Practical application of electrification

At present, most of the electrifications in the world are used for selected operations. Before the selection, the materials are generally re-elected or other mineral processing methods to obtain coarse concentrate. The use of electrification is to improve the concentrate grade and to obtain qualified concentrates, and the other is to separate the symbiotic minerals for comprehensive recovery, or both. Electrostatic separation now has grown to applications in other industries, in mineral processing is also part of practice for direct election ore, the main focus of this chapter is to introduce non-ferrous, rare and ferrous metals mining application electric separation practices.
1. The electro-selection of scheelite and cassiterite in non-ferrous metal ore often coexist, which is common in all tungsten mines in China (of course, mainly black tungsten ore), which are all pre-gravity The enrichment results in a mixed coarse concentrate, and the black tungsten ore is separated by strong magnetic separation, and the remaining part is a mixed ore mainly composed of white tungsten and cassiterite. Because the two have similar proportions (white tungsten 5.9~6.2; cassiterite 6.8~7.2), they are not magnetic, so the two methods can not be separated by re-election and magnetic separation. Generally, coarse particles are used for floating in the production, and fine particles are used for flotation. The effect is very poor and the efficiency is extremely low. However, the electrical properties of the two are significantly different. The scheelite has a dielectric constant of 5 to 6, a resistance of more than 10 ¹² Ω, a dielectric constant of cassiterite of 24 to 27, and a resistance of only about 10 ⁹ Ω. For this reason, the use of electro-election is the most effective method, which is economical, simple in process, free of chemicals, and does not cause pollution. Therefore, most of the methods are used at home and abroad.
Domestic use of floating or flotation has long been used, and the actual use of electricity in production is after 1964. Under the conditions at that time, the electric sorting machine developed had only one Φ120 × 1500mm double-roller electric sorter, and this equipment was still used more frequently. Due to the influence of historical conditions, the efficiency of electro-selection is very low, and the process is complicated. The final concentrate quality and recovery rate are not ideal. In particular, only the coarser grains (greater than 60-100 mesh) of white tungsten can be sorted. Tin sill, but less than this size can not enter the electrification, and the return amount of the mine is very large.
The actual process of electrification of scheelite in a mine in Hunan is introduced. The plant uses a Φ120 × 1500mm double-roller electric separator (voltage 17.5kV), the flow of which is shown in Figure 1.
The raw material is the mixed coarse concentrate after re-election, and the sulfide ore is removed by lifting and floating, and then electrified after drying. When the material enters the power contained in the mineral is selected from: 70% scheelite, cassiterite about 15 to 20% hematite and limonite about 5%, bismuthinite 2%, 1% molybdenite about. In addition, there are a small amount of zircon, pyrite, sphalerite, fluorite, wolframite, bismuth and the like foam. Due to the desulfurization by the stage, the raw materials contain sulfur, phosphorus , arsenic and copper .

Figure 1 Flow chart of electrification of scheelite in a mine in Hunan [next]

