds of colored glass. As a by-product of iron ore mining, it is mined together with monazite, with an average rare earth oxide content of 50.6%. The highest-grade industrial fluorocarbon-cerite deposit is the Mount pass Mine in California, USA, which is the only fluorocarbon-cerite in the world that mainly mines rare earths.

Yttrium phosphate rock: Y2O361.4% of the ingredient Y2O361.4% of the composition P2O538.6%. Yttrium group rare earth elements are mixed, mainly ytterbium, erbium, dysprosium and gadolinium. There are zirconium, uranium, thorium and other elements instead of yttrium, accompanied by silicon instead of phosphorus. Generally speaking, the content of uranium in yttrium phosphate is greater than that of thorium. The chemical property of yttrium phosphate ore is stable. It occurs mainly in granite, granite pegmatite, alkaline granite and related ore deposits, and also in placer. When enriched in large amounts, it is used as a mineral raw material for the extraction of rare earth elements.

Weathering crust leaching type rare earth ore: weathering crust leaching type rare earth ore (Ion absorpt deposit), that is, ion adsorption rare earth ore, is a new type of rare earth mineral unique to China. The so-called "ion adsorption" is that rare earth elements do not exist in the form of compounds, but adsorb in clay minerals in the form of ions. These rare earths are easy to be transferred into solution for strong electrolyte exchange, and mixed rare earth oxides can be obtained by direct leaching without crushing and mineral processing. Therefore, this kind of ore is characterized by high content of heavy rare earth elements, high economic content, low grade, large coverage, mostly in hilly areas, suitable for manual and semi-mechanized mining, and simple mining and leaching process. Weathering crust leaching type rare earth deposits are mainly distributed in Jiangxi, Guangdong, Hunan, Guangxi, Fujian and other places in China.

Preparation method of rare earth

Mineral processing of rare earths

Mineral processing is a mechanical process in which the useful minerals in the ore are enriched and harmful impurities are removed by using different mineral processing methods, different mineral processing processes and different mineral processing equipment, making use of the differences in the physical and chemical properties of the various minerals that make up the ore.

At present, the content of rare earth oxides in rare earth ores mined in China and other countries in the world is only a few percent, or even lower. In order to meet the production requirements of smelting, rare earth minerals are separated from gangue minerals and other useful minerals before smelting, so as to increase the content of rare earth oxides and obtain rare earth concentrates that can meet the requirements of rare earth metallurgy. Flotation is generally used in the mineral processing of rare earth ores, which is often supplemented by gravity separation and magnetic separation to form a variety of mineral processing processes.

The rare earth deposit of Bayan Obo Mine in Inner Mongolia is a carbonatite deposit of iron dolomite, which is associated with rare earth minerals (besides fluorocarbon cerite and monazite, there are several kinds of niobium and rare earth minerals) in the main composition iron ore. The mined ore contains about 30% iron and about 5% rare earth oxides. After the large ore is crushed in the mine, it is transported by train to the concentrator of Baotou Iron and Steel Group. The task of the concentrator is to increase the Fe2O3 from 33% to more than 55%, first grinding and grading on a conical ball mill, and then using a cylindrical magnetic separator to separate the primary iron concentrate of 62~65%Fe2O3 (iron oxide). The tailings continue flotation and magnetic separation to obtain secondary iron concentrates containing more than 45% Fe2O3 (iron oxide). Rare earths are enriched in flotation foam with a grade of 1015%. The concentrate can be used to select the crude concentrate with 30% ReO content, and the rare earth concentrate with more than 60% ReO can be obtained after re-treatment by mineral processing equipment.

Decomposition of rare earth concentrate

Rare earths in rare earth concentrates are generally in the form of insoluble carbonates, fluoride, phosphates, oxides or silicates. Rare earths must be converted into compounds soluble in water or inorganic acids through various chemical changes, and various mixed rare earth compounds such as mixed rare earth chlorides must be made by dissolution, separation, purification, concentration or burning, etc. as raw materials for products or separation of single rare earths, this process is called rare earth concentrate decomposition, also known as pretreatment.

There are many methods to decompose rare earth concentrate, which can be divided into three categories, namely, acid method, alkali method and chlorination decomposition. Acid decomposition can be divided into hydrochloric acid decomposition, sulfuric acid decomposition and hydrofluoric acid decomposition. Alkaline decomposition is divided into sodium hydroxide decomposition or sodium hydroxide melting or soda roasting and so on. Generally, the appropriate technological process is selected according to the type of concentrate, grade characteristics, product scheme, convenient recovery and comprehensive utilization of non-rare earth elements, labor hygiene and environmental protection, economic and reasonable and so on.

At present, although nearly 200 kinds of scattered element minerals have been found, they are not rich in independent deposits with industrial mining because they are rare. so far, only rare independent germanite, selenite and tellurite have been found, but the scale of the deposits is not large.

