A method for extracting magnesium from lf refining slag

Abstract

The application discloses a method for extracting Mg from LF refining slag, comprising the following steps: (1) placing the LF refining slag after casting in a vacuum chamber, adding a reducing agent to obtain mixed reaction materials; (2) vacuumizing the system, heating the mixed reaction materials and reacting; and the generated magnesium vapor is cooled into crude magnesium outside the vacuum chamber. The method realizes green and resource recycling of the LF refining slag, avoids defects in traditional hot reduction method for producing magnesium, rapidly produces high-value-added magnesium by using the waste heat of the LF refining slag, and realizes large-scale utilization of the LF refining slag after recycling the magnesium, so that the method is simple in process, low in cost, fluorine pollution in the production of Mg is avoided without adding fluorite as a mineralizer.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of metallurgy, and particularly relates to a method for extracting Mg from LF refining slag. BACKGROUND

[0002] LF refining slag is waste slag produced in the LF refining process. After most of the LF refining slag is recycled for metal Fe, the LF refining slag is stored as powder slag, which causes serious powdering dusting, occupies and pollutes land, is not conducive to environmental protection, and causes resource waste. At present, domestic and foreign scholars have made many studies on the LF refining slag recycling and utilization process, such as being used as a slagging agent for converter or electric furnace steelmaking, a building raw material, and the like. However, the existing research methods still have some defects: (1) due to the limitations of the workshop, hoisting equipment, product outline, and production organization, and the like, the hot slag recycling is relatively low, and changes between 20% and 50%, and the LF refining slag after recycling still needs to be discarded and treated; (2) after the LF refining slag is cooled and crushed, the heat cannot be fully utilized, and the next cycle uses cold slag material to form slag, which is slow and is not conducive to energy saving and consumption reduction; (3) the LF refining slag hot-state oxidation method slag desulfurization technology is difficult to realize due to the limitation of production space, and it is difficult to guarantee the high-temperature gas at 1300-1450℃; (4) the solid-state hydrothermal leaching method slag desulfurization wastes a large amount of cooling water and steel slag heat in the treatment process, and also causes secondary pollution.

[0003] Therefore, it is necessary to provide a high-value-added energy-saving and emission-reducing recycling method for hot-state LF refining slag, so as to achieve the purposes of circular production and zero emission. SUMMARY

[0004] The present application is based on the discovery and understanding of the inventors on the following facts and problems: at present, the LF refining slag has the problems of low recycling rate, low-value-added utilization, easy dusting during stacking, environmental pollution, and the like. The steel enterprises cannot fully utilize the LF refining slag, and the utilization rate of the LF refining slag is less than 20%, and even after one cycle, the LF refining slag is finally discarded, and the LF refining slag that cannot be recycled can only be poured into a slag tank to solidify and then transported to a slag yard for treatment together with converter slag or electric furnace slag. The steel slag contains P, and the ore blending is limited, and basically cannot be used for sintering, and can only be stacked after the metal Fe is recycled, which occupies and pollutes the land; a large amount of steel slag is discarded or used as raw material to produce cement and the like low-value-added products; the LF refining slag stacking causes serious powdering dusting, is not conducive to environmental protection, and causes resource waste.

[0005] The industrial magnesium production methods mainly include electrolysis method, carbon thermal reduction method, Pidgeon method and Magnetherm semi-continuous magnesium production process. Since the beginning of the 21st century, the industrial magnesium production method is mainly the Pidgeon method, and the Pidgeon method accounts for more than 80% of the global production. The traditional thermal reduction method for producing magnesium has some defects: (1) The production uses dolomite, magnesite and other mineral resources as raw materials, the resources are limited, and the mining process and generated mineral waste destroy the natural ecological environment; (2) The reactants silicon iron and calcined dolomite are subjected to solid phase chemical reaction, the reaction rate is slow, and the reduction reaction period is as long as 10-12 hours, and the efficiency is low; (3) The magnesium production process is carried out at high temperature, the raw materials are mixed at room temperature, then heated to the high temperature of 1200-1250 DEG C required for reaction, and the duration is long, a large amount of fuel is consumed, and the high-temperature calcined dolomite process is carried out separately, which further increases the fuel consumption and processing cost of the production process, the duration is long, and the energy consumption of the production process is large; (4) Flame external heating is adopted, heat is gradually conducted from the outside to the inside of the reactor, the production period is long, heat loss is large, the heat energy utilization rate is low, and the heat energy utilization rate of the typical process is only about 20%; (5) CaF2 is added in the production, which pollutes the environment. In addition, there are other defects such as serious smoke pollution in production, periodic intermittent production, difficulty in realizing automatic operation and large-scale production and the like.

