Oxidized slag composition and method of forming same

Abstract

An oxide slag composition comprises: 20 to 36 parts by weight of calcium oxide, 14 to 18 parts by weight of silicon oxide, 18 to 23 parts by weight of aluminum oxide, 7 to 8.5 parts by weight of magnesium oxide, and 20 to 36 parts by weight of iron oxide. The ratio of the total weight of calcium oxide, aluminum oxide, and magnesium oxide to the weight of silicon oxide is 2.6 to 4.6. A method for forming the oxide slag composition includes the following steps: introducing a slag-forming agent composition and scrap steel into an electric arc furnace for steelmaking and smelting to form molten oxide slag; forming an oxide slag foam layer on the surface of the molten oxide slag; and cooling the oxide slag foam layer to obtain the oxide slag composition.

Description

Technical Field

[0001] This invention relates to oxidized slag compositions and methods for forming the same, particularly oxidized slag compositions with high foaming life and methods for forming the same. Background Technology

[0002] In existing electric arc furnace steelmaking technologies, energy utilization efficiency remains a significant challenge. Although a large amount of energy is input into the electric arc furnace to obtain molten steel, only about 50% of the total input energy is actually used for molten steel. The remaining energy is lost due to various factors, including electrical energy loss, slag heat loss, cooling water heat loss, radiant heat loss, and waste gas heat loss.

[0003] These heat losses not only lead to decreased energy efficiency, but the high-temperature exhaust gases and electric arcs generated during steelmaking also cause varying degrees of damage to the furnace. This damage includes, for example, the high-temperature exhaust gases eroding the exhaust pipes and corroding the furnace tube walls, causing water leakage in the electric arc furnace; the electric arc penetrating the furnace cover wall also causes water leakage problems. Furthermore, molten steel may adhere to the furnace cover due to splashing, gradually eroding the cover material and shortening the furnace's service life.

[0004] Therefore, how to effectively reduce energy loss and extend the life of electric arc furnaces has become an important issue that the industry urgently needs to address. Summary of the Invention

[0005] To improve the aforementioned problems of energy loss and damage to electric arc furnaces, the present invention provides an oxidation slag composition and a method for forming the same.

[0006] An embodiment of the present invention provides an oxidation slag composition comprising: 20 to 36 parts by weight of calcium oxide (CaO), 14 to 18 parts by weight of silicon oxide (SiO2), 18 to 23 parts by weight of aluminum oxide (Al2O3), 7 to 8.5 parts by weight of magnesium oxide (MgO), and 20 to 36 parts by weight of iron oxide (FeO). The ratio of the total weight parts of calcium oxide, aluminum oxide, and magnesium oxide to the weight parts of silicon oxide is 2.6 to 4.6.

[0007] Another embodiment of the present invention provides a method for forming an oxide slag composition, comprising: introducing a slag-forming agent composition and scrap steel into an electric arc furnace for steelmaking and smelting to form a slag precursor and molten steel, wherein the slag precursor is suspended on the molten steel; heating the slag precursor to react and form a molten oxide slag; reacting the molten oxide slag in the presence of a reducing agent to form carbon monoxide gas, wherein the carbon monoxide gas causes an oxide slag foaming layer to form on the surface of the molten oxide slag; and cooling the oxide slag foaming layer to obtain an oxide slag composition.

[0008] The oxidized slag composition of the present invention can maintain a foamed state in the furnace for a long time, thereby reducing heat loss and protecting the furnace at the same time.

[0009] The effects of the present invention are not limited to those mentioned above, and those skilled in the art to which this invention pertains will clearly understand from the following description the effects not mentioned above. Attached Figure Description

[0010] Figure 1 This is a flowchart of a method for forming an oxide slag composition according to an embodiment of the present invention.

[0011] Figure 2 The image shows the XRD pattern of the crystalline phase of the oxide slag composition in the embodiments and comparative examples of the present invention.

[0012] Figure 3 This is a bar chart showing the foaming life of the oxidized slag foaming layer in the embodiments and comparative examples of the present invention.

[0013] Symbol Explanation

[0014] S101, S102, S103, S104: Steps Detailed Implementation

[0015] The following embodiments describe in detail the features and advantages of the present invention, the content of which is sufficient to enable anyone skilled in the art to understand the technical content of the present invention and implement it accordingly. Based on the disclosure of this specification, the claims, and the drawings, anyone skilled in the art can easily understand the related objects and advantages of the present invention. The following embodiments are for further detailed explanation of the aspects of the present invention, but are not intended to limit the scope of the present invention in any way.

[0016] The oxidation slag composition and its formation method of the present invention will be described in detail below.

