Method for obtaining low-iron white steel slag

Abstract

The invention relates to the technical field of treatment of steelmaking wastes, in particular to a method for obtaining low-iron white steel slag, which comprises the following steps: carrying out crushing, screening and magnetic separation on steel slag, and grinding magnetic separation residues again until all materials pass through a screen to obtain steel slag powder; carrying out first acidolysis on the steel slag powder, and carrying out solid-liquid separation on the obtained reaction product to obtain a first liquid material and a first solid material; the first solid material is subjected to second acidolysis, an obtained reaction product is subjected to solid-liquid separation, a second liquid material and a second solid material are obtained, the second liquid material is subjected to cooling crystallization and solid-liquid separation, CaCl2 crystals are obtained, and a mixture of the second solid material and the CaCl2 crystals is iron-removed steel slag. According to the method disclosed by the invention, the elemental iron, the ferrous iron and the ferric iron in the steel slag can be sequentially and respectively removed, so that the iron element in the steel slag is completely separated out, and the iron-removed steel slag is obtained. The content of elemental iron in the iron-removed steel slag is less than 0.5%, and the content of ferrous iron and ferric iron is less than 3.0%.

Description

Technical Field

[0001] The invention relates to the technical field of steelmaking waste treatment, in particular to a method for obtaining low-iron white steel slag. Background Art

[0002] As the core link of steel production, converter steelmaking not only provides the society with a steady supply of steel resources, but also produces a large number of by-products, among which steel slag is an important link that cannot be ignored. According to statistics, for every ton of steel produced, about 8%-10% of steel slag will be produced. If these steel slags cannot be effectively treated and utilized, they will not only occupy a large amount of land resources, but may also cause environmental pollution, such as soil pollution and water pollution. Therefore, exploring efficient and environmentally friendly ways to utilize steel slag powder (fine-grained steel slag obtained after slagging, crushing, screening, magnetic separation and other processes) has become a key issue that needs to be urgently solved for the sustainable development of the steel industry.

[0003] As an important product of steel slag processing, steel slag powder has a complex composition, mainly including silicate minerals, iron oxides, free calcium oxide, free magnesium oxide and a small amount of metallic iron. These components give steel slag powder unique physical and chemical properties, such as high hardness, high alkalinity, good water hardness and certain magnetism. However, it is these characteristics that, to a certain extent, limit the application of steel slag powder in the field of traditional building materials.

[0004] For example, in the cement industry, although the silicate mineral composition in steel slag powder is similar to that of cement clinker and has certain gelling properties, cement production has strict requirements on the iron content in the raw materials. Excessive iron will affect the color, strength and durability of cement. Therefore, although steel slag powder has certain substitution potential in cement production, its high iron content has become a major obstacle.

[0005] In the concrete field, when steel slag powder is used as a concrete admixture, its high specific gravity and iron content also bring challenges. The high specific gravity will increase the density of concrete and affect the construction performance; while the iron content may cause uneven color of concrete, affecting the appearance. In addition, the free calcium oxide and free magnesium oxide in the steel slag powder may expand in volume during the hardening process of concrete, affecting the stability and durability of concrete.

[0006] In the field of construction and decoration, due to the presence of iron in steel slag powder, its color change is difficult to predict and control, which is undoubtedly a huge challenge for building and decoration materials that pursue color consistency and aesthetics. Therefore, the application of steel slag powder in this field is also greatly limited.

[0007] In view of this, how to remove the iron element in steel slag to obtain an iron-free white steel slag is a technical problem that technical personnel in this field need to solve urgently. Summary of the invention

[0008] The object of the present invention is to provide a method for obtaining low-iron white steel slag, which can successively remove elemental iron, divalent iron and trivalent iron from the steel slag, so that all the iron elements in the steel slag can be separated out.

