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Click to add WeChatThe main useful components of tungsten ore are tungstates, of which wolframite and scheelite are common. Wolframite has a high tungsten content and also contains elements such as iron and manganese; scheelite is mainly composed of calcium, tungsten and oxygen. So how do these tungsten ores extract tungsten? Let's learn about it from three aspects: the properties of tungsten ore, tungsten ore beneficiation methods and tungsten ore extraction methods.
Wormite Type: The ore is mainly composed of wolframite, which often coexists with gangue minerals such as quartz, mica, and feldspar. Its characteristics are that the ore grade is relatively high, and the tungsten content can reach more than 50%, but the ore reserves are relatively small. This type of ore has a certain distribution in southern my country, such as Jiangxi and Hunan. In the process of mineral processing, due to the high density of wolframite and its magnetic (weak magnetic), gravity separation, magnetic separation and other methods can be used for preliminary enrichment.
Scheelite type: The ore contains scheelite as the main useful mineral, and is often associated with gangue minerals such as calcite, fluorite, and apatite. The reserves of scheelite-type ore are relatively large, but the grade is generally low, with a tungsten content of about 10% - 30%. It is widely distributed worldwide, and there are more scheelite resources in Henan, Gansu and other places in my country. The beneficiation method of scheelite is relatively complicated, and it is usually necessary to use flotation and other methods for separation. And because it has similar surface properties to some gangue minerals, it is necessary to accurately control the flotation reagent system.
Black and white mixed ore type: The ore contains both wolframite and scheelite. This type of ore is difficult to beneficiate. It is necessary to use a variety of methods such as gravity separation, flotation, and magnetic separation, and carry out step-by-step or joint treatment according to the different properties of wolframite and scheelite to achieve effective recovery of tungsten.
Gravity selection is based on the difference in mineral density. Under the action of external forces such as gravity field or centrifugal field, mineral particles of different densities are layered or graded according to density, thereby achieving mineral separation. For tungsten ores, the density of wolframite and scheelite is greater than that of common gangue minerals (such as quartz density of about 2.65g/cm³, feldspar density of about 2.5-2.7g/cm³). In the process of gravity separation, through the action of water flow or mechanical force, such as the use of periodic up and down alternating water flow in the jig, and the combined action of horizontal water flow and vertical shaking in the shaking table, the dense tungsten ore particles tend to be enriched at the bottom of the equipment or in a specific area, while the low-density gangue minerals are separated out.
Gravity separation is suitable for processing coarse-grained tungsten ores, especially wolframite-type ores, because wolframite has a large density and a relatively coarse embedded particle size. Gravity separation can quickly and effectively remove a large amount of gangue minerals and improve the grade of the selected ore.
Flotation is based on the difference in the physical and chemical properties of the mineral surface, especially the wettability of the mineral surface to achieve mineral separation. In the flotation process of tungsten ore, for the flotation of scheelite, a suitable collector is usually used to make its surface hydrophobic. Fatty acid collectors react with calcium ions (Ca²⁺) on the surface of scheelite under alkaline conditions to make its surface hydrophobic; phosphonic acid collectors make it hydrophobic by forming chemical bonds with tungstate ions (WO₄²⁻) on the surface of scheelite. At the same time, adding a foaming agent (such as pine oil) produces a large number of stable bubbles, and the hydrophobic scheelite particles adhere to the bubbles and float to the surface of the slurry with the bubbles to form a foam layer, while the gangue minerals remain in the slurry.
Flotation is mostly suitable for processing fine-grained scheelite and mixed scheelite, which can effectively separate tungsten ore from gangue minerals and improve the grade of tungsten concentrate.
Magnetic separation is to use the magnetic difference of minerals for mineral selection. Scheelite has weak magnetism, while scheelite is generally a non-magnetic mineral, and gangue minerals are mostly non-magnetic or weakly magnetic. During the magnetic separation process, the ore is sent into the magnetic field of the magnetic separator. The relatively strong magnetic wolframite particles will be adsorbed on the magnetic poles by the magnetic field, while the non-magnetic scheelite and gangue minerals are not affected by the magnetic field, thus achieving the separation of wolframite from other minerals.
Magnetic separation is mainly suitable for separating wolframite, and plays an important role in the enrichment of wolframite in wolframite-type ore or black and white tungsten mixed ore.
Crushing and screening: The raw ore is first crushed, and the crushed ore is screened to separate the ore into different particle sizes, such as coarse particle size (greater than 10mm), medium particle size (1-10mm) and fine particle size (less than 1mm). The equipment required in the process is mainly jaw crusher, cone crusher and vibrating screen. Among them, the jaw crusher uses the extrusion of the moving jaw plate and the static jaw plate to crush the ore, which is suitable for coarse crushing; the cone crusher squeezes the material through the movement of the mortar wall to the crushing wall, which can achieve medium and fine crushing;
The vibrating screen uses the exciting force generated by the vibration motor to vibrate the screen, and the material is layered on the screen according to the particle size and separated through the sieve holes.
Grinding and classification: The screened ore is ground as needed to fully separate the tungsten ore and the gangue minerals. Grinding usually uses equipment such as ball mills and rod mills. The ball mill grinds the ore through the impact and grinding of steel balls. The slurry after grinding enters the classification equipment, such as spiral classifiers, hydrocyclones, etc. for classification. The spiral classifier uses the different precipitation speeds of solid particles in the liquid to separate the coarse and fine slurry by the rotation of the spiral blades; the hydrocyclone uses the centrifugal field to separate the particles in the slurry according to the particle size. After classification, the qualified particle size pulp enters the subsequent beneficiation process, and the unqualified particle size returns to the grinding machine for further grinding to ensure that the grinding fineness meets the beneficiation requirements.
Soda sintering method: is to mix tungsten ore with soda (sodium carbonate, Na₂CO₃) and then sinter at high temperature, so that the tungstate in the tungsten ore reacts with soda to form water-soluble sodium tungstate (Na₂WO₄). At high temperature, the reaction is fully carried out, the generated sodium tungstate is soluble in water, and the gangue minerals form insoluble residues, thereby realizing the initial separation of tungsten and gangue. The sintering temperature is generally between 800-900°C, and the sintering time is determined according to the properties of the ore and the equipment conditions, usually 1-3 hours. The sintered product is leached with water to dissolve sodium tungstate in water, obtaining sodium tungstate solution and insoluble residue. The residue is separated by filtration and other methods, and the sodium tungstate solution enters the subsequent purification process.
High-pressure leaching: is to use a strong alkaline solution (such as sodium hydroxide or potassium hydroxide solution) to react chemically with tungsten ore under high temperature and high pressure, so that the tungsten in the tungsten ore is dissolved into the solution in the form of tungstate, thereby realizing the separation of tungsten from gangue minerals.
The above is the complete content of tungsten ore extraction method and process. In the actual beneficiation process, there are many types of tungsten, and the types of gangue minerals they are rich in are also different. You cannot blindly choose the beneficiation method. If you want to obtain a more ideal tungsten recovery rate, it is recommended to conduct a tungsten beneficiation test first. Through experimental analysis, a more suitable tungsten beneficiation process plan can be designed. At the same time, a complete set of tungsten ore beneficiation equipment can be customized according to the plan.
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