Recycling treatment method for converter steel slag

Abstract

The invention relates to a converter steel slag recycling treatment method which comprises the following steps: pouring cold-state or hot-state converter steel slag into a submerged arc furnace, and adding iron ore concentrate powder at the same time, so that the mass ratio of FeO to SiO2 in the slag is (2.5-3.5): 1; lowering the electrode to start heating, and raising the electrode when the fluidity of the slag is good; coke powder is added into the high-temperature area of the molten slag in batches, and the mass ratio of Mc to Mo in the molten slag is (1.6-1.9): 1; mc is the mass of the coke powder, and Mo is the total oxygen mass in the slag; blowing nitrogen or argon to the surface of the molten pool; discharging the iron liquid containing silicon and manganese, and casting to obtain an iron alloy; and the converter body is tilted to pour out slag which is the slagging raw material for converter steelmaking. The method has the advantages that most of P and S elements in the converter steel slag can be removed, CaO, MgO, FeO and SiO2 are recycled, and cyclic utilization of the steel slag is achieved.

Description

Technical Field

[0001] The invention belongs to the field of steel slag treatment, and in particular relates to a recycling treatment method for converter steel slag. Background Art

[0002] Converter slag poses several environmental risks: large accumulations of slag occupy and pollute land, heavy metals in the slag are washed away by rainwater and cause water pollution, and dust from slag piles affects air quality. Furthermore, slag contains a wealth of valuable resources, such as calcium, iron, and silicon. Effective utilization can conserve resources and reduce the exploitation of natural resources.

[0003] Adopt modern processing technology can be used as the raw material of making cement, glass, paving stone etc. by converter slag, but processing cost is high and recovery value is low.If the CaO, MgO etc. in converter slag are recycled as converter smelting slag raw material, with FeO, SiO2 etc. in slag and be recycled as steel material and silicon alloy, will produce great economic benefit.But there is no effective method at present that phosphorus and silicon oxide (existing with the form of calcium phosphate and calcium silicate respectively) in slag are removed from slag, thereby cause converter slag to be unable to recycle, and this difficult problem is not effectively solved all the time.For this reason, people have made many attempts, but all without obvious effect.

[0004] Patent publication number CN118702430A discloses a method for producing environmentally friendly building materials using steel slag, including the following steps: S1. Pretreatment: Liquid steel slag is sprayed with high-pressure air and cooled to form steel slag particles, which are then modified to produce modified steel slag microbeads; S2. Mixing: The modified steel slag microbeads, desulfurized gypsum powder, and fly ash are uniformly mixed to produce a mixture; S3. Slurrying: Water is added to the mixture and uniformly mixed to produce the building material. This method uses an air quenching process to produce steel slag particles. The free calcium oxide in the steel slag is degraded by the high-pressure air, and the steel slag particles are modified, improving the bonding between the steel slag and other fillers and increasing the strength of the building material. Patent publication number CN118908607A discloses a composite steel slag activator-modified steel slag material and its preparation method. The composite steel slag activator-modified steel slag material is composed of the following raw materials by weight: 86-93 parts steel slag, 4-7 parts desulfurized gypsum, 1-2 parts sodium silicate, 0.2-0.4 parts polyol amine, 0.5-1 part polyol, 0.2-0.5 parts calcium dihydrogen phosphate, and 0.1-0.3 parts corrosion enhancer. The corrosion enhancer exhibits excellent thermal stability and chemical stability due to its numerous carbon-fluorine bonds, which impart excellent alkali resistance to the steel slag material. Furthermore, the thiazole structure allows for the formation of stable complexes with metal ions in the steel slag material, resulting in a comprehensive bond. After mixing the steel slag material with cement, the compressive strength of the base material is significantly improved compared to steel slag treated with commercially available steel slag activators, and the material exhibits excellent stability. The above technical solutions all add gypsum, sodium silicate, etc. to steel slag to make it suitable for use as cement or cement base material. It can be seen that its processing cost is high and its recycling value cannot be greatly improved, and it is far from achieving the ideal effect. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a method for recycling converter slag, which can remove most of the P and S elements in the converter slag and recover components such as CaO, MgO, FeO, SiO2 for use as metallurgical slag materials and ferrosilicon alloys, and can be produced on an industrial scale.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A method for recycling converter slag comprises the following steps:

[0008] 1) Pour cold or hot converter slag into a submerged arc furnace and add iron ore powder to make the mass ratio of FeO to SiO2 in the slag (2.5-3.5):1;

[0009] 2) Lower the electrode and start heating. Raise the electrode after the slag is completely melted and has good fluidity.

