Blowing desulfurization method

Abstract

The invention discloses a blowing desulfurization method, and belongs to the technical field of metallurgy. In order to solve the problems of low desulfurization rate, low magnesium utilization rate and the like in the prior art, the invention provides a blowing desulfurization method which comprises the following steps: dispersing magnesium-aluminum alloy powder in an organic solvent, and adding a passivating agent to obtain passivated magnesium-aluminum alloy powder; and inserting the spray gun into a ladle, firstly spraying the passivated active lime and the aluminum powder, and then spraying the passivated magnesium-aluminum alloy powder to finish desulfurization. The magnesium-aluminum alloy powder is utilized to create in-situ desulfurization thermodynamic conditions, the magnesium vapor pressure is reduced, the retention time in the molten iron is prolonged, the sulfur content in the molten iron is reduced, the magnesium utilization rate is increased, the material adding conditions are controlled, the desulfurization effect is fully exerted, and the desulfurization effect is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a spray desulfurization method. Background Art

[0002] Currently, there are two widely used methods for molten iron desulfurization: the injection method and the KR method. The injection method uses an inert gas as a carrier to spray desulfurization powder into the molten iron through a spray gun, causing the desulfurizer to react with the molten iron, achieving desulfurization. However, the desulfurization powder does not fully contact the sulfur in the molten iron, resulting in low desulfurization efficiency and high desulfurizer consumption. Desulfurization using passivated magnesium powder spraying has a short residence time and high desulfurization consumption. The KR method inserts a stirring head into the molten iron to a certain depth. The vortex generated by the intense stirring of a large agitator allows the desulfurization powder to contact and react with the molten iron components, achieving desulfurization. The KR method has higher desulfurization efficiency and lower desulfurization powder consumption, but it also results in a significant temperature drop.

[0003] CN115029511A discloses a calcium oxide-based desulfurizer for spraying complex vanadium-titanium high-sulfur molten iron and its application, wherein the calcium oxide-based desulfurizer is specifically lime powder CaO, calcium carbide CaC2, fluorite CaF2, and AD powder, and has the following components in the following mass ratio: CaO: 68wt%~75wt%, CaC2: 7wt%~8wt%, CaF2: 5wt%~6wt%, Al: 0.5wt%~1.0wt%, Al2O3: 2wt%~3wt%, and the remainder is inevitable impurities; and the amount of desulfurizer added is determined according to the original sulfur content of the molten iron and the molten iron temperature; the mixed calcium oxide-based desulfurizer is sprayed into the molten iron through a spray gun using nitrogen as a carrier gas for desulfurization, solving the problems of low desulfurization rate of complex vanadium-titanium high-sulfur molten iron and long pretreatment time affecting production organization. However, calcium fluoride in this method is not environmentally friendly and there is a risk of increased erosion of refractory materials.

[0004] CN107287377A discloses a composite desulfurizer for hot metal injection desulfurization and its preparation method. The composite desulfurizer comprises the following components by weight: 80-90% passivated magnesium powder, 1-8% metallic aluminum, 2-10% aluminum oxide, and the remainder being unavoidable impurities. This method increases the utilization rate of the passivated magnesium powder in the composite desulfurizer by an average of more than 5%, reducing the cost of hot metal desulfurization. The aluminum component of the composite desulfurizer is derived from metallic aluminum and aluminum oxide found in industrial aluminum ash, significantly reducing the production cost of the composite desulfurizer and enabling the reuse of industrial aluminum ash as waste. However, this method still does not address the issue of low magnesium utilization.

[0005] CN108504821A discloses a vanadium-titanium molten iron composite desulfurizer, which contains the following components in weight percentage: CaO 70-85%, Al2O3 5-20%, Al 2-8%, Mg 1-7%, Na2CO3 2-13%, and the rest are inevitable impurities; the vanadium-titanium molten iron composite desulfurizer is a powder mixed with raw materials containing CaO, Al2O3, Al, Mg and Na2CO3 respectively; desulfurization is carried out by a blowing method.