[0009] The present invention provides a method for obtaining low-iron white steel slag, comprising the following steps:

[0010] S1. Crushing, screening and magnetic separation of steel slag, grinding the residue from magnetic separation again until all materials pass through the screen to obtain steel slag powder;

[0011] S2, the steel slag powder is subjected to a first acid hydrolysis, and the obtained reaction product is subjected to solid-liquid separation to obtain a first liquid material and a first solid material;

[0012] S3. The first solid material is subjected to a second acid hydrolysis, and the obtained reaction product is subjected to solid-liquid separation to obtain a second liquid material and a second solid material. The second liquid material is subjected to cooling crystallization and solid-liquid separation to obtain CaCl2 crystals. The mixture of the second solid material and the CaCl2 crystals is the steel slag after iron removal.

[0013] The method for obtaining low-iron white steel slag of the present invention comprises the following steps: firstly, removing elemental iron from the steel slag by crushing, screening and magnetic separation; then, removing Fe 2+ The ferrous iron salt solution is converted into a divalent iron salt solution, which can be separated from the steel slag powder by cooling crystallization after solid-liquid separation; finally, the Fe 3+ The ferric iron salt solution can be converted into a ferric iron salt solution, and the ferric iron salt solution can be separated from the first solid material by solid-liquid separation, cooling crystallization, etc.

[0014] Therefore, the method of the present invention can successively remove elemental iron, divalent iron and trivalent iron from the steel slag, so that all the iron elements in the steel slag are separated out to obtain the iron-removed steel slag.

[0015] The steel slag of the present invention is a byproduct formed during converter steelmaking under high temperature conditions, wherein Fe and Ca exist in the form of oxides.

[0016] Among them, the grinding equipment for steel slag powder includes ball mill, vertical mill, ring roller mill, high pressure roller mill, Raymond mill, etc.

[0017] As a preferred embodiment of the present technical solution, in step S1, the mesh size of the sieve is 180-230 meshes, and preferably 200 meshes. After the steel slag is fully ground, magnetic separation is performed, which helps to fully remove the elemental iron in the steel slag through magnetic separation.

[0018] As a preferred embodiment of the present technical solution, in step S2, during the first acid hydrolysis, sulfuric acid is added to the steel slag powder, and the reaction temperature is controlled to be 70-90°C, and the reaction time is 3-5h, wherein the concentration of the sulfuric acid is 20%-50%, and the amount added is 20%-40% of the mass of the steel slag powder.

[0019] The following chemical reaction occurs here, and the reaction equations are shown in (1) and (2):

[0020] (1) FeO + H2SO4 = FeSO4 + H2O

[0021] (2) CaO + H2SO4 = CaSO4 + H2O

[0022] As a preferred embodiment of the present technical solution, in step S2, the first liquid material is cooled, crystallized, and solid-liquid separated to obtain FeSO4 crystals.

[0023] Specifically, when the first liquid material is cooled and crystallized, the first liquid material is cooled to 50-60° C. and maintained for 1-3 hours, so that the FeSO 4 crystals can be completely crystallized.

[0024] As a preferred embodiment of the present technical solution, in step S3, during the second acid hydrolysis, hydrochloric acid is added to the first solid material in a closed environment, and the reaction temperature is controlled to be 50-60°C, the reaction time is 3-5h, and the hydrochloric acid volatilized during the reaction drips into the reaction system, wherein the concentration of the hydrochloric acid is 20%-40%, and the amount added is 40%-60% of the mass of the first solid material.

[0025] The following chemical reaction occurs here, and the reaction equations are shown in (3) and (4):

[0026] (3)Fe2O3+6HCl=2FeCl3+3H2O

[0027] (4)CaO+2HCl=CaCl2+H2O

[0028] As a preferred embodiment of the present technical solution, when the second liquid material is subjected to cooling crystallization, the temperature of the second liquid material is lowered to 10-15° C. and maintained for 1-3 hours.

[0029] Specifically, the second liquid material is subjected to cooling crystallization and solid-liquid separation to obtain CaCl2 crystals and FeCl3 solution, wherein the obtained FeCl3 solution is subjected to heating evaporation crystallization concentration and solid-liquid separation to obtain FeCl3 crystals.

[0030] As a preferred embodiment of the present invention, the order of the first acid hydrolysis and the second acid hydrolysis can also be reversed, that is, hydrochloric acid is first added to the steel slag powder to remove Fe 3+The first solid material obtained by the first acid hydrolysis is converted into a trivalent iron salt, and sulfuric acid is added to the first solid material to convert the Fe 2+ Converted to ferrous salt.

