Tungsten ore enrichment cycle. Technology of enrichment of wolframite ores. General information about methods of beneficiation of tungsten ores

Vladivostok

annotation

This paper discusses technologies for the enrichment of scheelite and wolframite.

Enrichment technology tungsten ores includes: preliminary concentration, enrichment of crushed products of preliminary concentration to obtain collective (rough) concentrates and their finishing.

Keywords

Scheelite ore, wolframite ore, heavy-medium separation, jigging, gravity method, electromagnetic separation, flotation.

1. Introduction 4

2. Pre-concentration 5

3. Technology of enrichment of wolframite ores 6

4. Technology of enrichment of Scheelite ores 9

5. Conclusion 12

References 13

Introduction

Tungsten is a silver-white metal with high hardness and a boiling point of about 5500°C.

Russian Federation has large explored reserves. Its tungsten ore potential is estimated at 2.6 million tons of tungsten trioxide, of which proven reserves amount to 1.7 million tons, or 35% of those in the world.

Developed deposits in the Primorsky Territory: Vostok-2, OJSC Primorsky GOK (1.503%); Lermontovskoye, OJSC Lermontovskaya GRK (2.462%).

Main tungsten minerals are scheelite, hübnerite and wolframite. Depending on the type of minerals, ores can be divided into two types; scheelite and wolframite (huebnerite).

When processing tungsten-containing ores, gravitational, flotation, magnetic, as well as electrostatic, hydrometallurgical and other methods are used.

Pre-concentration.

The cheapest and at the same time highly productive methods of preconcentration are gravitational ones, such as heavy-medium separation and jigging.

Heavy medium separation allows you to stabilize the quality of the feed entering the main processing cycles, to isolate not only the waste product, but also to separate the ore into rich coarsely disseminated and poor finely disseminated ore, which often require fundamental different schemes processing, since they differ markedly in material composition. The process is characterized by the highest density separation accuracy compared to other gravitational methods, which allows for high recovery of the valuable component with minimal concentrate yield. When enriching ore in heavy suspensions, a difference in the densities of the separated pieces of 0.1 g/m3 is sufficient. This method can be successfully used for coarsely disseminated wolframite and scheelite-quartz ores. The results of studies on the enrichment of tungsten ores from the Pun-les-Vignes (France) and Borralha (Portugal) deposits under industrial conditions showed that the results obtained using enrichment in heavy suspensions are significantly better than when enriching only on jig machines - into the heavy fraction recovery was more than 93% of the ore.

Jigging compared to heavy-medium enrichment requires less capital costs, allows you to enrich material in a wide range of densities and sizes. Coarse jigging has become widespread in the beneficiation of coarse and medium disseminated ores that do not require fine grinding. The use of jigging is preferable when enriching carbonate and silicate ores of skarn and vein deposits, while the value of the ore contrast index in terms of gravitational composition should exceed one.

Technology of enrichment of wolframite ores

High specific gravity tungsten minerals and the coarse-grained structure of wolframite ores makes it possible to widely use gravitational processes in their enrichment. To get high technological indicators It is necessary in a gravitational scheme to combine devices with different separation characteristics, in which each previous operation in relation to the subsequent one is, as it were, preparatory, improving the enrichment of the material. Schematic diagram enrichment of wolframite ores is shown in Fig. 1.

Jigging is used starting from the size at which tailings can be recovered. This operation is also used to isolate coarse tungsten concentrates with subsequent regrinding and enrichment of jigging tails. The basis for choosing the jigging scheme and the size of the enriched material is the data obtained by separating the material by density with a particle size of 25 mm. If the ores are finely disseminated and preliminary studies have shown that large-piece enrichment and jigging are unacceptable for them, then the ore is enriched in thin suspension-carrying flows, which include enrichment on screw separators, jet chutes, cone separators, sluices, and concentration tables. With stage-by-stage grinding and stage-by-stage enrichment of ore, the extraction of wolframite into rough concentrates is more complete. Rough wolframite gravity concentrates are brought to condition according to developed schemes using wet and dry enrichment methods.

