TUNGSTEN MINING

TUNGSTEN :

Tungsten occurs in the normal state hardly in the type of chemical compounds with supplementary elements. Even though more than 20 tungsten bearing minerals are identified, only 2 of them are important for industrial utilize specifically wolframite and scheelite. Pure scheelite contains blue-white fluorescence in ultraviolet luminosity, a belonging which is utilized in prospecting. Wolframite is a universal word for iron and manganese tungstates where the iron/manganese proportion can fluctuate. A mineral with more than 80% FeWO4 is named Ferberite and a mineral with further than 80% MnWO4 is named Hübnerite.

All tungsten dumps are of cooled magma or hydrothermal beginning. During cooling of the molten rock, degree of difference over crystallization happens, and scheelite and wolframite are over and over again establish in veins where the volcanic emission has infiltrate cracks in the earth's outer layer. Most of the tungsten deposits are in younger peak belts, i.e. the Alps, the Himalayas and the circum-Pacific belt. Over the previous few existences, sources of contribute have distorted spectacularly. In 1986, the USSR was the world’s biggest consumer but, by 1992, the rehabilitated CIS was exporting tungsten and by 1996 was the world’s 2nd major trader.

Tungsten is generally mined underground. Scheelite and/or wolframite are frequently positioned in rather narrow veins which are faintly disposed and often widen with the intensity. Open pit mines subsist but are exceptional. The ore is first compacted and milled to unshackle the tungsten mineral crystals. Scheelite ore can be concerted by gravimetric techniques, often pooled with lather flotation, whilst wolframite ore can be concerted by solemnity, sometimes in amalgamation with magnetic disjointing.

HOW IS TUNGSTEN OBTAINED?

Tungsten is mostly obtained from the minerals scheelite and wolframite which also includes Ferberite and huebnerite in the list. Tungsten is not refined by smelting or through any other method through which other metals are refined since it has the highest melting point above any other metal. Therefore, tungsten is extracted chemically from the crushed ore in a series of chemical reactions, titrations, washings, and filterings. Tungsten mining countries are China, Russia, Portugal, Austria and Bolivia. China is known to provide about 75% of the world's tungsten supply. The mining methods used for tungsten depend on the physical and chemical properties of the mineral, the grade and depth of the ore and the physical form in which it occurs. The common extraction methods are surface mining and underground mining.

MINING AND PROCESSING :

The surface mining methods are used when the tungsten minerals are found in the earth's surface where underground digging is not required. The areas where surface mining is done is referred to as quarries. These quarries are expanded until no more useful minerals are extracted. This method is most certainly carried in the regions of Australia and Canada.
The method of underground mining is done by slashing out the ore which is generally cost-effective. The miners will drill directly into the tungsten ore deposit to carve out large chunks of the ore. Otherwise the room-and-pillar mining method involves carving out rooms of the ore, while leaving across many pillars to support the roof. This process requires a series of rooms and pillars to be developed.


Despite, having a large amount of the ore mined, it is astonishing to know that most tungsten minerals contain less than 1.5 percentage of useful tungsten. The extraction of useful minerals from the rock requires crushing machines breaking down the ore into very smaller chunks, after which those chunks are sent to an ore-dressing plant following which our piece of favourite jewellery is made ready. Deep down from the earth to our fingers, the tungsten mining process is very much labour intensive and tedious.

EXTRACTION AND REFINING :

Tungsten ores occur frequently in association with sulfides and arsenides which can be removed by roasting in air for two to four hours at 800? C. An intermediate compound, ammonium paratungstate (APT) must be firstly produced to obtain the pure metal. Regarding this, the ores undergo decomposition through acid leaching or by adding concentrated sodium hydroxide solution. In the second stage, the ground ore is kept for about 11/2 to 4 hours in a solution of 10-18 percent sodium carbonate at temperatures of 190?C to 230?C under a pressure of 14.1-24.6 kilograms per square centimetre. Before the removal of gangue or unwanted waste by filtration process, the acidity is adjusted to pH 9-9.5 and aluminum and manganese sulfates are added at 70?C-80?C and stirred for an hour completely. This helps in eliminating phosphorus and arsenic and thus reduces silica to a level of 0.03-0.06 percent. Sodium sulfide is added at 80?C-85?C at a pH of 10 to remove the presence of molybdenum. Holding for an hour and acidifying the solution to pH 2.5-3 and then stirring it for seven to nine hours, molybdenum sulfide gets precipitated. The sodium tungstate solution obtained can be purified by precipitation and filtration after which it is converted to ammonium tungstate solution. This purification is done by a liquid ion-exchange process with the help of an organic extractant which consists of alamine-336, decanol, kerosene in definite proportions. The tungstate ions transfer from the aqueous phase to the organic phase during the countercurrent flow of the extractant through the solution. The tungsten present in it is later on stripped from the extractant into a solution containing ammonium tungstate. For a highly pure solution, the Ammonium Paratungstate formed as a result is sent to an evaporator for crystallization.


