CN116536518A - Method for extracting Mg and Al by using LF refining slag - Google Patents

Abstract

The invention discloses a method for extracting Mg and Al by utilizing LF refining slag, which comprises the following steps: a. pouring the poured LF refining slag from a ladle into a slag tank, placing the ladle into a vacuum chamber, adding a reducing agent into the LF refining slag, and mixing to obtain a mixed reaction material; b. and after vacuum extraction, heating the mixed reaction materials in the slag pot, reacting, and respectively condensing and recovering the generated gaseous Mg and Al at the cooling end outside the vacuum chamber to obtain solid Mg and Al. According to the method, LF refining slag is used as a raw material, and the rest heat is effectively utilized to produce high added value Mg and Al, so that the problem of green treatment of the LF refining slag is solved, the defect of producing Mg by a traditional thermal reduction method is avoided, the recovered Mg and Al can be reused in steelmaking production, and the problem of large-scale utilization of the LF refining slag is solved while higher economic benefit is obtained.

Description

A kind of method utilizing LF refining slag to extract Mg and Al

technical field

The invention belongs to the technical field of steelmaking slag utilization, and in particular relates to a method for extracting Mg and Al by using LF refining slag.

Background technique

The ladle top slag after LF refining has the characteristics of high alkalinity, good metallurgical properties, reasonable composition, and fast slag melting. Except for some heat slags with high sulfur content, most of the heat slags are unsaturated with sulfur and can be recycled Go back to the refining process for secondary or even tertiary utilization.

At present, scholars at home and abroad have done a lot of research on the recycling process of LF refining slag, but no iron and steel enterprise can fully recycle LF refining slag. The current recycling rate is less than 20%, and the LF slag that cannot be recycled can only be poured into slag. The tank is then transported to the slag yard, and finally processed together with converter slag or electric furnace slag. Because steel slag contains P, the ore blending is limited, and basically cannot be used for sintering. Only after metal Fe is recovered, the powder and slag can be piled up, occupying and polluting the land. A large amount of steel slag is discarded or used as raw material to produce low value-added products such as cement. Due to the serious dust and pulverization in stacking, it is not conducive to environmental protection and causes waste of resources. It has brought serious troubles to the social environment, and has also become a major obstacle to social progress and economic development.

Therefore, it is necessary to provide a high-value-added energy-saving and emission-reduction method for recycling LF refining slag, so as to solve the shortcomings of low reuse rate of LF refining slag, easy to raise dust when stacked, great environmental pollution, and low value-added utilization, so as to achieve high added value Recycling and utilization of LF refining slag finally achieves the purpose of circular production and zero emission.

Contents of the invention

The present invention is made based on the inventor's discovery and understanding of the following facts and problems: in the related art, there are some defects in the research method of recycling LF refining slag, mainly manifested in: (1) refining hot slag recycling process, many iron and steel Enterprises have implemented the heat recovery test of the remaining steel slag after refining, but limited by the conditions of the plant, lifting equipment, product outline and production organization, the hot slag circulation ratio is low; (2) Refined slag is cooled and crushed for solid reuse , its heat cannot be fully utilized, and the slag formation speed of the next cycle using cold slag material is slow, which is not conducive to energy saving and consumption reduction; (3) the desulfurization technology of LF refining slag thermal oxidation is difficult to realize due to the limitation of production space, It is difficult to guarantee the high-temperature gas at a temperature of 1300-1450°C; (4) The solid-state hydrothermal leaching method for desulfurization wastes a lot of cooling water and steel slag heat during the treatment process, and also causes secondary pollution.

Industrial magnesium smelting methods mainly include electrolysis, carbothermal reduction, Pidgeon method, and Magnetherm semi-continuous magnesium smelting process. Among them, the carbothermal magnesium smelting process was only used in factories in the 1930s and 1940s. At present, the mainstream industrial methods in the world are only Electrolysis and Pidgeon. Before the mid-1990s, electrolytic production accounted for more than 80% of global magnesium production, while Pidgeon and Magnetherm production only 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. Only the Pidgeon method accounts for more than 80% of the world's output.

