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钽铌Selection theory and practice
I. 钽, 铌 and its application
(a) 钽 and 铌
Tantalum, rare metal, is located in the 6th period in the periodic table Category Group 5 element symbol Ta, atomic number 73, atomic weight 180.95 electron structure in a chemical reaction easily 2,8,18,32,11,2 Loss of the outermost 2 electrons and the outer layer of 3 electrons, leaving 8 electrons in the outer layer to become a relatively stable electronic layer structure, so it usually shows a price of 5. The base metal density is 16600 kg/m3 and the melting point is 3000 °C.
é“Œ, rare metals, in the fifth periodic table of the fifth cycle of the periodic table, element symbol 23, atomic number 41, atomic weight 92.91 electronic structure is !, 2,8,18,11,2 is also easy in chemical reactions Loss of the outermost 2 electrons and the outer layer of 3 electrons, leaving 8 electrons in the outer layer to become a relatively stable electronic layer structure, so it is usually +5 price. The base metal has a density of 8600 kg/m 3 and a melting point of 2415 ° C.é’½, é“ŒåŒæ—, similar electronic structure, physical and chemical properties are close, always symbiotic in nature.
(2) Uses of 钽 and 铌
The main use of germanium is as a capacitor. Tantalum capacitors have the advantages of high capacity, small size, high stability, long life, etc., and are widely used in the electronics industry and aviation industry, especially for radar, missile, supersonic aircraft, electronic computers and mobile phones. In the electronic circuit.
In addition, because of the good thermal conductivity of the crucible, various tanks, columns, pipes, valves, etc. in the heater, heat exchanger, concentrator, condenser or reactor are commonly used in the chemical industry. Because of the corrosion resistance of the cockroach, it is not irritating to the human body. In the medical field, it is possible to repair the bone with a seesaw and a bract, to connect the bone with a purlin, and to sew blood vessels and nerves with a sputum. Spraying micro-powder powder into certain tumor lesions can also be used for x-ray examination to observe changes in the condition.
铌 Because of its high melting point and twice the density, it is more widely used in the aerospace and aerospace industries, such as attitude control engine components used as rocket propellers, as blades, combustion chambers and flame stabilizers for aircraft gas turbines. . The use of bismuth as an additive in carbon steel, stainless steel and alloy steel can greatly improve the strength and corrosion resistance of steel.
Tantalum and niobium carbides are also used as superhard cutting tools, which are not only heat and shock resistant, but also have a low coefficient of friction.
(B) tantalum-niobium ore
In the ore-forming geological process, strontium and strontium are disseminated and most of them occur in granite or pegmatite granite. Some are rich in strontium veins relative to the surrounding rock, while others are unevenly dispersed throughout the ore body. The main minerals are tantalum and niobium and tantalum niobium iron ore mine. There is also a tantalum-containing cassiterite, microlite, tantalum and niobium ore manganese, yttrium, tantalum and the like yellow. The ore is brittle and brittle, and the inlay size is generally fine. Tantalum and niobium metal oxide content of tantalum and niobium ores in ore grade, ie high and low ranges, the higher such as Brazil Araxa (Aaxa) niobium mineral processing plant, ore grade of 2.5% to 3.0%, Canada Bo Nike Lake (Bemic Lake) At the mining plant, the original ore grade is 0.13%; the lower one is the Guangdong Pantan (mineral sand) ore dressing plant, the original ore grade is only 0.0083%, and the ore grade of most antimony ore is in a few ten thousandths, such as 0.06% in Fujian Nanping Mine. Jiangxi Yichun Mine is 0.027. The Xinjiang Cocoto Sea Mine is 0.025%, and the Guangxi Limu Mine is 0.02%. The recovery rate of most of the smelting plants is between 40% and 65%.
