Bolu Tiancheng New Energy Technology Co., Ltd. - Negative electrode material processing

There are usually two methods used to remove impurities from graphite. One is to increase the graphitization temperature and prolong the graphitization time. Raising the graphitization temperature to about 3000 ℃ and maintaining it for 15-50 hours can reduce the ash content to below 0.07% and the boron (B) content to 0.5PPm. Impurities with low boiling points such as Si, Ca, Al, Mg, etc. have evaporated.

The principle of gas impurity removal:

(1) Do not introduce new impurities

(2) Attention should be paid to not reducing the amount of purified gas:

① When the gas to be purified contains multiple impurities, the order of impurity removal is generally to first remove acidic gases such as hydrogenated gases, CO2, SO2, etc. Water vapor should be removed before purification.

② When selecting methods for impurity removal, it is important to ensure that all impurities are completely removed. For example, when removing CO2, NaOH is used instead of Ca (OH) 2 solution because Ca (OH) 2 is a slightly soluble substance. The concentration of Ca (OH) 2 in lime water is low, making it difficult to completely absorb CO2.

Method:

A. Impurity conversion method: To remove phenol from benzene, hydrogen oxidation can be added to convert phenol into sodium phenolate, which is easily soluble in water and separated from benzene;

B. Absorption washing method; To remove a small amount of hydrogen and water mixed in carbon dioxide, the mixed gas can be first passed through a saturated sodium bicarbonate solution, and then passed through to remove it;

C. Precipitation filtration method: To remove a small amount of copper sulfate mixed in the ferrous sulfate solution, add a small amount of iron powder, wait for sufficient reaction, and filter to remove insoluble substances;

D. Heating sublimation method: This method can be used to remove sand from iodine;

E. Solution extraction method: To remove a small amount of bromine from water, this method can be used;

More troublesome are refractory metals, which form high melting point carbides such as boron carbide (B4C) with a melting point of 2350 ^, but do not boil until 35001 and form stable displacement solid solutions in the graphite structure The neutron capture cross section of vanadium is 5 bar, and the formed carbides do not dissolve until 2800T. In order to remove these harmful impurities, halogen gas purification methods are widely used in countries around the world.