The thermal reduction method is one of the methods for producing metal Mg. It mainly uses dolomite and magnesite as raw materials, burns MgO in the middle of the kiln, and then adds a reducing agent to heat and reduce it to metal magnesium in the reduction furnace. The Pidgeon process is commonly used at home and abroad to smelt magnesium, that is, calcined dolomite (MgO, Cao) is used as raw material, ferrosilicon is used as reducing agent, mixed and ground into fine powder according to a certain proportion, pressed into agglomerates, and put into a reduction tank , heated and reduced in the reduction furnace to obtain magnesium vapor, condensed and crystallized solid magnesium, and then melted into magnesium ingots. The advantage of this method is that it is simple, but the disadvantage is that the raw materials are heated after being mixed from the cold state, and the production process consumes a lot of energy. Calcination of dolomite and thermal reduction of magnesium smelting are both carried out at high temperature, which takes a long time and consumes a lot of fuel, and the two processes are carried out separately, which increases the fuel consumption and processing cost of the production process.

Regardless of the Pidgeon method or the Magnetherm semi-continuous smelting process in France, ferrosilicon, especially ferrosilicon containing more than 75% silicon (usually 75 ^# ferrosilicon) is used as the reducing agent, and the ore containing MgO is used as the magnesium smelting process. The raw materials are then ground, mixed and pressed into balls with the mineralizer (CaF ₂ ) according to the proportion, and then the balls are put into the reduction tank, and the tank undergoes high temperature and high vacuum (1200°C, 13Pa) to react to form Mg vapor. The Mg vapor is then crystallized to form metal Mg, and the function of the mineralizer (CaF ₂ ) is to reduce the temperature at which the liquid phase appears to accelerate the reaction speed.

Under high temperature and vacuum conditions, the chemical reaction of Si reducing MgO is shown in formula (1).

2MgO+Si＝SiO ₂ +2Mg(gas)(1)

Disadvantages of traditional thermal reduction method to produce Mg: 1) The production uses dolomite and magnesite as raw materials, and the mining process destroys the natural ecological environment; 2) Dolomite, magnesite and other raw materials need to be fired into MgO in the middle of the kiln, and It is carried out at high temperature, the duration is long, and it needs to consume a lot of fuel. The fuel consumption and processing cost in the production process are large; 3) The production process of thermal reduction magnesium smelting needs to mix the raw materials from room temperature and then heat them to the high temperature required for the reaction. 1250°C, long duration, also consumes a lot of fuel, and is carried out separately from the 1) process, which increases the fuel consumption and processing cost of the production process; 4) Pidgeon method uses external heating, and the heat is gradually conducted from the outside of the reactor to Internally, the production cycle is long, the heat loss is large, and the heat energy utilization rate is low. According to the analysis, the heat energy utilization rate of the typical process is only about 20%; 5) The smoke pollution in the production process is serious, the working environment is bad, and the surrounding ecological environment is deteriorated; 6) Production needs to add CaF ₂ , causing pollution to the environment.

Aluminum and aluminum alloys are currently one of the most economically applicable materials that are widely used. Because of its high activity, aluminum can only be produced on a large scale by electrolysis at present. However, the process of electrolytic aluminum requires high energy consumption and high cost, so researchers have been looking for various ways to economically produce aluminum.

The present invention aims to solve one of the technical problems in the related art at least to a certain extent. For this reason, the embodiments of the present invention propose a method for extracting Mg and Al by using LF refining slag, using LF refining slag as raw material, and effectively utilizing the remaining heat to produce high value-added Mg and Al, which not only solves the problem of LF refining steel slag Green treatment of problems, and avoid the shortcomings of the traditional thermal reduction method to produce Mg, the recovered Mg and Al can be re-used in steelmaking production, while obtaining high economic benefits, it solved the problem of large-scale utilization of LF refined steel slag.

The method for extracting Mg and Al using LF refining slag in the embodiment of the present invention comprises the following steps:

a. Pour the poured LF refining slag from a ladle into a slag tank, place it in a vacuum chamber, add a reducing agent to the LF refining slag and mix to obtain a mixed reaction material;

b. After the vacuum is drawn, the mixed reaction materials in the slag tank are heated to react, and the gaseous Mg and Al produced are condensed and recovered at the cooling end outside the vacuum chamber respectively.

