WO2013029456A1

WO2013029456A1 - Two-step reduction method for reutilization of iron scale of stainless steel

Info

Publication number: WO2013029456A1
Application number: PCT/CN2012/079635
Authority: WO
Inventors: 顾卫东
Original assignee: 威喜有限公司
Priority date: 2011-08-30
Filing date: 2012-08-03
Publication date: 2013-03-07
Also published as: CN102337408A; CN102337408B

Abstract

A two-step reduction method for reutilization of iron scale of stainless steel, comprising: subjecting stacked iron scale powder of stainless steel to sieving, mixing, and compacting and filling the powder into cans, delivering to a tunnel furnace for calcination and cooling, and then delivering to a lined electroslag furnace for refinement, wherein the lined electroslag furnace uses graphite electrodes, uses graphite carbon bricks as furnace lining, and uses electroslag composed of CaO and CaF₂. The process is effective to recover such precious metals as chromium and nickel in addition to iron. Moreover, the process has advantages such as high availability of raw materials, high throughput, controllable components, simple and reliable operation, low power consumption and low overall cost.

Description

Stainless steel oxide scale regeneration using two-step reduction method

Technical field

The invention relates to the technical field of metal scrap recycling, in particular to a two-step reduction method for recycling stainless steel iron oxide skin, which is suitable for recovering chromium-nickel precious metals from stainless steel iron oxide scale.

Background technique

In order to recover metals such as Fe, Cr, Ni, Cu, Mn in stainless steel scales and reduce environmental pollution, the prior art is looking for the best treatment method. So far, the most representative method for recycling stainless steel oxide scales is electric furnace. Law and saying

Two types of blast furnace method.

The electric furnace method is divided into two types: an electric arc furnace method and a submerged arc furnace method: the electric arc furnace method is to put a stainless steel oxide scale with other furnace materials in the book.

The smelting process is directly added to the furnace, and after the melting, a reducing agent is added to reduce the oxide, thereby obtaining an iron alloy having a high chromium-nickel content. The biggest disadvantage of the electric arc furnace method is: Since the pre-reduced iron sheet is light, it is basically floating on the slag surface after being added to the electric arc furnace, and it is difficult to enter the molten steel in a short time. The reducing agent used in the electric arc furnace is generally ferrosilicon, which is high in cost, and the method can only partially recover Fe in the stainless steel oxide scale, and cannot recover Cr and Mn.

The submerged arc furnace method is to add stainless steel oxide scale together with other ores into the furnace and reduce it with carbon. The reaction mechanism is basically the same as that of the arc furnace. Because the ore furnace is heated by electroslag, the power consumption is high, and the amount of slag is large, the yield of chromium in the stainless steel oxide scale is not high, the cost is large, and a large amount of chromium oxide residue remains in the slag, and the electric arc furnace Like the law, precious resources such as chromium and nickel cannot be reasonably recycled.

The blast furnace method is that the stainless steel oxide scale is mixed with other iron ore fines and sintered, and then used as a sintered ore to be melted into a blast furnace, and finally used as molten iron. Since the temperature of the blast furnace tapping is about 1400 ° C, the reaction temperature in the furnace is about 1500 ° C.

The reduction temperature of Cr ₂ 0 ₃ is 1600-1700 °C. Therefore, in order to reduce chromium oxide to metal in the blast furnace, it is necessary to increase the temperature inside the furnace, increase the consumption of coke, increase the cost, and easily melt the blast furnace. Wall, shorten the furnace age. At present, the use of stainless steel oxide scale in the blast furnace generally only recovers Fe therein, the temperature in the furnace is controlled at about 1500 ° C, and Cr and Mn are substantially not recovered.

In summary, the traditional electric furnace method and blast furnace method cannot effectively recycle the chromium metal of stainless steel oxide scale, which is a waste of valuable resources. At the same time, chromium acts as an oxide and remains in the slag, causing environmental pollution.

