Method for preparing iron and cementing material by electrolyzing molten steel slag

Abstract

The invention provides a method for preparing iron and a cementing material through electrolysis of molten steel slag, and belongs to the technical field of solid waste resource utilization. The method comprises the following steps: mixing molten steel slag and a siliceous modifier to obtain mixed molten slag; the mixed slag is subjected to electrolytic reduction, and modified slag with reconstructed components and metal iron are obtained; and mixing the modified slag with the reconstructed components with calcium oxide to obtain silicate slag, then cooling to room temperature, and recycling cooling heat for preheating the siliceous modifier and calcium oxide to obtain the silicate cementing material. According to the method, the iron element is directly recovered from the molten steel slag through an electrochemical reduction method, so that the reduction efficiency is high, the addition of other reagents can be reduced, and the carbon emission of iron and steel enterprises is reduced; the modified slag obtained after component reconstruction and calcium oxide are mixed and cooled to the room temperature, the silicate cementing material is directly prepared, recycled heat is used for preheating raw materials, carbon emission reduction in the ferrous metallurgy industry is achieved, and energy consumption of iron and steel enterprises is reduced.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization technology, and in particular to a method for preparing iron and cementitious materials by electrolysis of molten steel slag. Background Technology

[0002] Steel slag is a major industrial waste generated during the steelmaking process, consuming significant land resources and causing environmental pollution. Steel slag is produced at temperatures between 1500 and 1700°C, containing substantial amounts of heat energy. Its main components are CaO, Fe₂O₃, SiO₂, MgO, and Al₂O₃, with small amounts of MnO and TiO₂. Due to the steelmaking process, steel slag suffers from poor stability, fluctuating chemical composition, and poor cementitious activity, resulting in a comprehensive utilization rate of only about 30%. Currently, steel slag is mainly utilized for backfilling in engineering projects, in the building materials industry, and returned to the smelting process. However, with increasing quality requirements for silicate cement, steel slag can no longer be used as a blending material in silicate cement production, further limiting its utilization. Furthermore, the aforementioned utilization methods all involve cooling the steel slag to room temperature before use, failing to achieve the synergistic utilization of thermal and chemical energy.

[0003] By treating steel slag, not only can the iron element in the slag be recovered, but the cementitious properties of the slag can also be improved, allowing the treated slag to be used to produce silicate cement for the preparation of high-strength materials. For example, prior art 1 (IN202121003265A) describes melting steel slag, adding a reducing agent to reduce the iron oxide in the slag to obtain molten iron, then separating the iron from the reduced steel slag, and finally adding a modifier or a silica source free of impurities for modification to obtain a high-performance cementitious material that can be used to replace silicate cement. However, the above method requires the addition of a large amount of reducing agent and modifier, resulting in high steel slag treatment costs and poor market competitiveness. Existing technology 2 (RU2572438C1) processes waste steel slag by: screening the waste steel slag with a drum separator to separate oversized slag pieces; performing magnetic separation with a cylindrical magnetic separator; then crushing it in a jaw crusher; subsequently, performing magnetic separation on the crushed product using a cylindrical magnetic separator; finally, crushing and performing magnetic separation in a centrifugal impact crusher; and finally, grinding it into 150-200 μm particles in a roller crusher after multi-stage crushing and magnetic separation. 2 The process involves mixing granules of / kg with reducing agent metallic aluminum and heating them. After heating, the molten metallic iron is reduced and separated. Cryolite and aluminum fluoride are added to the remaining melt, and electrolysis yields a silicon-aluminum alloy. However, the above methods require the addition of a large amount of reducing agent to reduce the iron oxides in the steel slag; or they only treat the cold steel slag, failing to recover and utilize the heat energy of the steel slag. Furthermore, the overall process is complex and the production cost is high.

