A method for extracting mg and al using lf refining slag

Abstract

The application discloses a method for extracting Mg and Al by using LF refining slag, and comprises the following steps: a, pouring the LF refining slag after casting into a slag tank from a ladle, placing the slag tank in a vacuum chamber, adding a reducing agent into the LF refining slag to obtain mixed reaction materials; b, after vacuum extraction, heating the mixed reaction materials in the slag tank to generate reaction, and condensing gaseous Mg and Al at an external cooling end of the vacuum chamber to obtain solid Mg and Al. The method uses the LF refining slag as raw material, and effectively utilizes the waste heat to produce high-value-added Mg and Al, so that the green treatment problem of the LF refining slag is solved, the shortcomings of the traditional hot reduction method for producing Mg are avoided, the recovered Mg and Al can be applied to steelmaking production again, higher economic benefits are obtained, and the large-scale utilization problem of the LF refining slag is solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of utilization of steelmaking slag, and particularly relates to a method for extracting Mg and Al by using LF refining slag. BACKGROUND

[0002] The top slag of the ladle after LF refining has the characteristics of high basicity, good metallurgical properties, reasonable composition and fast slagging, and the sulfur in most of the slag is not saturated, so the slag can be returned to the refining process for secondary or even tertiary utilization.

[0003] At present, domestic and foreign scholars have made a lot of researches on the LF refining slag recycling utilization process, but no steel enterprise can fully recycle the LF refining slag, and the recycling rate is less than 20%, and the LF slag that cannot be recycled can only be poured into the slag tank and then transported to the slag field, and finally treated together with the converter slag or the electric furnace slag. Because the steel slag contains P, the ore matching is limited, and the steel slag cannot be used for sintering. After the Fe metal is recovered, the powder slag can only be stored, which occupies and pollutes the land. A large amount of steel slag is abandoned or used as raw materials to produce cement and other low-value-added products. Because the dusting is serious, it is not conducive to environmental protection and causes resource waste. It has brought serious troubles to the society and environment, and has become a major obstacle to social progress and economic development.

[0004] Therefore, it is necessary to provide a high-value-added energy-saving and emission-reducing method for recycling LF refining slag, solve the problems of low LF refining slag recycling rate, easy dusting, great pollution to the environment and low-value-added utilization, realize high-value-added recycling of LF refining slag, and finally achieve the purpose of circular production and zero emission. SUMMARY

[0005] The present application is based on the discovery and understanding of the inventors on the following facts and problems: in the related art, the research methods for recycling LF refining slag all have some defects, mainly as follows: (1) refining hot slag recycling process, many steel enterprises have implemented hot recycling test of residual steel slag after refining, but the hot slag recycling rate is low due to the limitations of plant, hoisting equipment, product outline and production organization and other conditions; (2) solid-state recycling of refining slag after cooling and crushing, the heat cannot be fully utilized, and the cold slag material is used for slagging in the next cycle, which is slow and is not conducive to energy saving and consumption reduction; (3) the LF refining slag hot-state oxidation method for removing S 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 for removing S wastes a large amount of cooling water and steel slag heat in the treatment process, and also causes secondary pollution.

[0006] The main industrial magnesium production methods are electrolysis, carbon thermal reduction, Pidgeon process and Magnetherm semi-continuous magnesium production process. The carbon thermal reduction method was only used in the factories in the 1930s-1940s, and the main industrial methods in the world are electrolysis and Pidgeon process. Before the mid-1990s, the electrolysis method accounted for more than 80% of the global magnesium production, and the Pidgeon and Magnetherm methods accounted for about 20%. Since the beginning of the 21st century, the Magnetherm process has basically stopped production, and the electrolysis method has shrunk a lot, and only the Pidgeon method accounts for more than 80% of the global production.

[0007] The thermal reduction method is one of the methods for producing metal Mg, which mainly uses dolomite, magnesite and the like as raw materials, and sinters MgO in the middle section of the kiln, and then adds a reducing agent to reduce to metal magnesium in a reduction furnace. The Pidgeon process is widely used at home and abroad to produce magnesium, that is, calcined dolomite (MgO, CaO) is used as raw material, silicon iron is used as reducing agent, and the mixture is ground into fine powder, pressed into briquettes, and then loaded into a reduction tank to produce magnesium vapor in a reduction furnace. The condensed crystalline solid magnesium is melted into magnesium ingots. The advantages of this method are simple, and the disadvantages are that the raw materials are mixed after cooling and then heated, and the production process consumes a lot of energy. The calcined dolomite and the thermal reduction magnesium production process are both carried out at high temperature for a long time, which consumes a large amount of fuel, and the two processes are carried out separately, which further increases the fuel consumption and processing cost of the production process.