Summary of the invention

The object of the present invention is to provide a stainless steel scale regeneration and two-step reduction method in view of the problem that the existing stainless steel oxide scale recycling process cannot effectively reduce precious metals such as chromium and nickel. The method not only effectively recovers the iron of the stainless steel oxide scale, but also effectively recovers valuable metals such as chromium and nickel. The task of the present invention is achieved as follows: A stainless steel oxide scale regeneration using a two-step reduction method, the process of which is as follows:

1. Raw material screening and mixing

The pulverized stainless steel oxide scale raw material containing Fe 50%, Cr 5%, Mn^6% Ni^0.4% P 0.06%, S 0.06% (% by weight) under 3 mm is passed through a cylindrical sieve and vibrated After sieving, remove the impurities and heat the powder to less than 1% of water, then send it to the mixing chamber to add water glass, coke powder, lime powder and stainless steel iron oxide powder.

2. Crimp and canning

The mixed stainless steel iron oxide powder is placed on a briquetting machine for briquetting, and then the compact is placed in a calcination tank.

3. Calcination and cooling

The roasting tank with the briquetting body is capped and placed on the tunnel trolley to enter the tunnel kiln. In the tunnel kiln, the preheating drying section is gradually raised from room temperature to 900 °C, and then enters 950~1180 °C/ The 20-hour high-temperature roasting section is calcined, and finally enters the cooling section and is gradually cooled to 200~300 °C, and then the tunnel kiln is semi-finished.

4. Semi-finished product crushing, magnetic separation and briquetting

After the semi-finished product is crushed and magnetically selected, it is pressed by a briquetting machine into a cold compact having a density of about 4.5 g/cm 3 .

5. Melting and purifying in a lining furnace

The cold briquetting block is sent to the slag electroslag furnace for slag washing, and the lining electric slag furnace adopts continuous operation mode, and the lining refractory material is one of semi-graphite carbon brick, graphite carbon brick or silicon carbide combined with silicon carbide brick. For refractory bricks, the slag used is composed of CaO and CaF. The ratio of CaO:CaF is 1.22~1.86, and the thickness of lining electroslag slag is controlled between 300~400mm. Coke is added as usual during the slag washing process. The SiC reducing agent sufficiently reduces the unreduced metal oxide in the semi-finished product.

6. Casting, pouring

When the composition of the above molten steel meets the requirements of the following table, the tapping water should be accurately controlled to control the amount of retained steel. The retained steel is controlled at 50 to 100 mm and poured into a steel ingot mold for cooling.

Finished chrome-nickel iron quality indicator

The above method can also be further improved by the following measures:

The inner refractory material with the lining slag furnace is preferably made of graphite carbon brick, which has high temperature resistance and low loss.

In the slag system, 5 to 10% of A12O3, which accounts for the weight of the slag system, can be appropriately added, so that the slag system has a high electrical resistivity, which is advantageous for improving electrical efficiency and reducing specific power consumption. The invention is actually a two-step reduction method of tunnel kiln + electroslag furnace. The working principle is to pre-restore the stainless steel pre-reduced iron sheet in the raw material field, and after screening, mixing and briquetting, it is put into the roasting tank. The calcination tank is preheated, calcined and heat-cooled in the tunnel kiln to complete a reduction to obtain a semi-finished product. The Fe, Cr and some Mn and Ni in the pre-reduced iron sheet of the stainless steel are initially reduced to metal, but the semi-finished product still contains more Impurities. The semi-finished product enters the lining electric slag furnace after crushing magnetic separation and briquetting. The slag in the slag slag furnace is carefully designed to reduce the oxidation of the metal in the finished product, because the semi-finished product is very low in C and extremely easy to be in the air. Secondary oxidation. When the semi-finished product enters the high-temperature molten slag in the slag washing furnace, the impurities are adsorbed by the slag, and the metal is further purified, thereby realizing the slag-iron separation, and fully recovering the metal elements such as Cr, Fe, Ni, Mn of the stainless steel pre-reduced iron sheet. Realize the recycling of stainless steel pre-reduced iron resources.

