In China, the chrome beneficiation of ore has been carried out using jigs, shakers , spiral ore dressers, centrifugal ore dressers, and belt chute to separate chrome-depleted ore from various places (Cr203 <20%). Mine in a shaker. Dry strong magnetic separation, wet strong magnetic separation, flotation and various chemical beneficiation methods have been studied in the laboratory. However, in the production practice, the reselection method is mainly used, and some mines use strong magnetic separation.
Since 1967, China has built five small beneficiation plants in Zunhua, Hebei, Miyun, Beijing, Shangnan, Shaanxi, Inner Mongolia, and Saltohai, Xinjiang, and reselection has been used. The first three have been followed by mining. Discontinued. The existing Sauron Mountain Concentration Plant was prepared in 1985. It has an annual output of 3,000 to 4,000 tons of concentrate powder at a design scale, and the selected ore grade is 25%. After reselection, the concentrate grade is 40%. For the strong magnetic separation process, it was put into production in 1986.
At present, the smelting of chromium ore in China is mainly the electric furnace method in pyrometallurgical smelting, followed by metal thermal reduction method and vacuum carbon reduction method and converter method. Electric furnace method is divided into ore heat method and refining electric furnace method. The former uses carbon as the reducing agent to produce high-carbon ferrochrome using chromium ore, coke, and silica as raw materials, or the silicon-chromium alloy using silica, coke, and high-carbon ferrochrome as raw materials; the latter uses silica as the reducing agent and uses chromium ore , Silicon chromium alloy, lime as raw materials to produce medium and low carbon ferrochrome and microcarbon ferrochrome. It is also useful for converters to produce medium and low carbon ferrochrome.
The metal thermal reduction method usually uses aluminum particles as a reducing agent, so that the chromium oxide reacts violently in a short time, releases a large amount of heat, and smelts metal chromium.
The vacuum carbon reduction method uses high-grade chromium ore (currently, high-carbon ferrochromium after oxidation roasting) as an oxidant, and agglomerates with high-carbon ferrochrome powder, puts it into a vacuum furnace, and decarburizes at a temperature lower than the melting point of the metal. , To produce micro-carbon, ultra-micro-carbon ferrochrome; or pass nitrogen after decarburization to produce nitrogen-containing ferrochrome.
In wet smelting, chromium ore, soda ash, dolomite or limestone are put into a rotary kiln for oxidation and roasting to produce sodium chromate. After water immersion, sodium sulfide or sulfur is added to reduce it to chromium hydroxide precipitate. Chromium is then produced by metal thermal reduction or vacuum carbon reduction and electrolysis.
In addition to the above smelting methods, in recent years, China has studied a method for recovering chromium from Jinchuan copper-nickel tailings in Gansu. The method uses oxidation roasting to produce chromium hydroxide, and then turns it into chrome ammonium alum, and finally electrolyzes metal chromium. The Chinese Academy of Sciences has also developed a new process for the extraction of chromium from primary amines, with a chromium extraction rate of 98% and a back extraction rate of 100%. The purity of Cr203 product is 95% -98%, which provides a basis for the comprehensive utilization of the associated chromium in Hongge iron ore in Panzhihua-Xichang area.
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