[0006] CN103789502A discloses a method for preparing a desulfurizer for silicon steel sheets, wherein the desulfurizer is composed of the following components by weight: 50-54 parts of CaO, 18-22 parts of Al, 12-16 parts of MgO, 10-12 parts of SiO2, 3-7 parts of Al2O3, 3-5 parts of Fe2O3, 5-7 parts of CaF2, 5-7 parts of BaO, 10-12 parts of SiO2, 3-7 parts of Al2O3, 3-5 parts of Fe2O3, 5-7 parts of CaF2, 5-7 parts of BaO, 5-7 parts of Mg ... 7-9 parts, the preparation method comprises the following steps: 1) mixing: mixing the materials in proportion; 2) crushing: placing the mixed materials into a crusher for crushing and processing so that the material particle size is ≤0.4mm; 3) passivation: spraying a 30%-50% organic silicone resin solution for passivation protection, the amount of the organic silicone solution is 0.4%-0.8% of the total weight of the material, and after passivation treatment, a passivation film with a thickness of 0.4-0.6um is formed on the surface of the material particles; 4) drying: after crushing and passivation, drying treatment is required, the drying temperature is 120-150°C, and the drying time is 30-60min, so that the organic components of the passivation solution are quickly volatilized and a trace amount of water is discharged at the same time.

[0007] CN1354057A discloses a granular passivated magnesium powder for off-furnace desulfurization in the steel metallurgical industry. The powder is prepared by coating a hydrophobic layer on the surface of granular magnesium powder having a particle size of 0.1 to 2.0 μm, and then adhering a flame retardant layer to the surface of the hydrophobic layer. The hydrophobic agent is an organic substance that is solid at room temperature, such as rosin, asphalt, resin, and mixtures thereof. The amount of the hydrophobic agent is 1 to 10% of the total weight of the passivated magnesium powder. The flame retardant is one or more oxides or salts of Ca, Mg, Al, and Si, such as CaO, MgO, CaCO₃, MgCO₃, Al₂O₃, SiO₂, and mixtures thereof. The flame retardant is a powder having a particle diameter of 0.08 mm or less, preferably 0.03 mm or less. The amount of the flame retardant is 1 to 20% of the total weight of the passivated magnesium powder. The total weight of the hydrophobic agent and flame retardant is 3 to 25% of the total weight of the passivated magnesium powder. Summary of the Invention

[0008] In response to the shortcomings of the existing technology, the present invention proposes a spray desulfurization method, which uses Mg-Al alloy powder to create in-situ desulfurization thermodynamic conditions, while reducing the magnesium vapor pressure and extending its residence time in molten iron, thereby reducing the sulfur content of the molten iron and improving the magnesium utilization rate.

[0009] The present invention provides a spray desulfurization method, which comprises the following steps: A. (The entire process of preparing the passivated magnesium-aluminum alloy powder is carried out under an inert atmosphere) Under an inert atmosphere, a magnesium-aluminum alloy ingot is crushed into magnesium-aluminum alloy powder (the magnesium-aluminum alloy powder can be prepared by mechanical crushing), the magnesium-aluminum alloy powder is dispersed in an organic solvent, a passivating agent is added, and the mixture is reacted under stirring or ultrasonic conditions so that the passivating agent uniformly coats the surface of the magnesium-aluminum alloy powder, and then filtered, dried, and crushed to obtain the passivated magnesium-aluminum alloy powder; B. Insert the spray gun into the molten iron ladle at a distance of 400~550mm from the bottom. Use nitrogen as the carrier and a pressure of 0.45~0.6MPa to spray passivation active lime and aluminum powder. The mass ratio of passivation active lime to aluminum powder is 7~8:2~3. The total amount of passivation active lime and aluminum powder sprayed is 5.0~6.0kg / t iron. Then spray passivation magnesium-aluminum alloy powder at a spraying amount of 1.0~1.5kg / t iron to complete desulfurization.