[0017] In one embodiment of the present invention, the oxide slag composition comprises: 20 to 36 parts by weight of calcium oxide (CaO), 14 to 18 parts by weight of silicon oxide (SiO2), 18 to 23 parts by weight of aluminum oxide (Al2O3), 7 to 8.5 parts by weight of magnesium oxide (MgO), and 20 to 36 parts by weight of iron oxide (FeO). The ratio of the total weight parts of calcium oxide, aluminum oxide, and magnesium oxide to the weight parts of silicon oxide is 2.6 to 4.6.

[0018] In some embodiments, the basicity of the oxidized slag composition may be 1.3 to 2.5. In some embodiments, the ratio of the total weight parts of calcium oxide (CaO), aluminum oxide (Al2O3), and magnesium oxide (MgO) to the weight parts of silicon oxide (SiO2) may be 2.7 to 4.5. In some embodiments, calcium oxide (CaO) may be 21 to 36 parts by weight, silicon oxide (SiO2) may be 14.5 to 17 parts by weight, aluminum oxide (Al2O3) may be 18 to 22 parts by weight, magnesium oxide (MgO) may be 7.5 to 8.5 parts by weight, and iron oxide may be 21 to 36 parts by weight. In some embodiments, the oxide slag composition may have a crystalline phase comprising: 5% to 25% calcium aluminosilicate (Ca2Al2SiO7) crystal structure, 10% to 25% calcium silicate (Ca2SiO4) crystal structure, and 60% to 80% iron oxide (FeO) crystal structure. In other embodiments, the crystalline phase may have: a calcium aluminosilicate (Ca2Al2SiO7) crystal structure with an X-ray diffraction peak integral area of ​​5 to 25, a calcium silicate (Ca2SiO4) crystal structure with an X-ray diffraction peak integral area of ​​10 to 25, and an iron oxide (FeO) crystal structure with an X-ray diffraction peak integral area of ​​60 to 80.

[0019] Figure 1 This is a flowchart of a method for forming an oxide slag composition according to an embodiment of the present invention.

[0020] like Figure 1 As shown, in one embodiment of the present invention, the method for forming an oxide slag composition includes: introducing a slag-forming agent composition and scrap steel into an electric arc furnace for steelmaking and smelting to form a slag precursor and molten steel, wherein the slag precursor is suspended on the molten steel (step S101); heating the slag precursor to react and form a molten oxide slag (step S102); reacting the molten oxide slag in the presence of a reducing agent to form carbon monoxide gas, wherein the carbon monoxide gas causes an oxide slag foaming layer to form on the surface of the molten oxide slag (step S103); and cooling the oxide slag foaming layer to obtain an oxide slag composition (step S104).

[0021] First, the slag-forming agent composition and scrap steel are introduced into an electric arc furnace for steelmaking and smelting to form a slag precursor and molten steel, with the slag precursor suspended on the molten steel (step S101). In some embodiments, the slag-forming agent composition may be 20 to 40 parts by weight of aluminum silicate, 15 to 20 parts by weight of bauxite, 30 to 50 parts by weight of quicklime, 5 to 10 parts by weight of iron oxide, and 5 to 10 parts by weight of magnesia. The scrap steel may contain carbon steel, alloy steel, direct reduced iron, or a combination thereof. The amount of slag-forming agent composition added is 5% to 15% (e.g., 7%, 9%, 11%, 12%, 13%, or 14%) of the scrap steel by weight.

[0022] Next, the slag precursor is heated to react and form a molten oxide slag (step S102). Specifically, the slag precursor is heated to a temperature of 1400°C to 1800°C (e.g., 1500°C, 1600°C, or 1700°C) to melt the slag precursor and form a molten oxide slag. After reacting with the following formulas (1) and (2), calcium silicate (Ca2SiO4) and calcium aluminosilicate (Ca2Al2SiO7) are generated. At this time, the oxide slag is a molten single-phase oxide slag.

[0023] Equation (1): 2CaO(s) + SiO2(l) → Ca2SiO4(l)

[0024] Equation (2) CaO(s) + Al2O3(s) + SiO2(l) → Ca2Al2SiO7(l)

[0025] Next, in the presence of a reducing agent, the molten slag reacts to form carbon monoxide gas, and the carbon monoxide gas causes a foamed slag layer to form on the surface of the molten slag (step S103). The reducing agent may include coke, coal, coal gas, natural gas, or a combination thereof. For example, the foamed slag layer (also known as foamed slag) is achieved by injecting carbon powder. After the carbon powder enters the molten pool, the iron oxide in the molten slag reacts with equation (4) to generate iron and carbon monoxide. At this time, the carbon monoxide gas generated by the reaction forms bubbles in the molten slag to form the foamed slag layer.

[0026] Formula (4)FeO(l)+C(s)→Fe(l)+CO(g)

[0027] The oxidized slag foam layer has good heat insulation properties, which can reduce heat loss. Furthermore, the oxidized slag foam layer covering the molten pool can effectively shield the high-temperature energy of the electric arc radiation and buffer the mechanical impact of the electric arc on the furnace, thus protecting the furnace.

