Biological utilization method based on molten iron desulfurization slag

Abstract

The invention relates to the technical field of resource utilization, in particular to a biological utilization method based on molten iron desulfurization slag, which comprises the following preparation steps: S1, crushing, magnetically separating and sieving the molten iron desulfurization slag to obtain desulfurization slag powder; s2, mixing the desulfurization slag powder with a sulfuric acid solution, adjusting the pH value to 2-4, reacting to obtain slurry and hydrogen sulfide, and filtering the slurry to obtain filtrate and acid leaching slag containing silicon dioxide; s3, combining hydrogen sulfide with sulfur-oxidizing bacteria loaded in the ceramic filler, and carrying out biological oxidation to obtain sulfuric acid; and S4, adding an alkaline reagent into the filtrate, adjusting the pH value of the filtrate to 4.5-5.5, and filtering to obtain aluminum ion-containing precipitate and filtrate. According to the method, the industrially produced molten iron desulfurization slag is used as a raw material, the sulfuric acid is produced in a biological oxidation manner, besides the main product sulfuric acid, by-products such as acid leaching slag containing silicon dioxide, aluminum hydroxide and recycled iron are separated, the economic value of the whole process is improved, and the problem of land resource occupation is relieved.

Description

Technical Field

[0001] This invention relates to the field of resource utilization technology, and in particular to a method for the biological utilization of molten iron desulfurization slag. Background Technology

[0002] External desulfurization of molten iron refers to a pretreatment process where molten iron is desulfurized outside the furnace before entering the steelmaking furnace. This reduces the sulfur content of pig iron, improves steel quality, and enhances the overall technical and economic indicators of the steel plant. Industrially, lime, calcium carbide, soda ash, and magnesium powder are commonly used as desulfurizing agents to react with molten iron, removing sulfur by generating stable sulfides. This process produces a large amount of desulfurization slag. This slag contains significant amounts of calcium, magnesium, iron, and sulfur. With industrial development, the amount of desulfurization slag discharged annually is increasing. If it can be recycled and utilized through scientific processes, it can not only alleviate the environmental pressure of solid waste accumulation but also create significant economic value. Summary of the Invention

[0003] The purpose of this invention is to provide a biological utilization method based on molten iron desulfurization slag, so as to achieve the targeted separation and efficient recovery of impurities such as iron, sulfur, aluminum, and silicon in molten iron desulfurization slag.

[0004] like Figure 1 As shown, to achieve the above objectives, this invention provides a method for the bio-utilization of molten iron desulfurization slag, comprising the following preparation steps: S1. The desulfurization slag of molten iron is crushed, magnetically separated, and sieved to obtain desulfurization slag powder; S2. Mix the desulfurization slag powder with sulfuric acid solution, adjust the pH to 2-4, react to obtain slurry and hydrogen sulfide, filter the slurry to obtain filtrate and acid leaching residue containing silica. S3. Hydrogen sulfide is combined with sulfur-oxidizing bacteria loaded in ceramic packing and bio-oxidized to obtain sulfuric acid. S4. Add an alkaline reagent to the filtrate to adjust the pH of the filtrate to 4.5-5.5, filter, and obtain aluminum ion precipitate and filtrate.

[0005] In this invention, the sieve in S1 has a mesh size of 100-200, and the resulting desulfurization slag powder contains calcium ions, magnesium ions, aluminum ions, silicon ions, sulfur ions, etc.

[0006] In this invention, the mass concentration of the sulfuric acid solution in S2 is 5%-15%, the reaction temperature is 25-60℃, and the reaction pressure is -500Pa to -50Pa. The reaction is carried out under negative pressure conditions, which is conducive to the generation of hydrogen sulfide.

[0007] In this invention, the filtrate obtained in S2 includes calcium ions, magnesium ions, aluminum ions, etc.

[0008] In this invention, the gas flow rate of hydrogen sulfide in S3 is 0.8-1.2 m / s. 3 / (m 2 ·h).