[0010] Wherein, in the above-mentioned desulfurization injection method, in step A, the Mg content in the magnesium-aluminum alloy ingot is 80-90wt%, and the Al content is 20-10wt%.

[0011] Wherein, in the above-mentioned injection desulfurization method, in step A, the particle size of the magnesium-aluminum alloy powder is ≤1 mm.

[0012] In the above-mentioned spray desulfurization method, in step A, the organic solvent is at least one of ethanol and toluene. In the present invention, the amount of organic solvent used is appropriate to ensure uniform dispersion of the magnesium-aluminum alloy powder and dissolve the passivating agent. Residual organic solvent is subsequently removed by filtration and drying.

[0013] Wherein, in the above-mentioned injection desulfurization method, in step A, the passivating agent is at least one of stearic acid, paraffin or silane coupling agent.

[0014] Wherein, in the above-mentioned desulfurization injection method, in step A, the amount of the passivating agent is 5-15% of the mass of the magnesium-aluminum alloy powder.

[0015] Wherein, in the above-mentioned injection desulfurization method, in step A, the reaction temperature is 50~80°C.

[0016] Wherein, in the above-mentioned injection desulfurization method, in step B, the particle size of the passivated active lime is ≤1mm.

[0017] Wherein, in the above-mentioned injection desulfurization method, in step B, the particle size of the aluminum powder is ≤1mm.

[0018] In the above-mentioned desulfurization injection method, in step B, the sulfur content of the molten iron is reduced to below 20 ppm, and the magnesium utilization rate is ≥51%.

[0019] Beneficial effects of the present invention: Usually, magnesium powder desulfurization easily generates magnesium vapor, and its utilization rate is not high. The present invention adopts magnesium-aluminum alloy, which, on the one hand, delays the formation of magnesium vapor and reduces the magnesium vapor pressure. On the other hand, Al in the alloy is deoxidized, promoting in-situ desulfurization, thereby improving magnesium utilization and desulfurization effect. At the same time, the use of passivator coating is conducive to powder spraying and is safer.

[0020] The present invention first sprays passivated active lime and aluminum powder, and then sprays passivated magnesium-aluminum alloy powder, and controls the adding conditions and amounts of the three. When the initial sulfur content is high, the passivated active lime and aluminum powder are added for desulfurization. As the sulfur content decreases, the passivated magnesium-aluminum alloy powder with stronger desulfurization ability is used to further deeply desulfurize, thereby improving the utilization rate of each material and giving full play to the desulfurization effect of each material.

[0021] The present invention has strong operability. By optimizing the desulfurization materials and processes, the sulfur content of molten iron can be reduced to below 20 ppm, the magnesium utilization rate is ≥51%, the magnesium utilization rate is increased by more than 6%, and the cost is reduced. It is suitable for promotion and application in steel enterprises and has certain economic benefits. DETAILED DESCRIPTION

[0022] Specifically, a spray desulfurization method includes the following steps: A. (The entire process of preparing the passivated magnesium-aluminum alloy powder is carried out under an inert atmosphere) Under an inert atmosphere, a magnesium-aluminum alloy ingot is crushed into magnesium-aluminum alloy powder (the magnesium-aluminum alloy powder can be prepared by mechanical crushing), the magnesium-aluminum alloy powder is dispersed in an organic solvent, a passivating agent is added, and the mixture is reacted under stirring or ultrasonic conditions so that the passivating agent uniformly coats the surface of the magnesium-aluminum alloy powder, and then filtered, dried, and crushed to obtain the passivated magnesium-aluminum alloy powder; B. Insert the spray gun into the molten iron ladle at a distance of 400~550mm from the bottom. Use nitrogen as the carrier and a pressure of 0.45~0.6MPa to spray passivation active lime and aluminum powder. The mass ratio of passivation active lime to aluminum powder is 7~8:2~3. The total amount of passivation active lime and aluminum powder sprayed is 5.0~6.0kg / t iron. Then spray passivation magnesium-aluminum alloy powder at a spraying amount of 1.0~1.5kg / t iron to complete desulfurization.