Rich wolframite concentrates are enriched by electromagnetic separation, and the electromagnetic fraction can be contaminated with ferrous zinc blende, bismuth minerals and partially arsenic (arsenopyrite, scorodite). To remove them, magnetizing roasting is used, which enhances the magnetic susceptibility of iron sulfides, and at the same time, sulfur and arsenic, which are harmful to tungsten concentrates, are removed in the form of gaseous oxides. Wolframite (Hübnerite) is further extracted from sludge by flotation using fatty acid collectors and the addition of neutral oils. Rough gravity concentrates are relatively easily brought to standard using electrical methods enrichment. Flotation and flotation gravity are carried out with the supply of xanthate and a foaming agent in a slightly alkaline or slightly acidic environment. If the concentrates are contaminated with quartz and light minerals, then after flotation they are cleaned on concentration tables.

Related information.

Tungsten is the most refractory metal, melting point 3380°C. And this determines its scope. It is also impossible to build electronics without tungsten; even the filament in a light bulb is tungsten.

And, naturally, the properties of the metal also determine the difficulties in obtaining it...

First, you need to find ore. These are just two minerals - scheelite (calcium tungstate CaWO 4) and wolframite (iron and manganese tungstate - FeWO 4 or MnWO 4). The latter has been known since the 16th century under the name "wolf's foam" - "Spuma lupi" in Latin, or "Wolf Rahm" in German. This mineral accompanies tin ores and interferes with the smelting of tin, turning it into slag. Therefore, it is possible to find it already in antiquity. Rich tungsten ores usually contain 0.2 - 2% tungsten. Tungsten was actually discovered in 1781.

However, this is the easiest thing to find in tungsten mining.
Next, the ore needs to be enriched. There are a bunch of methods and they are all quite complex. First of all, of course. Then - magnetic separation (if we have wolframite with iron tungstate). Next is gravitational separation, because the metal is very heavy and the ore can be washed, much like when mining gold. Nowadays they still use electrostatic separation, but it is unlikely that the method will be useful to the endangered person.

So, we have separated the ore from the gangue. If we have scheelite (CaWO 4), then we can skip the next step, but if we have wolframite, then we need to turn it into scheelite. To do this, tungsten is extracted soda solution under pressure and at elevated temperature (the process takes place in an autoclave), followed by neutralization and precipitation in the form of artificial scheelite, i.e. calcium tungstate.
It is also possible to sinter wolframite with an excess of soda, then we obtain tungstate not of calcium, but of sodium, which for our purposes is not so significant (4FeWO 4 + 4Na 2 CO 3 + O 2 = 4Na 2 WO 4 + 2Fe 2 O 3 + 4CO 2).

The next two stages are leaching with water CaWO 4 -> H 2 WO 4 and decomposition with hot acid.
You can take different acids - hydrochloric (Na 2 WO 4 + 2HCl = H 2 WO 4 + 2NaCl) or nitric.
As a result, tungsten acid is isolated. The latter is calcined or dissolved in an aqueous solution of NH 3, from which paratungstate is crystallized by evaporation.
As a result, it is possible to obtain the main raw material for the production of tungsten - WO 3 trioxide with good purity.

Of course, there is also a method for producing WO 3 using chlorides, when tungsten concentrate at elevated temperatures it is treated with chlorine, but this method will not be simple for the trapped.

Tungsten oxides can be used in metallurgy as an alloying additive.

So, we have tungsten trioxide and there is only one step left - reduction to metal.
There are two methods here - reduction with hydrogen and reduction with carbon. In the second case, the coal and the impurities it always contains react with tungsten, forming carbides and other compounds. Therefore, tungsten comes out “dirty”, brittle, and for electronics it is pure that is very desirable, because having only 0.1% iron, tungsten becomes brittle and it is impossible to draw the thinnest wire for incandescent filaments from it.
The technical process with coal has another drawback - high temperature: 1300 - 1400°C.

However, production with hydrogen reduction is also not a gift.
The reduction process takes place in special tube furnaces, heated in such a way that as it moves through the tube, the “boat” of WO3 passes through several temperature zones. A stream of dry hydrogen comes towards it. Recovery occurs in both “cold” (450...600°C) and “hot” (750...1100°C) zones; in “cold” ones – to the lower oxide WO 2, then – to the elemental metal. Depending on the temperature and duration of the reaction in the “hot” zone, the purity and grain size of the powdered tungsten released on the walls of the “boat” change.