Advantages and technical effects brought by the method of using LF refining slag to extract Mg and Al in the embodiment of the present invention, 1. In the method of the embodiment of the present invention, the LF refining slag after casting is used as raw material, the cost is low, almost zero, and The residual temperature of LF refining slag is high, and the steel slag contains a large amount of sensible heat. The LF refining slag is used to preheat the reducing agent and provide part of the energy required for the reaction of MgO and Al ₂ O ₃ in the slag. After adding some additional heat, it can Reduction reaction needs are satisfied, heat is fully and effectively utilized, and a large amount of energy is saved; 2, in the method of the embodiment of the present invention, the LF refining slag after casting is used as raw material to extract Mg and Al, and the LF refining slag is industrial solid waste. Use it to replace industrial raw materials dolomite, magnesite and aluminum ore, realize waste utilization, save non-renewable ore resources; 3, the method of the embodiment of the present invention effectively solves the problem of recycling and reusing LF refining steel slag, realizes It not only achieves green treatment, but also avoids the technical defects of traditional production of Mg and Al. The recovered Mg and Al can be re-used in steelmaking production, achieving high economic benefits. 4. The method of the embodiment of the present invention has simple process, low cost, energy saving and environmental protection, easy large-scale industrial application, and has broad prospects.

In some embodiments, in the step a, the temperature of the LF refining slag is not lower than 1200°C.

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

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

In some embodiments, in the step a, the FeSi powder is added in an amount of 20wt%-30wt% of the LF refining slag.

In some embodiments, in the step a, the reducing agent is added to the LF refining slag in batches.

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

In some embodiments, in the step b, the reaction temperature is 1300-1500°C.

In some embodiments, in the step b, the reaction time is 1-3 hours.

Description of drawings

Fig. 1 is a process flow chart of extracting Mg and Al from LF refining slag according to an embodiment of the present invention.

Detailed ways

Embodiments of the present invention are described in detail below, and the embodiments are exemplary and intended to explain the present invention, but should not be construed as limiting the present invention.

As shown in Figure 1, the method of utilizing LF refining slag to extract Mg and Al in the embodiment of the present invention comprises the following steps:

a. Pour the poured LF refining slag from a ladle into a slag tank, place it in a vacuum chamber, add a reducing agent to the LF refining slag and mix to obtain a mixed reaction material;

b. After the vacuum is drawn, the mixed reaction materials in the slag tank are heated to react, and the gaseous Mg and Al produced are condensed and recovered at the cooling end outside the vacuum chamber respectively.

In the method for extracting Mg and Al using LF refining slag in the embodiment of the present invention, the LF refining slag after pouring is used as raw material, the cost is low, almost zero, and the residual temperature of LF refining slag is high, and the steel slag contains a large amount of sensible heat. The LF refining slag preheats the reducing agent and provides part of the energy required for the reaction of MgO and Al ₂ O ₃ in the slag. After adding an additional part of the heat, the reduction reaction needs can be met. The heat has been fully and effectively used, saving a lot of energy. Energy: In the method of the embodiment of the present invention, 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 it is used to replace industrial raw materials dolomite, magnesite and aluminum ore, thereby realizing waste Utilization saves non-renewable ore resources; the method of the embodiment of the invention effectively solves the problem of recycling and reusing LF refining steel slag, realizes green treatment, and avoids the technical defects of traditional production of Mg and Al. Mg and Al can be re-applied to steelmaking production, which has achieved higher economic benefits, and at the same time provides a new direction for large-scale utilization of LF refining steel slag; the method of the embodiment of the invention has simple process, low cost, energy saving and environmental protection, and is easy to use. Large-scale industrial applications have broad prospects.

In some embodiments, in the step a, the temperature of the LF refining slag is not lower than 1200°C. In the method of the embodiment of the present invention, the temperature of the LF refining slag after pouring basically reaches above 1200°C, which contains a large amount of sensible heat. The waste heat of the LF refining slag can be used to preheat the reducing agent, and it can also be MgO, Al ₂ O The ₃ reaction provides most of the energy needed, so that the heat of LF refining slag is fully utilized, saving a lot of energy, energy saving and environmental protection.