[0023] The present invention utilizes a magnesium-aluminum alloy to delay magnesium vapor formation and reduce magnesium vapor pressure. It also deoxidizes the aluminum in the alloy, promoting in-situ desulfurization, thereby improving magnesium utilization and desulfurization effectiveness. In step A, the magnesium-aluminum alloy ingot contains 80-90 wt% Mg and 20-10 wt% Al. In step A, the magnesium-aluminum alloy powder has a particle size of ≤1 mm.

[0024] For safety and powder spraying needs, the present invention coats the magnesium-aluminum alloy powder with a passivator. In step A, the organic solvent is at least one of ethanol or toluene. In the present invention, the amount of organic solvent used is appropriate to ensure that the magnesium-aluminum alloy powder can be evenly dispersed and can dissolve the passivator. Residual organic solvent will be removed by filtration and drying. In step A, the passivator is at least one of stearic acid, paraffin, or a silane coupling agent. In step A, the amount of the passivator used is 5-15% of the mass of the magnesium-aluminum alloy powder.

[0025] In step A of the present invention, the reaction temperature is 50-80°C.

[0026] In step B of the present invention, the particle size of the passivated active lime is ≤1 mm.

[0027] In step B of the present invention, the particle size of the aluminum powder is ≤1 mm.

[0028] In step B of the present invention, the sulfur content of the molten iron is removed to below 20 ppm, the magnesium utilization rate is ≥51%, and the magnesium utilization rate is increased by more than 6%, which significantly improves the desulfurization effect and the magnesium utilization rate.

[0029] The present invention is further described in detail below through examples, but the protection scope of the present invention is not limited to the scope of the examples.

[0030] Example 1 Under an inert atmosphere, a magnesium-aluminum alloy ingot (Mg content 80wt%, Al content 20wt%) was mechanically crushed into a powder with a particle size of less than 1mm. The magnesium-aluminum alloy powder was dispersed in an appropriate amount of ethanol, and 10% stearic acid as a passivating agent was added. The mixture was reacted at 50-60°C under stirring to allow the passivating agent to evenly coat the surface of the magnesium powder. The powder was then filtered, dried and crushed to obtain a passivated magnesium-aluminum alloy powder.

[0031] Insert the spray gun into the molten iron ladle at a distance of 400mm from the bottom. Use nitrogen as the carrier and a pressure of 0.45MPa to spray passivated active lime (particle size less than 1mm) and aluminum powder (particle size less than 1mm) in a mass ratio of 7:3, with a total spray volume of 5.0kg / t iron. Then spray passivated magnesium-aluminum alloy powder at a spray volume of 1.0kg / t iron. This can reduce the sulfur content of the molten iron to 18ppm, and the magnesium utilization rate to 56%, an increase of more than 11% (the existing process usually adopts CaO+Mg mixed spraying for desulfurization, with a magnesium utilization rate of 35~45%).

[0032] Example 2 Under an inert atmosphere, a magnesium-aluminum alloy ingot (Mg content 85wt%, Al content 15wt%) was mechanically crushed into a powder with a particle size of less than 1mm. The magnesium-aluminum alloy powder was dispersed in an appropriate amount of ethanol, and 10% passivating agent paraffin was added. The mixture was reacted at 50-60°C under stirring to allow the passivating agent to evenly coat the surface of the magnesium powder. The powder was then filtered, dried and crushed to obtain a passivated magnesium-aluminum alloy powder.