[0004] Therefore, providing a simple, low-cost process for preparing iron and cementitious materials using steel slag has become a pressing technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing iron and cementitious materials by electrolysis of molten steel slag. The iron recovery rate of the method provided by this invention is >96%, and the silicate cementitious materials can be used as clinker in the manufacture of ordinary silicate cement. At the same time, using molten steel slag as raw material can not only utilize the silicate components in the molten steel slag and the heat generated by cooling, but also eliminates the need for multi-stage crushing. The preparation process is simple and the production cost is low.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing iron and cementitious materials by electrolysis of molten steel slag, comprising the following steps: (1) Mix molten steel slag and silicon modifier to obtain mixed slag; (2) Electrolytically reduce the mixed slag obtained in step (1) to obtain modified slag with reconstructed composition and metallic iron; (3) After mixing the modified slag with the component reconstruction obtained in step (2) and calcium oxide, the mixture is cooled to room temperature to obtain silicate cementitious material; In step (1), the mass ratio of silicon modifier to molten steel slag is (0.0706~0.1392):1; In step (2), the reduction potential of electrolytic reduction is 0.4~10.0V, the current of electrolytic reduction is 5~15A, and the time of electrolytic reduction is 0.5~5h; The mass ratio of calcium oxide in step (3) to molten steel slag in step (1) is (0.1648~0.2833):1.

[0007] Preferably, the molten steel slag in step (1) is molten steel slag produced by converter steelmaking.

[0008] Preferably, the temperature of the molten steel slag in step (1) is 1450~1600℃.

[0009] Preferably, the silica modifier in step (1) includes any one or more of quartz sand, silica fume, and quartz waste.

[0010] Preferably, the silicon dioxide content in the silicon modifier is 90-100% by mass.

[0011] Preferably, the anode and cathode during electrolytic reduction in step (2) are independently high-temperature resistant conductive electrodes.

[0012] Preferably, the high-temperature resistant conductive electrode comprises any one or more of graphite electrodes, platinum electrodes, rhodium electrodes, iridium electrodes, and silicon carbide electrodes.

[0013] This invention provides a method for preparing iron and cementitious materials by electrolysis of molten steel slag, comprising the following steps: (1) mixing molten steel slag and a silica modifier to obtain a mixed slag; (2) electrolytically reducing the mixed slag obtained in step (1) to obtain a modified slag with reconstructed components and metallic iron; (3) mixing the modified slag with reconstructed components obtained in step (2) and calcium oxide and cooling it to room temperature to obtain a silicate cementitious material; the mass ratio of silica modifier to molten steel slag in step (1) is (0.0706~0.1392):1; the reduction potential of electrolysis in step (2) is 0.4~10.0V, the current of electrolysis is 5~15A, and the time of electrolysis is 0.5~5h; the mass ratio of calcium oxide to molten steel slag in step (1) in step (3) is (0.1648~0.2833):1. This invention directly recovers iron from molten steel slag using an electrochemical reduction method. This method not only boasts high reduction efficiency but also reduces the need for additional reagents, thereby decreasing carbon emissions from steel enterprises. By mixing the reconstructed modified slag with calcium oxide and cooling it to room temperature, silicate cementitious materials are directly produced. This process utilizes the silicate components in the molten steel slag and the heat generated during cooling, eliminating the need for multi-stage crushing. The simple preparation process facilitates carbon reduction in the steel metallurgical industry and lowers energy consumption for steel enterprises. Furthermore, the invention uses relatively small amounts of silicate modifier and calcium oxide in the preparation of iron and cementitious materials, significantly reducing production costs and facilitating large-scale industrial application. The results of the examples show that the iron recovery rate obtained by the method provided by the present invention is all >96%, basically recovering most of the iron in the molten steel slag; at the same time, the free calcium oxide content in the silicate cementitious materials is all less than ≤1.5% required by the national standard; the Fe2O3 content in the obtained silicate cementitious materials is all low, indicating that the iron reduction effect is good, and the composition of the silicate cementitious materials is mainly calcium oxide, silicon dioxide, aluminum oxide and magnesium oxide, etc., which has the potential to be used as clinker in the manufacture of ordinary silicate cement; the 3-day, 7-day and 28-day compressive strengths of the neat cement paste test blocks obtained in Examples 1 and 3 are similar to those of pure cement, while the 3-day and 7-day compressive strengths of the neat cement paste test blocks obtained in Example 2 are higher than those of pure cement, while the 28-day compressive strength is slightly lower than that of pure cement, indicating that the silicate cementitious materials obtained by the method provided by the present invention can all be used as clinker in the manufacture of ordinary silicate cement. Attached Figure Description