Second, the theory and practice of bismuth ore dressing
(1) Mineral processing method
1. Determine the principles and basis of the beneficiation method
The principle of the beneficiation method is determined. First, the selectivity of the ore is adopted by the beneficiation method, and second, the economics of the beneficiation method is adopted. In other words, in principle, it is necessary to use a beneficiation method that is both optional and has the greatest economic benefit. There are various mineral processing methods, among which the three most commonly used mineral processing methods are gravity beneficiation, floating ore dressing and electromagnetic beneficiation. Because re-election is generally simpler and the cost is often lower than other beneficiation methods, so when determining the beneficiation method, as long as the re-election of the ore is good, the re-election scheme is always considered first. When the re-election of the ore is poorly selectable, that is, it is difficult to obtain the ideal sorting index by re-election, it is only necessary to consider the other methods.
The basis for determining the ore dressing method is mainly the nature of ore, including the density of various minerals in the ore, the hardness, the size and state of inclusion of useful minerals, the surface physicochemical properties and electromagnetic properties of various minerals, and the complexity of mineral composition. Wait. The experience of mineral processing practice in the same type of mines, the research results of the industry's peers on the ore dressing, can no doubt be borrowed.
2. Determination of mineral processing method
Generally, according to the calculated value of the formula e=(δ2-Δ)/(δ1-Δ), the following table is used to determine the difficulty of re-election of ore.
Table 1 Difficulty of sorting minerals by specific gravity
The density of strontium minerals is usually above 5500kg/m3, while the density of gangue minerals is generally 2700kg/m3. The e-value of minerals sorted by specific gravity is greater than 2.5, so it is easy to sort the antimony ore by re-election method. . The re-election method is the preferred method for determining the bismuth beneficiation method.
For the antimony ore that is difficult to be effectively sorted by gravity ore dressing, such as antimony ore with particularly complex mineral composition, the antimony ore with fine grain size is especially fine, and it can be considered on the basis of gravity beneficiation method. Appropriate use of flotation, electromagnetic selection and water metallurgy methods to supplement.
(2) Beneficiation process
1, broken
In the early crushing process design, the required number of crushing sections was determined according to the maximum bulk of the ore and the coarser final crushed product size, and the crushing equipment was selected according to the scale of the ore dressing plant. Later, the ore dressing workers found that the grinding cost was much higher than the cost of the crushing, and reducing the particle size of the final crushed product was beneficial to improve the grinding effect and reduce the total cost of grinding. Therefore, the crushing and grinding were started when the crushing process was designed. As a whole, considering the optimum grinding mill to determine the particle size of the final crushed product, the crushing process design is developed to reduce the granularity of the final crushed product. Less grinding." In this regard, the former Soviet Union's ore dressing workers have done a lot of work, and the results are shown in the table below.
Yichun antimony ore dressing plant design adopts three-stage open-circuit crushing sulfur process, one section adopts φ900×1200 jaw crusher , the second section adopts φ1750 standard cone crusher , the third section adopts φ2200 short-head cone crusher, and the final crushed product granularity- 25mm is over 95%. Because the mineral inclusions are fine and brittle, it is especially important to grind and grind. According to the research results of the former Soviet mineral processing workers, the Yichun Yan ore concentrator is a medium-sized concentrator (1500t/d), and the suitable final crushed product should have a particle size of less than 10mm. Regardless of whether this conclusion is completely correct, there is no doubt that the existing final crushed product of the Yichun Yankuang Concentrator is too coarse. As a result, the grinding ratio of one section of grinding is as high as 50, which not only makes the total cost of grinding more than high, but also results in poor grinding effect, and the grinding product has coarse grain size and shows muddy.
2, grinding
The grinding process must meet the following conditions:
(1) The needs of the production capacity of the concentrator.
(2) The need to grind the ore to the specified fineness. When the size of the useful mineral is relatively coarse, the primary grinding can grind the ore to the specified fineness, so that the useful mineral is substantially completely dissociated. At this time, the design should adopt a grinding process. When the fineness of the useful mineral is fine, it is difficult to grind the ore to the required fineness in one grinding, and two or more grinding processes must be designed.
