Introduction and industry application of chrome ore

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Chrome has stronger siderophile affinity than oxytropism. Besides, its sulphophile will only be displayed under the reduction or high density sulfur conditions. In the endogenic process, chrome is often in trivalent state, in which the six acid sites of Cr3+, Al3+ and Fe3+ will have extensive isomorphism as they have close ionic radius. In addition, the elements such as Mn, Mg, Ni, Co, Zn and so on can replace chrome as isomorphism. Therefore, chrome is widely distributed in magnesium iron silicate mineral and auxiliary mineral. Under the strong conditions of epigenetic zone (such as the alkaline medium), Cr3 will be oxidized to chromic acid radical ion in the form of Cr6+, which will change the inactive ion into soluble chromium ion that can migrate. When Cr3 is reacted with the ions (such as Cu, Pb and so on) that has very strong polarizability, they will form insoluble chromium acid mineral.

Currently the discovered chrome-bearing ores in nature are about more than 50 kinds which respectively belong to oxides, chromates and silicates as well as minority of hydroxides, iodate, nitride and sulfide, among which the chromium nitride and cadmium sulfide minerals only can be found in the aerolite. Chromium minerals that have commercial value all belong to picotite type minerals, of which the general chemical formula are (Mg, Fe2+)(Cr, Al, Fe3+)2O4 or (Mg, Fe2+)O(Cr, Al, Fe3+)2O3. Among them, Cr2O3 content is within the ranges of 18 percents-62 percents. Chrome minerals that have industrial value often have more than 30 percents of Cr2O3 content, in which the common ores are as follows:

Chromite

Chromite

The chemical component of chromite is (Mg, Fe)Cr2O4, which ranges between ferrous chromite (FeCr2O4 that contains 32.09 percents of FeO and 67.91 percents of Cr2O3) and magnochromite (MgCr2O4 that contains 20.96 percents of MgO and 79.04 percents of Cr2O3). However, some people often call ferrous chromite and magnochromite as chromite. Chromite, belongs to the isometic system, of which the crystal is in small octahedron and often has granularity and dense clumps aggregate. It is in black, while its striation is in brown. It has submetallic luster with the hardness of 5.5 and specific gravity in the range of 4.2-4.8. Besides, it also has low-magnetic. Chromite is the leading raw material in smelting chrome, in which the iron-rich inferior ores can be used as the high grade refractory.

Chrome-rich spar

Chrome-rich spar is also known as picotite or alumchromite. Its chemical component is Fe(Cr, Al)2O4 which contains 32 percents to 38 percents of Cr2O3. Its morphology, physical property, genesis, occurrence and usage are all same with chromite.

Chrompicotite

The chemical component of chrompicotite is (Mg, Fe)(Cr, Al)2O4 which contains 32 percents to 50 percents of Cr2O3. Its morphology, physical property, genesis, occurrence and usage are also all same with chromite.

Chrome ore resource in china is poor. According to the demand requirements, it belongs to the shortage resource. Rich ores occupy 53.6 percents in 10.78 million tons of total chrome ore reserves. There are 56 chrome ore producing areas which distribute in Xizang province, Xinjiang province, Inner Mongolia, Gansu province and other nine provinces (regions), among which Xizang province is the leading producing area that has about half of the nation’s recoveralble deposits. China chromium deposit is a typical kind of magmatic deposit that relates to the ultrabasic rocks, in which the vast majority belongs to the ophiolite type and the deposits occur in the ophiolite zone. Chrome ores in Luobusha, Xizang province and Saertuohai, Xinjiang province and so on all belong to the above class. According to the mineralogenetic epoch, chrome ore is mainly formed in Mesozoic and Cenozoic. As chrome ore is a kind of shortage mineral in china, which has little reserves and lower productivity, more than 80 percents of its consumption per year needed to be imported.

In the metallurgical industry, chrome ore is mainly used to produce ferrochrome and metal chrome. Ferrochrome, served as the additive of steel, can be used to produce various high strength, corrosion-resistant, wear-resistant and antioxidant special steel, such as stainless steel, acid-resistant steel, ball-bearing steel, spring steels, tool steel and so on. Metal chrome is mainly used in the cobalt, nickel and tungsten to smelt special alloy. These kinds of special steel and special alloy are the indispensable materials in aviation, aerospace, automobile and shipbuilding as well as the production of guns, missiles, rockets, naval vessels and so on in the national defense industry.

Chromite can be also used to produce chrome brick, chrome magnesite brick and other special refractory materials. In the chemical industry, chromite is mainly used to produce sodium dichromate and further produce other chromium compounds which can be used in the pigment, textile, electroplate, tanning and other industries. Besides, chromium powder can be used as the catalyzer and catalyst.