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Tungsten is a rare metal that is widely distributed and found in almost all kinds of rocks. Because of its low content,the extraction of tungsten can only use relevant geological processes. At present, there are more than 20 kinds of tungsten ores have been found in nature, among which scheelite and wolframite have higher mining value and are the main sources of tungsten resources.
In extraction of tungsten ore, the processes used to extract scheerite and wolframite are also very different due to the differences in mineral properties and deposit types. Below, we introduce the ore properties and extraction methods of scheerite and wolframite respectively.
One. Extraction of tungsten ore: Scheelite
Scheelite is generally sandston-type, complex (veined disseminated type-vanite skarn complex), often with a variety of molybdenum and bismuth and other non-ferrous metal minerals associated or symbiosis, the useful mineral mosaic particle size is fine, most of the are embedded in the ore as the disseminated state.
According to the mineral dissemination, the scheerite extraction process can be divided into gravity separation process and froth flotation process. Generally, the gravity separation process is used to deal with coarse disseminated scheerite, thus obtaining alloying scheerite. The froth flotation process is often used to deal with fine disseminated scheerite.
• Scheerite extraction process - gravity separation process
The relative density of scheelite is 5.8-6.2, which is quite different from the mineral density of gangue. Therefore, the qualified scheelite can be obtained directly by the gravity separation process.
• Scheerite extraction process - froth flotation process
Scheelite has good natural floatability,and its flotation process can be roughly divided into two parts: Roughing is mainly to maximize the recovery rate of scheelite, while cleaning is to get qualified tungsten concentrate. Several times of cleaning are often needed to get qualified tungsten concentrate.
Scheelite roughing: Lime method is the commonly used methods, which uses the Ca2+ to adsorb in the gangue mineral surface, changing the potential on the surface of the gangue mineral, then adds the sodium carbonate to precipitate Ca on the surface of gangue minerals, and absorbs the Ca on the scheelite surface, but the surface charge remains the negative electricity, without producing CaCOs precipitation. Therefore, adding sodium silicate can only suppress the gangue minerals, without effect on the white scheelite, so as to achieve the separation of tungsten and the gangue minerals.
Scheelite cleaning: The key is to separate the calcium-containing gangue mineral from scheelite. The commonly used processes are the normal temperature method and the heating method. The normal temperature method does not have strong adaptability to the ore, and the separation index fluctuates greatly. The grade of floated scheelite concentrate is generally 55%-60% with high impurities. Adding hydrochloric acid can obtain the scheelite concentrate with a recovery rate of 65%. The essence of the heating method mainly refers to the thickening of scheelite concentrate obtained from roughing, the pulp concentration is between 60%-70%, and then add a lot of water glass then mix it at high temperature, finally dilute the pulp,and then adopt froth flotation at normal temperature.
Two. Extraction of tungsten ore: Wolframite
Wolframite is usually quartz large vein type or vein-grain type deposit, wolframite is usually thick plate or vein-graintype crystal enrichment in quartz, the mosaic particle size is coarse, easy to separate. For the gangue minerals with which wolfram is associated, the density of wolfram is relatively high, and the combined beneficiation technology based on gravity separation process is generally adopted as the extraction process of tungsten ore, which can be divided into roughing, gravity separation, cleaning and fine mud treatment, etc.
• Wolframite roughing:
Because the uneven distribution of wolframite in quartz gangue, the wolframite is usually in the shape of thick plate or vein lets, and the vein is narrow and the thickness is not uniform. So, it is necessary to conduct manual waste separation before separation.
• Wolframite gravity separation:
Generally, multi-stage jigging, multi-stage shaking table, middlings re-grinding process. The qualified ore after classification of vibrating screen is sent to multi-stage jigging to output jigging rough sand, the coarse grained jigging tailings is sent to the rod mill for re-grinding, the fine grained jigging tailings after classification of hydraulic classifier is sent into multi-stage shaking table, and produce shaking table rough sand with one roughing and one scavenging. The shaking table tailings is discharged to the tailings pond, and shaking table middlings is returned to re-grinding and re-separation, the roughing sand obtained by the jigging and shaking table enters to cleaning operation.
• Wolframite cleaning:
The flotation-gravity separation or flotation - gravity separation - magnetic separation processes are generally adopted, and the associated elements are recovered in the cleaning section.
Through the coarse-grained and fine-grained table flotation and machine flotation to remove sulfide ore, the sulfide ore of table flotation and machine flotation merge into the sulphide ore flotation separation. The wolframite of table flotation and machine flotation further produce the wolframite concentration by the gravity separation process. If the wolframite contains scheelite or cassiterite, adopting the gravity separation-flotation and gravity separation - flotation - magnetic separation (electricity) process can select the wolframite concentrate, scheelite concentrate and tin concentrate.
• Wolframite slime treatment:
Normally, the slime of wolframite is treated separately. Desulphurization is carried out first, and then adopting the separation process (such as gravity separation,flotation, magnetic separation, electrical separation) or a combination processes to extract the tungsten according to the properties of fine mud material. Meanwhile,the associated metal minerals are also recovered and utilized comprehensively.
The above are the common processed used for the extraction of tungsten ore. In addition, magnetic separation and electrical separation are also used in the extraction of tungsten ore, mainly used for the separation of wolframite and scheelite, wolframite and cassiterite, scheelite and cassiterite, and ferromagnetic ores.
For the extraction of tungsten ore, it is necessary to determine the ore composition of tungsten minerals and the separation degree. It is recommended to find qualified manufacturers to carry out mineral processing test, customize the actual situation of the process flow according to the report result..