The flotation method is one of the conventional mineral […]
The flotation method is one of the conventional mineral purification methods with less energy consumption and reagent consumption, and lower cost. This is the greater advantage of the flotation method to purify graphite. However, the use of flotation to purify graphite can only achieve a limited improvement in the grade of graphite. For flake graphite, the use of multi-stage grinding not only can not completely dissociate the monomer, but also is not conducive to protecting the large flakes of graphite. Therefore, it is neither economical nor scientific to use flotation methods to further improve the graphite grade. To obtain high-carbon graphite with a carbon content of more than 99%, the graphite must be purified by chemical methods.
(1) The chlorination roasting method. The low roasting temperature and low chlorine consumption of the chlorination roasting method greatly reduce the production cost of graphite. At the same time, the carbon content of graphite products is equivalent to that after treatment with hydrofluoric acid. In contrast, chlorination The roasting method has a higher recovery rate. However, because chlorine gas is toxic and corrosive, it has high requirements for equipment operation and requires strict sealing. The exhaust gas must be properly handled, which limits its promotion and application to a certain extent.
(2) Alkaline acid purification method. The carbon content of the graphite purified by the alkaline-acid method can reach more than 99%, which has the characteristics of low one-time investment, high product quality, and strong process adaptability. Moreover, it also has the advantages of conventional equipment and strong versatility (except graphite, many non-metallic minerals can be purified by alkaline acid method). The alkaline acid method is a method that is widely used in my country today; its disadvantage is that it consumes a lot of energy. , Long reaction time, large loss of graphite and serious wastewater pollution.
(3) Hydrofluoric acid method. The main advantages of the hydrofluoric acid method are high impurity removal efficiency, high-quality products, small impact on the performance of graphite products, and low energy consumption. The disadvantage is that hydrofluoric acid is highly toxic and corrosive. Strict safety protection measures must be taken during the production process. The strict requirements for equipment also lead to increased costs. In addition, the waste water produced by the hydrofluoric acid method is very toxic and corrosive. Strong, it needs strict treatment before it can be discharged. Environmental protection investment also greatly reduces the advantages of low cost of hydrofluoric acid method.
(4) The big advantage of the high temperature method is that the carbon content of the product is extremely high, up to 99.995%. The disadvantage is that the high temperature furnace must be specially designed and constructed, the equipment is expensive, the one-time investment is large, and the energy consumption is high. Electricity bills increase production costs. Moreover, the harsh production conditions make the scope of application of this method extremely limited. Only occasions with special requirements for the purity of graphite products, such as national defense and aerospace, consider using this method for small batch production of graphite, and it is still impossible to achieve promotion in the industry. Comparative analysis shows that the several methods of graphite purification have their own advantages and disadvantages. The alkaline-acid method is easy to operate, low production cost, and low production conditions. However, the fixed carbon content of the graphite produced is low, and it can't reach 99.9% from the current point of view. The hydrofluoric acid method has a good impurity removal effect, and the product has a high fixed carbon content, but the hydrofluoric acid is highly toxic and corrosive. It has strict requirements on safety protection measures and production conditions, and the wastewater is difficult to treat. The chlorination roasting method also requires strict sealing due to the toxic and corrosive chlorine gas. The high-temperature method can produce very high-grade high-purity graphite, but it cannot be promoted at present due to its own limitations and is only used in a small range.