[0028] Finally, the oxidized slag foaming layer is cooled to obtain the oxidized slag composition (step S104). Specifically, the oxidized slag foaming layer, after cooling, becomes the aforementioned oxidized slag composition. In some embodiments, after sampling the molten oxidized slag, it is placed in the atmosphere to cool, and the process takes about 5 hours to cool from the molten state to 50°C before sampling. The basicity of the oxidized slag composition is 1.3 to 2.5, and the basicity (C / S) is the ratio of calcium oxide content to silica content (calcium oxide content / silica content). The oxidation index of the oxidized slag composition is 2.6 to 4.6, and the oxidation index is the ratio of the total weight parts of calcium oxide (CaO), aluminum oxide (Al2O3), and magnesium oxide (MgO) to the weight parts of silica (SiO2). In some embodiments, the oxidation index of the oxidized slag composition may be 2.7 to 4.5. In some embodiments, the oxide slag composition may comprise: 20 to 36 parts by weight of calcium oxide, 14 to 18 parts by weight of silicon oxide, 18 to 23 parts by weight of aluminum oxide, 7 to 8.5 parts by weight of magnesium oxide, and 20 to 36 parts by weight of iron oxide. In some embodiments, the oxide slag composition may comprise: 21 to 36 parts by weight of calcium oxide, 14.5 to 17 parts by weight of silicon oxide, 18 to 22 parts by weight of aluminum oxide, 7.5 to 8.5 parts by weight of magnesium oxide, and 21 to 36 parts by weight of iron oxide. In some embodiments, the oxide slag composition may comprise: 24.5 to 30.9 parts by weight of calcium oxide, 14.8 to 15.3 parts by weight of silicon oxide, 20.1 to 20.6 parts by weight of aluminum oxide, 8.2 to 8.4 parts by weight of magnesium oxide, and 26.0 to 31.2 parts by weight of iron oxide. In the foregoing embodiments, the composition of the oxide slag composition may be the composition obtained after quantitative analysis of oxides using X-ray fluorescence spectrometry.

[0029] In some embodiments, the method for forming the oxide slag composition may further include: after step S102, subjecting the molten oxide slag to a gas-blowing reaction in the presence of air to form iron oxide. Specifically, gas (e.g., oxygen, nitrogen, or air) is blown into an electric arc furnace to oxidize and remove impurities such as silicon, manganese, and phosphorus in the molten steel, while simultaneously oxidizing part of the molten steel to produce iron oxide (FeO), as shown in formula (3).

[0030] Equation (3) 2Fe(l) + O2(g) → 2FeO(l)

[0031] The method for forming the oxide slag composition of the present invention produces an oxide slag foamed layer during the process, which has good heat insulation properties and can reduce heat loss. Furthermore, the oxide slag foamed layer covering the molten pool can effectively shield the high-temperature energy of the electric arc radiation and buffer the mechanical impact of the electric arc on the furnace, thus protecting the furnace. Therefore, the method for forming the oxide slag composition of the present invention is also a method for protecting furnaces or reducing energy consumption.

[0032] The embodiments and comparative examples of the present invention will be described in detail below.

[0033] According to the method for forming the oxide slag composition of the present invention, a slag-forming agent composition is added to form an oxide slag foaming layer in an electric arc furnace, and the oxide slag foaming layer, after cooling, becomes the oxide slag composition. The slag-forming agent composition can be obtained by mixing 20 to 40 parts by weight of aluminum silicate, 15 to 20 parts by weight of bauxite, 30 to 50 parts by weight of quicklime, 5 to 10 parts by weight of iron oxide, and 5 to 10 parts by weight of magnesia. The amount of slag-forming agent composition added is 12% of the weight of scrap steel.

[0034] The composition of the oxidized slag compositions obtained in each embodiment and comparative example was measured and analyzed by X-ray fluorescence spectrometry (XRF), and the crystalline phase was measured and analyzed by X-ray diffraction (XRD). The results are shown in Table 1. Figure 2 and Figure 3 As shown.

[0035] Table 1. Composition, foaming life, and structure of the oxide slag compositions in each embodiment and comparative example.

[0036]

[0037] *Alkalinity (C / S) = Calcium oxide content / Silicon dioxide content.

[0038] *Oxidation index (x) = Total weight parts of calcium oxide (CaO), aluminum oxide (Al2O3), and magnesium oxide (MgO) / Weight parts of silicon oxide (SiO2).