In some embodiments, in the step a, the reducing agent is FeSi powder, preferably, the Si content in the FeSi powder is 72wt%-78wt%. Further preferably, the FeSi powder is added in an amount of 20wt%-30wt% of the LF refining slag. Preferably, the reducing agent is added to the LF refining slag in batches. In the method of the embodiment of the present invention, the dosage of the reducing agent is optimized, which can further increase the heat utilization rate of the LF refining slag, and improve the extraction recovery rate of Mg and Al.

In some embodiments, in the step b, the vacuum degree of the vacuum chamber is 5-20 Pa, the reaction temperature is 1300-1500° C., and the reaction time is 1-3 hours. In the method of the embodiment of the present invention, the LF refining slag and the reducing agent are reacted in a vacuum environment, which can realize the full utilization of the waste heat of the LF refining slag, and only need to add some additional heat to achieve all the energy required for the reduction reaction. The LF refining slag was used as raw material to extract Mg and Al.

The present invention will be described in detail below in conjunction with the examples.

For 260t LF in a steel plant, the amount of LF refining slag is 3t/furnace, and the temperature of LF refining slag in the ladle returned after pouring is 1200-1250℃.

Example 1

(1) Reductant batching: add FeSi powder with Si content of 75wt%, the amount of FeSi powder is proportioned according to 20wt% of the LF refining slag amount, and the addition is 600kg;

(2) Pour the poured LF refining slag from the ladle into the slag pot and transport it to the vacuum chamber. The slag tank is used as the reaction vessel, and the temperature of the LF refining slag is 1220°C. The prepared FeSi powder is added to the LF refining slag in batches, and then mixed evenly.

(3) The system is evacuated to a degree of vacuum of 19 Pa (absolute pressure), and the reaction raw materials in the slag tank are heated to 1500° C. in the vacuum chamber and kept for 1 hour. Under the suction of the vacuum system, the gaseous Mg and Al produced by the reaction are condensed into solid Mg and Al respectively at the cooling end outside the vacuum chamber for recovery.

The main components of the LF refining slag before and after the reaction in this example are shown in Table 1. It can be seen from Table 1 that the Mg and Al in the LF refining slag are effectively extracted and recovered after the reaction, and the MgO content in the LF refining slag is as low as 2.3% _{. O3} drops to 6.2%.

Table 1

LF refining slag CaO(wt%) SiO ₂ (wt%) MgO(wt%) Al ₂ O ₃ (wt%) Before restore 49 11 9 27 After restoration 42 32 2.3 6.2

It is calculated that in the method of this embodiment, the recovery rate of Mg is 73%, and the recovery rate of Al is 76%.

Example 2

(1) Reductant batching: adding FeSi powder with a Si content of 78wt%, the amount of FeSi powder is proportioned according to 25wt% of the LF refining slag amount, and the addition is 750kg;

(2) Pour the poured LF refining slag from the ladle into the slag pot and transport it to the vacuum chamber. The slag tank is used as the reaction vessel, and the temperature of the LF refining slag is 1210°C. The prepared FeSi powder is added to the LF refining slag in batches, and then mixed evenly.

(3) The system is evacuated to a vacuum degree of 15 Pa, and the reaction raw materials in the slag tank are heated to 1400° C. in the vacuum chamber and kept for 2 hours. Under the suction of the vacuum system, the gaseous magnesium and aluminum produced by the reaction are condensed into solid Mg and Al respectively at the cooling end outside the vacuum chamber for recovery.

The main components of the LF refining slag before and after the reaction in this embodiment are shown in Table 2. It can be seen from Table 2 that the Mg and Al in the LF refining slag are effectively extracted and recovered after the reaction, and the MgO content in the LF refining slag is as low as ₂ %. _O3 down to 8%.

Table 2

LF refining slag CaO(wt%) SiO ₂ (wt%) MgO(wt%) Al ₂ O ₃ (wt%) Before restore 48 10 7 29 After restoration 41 37 2 8

It is calculated that in the method of this embodiment, the recovery rate of Mg is 68%, and the recovery rate of Al is 69%.

