A method for comprehensive utilization of hot converter steel slag resources

Abstract

This invention discloses a method for the comprehensive utilization of hot converter steel slag resources. The steps include: pouring hot converter steel slag into a roller press cooling bed; high-temperature flue gas accumulating at the top of the equipment and being transported to a boiler; after roller pressing, the steel slag is crushed in multiple stages to below 0.8 mm; room-temperature water in the boiler is heated into steam, which is used to generate electricity and sent back to the plant; the steel slag temperature is reduced to 300 ℃ and transported to the next workshop for magnetic separation to extract iron; the steel slag is mixed with water to obtain a slurry, which is simultaneously acid-leached and mechanically stirred; after acid leaching, the slurry is filtered to separate precipitate and leachate; after adjusting the pH of the leachate to 7.0-8.0, it is filtered again to obtain a phosphorus-rich precipitate. This method fully develops and utilizes the potential value of converter steel slag, establishes a green metallurgical process, and creates significant economic benefits.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical resource recycling technology, specifically a method for the comprehensive utilization of hot converter steel slag resources. Background Technology

[0002] Converter slag is a byproduct of the steelmaking process, accounting for approximately 10% to 13% of steel production. Due to the prevalence of the single-process steelmaking method in my country, the basicity of the steel slag is relatively high, resulting in the production of free CaO and MgO, which leads to a relatively low comprehensive utilization rate of steel slag in my country.

[0003] Currently, the main method of steel slag treatment involves cooling and crushing molten steel slag, followed by magnetic separation to separate the slag from the steel. The remaining tailings are used for building materials, road construction, or directly stockpiled. These methods fail to fully utilize the potential value of steel slag, resulting in significant resource waste and environmental pollution. Therefore, how to efficiently utilize steel slag is an urgent issue for steel companies to address.

[0004] The main mineral phases of converter steel slag are dicalcium ferrite, dicalcium silicate, iron-rich phase, and RO phase. The iron-rich phase can be recovered through crushing and magnetic separation. The dicalcium ferrite, dicalcium silicate, and RO phases are separated based on their different solubilities in water; dicalcium ferrite and RO phases are insoluble in water, while dicalcium silicate is soluble. The dephosphorization product, tricalcium phosphate, is mainly distributed in the dicalcium silicate phase. Therefore, the various components of converter steel slag can be separated, achieving comprehensive resource utilization.

[0005] Patent CN201910915782.4 discloses a method for the efficient resource utilization of converter steel slag. The specific content is as follows: First, the molten converter steel slag is oxidized to reduce the mass fraction of FeO in the slag. Then, the steel slag is mixed with an aqueous solution to obtain a slurry, and acid leaching is performed using an inorganic acid solution. The pH value of the slurry is controlled within the range of 2.0 to 3.0, causing the phosphorus-containing dicalcium silicate phase in the steel slag to dissolve and separate. After solid-liquid separation, the pH value of the leachate is adjusted to 7.5 to 8.5, causing the phosphate in the leachate to precipitate. The main purpose of this invention is to treat the steel slag; it does not recover the excess heat of the molten converter steel slag.

[0006] Patent CN201811650115.X discloses a method for the comprehensive utilization of steel slag resources. The specific content is as follows: Acid and an oxidant are added to the steel slag to dissolve it, converting the solid valuable elements into ionic states in water. After heating and stirring, solid-liquid separation is achieved. Then, an extractant is added, and a countercurrent two-stage extraction method is used to obtain an extract phase and a solution phase. The two phases are then separated, and the extract phase is processed to obtain metal elements and filtrate. The filtrate can be reused as an extractant. This invention only focuses on the utilization of the filtrate obtained from selective separation, failing to comprehensively consider the effective treatment of the filter residue, resulting in resource waste.

[0007] Patent CN202310523680.4 discloses a method for treating liquid steel slag from a steelmaking plant, specifically as follows: S1, a steel slag modifier is added to the liquid steel slag from the steelmaking plant, the mixture is heated to react, then cooled, filtered, and a primary treated product is obtained, with the solid retained; S2, a Si / C reducing agent is added to the primary treated product, microwave heating is performed, an inert gas containing CO is introduced, a reduction gasification reaction is initiated, the mixture is filtered, the solid is collected, the liquid steel slag is poured out and cooled, and the waste heat is recovered. Simultaneously with the waste heat recovery, the liquid steel slag naturally pulverizes and is sent to a magnetic separator to magnetically separate iron particles and recover tailings; S3, the solids from steps S1 and S2 are combined and used as a phosphorus-containing fertilizer. This invention requires the addition of a reducing agent to the primary treated product and subsequent heating treatment, making the process cumbersome and resulting in significant energy and heat waste. Summary of the Invention