Smelting of rare earths

There are two kinds of rare earth smelting methods, namely hydrometallurgy and pyrometallurgy.

In the way of metal chemical metallurgy in hydrometallurgy, the whole process is mostly in solution and solvent. for example, the separation and extraction process of rare earth concentrate, rare earth oxide, rare earth compound and single rare earth metal is the chemical separation process such as precipitation, crystallization, redox, solvent extraction, ion exchange and so on. At present, organic solvent extraction is widely used, which is a general process for industrial separation of high purity single rare earth elements. The hydrometallurgical process is complex and the purity of the product is high. The application of this method to the production of finished products is wide.

The pyrometallurgical process is simple and the productivity is high. Rare earth pyrometallurgy mainly includes the preparation of rare earth alloys by silicothermic reduction, rare earth metals or alloys by molten salt electrolysis, rare earth alloys by metal thermal reduction and so on. The common feature of pyrometallurgy is that it is produced at high temperature.

Global distribution of rare earths

According to the USGS survey data of the US Geological Survey, the world's rare earth reserves were 120 million tons of rare earth oxides (REO) in 2021. China has the largest rare earth reserves in the world, at 44 million tons (REO), accounting for 37 percent of the world's total. Brazil, Vietnam and Russia are second only to China in rare earth resources, with rare earth reserves of 22 million tons, 21 million tons and 21 million tons, respectively. Global mine production in 2021 is 280000 tons (REO). According to China's Ministry of Industry and Information Technology, the mine production quota for 2021 is 168000 tons, accounting for 60% of the world's total, including 148850 tons of light rare earths and 19150 tons of ion-adsorbed clay.

Distribution of rare earths overseas

Australia, Greenland, the United States and other areas are more concentrated, and most of them are light rare earth ores, while medium and heavy rare earth ores are mainly distributed in Myanmar. At present, Mount Weld and Mountain Pass are the two major overseas light rare earth mines.

Australian Mount Weld is a high-grade rare earth ore dominated by fluorocarbon cerium lanthanum ore, which is currently composed of two core mining areas. The mine was put into production in 2013 with an initial production capacity of 11000 tons (REO) / year, and then increased to 25000 tons (REO) / year. The current capacity utilization is about 75%. There are no plans to continue to expand production in the short term, and the capacity increment is relatively limited. The mine is owned by Lynas, a mining company engaged in integrated rare earth mineral mining and processing mainly in Australia and Malaysia.

The Mountain Pass Mine in California, which is owned by MP Materials, is the largest rare earth mine outside China. The total ore volume is about 21.1 million tons, the reserves is 1.5 million tons REO, and the average grade is 7.06%. It began to resume production in January 2018, and the designed annual production capacity is 40,000 tons REO, which is mainly sold to China through Shenghe resources. at present, the production capacity has climbed to the full production stage, and there is no short-term mine expansion plan.

Distribution of rare earths in China

China is rich in rare earth resources, with obvious distribution characteristics of "heavy in the south and light in the north". The reserves and resource types of light rare earths and heavy rare earths have significant advantages in the world.

China's rare earth minerals are distributed in North, Northeast, East China, South Central, Southwest and Northwest, but the reserves are highly concentrated, mainly in Bayan Obo in Baotou, Inner Mongolia, Gannan in Jiangxi, northern Guangdong in Guangdong and Liangshan in Sichuan. A few are distributed in Shandong, Hunan, Shanxi, Liaoning, Shaanxi, Xinjiang and other provinces. 98% of the country's total rare earth resources are distributed in Inner Mongolia, Jiangxi, Guangdong, Sichuan, Shandong and other regions.

Bayan Obo Mine in Inner Mongolia is the largest rare earth deposit in the world. it is a large symbiotic deposit of iron, rare earth, niobium and other metals. It contains more than 41% of the world's total proven reserves of rare earth minerals and 71 kinds of elements, such as iron, niobium, manganese, phosphorus, fluorite and 175 kinds of minerals. Among them, iron ore reserves are 1.4 billion tons, with an average grade of 34%; rare earth reserves are 100 million tons, accounting for 38% of the world's total proven reserves, ranking first in the world, and officially put into production in 1957.

According to Yang Zhanfeng, vice president of the China Society of rare Earths and director of the State key Laboratory for Research and Comprehensive Utilization of Bayan Obo rare Earth Resources, the rare earth reserves data adopted by the industry are still the results of evaluation in the 1950s. Due to the limited demand and exploration means of iron ore at that time, the whole deposit was not completely explored, and the periphery of the iron orebody and 500 meters below the surface were not explored in detail.

