Graphite is one of the highest boiling point substances in nature melting, melting at 3 850 ± 50 ℃, boiling point is 4 500 ℃, and the boiling point of silicate minerals are 2 750 ℃ (quartz boiling point) or less, well above the boiling point of graphite impurities contained in the boiling point of the silicate. This feature is the basis of high-temperature purified graphite reason perish.
The graphite powder directly into a graphite crucible and heated in inert gas and freon protective gas purification furnace to 2 300-3 000 ℃, a period of time, impurities in the graphite will overflow to achieve graphite purification. High-temperature method commonly used by flotation or more chemically purified 99% of the carbon-carbon graphite as raw material, can be purified graphite to 99.99%, for example, by further improving the process conditions, improve the crucible quality, purity up to 99.995% the above.
High-temperature method can produce more than 99.99% of ultra-pure graphite, but requires to be fixed carbon materials in more than 99 percent, and the equipment is expensive, the huge investment, production scale has limited electric heating technology is demanding and require isolation from the air, or else graphite when the temperature was raised to 450 ℃ in hot air begins to be oxidized, the higher the temperature, the greater the loss of graphite. Only very high quality graphite specific industries (such as defense, aerospace, etc.) using the high-temperature method for small batch production of high-purity graphite.
A lot of research and production practice show that, in many purification methods graphite, although the advantages and disadvantages, but alkali acid method because the production process is simple, easy production environment, lower production costs, does not produce toxic and hazardous waste, conventional waste fluid handling easier and more advantageous features. After roasting and leaching ore solve shorten time, improve the purification effect, to properly resolve issues such as waste water treatment, alkaline acid method may well be the best way to purify graphite industrial production.