In all rare metals, the importance and scarcity of chrome ore and scarce are most obvious, which is at the top of "strategic metals". The chrome ore is mainly used in the production of stainless steel and various kinds of alloy steel in the form of ferroalloy (such as ferrochrome), which has the advantages of strong hardness, wear-resisting, heat-resisting and corrosion resistance.
At present, the common chrome extraction processes mainly include gravity separation, magnetic separation, electric separation, flotation, gravity-magnetic separation process. Below, let's take you to learn about each chromite ore processing process.
From the point of production practice, the gravity separation is still the main chrome extraction method in the world method now, which uses the loose stratification in the water medium. At present, the gravity separator used in the chromite ore processing includes the shaker table, jig, spiral chute and centrifugal separator.
It is worth noting that stage grinding and gravity separator, or the combination of various gravity separators can be used according to the chrome ore properties, thus further improving the grade and recovery of chrome concentrate.
Because the chromite has a weak magnetism, we can use the strong magnetic separator for chrome extraction. There are mainly the following two cases: one is in the weak magnetic field, remove the ore in the strong magnetic separation of minerals (main magnetite), improve the ratio of ferrochrome. Another is to separate the gangue minerals and recover chrome ore (weakly magnetic mineral) under the strong magnetic field. If necessary, the weak magnetic - strong magnetic separation process can also be used to effectively separate the ore and achieve the chrome extraction.
The electric concentration process is mainly used to separate chromium ore from silicate gangue by using the difference of electrical properties of minerals, such as conductivity, dielectric constant, etc. For the chrome ore, a few chrome can be used directly by the electrical concentration, most of them only use the electrical concentration process in the concentration process. The concentration process has a special effect on removing silicate minerals (such as quartz, etc.) from chrome. Therefore, after the separation of chrome, another stage of the electric concentration process can be added for cleaning, which not only further improves the grade of chrome concentrate, but also greatly reduces the content of silicon dioxide.
At present, we can use the flotation process to recover the chromite with fine grain size (-100um) after the gravity separation. The results show that Mg2+ and Ca2+ can inhibit the chromium ore, and the inhibition of Mg2+ is influenced by the type of anions in the slurry. Therefore, after knowing the cationic behavior in the pulp, we can choose the appropriate pulp PH value, reagents concentration, add the order of inhibitors and activators, achieve the separation of chromite and pyrite.
Sometimes, the single gravity separation method cannot recover the chrome concentrate effectively. At this time, the concentrate obtained by the gravity separation can be separated by weak magnetic separation or strong magnetic separation, further improving the grade of chrome concentrate and chromic oxide-ferrous oxide ratio.
For example, the 100-10mm grade of raw ore adopts two-stage dense media separation. The medium ore of the dense media separator is crushed to 10-0mm and then merged with the 10-0mm grade of raw ore for separation. The grades of 10-3mm and 3-0mm are sent to the jigging process. After the middling of the jigging process is ground to 0.5-0mm, the spiral concentrator is used for separation, and the shaker table is used for the separation of mineral mud (0.5-0mm). Then, the high-field magnetic separator is used to recover 0.25mm slime separated from the tailings of the shaker table and spiral separator, ensuring the content of chromium oxide in the concentrate and reduce the loss of valuable components in the tailings.
Here are the common five chrome extraction processes. For the rich ore with high chromium oxide content, single gravity separation or magnetic separation process can be adopted. For the chrome with low chromium oxide content, the combined process of gravity separation and magnetic separation usually gets a better index than the single process. Of course, the specific chrome extraction process should be determined comprehensively according to the nature of the chrome ore, the actual situation of the chromite ore processing plant, the investment budget, so as to ensure the ideal beneficiation benefits and economic benefits.
Chromium has a wide variety of applications in the modern world. Its major uses are in stainless steels and the plating of metals. Other important uses include alloy steel, heating elements, pigments, leather processing, catalysts, and refractories.
Of the chromite ore imported into the USA, the metallurgical industry consumed about 59 pct, the chemical industry consumed 21 pct, and the refractory industry consumed 20 pct. The average grade of the metallurgical chromite ore was 43.4 pct Cr2O3, with 52 pct of the ore having a chromium-to-iron ratio of 3:1 or over, 17.6 pct having a ratio between 2:1 and 3:1, and 30.4 pct having a ratio less than 2:1. Chemical-grade chromite ore generally ranged from 40 to 46 pct Cr2O3 with a chromium-to-iron ratio of 1.5:1 to 2:1. Refractory-grade chromite ores contained a minimum of 20 pct Al2O3 and more than 60 pct Al2O3 plus Cr2O3.
