After spherical graphite making,purification is a necessary processing step for anode material produced by natural graphite. For natural graphite, normally after mineral processing, the fixed carbon content of the graphite concentrate can reach 95%, but to make anode material, the fixed carbon should be upgraded to 99.95% above. So various impurities inside the natural graphite concentrate should be removed sufficiently. Now for the purification process on natural graphite, high temperature purification and chemical purification are the two main technological directions.
Silica is the most difficult to be removed, and by using high temperature to 2700 degree, the silica and other impurities will be vaporized and get out from the graphite. By this process the fixed carbon content can be improved to 99.99% above. However, due to the high requirement on the high temperature furnace and the huge investment, high temperature purification furnace is now still under development and only small quantity trial is applicable. Another way of high temperature purification is to use graphitization furnace, but the disadvantage is that the production cost will be extremely high.
Besides the high temperature purification, chemical purification is commonly used now for natural graphite purification. Because of the mineral characteristic, hydrofluoric acid is necessary to be used for purifying natural graphite during chemical processing, together with other acids. The dosage and scheme of different acids and chemicals for chemical purification plant can be concluded via conditional tests in laboratory.
Prominer can conduct the chemical purification test to conclude various conditions for the purification plant design and proposal.