So, we have obtained pure tungsten metal in the form of a tiny powder.
But this is not yet an ingot of metal from which something can be made. The metal is produced by powder metallurgy. That is, it is first pressed, sintered in a hydrogen atmosphere at a temperature of 1200-1300 °C, then passed through it electricity. The metal is heated to 3000 °C, and sintering occurs into a monolithic material.

However, we rather need not ingots or even rods, but thin tungsten wire.
As you yourself understand, here again everything is not so simple.
Wire drawing is carried out at a temperature of 1000°C at the beginning of the process and 400-600°C at the end. In this case, not only the wire, but also the die is heated. Heating is carried out by a gas burner flame or an electric heater.
In this case, after drawing, the tungsten wire is coated with graphite lubricant. The surface of the wire must be cleaned. Cleaning is carried out using annealing, chemical or electrolytic etching, and electrolytic polishing.

As you can see, the task of producing a simple tungsten filament is not as simple as it seems. And only the basic methods are described here; there are probably a lot of pitfalls there.
And, of course, even now tungsten is not a cheap metal. Now one kilogram of tungsten costs more than $50, the same molybdenum is almost two times cheaper.

Actually, there are several uses for tungsten.
Of course, the main ones are radio and electrical engineering, where tungsten wire goes.

The next one is the production of alloy steels, which are distinguished by their particular hardness, elasticity and strength. Added together with chromium to iron, it produces so-called high-speed steels, which retain their hardness and sharpness even when heated. They are used to make cutters, drills, milling cutters, as well as other cutting and drilling tools (in general, drilling tools contain a lot of tungsten).
Tungsten-rhenium alloys are interesting - they are used to make high-temperature thermocouples that operate at temperatures above 2000°C, although only in an inert environment.

Well, and one more thing interesting application- These are tungsten welding electrodes for electric welding. Such electrodes are non-consumable and it is necessary to supply additional metal wire to the welding site to provide a weld pool. Tungsten electrodes are used in argon arc welding - for welding non-ferrous metals such as molybdenum, titanium, nickel, as well as high-alloy steels.

As you can see, tungsten production is not for ancient times.
And why is tungsten there?
Tungsten can only be obtained with the construction of electrical engineering - with the help of electrical engineering and for electrical engineering.
No electricity means no tungsten, but you don’t need it either.

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State budgetary professional

educational institution of the Republic of Karelia

"Kostomuksha Polytechnic College"

Deputy Director of OD ___________________ Kubar T.S.

"_____"_________________________________2019

GRADUATE QUALIFYING WORK

Subject: "Maintaining the main method of beneficiation of tungsten ores and applying auxiliary processes dehydration in the technological scheme of Primorsky GOK"

Group student: Kuzich S.E.

4th year, group OPI-15 (41C)

Specialty 02/21/18

"Beneficiation of mineral resources"

Head of the research and development work: Volkovich O.V.

teacher special disciplines

Kostomuksha

2019

Introduction………………………………………………………………………………...…3

1. Technological part………………………………………………………6

1.1 general characteristics tungsten ores………………………………….6

1.2 Economic assessment of tungsten ores……………………………………10

1. Technological scheme for beneficiation of tungsten ores using the example of Primorsky Mining and Processing Plant………………………………………………………..……11

2. Dehydration of enrichment products…………………………………......17

2.1. The essence of dehydration processes…………………………………..….17

2.2. Centrifugation…………………………………………………..…….24

3. Organization of safe working conditions…………………………………….30

3.1. Requirements for creating safe working conditions in the workplace…………………………………………………………..…...30

3.2. Requirements for maintaining safety in the workplace…….…..32

3.3. Safety requirements for enterprise employees…………32

Conclusion………………………………………………………………………………….…..…..34

List of sources and literature used……………………....…...36

Introduction

Mineral beneficiation - This is an industry that processes solid minerals with the intention of obtaining concentrates, i.e. products whose quality is higher than the quality of the original raw materials and meets the requirements for their further use in the national economy.Minerals are the basis National economy, and there is not a single industry where minerals or their processed products are not used.

