Extraction and refining for Chromium metal

Chromium metal refining and extraction

Chromium metal refining and extraction is used in Chrome ore processing plant to recovery pirify chrome.

Chromium metal - Extraction and refining:

Pure chromium is produced either by the thermal reduction of Cr2O3 with aluminum or by the electrolysis of trivalent chromium solutions.

The aluminothermic process begins with the roasting of fine ore, soda, and lime in air at 1,100° C (2,000° F). This creates a calcine containing sodium chromate, which is leached from the insoluble gangue and then reduced and precipitated as Cr2O3. The Cr2O3 is blended with finely divided aluminum powder, charged to a refractory-lined container, and ignited. The combustion quickly generates temperatures in excess of 2,000° C (3,600° F), giving a clean separation of chromium from the slag. The purity of the metal, varying from 97 to 99 percent chromium, depends on the starting materials.

In the electrolytic process, milled high-carbon ferrochromium is leached by a mixture of reduced anolyte (electrolytic solution recycled from the anode side of the smelting cell), a chrome alum mother liquor based on a solution of ammonium sulfate recycled from a later stage in the process, and sulfuric acid. The resultant slurry is cooled, and silica and other undissolved solids are filtered from the solution. The iron forms crude ferrous ammonium sulfate crystals, which also are filtered out.

The mother liquor is then clarified in a filter press, and about 80 percent of the chromium is stripped by precipitation as ammonium chrome alum. The mother liquor is sent back to the leach circuit while the chrome alum crystals are dissolved in hot water and fed into the cathode portion of an electrolytic cell. The cell is divided by a diaphragm in order to prevent the chromic and sulfuric acids formed at the anode from mixing with the catholyte (cathode electrolyte).

With the passage of electric current from a lead anode to a thin stainless-steel cathode sheet, chromium is plated onto the cathode and, every 72 hours, is stripped from the sheet, sealed in stainless steel cans, and heated to 420° C (790° F) to remove water and hydrogen. This electrolytic chromium contains 0.5 percent oxygen, which is too high for some applications; combining it with carbon and heating the briquettes to 1,400° C (2,550° F) at 13 pascals lowers the oxygen content to 0.02 percent, resulting in a metal more than 99.9 percent pure.

Ferrochrome silicon - Extraction and refining:

If silica is added to the charge until its weight equals that of the ore, the smelting processes will yield what is known as ferrochrome silicon. Containing 38–42 percent silicon and less than 0.1 percent carbon, this alloy is used as a deoxidizer in the production of stainless steel and as an intermediate material in the production of low-carbon ferrochromium. Because of the greater energy required to reduce silica to silicon, the smelting of ferrochrome silicon consumes 7,600 kilowatt-hours per ton of product.

Chrome ore processing machine

SBM is a famous Chrome ore processing machines manufacturer in China, and offer types of machines for chrome ore extraction and refining plant, like crusher, grinding, washing machine and concentrate machine. SBM also design chrom ore plant process for chrome mineral recovery plant in South Africa, India, Kazakhstan, Zimbabwe, Finland, Iran, Brazil, USA, China, Oman, Pakistan, the Sudan, Malaysia, Turkey, Mozambique, Madagascar, Albania, Turkey, Philippines and New Caledonia.

Chrome ore mining

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