[0031] As a preferred technical solution, the present invention grinds the steel slag powder to 200 meshes using a grinding device, adds sulfuric acid to acid-decompose the steel slag powder, and makes Fe 2+ Converted to FeSO4, with a small amount of Ca 2+ It is also converted into CaSO4. The acid hydrolysis process is an exothermic reaction. Good ventilation and cooling are required to control the solution temperature at 70-90°C. During the hydrolysis process, CaSO4 is slightly soluble in water and exists in the solid. FeSO4 is soluble in water and exists in the form of solution. After the acid hydrolysis is completed, FeSO4 is separated by solid-liquid separation. Then, the solution is cooled. When it is cooled to 60°C, FeSO4 begins to crystallize. Add hydrochloric acid to the remaining solid material, heat and stir to concentrate it. The Fe in the steel slag powder 3+ Converted to FeCl3, while a small amount of Ca 2+ Converted into CaCl2. Both FeCl3 and CaCl2 are easily soluble in water, so after solid-liquid separation, FeCl3 and CaCl2 are separated, and the mixed solution of the two is cooled to a temperature of 10-15°C, CaCl2 crystallizes to form crystals, and FeCl3 continues to exist in the solution, solid-liquid separation, and CaCl2 crystals are returned to the steel slag powder. The obtained steel slag powder is iron-free white steel slag powder. The separated liquid is heated, evaporated, concentrated and crystallized to obtain FeCl3 crystals.

[0032] The present invention utilizes a two-step acidolysis method to fully convert the divalent iron and trivalent iron in the steel slag into corresponding iron salt solutions, and can further effectively separate the obtained divalent iron crystals and trivalent iron crystals by cooling crystallization, thereby eliminating the iron-containing materials in the steel slag and making the color of the steel slag white.

[0033] The method for obtaining low-iron white steel slag of the present invention has at least the following beneficial effects:

[0034] The method for obtaining low-iron white steel slag of the present invention comprises the following steps: firstly, removing elemental iron from the steel slag by crushing, screening and magnetic separation; then, removing Fe 2+ The ferrous iron salt solution is converted into a divalent iron salt solution, which can be separated from the steel slag powder by cooling crystallization after solid-liquid separation; finally, the Fe 3+The ferric iron salt solution is converted into a ferric iron salt solution, and the ferric iron salt solution can be separated from the first solid material by solid-liquid separation, cooling crystallization, etc. Therefore, the method of the present invention can successively remove the elemental iron, divalent iron and ferric iron from the steel slag, so that all the iron elements in the steel slag are separated to obtain the steel slag after iron removal. Studies have shown that the elemental iron content in the steel slag after iron removal of the present invention is less than 0.5%, and the divalent iron and ferric iron are both less than 3.0%. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 The present invention is a schematic flow chart of the method for obtaining low-iron white steel slag. DETAILED DESCRIPTION

[0037] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0038] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form also includes the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this description, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0039] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] Example 1

[0041] The chemical indicators of the steel slag in this embodiment are shown in Table 1:

[0042] Table 1 Chemical indexes of steel slag powder, %

[0043] MFe FeO <![CDATA[Fe2O3]]> CaO <![CDATA[SiO2]]> MgO 1.25 10.27 11.64 39.71 11.08 9.43

[0044] S1. Grind the steel slag with a roller mill, and after grinding, screen it with a 200-mesh screen to form two kinds of materials, one on the screen and the other under the screen. The materials on the screen are magnetically separated with a 1000-1200 gauss magnetic separator to select iron-containing materials and magnetic separation residues, and the magnetic separation residues formed by magnetic separation are returned to the roller mill for grinding again, and the grinding, screening, and magnetic separation processes are repeated to finally obtain iron-containing materials and steel slag powder under the 200-mesh screen;