Primary chromium needs for all uses in the United States by the year 2000 are estimated to be nearly three times its present annual consumption (400,000 short tons), and world needs in the year 2000 are estimated to be nearly 4 times that of the United States. The world reserves are ample to meet all needs; however, U.S. resources are very small. In 1977, identified resources grading over 10 pct Cr2O3 in the United States contained about 2.8 million recoverable tons of Cr2O3 as concentrates. Over 90 pct of the concentrates would be in the chemical-grade classification. Additional resources of large, but undetermined, tonnage exist in low-grade ores that contain less than 10 pct Cr2O3.
With no substitute readily available, chromium is an indispensable ingredient in our industrialized society. Our complete dependence upon imported ores and the ever-present danger of disrupted supply lines make it necessary to explore every possibility to devise methods for utilizing the Nations limited resources in case of an emergency.
Many studies have been made on ores containing more than 15 pct Cr2O3, but little work has been done on the lower grade ores. The research described was undertaken on low-grade ores from a deposit near Auburn, Calif, and core samples from the Seiad Creek area in northern California.
Chemical analyses of the ores used for the research are shown in table 1. The calculated chromite heads in subsequent tables, although not in perfect agreement with head assays, show that the tests are within experimental error and the assay variations on the feed materials.
A petrographic examination of the Auburn ore showed that it contains major amounts of epidote, chlorite, and serpentine, with minor amounts of calcite, enstatite, chromite, magnetite, hematite, and olivine. Examination of the ores from the Seiad Creek area showed the following minerals and the estimated volume-percent of each constituent:
The chromite grains in both samples were essentially liberated from the gangue at 100 mesh, although chromite was still locked with magnetite particles as small as 400 mesh.Both samples also contained fibrous structured minerals that may present environmental and/or health problems in the event of commercial mining and/or processing.
Low-grade ore obtained from an open cut trench at a chromite deposit near Auburn, Calif., was treated in the laboratory using gravity-magnetic separation and flotation beneficiation techniques. Flotation using known methods, however, gave very poor results and will not be discussed further in this report. Tabling of the ore followed by upgrading the tabled chromite concentrate using magnetic separation to remove magnetite gave far superior results. The results and discussion of gravity-magnetic separation tests on the Auburn ore follow.
Approximately 150 pounds of ore were stage crushed with rolls to minus 35 mesh, then blended and sampled for screen analysis. The results of the screen analysis, given in table 2, show that 48.3 pct passed 100 mesh, the point of chromite liberation.
The minus 35-mesh stage crushed ore was slurried and tabled to produce a rougher concentrate. As shown in table 3, the rougher concentrate contained 83.6 pct of the Cr2O3 and assayed 8.9 pct Cr2O3. The rougher concentrate was split into two equal portions. One part was retabled to obtain a cleaner concentrate which was further treated by dry magnetic separation. The other portion was wet ground to minus 100-mesh and retabled. The cleaner concentrates produced by retabling were dried and magnetically separated.
A comparison of cleaner concentrates obtained by retabling the minus 35-mesh table rougher concentrate and the table rougher concentrate reground to minus 100 mesh is shown in tables 4-6. It will be noted that the cleaner concentrate produced from the rougher concentrate reground to minus 100 mesh assayed 33.4 pct with a recovery of 62.0 pct. This is a grade increase of 2.7 pct Cr2O3 over the corresponding cleaner concentrate produced from the minus 35-mesh rougher concentrate, but the increased grade is obtained at the expense of 1.1 pct less recovery based on the original ore feed. Essentially no change or advantage was noted by regrinding the rougher concentrate through 100 mesh before cleaning by retabling.
The cleaner concentrates obtained by retabling the minus 35-mesh and reground minus 100-mesh rougher concentrates were dried and treated by low-intensity magnetic separation. The results, given in table 5, show that the nonmagnetic fraction of the minus 35-mesh Auburn cleaner concentrate assayed 36.7 pct Cr2O3 with an overall recovery of 29.0 pct. A similar nonmagnetic fraction produced from the minus 100-mesh cleaner concentrate assayed 42.8 pct Cr2O3 with a recovery of 34.1 pct.
Although test results shown in tables 4-6 indicate no advantage in regrinding the rougher shaker table concentrate before cleaner tabling, regrinding did substantially improve the liberation of the chromite from magnetite grains. This is evidenced by a small increase in grade in the cleaner concentrate and a substantial increase in grade in the nonmagnetic fraction. Overall recovery in the minus 100-mesh nonmagnetic fraction also was improved.
