The chrome ore deposits that have been explored are selected to obtain various grades of mineral products, which can meet the production needs of different industrial applications. The mining method of chrome ore is determined by the form of the ore layer. The dispersed deposits are often mined by open pit and the underground mining is mainly used for large scales. Most of the rich ore-rich ore-bearing minerals do not need to be beneficiated ; the dispersed ore deposits can be selected to obtain 50% chromium ore.
In addition to chemical grade and refractory grade chrome ore refractory plant and transported to other than chemical, high-grade chrome ore fed to the ferroalloy smelting plant as ferrochromium, as an alloying agent in the steel industry, or smelt metal chromium, as Additives for special alloys.
Since chromium is the most versatile metal, it ranks first in the “strategic metalâ€. Countries with chrome ore resources in the world today or countries with scarce resources are stepping up research on chrome ore beneficiation.
(1) Re-election: such as jigging, shaker, spiral chute, heavy medium cyclone, etc.
(2) Magnetic power selection: including high-strength field magnetic separation and high-voltage electric selection.
(3) Flotation and flocculation flotation.
(4) Joint election: such as re-election.
(5) Chemical beneficiation: It is difficult to treat extremely fine grains and choose chromium-poor ore.
In the above chrome ore beneficiation method, the re-election method is mainly used in production, and the shaker and the jig are often used for sorting. Sometimes re-election concentrates are re-selected with weak magnetic separation or strong magnetic separation to further increase the grade and ferrochrome ratio of chromium concentrate.
The chrome spinel contains ore which is relatively high in iron or densely symbiotic with magnetite. In the concentrate obtained after ore dressing, the chrome grade and the ferrochrome ratio are both low, which can be considered as an ingredient for the production of ferrochrome by fire, or Treated by hydrometallurgy. For example, sodium dichromate method, chromium hydroxide method, reduction rust method, chlorination roasting acid leaching or electrolysis method. The production practice of low-grade ferrochrome concentrate by hydrometallurgy.
Platinum deposits (platinum, palladium , rhodium , iridium , ruthenium and rhodium ), cobalt , titanium , vanadium , nickel and the like are often associated with chromium deposits. When the platinum content is greater than 0.2-0.4g/t, the cobalt content is greater than 0.02%, and the nickel content is greater than 0.2%, comprehensive recovery should be considered. Chromite ore in associated form, such as PGE sulfide, arsenic compound or sulfur arsenide state, can be recovered by flotation. Olivine and serpentine ore, can be considered comprehensive recovery, for the production of refractory materials, calcium magnesium phosphate fertilizer diabase or the like. In the shallow part of the ultrabasic rock mass, there is sometimes an amorphous magnesite that is caused by weathering and leaching, and it is also a good raw material for refractory materials.
In the late 1960s, China established small-scale plants such as Shangnan chrome ore in Shaanxi, Zunhua chrome ore in Hebei Province, and Miyun chrome ore in Beijing. Since the 1970s, the study of tin and mineral League in Inner Mongolia Ao Heeg pull chrome ore, Gansu Avenue Bhattacharjee chrome ore and chrome ore Tibet, Xinjiang and other places were. Due to lack of resources, the ore dressing of chrome ore in China has been in a backward situation. Only a few small-scale plants use a single re-election (shaker) to select chrome-poor ore. For example, Shangnan, Zunhua and Miyun concentrating plants use a shaker to treat chrome-poor ore with finer crystal grain size, which can be obtained from Cr2O34. Concentrates containing Cr 230%, -45% and recovery rate of 62% to 82% are sorted from % to 20% of the ore.
Recently, China has made some progress in the research of chrome ore beneficiation. For example, the relevant units have adopted stage grinding and spiral chute sorting for refractory ore in a certain area, so that the grade of chrome concentrate is increased from 22.4% to 35% of the original ore. It is 80.18%, and the easy-choice chromium-poor mine adopts the jigging and shaker combined sorting process, and the grade of chromium concentrate is increased from 19% of the original ore to 40%.