[0006] In summary, how to green and resource recycling of LF refining slag, and how to avoid the defects of low efficiency of traditional thermal reduction method for producing magnesium need to be further explored and researched.

[0007] The embodiments of the present application aim to at least solve one of the technical problems in the related art. To this end, the embodiments of the present application propose a method for extracting Mg from LF refining slag, which can green and resource recycling of LF refining slag, can avoid the defects of traditional thermal reduction method for producing magnesium, can rapidly produce high value-added magnesium by using the waste heat of LF refining slag, and can be reused in steel production after recovering magnesium, realizes large-scale utilization of LF refining slag, has simple process and low cost, does not need to add fluorite as mineralizer, and avoids fluorine pollution problem in the production of Mg.

[0008] The embodiments of the present application propose a method for extracting Mg from LF refining slag, which comprises the following steps:

[0009] (1) The LF refining slag after pouring is placed in a vacuum chamber, a reducing agent is added, and a mixed reaction material is obtained;

[0010] (2) The system is vacuumized, the mixed reaction material is heated, and reaction is carried out; the generated magnesium vapor is cooled to form crude magnesium outside the vacuum chamber.

[0011] The method for extracting Mg from LF refining slag according to the embodiment of the present application has the following advantages and technical effects: 1. The method of the embodiment of the present application uses the LF refining slag after pouring as raw material. The LF refining slag is an industrial solid waste. The LF refining slag is used to replace the traditional industrial magnesium smelting raw material dolomite or magnesite and other mineral resources, thereby saving the non-renewable mineral resources, realizing waste recycling, reducing the cost, reducing the storage of the LF refining slag and environmental pollution, and achieving environmental protection and energy saving. 2. The method of the embodiment of the present application uses the LF refining slag after pouring to be reduced under the condition of vacuum and high temperature. Since the LF refining slag after pouring has high residual temperature, the raw material LF refining slag itself contains a large amount of sensible heat, which can preheat the reducing agent and provide part of the energy for the reaction of the MgO in the LF refining slag. After adding part of the heat, the needs of the reduction reaction can be met, and the residual temperature of the LF refining slag after pouring is fully utilized. 3. The method of the embodiment of the present application has a fast reaction rate and high efficiency. The raw material does not need to be mixed at room temperature and then heated to a high temperature required for the reaction. The heat is conducted through the raw material itself, the heat loss is small, the heat energy utilization rate is high, the fuel is saved, and the production energy consumption can be greatly reduced. 4. In the method of the embodiment of the present application, the raw material LF refining slag is subjected to a high-temperature slagging process, thereby reducing the activation energy of the reaction and increasing the reaction speed. Therefore, fluorite mainly composed of CaF2 does not need to be added to play a role in catalyzing the reaction, and the pollution of fluorine to the environment is avoided, thereby fundamentally avoiding the fluorine pollution problem in the process of producing Mg by using the traditional process.

[0012] In some embodiments, in the step (1), the reducing agent comprises FeSi powder.

[0013] In some embodiments, in the step (1), the Si content in the FeSi powder is 72wt%-78wt%.

[0014] In some embodiments, in the step (1), the adding amount of the reducing agent is 4wt%-8wt% of the LF refining slag.

[0015] In some embodiments, in the step (1), the temperature of the LF refining slag after pouring is above 1200℃.

[0016] In some embodiments, in the step (1), the LF refining slag after pouring is poured from a ladle into a slag tank, and then placed in a vacuum chamber. The slag tank is used as a reaction container, the reducing agent is added in batches, and the mixture is uniformly mixed to obtain a mixed reaction material.