[0008] Both the Pidgeon process and the Magnetherm semi-continuous magnesium production process of France use silicon iron, especially silicon iron containing more than 75% of silicon (usually 75 # Silicon iron) as a reducing agent, and MgO-containing ore as a magnesium production raw material, and then mixed with a mineralizer (CaF2) in a certain proportion, ground and mixed, and pressed into balls, and then the balls are loaded into a reduction tank, and the reaction occurs in the tank at high temperature and high vacuum (1200°C, 13Pa) to form Mg vapor, and the Mg vapor is crystallized to form metal Mg. The role of the mineralizer (CaF2) is to reduce the temperature at which the liquid phase appears to accelerate the reaction rate.

[0009] The chemical reaction of Si reducing MgO under high temperature and vacuum conditions is shown in formula (1).

[0010] 2MgO + Si = SiO2 + 2Mg(gas) (1)

[0011] The disadvantages of the traditional hot reduction method for producing Mg are: 1) the production uses dolomite, magnesite and the like as raw materials, and the mining process destroys the natural ecological environment; 2) the dolomite, magnesite and the like need to be calcined into MgO in the middle section of the kiln, and the calcination is carried out at high temperature for a long time, which needs to consume a large amount of fuel, and the fuel consumption and processing cost of the production process are large; 3) the hot reduction magnesium production process needs to mix the raw materials from room temperature, and then heat to the high temperature of 1200-1250 DEG C required for reaction in cold state, which needs to consume a large amount of fuel, and is carried out separately with the process of 1), which further increases the fuel consumption and processing cost of the production process; 4) the Pidgeon method uses external heating, and the heat is gradually conducted from the outside to the inside of the reactor, which has a long production cycle, large heat loss, low heat energy utilization rate, and the analysis shows that the heat energy utilization rate of the typical process is only about 20%; 5) the production process has serious smoke pollution, the working environment is poor, and the surrounding ecological environment is deteriorated; 6) CaF2 needs to be added in the production, which pollutes the environment.

[0012] Aluminum and aluminum alloy are one of the most economical and applicable materials with very wide application at present. Because of the strong activity of aluminum, it can only be produced on a large scale by electrolysis at present. The electrolytic aluminum process has high energy consumption and cost, so researchers have been looking for various ways to economically produce aluminum.

[0013] The present application aims 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 and Al by using LF refining slag, which uses LF refining slag as raw material and effectively uses the residual heat to produce high value-added Mg and Al, not only solving the green treatment problem of LF refining steel slag, but also avoiding the disadvantages of the traditional hot reduction method for producing Mg, and the recovered Mg and Al can be re-applied to steel production, which not only obtains higher economic benefits, but also solves the problem of large-scale utilization of LF refining steel slag.

[0014] The method for extracting Mg and Al by using LF refining slag according to the embodiments of the present application comprises the following steps:

[0015] a. Pouring the LF refining slag after pouring into a slag tank from a ladle, placing it in a vacuum chamber, adding a reducing agent to the LF refining slag for mixing to obtain a mixed reaction material;

[0016] b. After vacuum extraction, the mixed reaction material in the slag tank is heated to react, and the generated gaseous Mg and Al are condensed and recovered at the external cooling end of the vacuum chamber.

[0017] The method for extracting Mg and Al by using LF refining slag has the following advantages and technical effects: 1. In the method, the LF refining slag after pouring is used as raw material, which is low in cost and almost free of cost. Moreover, the LF refining slag has high residual temperature, and a large amount of sensible heat is contained in the steel slag. The LF refining slag is used to preheat the reducing agent, and part of the energy required for the reaction of MgO and Al2O3 in the slag is provided. After additional addition of part of heat, the reducing reaction can be met, and the heat is fully and effectively utilized, thereby saving a large amount of energy; 2. In the method, the LF refining slag after pouring is used as raw material to extract Mg and Al. The LF refining slag is industrial solid waste, and is used to replace industrial raw materials such as dolomite, magnesite and aluminum ore, thereby realizing waste utilization and saving non-renewable mineral resources; 3. The method effectively solves the problem of recycling and reuse of LF refining steel slag, realizes green treatment, avoids the technical defects in traditional production of Mg and Al, and realizes that the recovered Mg and Al can be applied to steel production again, thereby achieving high economic benefits, providing a new direction for large-scale utilization of LF refining steel slag; 4. The method has simple process, low cost, energy saving and environmental protection, and is easy to be applied to large-scale industrial application, and has wide prospects.