[0039] from Figure 2 , Figure 3As shown in Table 1, the crystalline phase of the oxide slag composition includes calcium aluminosilicate, calcium silicate, and iron oxide. When the basicity is below 1.3 and the oxidation index is below 2.6 (e.g., Comparative Example 1), the oxide slag under this condition is acidic due to its high silica content. Its excessively high surface tension is detrimental to foaming, resulting in a short foaming life (less than 8 minutes). When the basicity is above 2.5 and the oxidation index is above 4.6 (e.g., Comparative Example 2), the calcium silicate content is high. Since calcium silicate is a metastable phase formed by the silica network structure and calcium oxide at high temperatures, excessive calcium oxide will destroy the silica network structure, resulting in a short foaming life (less than 8 minutes).

[0040] However, when the alkalinity is 1.3 to 2.5, the oxidation index is 2.6 to 4.6, and the crystalline phase comprises 5% to 25% calcium aluminosilicate crystal structure, 10% to 25% calcium silicate crystal structure, and 60% to 80% iron oxide crystal structure (e.g., Examples 1 to 4), the foaming life of the oxide slag foaming layer is 8 to 20 minutes. Specifically, when the oxide slag foaming layer comprises 24.5 to 30.9 parts by weight of calcium oxide, 14.8 to 15.3 parts by weight of silicon oxide, 20.1 to 20.6 parts by weight of aluminum oxide, 8.2 to 8.4 parts by weight of magnesium oxide, and 26.0 to 31.2 parts by weight of iron oxide (e.g., Examples 2 and 3), the foaming life of the oxide slag foaming layer is 12 to 18 minutes. The longer foaming life of the oxide slag foaming layer can more effectively reduce heat loss and protect the furnace.

[0041] In summary, the oxide slag composition of the present invention maintains a long foaming life due to its specific component ratio, thereby achieving better heat loss reduction and furnace protection in the molten state. Furthermore, this oxide slag composition also possesses a specific structure and proportion of crystalline phases after cooling. In addition, the method for forming the oxide slag composition of the present invention involves adding the slagging agent composition of the present invention during smelting to melt the scrap steel with the slagging agent composition, and forming an oxide slag foam layer with a high foaming life under the action of carbon monoxide, thereby achieving the effects of reducing heat loss and protecting the furnace.

Claims

1. An oxidation slag composition comprising: 20 to 36 parts by weight of calcium oxide (CaO); 14 to 18 parts by weight of silicon dioxide (SiO2); 18 to 23 parts by weight of aluminum oxide (Al2O3); 7 to 8.5 parts by weight of magnesium oxide (MgO); and 20 to 36 parts by weight of iron oxide (FeO), The ratio of the total weight parts of calcium oxide (CaO), aluminum oxide (Al2O3), and magnesium oxide (MgO) to the weight parts of silicon oxide (SiO2) is 2.6 to 4.

6.

2. The oxide slag composition according to claim 1, wherein the basicity of the oxide slag composition is 1.3 to 2.

5.

3. The oxide slag composition according to claim 1, wherein the total weight parts of calcium oxide (CaO), aluminum oxide (Al2O3) and magnesium oxide (MgO) are in a weight ratio of 2.7 to 4.5 to silicon oxide (SiO2).

4. The oxide slag composition according to claim 1, wherein calcium oxide (CaO) is 21 to 36 parts by weight, silicon oxide (SiO2) is 14.5 to 17 parts by weight, aluminum oxide (Al2O3) is 18 to 22 parts by weight, magnesium oxide (MgO) is 7.5 to 8.5 parts by weight, and iron oxide is 21 to 36 parts by weight.

5. The oxidation slag composition according to claim 1, comprising a crystalline phase, wherein the crystalline phase has: 5% to 25% of calcium aluminosilicate (Ca2Al2SiO7) crystal structure; Calcium silicate (Ca2SiO4) crystal structure of 10% to 25%; and It has a 60% to 80% iron oxide (FeO) crystal structure.

6. A method for forming an oxidation slag composition, comprising: The slag-forming agent composition and scrap steel are introduced into an electric arc furnace for steelmaking and smelting to form a slag precursor and molten steel, wherein the slag precursor is suspended on the molten steel. The slag precursor is heated to react and form a molten oxide slag. In the presence of a reducing agent, the molten oxide slag reacts to form carbon monoxide gas, and the carbon monoxide gas causes an oxide slag foaming layer to form on the surface of the molten oxide slag. as well as The oxidized slag foam layer is cooled to obtain the oxidized slag composition of claim 1.

7. The method for forming the oxide slag composition according to claim 6, wherein the temperature for heating the slag precursor is 1400°C to 1800°C.

8. The method for forming the oxidized slag composition according to claim 6, wherein the scrap steel comprises carbon steel, alloy steel, direct reduced iron, or a combination thereof.

9. The method for forming the oxidized slag composition according to claim 6, wherein the reducing substance comprises coke, coal, coal gas, natural gas, or a combination thereof.

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