(3) The need for stage grinding and stage classification. If the useful mineral has a wide range of inlay size, even if the primary grinding can achieve the required fineness, the useful minerals are substantially dissociated completely, but the coarsely divided useful minerals that are dissociated first are easily ground to excessive pulverization. Recycling. In order to reduce the excessive pulverization of useful minerals and reduce the loss of useful metals, it is conceivable to adopt a stage grinding and stage selection process, that is, a section of grinding first grinds the ore to a certain fineness (thicker), so that the coarse-grained useful mineral takes the lead. Dissociated, and then sorted and recycled. The selected tailings enter the second stage of the grinding machine and are ground to the required fineness, so that the useful minerals are substantially dissociated completely, and then the separation is carried out again.
In the two-stage grinding process, regardless of whether the first-stage grinding machine is closed or not, the second-stage grinding machine must work in a closed circuit, otherwise the grinding machine will not be effectively utilized. At the same time, in the grinding process, as long as the qualified grain content in the ore-feeding mine is greater than 15%, a pre-grading operation should be set. In addition, it is best to promote the application of the two-stage grading process initiated by Professor Hu Ji to improve the production capacity of the grinding machine and the recovery rate of the ore dressing. The design of Yichun Yankuang Concentrator is based on φ2100×30 stage grinding and stage selection process. A section of grinding uses a wet overflow type rod mill to grind the ore to -0.5mm, then close the road with high-frequency fine screen, and 65% to 70% of the sieved product is returned to the rod mill for re-grinding, +0.5mm under the sieve The product enters the -0.5mm sorghum type single spiral classifier and is divided into two grades of FG-15φ1500. The back sand of 0.5-0.2mm is selected as the first section of grinding product in the first stage. Although the strontium concentrate obtained after the selection of a section of grinding products is coarser, its particle size is completely within the range of fine concentrates, and the fractional recovery of 0.5-0.2 mm is almost zero. So it is difficult to say that the rationality of the process is no problem. At that time, the design was based on the test conclusion that “there was a monomer when the ore was broken to 0.4 mmâ€, but “beginning with monomer†was not a quantitative concept, and it was unreasonable to use it as a design basis. After the first section of the tailings, the tailings will enter the second stage of grinding. The second-stage grinding machine adopts φ2100×2200 wet lattice ball mill to grind the ore to -0.2mm, which accounts for more than 85%. However, because the second-stage grinding machine works, the actual grinding size can only reach about 65%, and the design index. A far cry, resulting in a large number of useful minerals failed to separate the monomer, can not meet the requirements of the selection process. At the same time, the qualified grain content of the second-stage grinding machine is as high as 22.7%, and there is no pre-grading operation.
3, graded selection
The basic requirements for beneficiation should be clarified when designing the grading process. First of all, any sorting equipment has a suitable range of particle sizes, which vary in width and width. Therefore, the materials must be graded before being selected to meet the performance of the sorting equipment to meet the production needs. The division of the selected material size is related to its nature and the performance of the equipment. For example, for the ore dressing of tungsten, tin and other ores, it is recovered by gravity ore dressing. The selected materials are usually divided into coarse-grained grade (2~0.5mm) fine-grain grade (0.5-0.074mm) and fine mud (-0.074mm). The three fractions are processed separately. Then, does this division also apply to antimony ore? As mentioned above, the niobium concentrate recovered after the 0.5-0.2mm grade in the grinding product of the Yichun antimony ore is almost all -0.2mm. Concentrate, +0.2mm fractional recovery is almost zero. It is obviously not that the +0.2 mm niobium mineral monomer is not available in the re-election equipment , but because there is no niobium mineral monomer in the +0.2 mm grade material, or the niobium mineral is not actually separated by the monomer. Therefore #, (0.5-0.2mm) is not a qualified material, and it is not necessary to set (0.5-0.2mm). For Yichun antimony ore dressing, all selected materials should be ground to -0.2mm. Secondly, does the -0.2mm qualified material still need to be re-classified? For the non-ferrous metals such as tungsten and tin, on the basis of summarizing the experience of the ore dressing test and production practice, the ore dressing worker believes that the lower limit of the re-election recovery particle size is 0.038mm. And 0.074mm as the dividing line between ore and slime is undoubtedly correct. Then, is the lower limit of re-election recovery of antimony ore also 0.038mm? And look at the table below data.