[0045] S2, add 35% sulfuric acid to the steel slag powder under the 200 mesh sieve for the first acidolysis, the sulfuric acid addition amount is 30% of the steel slag powder, after adding sulfuric acid, acidolysis for 4 hours and 40 minutes, during the acidolysis, the temperature is controlled at 75-85 ℃ by ventilation cooling, during the acidolysis, FeO is converted into FeSO4, a small amount of CaO is converted into CaSO4, after the acidolysis is completed, solid-liquid separation is performed to obtain a first liquid material and a first solid material, the first solid material is steel slag powder and CaSO4, the first liquid material is FeSO4 solution, the separated FeSO4 solution is cooled naturally, and when the temperature is reduced to 60 ℃, FeSO4 begins to crystallize to form crystals, and the temperature of FeSO4 crystallization is controlled at 50-60 ℃ for 2 hours, at which time the crystals are fully formed, solid-liquid separation is performed to obtain FeSO4 crystals and water;

[0046] S3, add 30% hydrochloric acid to the first solid material for a second acid hydrolysis, the mass ratio of the amount of hydrochloric acid added to the first solid material is about 1:1, after adding hydrochloric acid, stir and react at 60°C for 3-5h, Fe in the steel slag powder 3+ Converted to FeCl3, a small amount of Ca 2+ Converted into CaCl2, the formed FeCl3 and CaCl2 are both soluble in water. After the dissolution is completed, the solid-liquid separation is performed to obtain a second liquid material and a second solid material. The second solid material is steel slag powder, and the second liquid material is a mixed solution of FeCl3 and CaCl2. The second liquid material is cooled to 10-15°C, and CaCl2 crystallizes to form crystals. FeCl3 continues to exist in the solution and is maintained for 2 hours. When the crystals are completely formed, the solid-liquid separation is performed, and the CaCl2 crystals are separated in the form of a solid. The remaining material is a FeCl3 solution. The separated FeCl3 solution is heated, evaporated, concentrated and crystallized to obtain FeCl3 crystals. The formed CaCl2 crystals are returned to the steel slag powder and mixed evenly to obtain the steel slag after iron removal.

[0047] The chemical indicators of the steel slag after iron removal obtained in this embodiment are shown in Table 2:

[0048] Table 2 Chemical indexes of steel slag powder, %

[0049] MFe FeO <![CDATA[Fe2O3]]> 0.3 2.89 2.85

[0050] Example 2

[0051] The chemical indicators of the steel slag in this embodiment are shown in Table 3:

[0052] Table 3 Chemical indexes of steel slag powder, %

[0053] MFe FeO <![CDATA[Fe2O3]]> CaO <![CDATA[SiO2]]> MgO 1.25 10.27 11.64 39.71 11.08 9.43

[0054] S1. Grinding the steel slag with a roller mill, and after grinding, sieving with a 180-mesh screen to form two kinds of materials, namely, materials on the screen and materials under the screen. The materials on the screen are magnetically separated with a 1000-1200 gauss magnetic separator to select iron-containing materials and magnetic separation residues, and the magnetic separation residues formed by magnetic separation are returned to the roller mill for grinding again, and the grinding, screening, and magnetic separation processes are repeated to finally obtain iron-containing materials and steel slag powder under the 180-mesh screen;

[0055] S2, add 35% sulfuric acid to the steel slag powder under the 180 mesh sieve for the first acidolysis, the sulfuric acid addition amount is 40% of the steel slag powder, after adding sulfuric acid, acidolysis for 4 hours, during the acidolysis, the temperature is controlled at 75-85 ℃ by ventilation cooling, during the acidolysis, FeO is converted into FeSO4, a small amount of CaO is converted into CaSO4, after the acidolysis is completed, solid-liquid separation is performed to obtain a first liquid material and a first solid material, the first solid material is steel slag powder and CaSO4, the first liquid material is FeSO4 solution, the separated FeSO4 solution is cooled naturally, and when the temperature is reduced to 60 ℃, FeSO4 begins to crystallize to form crystals, the temperature of FeSO4 crystallization is controlled at 50-60 ℃, maintained for 2 hours, at which time the crystals are fully formed, solid-liquid separation is performed to obtain FeSO4 crystals and water;