[0033] A rotary lance is inserted into the molten iron ladle at a distance of 470mm from the bottom. Using nitrogen as a carrier, at a pressure of 0.5MPa, passivation active lime (particle size less than 1mm) and aluminum powder (particle size less than 1mm) are sprayed in a mass ratio of 7.5:2.5, with a total injection volume of 5.5kg / t iron. Passivation magnesium-aluminum alloy powder is then sprayed in at a volume of 1.2kg / t iron. This can reduce the sulfur content of the molten iron to 16ppm, achieve a magnesium utilization rate of 54%, and increase the magnesium utilization rate by more than 9%.

[0034] Example 3 Under an inert atmosphere, a magnesium-aluminum alloy ingot (Mg content 90wt%, Al content 10wt%) was mechanically crushed into a powder with a particle size of less than 1mm. The magnesium-aluminum alloy powder was dispersed in an appropriate amount of toluene, and 10% of a passivating silane coupling agent was added. The mixture was reacted at 50-60°C under stirring to uniformly coat the surface of the magnesium powder with the passivating agent. The powder was then filtered, dried, and crushed to obtain a passivated magnesium-aluminum alloy powder.

[0035] A rotary lance is inserted into the molten iron ladle at a distance of 550mm from the bottom. Using nitrogen as a carrier, at a pressure of 0.6MPa, passivation active lime (particle size less than 1mm) and aluminum powder (particle size less than 1mm) are sprayed in a mass ratio of 8:2, with a total injection volume of 6.0kg / t iron. Passivation magnesium-aluminum alloy powder is then sprayed in at a volume of 1.5kg / t iron. This can reduce the sulfur content of the molten iron to 14ppm, achieve a magnesium utilization rate of 51%, and increase the magnesium utilization rate by more than 6%.

Claims

1. Injection desulfurization method, characterized by: The following steps are involved: A. Under an inert atmosphere, a magnesium-aluminum alloy ingot is crushed into magnesium-aluminum alloy powder, the magnesium-aluminum alloy powder is dispersed in an organic solvent, a passivating agent is added, and the mixture is reacted under stirring or ultrasonic conditions so that the passivating agent uniformly coats the surface of the magnesium-aluminum alloy powder, and then filtered, dried and crushed to obtain passivated magnesium-aluminum alloy powder; B. Insert the spray gun into the molten iron ladle at a distance of 400~550mm from the bottom. Use nitrogen as the carrier and a pressure of 0.45~0.6MPa to spray passivation active lime and aluminum powder. The mass ratio of passivation active lime to aluminum powder is 7~8:2~3. The total amount of passivation active lime and aluminum powder sprayed is 5.0~6.0kg / t iron. Then spray passivation magnesium-aluminum alloy powder at a spraying amount of 1.0~1.5kg / t iron to complete desulfurization.

2. The injection desulfurization method according to claim 1, characterized in that: In step A, the magnesium-aluminum alloy ingot has a Mg content of 80-90 wt % and an Al content of 20-10 wt %.

3. The injection desulfurization method according to claim 1, characterized in that: In step A, the particle size of the magnesium-aluminum alloy powder is ≤1 mm.

4. The injection desulfurization method according to claim 1, characterized in that: In step A, the organic solvent is at least one of ethanol or toluene.

5. The injection desulfurization method according to claim 1, characterized in that: In step A, the passivating agent is at least one of stearic acid, paraffin or a silane coupling agent.

6. The injection desulfurization method according to claim 1, characterized in that: In step A, the amount of the passivating agent is 5-15% of the mass of the magnesium-aluminum alloy powder.

7. The injection desulfurization method according to claim 1, characterized in that: In step A, the reaction temperature is 50-80°C.

8. The injection desulfurization method according to claim 1, characterized in that: In step B, the particle size of the passivated active lime is ≤1 mm.

9. The injection desulfurization method according to claim 1, characterized in that: In step B, the particle size of the aluminum powder is ≤1 mm.

10. The injection desulfurization method according to any one of claims 1 to 9, characterized in that: In step B, after desulfurization is completed, the sulfur content of the molten iron is reduced to below 20 ppm, and the magnesium utilization rate is ≥51%.