[0017] In some embodiments, in the step (2), the vacuum degree of the vacuum chamber is 5-20Pa.

[0018] In some embodiments, in the step (2), the temperature is heated to 1200-1300℃.

[0019] In some embodiments, the reaction time in step (2) is 1-3 hours.

[0020] The embodiment of the present application also provides an application of the LF refining slag in extracting Mg, and the Mg is extracted by the method of the embodiment of the present application. In the embodiment of the present application, the application range of the LF refining slag is expanded, the LF refining slag is recycled in a green and resourceful way, the defects in the traditional hot reduction method for producing Mg are avoided, the high value-added Mg is rapidly produced by using the waste heat of the LF refining slag, the recycled Mg is reused in steelmaking, the large-scale utilization of the LF refining slag is realized, the process is simple, the cost is low, no fluorite is added as a mineralizer, and the fluorine pollution problem in the production of Mg is avoided. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is an implementation flowchart of the method for extracting Mg by the LF refining slag of the embodiment of the present application. DETAILED DESCRIPTION

[0022] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0023] As shown in Figure 1 The method for extracting Mg by the LF refining slag of the embodiment of the present application comprises the following steps:

[0024] (1) The LF refining slag after pouring is placed in a vacuum chamber, a reducing agent is added, and a mixed reaction material is obtained;

[0025] (2) The system is vacuumized, the mixed reaction material is heated, and reaction is performed; the generated magnesium vapor is cooled into crude magnesium outside the vacuum chamber.

[0026] The method for extracting Mg from LF refining slag according to the embodiment of the present application uses the LF refining slag after pouring as raw material, and the LF refining slag is an industrial solid waste. The method replaces the traditional industrial magnesium smelting raw material dolomite or magnesite and other mineral resources, saves the non-renewable mineral resources, realizes waste recycling, has low cost, reduces the storage of LF refining slag and environmental pollution, and is environmentally friendly and energy-saving. The method according to the embodiment of the present application uses the LF refining slag after pouring to reduce under the condition of vacuum and high temperature. Since the LF refining slag after pouring has high afterheat, the raw material LF refining slag itself contains a large amount of sensible heat, can preheat the reducing agent, and provides part of the energy for the reaction of MgO in the LF refining slag. After adding part of the heat, the needs of the reduction reaction can be met, and the afterheat of the LF refining slag after pouring is fully utilized. The method according to the embodiment of the present application has fast reaction rate and high efficiency. The raw material does not need to be mixed at room temperature and then heated to high temperature required for the reaction in cold state. The heat is conducted through the raw material itself, the heat loss is small, the heat energy utilization rate is high, fuel is saved, and the production energy consumption can be greatly reduced. In the method according to the embodiment of the present application, the raw material LF refining slag is subjected to a high-temperature slagging process, the activation energy of the reaction is reduced, the reaction speed is fast, and therefore, fluorite mainly composed of CaF2 does not need to be added, which can play a role in catalyzing the reaction and avoid the pollution of fluorine to the environment, fundamentally avoiding the fluorine pollution problem in the process of producing Mg by the traditional process.

[0027] In some embodiments, the reducing agent in step (1) includes FeSi powder. In the embodiment of the present application, the reducing agent includes FeSi powder, the raw material LF refining slag itself contains a large amount of sensible heat, can preheat the FeSi powder, and provides part of the energy for the reaction of MgO in the LF refining slag. After adding part of the heat, the needs of the reduction reaction can be met. In addition, the raw material LF refining slag is subjected to a high-temperature slagging process, the activation energy of the reaction is reduced, the reaction speed is fast, and therefore, fluorite mainly composed of CaF2 does not need to be added, which can play a role in catalyzing the reaction.

[0028] In some embodiments, the Si content in the FeSi powder in step (1) is 72wt%-78wt%, and specifically, for example, 72wt%, 73wt%, 74wt%, 75wt%, 76wt%, 77wt%, 78wt%, and preferably, 75# FeSi. In the embodiment of the present application, the Si content in the FeSi powder is further preferred, which is beneficial to further improve the efficiency of extracting Mg, promote the reaction, reduce the energy consumption, and shorten the production cycle.