[0056] S3, add 40% hydrochloric acid to the first solid material for a second acid hydrolysis, the amount of hydrochloric acid added is 40% of the mass of the first solid material, after adding hydrochloric acid, stir and react at 50°C for 3-5h, Fe in the steel slag powder 3+ Converted to FeCl3, a small amount of Ca 2+ Converted into CaCl2, the formed FeCl3 and CaCl2 are both soluble in water. After the dissolution is completed, the solid-liquid separation is performed to obtain a second liquid material and a second solid material. The second solid material is steel slag powder, and the second liquid material is a mixed solution of FeCl3 and CaCl2. The second liquid material is cooled to 10-15°C, and CaCl2 crystallizes to form crystals. FeCl3 continues to exist in the solution and is maintained for 2 hours. When the crystals are completely formed, the solid-liquid separation is performed, and the CaCl2 crystals are separated in the form of a solid. The remaining material is a FeCl3 solution. The separated FeCl3 solution is heated, evaporated, concentrated and crystallized to obtain FeCl3 crystals. The formed CaCl2 crystals are returned to the steel slag powder and mixed evenly to obtain the steel slag after iron removal.

[0057] The chemical indicators of the steel slag after iron removal obtained in this embodiment are shown in Table 4:

[0058] Table 4 Chemical indexes of steel slag powder, %

[0059] MFe FeO <![CDATA[Fe2O3]]> 0.5 2.74 2.81

[0060] Example 3

[0061] The chemical indicators of the steel slag in this embodiment are shown in Table 5:

[0062] Table 5 Chemical indexes of steel slag powder, %

[0063] MFe FeO <![CDATA[Fe2O3]]> CaO <![CDATA[SiO2]]> MgO 1.25 10.27 11.64 39.71 11.08 9.43

[0064] S1. Grind the steel slag with a roller mill, and after grinding, screen it with a 230-mesh screen to form two kinds of materials, one on the screen and one under the screen. The materials on the screen are magnetically separated with a 1000-1200 gauss magnetic separator to select iron-containing materials and magnetic separation residues, and the magnetic separation residues formed by magnetic separation are returned to the roller mill for grinding again, and the grinding, screening, and magnetic separation processes are repeated to finally obtain iron-containing materials and steel slag powder under the 230-mesh screen;

[0065] S2, add 30% sulfuric acid to the steel slag powder under the 230 mesh sieve for the first acidolysis, the sulfuric acid addition amount is 35% of the steel slag powder, after adding sulfuric acid, acidolysis for 5 hours, during the acidolysis, the temperature is controlled at 75-85 ℃ by ventilation cooling, during the acidolysis, FeO is converted into FeSO4, a small amount of CaO is converted into CaSO4, after the acidolysis is completed, solid-liquid separation is performed to obtain a first liquid material and a first solid material, the first solid material is steel slag powder and CaSO4, the first liquid material is FeSO4 solution, the separated FeSO4 solution is cooled naturally, and when the temperature is reduced to 60 ℃, FeSO4 begins to crystallize to form crystals, the temperature of FeSO4 crystallization is controlled at 50-60 ℃, maintained for 2 hours, at which time the crystals are fully formed, solid-liquid separation is performed to obtain FeSO4 crystals and water;

[0066] S3, add 20% hydrochloric acid to the first solid material for a second acid hydrolysis, the amount of hydrochloric acid added is 60% of the mass of the first solid material, after adding hydrochloric acid, stir and react at 50°C for 3-5h, Fe in the steel slag powder 3+ Converted to FeCl3, a small amount of Ca 2+Converted into CaCl2, the formed FeCl3 and CaCl2 are both soluble in water. After the dissolution is completed, the solid-liquid separation is performed to obtain a second liquid material and a second solid material. The second solid material is steel slag powder, and the second liquid material is a mixed solution of FeCl3 and CaCl2. The second liquid material is cooled to 10-15°C, and CaCl2 crystallizes to form crystals. FeCl3 continues to exist in the solution and is maintained for 2 hours. When the crystals are completely formed, the solid-liquid separation is performed, and the CaCl2 crystals are separated in the form of a solid. The remaining material is a FeCl3 solution. The separated FeCl3 solution is heated, evaporated, concentrated and crystallized to obtain FeCl3 crystals. The formed CaCl2 crystals are returned to the steel slag powder and mixed evenly to obtain the steel slag after iron removal.

