Since 1751 the Swedish chemist A. Cronztedt silicon cerium stone found in 1987, another Swedish amateur mineralogist Arrhenius CA (CA Arrhenius) found a new mineral in 1794 by the Finnish chemist Y. Gadolin named gadolinite. Murrisk (JA Marisky) obtained from the fission products of uranium promethium up in 1947 the United States J. a, before and after almost 200 years, was filled with a rare earth element on the periodic table The name. It has been ascertained that the content of rare earth in the crust is 0.01% to 0.02% by weight of the crust, wherein lanthanum, cerium, praseodymium, neodymium, yttrium, and in the abundance of igneous upper crust, more than tungsten, molybdenum, cobalt, lead, Therefore, rare earth is not a very scarce resource. With the development of science and technology, rare earth plays a greater role in the national economy and has wider use.

Rare earth treated steel metallurgical industry, rare earth rare earth zeolite cracking ductile iron agent, widely used in the petroleum industry; an optical glass, such as polishing powder kinescope; single rare earth oxides can produce a variety of optical glass, Anti-radiation glass; Ni- MH battery (Ni MH) is a green power source with high specific capacity, high current charging and discharging performance, and future development of electric vehicles; rare earth permanent magnet materials for computer and communication; magnetic laser, magnetostriction , rare earth magnetic materials for magnetic refrigeration and magnetic refrigeration refrigerators; rare earth micro-fertilizers for agriculture. The various magical properties and functions of rare earths have yet to be studied and found. To fully understand the strategic position of China's rare earth resources, it will be an important resource for the development of high-tech industries in the 21st century.

China's four major rare earth deposits (about 95% of China's total reserves) are basically discovered and discovered after the founding of New China in 1949. So far, China's rare earth oxidation has been proven. The industrial reserves are 3,600,000 tons (visual reserves of hundreds of millions of tons), accounting for about 80% of the world's proven rare earth reserves. In addition, the light, medium and heavy rare earth elements are complete. In the southern ion-type rare earth resources (ie, weathered and leached rare earth ore), the content of heavy rare earth elements is high, and its reserves account for 90% of the world reserves. The distribution of rare earth elements in rare earth minerals from different producing areas in China is shown in Table 1.

Table 1 Distribution table of rare earth elements of major rare earth minerals in China (%)

In 1997, the total production of rare earth concentrates in China was 53,250 tons, and the output of rare earth smelting products was 46,500 tons, accounting for 70% of the world's total rare earth production. The mineral processing technology has reached the world's most advanced level, from a large rare earth resource country to a large producing country that can produce various rare earth products. The four rare earth mine resources and ore dressing production processes are as follows.

I. Baotou Steel Baiyun Ebo Iron and Rare Earth Deposit

In July 1927, Mr. Ding Daoheng discovered iron ore on his way to the northwest. In 1935, Professor He Zuolin found rare earth minerals in the ore specimens retrieved by Mr. Ding Daoheng. After the founding of the People's Republic of China, the 241 Geological Team of the North China Geological Bureau conducted a detailed survey of the main and eastern mines, and determined the iron ore and rare earth reserves, indicating that Baiyun Obo is a large iron ore and a large-scale rare earth deposit.

(1) Ore properties

The iron, rare earth and strontium polymetallic symbiotic large deposits in the Baiyun Obo deposit, Baotou, have been found to have 71 elements and more than 170 kinds of minerals. There are many ore types, among which rare earth reserves rank first in the world, and rare earth minerals are about There are 15 kinds, but mainly fluorocarbon antimony or monazite light rare earth mixed ore, the ratio is 7:3 or 6:4, accounting for about 80% of the national rare earth reserves. The symbiotic relationship between the useful minerals is close, the size of the inlaid cloth is fine, and the particle size of the rare earth mineral is generally between 0.01 and 0.074 mm. The useful minerals in the ore are magnetite, hematite, bastnasite, monazite, and strontium minerals. The main gangue minerals are smectite, sodium amphibole, calcite , dolomite, barite , and apatite. Stone, quartz , feldspar, etc. The chemical composition of Baotou iron oxide ore is shown in Table 2. The distribution of rare earth elements in rare earth minerals is shown in Table 1. Table 2 Table of main chemical compositions of Baotou Mine iron oxide ore (%)