[0014] Figure 1 The XRD patterns of the silicate cementitious materials obtained in Examples 1-3 are shown below. Figure 2The graph shows a comparison of the compressive strength of the silicate cementitious materials obtained in Examples 1-3 and the pure cement provided in Comparative Example 1 after 3 days. Figure 3 The graph shows a comparison of the compressive strength of the silicate cementitious materials obtained in Examples 1-3 and the pure cement provided in Comparative Example 1 after 7 days. Figure 4 The graph shows a comparison of the compressive strength of the silicate cementitious materials obtained in Examples 1-3 and the pure cement provided in Comparative Example 1 after 28 days. Detailed Implementation

[0015] This invention provides a method for preparing iron and cementitious materials by electrolysis of molten steel slag, comprising the following steps: (1) Mix molten steel slag and silicon modifier to obtain mixed slag; (2) Electrolytically reduce the mixed slag obtained in step (1) to obtain modified slag with reconstructed composition and metallic iron; (3) After mixing the modified slag with the component reconstruction obtained in step (2) and calcium oxide, the mixture is cooled to room temperature to obtain silicate cementitious material; In step (1), the mass ratio of silicon modifier to molten steel slag is (0.0706~0.1392):1; In step (2), the reduction potential of electrolytic reduction is 0.4~10.0V, the current of electrolytic reduction is 5~15A, and the time of electrolytic reduction is 0.5~5h; The mass ratio of calcium oxide in step (3) to molten steel slag in step (1) is (0.1648~0.2833):1.

[0016] This invention mixes molten steel slag with a silicon modifier to obtain a mixed molten slag.

[0017] In this invention, the molten steel slag is preferably molten steel slag produced by converter steelmaking. This invention does not have a specific limitation on the specific source of the steel slag; any steel slag well-known to those skilled in the art can be used. This invention does not have a specific limitation on the heating and melting temperature; any temperature that allows the molten steel slag to reach the required level is acceptable.

[0018] In this invention, the temperature of the molten steel slag is preferably 1450~1600℃. As one embodiment of this invention, the temperature of the molten steel slag can be 1450℃, 1500℃, 1550℃, or 1600℃. The molten steel slag used in this invention remains in a molten state and has excellent fluidity.

[0019] In this invention, the silica modifier preferably includes any one or more of quartz sand, silica fume, and quartz waste; the silica content in the silica modifier is preferably 90-100% by mass. In this invention, the molten steel slag mainly contains dicalcium silicate, tricalcium silicate, and calcium ferrite, etc. Dicalcium silicate undergoes a crystal transformation during cooling, accompanied by a certain volume expansion, resulting in pulverization and instability of the steel slag. This invention, by adding a silica modifier, can change the chemical composition and mineral structure of the molten steel slag through chemical and mineral phase transformation, adjust the initial viscosity and fluidity of the steel slag, inhibit pulverization, and improve volume stability, thereby transforming it from an unstable state into a stable mixed molten slag.

[0020] In this invention, the mass ratio of the silica modifier to the molten steel slag is (0.0706~0.1392):1. As one embodiment of this invention, the mass ratio of the silica modifier to the molten steel slag can be 0.0706:1, 0.08:1, 0.0842:1, 0.09:1, 0.1:1, 0.11:1, 0.12:1, 0.13:1, or 0.1392:1. This invention, by controlling the dosage relationship between the silica modifier and the molten steel slag, can better improve the stability of the molten steel slag.

[0021] In this invention, the mixing of the molten steel slag and the silica modifier is preferably carried out in a high-temperature reactor; the high-temperature reactor is preferably a container lined with refractory material. This invention does not impose any special limitations on the size and structure of the high-temperature reactor, which can be determined based on the technical knowledge of those skilled in the art.

[0022] After obtaining the mixed slag, the present invention performs electrolytic reduction on the mixed slag to obtain modified slag with reconstructed composition and metallic iron.