It is well known that in natural chrome ore, low-site chrome ore with a SIO2 content of less than 2% is almost non-existent and must be obtained by beneficiation and purification. Therefore, the study of refractory grade chrome ore beneficiation and silicon reduction process is of particular importance for the development of magnesium, aluminum and chromium series refractories.
The properties of chrome ore in the Salto Sea in Xinjiang and the Red Flag in Tibet are similar. The main mineral is chrome spinel, the content is about 85% to 90%, and the chromium mineral particle size is generally 1-5 mm and the minimum is 0.3-0.5 mm. The gangue minerals are mainly chlorite and serpentine. They are fine scaly aggregates and colloidal fibers distributed between chromium mineral grains and fissures. The maximum particle size is 0.15 mm × 0.075 mm, generally less than 0.008 mm. The nature of the ore indicates that the silicon-containing mineral is extremely finely embedded in the chrome ore and must be finely ground to dissociate the monomer. A single sorting process was used to sort the centrifugal concentrator by one grinding to a 0.3 mm one-second spiral chute, and a good sorting effect was obtained.
Xinjiang chrome ore: When the content of CrO3 is 33 65% and the content of SiO 2 is 6.01%, a low-silicon chrome concentrate with a Crz0 content of 37% and a so/content of 1.76% can be obtained.
Tibet chrome ore: When the content of Cr203 is 48.46%, and the content of SiO2 is 3.91%, the content of Cr 2 0 3 is 53.26%. High purity chromium concentrate with a Si0 2 content of 0.98%. The Xinjiang chrome ore has undergone continuous expansion tests above the tonnage level and obtained concentrates containing 7.25% Cr 2 O 3 and 1.8% SiO 2 .
The laboratory test conducted by the stage grinding process-stage jigging three-stage bed-casting process in Ganzi Avenue Erji chrome ore can obtain Cr 2 0 3 45.82% from the ore containing Cr 2 O 3 32.56%. The rate is 96.68% of the concentrate. Test uses a two stage grinding process shaker Inner XiMeng Heeg pull Ao chromium ore showed available containing Cr 2 O 3 4.18% from ore containing Cr 2 O 3 22.41%, the recovery of 77.45 % concentrate. The new direct steelmaking process of chromite ore furnace requires high-quality high-purity chrome concentrate. The grading deep selection of two types of chrome ore is carried out by a jigging shaker-centrifugal concentrator combination process, which can obtain high grade, large ratio of ferrochrome to harmful impurities. High-grade chromium concentrate with low content.
The original design process of the Don River Plant includes the following operations:
The ore grade 100~10 is graded by two sections of heavy medium (cylinder concentrator) with a medium density of 2.7-3.31 g/cm3. The medium ore of the heavy medium concentrator is crushed to 10-0mm and merged with the original ore 10-10mm level for storage; the 10~3 mm and 3-Omm grades are separately jigging and beneficiation; After ~0mm, use a spiral concentrator to sort. 0 5 ~ 0 mm slime is sorted with a shaker. On the basis of long-term research and commissioning, improvements and improvements were made in 1983: in order to improve the reliability of the jigging sorting operation, a second spare series was installed, which greatly reduced the time for the plant to be shut down due to the failure. The use of high-efficiency jigs improves the efficiency of jigging, especially in the 3 to 5 mm class. After the jigging mine is reground, the CB3-1500 (+1500 m) spiral concentrator is used instead of the +600mmm spiral concentrator. The selection rate of the middle mine. The high field strength magnetic separator was used to recover the 0.25 mm slime separated from the shaker and the spiral concentrator tailings. The process of the Don River plant has been improved. In 1983, the design indicators were met and exceeded in terms of production and quality. When the proportion of refractory ore-like ore in the ore is more than the usual ratio (20% to 25%) and reaches 30% -35% (up to 44%), the first stage of heavy media beneficiation must be used in order to enable the design process to Ensure that the chromium oxide in the concentrate reaches the specified level and reduces the loss of valuable components in the tailings.
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