The Beginner’s Guide about Chrome Ore Processing

( Chrome ore processing plant with 300td in Shiraz Iran )

In recent years, the application of chrome ore sand in the foundry industry has increased due to the increase in the world price of grant sand. Below we will focus on the beneficiation of chrome ore by presenting information on the resource overview of chrome ore, ore types, ore characteristics, and beneficiation process and equipment.

Since the discovery of chromium in 1797, more than 50 types of chromium-bearing minerals have been found in nature to date, and chromium spinel-like minerals are the only source of chromium for industrial use. Chromium is mainly used in many industries such as metallurgical products, refractory materials, chemical industry and casting.

Chromium has been one of the most used metals in modern industry. Because there are few countries with available resources, low degree of substitutable materials, and expanding military applications, chromium is known as an important strategic resource, and the United States alone reserves more than 8 million t of chromite.

In the metallurgical industry, the general requirements of ferrochrome ore grade of Cr2O3-38% ~ 45%, Cr/Fe ≥ 2 above, mainly used to produce ferrochrome alloys and chromium metal. Ferrochrome alloy is used as steel additive to produce a variety of high-strength, corrosion-resistant, oxidation-resistant, high-temperature-resistant special steels, such as stainless steel, acid-resistant steel, heat-resistant steel, ball bearing steel, spring steel, tool steel, etc.

Chromium metal is mainly used for smelting special alloys with elements such as drill, nickel and tungsten. In turn, it is used in aviation, astronautics, gas vehicles, shipbuilding, military and other industrial sectors.

In the refractory industry, the general requirement of chromite ore grade of Cr2O3-30% to 35%, SiO2 less than 5% , used to manufacture chrome bricks. Chromium-magnesium bricks and fully synthetic advanced refractories, as well as other special refractories, etc., widely used in flat furnaces. Induction furnace, metallurgical converter and cement industry on the rotary furnace household lining, etc..

In the chemical industry, the general requirements of chromite grade of Cr2O3 ≥ 30%, Cr/Fe ≥ 2, mainly used to produce sodium dichromate, and then make its also chromium compounds, used in pigments, textiles, electroplating, tanning and other industries, but also to make catalysts.

World chromite consumption of 76% for the metallurgical industry; 13% for refractory materials; 11% for the chemical industry. Chromite is the basic raw material for the production of stainless steel, the development of stainless steel is a major trend in the world of steel production, is bound to usher in a major development.

(1) According to the content of chromium spinel can be divided into dense massive, dense dipping, medium diffuse and sparse dipping ore, etc.

(2) According to the chemical composition of chromite ore is divided into: high chromite chromite ore, containing Cr2O3>46%, Cr/Fe >2; high iron chromite ore, containing Cr2O3-40% ~46%, Cr/Fe > 1.5~2; high aluminum chromite ore Al2O3>20%, Cr2O3+ Al2O3 >60%.

(3) According to the Cr2O3 grade of chrome ore and ferrochrome score as follows: Cr2O3 of chrome-rich ore ≥ 32%, Cr2O3/( Fe0) > 2.5; Cr2O3 of chrome-poor ore-12% ~32%. China's native chrome-rich ores allow impurity content of; SiO2 ≤ 8% , P ≤ 0.07% , S < 0.05%. And alluvial chrome ore requires Cr2O3 ≥ 3%, regardless of rich ore and poor ore.

(4) According to the industrial use of chromium ore classification: can be divided into metallurgical grade, refractory grade, chemical grade and cast stone grade. Different industrial use of chrome ore, its industrial requirements are also different.

The industrial minerals of chromium all belong to the chromium spinel subgroup minerals with Cr2O3 content of 18% to 62%. Chromium minerals with industrial value have Cr2O3 above 30%. Such as magnesia chromite (Mg, Fe) Cr2O4, Cr2O3-50% ~60% , aluminum chromite (Mg, Fe)( Cr, Al)2O4, Cr2O3-32% ~50% ; chromium-rich spinel (Mg, Fe)( Al, Cr)2O4; Cr2O3-32% ~38%. Chromite [ FeCr2O3] contains Cr2O3-47% ~60%.

Chromium, magnesium and iron in chromite are completely homogeneous instead, and are divided into four subspecies of magnesia-chromite, ferromagnesia-chromite, magnesia-iron-chromite and ferrochromite. Among them, magnesia chromite and ferrochromite are extremely rare. Hardness 5.5 ~7.5, density 4.0 ~4.8g/cm', weak magnetic.