One of these minerals is tungsten, a metal with unique properties. It has the highest boiling and melting points among metals, while having the lowest coefficient of thermal expansion. In addition, it is one of the hardest, heaviest, most stable and dense metals: the density of tungsten is comparable to the density of gold and uranium and 1.7 times higher than that of lead.The main tungsten minerals are scheelite, hübnerite and wolframite. Based on the type of minerals, ores can be classified into two types; scheelite and wolframite. When processing tungsten-containing ores, gravitational, flotation, magnetic, and also electrostatic,hydrometallurgical and other methods.

IN last years Metal-ceramic hard alloys made on the basis of tungsten carbide are widely used. Such alloys are used as cutters, for the manufacture of drill bits, dies for cold wire drawing, dies, springs, parts of pneumatic tools, valves of internal combustion engines, heat-resistant parts of mechanisms operating at high temperatures. Surfacing hard alloys (stellites), consisting of tungsten (3-15%), chromium (25-35%) and cobalt (45-65%) with a small amount of carbon, are used for coating quickly wearing parts of mechanisms (turbine blades, excavator equipment and etc.). Tungsten alloys with nickel and copper are used in the manufacture of protective screens against gamma rays in medicine.

Metal tungsten is used in electrical engineering, radio engineering, X-ray engineering: for the manufacture of incandescent filaments in electric lamps, high-temperature heaters electric ovens, anticathodes and cathodes of X-ray tubes, electric vacuum equipment and much more. Tungsten compounds are used as dyes, to impart fire and water resistance to fabrics, in chemistry - as a sensitive reagent for alkaloids, nicotine, protein, and as a catalyst in the production of high-octane gasoline.

Tungsten is also widely used in the production of military and space equipment (armor plates, tank turrets, rifle and gun barrels, rocket cores, etc.).

The structure of tungsten consumption in the world is constantly changing. It is being replaced by other materials in some industries, but new areas of its application are emerging. Thus, in the first half of the 20th century, up to 90% of tungsten was spent on alloying steels. Currently, the industry is dominated by the production of tungsten carbide, and the use of tungsten metal is becoming increasingly important. IN Lately New opportunities are opening up for the use of tungsten as an environmentally friendly material. Tungsten can replace lead in the production of various ammunition, and can also be used in the manufacture of sports equipment, in particular golf clubs and balls. Developments in these areas are being carried out in the USA. In the future, tungsten should replace depleted uranium in the production of large-caliber ammunition. In the 1970s, when tungsten prices were around $170. for 1% WO content 3 per 1 ton of product, the USA and then some NATO countries replaced tungsten with depleted uranium in heavy ammunition, which, at the same technical specifications was significantly cheaper.

Tungsten like chemical element belongs to the group of heavy metals and, from an environmental point of view, is classified as moderately toxic (Class II-III). The current source of tungsten pollution is environment are the processes of exploration, mining and processing (concentration and metallurgy) of tungsten-containing mineral raw materials. As a result of processing, such sources are unused solid waste, wastewater, and dusty tungsten-containing fine particles. Solid waste in the form of dumps and various tailings are formed during the enrichment of tungsten ores. Wastewater processing plants represented by tailings discharges, which are used as recycled water in grinding and flotation processes.

Graduation goal qualifying work : justify technological scheme enrichment of tungsten ores using the example of Primorsky GOK and the essence of dehydration processes in this technological scheme.

The chemical element is tungsten.

Before describing the production of tungsten, it is necessary to take a short excursion into history. The name of this metal is translated from German as “wolf’s cream”; the origin of the term goes back to the late Middle Ages.

When obtaining tin from various ores, it was noticed that in some cases it was lost, turning into foamy slag, “like a wolf devouring its prey.”

The metaphor caught on, giving the name to the later received metal; it is currently used in many languages ​​of the world. But in English, French and some other languages, tungsten is called differently, from the metaphor “heavy stone” (tungsten in Swedish). The Swedish origin of the word is associated with the experiments of the famous Swedish chemist Scheele, who first obtained tungsten oxide from the ore later named after him (scheelite).