[0023] In this invention, the anode and cathode during electrolytic reduction are preferably independently high-temperature resistant conductive electrodes; the high-temperature resistant conductive electrodes preferably include any one or more of graphite electrodes, platinum electrodes, rhodium electrodes, iridium electrodes, and silicon carbide electrodes. In this invention, using high-temperature resistant conductive electrodes enables better electrolysis while avoiding damage to the electrodes from high temperatures.

[0024] In this invention, the reduction potential of the electrolytic reduction is 0.4~10.0V; the current of the electrolytic reduction is 5~15A; the electrolytic reduction time is 0.5~5h; and the mixed slag is preferably kept in a molten state during the electrolytic reduction. In one embodiment of the present invention, the reduction potential of the electrolytic reduction is 0.4V, 0.5V, 0.8V, 1.0V, 1.5V, 2.0V, 2.5V, 3.0V, 3.5V, 4.0V, 4.5V, 5.0V, 5.5V, 6.0V, 6.5V, 7.0V, 7.5V, 8.0V, 8.5V, 9.0V, 9.5V, or 10.0V; the current of the electrolytic reduction can be 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A, 14A, or 15A; and the electrolytic reduction time can be 0.5h, 1h, 2h, 3h, 4h, or 5h. This invention reduces iron ions in mixed slag to metallic iron by controlling the reduction potential of electrolytic reduction; by keeping the mixed slag in a molten state, it facilitates the full progress of electrolytic reduction, thereby achieving an iron recovery rate of over 96%.

[0025] In this invention, the metallic iron settles at the bottom, which facilitates its subsequent recovery. In this invention, the metallic iron is used in steel production.

[0026] After obtaining the modified slag with reconstructed components, the present invention mixes the modified slag with calcium oxide and cools it to room temperature to obtain a silicate cementitious material.

[0027] In this invention, the mass ratio of calcium oxide to molten steel slag is (0.1648~0.2833):1. As one embodiment of this invention, the mass ratio of calcium oxide to molten steel slag can be 0.1648:1, 0.17:1, 0.18:1, 0.19:1, 0.2:1, 0.21:1, 0.22:1, 0.23:1, 0.24:1, 0.25:1, 0.26:1, 0.27:1, 0.28:1, or 0.2833:1. This invention first uses a silica modifier to suppress the negative effects of free calcium oxide, such as "reduced gelling activity and increased volume expansion." After electrolysis, calcium oxide is added to increase alkalinity, thereby changing the mineral composition and physical properties of the modified slag, thus giving the gel material high hydraulic gelling properties.

[0028] The present invention does not have any special limitations on the specific operation of mixing the modified slag and calcium oxide of the component reconstruction. Conventional mixing methods can be used to ensure that the mixture is uniform.

[0029] This invention does not impose any particular limitation on the specific cooling method; any cooling method well-known to those skilled in the art can be used. As one embodiment of this invention, the cooling method can be any one of room temperature cooling, air cooling, and water quenching; the cooling can be carried out in a high-temperature reactor; the high-temperature reactor can be a container constructed of refractory material. This invention does not impose any particular limitation on the size and structure of the high-temperature reactor; it can be determined based on the technical knowledge of those skilled in the art. This invention, by cooling in a high-temperature reactor, facilitates the control of the cooling rate and heat recovery.

[0030] The present invention preferably further includes recovering the heat from the cooling process and using it for preheating the silicon modifier and calcium oxide. The present invention does not impose any special limitations on the specific operation of the heat recovery; conventional heat recovery methods can be used.

[0031] In this invention, the silicate cementitious material is preferably used as clinker in the manufacture of ordinary silicate cement. This invention does not impose any particular limitation on the specific manufacturing method; any manufacturing method well-known to those skilled in the art can be used.

[0032] This invention directly recovers iron from molten steel slag using an electrochemical reduction method. This method not only boasts high reduction efficiency but also reduces the need for additional reagents, thereby decreasing carbon emissions from steel enterprises. By mixing the reconstructed modified slag with calcium oxide and cooling it to room temperature, silicate cementitious materials are directly produced. This method utilizes the silicate components and heat in the molten steel slag, which is beneficial for carbon emission reduction in the steel metallurgical industry and for reducing energy consumption in steel enterprises. Furthermore, this invention uses relatively small amounts of silicate modifier and calcium oxide in the preparation of iron and cementitious materials, significantly reducing production costs and facilitating large-scale industrial application.