[0009] In this invention, the loading of sulfur-oxidizing bacteria in the ceramic packing in S3 is 12%-15%, and the sulfur-oxidizing bacteria include at least one of Thiobacillus thiooxidans and Thiobacillus ferrooxidans.

[0010] In this invention, the temperature of the bio-oxidation reaction in S3 is 28-35℃, and the pH of the bio-oxidation reaction is 1.5-3.5.

[0011] In this invention, the alkaline reagent in S4 includes ammonia water, and the volume concentration of ammonia water is 5%-15%.

[0012] In this invention, the filtrate obtained in S4 includes calcium ions and magnesium ions, which can be separated by subsequent processes to obtain the corresponding products.

[0013] The present invention has the following beneficial effects: This invention provides a method for the bio-utilization of molten iron desulfurization slag, comprising the following preparation steps: S1, crushing, magnetically separating, and sieving the molten iron desulfurization slag to obtain desulfurization slag powder; S2, mixing the desulfurization slag powder with sulfuric acid solution, adjusting the pH to 2-4, reacting to obtain a slurry and hydrogen sulfide, filtering the slurry to obtain a filtrate and a silica-containing acid leaching residue; S3, combining the hydrogen sulfide with sulfur-oxidizing bacteria loaded in ceramic packing material for bio-oxidation to obtain sulfuric acid; S4, adding an alkaline reagent to the filtrate, adjusting the pH of the filtrate to 4.5-5.5, filtering to obtain an aluminum ion precipitate and a filtrate.

[0014] In step S1, this invention recovers metallic iron from the desulfurization slag of molten iron through magnetic separation, avoiding interference from iron in subsequent reactions. In step S2, the desulfurization slag powder is mixed with sulfuric acid solution, preferentially generating hydrogen sulfide gas. Sulfur-oxidizing bacteria then convert the hydrogen sulfide gas into sulfuric acid, avoiding the influence of heavy metal ions in the desulfurization slag powder on the activity of the sulfur-oxidizing bacteria.

[0015] This invention loads sulfur-oxidizing bacteria onto the surface of a ceramic packing material. The ceramic packing material has the characteristics of large specific surface area and strong acid resistance, which solves the problems of easy loss of free bacteria and dispersion of active area, and improves the contact efficiency between sulfur-oxidizing bacteria and hydrogen sulfide gas.

[0016] In step S2 of this invention, the pH is adjusted to 2-4, and under acidic conditions, acid-soluble metal ions such as Ca, Al, and Mg ions generate corresponding salt solutions. Since the acidity is too low to break the silicon-oxygen bonds in the desulfurization slag powder, silica is retained in the form of acid leaching residue.

[0017] In step S4 of this invention, the pH of the filtrate is adjusted to 4.5-5.5 to convert the Al ions in the filtrate into aluminum hydroxide precipitate. At this pH environment, the precipitation threshold of Ca and Mg ions is not reached, so hydroxides will not be formed.

[0018] This invention uses desulfurization slag from molten iron produced in industrial processes as raw material and employs a biological oxidation method to produce sulfuric acid. In addition to the main product, sulfuric acid, byproducts such as silica-containing acid leaching slag, aluminum hydroxide, and recovered iron are also separated, which enhances the economic value of the overall process and alleviates the problem of land resource occupation.

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a biological utilization method based on molten iron desulfurization slag provided by the present invention. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should be understood in their ordinary sense by those skilled in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.

[0022] Example 1 The composition of desulfurization slag in molten iron includes: Fe: 40.73%, CaO: 31.44%, SiO2: 8.09%, MgO: 6.32%, CaS: 12.43%, with the remainder being unavoidable impurities.

