CN1542148A

CN1542148A - Method for producing metallic chromium

Info

Publication number: CN1542148A
Application number: CNA2003101035103A
Authority: CN
Inventors: 蒋兴东; 周瑞; 关振波; 王英礼
Original assignee: Shenhong Industry Co Ltd Jinzhou City
Current assignee: Linghai Shenhong chromium Industry Co. Ltd.
Priority date: 2003-11-05
Filing date: 2003-11-05
Publication date: 2004-11-03
Anticipated expiration: 2023-11-05
Also published as: CN1257990C

Abstract

The present invention is carbon reducing process of producing metal chromium and can prepare metal chromium product with Cr content higher than 99 %, C content less than 0.02 % and O content less than 0.5 %.

Description

Method for producing chromium metal

Technical Field

The invention relates to a method for producing metallic chromium by reducing chromium oxide with carbon. The Cr content of the metal chromium produced by the method is more than 99.0 percent, the C content is less than 0.02 percent, and the oxygen content is less than 0.5 percent.

Background

The chromium metal is widely applied to the fields of metallurgy, chemical engineering, aerospace and refractory materials. The current production methods of metallic chromium include thermit, electrolysis, and carbon reduction.

The aluminothermic process consumes a large amount of expensive aluminum powder, and simultaneously, a large amount of impurities such as Fe, Si, Al and the like are introduced into the product, so that the recovery rate of the product is not high and is usually not more than 88%.

The electrolysis method has the advantages of high product purity and easy breakage, but because the oxygen content is high in the chromium electrolysis process, a corresponding high-temperature hydrogen deoxidation furnace needs to be established to obtain a high-quality product.

And cheap carbon powder is adopted to replace aluminum powder to reduce chromium oxide, so that the introduction of impurities is greatly reduced, the recovery rate of the product can be improved to more than 98%, and the production cost is reduced. The reactions for carbon reduction of chromium oxide production are as follows:

US2833645A discloses a method for producing chromium metal by carbon reduction of chromium oxide, which comprises forming a compact, and collectingA two-step production mode is adopted, after the first step of sintering, the reaction materials are discharged from the furnace for secondary grinding, mixing and balling treatment, and then secondary sintering is carried out, wherein the apparent density of the small balls formed in the molding process is 5-5.5g/cm³The temperature during the sintering process is controlled to be 1100-1600 ℃, preferably 1250-1400 ℃, but the product can not simultaneously satisfy the conditions that the Cr content is more than 99.0%, the C content is less than 0.02% and the oxygen content is less than 0.5%.

Japanese patent JP-A No. 6-212306 and JP-A No. 54-4807 also adopt a method of carbon reduction of chromium oxide to produce metallic chromium, but the first vacuum treatment is followed by a second vacuum reduction treatment by adding carbon powder again. For example, in JP Hei 6-212306A, the mixture is pressed into blocks, the length of the short side is 20-100mm, the material stacking void degree is 0.3-0.8, and the metallic chromium is produced by two-step reduction, namely, the metallic chromium is firstly reduced by vacuum heating and one-step reduction, crushed and added with carbon powder and then reduced by secondary vacuum heating. The process is complicated, the production time is long, the cost is high, and the content of C in the product metal chromium is not less than 0.02%.

Japanese patent JP-A-7-216474 discloses the production of metallic chromium by carbon reduction of chromium oxide, also by two-step reduction, but with hydrogen being introduced into the reactor during the first step of the process. This process requires a large amount of high purity hydrogen, resulting in high production costs.

The invention aims to overcome the problems in the production of carbon-reduced chromium oxide and provides a treatment method which has simple process and low cost and can produce high-purity chromium metal.

Disclosure of Invention

The invention provides a method for producing metal chromium by reducing chromium oxide with carbon powder, which comprises the steps of adding carbon powder, preferably 99.5-100.2%, into 99-101% of the oxygen content in the chromium oxide, grinding, mixing, briquetting, forming, and then carrying out reduction treatment in a vacuum furnace, wherein the reduction process in the furnace is divided into two stages, the first stage controls the vacuum degree in the vacuum furnace to be 200-plus-300 Pa, the temperature is increased to 1460-plus-1600 ℃, preferably 1475-plus-1520 ℃, the heat preservation treatment is carried out for 3-10 hours, the vacuum is simultaneously pumped in the heat preservation process, when the vacuum degree reaches 200Pa, the reduction treatment enters the second stage, the temperature in the furnace is reduced to 1400-plus-1450 ℃, preferably 1420-plus-1450 ℃, the vacuum degree is controlled to be 5-30Pa, the heat preservation treatment is carried out for 3-10 hours, and the metal chromium product is.

The chromium oxide used preferably has a purity of greater than 99% and a particle size of 325 mesh to 1000 mesh.

The carbon content in the carbon powder is preferably more than 99%, the total content of Fe, Si and Al is less than 0.1%, and the granularity is less than 325 meshes.

The chromium oxide is mixed with carbon powder and then put into a ball mill for grinding and mixing, wherein the grinding and mixing time is 0.5-3 hours. In order to prevent the introduction of impurities such as Fe, Si and the like, agate balls or alumina corundum balls are selected as grinding media, and the granularity is 5-50 mm.