[0033] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0034] Example 1 A method for preparing iron and cementitious materials by electrolysis of molten steel slag comprises the following steps: (1) Molten steel slag and silica modifier are mixed in a high-temperature reactor to obtain mixed slag; the molten steel slag is molten steel slag produced by converter steelmaking, and the temperature of the molten steel slag is 1450℃; the silica modifier is quartz sand; the mass ratio of the silica modifier to the molten steel slag is 0.0842:1; (2) The mixed slag obtained in step (1) is electrolytically reduced to obtain modified slag with reconstructed components and metallic iron, with the metallic iron settling at the bottom; the anode and cathode during the electrolytic reduction are both graphite electrodes, the reduction potential of the electrolytic reduction is 7.6V, the current of the electrolytic reduction is 9A, and the electrolytic reduction time is 2h. (3) The modified slag and calcium oxide obtained in step (2) are mixed in a high-temperature reactor and then cooled to room temperature to obtain silicate cementitious material; the mass ratio of calcium oxide to molten steel slag is 0.1648:1.

[0035] Example 2 A method for preparing iron and cementitious materials by electrolysis of molten steel slag comprises the following steps: (1) Molten steel slag and silica modifier are mixed in a high-temperature reactor to obtain mixed slag; the molten steel slag is molten steel slag produced by converter steelmaking, and the temperature of the molten steel slag is 1500℃; the silica modifier is quartz sand; the mass ratio of the silica modifier to the molten steel slag is 0.0842:1; (2) The mixed slag obtained in step (1) is electrolytically reduced to obtain modified slag with reconstructed components and metallic iron, with the metallic iron settling at the bottom; the anode and cathode during the electrolytic reduction are both graphite electrodes, the reduction potential of the electrolytic reduction is 6.8V, the current of the electrolytic reduction is 9A, and the electrolytic reduction time is 2h. (3) The modified slag and calcium oxide obtained in step (2) are mixed in a high-temperature reactor and then cooled to room temperature to obtain silicate cementitious material; the mass ratio of calcium oxide to molten steel slag is 0.1648:1.

[0036] Example 3 A method for preparing iron and cementitious materials by electrolysis of molten steel slag comprises the following steps: (1) Molten steel slag and silica modifier are mixed in a high-temperature reactor to obtain mixed slag; the molten steel slag is molten steel slag produced by converter steelmaking, and the temperature of the molten steel slag is 1550℃; the silica modifier is quartz sand; the mass ratio of the silica modifier to the molten steel slag is 0.0842:1; (2) The mixed slag obtained in step (1) is electrolytically reduced to obtain modified slag with reconstructed components and metallic iron, with the metallic iron settling at the bottom; the anode and cathode during the electrolytic reduction are both graphite electrodes, the reduction potential of the electrolytic reduction is 8.2V, the current of the electrolytic reduction is 9A, and the electrolytic reduction time is 2h. (3) The modified slag and calcium oxide obtained in step (2) are mixed in a high-temperature reactor and then cooled to room temperature to obtain silicate cementitious material; the mass ratio of calcium oxide to molten steel slag is 0.1648:1.

[0037] Comparative Example 1 Pure cement, specifically PI42.5 cement from Shandong Shanshui Cement Group Co., Ltd.

[0038] Comparative Example 2 A method for preparing iron and cementitious materials by electrolysis of molten steel slag comprises the following steps: (1) Molten steel slag and silica modifier are mixed in a high-temperature reactor to obtain mixed slag; the molten steel slag is molten steel slag produced by converter steelmaking, and the temperature of the molten steel slag is 1500℃; the silica modifier is quartz sand; the mass ratio of the silica modifier to the molten steel slag is 0.0842:1; (2) The mixed slag obtained in step (1) is electrolytically reduced to obtain cementitious material and metallic iron, with the metallic iron settling at the bottom; the anode and cathode during the electrolytic reduction are both graphite electrodes, the reduction potential of the electrolytic reduction is 6.8V, the current of the electrolytic reduction is 9A, and the electrolytic reduction time is 2h.