[0023] S1. Take 500 kg of molten iron desulfurization slag, crush it coarsely with a jaw crusher, and then recover the mixed elemental iron with a magnetic separator. Then, put the molten iron desulfurization slag with the elemental iron removed into a wet ball mill and grind it until the particle size passes through a 200-mesh standard sieve to obtain desulfurization slag powder. S2. Under closed conditions, the desulfurization slag powder obtained in step S1 is mixed with 10% sulfuric acid. The pH of the system is adjusted to 3.5, and the pressure inside the reactor is maintained at -200 Pa and the temperature at 55℃. A slurry and hydrogen sulfide are obtained. The slurry is filtered to obtain the filtrate (mainly containing Ca). 2+ Mg 2+ Al 3+ (e.g., metal ions) and acid leaching residue containing silica; S3. Dispose of the hydrogen sulfide gas generated in step S2 at a rate of 2m 3 / (m 2The solution was fed into a bioreactor containing *Thiobacillus ferrooxidans* (which was loaded in ceramic packing at a rate of 15%) at a rate of h. The pH in the bioreactor was maintained at 2 and the temperature at 35°C. The bio-oxidation reaction was carried out to obtain sulfuric acid (4334.1 kg measured). S4. After removing the filtrate obtained in step S2, add 10% ammonia solution to adjust the pH of the filtrate to 4.5, filter, and obtain an aluminum ion precipitate and filtrate (mainly containing Ca). 2+ Mg 2+ ).

[0024] Example 2 The composition of desulfurization slag in molten iron includes: Fe: 42.57%, CaO: 29.19%, SiO2: 7.83%, MgO: 5.42%, CaS: 11.43%, with the remainder being unavoidable impurities.

[0025] S1. Take 500 kg of molten iron desulfurization slag, crush it coarsely with a jaw crusher, and then recover the mixed elemental iron with a magnetic separator. Then, put the molten iron desulfurization slag with the elemental iron removed into a wet ball mill and grind it until the particle size passes through a 150-mesh standard sieve to obtain desulfurization slag powder. S2. Under closed conditions, the desulfurization slag powder obtained in step S1 is mixed with 15% sulfuric acid. The pH of the system is adjusted to 3.5, and the pressure inside the reactor is maintained at -280 Pa and the temperature at 60°C. A slurry and hydrogen sulfide are obtained. The slurry is filtered to obtain the filtrate (mainly containing Ca). 2+ Mg 2+ Al 3+ (e.g., metal ions) and acid leaching residue containing silica; S3. Dispose of the hydrogen sulfide gas generated in step S2 at a speed of 0.8 m 3 / (m 2 The solution was fed into a bioreactor containing *Thiobacillus ferrooxidans* (which was loaded in ceramic packing at a rate of 15%) at a rate of h. The pH in the bioreactor was maintained at 3 and the temperature at 35°C. The bio-oxidation reaction was carried out to obtain sulfuric acid (4057.6 kg measured). S4. After removing the filtrate obtained in step S2, add 10% ammonia solution to adjust the pH of the filtrate to 4.5, filter, and obtain an aluminum ion precipitate and filtrate (mainly containing Ca). 2+ Mg 2+ ).

[0026] Example 3 The composition of desulfurization slag in molten iron includes: Fe: 41.57%, CaO: 30.82%, SiO2: 8.77%, MgO: 5.47%, CaS: 12.82%, with the remainder being unavoidable impurities.

[0027] S1. Take 500 kg of molten iron desulfurization slag, crush it coarsely with a jaw crusher, and then recover the mixed elemental iron with a magnetic separator. Then, put the molten iron desulfurization slag with the elemental iron removed into a wet ball mill and grind it until the particle size passes through a 100-mesh standard sieve to obtain desulfurization slag powder. S2. Under closed conditions, the desulfurization slag powder obtained in step S1 is mixed with 10% sulfuric acid by mass concentration. The pH of the system is adjusted to 4, and the pressure inside the reactor is maintained at -300 Pa and the temperature at 50℃. A slurry and hydrogen sulfide are obtained. The slurry is filtered to obtain the filtrate (mainly containing Ca). 2+ Mg 2+ Al 3+ (e.g., metal ions) and acid leaching residue containing silica; S3. Dispose of the hydrogen sulfide gas generated in step S2 at a rate of 1m 3 / (m 2 The solution was introduced into a bioreactor containing Thiobacillus thiooxidans and Thiobacillus ferrooxidans at a rate of h (both Thiobacillus ferrooxidans and Thiobacillus thiooxidans were loaded in ceramic packing material, with a total loading of 12%). The pH in the bioreactor was maintained at 2 and the temperature at 35°C. The bio-oxidation reaction was carried out to obtain sulfuric acid (4692.2 kg measured). S4. After removing the filtrate obtained in step S2, add 15% ammonia solution to adjust the pH of the filtrate to 5.5, filter, and obtain an aluminum ion precipitate and filtrate (mainly containing Ca). 2+ Mg 2+ ).