The beneficial effects of the invention are:

As described above, the present invention can effectively recover the precious metals such as chromium and nickel of the stainless steel oxide scale in addition to the iron of the stainless steel oxide scale as compared with the electric furnace method and the blast furnace method. The process also has the advantages of strong adaptability of raw materials, large processing capacity, easy control of components, simple and reliable operation, low cost, and almost no waste gas, waste water and other pollutants in the production process, and achieves good economic and environmental benefits. . In addition, the present invention has the advantages of low power consumption and low overall cost. In addition to the effective recovery of iron and precious metals from stainless steel oxide scales, the present invention is also suitable for the recovery of dust ash from stainless steel.

detailed description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a specific embodiment of the stainless steel scale recycling two-step reduction method will be described in detail with reference to the examples. However, the specific embodiment of the stainless steel scale regeneration using the two-step reduction method is not limited to the following examples.

Embodiment 1

This embodiment is an 8 ton stainless steel scale.

1. After the stainless steel oxide scale raw material is removed from the cylindrical sieve and the vibrating screen, the powder with a particle size of less than 3 mm is heated and dried to a moisture content of less than 1%, and then sent to the mixing chamber, and the binder is added in proportion in the mixing chamber. (a small amount of water glass, etc.), a reducing agent, a desulfurizing agent (coke powder, lime powder) are mixed.

2. The mixed material is pressed into a high-precision circular cylinder of 180 mm, outer diameter 150 mm, and inner diameter of 70 mm by a briquetting machine, and then the circular cylinder is loaded into the roasting can by an electromechanical hand.

3. Cover the filled roasting tank and place it on the tunnel trolley to enter the tunnel kiln. The roasting tank is gradually upgraded from room temperature to room temperature.

Preheating and drying at 900 °C, then baking at 950~1180 °C for 20 hours, and finally cooling to 200~300 °C, then exiting the tunnel kiln into semi-finished products.

4. After the semi-finished product is crushed and magnetically selected, it is pressed into a cold compact having a density of about 4.5 g/cm ³ by a briquetting machine.

5. The cold press block is sent to a lining furnace for slag washing. The electroslag furnace adopts graphite electrode, and the furnace lining is graphite carbon brick. The slag system CaO:CaF ratio of the electroslag furnace is 1.22, adding A1203 which accounts for 10% of the total slag system, and the slag thickness of the slag-lined slag furnace is controlled. Between 300 and 400 mm, a reducing agent such as coke or SiC is added to the slag washing process to sufficiently reduce the unreduced metal oxide in the semi-finished product. Other operations are performed in accordance with the requirements of existing electroslag furnaces.

6. When the composition of the above molten steel meets the requirements, tapping, closely observe the steel extraction process, accurately control the amount of retained slag in the retained steel, and keep the steel at 50-100mm.

In this embodiment, 8 tons of stainless steel iron oxide scale can recover 5 tons of chromium-nickel iron material, and the rest is manganese-rich slag containing more than 20% manganese.

Embodiment 2

This embodiment is a 12 ton stainless steel scale.

2. The mixed material is pressed into a high-standard circular cylinder of 180 mm, outer diameter 150 mm and inner diameter of 70 mm by a briquetting machine, and then the circular cylinder is loaded into the roasting can by an electric manipulator.

3. Cover the filled roasting tank and place it on the tunnel trolley to enter the tunnel kiln. The roasting tank is preheated and dried by gradually increasing from room temperature to 900 °C, and then subjected to high temperature of 950~1180 °C for 20 hours. Roasting, and finally gradually cooling to 200~300 °C, then exiting the tunnel kiln into semi-finished products.

5. The cold press block is sent to a lining furnace for slag washing. The electroslag furnace adopts graphite electrode, the furnace lining is graphite carbon brick, the slag system CaO:CaF ratio of the electroslag furnace is 1.5, the addition of A1203 which accounts for 8% of the total slag system, and the slag thickness of the lining electroslag furnace is controlled at 300-400mm Between the slag washing process, a reducing agent such as coke or SiC is further added to sufficiently reduce the unreduced metal oxide in the semi-finished product. Other operations are performed in accordance with the requirements of existing electroslag furnaces.