The ore recovery rate of Yichun antimony ore is only 48%, while the recovery of -0.038mm in the coarse weight grade (0.5-0.2mm) is 44.93%, and in the fine fraction (0.2-0.038mm). The recovery rate of 0.038mm is 46.06%, which is not much lower than 48%. Therefore -0.038mm is clearly not the lower limit of the reclaimed recovery particle size of the antimony ore. The reason why the two are different is because the ore grade of tungsten ore is high (0.3%), and the embedding grain size of tungsten mineral is coarse. Before the ore crushing and grinding 0.038mm, the tungsten mineral has already been completely dissociated and sorted and recovered. There are very few useful minerals in the -0.074mm grain size, and it is naturally difficult to recycle with separate treatment. Therefore, it is not only reasonable but also reasonable to set 0.038mm as the lower limit of the recovery particle size. However, the ore grade of the antimony ore is much lower, and the inlay size of the niobium mineral is much finer. When the ore is crushed to -0.1, the monomer reaches 95%, and not only the niobium mineral in the -0.074 mm fraction. Monomers, which are also in the -0.038mm size range, also have a considerable amount of niobium mineral monomers, which can be recovered by gravity beneficiation without classification. Therefore, 0.038mm is not the lower limit of re-election recovery of antimony ore. This has been proven by the trial and production practices of Yichun Yankuang Mine. The lower limit of the particle size of the re-election recovery of antimony ore is still unknown. So far no one has studied and explored it, but it is certainly much lower than 0.038mm, so the ore and slime are not just a granularity. concept. From the point of view of granularity, it may not be wrong to count -0.074mm as fine mud, but if you consider the lower limit of the recovery granularity of re-election, this division may not be appropriate. If -0.2mm is to be re-classified, it is actually a de-sludge problem. The lower limit of the re-election recovery of tungsten ore is 0.038mm. It is correct to separate the 0.074mm fraction as a fine mud. The lower limit of the particle size of the re-election recovery of antimony ore is not 0.038 mm, and it is obviously unreasonable to separate the -0.038 mm particle size as a separate treatment of the fine mud. In fact, the -0.038mm fraction is treated separately and the recovery rate will drop significantly. For example, in the grinding mill workshop - 0.038mm particle size recovery rate of 45% and -0.038mm after separation and treatment in fine mud alone, the recovery rate is less than 10%. This is because there is a special phenomenon in the process of gravity beneficiation - separation and stratification, fine-grained heavy minerals can be drilled through the gap of coarse ore particles to reach the bottom of the bed, thereby moving forward under the entrainment of coarse and heavy ore particles. Until it is discharged from the concentrate end. The -0.038mm is separated and treated separately, and the separation and stratification no longer exist. It is difficult for fine-grained heavy minerals to settle to the bottom of the bed, and the entrainment of the coarse and heavy ore particles is lost. The fine-grained heavy minerals are no longer possible. From the feeding end along the bed surface to the concentrate end, it will be washed away by the horizontal flow in the middle, so it is difficult to recycle. Therefore, the classification of minerals is important, but it must be reasonable, and the classification is too fine and harmful. Considering that the lower limit of re-election recovery of antimony ore is still unclear, the ore deposit is difficult to define, and the finer the classification, the more difficult it is. Instead of adding too much input for de-sludge, it is better not to remove the mud.