(2) Rare earth ore dressing production process

Since the 1960s, the state has conducted many scientific and technological researches on the iron, rare earth and antimony beneficiation organizations of the Baiyun Obo iron oxide ore. It has studied more than 20 kinds of mineral processing processes in detail. In 1990, the Changsha Research Institute of Mining and Metallurgy cooperated with Baotou Steel to successfully carry out industrial tests using two series of weak magnetic separation-strong magnetic separation-flotation recovery of iron and rare earth process to transform Baotou Steel Concentrator. The process is fully successful. It embodies the guiding ideology of “iron-based, comprehensive recovery of rare earth minerals”. Baotou Steel Concentrator has built eight production series (5 of which are treated with oxidized ore and 3 of which are treated with primary ore). The annual processing of raw ore is 9 million tons, and the annual production of iron concentrate is 3.5 million tons. 40,000 tons (REO). The iron oxide ore beneficiation series firstly grinds the original ore to -0.074mm, accounting for 90% to 92%, and the weak magnetic separation selects the magnetite. The tailings are coarsely selected under the condition of strong magnetic separator magnetic induction strength 1.4T, which will be red. The iron ore and most of the rare earth minerals are selected into the strong magnetic coarse concentrate. The coarse concentrate is selected by a strong magnetic (0.6-0.7t), and the strong magnetic selected iron concentrate and weak magnet concentrate are combined and sent to the anti-floating. Select and remove gangue minerals such as fluorite and rare earth with magnetic separation to obtain qualified iron concentrate. Strong magnetic medium ore (selected tailings) containing REO 9% to 12%, rare earth recovery rate of 25% to 30% as flotation rare earth raw materials, using H2O5 (o-hydroxynaphthyl hydroxamic acid), water glass, J102 (foaming agent) a combination of agents, flotation of rare earth minerals in a weakly alkaline (pH 9) slurry, after a rough selection, a single sweep, a second selection to obtain a mixed rare earth concentrate (carbon bromide and monazite) grade 50% ~ 60 %, average 55.62%, rare earth recovery rate of 12.55%; rare earth concentrate level of 34.49%, rare earth recovery rate of 6.1%, total rare earth recovery rate of 18.56%, for flotation of strong magnetic medium ore The recovery rate is 72.75% (the grade of rare earth concentrate is adjusted according to market demand). The process of rare earth beneficiation is shown in Figure 1.

Fig.1 Process flow of flotation of rare earth minerals in strong magnetic separation of Baotou Bayou O Mine

(III) Innovation and development of rare earth mineral flotation reagents

Before 1975, rare earth mineral flotation collectors used fatty acid collectors. The rare earth minerals in Baotou ore were associated with fluorite, calcite, barite, hematite, etc., and these minerals floated when flotation of rare earth minerals. It is difficult to separate, preferential flotation rare earth or mixed flotation-separation of rare earth minerals can only obtain rare earth concentrate containing about 20% REO. In order to obtain high-grade rare earth concentrate, the tailings of the ore weak magnetic separation magnetite are subjected to semi-priority and semi-mixed flotation [adding NaOH, Na2SiO3, and oxidized stone soap combination agent, and preferentially in strong alkaline pulp (pH11)) Flotation of fluorite, barite and other easy-floating minerals, and then adding Na2 SiF6 activated rare earth minerals (mineral pH 8 ~ 9) to the slurry, mixing rare earth and some fluorite with oxygen oxide wax mixture, mixing The flotation of the rare earth foam is re-elected by a grooved slime shaker to obtain a re-selected rare earth concentrate containing about 30% REO. The re-election concentrate, such as the reuse of fatty acid collectors, has little effect on flotation selection. Therefore, from 1966 to 1978, Baotou Steel Concentrator could only produce rare earth concentrates containing 20% ​​to 40% of REO for rare earth smelting, thus affecting the effective development of China's rare earth smelting, extraction, separation and application industries. status. The chemical composition of the re-selected rare earth concentrate is shown in Table 3.

