Enrichment of rare earth minerals from raw ore

Rare earth minerals in nature and often symbiosis with barite, calcite, apatite, silicate ore minerals. Due to the different mineralization reasons of minerals, the occurrence and content of rare earth elements in minerals are also different. Among the rare earth-bearing ores currently mined, the content of rare earth oxides is only a few percent or even lower. To meet the needs of rare earth metallurgical production, we are satisfied by processing methods, and other rare earth ores before smelting separated, enriched rare earth minerals. The content of rare earth oxides in minerals after mineralization and enrichment can reach 60% to 70%. The minerals enriched in rare earths are often referred to as rare earth concentrates, and the content of rare earth oxides in concentrates is called the rare earth grade of concentrates.

Mineral processing is the process of extracting valuable minerals from raw ore by using the difference between the physical and chemical properties of the minerals in the original ore and adopting corresponding technical measures. Due to the variety of rare earth minerals and species, the mineral composition in the original ore varies, so the beneficiation process used for different mines is different. Table 1 lists some mineral processing characteristics of minerals often associated with rare earth minerals. The mineral processing techniques of the five most important rare earth minerals in the industry will be briefly introduced below based on these characteristics.

Table 1 Beneficiation characteristics of major minerals

I. Beneficiation of fluorocarbon antimony-monistite mixed type ore

Sedimentary metamorphism in the Bayan Obo area of ​​Inner Mongolia, China - Fluoride, sodium metasomatic type 铌-rare earth-iron deposits contain a variety of rare earth minerals, of which industrial value is fluorocarbon antimony ore and monazite, the ratio of the two is at (9: 1) ~ (6: 4) fluctuates between. The original ore contains REO 5% to 6%. Other minerals include hematite, magnetite, rare metal ore, barite, calcite, dolomite, quartz, feldspar, etc. There are six main processes for mineral processing for the characteristics of ore:

1 priority flotation iron process;

2 mixed flotation-foam separation iron process;

3 preferential flotation fluorite-rare earth-iron process;

4 semi-priority semi-mixed flotation iron process;

5 weak magnetic-semi-priority semi-mixed flotation-re-election-flotation combined process;

6 Weak magnetic-strong magnetic-flotation combined process.

Figure 1 shows the weak magnetic-strong magnetic-flotation combined process. The rare earth concentrate of this rare earth concentrate can reach more than 60%.

Figure 1 Joint flow chart of weak magnetic-strong magnetic-flotation in a concentrator of Baotou

Second, the dressing of monazite

Monazite mainly exists in deposits related to alkaline rock-alkaline ultrabasic rocks, alkaline rock-carbonates, granites , weathering crusts, sand mines, etc. Because of the different mineral composition of the original ore in the monazite, the process of beneficiation used is different. Australian monazite produced in heavy sands, other components of the mineral magnetite, iron titanium, rutile, zircon and other minerals. The Southport concentrator in the country uses a re-election-magnetic separation process to extract monazite. India and South Africa monazite containing apatite mineral, zircon, magnetite, yellow copper ore, galena, and the like. The mine uses a re-election-flotation process to recover zircon while selecting monazite (see Figure 2).

Figure 2 Process flow of the Steen kamps-Kraal concentrator in South Africa

3. Beneficiation of bastnasite

Bastnasite may be present in alkaline rock-alkaline ultrabasic rocks and alkaline rock-carbonate deposits. Significantly, it is an alkaline granite deposit in the Maoniuping area of ​​Suining County, Sichuan Province, China, and a carbonate-type rare earth deposit in the Mountain Pass area of ​​California, USA. The US Mountain Pass concentrator uses a re-election-flotation-magnetic separation process. China uses a re-election-flotation-magnetic separation process to recover fluorocarbon antimony ore according to the characteristics of the yak mine. Figure 3 shows the beneficiation process of the yoghurt fluorocarbon antimony ore in Sichuan.

Figure 3 Flow chart of beneficiation of yoke sulphide ore in Sichuan

4. Beneficiation of xenotime

Xenotime sand deposits found mainly in Malaysia, Thailand, Indonesia, Sri Lanka and southern regions of our country. The minerals associated with xenotime are mainly gangue minerals such as zircon, ilmenite, rutile, iron ore and quartz, mica and feldspar. During the beneficiation process, valuable minerals are recovered separately based on the characteristics of the mineral. CENTRAL granite hydrothermal area of feldspar - quartz vein wolframite deposits except wolframite, scheelite, and also contains a small amount of xenotime gadolinite, monazite, Greek black gold, fluorocarbon In antimony ore, rare earth elements are mainly enriched in xenotime. Other minerals of the ore include siderite, limonite and feldspar, quartz minerals, and minerals such as manganese garnets and sulfides. In order to recover tungsten ore and xenotime, the ore dressing process uses a flotation process to recover scheelite, wolframite and xenotime at a time according to the different planktonic properties of the minerals (the beneficiation process is shown in Figure 4).

Figure 4 Test procedure for recovery of xenotime from fine mud tungsten concentrate

After ore dressing, the product in the tank is 62% containing WO ₃ and the recovery rate is 79% wolframite. The main reason for the quality of the xenotime products in this process is scheelite. To improve the quality of xenotime, two times selection of paste is added, then water glass, sodium carbonate was warmed (85 deg.] C) treated with a mixed flutter collector (oleic acid: kerosine oil = 1:1: number :2 0.2) Flotation of scheelite can obtain a phosphonium ore concentrate with Y ₂ O ₃ 8% to 10% and a recovery rate of 34%.

5. Beneficiation of brown earth mine

The brown earth mine is mainly found in the deposits of granite and granite weathering crust. Deposits dominated by brown earth mines are rare. The brown castor weathering crust deposit in a central and southern part of China is currently the world's largest rare earth industrial deposit with the largest number of rare earths. The main mineral components in the ore are brown gangue, monazite, brown pebbles, zircon, ilmenite, rutile and quartz, feldspar, mica and other gangue minerals. Niobium and rare earth are present in minerals of different particle sizes. In order to effectively recover lanthanum and rare earth, the beneficiation process is carried out in two steps: in the first step, a coarse concentrate containing Nb ₂ O ₅ 1.821% is initially selected according to the distribution of lanthanum and rare earth in each fraction of the ore; In the second step, the coarse concentrate is selected by magnetic separation-re-election-flotation (see the selection process in Figure 5) to obtain a concentrate containing Nb ₂ O ₅ 37.75%. In addition, 61.82% monazite concentrate containing REO and zircon concentrate containing ZrO ₂ can be obtained during the beneficiation process.

Figure 5 Selected process of brownstone ore weathering crust ore

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