[0039] Comparative Example 3 A method for preparing iron and cementitious materials by electrolysis of molten steel slag comprises the following steps: (1) The molten steel slag is electrolytically reduced to obtain electrolyte and metallic iron, and the metallic iron settles at the bottom; the molten steel slag is the molten steel slag produced by converter steelmaking, and the temperature of the molten steel slag is 1550℃; the anode and cathode of the electrolytic reduction are both graphite electrodes, the reduction potential of the electrolytic reduction is 8.2V, the current of the electrolytic reduction is 9A, and the electrolytic reduction time is 2h; (2) The electrolyte obtained in step (1) and calcium oxide are mixed in a high-temperature reactor and then cooled to room temperature to obtain a cementitious material; the mass ratio of calcium oxide to molten steel slag is 0.1648:1.

[0040] Comparative Example 4 A method for preparing iron and cementitious materials by electrolysis of molten steel slag comprises the following steps: (1) The molten steel slag is electrolytically reduced to obtain electrolyte and metallic iron, and the metallic iron settles at the bottom; the molten steel slag is the molten steel slag produced by converter steelmaking, and the temperature of the molten steel slag is 1550℃; the anode and cathode of the electrolytic reduction are both graphite electrodes, the reduction potential of the electrolytic reduction is 8.2V, the current of the electrolytic reduction is 9A, and the electrolytic reduction time is 2h; (2) The electrolyte, silica modifier and calcium oxide obtained in step (1) are mixed in a high-temperature reactor and then cooled to room temperature to obtain a cementitious material; the silica modifier is quartz sand; the mass ratio of the silica modifier to molten steel slag is 0.0842:1; the mass ratio of calcium oxide to molten steel slag is 0.1648:1.

[0041] The iron recovery rate R obtained by the methods provided in Examples 1-3 Fe The calculation is performed using the formula shown in Equation I: R Fe =(C0-C1) / C0Form I In formula I, R Fe C0 represents the iron recovery rate, C1 represents the total iron content in the molten steel slag, and C2 represents the total iron content in the modified slag with reconstructed components.

[0042] The free calcium oxide content in silicate cementitious materials was determined according to the national standard method GB / T176-2017, Cement Chemical Analysis Method.

[0043] Iron recovery rate and free calcium oxide content are shown in Table 1.

[0044] Table 1. Results of iron recovery rate and free calcium oxide content in the molten steel slag of Examples 1-3

[0045] As can be seen from Table 1, the iron recovery rate obtained by the methods provided in Examples 1 to 3 of this invention is all >96%, which basically recovers most of the iron in the molten steel slag; at the same time, the free calcium oxide content in the silicate cementitious materials is all less than ≤1.5% as required by the national standard, which shows that the silicate cementitious materials obtained by the methods provided in this application meet the national standards.

[0046] XRF tests were performed on the silicate cementitious materials obtained in Examples 1-3, and the results are shown in Table 2. Table 2 XRF of silicate cementitious materials obtained in Examples 1-3

[0047] As can be seen from Table 2, the silicate cementitious materials obtained by the methods provided in Examples 1-3 of this invention have low Fe2O3 content, indicating that the iron reduction effect is good. Furthermore, the silicate cementitious materials are mainly composed of calcium oxide, silicon dioxide, aluminum oxide, and magnesium oxide, and have the potential to be used as clinker in the manufacture of ordinary silicate cement.

[0048] XRD tests were performed on the silicate cementitious materials obtained in Examples 1-3, and the results are as follows: Figure 1 As shown. By Figure 1 It can be seen that after the molten steel slag is de-ironized, it reacts with the calcium modifier to undergo phase reconstruction, and its phase composition is tricalcium silicate (C3S), dicalcium silicate (C2S) and dicalcium aluminate (C2A).