[0008] This invention provides a method for the comprehensive utilization of converter steel slag resources. First, the high-temperature flue gas from the converter is used as a heat source to heat the room-temperature water in the boiler, converting thermal energy into electrical energy. Subsequently, the steel slag is ground and crushed, and then subjected to magnetic separation to extract iron. The tailings from the magnetic separation are acid-leached and then separated into solid and liquid components. The leachate is adjusted to a weakly alkaline state to obtain precipitate, thus realizing the resource conversion process of converter steel slag waste heat recovery, iron extraction, metallurgical flux, and phosphorus-rich products.

[0009] To achieve the above objectives, the present invention employs the following technical solution:

[0010] A method for comprehensive utilization of hot converter steel slag resources, the method comprising the following steps:

[0011] Step 1: The hot converter slag is quickly poured into the roller pressing cooling bed. After being pressed, the slag will generate a large amount of high-temperature flue gas. The flue gas is collected at the top of the equipment and transported to the boiler through a sealed pipeline. The pressed slag is then crushed in multiple stages to below 0.8 mm. High-temperature flue gas is still generated during this process and is also collected and transported to the boiler through a sealed pipeline. The high-temperature flue gas is used to heat the room-temperature water in the boiler into steam, which is then used to generate electricity. Finally, the electricity is fed back to the factory, achieving the goal of energy saving.

[0012] Furthermore, in step one, air cooling is used to reduce the heat consumed when water turns into water vapor during the water spray evaporation process.

[0013] Step 2: Reduce the temperature of the crushed steel slag described in Step 1 to 300 ℃ and transport it to the next workshop for magnetic separation to extract iron. The extracted iron can be reused in steelmaking, reducing iron loss and increasing the iron yield of the converter.

[0014] Step 3: Mix the remaining converter slag from Step 2 with water to obtain a slurry, and then perform acid leaching on the slurry while mechanically stirring it. The purpose of this is to improve the kinetic conditions of the acid leaching reaction and promote the dissolution of the dicalcium silicate phase. After acid leaching, the slurry is filtered to separate the precipitate and leachate. The dicalcium silicate phase in the converter slag precipitate has been dissolved and separated. The remaining dicalcium ferrite can be reused as a metallurgical flux in sintering or steelmaking.

[0015] Step 4: After adjusting the pH of the leachate obtained in Step 3 to 7.0-8.0, filter and separate it to obtain a phosphorus-rich precipitate. The precipitate is mainly composed of calcium phosphate salts and can be used directly as a raw material for phosphorus chemical industry or phosphate fertilizer.

[0016] Preferably, in step one, the temperature of the steel slag is 1300~1400 ℃.

[0017] Preferably, in step one, the waste heat recovered from each ton of steel slag can generate 53 to 65 kilowatt-hours of electricity.

[0018] Preferably, in step two, the MFe content in the steel slag after magnetic separation for iron extraction is less than 5%.

[0019] Preferably, in step three, chloric acid has oxidizing properties and can decompose the Fe in the acid leaching solution. 2+ Oxidized to Fe 3+ The solution is precipitated when the pH value is less than 3.0. The acid leaching solution is chloric acid solution, the pH value of the acid leaching solution is maintained at 1.5~2.5, the acid leaching temperature is 40~60 ℃, and the acid leaching time is 1~2 h.

[0020] Preferably, in step three, the precipitate is mainly composed of dicalcium ferrite, with a content of 75% to 84%.

[0021] Preferably, in step three, the leaching rate of iron in the leachate is less than 3.0%, which helps to separate the various elements in the steel slag.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects:

[0023] (1) The present invention proposes a method for comprehensive utilization of converter steel slag resources, which realizes the resource conversion process of converter steel slag waste heat recovery, iron extraction, metallurgical flux and phosphorus-rich products, fully develops and utilizes the potential value of converter steel slag, establishes a green metallurgical process, and creates huge economic benefits.

[0024] (2) While recovering the waste heat of steel slag to generate electricity, the present invention crushes the steel slag to a suitable particle size, which facilitates the application of subsequent processes and avoids the loss caused by secondary processing.

[0025] (3) This invention eliminates the need for blowing oxygen or air into molten steel slag to remove Fe 2+ Oxidized to Fe 3+Instead of using oxidation treatment methods, chloric acid is used as the leaching solution to achieve the same purpose, saving a lot of energy and improving production efficiency.

