The Scheelite Flotation Process—Lime Method
In our country the white tungsten deposit is mostly a skarn shape deposit, this kind of characteristic of scheelite ore bed is “lean, multiple, thin, miscellaneous”, especially the “miscellaneous”, caused a variety of obstacles to white tungsten ore dressing.
Most white tungsten deposit are associated with calcite, fluorite, barite, such as calcium containing gangue, because of the flotability is close to scheelite so is hard to separate.
For many years Petrov method is commonly used for the white tungsten flotation method, namely high temperature flotation process, this process must be heating flotation, high energy consumption, the operation is complicated. Following the development of the technology, finally developed a flotation process at room temperature in the 70s.The most representative of flotation process at room temperature is 731 flotation method at room temperature and method of lime, here’s to emphatically introduce lime method.
Scheelite flotation process- lime method first invented by the American company, is to stir with the right amount of lime slurry, then adding sodium carbonate, sodium silicate, selective inhibition of containing ore vein, and white tungsten can still maintain good flotability. This method not only can be carry on at room temperature, also the dosage of sodium silicate can be greatly reduced, especially in the presence of fluorite scheelite has excellent selectivity.
Mechanism of lime method is: the addition of lime white tungsten and fluorite surface adsorption Ca2+，and lead to different change of their surface potential, surface potential of fluorite from negative to positive, surface potential of scheelite remains in negative territory. Join the Ca2+ in aqueous solution of sodium carbonate, can adsorption in the positively charged surface of fluorite and formed by the Ca2+ and formed into CaCO3 covering layer, after the coating with sodium silicate strong inhibition to fluorite. Since tungsten surface without any precipitation, so it can continue to the role of fatty acid and plankton.
The most typical used of lime method w polymetallic tungsten ore in Hunan province, the mine flotation ore grade of WO3 in the method of lime is 0.39% of scheelite, through roughing closed-circuit test obtained WO3 grade is 3.53%,recovery 77.01% of white tungsten rough concentrate. The acidification of the select open circuit test, by adding sodium silicate, obtained the final WO3 of flotation concentrate grade of 42.12%,a good indicator of recovery is 46.26%. Concentrate product XRD spectra analysis shows that the fluorite and calcite in lime method roughing and select a strong inhibitory effect have been obtained respectively, sheelite and gangue mineral calcium can achieve effective separation, the research result shows that lime method is an effective way to achieve white tungsten plants the flotation.
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