Aluminous chromite is semi-metallic luster hardness >5.5, density 4.448 ~4.19g/cm'. High iron chromite is black, metallic luster, hardness 5.5, density 4.73g/cm'. Chromium-rich spinel is black, asphaltic to metallic luster, weakly magnetic, hardness 5.5~7.5, density 4.0~5.1g/cm'.

The useful minerals in chromite ore are mainly chromium spinel-like minerals, followed by magnetite, a small amount of hematite, pyrite, chalcopyrite, magnetic pyrite and trace platinum group minerals.

Vein minerals are mainly serpentine, chlorite, carbonate minerals, followed by chromium mica, talc, vermiculite, tremolite, etc.

Chrome spinel grain size is 0.01 ~ 0.1mm. magnetite grain size 0.02 ~ 0.04mm. platinum group minerals grain size 0.005 ~ 0.015mm. pyrite, chalcopyrite grain size 0.05mm.

The selectivity of chromite ore mainly depends on the grade, purity, diffuse particle size, composition and quantity of co-occurring vein minerals of chromite ore. In addition chromite ore is denser and has weak magnetic properties.

The most important beneficiation method of chromite ore is re-election, which is based on the specific gravity difference between chromite ore and waste rock, the specific gravity of chromite ore is large, and the specific gravity of its associated veinstone is small, so the principle of gravity separation and equipment can be used for separation. Chrome ore re-election equipment mainly refers to jigger and shaker.

Chromite ore is generally embedded in the size of the medium and fine particles, chromite production line equipment also contains most of the crusher, rod mill, etc. The determination of chromite re-election equipment needs to be based on the specific chromite ore embedded in the size.

If the embedded size is coarse, most of the monomer dissociation can be achieved after grinding by rod mill, then the rod mill-jig process is selected. If the embedded size is fine, then the ball mill needs to be used to grind the ore, and the grinding product will enter the strong magnetic separation process or flotation process after reaching the monomer dissociation.

Chrome ore production process is composed of a series of continuous operations. The nature of the operations can be divided into three parts: preparation operations, separation operations, and product handling operations.

(1) Preparatory operations: including a: crushing and grinding for the dissociation of chromite ore monomer; b: washing and desliming of chromite ore with more colloid or clay; c: classification of the incoming ore by size using screening or hydraulic classification methods.

Chromium ore is graded and then separately selected, which is conducive to selecting operating conditions and improving sorting efficiency.

(2) Sorting operation: It is the main part of the sorting of chrome ore. The sorting process is simple and complex, simple by unit operations, such as heavy media sorting.

(3) Product processing operations: mainly refers to chrome ore concentrate dewatering, tailings transport and stockpiling

Chrome ore beneficiation equipment mainly includes the following series of equipment.

1. Jaw Crusher

Jaw Crusher is a crusher equipment with high production capacity, large crushing ratio and high crushing efficiency, mainly used for coarse crushing of chrome ore.

Ball Mill: Ball mill is the main equipment for regrinding after crushing, after coarse crushing, the feeder will give the chrome ore to the ball mill for grinding.

2. Spiral Classifier

The spiral classifier is an equipment for classifying solid particles with the help of different settling speed in the ore pulp. It is responsible for cleaning and classifying the ore mixture, and the graded ore is fed to the jigger or shaker for washing.

3.  Jig

Jig is an energy-saving re-election equipment developed and improved on the basis of the traditional jigger according to the law of layering of jig bed theory, and its jig pulsation curve is a sawtooth waveform making the rising water flow faster than the falling water flow.

4. Shaking table

The working principle of shaking table is to use the asymmetric reciprocating motion of the table to achieve the separation of light and heavy minerals.

5. Spiral chute

Mineral processing spiral chute is mainly used for separating iron, tin, tungsten, tantalum, niobium, gold, coal, monazite, rutile, zircon and other metallic and non-metallic minerals with sufficient specific gravity difference of 0.3-0.02 mm fine grains.

This paper gives us a brief understanding of chrome ore by describing its resource overview and utilization, ore types, mineral composition and physical properties, and finally describes the chrome ore beneficiation process and beneficiation equipment, but in the actual beneficiation application, we need to combine specific ore properties and other conditions for the specific design of the beneficiation plant. Welcome to click chat button to learn more about chrome ore beneficiation.