[0026] (4) This invention abandons the method of using steel slag as building or road material, and instead uses acid leaching extraction to separate different mineral phases of steel slag, thereby obtaining resource materials with better economic value. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of exemplary embodiments of the experimental method is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] Step 1: The steel slag, fresh from the converter, is 1400 ℃ and is quickly poured into the roller pressing cooling bed. After being pressed, the steel slag generates a large amount of high-temperature flue gas, which is collected at the top of the equipment and transported to the boiler through a sealed pipeline. After being pressed, the steel slag undergoes multiple stages of crushing to below 0.8 mm, generating high-temperature flue gas in the process, which is also collected and transported to the boiler through a sealed pipeline. The high-temperature flue gas is used to heat the room-temperature water in the boiler into steam, which is then used to generate electricity. Finally, the electricity is fed back to the factory. The waste heat recovered from each ton of steel slag can generate 65 kWh of electricity.

[0031] Step 2: Reduce the temperature of the crushed steel slag described in Step 1 to 300 ℃ and transport it to the next workshop for magnetic separation to extract iron. The MFe content in the steel slag is 1.5%. The chemical composition of the steel slag in this Example 1 is shown in Table 1.

[0032] Table 1. Chemical composition of converter steel slag in Example 1 (mass fraction / %)

[0033] 45.08 14.80 18.88 7.26 3.37 2.28 2.89 5.44

[0034] Step 3: Mix the remaining converter slag from Step 2 with water to obtain a slurry, and perform acid leaching using chloric acid solution at a temperature of 50 ℃ for 1.5 h with a pH value of 1.5~2.5. Simultaneously, mechanically stir the slurry. After acid leaching, filter the slurry to obtain precipitate and leachate. The leaching rate of iron in the leachate is 2.41%. The chemical composition of the precipitate is shown in Table 2, with a dicalcium ferrite content of 84%.

[0035] Table 2 Chemical composition of the precipitate in Example 1 (mass fraction / %)

[0036] 26.22 0.63 0.25 61.12 0.211 1.56 4.36 4.21

[0037] Step 4: After adjusting the pH of the leachate obtained in Step 3 to 7.0~8.0, filter and separate the precipitate, which is mainly composed of calcium phosphate salt. The chemical composition is shown in Table 3.

[0038] Table 3 Chemical composition of the precipitate in Example 1 (mass fraction / %)

[0039] 21.13 52.12 1.56 22.36 0.05 1.23 Example 2

[0040] Step 1: The steel slag, fresh from the converter, is 1300 ℃ and is quickly poured into the roller pressing cooling bed. After being pressed, the steel slag generates a large amount of high-temperature flue gas, which is collected at the top of the equipment and transported to the boiler through a sealed pipeline. After being pressed, the steel slag undergoes multiple stages of crushing to below 0.8 mm, generating high-temperature flue gas in the process, which is also collected and transported to the boiler through a sealed pipeline. The high-temperature flue gas is used to heat the room-temperature water in the boiler into steam, which is then used to generate electricity. Finally, the electricity is fed back to the factory. The waste heat recovered from each ton of steel slag can generate 53 kWh of electricity.

[0041] Step 2: Reduce the temperature of the crushed steel slag described in Step 1 to 300 ℃ and transport it to the next workshop for magnetic separation to extract iron. The MFe content in the steel slag is 2.1%. The chemical composition of the steel slag in this Example 2 is shown in Table 4.

[0042] Table 4 Chemical composition of converter steel slag in Example 2 (mass fraction / %)

[0043] 45.51 15.23 16.46 8.38 3.21 3.46 2.56 5.19

[0044] Step 3: Mix the remaining converter slag from Step 2 with water to obtain a slurry, and perform acid leaching using chloric acid solution at a temperature of 40 ℃ for 2 h with a pH of 1.5~2.5. Simultaneously, mechanically stir the slurry. After acid leaching, filter the slurry to obtain precipitate and leachate. The leaching rate of iron in the leachate is 1.89%, and the chemical composition of the precipitate is shown in Table 5, with a dicalcium ferrite content of 75%.

[0045] Table 5 Chemical composition of the precipitate in Example 2 (mass fraction / %)

[0046] 24.38 0.65 0.21 61.71 0.211 1.83 4.56 4.03

[0047] Step 4: After adjusting the pH of the leachate obtained in Step 3 to 7.0~8.0, filter and separate the precipitate, which is mainly composed of calcium phosphate salt. The chemical composition is shown in Table 6.