[0018] In some embodiments, the temperature of the LF refining slag in step a is not less than 1200℃.

[0019] In some embodiments, the reducing agent in step a is FeSi powder.

[0020] In some embodiments, the Si content in the FeSi powder is 72wt%-78wt%.

[0021] In some embodiments, the adding amount of the FeSi powder in step a is 20wt%-30wt% of the LF refining slag.

[0022] In some embodiments, the reducing agent is added into the LF refining slag in batches in step a.

[0023] In some embodiments, the vacuum degree of the vacuum chamber in step b is 5-20Pa.

[0024] In some embodiments, the reaction temperature in step b is 1300-1500℃.

[0025] In some embodiments, the reaction time in step b is 1-3 hours. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The process flow diagram of the method for extracting Mg and Al by using LF refining slag is shown. DETAILED DESCRIPTION

[0027] The embodiments of the present application are described in detail below, which are exemplary and intended to explain the present application, and cannot be understood as a limitation of the present application.

[0028] As shown in the method for extracting Mg and Al by using LF refining slag in the embodiments of the present application, the method comprises the following steps: Figure 1

[0029] a. Pouring the LF refining slag after casting from a ladle into a slag tank, placing the slag tank in a vacuum chamber, adding a reducing agent into the LF refining slag for mixing to obtain a mixed reaction material;

[0030] b. After vacuum extraction, heating the mixed reaction material in the slag tank to generate a reaction, and condensing and recovering the generated gaseous Mg and Al at an external cooling end of the vacuum chamber.

[0031] In the method for extracting Mg and Al by using LF refining slag in the embodiments of the present application, the LF refining slag after casting is used as raw material, which is low in cost and almost zero, and the LF refining slag has high residual heat, a large amount of sensible heat is contained in the steel slag, the reducing agent is preheated by using the LF refining slag, and part of the energy required for the reaction of MgO and Al2O3 in the slag is provided, and after additional addition of part of heat, the reducing reaction can be met, and the heat is fully and effectively utilized, and a large amount of energy is saved; in the method in the embodiments of the present application, the LF refining slag after casting is used as raw material to extract Mg and Al, the LF refining slag is industrial solid waste, and the industrial raw materials dolomite, magnesite and aluminum ore are replaced, waste utilization is realized, and non-renewable mineral resources are saved; the method in the embodiments of the present application effectively solves the problem of recycling and reusing of LF refining steel slag, realizes green treatment, avoids the technical defects of traditional production of Mg and Al, and the recovered Mg and Al can be re-applied to steel production, achieves high economic benefits, and provides a new direction for large-scale utilization of LF refining steel slag; the method in the embodiments of the present application is simple in process, low in cost, energy-saving and environment-friendly, easy to be applied in large-scale industry, and has a broad prospect.

[0032] In some embodiments, the temperature of the LF refining slag in step a is not less than 1200℃. In the method in the embodiments of the present application, the temperature of the LF refining slag after casting basically reaches 1200℃ or above, a large amount of sensible heat is contained, the reducing agent can be preheated by using the residual heat of the LF refining slag, and most of the energy required for the reaction of MgO and Al2O3 can be provided, so that the heat of the LF refining slag is fully utilized, a large amount of energy is saved, and energy saving and environmental protection are achieved.

[0033] ​In some embodiments, the reducing agent in step a is FeSi powder, preferably, the Si content in the FeSi powder is 72wt%-78wt%. Further preferably, the amount of the FeSi powder added is 20wt%-30wt% of the LF refining slag. Preferably, the reducing agent is added to the LF refining slag in batches. The amount of the reducing agent in the method of the embodiments of the present application can further improve the heat utilization rate of the LF refining slag and improve the extraction and recovery rate of Mg and Al.

[0034] In some embodiments, the vacuum degree of the vacuum chamber in step b is 5-20Pa, the reaction temperature is 1300-1500℃, and the reaction time is 1-3 hours. In the method of the embodiments of the present application, the LF refining slag and the reducing agent are reacted in a vacuum environment, which can fully utilize the residual heat of the LF refining slag, only a part of heat needs to be supplemented to obtain the total energy required for the reduction reaction, and Mg and Al are extracted from the LF refining slag.