The process test shows that the recovery rate of white tungsten is only about 60%, and the grade is as high as 74.51%, but the tin content in the white tungsten concentrate is often more than 0.2~0.3%, rarely less than 0.2%; the electrification of cassiterite can not be obtained. The concentrate must be subjected to secondary magnetic separation and re-election (magnetic separation to wolframite and other magnetic minerals), and the final tin concentrate has a grade of only 47.3% (Sn), and the recovery rate is about 90%, but contains WO. ₃ is more than 20%, which is an unqualified concentrate.
For the white tungsten and cassiterite of the above mines, a large number of tests were carried out using DXJ type Φ320 × 900mm high-voltage electric separator. When the materials less than 1mm were electrified, the electro-election process was greatly simplified, only one time. Select high-quality scheelite concentrate, WO ₃ ≥70% in scheelite concentrate, recovery rate of 90~95%, tin (Sn) less than 0.2%; -0.42+0.1mm The grain size is only one time. The WO ₄ is 70.4%, the (Sn) is 0.14~0.18%, the ε _WO3 is 96%, the cassiterite recovery rate is 96~97%, and the cassiterite grade is once. The selection can reach more than 40%. If the tin concentrate is selected once, the grade can reach more than 50%, and the recovery rate is 96%.
A selected factory in Guangdong also uses the above Φ120 × 1500mm double-roller electric separator. The raw materials come from the black and white tungsten coarse concentrate of each mine. The same is pre-screened into various levels, and then the black tungsten concentrate is separated by dry strong magnetic separation, and the remainder is white tungsten, cassiterite, sulfide ore, mica , apatite and quartz . The particles are floated to the sulfide ore, and then the white tungsten and the cassiterite are enriched by a shaker, and the obtained concentrate is dried and then electrified. The difference is that the material is divided into narrower grain sizes: -2+1.4, -1.4+0.83, -0.83+0.2 and -0.2mm. Each particle fraction enters the electrification separately, and the electro-optic process is generally the same as that of a certain mine in Hunan (five times of electrification), and finally the total scheelite concentrate contains WO ₃ >65% and Sn is 0.2-0.3%. ε _WO3 ≥ 80%.
Now the plant does not need Φ120 × 1500mm double-roller electric separator, and after using 60kV high-voltage electric separator, the amount of white tungsten concentrate is increased by about 20%, tin concentrate production is increased by 22%, and tin recovery rate is increased by 9.55%. It can be seen that the use of high-voltage electrification is more effective than the low-voltage electrification in the past.
Japan's Otani Mountain Concentrator, which treats coarse concentrates 60t per month, also uses electro-selection to sort scheelite and cassiterite. The raw material contains sulfide ore and is first removed by flotation. The equipment used is an electric separator with Φ125 × 500 and Φ125 × 1000mm and a voltage of 20kV. The raw materials are narrowly classified into individual particle sizes such as +10, -10+20, -20+40, -40+80, -80+150 mesh (or 180 mesh). The magnetic minerals are first removed by magnetic separation, and then electrified several times. Only the recovery rate of white tungsten was reported to be 95%, no white tungsten grade and its tin content and tin recovery rate and cassiterite grade were observed.
In addition, the Soviet Union has conducted a lot of research on stellite cassiterite containing various minerals in raw materials. The main raw material of cassiterite (Sn 9.7%) and scheelite (WO ₃ 7.9%), followed by titanium, iron, monazite, quartz, and the like. The particle size is 0.1~0.6mm, and the process flow combining electric and magnetic separation is adopted. After multiple sorting, the results are shown in Table 1.

From the above results, the effect is not outstanding, and the finest grade can only reach 150 or 180 mesh. In addition, electrification can also be used for the selective separation of black and white tungsten ore.
Second, the elective of rare metal ore
(1) Electrification of ilmenite and rutile
Due to the needs and development of the military industry and the needs of other industries, the demand for ilmenite and rutile has increased. According to incomplete statistics of available data, the annual production of titanium concentrates in the world is more than 4.5 million tons.
Ilmenite and rutile are divided into primary ore deposits, terrestrial sand mines and coastal sand mines. However, regardless of primary ore deposits, they must be pre-enriched by gravity ore dressing and then electrified. Otherwise, it is extremely uneconomical. In addition, smelting and various industries require titanium concentrates containing more than 48% TiO ₂ . The ilmenite from a factory in Sichuan was first re-elected, then dried by hot air, and classified by electric separation. The electric separator used was a Φ300 × 2000mm three-barrel high-pressure electric separator. The concentrate contained nearly 48% of TiO ₂ . [next]
As far as the world is concerned, most of the ilmenite and rutile are currently recovered from coastal sand mines. This is currently the most important source, and production is now increasing. The first is the recovery of ilmenite and rutile in the coastal sand mines in Florida, USA. The annual production of titanium concentrates in the United States is over 400,000 tons. Since then, Australia has recovered titanium minerals from coastal sand mines, ranking first in the world, with at least 1.5 million tons per year. In recent years, there are eight companies in the country that use electricity to recover ilmenite and rutile. Sierra, West Africa, now produces 100,000 tons of rutile and ilmenite concentrate annually. In addition, the Soviet Union also used electro-selection to sort out the titanium concentrate of the sand mine, with an annual output of more than 100,000 tons. Other countries also recover titanium minerals from coastal sand or land sand ore, and the annual output is not low. China's coastal mines have a considerable amount of resources, and are currently concentrated in Hainan and Guangxi coastal areas of Guangdong, recycling a certain amount each year, but the output is not high.
The most prominent feature of seashore sand mines is that the minerals have been dissociated by the monomers, so there is no need for a large amount of operations such as crushing and grinding in the front. Generally, the weight of minerals per cubic meter of beach sand varies from 1 to 3 kg, and Another advantage is that the fine-grained grade (-150~200 mesh) is extremely low. These sea sands are coarse ore concentrates of the type containing magnetite, ilmenite, rutile, zircon and monazite, which were selected from the re-election plant on the waterfront, and then selected on the seashore or land. The electrification is the main selection method for qualified titanium concentrate, lead stone and monazite.