A petrographic examination was conducted on the minus 100-mesh magnetic separation products to characterize the products and to determine if further grinding would improve liberation of the chromite. The nonmagnetic fraction of the cleaner concentrate consists of approximately 73 to 75 pct chromite, 15-17 pct silicates, and 8 to 10 pct magnetite by volume, along with traces of hematite. Much of the magnetite occurs as thin, discontinuous rims on the chromite. (See fig. 1.)
The magnetic fraction is primarily magnetite and chromite, which together compose 94 to 96 vol-pct of the sample; the remainder consists of silicates and hematite. Most of the chromite occurs in zoned grains with magnetite.The grains, in general, contain chromite cores and grade outwardly into magnetite. (See fig. 2.)
Magnetite frequently constitutes the greatest portion of the zoned grains. The compositional gradation from chromite to magnetite is not always continuous but frequently occurs in several discontinuous steps. In some instances, the change is very abrupt and the chromite is simply mantled by magnetite.
Chemical data were collected on a small number of grains in both the magnetic and nonmagnetic fractions by using the X-ray energy spectrometer on the scanning electron microscope. The points analyzed are identified by the numbers on figures 1 and 2. Semiquantitative weight-percent data were collected for four elements, namely Cr, Fe, Al, and Mg, and they are shown as part of the figures in the form of ratios, with the most abundant element being assigned a value of 1. As can be seen, the magnetite contains some chromium substituting for iron. Similarly, the chromite contains aluminum substituting for chromium and magnesium substituting for iron.
Six different size fractions from minus 100- through minus 400-mesh were separated from the magnetic fraction and examined with the metallographic microscope to help determine if increased grinding would significantly improve the concentration of chromite. Three of the fractions are shown in figures 3-5. As would be expected, a lower percentage of the chromite grains in the finer size fractions are zoned by magnetite. Even at minus 400 mesh, however, a significant percentage of the grains show noticeable zoning, as figure 5 illustrates. It is apparent that regrinding the magnetic concentrate would increase liberation of the chromite and could result in increased chromite in a nonmagnetic product.
Based on the dry-grinding-tabling-magnetic separation results, a larger wet grinding test was conducted to better simulate a commercial operation. Approximately 600 pounds of the Auburn ore were crushed to minus 3/8-inch size and used as feed to a rodmill-tabling circuit, as shown in figure 6. The mill discharge was passed over a 35-mesh screen with the undersize reporting as table feed, and the oversize was returned to the rodmill along with the middling table product. The minus 35-mesh table feed was about 75 pct minus 100 mesh. The high-grade fraction was dried and magnetically separated without further treatment, whereas the low-grade portion was reground to minus 100 mesh and retabled to produce a cleaner concentrate for dry magnetic separation. Tables 7-9 show that the high-grade rougher concentrate accounted for a recovery of 23.4 pct in a product assaying 37.0 pct Cr2O3. This was upgraded by dry magnetic separation to 48.3 pct Cr2O3, representing 12.5 pct of the Cr2O3 in the original feed.
The low-grade fraction, assaying 13.5 pct Cr2O3, was upgraded to 33.0 pct Cr2O3 by regrinding to minus 100 mesh and retabling. The resulting cleaner concentrate was dried and magnetically separated to produce a nonmagnetic concentrate assaying 43.3 pct Cr2O3, and representing a recovery of 23.9 pct of the original feed. These results are shown in tables 8-10. The middling table product obtained from retabling the reground low-grade fraction was added with fresh feed to the rodmill.
A summary of the results from the tabling and magnetic concentration of wet-ground Auburn ore is given in tables 11 and 12. The magnetic and nonmagnetic products are the combination of the minus 35 and minus 100-mesh magnetic separation products. As seen, 36.4 pct of the available Cr2O3 was recovered in a final nonmagnetic concentrate assaying 44.9 pct Cr2O3 with a Cr:Fe ratio of 1.6:1. This compares with the 34.1 pct recovered in a 42.8 pct-Cr2O3 nonmagnetic concentrate obtained from the dry-crushed feed material. The increased percentage of minus 100-mesh material from 48.3 pct in the dry-crushed feed to about 75 pct in the wet-ground feed resulted in about a 2-pct increase in grade and recovery in the final concentrate.
Because of the potential value of nickel as a byproduct when processing the ore, the products of table 11 were analyzed to determine if the nickel was concentrated with the chromite or magnetite above the 0.22 pct in the head.