[0029] In some embodiments, in the step (1), the amount of the reducing agent added is 4wt%-8wt% of the LF refining slag, specifically, for example, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%. In the embodiments of the present application, too much FeSi powder added will significantly increase the production cost, and too little FeSi powder added will result in too low reduction rate of Mg, which cannot extract the magnesium in the LF refining slag sufficiently, and the magnesium recovery rate is low. By further optimizing the amount of the reducing agent added, it is beneficial to further improve the extraction efficiency of Mg, improve the magnesium recovery rate, reduce the cost, reduce the energy consumption, and shorten the production cycle.

[0030] In some embodiments, in the step (1), the temperature of the LF refining slag after casting, i.e., the LF refining slag returned after casting, is above 1200°C. In the embodiments of the present application, the temperature of the LF refining slag after casting is above 1200°C, which can fully utilize the large amount of sensible heat contained in the LF refining slag itself, preheat the reducing agent, and provide part of the energy for the reaction with MgO in the LF refining slag, so that only part of the heat needs to be supplemented to meet the needs of the reduction reaction, and the waste heat of the LF refining slag after casting is fully utilized.

[0031] In some embodiments, in the step (1), the reducing agent is added in batches. In the embodiments of the present application, adding the reducing agent in batches is beneficial to the full and efficient progress of the reduction reaction.

[0032] In some embodiments, in the step (1), the LF refining slag after casting is poured from a ladle into a slag pot, and then placed in a vacuum chamber; the slag pot is used as a reaction container, the reducing agent is added in batches, and mixed to obtain a mixed reaction material. In the embodiments of the present application, the slag pot is directly used as a reaction container, without the need for further production investment in equipment, which is beneficial to production management and cost reduction.

[0033] In some embodiments, in the step (2), the vacuum chamber is evacuated, and then the mixed reaction material is heated; preferably, the vacuum degree of the vacuum chamber is 5-20Pa, specifically, for example, 5Pa, 6Pa, 8Pa, 10Pa, 12Pa, 13Pa, 15Pa, 18Pa, 20Pa. In the embodiments of the present application, the vacuum degree is optimized, which is beneficial to improve the extraction efficiency of Mg and improve the recovery rate of Mg.

[0034] In some embodiments, in the step (2), heating to 1200-1300℃, specifically, for example, 1200℃, 1220℃, 1250℃, 1270℃, 1290℃, 1300℃; the reaction time is 1-3 hours, specifically, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours. In the embodiment of the present application, the raw material LF refining slag itself contains a large amount of sensible heat, only a part of heat needs to be supplemented after heating to meet the needs of the reduction reaction, the reaction rate is fast, the production cycle is short, the efficiency is high, and the Mg recovery rate is high. By optimizing the heating temperature and the reaction time, the extraction efficiency of Mg is further improved, and the Mg recovery rate is improved.

[0035] In some embodiments, in the step (2), under the suction of the vacuum system, the magnesium vapor condenses into crude magnesium at the cooling end outside the vacuum chamber.

[0036] The embodiment of the present application also proposes an application of the LF refining slag in extracting Mg, and Mg is extracted by the method of the embodiment of the present application. In the embodiment of the present application, the application range of the LF refining slag is expanded, green and resource recycling of the LF refining slag are realized, the defects of the traditional hot reduction method for producing Mg are avoided, the residual heat of the LF refining slag is utilized to rapidly produce high-value-added Mg, the recovered Mg is re-applied to steelmaking production, large-scale utilization of the LF refining slag is realized, the process is simple, the cost is low, fluorite as a mineralizer is not needed to be added, and the fluorine pollution problem in the production of Mg is avoided.

[0037] The present application is described below with reference to specific embodiments, and it should be noted that these embodiments are merely descriptive and do not limit the present application in any way.

[0038] Taking 260t LF production as an example, the amount of LF refining slag is usually calculated as 3t / furnace. The temperature of the LF refining slag returned from the ladle after pouring is above 1200℃.