3. Reforming the direction of the ore dressing process in Yichun
The production research test from 1978 to 1981 and the technical transformation from 1982 to 1984 solved the problem of rough selection equipment in the main process of the beneficiation plant (replacement of the combined chute with spiral chute) and demineralization of the original ore (using the vibrating feed screen washing machine) The problem that the coarse crushing equipment does not match the original ore grade (replaces the φ600×900 jaw crusher with φ900×1200 jaw crusher), which realizes smooth flow and normal production. However, the problem that the final particle size of the crushed ore product is too coarse and the grain size of the second-stage grinding product is too coarse and the classification process is unreasonable still exists, and improvement is urgently needed.
(1) The particle size of the final crushed product is reduced from -25mm to -10mm. With the existing three-stage open-circuit crushing process, it is impossible to reduce the final crushed product size from -25mm to -10mm. Ways to reduce the granularity of the final mined product are:
1. Replace the crushing equipment and replace it with the foreign advanced impact crusher (there is information, the impact crusher produced abroad can crush the ore to -5mm in one crush).
2. Change the three-stage open-circuit crushing process to a three-stage closed-circuit process.
All of the above methods must undergo major technological transformations, which will inevitably affect normal production, and enterprises may be unbearable. Moreover, the opening and closing of the road will seriously limit the production capacity of the existing crushing equipment, and it is not desirable to meet the production needs.
3. Use the wet rod mill as the fourth-stage crusher, and change from closed-circuit work to open-circuit work, allowing the grinding particle size to be relaxed to 2mm or 3mm. This is possible. Because the original design is a stage grinding process and a stage selection process, in fact, the 0.5-0.2mm grain grade cerium mineral in the first stage grinding product has not been separated by the monomer, and cannot meet the requirements of the sorting process. In fact, there is no It plays the role of stage grinding and stage classification.
(2) The existing two-stage grinding machine is changed from open work to closed work. In order to solve the problem that the second-stage grinding is seriously under-grinded and the grain size of the grinding product is too coarse to meet the requirements of the beneficiation process, it is necessary to open the second stage of the open work. The mining machine was changed to a closed circuit. The original design did not use a closed-circuit process, which was worried that the lithium mica would be difficult to grind. For this purpose, Huji's two-stage grading process can be applied, and pre-screening and inspection sieving are separately provided, and a tee is installed at the product discharge of the sifted screen. The lithium mica content in the product on the screen is often checked during the production process. Under normal conditions, the product on the sieve enters the mill through the three-way branch of the tee and is ground again. When the lithium mica in the product on the sieve accumulates to a certain extent, immediately close the No. 1 branch pipe, open the No. 2 branch pipe, and let the product on the sieve be separately discharged into the lithium mica concentrate product through the No. 2 branch pipe. This will prevent a vicious circle caused by the difficulty of grinding the lithium mica.
(3) Reforming the selection process
Since the selection of 0.5-0.2mm grain-level materials is actually an invalidation, this sorting section should be cancelled to save the equipment, manpower and material resources occupied by this part of the material during the sorting process. All selected materials should be ground to -0.2mm.
Also, since the lower limit of the particle size of the re-election recovery of the antimony ore is not 0.038 mm, the -0.038 mm fraction of the selected material should not be separated and treated as a fine mud alone. Plus the -0.2mm level is not too wide, and the ore and slime of the antimony ore are difficult to define. At the same time, if the particle size is already very fine, there is no interference with the "fine mud", so the fine material (0.2 -0.038mm) can be no longer graded.
Finally, considering that the -0.038mm particle size recovery rate in the selected materials has reached 45%, it is still low, indicating that the recovery by gravity ore dressing method is not complete, and the gravity beneficiation method is not as good as flotation in dealing with fine-grained materials. Therefore, in order to further improve the recovery rate, -0.038 mm in the re-selected tailings can be separated for flotation, and the niobium minerals can be further sorted and recovered.