Swedish chemist Scheele, who discovered tungsten.

Industrial production of tungsten metal can be divided into 3 stages:

• ore beneficiation and production of tungsten anhydrite;
• reduction to powder metal;
• receiving monolithic metal.

Ore beneficiation

Tungsten does not occur in a free state in nature; it is present only in various compounds.

• wolframites
• scheelites

These ores often contain small quantities of other substances (gold, silver, tin, mercury, etc.), despite the very low content of additional minerals, sometimes their associated extraction during enrichment is economically feasible.

1. Beneficiation begins with crushing and grinding the rock. The material is then sent for further processing, the methods of which depend on the type of ore. Enrichment of wolframite ores is usually carried out using the gravitational method, the essence of which is to use the combined forces of gravity and centrifugal force; minerals are separated according to chemical and physical properties - density, particle size, wettability. This way, the waste rock is separated, and the concentrate is brought to the required purity using magnetic separation. The wolframite content in the resulting concentrate ranges from 52 to 85%.
2. Scheelite, unlike wolframite, is not magnetic mineral, therefore magnetic separation is not applied to it. For scheelite ores, the enrichment algorithm is different. The main method is flotation (the process of separating particles in an aqueous suspension) followed by the use of electrostatic separation. The concentration of scheelite at the outlet can be up to 90%. Ores can also be complex, containing wolframites and scheelites at the same time. To enrich them, methods combining gravitational and flotation schemes are used.
   
   If further purification of the concentrate to established standards is necessary, various procedures are used depending on the type of impurities. To reduce phosphorus impurities, scheelite concentrates are processed in the cold hydrochloric acid, at the same time calcite and dolomite are removed. To remove copper, arsenic, and bismuth, roasting followed by treatment with acids is used. There are other cleaning methods.

Several different methods are used to convert tungsten from a concentrate into a soluble compound.

1. For example, the concentrate is sintered with an excess of soda, thus obtaining sodium wolframite.
2. Another method can be used - leaching: tungsten is extracted with a soda solution under pressure at high temperature, followed by neutralization and precipitation.
3. Another method is to treat the concentrate with chlorine gas. This process produces tungsten chloride, which is then separated from the chlorides of other metals by sublimation. The resulting product can be converted into tungsten oxide or processed directly into elemental metal.

The main result of various enrichment methods is the production of tungsten trioxide. Further, it is he who goes into the production of metal tungsten. Tungsten carbide is also obtained from it, which is the main component of many hard alloys. There is another product of direct processing of tungsten ore concentrates - ferrotungsten. It is usually smelted for the needs of ferrous metallurgy.

Tungsten Recovery

The resulting tungsten trioxide (tungsten anhydrite) must be reduced to the metal state in the next step. Reduction is most often carried out using the widely used hydrogen method. A moving container (boat) with tungsten trioxide is fed into the furnace, the temperature rises as it moves, hydrogen is supplied towards it. As the metal is restored, the bulk density of the material increases, the container loading volume decreases by more than half, so in practice, a run in 2 stages is used, through different types ovens.

1. At the first stage, dioxide is formed from tungsten trioxide, at the second, pure tungsten powder is obtained from the dioxide.
2. Then the powder is sifted through a mesh, large particles are additionally ground to obtain a powder with given size grains

Carbon is sometimes used to reduce tungsten. This method simplifies production somewhat, but requires higher temperatures. In addition, coal and the impurities it contains react with tungsten, forming various compounds that lead to contamination of the metal. There are a number of other methods used in production around the world, but in terms of all parameters, hydrogen reduction has the highest applicability.