[0039] Embodiment 1

[0040] (1) Reducing agent batching: FeSi powder with a Si content of 75wt% is added, and the FeSi powder is added at 8wt% of the LF refining slag, and the amount added is 240kg;

[0041] (2) The LF refining slag after pouring is poured from the ladle into the slag tank and transported to the vacuum chamber. The slag tank is used as a reaction container, the temperature of the LF refining slag returned after pouring is above 1200℃, FeSi powder is added in batches, and then the mixture is uniformly mixed to obtain a mixed reaction material;

[0042] (3) The system is vacuumized, the vacuum degree is 20 Pa, the mixed reaction material in the slag tank is heated to 1300 °C in the vacuum chamber, and the reaction is kept for 1 hour. Under the suction of the vacuum system, the magnesium vapor generated by the reaction is condensed into crude magnesium at the cooling end outside the vacuum chamber for recovery.

[0043] The main components of the LF refining slag before and after the reaction are shown in Table 1.

[0044] Table 1: Main components of the LF refining slag before and after the reaction

[0045] Slag sample CaO (wt%) SiO2 (wt%) MgO (wt%) Al2O3 (wt%) Before reduction to Mg 49 11 9 27 After reduction Example 1 47 14 3.8 26

[0046] The Mg recovery rate is 55% through the method of the embodiment.

[0047] Example 2

[0048] (1) Reducing agent batching: FeSi powder with a Si content of 78 wt% is added, and the FeSi powder is added at 4 wt% of the LF refining slag, with an addition amount of 120 kg;

[0049] (2) The LF refining slag after pouring is poured from the ladle into the slag tank and transported to the vacuum chamber. The slag tank is used as a reaction container, the temperature of the LF refining slag returned after pouring is above 1200 °C, the FeSi powder is added in batches, then the mixture is uniformly mixed to obtain a mixed reaction material;

[0050] (3) The system is vacuumized, the vacuum degree is 5 Pa, the mixed reaction material in the slag tank is heated to 1200 °C in the vacuum chamber, and the reaction is kept for 3 hours. Under the suction of the vacuum system, the magnesium vapor generated by the reaction is condensed into crude magnesium at the cooling end outside the vacuum chamber for recovery.

[0051] The main components of the LF refining slag before and after the reaction are shown in Table 2.

[0052] Table 2: Main components of the LF refining slag before and after the reaction

[0053] Slag sample CaO (wt%) SiO2(wt%) MgO (wt%) Al2O3 (wt%) Before reduction to Mg 48 10 7 29 After reduction Example 2 44 17 3.4 26

[0054] The Mg recovery rate is 50% through the method of the embodiment.

[0055] Example 3

[0056] (1) Reducing agent batching: FeSi powder with a Si content of 72 wt% is added, and the FeSi powder is added at 6 wt% of the LF refining slag, with an addition amount of 180 kg;

[0057] (2) The LF refining slag after pouring is poured from the ladle into the slag tank and transported to the vacuum chamber. The slag tank is used as a reaction container, the temperature of the LF refining slag returned after pouring is above 1200 °C, the FeSi powder is added in batches, then the mixture is uniformly mixed to obtain a mixed reaction material;

[0058] (3) The system is vacuumized to 13 Pa, and the mixed reaction materials in the ladle are heated to 1250 °C in the vacuum chamber, and the reaction is kept for 2 hours. Under the suction of the vacuum system, the magnesium vapor generated by the reaction is condensed into crude magnesium at the cooling end outside the vacuum chamber.

[0059] The main components of the LF refining slag before and after the reaction are shown in Table 3.

[0060] Table 3: Main components of the LF refining slag before and after the reaction

[0061] Slag sample CaO (wt%) SiO2(wt%) MgO (wt%) Al2O3 (wt%) Before reduction to Mg 46 11 8 30 After reduction Example 3 44 14 3.6 29

[0062] The Mg recovery rate is 53% through the method of the embodiment.

