Graphite purification: accounting for two methods of chemical purification and physical purification. Graphite Electrode supplier shares with you.
1. Chemical purification: It uses graphite's acid resistance, alkali resistance and corrosion resistance properties to treat graphite concentrate with acid and alkali to dissolve impurities and then wash them away to improve the concentrate grade. High-carbon graphite with 99% grade can be obtained by chemical purification. There are various methods for chemical purification. The most widely used domestic method is the high-temperature melting method of sodium hydroxide.
The basic principle is to make the impurities in graphite (mainly silicate minerals) react with caustic soda, namely NaOH, under high-temperature conditions above 500 ° C, to form water-soluble reactants, and leaching the reactants with water can remove some impurities. Another part of impurities, such as iron oxides, is neutralized with HCl after alkali melting to form soluble sub-water ferric chloride, which can be removed by washing with water.
In the above process, the NaOH concentration is about 50%, and it is mixed with graphite at a ratio of 1: 0.8, that is, the production of 1 t of high-carbon graphite consumes about 0.4 t of NaOH. The amount of HCl added is about 30% of graphite. Fuel coal is about 0.6-0.7t. The equipment used in the alkaline melting method mainly includes anchor mixers, melting furnaces, propeller mixers, V-type washing tanks and the like. The recovery rate is 85-90%, and the investment is 150,000-200,000 yuan. Although this process is more advanced, it also has insufficient water consumption, graphite loss, low productivity, large alkali consumption, and environmental pollution caused by discharged waste liquid.
For the above reasons, the cost is higher. In order to solve or improve the above-mentioned shortcomings, the Rock and Mineral Testing Center of Henan Provincial Bureau of Geology and Mineral Resources have developed a new process for purifying high-carbon graphite, replacing the V-type washing tank with centrifugal washing, and recycling the waste liquid after treatment. Using this new process can reduce material costs by about 50%, save water by about 50%, increase yield by about 10%, and reduce environmental pollution from the waste liquid. The fixed carbon content of graphite is more than 99%, and the recovery rate is 92.8%.
2. Physical purification: high-temperature purification. Using the high-temperature resistance properties of graphite, it is placed in an electric furnace, and the air is heated to 2500 ° C, so that the ash (ie impurities) is volatilized, thereby improving the concentrate grade. High-temperature purification can obtain high-purity graphite with a grade of 99.9%.
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