Table 3 Table of chemical composition of re-selected rare earth concentrates (%)

At the end of 1975, the Guangdong Branch of the Nonferrous Metal Research Institute used a large amount of water glass to suppress gangue minerals (Na2CO3 as a pulp pH adjuster, Na2SiF6 as a rare earth mineral activator) in the laboratory flotation re-election of rare earth concentrates, using C5~ 9 Hydroxamic acid flotation of rare earth minerals, breakthrough progress, and obtained rare earth concentrate containing REO >60%. In October 1976, a semi-industrial test of 30 t/d was carried out at Baotou Nonferrous Metals Plant, which verified the results of small tests. Since then, the prelude to the production of high-grade rare earth concentrates from the Baiyun Obo ore has been opened. Due to the weak ability of C5-9 hydroxydecanoic acid to collect, it requires multiple sweeps and the drug is not stable in production. In 1979, Baotou Metallurgical Research Institute successfully developed cycloalkyl hydroxamic acid (used as a ring raft when used). Ammonium acid), applied in industrial production at the end of the year, adopts a coarse and fine closed circuit process. When the ore (re-elected concentrate) grade is 3.82%, the rare earth grade can be produced as 63.74%, and the flotation operation recovery rate is 66. 75% of rare earth concentrate. From 1979 to 1985, the production of rare earth concentrates with cycloalkyl hydroxamic acid was good, but the selectivity of cycloalkyl hydroxamic acid was also poor during the production process, and there were many kinds of adjusting agents. Sodium fluorosilicate is inconvenient to use; in 1985, Baotou Rare Earth Research Institute (former Baotou Metallurgy Institute) successfully developed H2O5 (o-hydroxynaphthyl hydroxamic acid) collector. The test results show that it has good selectivity to rare earth minerals and greatly simplifies. Flotation pharmacy system, only need to add water glass, pulp flotation pH9 or so,

In July 1986, an industrial test was carried out at the concentrator, using a coarse and fine closed-circuit process. When the grade of the ore (re-selected concentrate) was 23.12%, the grade was 62.32%, and the recovery rate of rare earth flotation was 74.74. % of rare earth concentrate. Hydroxamic acid (hydroxamic acid) can form stable five-membered ring conjugates with transition metal ions such as rare earth, cerium (strontium) and iron. Therefore, hydroxamic acid (salt) acts as a collector rather than fatty acid (salt). The rare earth minerals have high selectivity and high flotation recovery.

The production results show that the non-polar group of hydroxamic acid has a great influence. H2O5 has better effect than alkyl hydroxamic acid, and may mainly form π•π conjugated double bond with aromatic hydrocarbon hydroxamic acid. The electron cloud density on the atomic "O" is stronger than the alkane hydroxamic acid. Since H2O5 needs to be added with a large amount of alcohol in the process of adding a large amount of alcohol to form o-hydroxynaphthyl ammonium hydroxide, it is complicated to prepare in the production workshop, and the solid particles of H2O5 cannot be safely dissolved and reacted to form an ammonium salt, 1992~ In 1994, Baotou Steel Rare Earth Research Institute (formerly Baotou Rare Earth Research Institute) successfully developed H316 (improved on H2O5) instead of H2O5, and used industrial test with water glass and foaming agent J103 (paste pH 7~8). The comparison of industrial test results of H 3 16 and H2O5 shows that H316 has an improved recovery rate of 10.09% compared with H2O5 when the grade of rare earth concentrate is the same (53%), and H316 does not need to be dispensed with ammonia water, which improves the working environment, per ton of rare earth. The cost of concentrate was reduced by 44.22 yuan, and the cost of chemicals was reduced by 7.13%. It fully demonstrates that with the continuous improvement and innovation of rare earth flotation reagents, it promotes the development of rare earth mineral processing technology in China, and at the same time makes the technology of rare earth flotation in China reach the international leading level.