[0048] Table 6 Chemical composition of the precipitate in Example 2 (mass fraction / %)

[0049] 21.34 52.01 1.28 21.56 0.06 1.65

[0050] Example 3

[0051] Step 1: The steel slag, fresh from the converter, is 1350 ℃ and is quickly poured into the roller pressing cooling bed. After being pressed, the steel slag generates a large amount of high-temperature flue gas, which is collected at the top of the equipment and transported to the boiler through a sealed pipeline. After being pressed, the steel slag undergoes multi-stage crushing to below 0.8 mm, generating high-temperature flue gas in the process, which is also collected and transported to the boiler through a sealed pipeline. The high-temperature flue gas is used to heat the room-temperature water in the boiler into steam, which is then used to generate electricity. Finally, the electricity is fed back to the factory. The waste heat recovered from each ton of steel slag can generate 58 kWh of electricity.

[0052] Step 2: Reduce the temperature of the crushed steel slag described in Step 1 to 300 ℃ and transport it to the next workshop for magnetic separation to extract iron. The MFe content in the steel slag is 1.7%. The chemical composition of the steel slag in this Example 3 is shown in Table 7.

[0053] Table 7 Chemical composition of converter steel slag in Example 3 (mass fraction / %)

[0054] 44.45 18.25 14.21 9.33 2.31 3.89 2.25 5.31

[0055] Step 3: Mix the remaining converter slag from Step 2 with water to obtain a slurry, and perform acid leaching using chloric acid solution at a temperature of 60 ℃ for 1 h with a pH value of 1.5~2.5. Simultaneously, mechanically stir the slurry. After acid leaching, filter the slurry to obtain precipitate and leachate. The leaching rate of iron in the leachate is 2.11%. The chemical composition of the precipitate is shown in Table 8, with a dicalcium ferrite content of 78%.

[0056] Table 8 Chemical composition of the precipitate in Example 3 (mass fraction / %)

[0057] 25.23 0.59 0.24 62.35 0.225 1.88 4.12 4.22

[0058] Step 4: After adjusting the pH of the leachate obtained in Step 3 to 7.0~8.0, filter and separate the precipitate, which is mainly composed of calcium phosphate salt. The chemical composition is shown in Table 9.

[0059] Table 9 Chemical composition of the precipitate in Example 3 (mass fraction / %)

[0060] 21.56 52.33 1.35 22.11 0.08 1.44

Claims

1. A method for comprehensive utilization of hot-state converter steel slag resources, characterized in that, Includes the following steps: Step 1: The hot converter slag is quickly poured into the roller pressing cooling bed, generating a large amount of high-temperature flue gas. The flue gas accumulates at the top of the equipment and is transported to the boiler through pipelines. The roller-pressed slag is then crushed in multiple stages to below 0.8 mm, generating high-temperature flue gas in the process, which is also transported to the boiler through pipelines. The high-temperature flue gas is used to heat the room-temperature water in the boiler into steam, which is then used to generate electricity, and finally the electricity is fed back to the factory. Step 2: Reduce the temperature of the crushed steel slag described in Step 1 to 300 ℃ and transport it to the next workshop for magnetic separation to extract iron. The extracted iron can be reused in steelmaking. Step 3: Mix the remaining converter slag from Step 2 with water to obtain a slurry, and then perform acid leaching on the slurry while mechanically stirring. After acid leaching, the slurry is filtered to separate the precipitate and leachate. The dicalcium ferrite in the precipitate can be reused as a metallurgical flux. Step 4: Adjust the pH of the leachate from Step 3 to 7.0-8.0, then filter and separate to obtain a phosphorus-rich precipitate.

2. The method for comprehensive utilization of hot converter steel slag resources according to claim 1, characterized in that, In step one, the temperature of the steel slag is 1300~1400 ℃.

3. The method for comprehensive utilization of hot converter steel slag resources according to claim 1, characterized in that, In step one, the waste heat recovered from each ton of steel slag can generate 53 to 65 kilowatt-hours of electricity.

4. The method for comprehensive utilization of hot converter steel slag resources according to claim 1, characterized in that, In step two, the MFe content in the steel slag after magnetic separation and iron extraction is less than 5%.

5. The method for comprehensive utilization of hot converter steel slag resources according to claim 1, characterized in that, In step three, chloric acid solution is selected as the pickling solution, the pH value of the pickling solution is maintained at 1.5~2.5, the pickling temperature is 40~60 ℃, and the pickling time is 1~2 h.

6. The method for comprehensive utilization of hot converter steel slag resources according to claim 1, characterized in that, In step three, the precipitate is mainly composed of dicalcium ferrite, with a content of 75% to 84%.

7. The method for comprehensive utilization of hot converter steel slag resources according to claim 1, characterized in that, In step three, the iron leaching rate in the leachate is less than 3.0%.