The first mining index of rare earth mines in China in 2022

On January 28, the Ministry of Industry and Information Technology and the Ministry of Natural Resources issued the notice on the total amount control index of the first batch of rare earth mining and smelting separation in 2022. This year, the total amount control targets of rare earth mining and smelting separation are 100800 tons and 97200 tons respectively, up 20% from the first batch of 84000 tons of mining and 81000 tons of smelting separation last year.

The bidders are China rare Earth Group, Northern rare Earth, Xiamen Tungsten Industry and Guangdong rare Earth Group. Among them, the north has the largest amount of rare earth mining, with 60200 tons, followed by China rare Earth Group, with 36900 tons. The third and fourth places are Xiamen Tungsten Industry and Guangdong rare Earth Group, with production volume of 2064 tons and 1620 tons respectively. The separation and smelting index increased by 20% over the same period last year, of which the rare earth separation and smelting index in the north was 53800 tons, an increase of 40.4% over the same period last year, with quotas accounting for 55.4%; and the separation and smelting index of China rare Earth Group was 34700 tons, an increase of 2% over the same period last year, with quotas accounting for 35.7%.

China's four major rare earth groups

Northern rare earths (600111): as the world's largest producer of rare earth minerals, China has the "Bayan Obo rare earth mine" with absolute cost advantage, which plays a leading role in the supply of rare earth industry. Bayan Obo rare earth mine is the largest rare earth mine in the world, while Baotou Steel Group, the controlling shareholder of northern rare earths, has the exclusive mining rights of Bayan Obo Mine, and the northern rare earths are mainly engaged in rare earth smelting and processing business. Northern rare earths are only responsible for mining light rare earths, while medium and heavy rare earths are distributed in the south and are subcontracted by three other groups.

China rare Earth Group (00769): China rare Earth Group Co., Ltd. was officially established on December 23. China rare Earth Group is a large rare earth enterprise group established by China Aluminum Group Co., Ltd., China Minmetals Group Co., Ltd., and Ganzhou rare Earth Group Co., Ltd., in order to realize the complementary advantages of rare earth resources and the coordination of rare earth industry development, China Steel Research Technology Group Co., Ltd., Youyan Science and Technology Group Co., Ltd. and other two rare earth science and technology research and development enterprises, established in accordance with the principles of marketization and the rule of law. China rare Earth Group has settled in Ganzhou, Jiangxi Province, and the Ganzhou rare Earth Kingdom is well deserved. Ganzhou has 10% of the country's medium and heavy rare earths, and the rare Earth Research Institute of the Chinese Academy of Sciences has also settled in Ganzhou. The restructured giant will have 70% of China's annual mining of heavy rare earths and 40% of light rare earths, and is expected to become the world's dominant rare earth giant.

Xiamen Tungsten Industry (600549): Xiamen Tungsten Industry Co., Ltd. (referred to as "Xiamen Tungsten Industry") has been involved in the rare earth industry since 2006 and is one of the six major rare earth groups established by the state. An industrial system has been formed from rare earth mine development, smelting separation, rare earth functional materials and scientific research and application. Its products include rare earth oxides, rare earth metals, rare earth permanent magnet materials, rare earth phosphors and so on.

Fujian Changting Jinlong rare Earth Co., Ltd. (referred to as "Jinlong rare Earth"), a wholly owned subsidiary of Xiamen Tungsten Industry, is a leading enterprise in Fujian rare earth industry, mainly engaged in rare earth separation, intensive processing and R & D and application of rare earth functional materials. The company covers an area of 800mu, with a construction area of 200000 square meters, with a total investment of 4 billion yuan. at present, it has built 5000 tons of rare earth separation, 3000 tons of rare earth metals, 2000 tons of high purity rare earth oxides, 1300 tons of tricolor phosphors, 6000 tons of NdFeB magnetic materials, and 2500 tons of NdFeB surface treatment production lines. It has a relatively complete industrial chain from rare earth mining-rare earth separation-rare earth metals-intensive processing (phosphors, magnetic materials).

Guangsheng Nonferrous (600259): one of the core enterprises of Guangdong rare Earth is Guangsheng Nonferrous Metals Co., Ltd. (referred to as "Guangsheng Nonferrous Metals"). Guangsheng Nonferrous is the only listed company on the main board in China that focuses on ion adsorption medium and heavy rare earths. It has established a relatively complete rare earth industry system covering mining mineral processing, smelting separation, intensive processing, scientific research application, import and export trade circulation. Four rare earth smelting and separation enterprises in Guangdong Province have all rare earth mining rights and a total separation capacity of 14000 tons per year. In Meizhou, it has a rare earth metal production line connecting upstream smelting separation and downstream deep processing of magnetic materials; in downstream deep processing, it has invested 600 million yuan in a joint venture with TDK Co., Ltd., a top 500 company in the world, to build a high-end magnetic material production line with an annual output of 4000 tons / year. At present, Guangsheng Nonferrous is preparing to build high-end rare earth permanent magnet materials and other rare earth functional materials and application projects.