Second, Shandong Weishan rare earth mine

(1) Mine and ore properties

The mine is located in Tanghu Township, Weishan County, Shandong Province. It was discovered by the original Jinan Geological Bureau and the 802 team during radioactive aerial survey from 1958 to 1962. The geological survey of the second team of the Provincial Geological Bureau from 1970 to 1974, the census report in December 1975. It is pointed out that the rare earth reserves in 0.85km2 are about 2.55 million tons (REO), and the shallow parts of the main ore veins 1, 3, 4 and 12 are inspected in detail. The C+D reserves are 120,000 tons (REO), and the average geological grade is 3.13. % is a quartz-barite-carbonate rare earth deposit with simple composition of minerals and gangue. It is mainly composed of fluorocarbon strontium ore and fluorocarbon strontium ore, accompanied by barite, calcite, quartz and fluorite. The rare earth mineral inlay has a coarse grain size, generally ranging from 0.5 to 0.04 mm, and is an easy-to-use ore. The main chemical components of the ore are shown in Table 4. The distribution of rare earth elements in rare earth minerals is shown in Table 1.

Table 4 Table of main chemical compositions of Weishan ore (%)

(2) Beneficiation process and sorting technical indicators

Weishan rare earth processing plant in 1982 formally set up factories, small-scale, original ore milled to -0.074mm 65% to 75%, adding sulfuric acid, sodium silicate, oleic acid and kerosene, in weakly acidic (pH5) pulp The rare earth minerals are flotation, and the rare earth concentrate containing REO is obtained by one rough selection, three sweeps, and three times. Between 1986 and 1989, the supporting transformation was carried out, and the mining was transferred to underground mining. The rare earth grade of the ore was reduced to 3% to 4% (the open surface ore contained REO was relatively high, generally 5% to 10%), and the original flotation agent was used for sorting effect. Unsatisfactory, in 1991, the rare earth special effect collector L102 (C6H4OHCONHOH), water glass, L101 (foaming agent) combination agent was used to float rare earth minerals in weakly alkaline (pH 8 ~ 8.5) pulp, and obtained REO> 60% rare earth concentrate with a rare earth recovery rate of 60% to 70%, and a rare earth concentrate with a REO of 32% and a recovery of 10% to 15%. From 1998 to 1999, the annual processing of ore was 40,000 tons, with an annual output of 3,500 rare earth concentrates containing REO 60%.

Third, rare earth resources in Liangshan, Sichuan

The rare earth resources in Liangshan area are mainly distributed in the Wei Niuping rare earth mining area of ​​Suining County, followed by the Dechang rare earth mining area. The annual processing of raw ore is 150,000 to 200,000 tons, and the annual output of rare earth concentrate is 10,000 tons.

(A) mining and ore properties Maoniuping rare earth mine in Sichuan Province Bureau of Geology and Mineral Resources 109 geological team conducted in 1985 and 1986 lead, zinc ore spot checks found in the census work. The deposit is a basic pegmatite-calcite carbonate rare earth deposit. The rare earth mineral is mainly fluorocarbon antimony ore, a small amount of silicon- titanium ore and fluorocarbon calcium antimony ore. The associated minerals are mainly barite, fluorite and iron. , manganese and other minerals, a small amount of galena. In 1994, the geological report of the mining area survey (including detailed investigation) pointed out that the C+D+E grade reserves were 21.46% tons (REO) and the industrial reserves were 1 million tons. The average grade of 3.70 percent rare earth, is a large rare earth deposits that REE europium, yttrium and the like, higher than the same type of heavy rare-mine grade. The distribution of rare earth elements in rare earth minerals of this deposit is shown in Table 1. The ore is divided into lump ore and powder ore from the particle size. The mineral inlay size of the lump ore is coarse, generally >1.0 mm, of which the fluorocarbon antimony ore is generally 1 to 5 mm, the particle size is extremely coarse, easy to grind, and the monomer dissociation degree. it is good. Powdered ore is the product of weathering of the original rock. The weathering is relatively thorough. The local weathering depth is 300m, forming a black weathered slime that accounts for about 20% of the ore. They are iron-manganese amorphous oxide aggregates. The black weathered slime has a particle size of 80% below -320 mesh, containing REO2% to 7%, and contains strontium and barium. The main chemical components of the Maoniuping ore are shown in Table 5. Table 5 Table of main chemical components of Ya Niuping ore (%)

