The dominant methods of tungsten ore dressing are physical mineral processing, such as preconcentration, gravity separation, flotation and magnetic separation. For difficult dressed medium mineral and low grade concentrate, chemical mineral processing can be used. According to mineral washability, the tungsten ore dressing can be classified into two kinds, black tungsten ore dressing process which gives priority to gravity separation and white tungsten ore dressing process which gives priority to flotation.
Black tungsten ore dressing process
Black tungsten ore features high ore dilution rate, low grade, coarse mineral disseminated grain size, large density, low hardness, easy to be pelitization and dark color. So dressing method gives priority to gravity separation.
The process flow consists of four parts, preconcentration, grading gravity separation, selectness and comprehensive recovery, and fine mud treatment.
Preconcentration of black tungsten ore will do ore washing and desliming and classification at first. The preconcentration adopts hand picking, photoelectric dressing and heavy media separation. The used dressing equipments are heavy media precessing machine and photoelectric dressing machine, etc.
Gravity separation method is the main method of black tungsten ore dressing process. The tungsten ore has large density so gravity separation method can effectively separate the tungsten ores from many minerals grains whose density is less than 3.5-4. In gravity separation, jigger and shaking table are the most commonly used devices. When dressing the black tungsten ores with coarse and medium disseminated grains, jigger has an important role. So before dressing, the ores are sieved, graded for jigging. Jigger are used in grinding cycle to reduce tungsten ore pelitization and the tungsten ores that are monomer disintegrated before it is too late. Jigger can dress the tungsten ore concentrates, which is more than 50% of factory total recovery.
After preconcentration, the ores can be crushed into -12mm then come through gradation and gravity separation. The coarse ore grains will come through three level jigging. Jigger work gives priority to twin-bucket diaphragm jigger. The large dressing plant uses 1000mm×1000mm MeXaHoБp jigger. The saking table gravity separation can be done in 4-6 level. Before shaking table gravity separation, a stage of two stage ore grinding should be finished. There is also the ore grinding process for medium ores regrinding. One stage ore grinding adopts rod mill. Two stages ore grinding adopts ball mill or rod mill.
The separation uses bracket system and convex roller shaking table. In China, some tungsten ores dressing plants adopt spring type shaking table. Large and medium tungsten ores dressing plant have selectness and associated metal comprehensive recovery process. In small tungsten ore dressing plants, the coarse concentrates are sent to special concentration plants for selectness and associated metal comprehensive recovery. The selectness will use gravity separation, table flotation, the flotation, magnetic separation, electric separation and chemical dressing, etc. Selectness recovery is 95%-98%. Shaking table is used in selectness to further enhance the grade of tungsten concentrates. Table flotation and flotation can do comprehensive recovery of associated sulfide ores. The magnetic separation and electric separation can separate the black tungsten ores, tin stone and nb-ta mineral, etc.
White tungsten ore dressing method and white tungsten ore dressing technology
Chemical mineral processing is used for processing the tungsten medium ores which are hard to be dressed and the concentrates with low grade to produce complex white tungsten ore and ammonium paratungstate. According to the ore dipping characteristics, the white tungsten ore dressing process will use the combined gravity separation and flotation, or single flotation. Individual white tungsten concentrator will do preconcentration.
The white tungsten ores features with good flotability. For there are many kinds of calcium contained gangue minerals whose properties are similar to white tungsten ores, such as calcite, fluorite and apatite, etc. These gangue minerals will lead to the complexity of flotation process. To improve the selectivity of flotation process, polyvalent metal salt will be added into sodium silicate so that the white tungsten flotation effect can be enhanced effectively.
The white tungsten ores are associated with sulfide ores, especially with pyrrhotite. In quartz, there are a few amount of monomer white tungsten ores produced. The crushing process is three stage and a closed-circuit process. The largest size of raw ores is 450mm and the crushing final size is 10mm. The ore grinding is a stage of closed-circuit. The grain size of white tungsten ores is 0.1-0.2mm, the larger one is 0.6mm and the minimum is 0.016mm. The flotation is part differential flotation.
White tungsten ores flotation process can adopt two coarse concentration, three scavenging and five selectness. The white tungsten ores that are got are the first grade and first level. The associated useful elements, such as copper and sulfur, will be recycled in production.
Tungsten ores crushing and grinding devices
Tungsten ores crushing and grinding devices are the main 7 kinds, 1. Vertical impact crusher; 2. Vertical impact fine crusher; 3.Reversible impact crusher; 4. Reversible hammer crusher; 5. Roller crusher; 6. Cone crusher; 7. Rod mill.