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About high-purity graphite

wallpapers News 2021-08-16
High-purity graphite generally refers to graphite with carbon content greater than 99.99% and a total ash content ≤ 50ppm. According to different uses, it is divided into 50×10-6, 20×10-6, 10×10-6, and other levels.
The production of high-purity graphite in China is basically based on the Acheson furnace and is equipped with a purification ventilation system. As the Acheson furnace has a large amount of power and heat loss, the heat utilization rate is very low. In the chemical purification method, the best reaction can only be carried out at high temperatures. Generally, the furnace temperature is required to be above 2800℃. The higher the furnace temperature is, the more reaction time and the better the purification effect. It can be seen that the temperature has a significant effect on the purification effect. Although the gas distribution is uniform, if the relationship between the purification temperature and the time is improper, the purification effect will not be improved.
In order to ensure that the graphitization furnace has a higher temperature, the electricity consumption per ton of products is more than twice as high as the graphitization of ordinary products. The average consumption per ton is generally around 10,000 degrees according to the weight of the calcined blank. At the same time, the width of the furnace core should not be too large, generally, 1.2 ~ 1.6 meters, so that it will not only better improve the temperature and insulation effect in the furnace core, prevent harmful gases from leaking from the sidewall, but also facilitate the access The gas can fully concentrate the reaction.
Some countries even produce blanks of superfine particles (5-10μm in size) and nano-sized particles. We know that the higher the density of the blank, the finer the particles, the larger the volume, and the more difficult it is to process the graphitization purity. First, the furnace temperature should not rise too fast; otherwise, product cracking will easily occur. Second, because the bulk density is too high, it is difficult for the halogen gas to penetrate into the product, which prolongs the reaction time and speed.
In addition to the temperature factor, the total ash content of the purified graphite products is high and low. Another key factor is the gas flow rate and whether the control of the gas flow in each temperature stage is reasonable. Experience has proved that according to the different requirements of product structure, performance and users, each ventilation rate is generally 6-10% of the total furnace capacity of the blanks. For products with small specifications and coarse structures, the lower limit can be used, and vice versa, the upper limit and medium specifications and negative electrode materials can be selected appropriately in the middle limit. If users have special requirements for total ash, sometimes the upper limit needs to be exceeded.
The halogen gases commonly used in chemical purification methods mainly include chlorine (Cl) and fluorine (also known as Freon), among which fluorine is divided into two fluorine monochloromethane (CHClF2, R22, F22), difluoromethylene chloride (CCl2F2, Freon-12, R12), and nitrogen (N2), argon (Ar).