Obtaining monolithic metal

If the first two stages industrial production Since tungsten is well known to metallurgists and has been used for a very long time, obtaining a monolith from powder required the development of a special technology. Most metals are obtained by simple melting and then cast into molds; with tungsten, due to its main property - refractoriness - such a procedure is impossible. The method of producing compact tungsten from powder, proposed at the beginning of the 20th century by the American Coolidge, is still used with various variations in our time. The essence of the method is that the powder turns into a monolithic metal under the influence of electric current. Instead of conventional smelting, several steps must be taken to obtain tungsten metal. At the first of them, the powder is pressed into special bars. Then these posts are subjected to a sintering procedure, and this is done in two stages:

1. 1. First, at temperatures up to 1300ºC, the rod is pre-sintered to increase its strength. The procedure is carried out in a special sealed oven with a continuous supply of hydrogen. Hydrogen is used for additional reduction; it penetrates into the porous structure of the material, and with additional exposure to high temperature, a purely metallic contact is created between the crystals of the sintered rod. After this stage, the headstock is significantly strengthened, losing up to 5% in size.
   2. Then proceed to the main stage - welding. This process is carried out at temperatures up to 3 thousandºC. The post is secured with clamping contacts, and an electric current is passed through it. Hydrogen is also used at this stage - it is needed to prevent oxidation. The current used is very high; for bars with a cross-section of 10x10 mm, a current of about 2500 A is required, and for a cross-section of 25x25 mm - about 9000 A. The voltage used is relatively small, from 10 to 20 V. For each batch of monolithic metal, a test bar is first welded, it is used to calibrate the welding mode. The duration of welding depends on the size of the post and usually ranges from 15 minutes to an hour. This stage, like the first, also leads to a reduction in the size of the stack.

The density and grain size of the resulting metal depend on the initial grain size of the rod and on maximum temperature welding The loss of dimensions after two stages of sintering is up to 18% along the length. The final density is 17–18.5 g/cm².

To obtain highly purified tungsten, various additives are used that evaporate during the welding process, for example, silicon oxides and alkali metals. As they heat up, these additives evaporate, taking other impurities with them. This process promotes additional cleaning. When using the correct temperature regime and the absence of traces of moisture in a hydrogen atmosphere during sintering, with the help of such additives the degree of tungsten purification can be increased to 99.995%.

Production of tungsten products

Obtained from the original ore after the three production stages described, monolithic tungsten has a unique set of properties. In addition to refractoriness, it is characterized by very high stability of geometric dimensions, preservation of strength at high temperatures and lack of internal tension. Tungsten also has good ductility and malleability. Further production most often involves drawing out wire. These are technologically relatively simple processes.

1. The blanks enter a rotary forging machine, where the material is compressed.
2. Then the drawing method produces wire of various diameters (drawing is drawing a rod using special equipment through tapering holes). This way you can obtain the thinnest tungsten wire with a total degree of deformation of 99.9995%, while its strength can reach 600 kg/mm².

Tungsten began to be used for filaments electric lamps even before the development of a method for producing malleable tungsten. The Russian scientist Lodygin, who had previously patented the principle of using a filament for a lamp, in the 1890s proposed using tungsten wire twisted into a spiral as such a filament. How did you get tungsten for such wires? First, a mixture of tungsten powder with some kind of plasticizer (for example, paraffin) was prepared, then a thin thread was pressed out of this mixture through a hole of a given diameter, dried and calcined in hydrogen. The result was a rather fragile wire, straight sections of which were attached to the electrodes of the lamp. There were attempts to obtain compact metal using other methods, however, in all cases, the fragility of the threads remained critically high. After the work of Coolidge and Fink, the production of tungsten wire gained a solid technological basis, and the industrial use of tungsten began to grow rapidly.

An incandescent lamp invented by the Russian scientist Lodygin.

World tungsten market

Tungsten production volumes are about 50 thousand tons per year. The leader in production, as well as in consumption, is China; this country produces approximately 41 thousand tons per year (Russia, for comparison, produces 3.5 thousand tons). An important factor currently is the processing of secondary raw materials, usually scrap tungsten carbide, shavings, sawdust and tungsten powder residues; such processing provides about 30% of global tungsten consumption.

Filaments from burnt-out incandescent lamps are practically not recycled.

The global tungsten market has recently shown a decline in demand for tungsten filaments. This is due to the development of alternative technologies in the field of lighting - fluorescent and LED bulbs aggressively replace conventional incandescent lamps both in everyday life and in industry. According to experts, the use of tungsten in this sector will decrease by 5% per year in the coming years. The demand for tungsten as a whole is not decreasing; the decline in applicability in one sector is compensated by growth in others, including innovative industries.