[0067] The chemical indicators of the steel slag after iron removal obtained in this embodiment are shown in Table 6:

[0068] Table 6 Chemical indexes of steel slag powder, %

[0069] MFe FeO <![CDATA[Fe2O3]]> 0.3 2.46 2.57

[0070] Example 4

[0071] The chemical indicators of the steel slag in this embodiment are shown in Table 7:

[0072] Table 7 Chemical indexes of steel slag powder, %

[0073] MFe FeO <![CDATA[Fe2O3]]> CaO <![CDATA[SiO2]]> MgO 1.25 10.27 11.64 39.71 11.08 9.43

[0074] S1. Grind the steel slag with a roller mill, and after grinding, screen it with a 200-mesh screen to form two kinds of materials, one on the screen and the other under the screen. The materials on the screen are magnetically separated with a 1000-1200 gauss magnetic separator to select iron-containing materials and magnetic separation residues, and the magnetic separation residues formed by magnetic separation are returned to the roller mill for grinding again, and the grinding, screening, and magnetic separation processes are repeated to finally obtain iron-containing materials and steel slag powder under the 200-mesh screen;

[0075] S2. Add 30% hydrochloric acid to the steel slag powder under a 200-mesh sieve for the first acid hydrolysis. The mass ratio of hydrochloric acid to steel slag powder is about 1:1. After adding hydrochloric acid, stir and react at 50°C for 3-5 hours. The Fe 3+ Converted to FeCl3, a small amount of Ca 2+Converted into CaCl2, the formed FeCl3 and CaCl2 are both soluble in water, after the dissolution is completed, the solid-liquid separation is performed to obtain a first liquid material and a first solid material, the first solid material is steel slag powder, the first liquid material is a mixed solution of FeCl3 and CaCl2, the first liquid material is cooled to 10-15°C, CaCl2 crystallizes to form crystals, FeCl3 continues to exist in the solution, maintained for 2 hours, the crystals are completely formed, the solid-liquid separation is performed, the CaCl2 crystals are separated in the form of a solid, and the remaining material is a FeCl3 solution, the separated FeCl3 solution is heated, evaporated, concentrated and crystallized to obtain FeCl3 crystals, and the formed CaCl2 crystals are returned to the steel slag powder for uniform mixing;

[0076] S3, add 35% sulfuric acid to the first solid material for a second acidolysis, the sulfuric acid addition amount is 30% of the first solid material, after adding sulfuric acid, acidolysis for 4 hours and 40 minutes, during the acidolysis process, the temperature is controlled at 75-85 ℃ by ventilation cooling, during the acidolysis process, FeO is converted into FeSO4, a small amount of CaO is converted into CaSO4, after the acidolysis is completed, solid-liquid separation is performed to obtain a second liquid material and a second solid material, the second solid material is slag powder and CaSO4, the second liquid material is FeSO4 solution, the separated FeSO4 solution is cooled naturally, and when the temperature is reduced to 60 ℃, FeSO4 begins to crystallize to form crystals, and the temperature of FeSO4 crystallization is controlled at 50-60 ℃ for 2 hours, at which time the crystals are completely formed, solid-liquid separation is performed to obtain FeSO4 crystals and water;

[0077] The CaCl2 crystals and steel slag powder obtained in step S2 are mixed to obtain the steel slag after iron removal.

[0078] The chemical indicators of the steel slag after iron removal obtained in this embodiment are shown in Table 8:

[0079] Table 8 Chemical indexes of steel slag powder, %

[0080] MFe FeO <![CDATA[Fe2O3]]> 0.4 2.72 2.60

[0081] Comparative Example 1

[0082] In this comparative example, the first and second acid hydrolysis of the steel slag powder were not performed, and the rest was basically the same as in Example 1.