[0028] Example 4 The composition of desulfurization slag in molten iron includes: Fe: 43.57%, CaO: 29.53%, SiO2: 7.62%, MgO: 5.79%, CaS: 12.69%, with the remainder being unavoidable impurities.

[0029] S1. Take 500 kg of molten iron desulfurization slag, crush it coarsely with a jaw crusher, and then recover the mixed elemental iron with a magnetic separator. Then, put the molten iron desulfurization slag with the elemental iron removed into a wet ball mill and grind it until the particle size passes through a 200-mesh standard sieve to obtain desulfurization slag powder. S2. Under closed conditions, the desulfurization slag powder obtained in step S1 is mixed with 15% sulfuric acid by mass concentration. The pH of the system is adjusted to 2, and the pressure inside the reactor is maintained at -200 Pa and the temperature at 45℃. A slurry and hydrogen sulfide are obtained. The slurry is filtered to obtain the filtrate (mainly containing Ca). 2+ Mg 2+ Al 3+ (e.g., metal ions) and acid leaching residue containing silica; S3. Dispose of the hydrogen sulfide gas generated in step S2 at a velocity of 1.2m. 3 / (m 2The sulfuric acid was introduced into a bioreactor containing Thiobacillus thiooxidans (Thioobacillus thiooxidans was loaded in ceramic packing material at a rate of 15%) at a rate of h. The pH in the bioreactor was maintained at 3.5 and the temperature at 30°C. The bio-oxidation reaction was carried out to obtain sulfuric acid (4523.9 kg measured). S4. After removing the filtrate obtained in step S2, add 10% ammonia solution to adjust the pH of the filtrate to 4.5, filter, and obtain an aluminum ion precipitate and filtrate (mainly containing Ca). 2+ Mg 2+ ).

[0030] Example 5 The composition of desulfurization slag in molten iron includes: Fe: 41.62%, CaO: 30.62%, SiO2: 7.95%, MgO: 6.53%, CaS: 12.97%, with the remainder being unavoidable impurities.

[0031] S1. Take 500 kg of molten iron desulfurization slag, crush it coarsely with a jaw crusher, and then recover the mixed elemental iron with a magnetic separator. Then, put the molten iron desulfurization slag with the elemental iron removed into a wet ball mill and grind it until the particle size passes through a 200-mesh standard sieve to obtain desulfurization slag powder. S2. Under closed conditions, the desulfurization slag powder obtained in step S1 is mixed with 5% sulfuric acid by mass concentration. The pH of the system is adjusted to 4, and the pressure inside the reactor is maintained at -200 Pa and the temperature at 35℃. A slurry and hydrogen sulfide are obtained. The slurry is filtered to obtain the filtrate (mainly containing Ca). 2+ Mg 2+ Al 3+ (e.g., metal ions) and acid leaching residue containing silica; S3. Dispose of the hydrogen sulfide gas generated in step S2 at a speed of 0.8 m 3 / (m 2 The solution was introduced into a bioreactor containing *Thiobacillus ferrooxidans* and *Thiobacillus thiooxidans* (which were loaded in ceramic packing with a total loading of 15%) at a rate of h. The pH in the bioreactor was maintained at 1.5 and the temperature at 28°C. The bio-oxidation reaction was carried out to obtain sulfuric acid (4682.2 kg measured). S4. After removing the filtrate obtained in step S2, add 5% ammonia solution to adjust the pH of the filtrate to 5.5, filter, and obtain an aluminum ion precipitate and filtrate (mainly containing Ca). 2+ Mg 2+ ).