In this embodiment, 12 tons of stainless steel iron oxide scale can recover 7.5 tons of chromium-nickel iron material, and the rest is manganese-rich slag containing more than 20% manganese. Embodiment 3

This embodiment is a 16 ton stainless steel scale.

2. The mixed material is pressed into a high-standard circular cylinder of 180 mm, outer diameter of 150 mm and inner diameter of 70 mm by a briquetting machine, and then the circular cylinder is loaded into the roasting can by an electric manipulator. 3. Cover the filled roasting tank and place it on the tunnel trolley to enter the tunnel kiln. The roasting tank is preheated and dried by gradually increasing from room temperature to 900 °C, and then subjected to high temperature of 950~1180 °C for 20 hours. Roasting, and finally gradually cooling to 200~300 °C, then exiting the tunnel kiln into semi-finished products.

5. The cold press block is sent to a lining furnace for slag washing. The electroslag furnace adopts graphite electrode, and the furnace lining is graphite carbon brick. The slag system CaO:CaF ratio of the electroslag furnace is 1.86, adding A1203 which accounts for 5% of the total slag system, and the slag thickness of the lining electroslag furnace is controlled at 300-400mm. Between the slag washing process, a reducing agent such as coke or SiC is further added to sufficiently reduce the unreduced metal oxide in the semi-finished product. Other operations are performed in accordance with the requirements of existing electroslag furnaces.

In this embodiment, 16 tons of stainless steel iron oxide scale can recover 10 tons of chromium-nickel iron material, and the rest is manganese-rich slag containing more than 20% manganese.

Claims

Claim

1. A two-step reduction method for recycling stainless steel oxide scale, characterized in that the process of the method is as follows:

1. Raw material screening and mixing

The pulverized stainless steel oxide scale raw material containing Fe 50%, Cr 5%, Mn^6% Ni^0.4% P 0.06%, S 0.06% (% by weight) under 3 mm is passed through a cylindrical sieve and vibrated Screening, after removing impurities, the powder is heated and dried to less than 1% moisture, and then sent to the mixing chamber to add water glass, coke powder, lime powder and stainless steel iron oxide powder;

2. Clamping and canning

Putting the mixed stainless steel iron oxide powder into a briquetting machine for pressing, and then placing the briquetting body into the melting tank;

3. Calcination and cooling

The roasting tank with the briquetting body is capped and placed on the tunnel trolley to enter the tunnel kiln. In the tunnel kiln, the preheating drying section is gradually raised from room temperature to 900 °C, and then enters 950~1180 °C/ The 20-hour high-temperature roasting section is calcined, and finally enters the cooling section and is gradually cooled to 200~300 °C, and then the tunnel kiln is semi-finished;

4. Semi-finished product crushing, magnetic separation and briquetting

The semi-finished product is crushed and magnetically selected by a briquetting machine into a cold compact having a density of about 4.5 g/cm 3 ;

5. Melting and purifying in a lining furnace

The cold briquetting block is sent to the slag electroslag furnace for slag washing, and the lining electric slag furnace adopts continuous operation mode, and the lining refractory material is one of semi-graphite carbon brick, graphite carbon brick or silicon carbide combined with silicon carbide brick. For refractory bricks, the slag used is composed of CaO and CaF. The ratio of CaO:CaF is 1.22~1.86, and the thickness of lining electroslag slag is controlled between 300~400mm. Coke is added as usual during the slag washing process. The SiC reducing agent sufficiently reduces the unreduced metal oxide in the semi-finished product;

6. Steel tapping, pouring

When the composition of the above molten steel meets the requirements of the following table, the tapping water shall be accurately controlled to control the amount of retained steel, and the retained steel shall be controlled at 50 to 100 mm, and poured into a steel ingot mold for cooling;

Finished chrome-nickel iron quality indicator table.

2. A two-step reduction method for recycling stainless steel oxide scale according to claim 1, wherein the refractory material of the lining electric slag furnace is graphite carbon brick.

A two-step reduction method for recycling stainless steel oxide scale according to claim 1, characterized in that A1203 which accounts for 5 to 10% of the total amount of the slag system is further added to the slag system.