[0035] The present application will be described in detail below with reference to the embodiments.

[0036] The 260t LF of a certain steel plant has 3t of LF refining slag per furnace, and the temperature of the LF refining slag returned from the ladle after casting is 1200-1250℃.

[0037] Embodiment 1

[0038] (1) Reducing agent preparation: FeSi powder with a Si content of 75wt% is added, and the amount of the FeSi powder is 20wt% of the amount of the LF refining slag, and the amount added is 600kg;

[0039] (2) The LF refining slag after casting is poured from the ladle into a slag pot and transported to a vacuum chamber. The slag pot is used as a reaction container, the temperature of the LF refining slag is 1220℃, the prepared FeSi powder is added to the LF refining slag in batches, and then the mixture is uniformly mixed.

[0040] (3) The system is evacuated, the vacuum degree is 19Pa (absolute pressure), the reaction raw materials in the slag pot are heated to 1500℃ in the vacuum chamber, and the temperature is maintained for 1 hour. Under the suction force of the vacuum system, the gaseous Mg and Al generated by the reaction are condensed into solid Mg and Al respectively at the cooling end outside the vacuum chamber and are recovered.

[0041] The main components of the LF refining slag before and after the reaction in this embodiment are shown in Table 1. As can be seen from Table 1, Mg and Al in the LF refining slag after the reaction are effectively extracted and recovered, the MgO content in the LF refining slag is as low as 2.3%, and the Al2O3 content is reduced to 6.2%.

[0042] Table 1

[0043] LF refining slag CaO (wt%) SiO2(wt%) MgO (wt%) Al2O3 (wt%) Before reduction 49 11 9 27 After reduction 42 32 2.3 6.2

[0044] The Mg recovery rate is 73% and the Al recovery rate is 76% in the method of the embodiment.

[0045] Embodiment 2

[0046] (1) Reducing agent preparation: FeSi powder with Si content of 78wt% is added, and the amount of FeSi powder is 25wt% of the amount of LF refining slag, and the added amount is 750kg;

[0047] (2) The poured LF refining slag is poured from the ladle into the slag pot and transported to the vacuum chamber. The slag pot is used as a reaction container, the temperature of the LF refining slag is 1210℃, and the prepared FeSi powder is added into the LF refining slag in batches, and then the mixture is uniformly mixed.

[0048] (3) The system is vacuumized, the vacuum degree is 15Pa, the reaction raw materials in the slag pot are heated to 1400℃ in the vacuum chamber, and the vacuum system is kept for 2 hours. Under the suction force of the vacuum system, the gaseous magnesium and aluminum generated by the reaction are condensed into solid Mg and Al respectively at the cooling end outside the vacuum chamber.

[0049] The main components of the LF refining slag before and after the reaction in the embodiment are shown in Table 2. As can be seen from Table 2, Mg and Al in the LF refining slag after the reaction are effectively extracted and recovered, the content of MgO in the LF refining slag is as low as 2%, and the content of Al2O3 is reduced to 8%.

[0050] Table 2

[0051] LF refining slag CaO (wt%) SiO2(wt%) MgO (wt%) Al2O3 (wt%) Before reduction 48 10 7 29 After reduction 41 37 2 8

[0052] The Mg recovery rate is 68% and the Al recovery rate is 69% in the method of the embodiment.

[0053] Embodiment 3

[0054] (1) Reducing agent preparation: FeSi powder with Si content of 72wt% is added, and the amount of FeSi powder is 30wt% of the amount of LF refining slag, and the added amount is 900kg;

[0055] (2) The poured LF refining slag is poured from the ladle into the slag pot and transported to the vacuum chamber. The slag pot is used as a reaction container, the temperature of the LF refining slag is 1210℃, and the prepared FeSi powder is added into the LF refining slag in batches, and then the mixture is uniformly mixed.

[0056] (3) The system is vacuumized, the vacuum degree is 6Pa, the reaction raw materials in the slag pot are heated to 1301℃ in the vacuum chamber, and the vacuum system is kept for 3 hours. Under the suction force of the vacuum system, the gaseous magnesium and aluminum generated by the reaction are condensed into solid Mg and Al respectively at the cooling end outside the vacuum chamber.