In the process of acid-leaching, the scheelite ore concentrate gets decomposed by hydrochloric acid in the presence of sodium nitrate which acts as an oxidizing agent. This charge is alarmed by steam spraying and is maintained at 70?C for 12 hours. The outcoming slurry contains tungsten in the form of a solid tungstic acid and is diluted and allowed to settle. The tungstic acid is then dissolved in aqueous ammonia at 60?C by stirring for continuous two hours. Calcium from the obtained solution is precipitated as calcium oxalate, while phosphorus and arsenic are removed by adding magnesium oxide, which gives rise to insoluble phosphates and arsenates of ammonium and magnesium. Silica, iron and other impurities that form colloidal hydroxides are removed by adding a small amount of activated carbon. The solution is finally purified through pressure filters and evaporated to obtain APT crystals.

Production of Tungsten powder :

When the ammonium paratungstate undergoes decomposition to tungsten oxides, various colours of the oxides are displayed according to the composition: yellow colour is seen in trioxide, whereas the dioxide is in brown, and the oxide is purple-blue. APT is normally decomposed to the intermediate oxide in a rotary furnace to maintain a reduced atmosphere under a stream of hydrogen, because of which the ammonia in the crystals get partially decomposed into nitrogen and hydrogen. This is the process carried for producing tungsten industrially. The rotary furnace is divided by partitions into three zones maintained, respectively, at 850?C, 875?C, and 900?C. The furnace is then tilted slightly and rotated to provide a continuous flow of powder through the central holes of the partitions.

production of tungsten
 

The blue oxide is reduced to metallic tungsten powder by hydrogen in stationary furnaces at temperatures ranging from 550?C to 850?C.

WO3(g)+ 3H2(g) -----> W(s)+ 3H2O(g)

Even though the powder is generally contaminated with tungsten carbide and some mineral elements contained in the carbon, the ammonium paratungstate can also be reduced by carbon. When APT and carbon are mixed and reacted at 650?C850?C, the product formed is a blue oxide. When heated in the range of 900?C1,050? C, the brown oxide is formed. A temperature higher than 1,050? C is required, for complete reduction to a pure tungsten metal of 95% purity.

 

TOP TUNGSTEN PRODUCING COUNTRIES :


1. China: China is the world's leading tungsten producer, accounting for over 80% of global output. In 2019, China produced an estimated 73,000 metric tons of tungsten, up from 70,000 metric tons in 2018. The major tungsten producing areas in China are Hunan, Jiangxi, Guangdong, Fujian, and Guangxi.

2. Russia: Russia is the second largest producer of tungsten in the world, with an estimated output of 5,900 metric tons in 2019. The major tungsten producing regions in Russia are Chelyabinsk, Altai, and Khabarovsk.

3. Vietnam: Vietnam is the third largest producer of tungsten in the world, with an estimated output of 4,400 metric tons in 2019. The major tungsten producing regions in Vietnam are Quang Ninh and Ha Tinh.

4. Canada: Canada is the fourth largest producer of tungsten in the world, with an estimated output of 3,800 metric tons in 2019. The major tungsten producing region in Canada is Ontario.

5. South Korea: South Korea is the fifth largest producer of tungsten in the world, with an estimated output of 2,400 metric tons in 2019. The major tungsten producing region in South Korea


production of tungsten

 

 

ANNUAL TUNGSTEN USAGE :

Tungsten is a metallic element that is used extensively in industry and commerce. It is used in a variety of applications, from electrical and electronics equipment to the production of industrial tools and materials. The annual usage of tungsten is estimated to be around 10,000 tonnes. Tungsten is used in the form of tungsten carbide and tungsten alloys. Tungsten carbide is a compound of tungsten and carbon, which is used in the production of tools, such as drills and saws. Tungsten alloys are used in the production of materials such as springs, wire and bearings.

Tungsten is used in a variety of industries, including electrical and electronics, automotive, aerospace, defense, and medical. It is used in the production of light bulbs, capacitors, transistors, and other electrical components. In the automotive industry, tungsten is used in spark plugs and catalytic converters. In the aerospace industry, tungsten is used in jet engines and turbines. In the defense industry, tungsten is used in armor plating and missiles. The annual usage of tungsten also includes its use in the production of jewelry. It is used in the production of rings, bracelets, and necklaces. Tungsten is also used in the production of coins and medals. Overall, tungsten is used in a variety of industries and is an essential element in the production of many modern technologies and materials.

TUNGSTEN PRODUCTION IN THE WORLD :

China is the largest producer of tungsten, providing a majority of the world's production. China also has the world's largest reserves of tungsten ores. Initially,Russia was the second-largest tungsten producer in the world, followed by Europe. Currently, it is Vietnam which is the second largest tungsten producer. The United States is also among one of the top tungsten producing countries, having some of the richest tungsten reserves in the world. Other tungsten producers in the world include Bolivia, United Kingdom, Austria and Canada.

 

Rank

Country

Tungsten production (metric tonnes)

1

 China

79,000

2

 Vietnam

7,200

3

 Russia

3,100

4

 Bolivia & UK

1,100

5

 Austria

950

 

 

 

 

 

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