Overview of China's chromium-poor ore dressing process

Of depleted of chromium ore beneficiation, has used jigger, shaker, spiral concentrator, centrifugal concentrator and belt sorting through the chute around the depleted chromium ore (Cr 2 O 3 <20% ), but also water power sorting The pipe was selected to pass the shaker in the mine. Dry strong magnetic separation, wet strong magnetic separation, flotation and various chemical beneficiation methods were studied in the laboratory. However, in the actual production, the re-election method is mainly adopted, and individual mines adopt strong magnetic separation.

Since 1967, China has built five small ore dressing plants in Zunhua, Beijing, Miyun, Shangnan, Inner Mongolia, Sauran, Inner Mongolia, and Salto, Xinjiang. The first three have been selected with the end of mining. Discontinued. The existing Solon Mountain plant was built in 1985. The designed scale has an annual output of 3,000-4,000 tons of concentrate powder, 25% of the ore grade, 40% of the refined grade after re-election, but the tailings grade is 10%. In 1986, it was put into production for the strong magnetic separation process.

Currently our chrome ore smelting mainly Pyrometallurgy electric furnace method, followed by metal vacuum thermal reduction and carbon reduction and converter method. The electric furnace method is further divided into a mineral thermal method and a refining electric furnace method. The former carbon as reducing agent, chromium ore, coke, silica raw materials to produce high-carbon ferrochrome, silica or coke, the raw material for the production of high carbon ferrochrome sichrome; the latter using silica as a reducing agent, chromium ore , silicon chrome alloy, lime as raw material to produce medium and low carbon ferrochrome and micro carbon ferrochrome. It is also useful to produce medium and low carbon ferrochrome in a converter.

Metal thermal reduction method commonly used as a reducing agent aluminum particles, chromium oxide vigorous reaction in a short time, emit large amounts of heat, melting the chromium.

The vacuum carbon reduction method uses high-grade chromium ore (currently used high-carbon ferrochrome after oxidizing roasting) as an oxidant, and is made into agglomerates with high-carbon ferrochrome powder, placed in a vacuum furnace, and decarburized at a temperature lower than the melting point of the metal. , production of micro-carbon, ultra-fine carbon ferrochrome; or decarburization and nitrogen gas to produce nitrogen-containing ferrochrome alloy.

Wet smelting is currently carried out by oxidizing roasting of chrome ore and soda ash and dolomite or limestone into a rotary kiln to form sodium chromate. After water immersion, sodium sulfide or sulfur is added to reduce it to chromium hydroxide precipitate, and dehydration calcination to obtain oxidation. 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 the method of recovering chromium from Jinchuan copper- nickel tailings in Gansu, which uses oxidizing roasting to prepare chromium hydroxide, then chrome ammonium ruthenium, and finally metal chromium. The Chinese Academy of Sciences has also developed a new process for the extraction of chromium by primary amines. The extraction rate of chromium is 98% and the stripping rate is 100%. The purity of Cr 2 O 3 product is 95%-98%, which provides a basis for comprehensive utilization of associated chromium in the red iron ore of Panzhihua-Xichang area.

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