Two samples of ore containing about 6 pct Cr2O3 were obtained from a core drilling operation in the Seiad Creek area of northern California. Two table concentration tests were made on each sample, one dry crushed to minus 35 mesh, and the other dry crushed to minus 100 mesh. In each test a rougher concentrate was recovered and then retabled. The results, given in tables 13 and 14, show that both samples responded in about the same manner. When tabling the minus 35-mesh material, a concentrate was produced from each ore sample that assayed about 47 pct Cr2O3 with a recovery of 60 pct, and a Cr:Fe ratio of 1.9:1 to 2.0:1. The concentrates obtained from both the minus 100- mesh feeds assayed about 50 pct Cr2O3, but showed a decrease in recovery from 60 to about 50 pct with no change in the Cr:Fe ratio. The nickel concentrations remained nearly constant (about 0.2 pct) in all products.
The combination of tabling and magnetic separation of a 2.5-pct-Cr2O3 ore from Auburn, Calif., resulted in a concentrate containing about 45 pct Cr2O3 with a chromium-to-iron ratio of 1.6:1, a product well suited to chemical use. The cleaner concentrate obtained by tabling the 5- and 6-pct-Cr2O3 ores from the Seiad Creek area in northern California contained from 47 to 49 pct Cr2O3 with a chromium-to-iron ratio of 1.9:1 to 2.0:1. The recoveries from both these ores were low, but the concentrates are suitable for metallurgical and/or chemical use and the grades compare favorably with those of imported chromite.
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The gold shaker table is a flow film separation equipment, that usually used to separate the gold particle grains from the ore material in the gold processing plant. Shaking table concentrator is developed from the early stationary and movable chute box, from percussion shaking table ( used in the coal mining industry) to the wilfley table and mineral processing eccentric rod shaker table, various type of gravity table separators have been developed and applied, especially in the recovery process of some precious metal like gold. Contact us to get the latest shaker table price.
Capacity: 0.1-2tph Feeding size: 0-2mm Applications: Gold, Tin, Chrome, Tantalum-niobium, Tungsten, Iron, Manganese, Nonferrous metal ore, and so on. Introduction: Gold shaker washing table can obtain the fine-grained materials, and separate the high-grade concentrate, taillights and intermediate mineral products during once processing. According to the different grain size of the ore material, it can be divided into coarse sand (2 - 0.074mm), fine sand (0.5 - 0.074mm), and ore slurry (0.074 - 0.02mm), the suited gold separate machine is varied with the material particle size, the main differences among them are the shaking table surface sluice, height, angle and so on. Main parts: table head, motor drive, stand, working bed, support frame, water tank, feed chute, angle adjuster device, spring, etc.
Types of shaking table: 1. Shake table for sale classified by uses: ore sand, ore slurry, mineral processing, coal dressing. 2. Classified by structure ( table head, surface, supporting frame ): 6-S shaker table, Gemini table, CC-2 gold wash table, spring concentrating table, centrifugal table, rp 4 shaker table, and so on shaking table mineral separation. 3. Classified by deck: single deck shaker table, the multideck table has double decks, three decks, four decks, six decks, and more.
Working principle of the shaker table: As a gravity separator machine, the shaking table separates the minerals mainly dependent on their differences of gravity, density, shape, etc, in addition, the water flow speed, slurry density, surface angle and so on variables also matters. The target mineral grains, from fine to coarse and light to heavy, can be classified by weight. The shaking table concentrator not only can be an independent beneficiation machine, but also connect with jig machine, flotation, magnetic separator, centrifuge concentrator, spiral concentrator, belt conveyor and so on.
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The principle of chrome ore mining process is to maximize the recovery rate of chrome and the associated heavy minerals from Ganges firstly, and then separate chrome ore from the associated heavy minerals by joint mining solutions such as gravity separation, magnetic separation, etc.
The laterite nickel ore is complex in composition and can be roughly divided into two types: limonite type and silicon magnesium-nickel type. The main elements are nickel, cobalt and manganese. The laterite mining method generally uses open-pit mining. The ore body generally does not require rock drilling or blasting. Nickel ore processing plant can directly use the excavator to shovel the ore. The thinner ore layers are first collected by the bulldozer and then shovel. nickel mining is divide into copper-nickel mining and extraction of nickel from sulphide ore. Below the cover of the Ramu laterite nickel deposit in Papua New Guinea, there are yellow limonite deposits, residual layers, gravel-bearing residual rocks and pure peridotite bedrock; under the Philippines mining Nonoc laterite ore cover are limonite Layer, transition layer, residual ore layer and bedrock; Cameroon red earth cobalt-nickel ore is red soil layer, breccia, iron-aluminum and serpentine bedrock. In general, the laterite ore mainly contains a gravel layer, and is often accompanied by columnar rock phenomenon with incomplete weathering. Because columnar rocks often have high-grade ore and the blockiness and hardness are relatively large, from the perspective of mineral processing. It is said that it is necessary to use crushing equipment to extract nickel from its ore.