[0083] The chemical indicators of the steel slag after iron removal obtained in this comparative example are shown in Table 9:

[0084] Table 9 Chemical indexes of steel slag powder, %

[0085] MFe FeO <![CDATA[Fe2O3]]> 0.4 10.25 11.60

[0086] Comparative Example 2

[0087] This reference example is substantially the same as Example 1, except that the time for sulfuric acid hydrolysis in this reference example is controlled to be 2 h.

[0088] The chemical indicators of the steel slag after iron removal obtained in this comparative example are shown in Table 10:

[0089] Table 10 Chemical indexes of steel slag powder, %

[0090] MFe FeO <![CDATA[Fe2O3]]> 0.4 7.65 2.68

[0091] Comparative Example 3

[0092] This reference example is substantially the same as Example 1, except that the hydrochloric acid hydrolysis time in this reference example is controlled to be 1 h.

[0093] The chemical indicators of the steel slag after iron removal obtained in this comparative example are shown in Table 11:

[0094] Table 11 Chemical indexes of steel slag powder, %

[0095] MFe FeO <![CDATA[Fe2O3]]> 0.4 2.81 6.87

[0096] In summary, the method of the present invention can successively remove elemental iron, divalent iron and ferric iron from steel slag, and the content of elemental iron in the steel slag after iron removal is less than 0.5%, and the content of divalent iron and ferric iron are both less than 3.0%. The color of the obtained steel slag is white, which can fully meet the requirements of the cement field, concrete field and architectural decoration field for low iron content of steel slag powder, and the obtained iron-containing materials, FeSO4 crystals and FeCl3 crystals can also be further recycled and reused.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for obtaining low-iron white steel slag, characterized in that: The following steps are involved: S1. Crushing, screening and magnetic separation of steel slag, grinding the residue from magnetic separation again until all materials pass through the screen to obtain steel slag powder; S2, the steel slag powder is subjected to a first acid hydrolysis, and the obtained reaction product is subjected to solid-liquid separation to obtain a first liquid material and a first solid material; S3. The first solid material is subjected to a second acid hydrolysis, and the obtained reaction product is subjected to solid-liquid separation to obtain a second liquid material and a second solid material. The second liquid material is subjected to cooling crystallization and solid-liquid separation to obtain CaCl2 crystals. The mixture of the second solid material and the CaCl2 crystals is the steel slag after iron removal.

2. The method for obtaining low-iron white steel slag according to claim 1, characterized in that: In step S1, the mesh size of the sieve is 180-230 meshes.

3. The method for obtaining low-iron white steel slag according to claim 1, characterized in that: In step S2, during the first acid hydrolysis, sulfuric acid is added to the steel slag powder, and the reaction temperature is controlled to be 70-90° C. and the reaction time is 3-5 hours.

4. The method for obtaining low-iron white steel slag according to claim 3, characterized in that: The concentration of the sulfuric acid is 20%-50%, and the amount added is 20%-40% of the mass of the steel slag powder.

5. The method for obtaining low-iron white steel slag according to claim 1, characterized in that: In step S2, the first liquid material is cooled, crystallized, and solid-liquid separated to obtain FeSO4 crystals.

6. The method for obtaining low-iron white steel slag according to claim 5, characterized in that: When the first liquid material is subjected to cooling crystallization, the temperature of the first liquid material is lowered to 50-60° C. and maintained for 1-3 hours.

7. The method for obtaining low-iron white steel slag according to claim 1, characterized in that: In step S3, during the second acid hydrolysis, hydrochloric acid is added to the first solid material, and the reaction temperature is controlled to be 50-60° C. and the reaction time is 3-5 hours.

8. The method for obtaining low-iron white steel slag according to claim 7, characterized in that: The concentration of the hydrochloric acid is 20%-40%, and the added amount is 40%-60% of the mass of the first solid material.

9. The method for obtaining low-iron white steel slag according to claim 1, characterized in that: When the second liquid material is cooled and crystallized, the temperature of the second liquid material is lowered to 10-15° C. and maintained for 1-3 hours.

10. The method for obtaining low-iron white steel slag according to claim 1, characterized in that: In step S3, the second liquid material is cooled, crystallized, and solid-liquid separated, and the obtained FeCl3 solution is heated, evaporated, crystallized, and concentrated to obtain FeCl3 crystals.

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