The materials after grinding and mixing can be added with a binder for briquetting and can also be directly briquetted, and the density of the briquettes is generally 2.0-4.0g/cm³。

The quality of the metallic chromium produced by the invention reaches the quality level of JCr99B in the state GB3211-87, the content of Cr is more than 99.0%, the content of C is less than 0.02%, and the content of oxygen is less than 0.5%. The product can be directly sold or made into powder for sale. Meanwhile, the product is more suitable for further vacuum treatment to produce high-purity metal chromium with the Cr content of more than 99.6 percent, the C content of less than 0.01 percent, the oxygen content of less than 0.05 percent and the Al content of less than 0.05 percent.

Detailed Description

Example 1:

selecting Cr₂O₃100kg of chromium oxide with the content of more than 99.50 percent and the granularity of 325 meshes is added into 23.7kg of carbon powder (added according to the theoretical amount of 99.8 percent) with the carbon content of 99.2 percent and the total content of Fe, Siand Al of less than 0.1 percent, the mixture is simply mixed and then added into a ball mill with the diameter of 1000mm and 150kg of 5-50mm agate balls, the mixture is ground and mixed for 2 hours, and then the mixture is pressed into blocks, the diameter of the blocks is 150mm, and the density is 2.95g/cm³。

Putting the material block into a vacuum furnace, vacuumizing to 250Pa, heating to 1500 ℃, preserving heat for 6 hours until the vacuum degree reaches 200Pa, cooling to 1430 ℃, preserving heat for 5 hours until the vacuum degree reaches 20Pa, cooling to 200 ℃ and discharging.

The main chemical components of the product are determined as follows:

Cr：99.5％，O：0.35％，C：0.017％，Al：0.02％

example 2:

selecting Cr₂O₃100kg of chromium oxide with the content of more than 99.70 percent and the granularity of 325 meshes is added into 23.8kg of carbon powder (added according to the theoretical amount of 100.2 percent) with the carbon content of 99.4 percent and the total content of Fe, Si and Al of less than 0.1 percent, the mixture is simply mixed and then added into a ball mill with the diameter of 1000mm and filled with 150kg of 5-50mm agate balls, the mixture is ground and mixed for 2 hours and then is pressed into blocks, the diameter of the blocks is 150mm, and the density is 2.95g/m³。

Putting the material block into a vacuum furnace, vacuumizing to 200Pa, heating to 1520 ℃, preserving heat for 6 hours, reducing the vacuum degree to 200Pa, cooling to 1450 ℃, preserving heat for 5 hours, reducing the vacuum degree to 5Pa, and discharging from the furnace after the temperature is reduced to 200 ℃.

The main chemical components of the product are determined as follows:

Cr：99.6％，O：0.14％，C：0.02％，Al：0.015％

example 3:

selecting Cr₂O₃100kg of chromium oxide with a content of more than 99.70% and a particle size of 325 mesh, 23.60kg of carbon powder (added in a theoretical amount of 99.5%) with a carbon content of 99.4% and a total content of Fe, Si and Al of less than 0.1% were added, and the mixed briquettes were the same as in example 1.

Putting the material block into a vacuum furnace, vacuumizing to 200Pa, heating to 1550 ℃, preserving heat for 6 hours and 10 minutes, cooling to 1400 ℃ when the vacuum degree reaches 200Pa, preserving heat for 5 hours and 30 minutes when the vacuum degree reaches 30Pa, cooling to 200 ℃ and discharging.

The main chemical components of the product are determined as follows:

Cr：99.15％，O：0.42％，C：0.02％，Al：0.02％。

Claims

1. a method for producing metal chromium by reducing chromium oxide with carbon powder comprises the steps of adding carbon powder according to 99% -101% of oxygen content in chromium oxide, grinding and mixing materials, briquetting, and then carrying out reduction treatment in a vacuum furnace, wherein the reduction process in the vacuum furnace is divided into two stages, the first stage controls the vacuum degree in the vacuum furnace to be 200-300Pa, the temperature is increased to 1460-1600 ℃, the heat preservation treatment is carried out for 3-10 hours, the vacuum is simultaneously pumped in the heat preservation process, when the vacuum degree reaches 200Pa, the reduction enters the second stage, the temperature in the furnace is reduced to 1400-1450 ℃, the vacuum degree is controlled to be 5-30Pa, the heat preservation treatment is carried out for 3-10 hours, and the metal chromium product is obtained after cooling and discharging from the furnace.

2. The method of claim 1, wherein: carbon powder is added according to 99.5 to 100.2 percent of the oxygen content in the chromium oxide.

3. The method according to claim 1 or 2, characterized in that: the purity of the chromium oxide is more than 99 percent, and the granularity is 325 meshes to 1000 meshes.

4. The method according to claim 1 or 2, characterized in that: the carbon content in the carbon powder is more than 99 percent, the total content of Fe, Si and Al is less than 0.1 percent, and the granularity is less than 325 meshes.

5. The method according to claim 1 or 2, characterized in that: the chromium oxide is mixed with carbon powder and then put into a ball mill for grinding and mixing for 0.5 to 3 hours, and the grinding medium is agate balls or alumina corundum balls.

6. The method of claim 5, wherein: the granularity of the agate ball or the alumina corundum ball is 5-50 mm.

7. The method according to claim 1 or 2, characterized in that: the first stage is heated to 1475-1520 deg.C, and the second stage is cooled to 1420-1450 deg.C.

8. The method according to claim 1 or 2, characterized in that: the Cr content in the prepared metal chromium is more than 99.0 percent, the C content is less than 0.02 percent, and the oxygen content is less than 0.5 percent.