[0010] 3) Add coke powder to the high temperature area of ​​slag in batches to make the mass ratio of M in slag c :M o (1.6~1.9):1;M c is the mass of coke powder, M o is the total oxygen mass in the slag;

[0011] M o =0.22M FeO +0.53M siO2 +0.45M MnO +0.44M P2O5 ;

[0012] Where: M FeO 、M siO2 、M MnO and M P2O5 are the masses of FeO, SiO2, MnO and P2O5 in the slag respectively;

[0013] Coke powder is added in batches to the high-temperature area of ​​the slag. Each time a batch of coke powder is added, the electrode is lowered and heated again to make the slag completely melted and have good fluidity. At the same time, nitrogen or argon is blown to the surface of the molten pool to isolate the oxygen in the air and form a reducing atmosphere. Most of the phosphorus and sulfur elements in the slag are reduced and gasified and removed. Most of the iron, silicon and manganese elements are reduced and melted to form molten iron containing silicon and manganese, which is deposited at the bottom of the submerged arc furnace.

[0014] 4) Open the furnace outlet to release the molten iron containing silicon and manganese, and then cast it to obtain the ferroalloy;

[0015] 5) The slag is poured out from the tilting furnace body and can be used as slag-making raw material for converter steelmaking.

[0016] The slag after smelting in step 4) includes the following components: CaO, MgO, Al2O3, and coke.

[0017] The converter slag described in step 1) includes the following components: CaSiO3, Ca3(PO4)2, Fe2O3, FeO, CaS, CaO, MgO, and Al2O3.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention can remove most of the P and S elements in the converter slag and recover components such as CaO, MgO, FeO, and SiO2. Iron and silicon are reduced and melted to form ferrosilicon alloy, which can be used as an alloy for steelmaking, thereby realizing high value-added utilization of the main metal elements in the slag. At the same time, the slag after smelting can be used as a slag-making raw material for converter steelmaking, thereby realizing the recycling of the slag, reducing the storage and discharge of the slag, and improving resource utilization.

[0020] The method of the present invention has a short converter slag treatment time, can adapt to the steelmaking production rhythm, realizes industrial-scale production, and will produce great economic and environmental benefits. DETAILED DESCRIPTION

[0021] The present invention will be described in detail below, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0022] A method for recycling converter slag comprises the following steps:

[0023] 1) Cold or hot converter slag is poured into a submerged arc furnace, and iron ore powder is added at the same time so that the mass ratio of FeO to SiO2 in the slag is (2.5-3.5):1; wherein the converter slag includes the following components: CaSiO3, Ca3(PO4)2, Fe2O3, FeO, CaS, CaO, MgO, and Al2O3.

[0024] 2) Lower the electrode and start heating. Raise the electrode after the slag is completely melted and has good fluidity.

[0025] 3) Add coke powder to the high temperature area of ​​slag in batches to make the mass ratio of M in slag c :M o (1.6~1.9):1;M c is the mass of coke powder, M o is the total oxygen mass in the slag;

[0026] M o =0.22M FeO +0.53M siO2 +0.45M MnO +0.44M P2O5 ;

[0027] Where: M FeO 、M siO2 、M MnO and M P2O5 are the masses of FeO, SiO2, MnO and P2O5 in the slag respectively;

[0028] Coke powder is added in batches to the high-temperature area of ​​the slag. Each time a batch of coke powder is added, the electrode is lowered and heated again to make the slag completely melted and have good fluidity. At the same time, nitrogen or argon is blown to the surface of the molten pool to isolate the oxygen in the air and form a reducing atmosphere. Most of the phosphorus and sulfur elements in the slag are reduced and gasified and removed. Most of the iron, silicon and manganese elements are reduced and melted to form molten iron containing silicon and manganese, which is deposited at the bottom of the submerged arc furnace.

[0029] The following chemical reactions take place in the molten pool:

[0030] Ca3(PO4)2+5C→3CaO+2P↑+5CO↑;

[0031] CaSiO3+3C→CaO+Si+3CO↑;

[0032] Fe2O3+3C→2Fe+3CO↑;

[0033] FeO+C→Fe+CO↑;

[0034] CaS+C→S↑+CaC;

[0035] MnO+C→Mn+CO↑;

[0036] Most of the phosphorus and sulfur elements in the slag are reduced and gasified and removed, and most of the iron and silicon elements are reduced and melted to form iron and silicon melts deposited at the bottom of the submerged arc furnace; the slag after smelting includes the following components: CaO, MgO, Al2O3, and coke.

[0037] 4) Open the furnace outlet to release the molten iron containing silicon and manganese, and then cast it to obtain the ferroalloy;

[0038] 5) The slag is poured out from the tilting furnace body and can be used as slag-making raw material for converter steelmaking.

[0039] Example 1:

[0040] Recycling of 150 tons of hot converter slag, including:

[0041] 1) The temperature of the hot converter slag is 1050°C, and its chemical composition is shown in Table 1.

[0042] Table 1 Converter slag composition (by mass percentage)

[0043] CaO <![CDATA[SiO2]]> FeO MgO MnO S <![CDATA[AL2O3]]> <![CDATA[P2O5]]> 51.09％ 16.28％ 18.63％ 8.99％ 1.59％ 0.033％ 0.88％ 1.9％

[0044] 2) Pour the hot converter slag into the submerged arc furnace and add 35 tons of iron ore powder;

[0045] 3) Lower the electrode and start heating, and raise the electrode when the slag has good fluidity;

[0046] 4) Add a total of 36.45 tons of coke powder to the high-temperature zone of the slag in 10 batches, 3.645 tons per batch. After each batch of coke powder is added, lower the electrode and heat it again. Simultaneously, blow nitrogen gas onto the surface of the molten pool to isolate the oxygen in the air and create a reducing atmosphere.