(II) Ore dressing technology and technical indicators

The ore produced in Maoniuping is a mixed ore with lump ore and powdery nature. The black slime affects the flotation of rare earth minerals. Therefore, it is very important to remove mud before flotation. Due to the easy selection of the ore, in the early stage of the discovery of the yakouping rare earth mine (in the late 1980s), the rare earth concentrate market was promising, and there were more than 100 small mining and concentrating plants. The mine was dug and dug, and the small ore dressing planted everywhere. In 1995, it was reduced to 39 years of concentrating plants (up to 20 in early 2000), and there are three representative mineral processing processes. 1. Single re-election process. The ore grinding to -200 mesh 62% is divided into four grades by hydraulic classification tank, which are separately sorted on the grooved silt shaker to obtain three fluorocarbon antimony concentrates containing REO 30%, 50% and 60%. The total job recovery rate was 75%. 2. Magnetic separation-re-election combined process. The ore containing REO 3.2% was subjected to magnetic separation (weak magnetic separation, strong magnetic separation) to obtain a magnetic product containing REO 5.64%. The magnetic separation operation recovery rate was 74.2% (yield 42%), and the magnetic separation was coarse. The concentrate is divided into four grades by hydraulic classification tank, which are re-elected by shaker respectively. The re-election of total concentrate contains REO52.3%, the yield is 3.56%, and the rare earth recovery rate is about 55%. 3. Re-election-flotation process. The first section of the original ore is ground to -200 mesh, accounting for 50%. It is divided into four grades by hydraulic classification tank, which are re-elected by shaker (removing the slime and some light specific gravity gangue) and re-electing with REO3 0%. Crude concentrate, rare earth recovery rate of 74.50%. The coarse concentrate is re-ground to -200 mesh and 70%, and is floated with a combination of sodium carbonate, water glass and C5-9 hydroxydecanoic acid, and floated by a coarse, one sweep, and a closed circuit process to obtain a REO 50%. ~60% of rare earth concentrate, rare earth recovery rate of 50% to 60%, the process flow is shown in Figure 2.

Figure 2 Flow chart of re-election-flotation process of yakouping rare earth mine

The three beneficiation processes are more widely used in the re-election-flotation process (such as Changlan Rare Earth Co., Ltd.), but the recovery rate of rare earths is relatively low. The combination of re-election of coarse concentrate flotation agent into water glass, H2O5 and phthalic acid 1:1 mixed agent was floated under the condition of slurry pH 8～9, and the grade of rare earth concentrate was 69.09%, flotation operation. The recovery rate is 89.82%, and the recovery rate of rare earth in the re-election-flotation process is 66.92%. The mineral processing technical indicators have been significantly improved. The content of this article is for reference only and does not constitute investment advice. Investors operate on this basis at their own risk.

4. Weathering shell leaching type rare earth ore

China's weathering crust leaching rare earth ore first discovered in the late 1960s in the Longnan foot cave of Jiangxi Province, after ion-adsorption heavy rare earth ore and Xunwuling ion adsorption light rare earth ore, successively in Nanling, Fujian, Hunan, Guangdong, Guangxi, etc. It has been found in the region, but it is concentrated and large in Jiangxi. Ion-adsorbed rare earth ore is a unique new type of rare earth deposit in China that has not been reported abroad. After more than 20 years of research, it has been found that this type of mine has a wide distribution of land, large reserves, low radioactivity, easy mining, simple process of extracting rare earth, low cost and good product quality. The proven industrial reserves are 1 million tons (REO) and the prospective reserves are more than 10 million tons. At present, it produces 10,000 tons (REO) of REO>60% mixed rare earth concentrate.