The extraction of nickel process generally consists of crushing, sieving, washing, re-selection, grinding, and slurry concentration, or the nickel leaching method. The target element nickel distribution varies with the nature of the ore, mostly contained in fine-grained grades. For example, the nickel minerals of the Ramu laterite mine in Papua New Guinea are mainly enriched in fine mud of -53 m. There are uncommon, such as Cameroon cobalt nickel manganese laterite ore, the nickel are mainly concentrated in +0. In the grain size above 3mm, the Philippine BNML nickel ore limonite + ore nickel grade above 50mm 2. 89%, the coarser the grade of ore, the higher the grade of nickel.
Laterite nickel ore is often accompanied by a columnar rock with incomplete weathering. The block size may exceed 1m. If you dont crush them, only use the original ore bin to control the ore size. The rock is easily stuck in the sieve hole, affects the normal supply during the nickel extraction process. Therefore, it is recommended that the laterite mine should be crushed better before washing. Conventional stone crushers such as rotary crusher, jaw crusher, impact crusher, hammer crusher, cone crusher and roller crushers, all have a common disadvantage that they cannot effectively handle materials with high mud content, high water content and high viscosity. The double roller crusher can effectively overcome the shortcomings of conventional crusher. the working principle of double roller crusher is that the shearing force acts directly on the ore material through the high-torque, low-speed transmission system, so that the force is along the weak and fragile parts of the material. Produces a huge crushing force to break it, forming a unique crushing particle size control technology. When the crusher is working, the material can be discharged into the upper part of the whole machine. The size of the feed port is larger than that of any crusher, and it is not easy to cause the blockage. The discharge port is also very large, and almost the entire lower part of the equipment can be discharged. product. The movement of the double-toothed tooth causes the material to be broken and can be forcibly discharged, so it is especially suitable for viscous materials and materials with high water content, and the discharge opening is not blocked. The double-roller screening crusher production plant mainly in British MMD company and Sandvik company.
The washing equipment used in the nickel mining process mainly includes a gold trommel scrubber, a spiral washing machine and a stirring scrubbing tank. The Nonoc laterite nickel mine washing system is composed of a cylindrical gold trommel washing machine and two spiral washing machines. The Australian laterite nickel ore is washed by a trommel scrubber. The specifications of the trommel scrubber are: 5m 11. 9m for limonite, 4m 7. 4m is used for residual ore. The grit of the first-stage hydrocyclone of laterite mine is fed into the mixing scrubbing tank and then graded into the second-stage hydrocyclone. The Papua New Guinea laterite nickel mine adopts a combined washing method of a cylinder washing machine and a spiral washer machine. The gold trommel washing machine has a specification of 3m 10m, and the tank type washing machine has a specification of LW36 35. Generally speaking, after a section of crushing, the cylinder size of the cylinder is used to feed the ore 300mm; the size of the log washing machine is 50mm. For most of the laterite nickel ore, the nickel-cobalt is mainly rich in In the 3mm grain class, the grain size above +3mm is discarded as waste rock. For example, 3mm ~ 50mm of laterite mine is recycled by sanding of the log washing machine, and the material of +50mm is thrown through the cylinder of the cylinder washing machine. Waste. But there are also uncommon such as Cameroon cobalt nickel manganese laterite ore, its useful mineral cobalt nickel is mainly rich in + 0. 3mm or more, 0. In the 3mm range, the slime is mainly thrown away as tailings. For this ore type laterite nickel ore, the use of cylindrical washing machine and trough washing machine cannot effectively remove 0. 3mm fine-grain grade slime, this red earth mine washing operation itself does not produce tailings, its purpose is mainly to scrub the ore and the slime, fully stir and de-sludge through a cyclone or hydraulic classification equipment. However, the washing and washing equipment may consider the use of the stirring scrubbing tank, but the washing condition of the stirring scrubbing tank and the energy consumption of the stirring should be fully considered according to the stirring scrubbing test. Extraction of nickel research has a very positive effect on the nickel mining process, extraction of manganese, extraction tin and other mining minerals. Nickel laterite processing is always upgrading. JXSC provides a full of nickel ore mining equipment for nickel mining companies around the world, contact us to know the mining use stone crusher machine price, washing plant price and so on.
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