[0047] 5) A chemical reaction occurs in the slag. Most of the phosphorus and sulfur elements in the slag are reduced and gasified and removed. Most of the iron and silicon elements are reduced and melted to form iron and silicon melts that are deposited at the bottom of the submerged arc furnace.

[0048] 6) The furnace outlet was opened to release the iron and silicon melt, and then cast to obtain 35 tons of ferrosilicon alloy with a silicon content [Si] of 34%, [P] of 0.03%, [S] of 0.01%, and [Mn] of 3.6%.

[0049] 7) Tilt the furnace body to pour out the slag. The main components of the slag after smelting are CaO, MgO, Al2O3, residual coke, etc.

[0050] Example 2:

[0051] Recycling of 130 tons of cold BC slag, including:

[0052] 1) The temperature of cold massive converter slag is 20°C, and its chemical composition is shown in Table 2.

[0053] Table 2 Converter slag composition (by mass percentage)

[0054] CaO <![CDATA[SiO2]]> FeO MgO MnO S <![CDATA[AL2O3]]> <![CDATA[P2O5]]> 46.37％ 13.99％ 17.95％ 9.56％ 1.82％ 0.032％ 4.46％ 1.42％

[0055] 2) Pour cold converter slag into the submerged arc furnace and add 31 tons of iron ore powder;

[0056] 3) Lower the electrode and start heating, and raise the electrode when the slag has good fluidity;

[0057] 4) Add a total of 31 tons of coke powder to the high-temperature zone of the slag in 10 batches, 3.1 tons per batch. After each batch of coke powder is added, lower the electrode and heat it again. Simultaneously, blow nitrogen gas onto the surface of the molten pool to isolate the oxygen in the air and create a reducing atmosphere.

[0058] 5) A chemical reaction occurs in the slag. Most of the phosphorus and sulfur elements in the slag are reduced and gasified and removed. Most of the iron and silicon elements are reduced and melted to form iron and silicon melts that are deposited at the bottom of the submerged arc furnace.

[0059] 6) The furnace outlet was opened to release the iron and silicon melt, and then cast to obtain 30 tons of ferrosilicon alloy with a silicon content [Si] of 34%, [P] of 0.031%, [S] of 0.012%, and [Mn] of 3.6%.

[0060] 7) Tilt the furnace body to pour out the slag. The main components of the slag after smelting are CaO, MgO, Al2O3, residual coke, etc.

[0061] The present invention can remove most of the P and S elements in the converter slag and recover components such as CaO, MgO, FeO, and SiO2. Iron and silicon are reduced and melted to form ferrosilicon alloy, which can be used as an alloy for steelmaking, thereby realizing high value-added utilization of the main metal elements in the slag. At the same time, the slag after smelting can be used as a slag-making raw material for converter steelmaking, thereby realizing the recycling of the slag, reducing the storage and discharge of the slag, and improving resource utilization.

Claims

1. A method for recycling converter slag, characterized in that: The following steps are involved: 1) Pour cold or hot converter slag into a submerged arc furnace and add iron ore powder to make the mass ratio of FeO to SiO2 in the slag (2.5-3.5):1; 2) Lower the electrode and start heating. Raise the electrode after the slag is completely melted and has good fluidity. 3) Add coke powder to the high temperature area of ​​slag in batches to make the mass ratio of M in slag c :M o (1.6~1.9):1;M c is the mass of coke powder, M o is the total oxygen mass in the slag; M o =0.22M FeO +0.53M siO2 +0.45M MnO +0.44M P2O5 ; Where: M FeO 、M siO2 、M MnO and M P2O5 are the masses of FeO, SiO2, MnO and P2O5 in the slag respectively; Coke powder is added in batches to the high-temperature area of ​​the slag. Each time a batch of coke powder is added, the electrode is lowered and heated again to make the slag completely melted and have good fluidity. At the same time, nitrogen or argon is blown to the surface of the molten pool to isolate the oxygen in the air and form a reducing atmosphere. Most of the phosphorus and sulfur elements in the slag are reduced and gasified and removed. Most of the iron, silicon and manganese elements are reduced and melted to form molten iron containing silicon and manganese, which is deposited at the bottom of the submerged arc furnace. 4) Open the furnace outlet to release the molten iron containing silicon and manganese, and then cast it to obtain the ferroalloy; 5) The slag is poured out from the tilting furnace body and can be used as slag-making raw material for converter steelmaking.

2. The method for recycling converter slag according to claim 1, characterized in that: The slag after smelting in step 4) includes the following components: CaO, MgO, Al2O3, and coke.

3. The method for recycling converter slag according to claim 1, characterized in that: The converter slag described in step 1) includes the following components: CaSiO3, Ca3(PO4)2, Fe2O3, FeO, CaS, CaO, MgO, and Al2O3.