Figure 2 Flow chart of a factory in Guangdong

For example, the main coarse concentrate of a selected plant in the south is from Hainan Island. The raw materials are pre-extracted on the waterfront or land by re-election method, and then concentrated to the plant for selection. The TiO ₂ containing titanium minerals in the raw materials of the selected plant is 30~38%, ZrO ₂ is 6~7%, and the total rare earth TR ₂ O ₃ is 0.63~0.7%. The mineral composition is ilmenite, zircon, rutile, monazite, xenotime , magnetite, limonite, white titanium, and a small amount of cassiterite, gold, antimony ore. The gangue minerals are quartz, garnet , tourmaline , epidote, cross stone and kyanite. The process used is shown in Figure 2.
Since the raw materials come from various regions and the nature is also complicated, the process adopted is also complicated, but it has flexibility. The sorting indicators are shown in Table 2.

The electric separator used in the plant is a Φ120 × 1500mm double-roller electric separator (20kV). The selection of coastal sand mines in Australia mainly relies on electrification to obtain high-quality titanium concentrate, using the American Carpco high-voltage electric separator, and also magnetic selection and selection, and each year to obtain high-quality titanium concentrate 100000t. , rutile 65000t, zircon 9000t. [next]
Florida is famous for its titanium-producing concentrates. It is said to be very effective after using the Carpco-type high-voltage electric separator and the process flow of Figure 3.   

Figure 3 Flow chart of the principle of electrifying sand mines in the United States

The ore is re-elected coarse concentrate or flotation coarse concentrate, containing 80~95% heavy minerals, and the ore size is -16+400 mesh. It is sorted by Carpco type electric separator, and the ore is preheated to $23. The processing capacity of each device is 14t/h; the maximum is 50t/h. The final concentrate obtained is calculated as titanium-containing minerals with a yield of 99% and a recovery rate of 98%. The index is relatively advanced.
(2) Electrification of antimony ore
There are many kinds of minerals containing antimony, and it is more meaningful to use antimony ore with high antimony. In the past 20 years, due to the development of the military industry, the demand for metal bismuth has increased, and the demand of other industries has increased, so the output has also increased. According to available materials, the world's annual production of antimony concentrates has exceeded 1,000 tons. Mineral tantalum-containing niobium power can not all selected separation, only tantalite, heavy tantalite, columbite, tantalum, manganese tantalite, niobium, titanium, tantalum, niobium, titanium, calcium, cerium, niobium ore and iron ore It has good conductivity and can be separated as a conductor in the electric selection, while pyrochlore and fine spar are poor conductors and cannot be separated by electric separation.
In the world, the ore grades of antimony ore produced in countries such as Nigeria and South Africa are high (more than an order of magnitude higher than domestic ones). In addition, Malaysia, the Philippines, India and Thailand also recover a portion of the coltan from the sand mine. The content of the ore is not high, and the production of the Soviet Union is also growing, and the research and production in this area are highly valued.
China's antimony ore has many resources, some of which are Weijing granite primary deposits, and some of which are Weijing granite weathered deposits and sand deposits. Most of them use re-elected shakers to concentrate on coarse concentrates, and then use magnetic and electric separation. Choose to obtain the final antimony concentrate. At present, domestic demand for concentrates contains (Ta, Nb) ₂ O ₅ > 40%, and tantalum (Ta ₂ O ₅ ) is higher than 20%, but the proportion of ore that is currently mined is higher than that of tantalite. Big, and the performance of the cockroach is far worse.
According to the situation in China, the coarse concentrate obtained from the re-election of the original ore is about 2~4% (Ta, Nb)-2O ₅ , and contains a large amount of gangue minerals such as pyrite, tourmaline and bubble ore. It is garnet, followed by quartz, feldspar and mica. The use of strong magnetic separation efficiency is not high, mainly garnet is also a weak magnetic mineral, its magnetic is similar to the antimony ore, it is difficult to effectively separate them. The Φ120 × 1500mm high-voltage electric separator has poor sorting effect or can not be sorted.
DXJ type Φ320 × 900mm high pressure drum type electric separator has been applied in some domestic antimony ore (such as Xinjiang Concentrator), and generally achieved good results. Because in the coarse concentrate, the antimony ore belongs to the conductor ore, and a large number of garnet, quartz, feldspar, mica and zircon are all non-conductor mines, so they can be effectively separated by electro-election. The process and results of sorting the high pressure electric separator into the antimony ore are shown in Figure 4 and Table 3.

Figure 4 Yankuang electrification process