[0049] Referring to GB / T20491 "Steel Slag Powder for Cement and Concrete", 20mm × 20mm × 20mm neat cement paste samples were prepared using the silicate cementitious materials obtained in Examples 1-3 and pure cement at a water-cement ratio of 0.5. When preparing the neat cement paste samples, 30wt% of the cement was replaced with the silicate cementitious materials obtained in Examples 1-3. After the curing time was reached, the samples were tested for compressive strength using a YAW-300D compressive strength testing machine. The compressive strengths at 3 days, 7 days, and 28 days were as follows: Figures 2-4 As shown.

[0050] Depend on Figures 2-4 It can be seen that the compressive strengths of the cement paste specimens prepared by replacing 30 wt% of cement with the silicate cementitious materials obtained in Examples 1 and 3 at 3 days, 7 days, and 28 days are similar to those of the cement paste specimens prepared with pure cement. However, the cement paste specimens prepared by replacing 30 wt% of cement with the silicate cementitious materials obtained in Example 2 have higher compressive strengths at 3 days and 7 days than those prepared with pure cement, while their 28-day compressive strength is slightly lower. This indicates that the silicate cementitious materials obtained by the method provided by this invention can all be used as clinker in the manufacture of ordinary silicate cement, and their performance is comparable to that of ordinary silicate cement.

[0051] Analysis of the gel materials provided in Comparative Examples 2-4 revealed that: in Comparative Example 2, since no calcium oxide was added, the gel material and iron were difficult to separate, and the gel material was mainly composed of dicalcium silicate, resulting in poor gelling activity and unsuitability for use as cement; in Comparative Examples 3 and 4, due to the lack of silica to adjust fluidity in the early stage, the electrolysis effect was very poor, the iron was not fully reduced, and the overall material remained the original black color of steel slag.

[0052] XRF tests were performed on the cementitious material obtained in Comparative Example 2, and the results are shown in Table 3: Table 3 shows the XRF of the cementitious materials obtained in Comparative Example 2.

[0053] As can be seen from Table 3, the silica content in the gel material obtained in Comparative Example 2 increased significantly, indicating that the gel material is mainly composed of dicalcium silicate, with poor gelling activity, and is not suitable for use as cement.

[0054] In summary, this invention directly recovers iron from molten steel slag through electrochemical reduction, and the silicate slag after component reconstruction is cooled to directly obtain silicate cementitious materials. The method provided by this invention simultaneously and efficiently utilizes the silicate components and heat in the molten steel slag, improving the utilization efficiency of the molten steel slag's materials and thermal energy, and reducing carbon emissions in the iron and steel metallurgical industry.

[0055] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing iron and cementitious materials by electrolysis of molten steel slag, characterized in that, The following steps are required: (1) Mix molten steel slag and silicon modifier to obtain mixed slag; (2) Electrolytically reduce the mixed slag obtained in step (1) to obtain modified slag with reconstructed composition and metallic iron; (3) After mixing the modified slag with the component reconstruction obtained in step (2) and calcium oxide, the mixture is cooled to room temperature to obtain silicate cementitious material; In step (1), the mass ratio of silicon modifier to molten steel slag is (0.0706~0.1392):1; In step (2), the reduction potential of electrolytic reduction is 0.4~10.0V, the current of electrolytic reduction is 5~15A, and the time of electrolytic reduction is 0.5~5h; The mass ratio of calcium oxide in step (3) to molten steel slag in step (1) is (0.1648~0.2833):

1.

2. The method according to claim 1, characterized in that, The molten steel slag in step (1) is the molten steel slag produced by converter steelmaking.

3. The method according to claim 1, characterized in that, The temperature of the molten steel slag in step (1) is 1450~1600℃.

4. The method according to claim 1, characterized in that, The silica modifier in step (1) includes any one or more of quartz sand, silica fume, and quartz waste.

5. The method according to claim 1 or 4, characterized in that, The silicon-based modifier contains 90-100% silicon dioxide by mass.

6. The method according to claim 1, characterized in that, In step (2), the anode and cathode during electrolytic reduction are independently high-temperature resistant conductive electrodes.

7. The method according to claim 6, characterized in that, The high-temperature resistant conductive electrode includes any one or more of graphite electrodes, platinum electrodes, rhodium electrodes, iridium electrodes, and silicon carbide electrodes.

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