(I) Ore nature The weathered leaching type rare earth ore-bearing rare earth-bearing granite or volcanic rock is formed by weathering for many years. The ore body is shallowly covered, the ore is loose, and the particles are very fine. Rare earth elements in the ore was 80% to 90% of ions adsorbed on kaolin, halloysite, mica, clay minerals, and water; adsorbed on the clay mineral rare earth cations are insoluble in water or alcohol, but strong electrolyte (e.g. Na Cl , (NH4)2 SO4, NH4Cl, NH4Ac, etc.) can undergo ion exchange and enter the solution and have a reversible reaction.

(II) Rare earth extraction process and technical indicators

1. Sodium Chloride Method After the discovery of the deposit in the late 1960s, the “Sodium Chloride Pool Immersion Process” was developed in 1970. It was the main method for treating this type of ore in the 1970s. The ore transported from the mining site is sent to a rectangular cement pool for immersion. The leachate is discharged from the discharge port of the filter layer at the bottom of the tank. The leaching residue is manually removed, and the leachate is precipitated in a saturated oxalic acid solution. The filtered cake is Rare earth oxalate, after burning, washing with water, and then burning to obtain a mixed rare earth oxide. 2. Ammonium sulfate pool leaching method The sodium chloride leaching method has a long leaching time, a large concentration of sodium chloride, a large consumption, and a large amount of sodium ion coprecipitation, which affects the burning product once, and the purity can only reach 70%. The complex process of burning the product water to elute sodium and then burning, and the leaching residue (tailing) contains a large amount of sodium chloride, causing the land to be salted and polluting the environment. Immersed ore and filtrate oxalic acid precipitation with 3% to 5% ammonium sulfate solution (due to the expensive oxalic acid, ammonium bicarbonate was used as a rare earth precipitant in the late 1980s, and it has been used in some factories and mines. Crystalline rare earth carbonate). The rare earth oxalate is once burned to obtain a mixed rare earth oxide containing REO>90%, and the filtrate is added with ammonium sulfate and returned for reuse. Compared with sodium chloride, ammonium sulphate has strong leaching ability, less dosage, less ammonium ion precipitation, and is more volatile when burning, and leaching does not cause soil salinization. The process flow of chemical beneficiation is shown in Figure 3.

Figure 3 Ammonium sulfate - oxalic acid extraction rare earth process

3, in-situ leaching method pool immersion process technology and equipment conditions are simple, easy to operate, and thus rapid development, blooming everywhere. However, the biggest disadvantage of the pool dipping method is the production of 1 t rare earth oxide. The surface area to be mined is 200-800 m2, the mining and stripping amount is more than 1000 m3, and the amount of tailing sand discharged is 800-1000 m3, causing serious damage to topsoil and vegetation, and soil erosion. Environmental pollution and waste of resources, the total recovery rate of rare earth is only 30% to 40%. In order to overcome these shortcomings, as early as 1980-1985, the rare earth mine workers put forward the idea of ​​the in-situ immersion method, and later formed the more systematic process technology through the "eight-five" scientific and technological research, the main content of the in-situ immersion method. That is, the ore containing rare earth is not taken out, but the well is drilled in the mining area or section containing the ionic rare earth ore. The immersion liquid is added through the surface injection well, and the ore is selectively passed through the permeation and ion exchange. A process for leaching and recovering rare earth ions. The recovery of the leaching solution has a negative pressure pumping and a water seal plugging method, and the former has a wide adaptability. The leaching solution is collected and precipitated with oxalic acid or ammonium bicarbonate to obtain a rare earth oxide product. The recovery rate of rare earth leaching is 70% to 75%, so that the landform, the surface and the vegetation are not damaged, and the rare earth leaching and the pool immersion are relatively low in cost. 1200 ~ 3000 yuan / t REO. After the scientific and technological research in 1990-1995, the in-situ leaching method was successful. Ready-made has been applied in some mines such as Longnan, Jiangxi.

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