[0063] Example 4

[0064] The method is the same as that of Example 1, except that in the step (1):

[0065] The FeSi powder is added at 10% by weight of the LF refining slag.

[0066] The main components of the LF refining slag before and after the reaction are shown in Table 4.

[0067] Table 4: Main components of the LF refining slag before and after the reaction

[0068] Slag sample CaO (wt%) SiO2(wt%) MgO (wt%) Al2O3 (wt%) Before reduction to Mg 49 11 9 27 After reduction Example 4 46 13 3.9 25

[0069] The Mg recovery rate is 54% through the method of the embodiment.

[0070] Comparative Example 1

[0071] (1) Reducing agent preparation: FeSi powder with a Si content of 75% by weight is added, and the FeSi powder is added at 1% by weight of the LF refining slag, with an addition amount of 30 kg;

[0072] (2) The LF refining slag after pouring is poured from the ladle into the ladle, and is transported to the vacuum chamber. The ladle is used as a reaction container, and the LF refining slag after pouring is kept at a temperature of 1200 °C or higher, and then the FeSi powder is added in batches, and then the mixture is uniformly mixed to obtain the mixed reaction materials.

[0073] (3) The system is vacuumized to 5 Pa, and the mixed reaction materials in the ladle are heated to 1200 °C in the vacuum chamber, and the reaction is kept for 3 hours. Under the suction of the vacuum system, the magnesium vapor generated by the reaction is condensed into crude magnesium at the cooling end outside the vacuum chamber.

[0074] The main components of the LF refining slag before and after the reaction are shown in Table 5.

[0075] Table 5: Main components of the LF refining slag before and after the reaction

[0076] Slag sample CaO (wt%) SiO2(wt%) MgO (wt%) Al2O3 (wt%) Before reduction to Mg 49 11 9 27 After reduction Comparative Example 1 48 12 8 27

[0077] The Mg recovery rate was 10% by the method of Comparative Example 1.

[0078] In the present application, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. mean that the specific feature, structure, material or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Also, the specific feature, structure, material or characteristic described can be combined in any appropriate manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in the present specification and the features of the different embodiments or examples can be combined and combined by those skilled in the art without contradiction.

[0079] Although the above embodiments have been shown and described, it is to be understood that the above embodiments are exemplary, and are not to be construed as limiting the present application, and the changes, modifications, replacements and variations of the above embodiments made by those skilled in the art are within the scope of the present application.

Claims

1. A method for extracting Mg from LF refining slag, characterized by, The method comprises the following steps: (1) placing the cast LF refining slag in a vacuum chamber, adding a reducing agent to obtain a mixed reaction material; the temperature of the cast LF refining slag is above 1200℃; (2) vacuumizing the system, heating and reacting the mixed reaction material; the generated magnesium vapor is cooled into crude magnesium outside the vacuum chamber.

2. The method of extracting Mg from LF refining slag according to claim 1, characterized by, In the step (1), the reducing agent comprises FeSi powder.

3. The method of extracting Mg from LF refining slag according to claim 2, characterized by, In the step (1), the Si content in the FeSi powder is 72wt%-78wt%.

4. The method of extracting Mg from LF refining slag according to claim 1, characterized by, In the step (1), the adding amount of the reducing agent is 4wt%-8wt% of the LF refining slag.

5. The method of extracting Mg from LF refining slag according to claim 1, characterized by, In the step (1), the cast LF refining slag is poured from a ladle into a slag pot, and then placed in the vacuum chamber; the slag pot is used as a reaction container, the reducing agent is added in batches, mixed, and the mixed reaction material is obtained.

6. The method of extracting Mg from LF refining slag according to claim 1, characterized by, In the step (2), the vacuum degree of the vacuum chamber is 5-20Pa.

7. The method of extracting Mg from LF refining slag according to claim 1, characterized by, In the step (2), the heating is to 1200-1300℃.

8. The method of extracting Mg from LF refining slag according to claim 1, characterized by, In the step (2), the reaction time is 1-3 hours.

9. Use of an LF refining slag for the extraction of Mg, characterized in that, Mg is extracted by the method in any one of claims 1-8.

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