[0057] The main components of the LF refining slag before and after the reaction of the example are shown in Table 3. As can be seen from Table 3, Mg and Al in the LF refining slag after the reaction are effectively extracted and recovered, the content of MgO in the LF refining slag is as low as 1.5%, and the content of Al2O3 is reduced to 7%.

[0058] Table 3

[0059] LF refining slag CaO (wt%) SiO2(wt%) MgO (wt%) Al2O3 (wt%) Before reduction 46 11 8 30 After reduction 37 32 1.5 7

[0060] It is calculated that the Mg recovery rate in the method of the example is 78%, and the Al recovery rate is 73%.

[0061] Comparative Example 1

[0062] (1) Reducing agent batching: FeSi powder with a Si content of 75wt% is added, and the amount of FeSi powder is 5wt% of the amount of LF refining slag, and the amount added is 150kg;

[0063] (2) The LF refining slag after pouring is poured from the ladle into the slag pot and transported to the vacuum chamber. The slag pot is used as a reaction container, the temperature of the LF refining slag is 1210℃, and the prepared FeSi powder is added to the LF refining slag in batches, and then the mixture is uniformly mixed.

[0064] (3) The system is vacuumed, the vacuum degree is 19Pa, the reaction raw materials in the slag pot are heated to 1500℃ in the vacuum chamber, and the temperature is kept for 1 hour. Under the suction force of the vacuum system, the gaseous magnesium and aluminum generated by the reaction are condensed into solid Mg and Al respectively at the cooling end outside the vacuum chamber.

[0065] The main components of the LF refining slag before and after the reaction of the example are shown in Table 3. As can be seen from Table 3, Mg and Al in the LF refining slag after the reaction are effectively extracted and recovered, the content of MgO in the LF refining slag is as low as 1.5%, and the content of Al2O3 is reduced to 7%.

[0066] Table 4

[0067] LF refining slag CaO (wt%) SiO2(wt%) MgO (wt%) Al2O3 (wt%) Before reduction 49 11 9 27 After reduction 49 18 6.7 21

[0068] It is calculated that the Mg recovery rate in the method of the example is 78%, and the Al recovery rate is 73%.

[0069] Comparative Example 2

[0070] The method is the same as that of Example 3, except that the reducing agent is added at 35wt% of the LF refining slag, and the amount added is 1050kg of FeSi powder with a Si content of 78wt%.

[0071] The main components of the LF refining slag before and after the reaction are shown in Table 5.

[0072] Table 5

[0073] LF refining slag CaO (wt%) SiO2(wt%) MgO (wt%) Al2O3 (wt%) Before reduction 46 11 8 30 After reduction LF refining slag CaO (wt%) MgO (wt%) Before reduction After reduction 37 27 2.3 9

[0074] The Mg recovery was 65% and the Al recovery was 62% in the process of Comparative Example 2.

[0075] 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 person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples, without contradiction.

[0076] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary, and are not to be construed as limiting the present application, and the person skilled in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

Claims

1. A method for extracting Mg and Al with LF refining slag, characterized by, The method comprises the following steps: a. Pouring the LF refining slag after casting from a ladle into a slag tank, placing it in a vacuum chamber, adding a reducing agent to the LF refining slag to obtain a mixed reaction material, wherein the temperature of the LF refining slag is not lower than 1200℃; b. After vacuum extraction, the mixed reaction material in the slag tank is heated to react, and the generated gaseous Mg and Al are condensed and recovered at the cooling end outside the vacuum chamber.

2. The method for extracting Mg and Al with LF refining slag according to claim 1, characterized by, In the step a, the reducing agent is FeSi powder.

3. The method for extracting Mg and Al with LF refining slag according to claim 2, characterized by, The Si content in the FeSi powder is 72wt%-78wt%.

4. The method of extracting Mg and Al with LF refining slag according to claim 2 or 3, characterized by, In the step a, the adding amount of the FeSi powder is 20wt%-30wt% of the LF refining slag.

5. The method for extracting Mg and Al with LF refining slag according to claim 1, characterized by, In the step a, the reducing agent is added into the LF refining slag in batches.

6. The method for extracting Mg and Al with LF refining slag according to claim 1, characterized by, In the step b, the vacuum degree of the vacuum chamber is 5-20Pa.

7. The method of extracting Mg and Al with LF refining slag according to claim 1, characterized by, In the step b, the reaction temperature is 1300-1500℃.

8. The method of extracting Mg and Al with LF refining slag according to claim 1 or 7, characterized by, In the step b, the reaction time is 1-3 hours.

Images