[0032] Example 6 The composition of desulfurization slag in molten iron includes: Fe: 42.97%, CaO: 30.72%, SiO2: 6.92%, MgO: 6.24%, CaS: 12.97%, with the remainder being unavoidable impurities.

[0033] S1. Take 500 kg of molten iron desulfurization slag, crush it coarsely with a jaw crusher, and then recover the mixed elemental iron with a magnetic separator. Then, put the molten iron desulfurization slag with the elemental iron removed into a wet ball mill and grind it until the particle size passes through a 150-mesh standard sieve to obtain desulfurization slag powder. S2. Under closed conditions, the desulfurization slag powder obtained in step S1 is mixed with 5% sulfuric acid by mass concentration. The pH of the system is adjusted to 4, and the pressure inside the reactor is maintained at -200 Pa and the temperature at 50℃. A slurry and hydrogen sulfide are obtained. The slurry is filtered to obtain the filtrate (mainly containing Ca). 2+ Mg 2+ Al 3+ (e.g., metal ions) and acid leaching residue containing silica; S3. Dispose of the hydrogen sulfide gas generated in step S2 at a speed of 0.8 m 3 / (m 2 The solution was introduced into a bioreactor containing *Thiobacillus ferrooxidans* and *Thiobacillus thiooxidans* (which were loaded in ceramic packing with a total loading of 15%) at a rate of h. The pH in the bioreactor was maintained at 3.5 and the temperature at 28°C. The bio-oxidation reaction was carried out to obtain sulfuric acid (4539.5 kg measured). S4. After removing the filtrate obtained in step S2, add 15% ammonia solution to adjust the pH of the filtrate to 5.5, filter, and obtain an aluminum ion precipitate and filtrate (mainly containing Ca). 2+ Mg 2+ ).

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for the biological utilization of molten iron desulfurization slag, characterized in that, The preparation steps include the following: S1. The desulfurization slag of molten iron is crushed, magnetically separated, and sieved to obtain desulfurization slag powder; S2. Mix the desulfurization slag powder with sulfuric acid solution, adjust the pH to 2-4, react to obtain slurry and hydrogen sulfide, filter the slurry to obtain filtrate and acid leaching residue containing silica. S3. Hydrogen sulfide is combined with sulfur-oxidizing bacteria loaded in ceramic packing and bio-oxidized to obtain sulfuric acid. S4. Add an alkaline reagent to the filtrate to adjust the pH of the filtrate to 4.5-5.5, filter, and obtain aluminum ion precipitate and filtrate.

2. The method for biological utilization of molten iron desulfurization slag according to claim 1, characterized in that, The mesh size of the sieve in S1 is 100-200 mesh.

3. The method for biological utilization of molten iron desulfurization slag according to claim 1, characterized in that, The mass concentration of sulfuric acid solution in S2 is 5%-15%, the reaction temperature is 25-60℃, and the reaction pressure is -500Pa to -50Pa.

4. The method for bio-utilization of molten iron desulfurization slag according to claim 3, characterized in that, The hydrogen sulfide permeation rate in S3 is 0.8-1.2 m / s. 3 / (m 2 ·h).

5. The method for biological utilization of molten iron desulfurization slag according to claim 1, characterized in that, The loading of sulfur-oxidizing bacteria in the ceramic packing in S3 is 12%-15%, and the sulfur-oxidizing bacteria include at least one of Thiobacillus thiooxidans and Thiobacillus ferrooxidans.

6. The method for bio-utilization of molten iron desulfurization slag according to claim 1, characterized in that, The temperature for the bio-oxidation reaction in S3 is 28-35℃, and the pH for the bio-oxidation reaction is 1.5-3.

5.

7. A method for the biological utilization of molten iron desulfurization slag according to claim 1, characterized in that, The alkaline reagent in S4 includes ammonia water, with a volume concentration of 5%-15%.

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