Example 3

(1) Reductant batching: adding FeSi powder with a Si content of 72wt%, the amount of FeSi powder is proportioned according to 30wt% of the LF refining slag amount, and the addition amount is 900kg;

(2) The poured LF refining slag is poured into the slag tank from the ladle and transported to the vacuum chamber. The slag tank is used as the reaction vessel, and the temperature of the LF refining slag is 1210°C. The prepared FeSi powder is added to the LF refining slag in batches, and then mixed evenly.

(3) The system is evacuated to a vacuum degree of 6 Pa, and the reaction raw materials in the slag tank are heated to 1301° C. in the vacuum chamber and kept for 3 hours. Under the suction of the vacuum system, the gaseous magnesium and aluminum produced by the reaction are condensed into solid Mg and Al respectively at the cooling end outside the vacuum chamber for recovery.

The main components of the LF refining slag before and after the reaction in this example are shown in Table 3. As can be seen from Table 3, Mg and Al in the LF refining slag are effectively extracted and recovered after the reaction, and the MgO content in the LF refining slag is as low as 1.5% _{. O3} down to 7%.

table 3

LF refining slag CaO(wt%) SiO ₂ (wt%) MgO(wt%) Al ₂ O ₃ (wt%) Before restore 46 11 8 30 After restoration 37 32 1.5 7

It is calculated that in the method of this embodiment, the Mg recovery rate is 78%, and the Al recovery rate is 73%.

Comparative example 1

(1) Reductant batching: adding FeSi powder with a Si content of 75wt%, the amount of FeSi powder is proportioned according to 5wt% of the LF refining slag amount, and the addition amount is 150kg;

(2) The poured LF refining slag is poured into the slag tank from the ladle and transported to the vacuum chamber. The slag tank is used as the reaction vessel, and the temperature of the LF refining slag is 1210°C. The prepared FeSi powder is added to the LF refining slag in batches, and then mixed evenly.

(3) The system is evacuated to a vacuum degree of 19 Pa. In the vacuum chamber, the reaction raw materials in the slag tank are heated to 1500° C. and kept for 1 hour. Under the suction of the vacuum system, the gaseous magnesium and aluminum produced by the reaction are condensed into solid Mg and Al respectively at the cooling end outside the vacuum chamber for recovery.

The main components of the LF refining slag before and after the reaction in this example are shown in Table 4. It can be seen from Table 4 that the Mg and Al in the LF refining slag are effectively extracted and recovered after the reaction, and the MgO content in the LF refining slag is as low as 6.7% _{. O3} drops to 21%.

Table 4

LF refining slag CaO(wt%) SiO ₂ (wt%) MgO(wt%) Al ₂ O ₃ (wt%) Before restore 49 11 9 27 After restoration 49 18 6.7 twenty one

After calculation, in the method of Comparative Example 1, the Mg recovery rate is 25%, and the Al recovery rate is 23%.

Comparative example 2

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

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

table 5

LF refining slag CaO(wt%) SiO ₂ (wt%) MgO(wt%) Al ₂ O ₃ (wt%) Before restore 46 11 8 30 After restoration 37 27 2.3 9

After calculation, in the method of Comparative Example 2, the Mg recovery rate is 65%, and the Al recovery rate is 62%.

As used herein, the terms "one embodiment," "some embodiments," "example," "specific examples," or "some examples" mean specific features, structures, materials, or features described in connection with the embodiment or example. A feature is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the described specific features, structures, materials or characteristics may be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples and features of different embodiments or examples described in this specification without conflicting with each other.

Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention, those skilled in the art can make the above-mentioned The embodiments are subject to changes, modifications, substitutions and variations.

Claims (9)

1. A method for extracting Mg and Al by using LF refining slag, which is characterized by comprising the following steps:

a. pouring the poured LF refining slag from a ladle into a slag tank, placing the ladle into a vacuum chamber, adding a reducing agent into the LF refining slag, and mixing to obtain a mixed reaction material;

b. and after vacuum extraction, heating the mixed reaction materials in the slag pot, reacting, and respectively condensing and recycling the generated gaseous Mg and Al at the cooling end outside the vacuum chamber.

2. The method for extracting Mg and Al using LF refining slag as defined in claim 1, wherein in the step a, the temperature of the LF refining slag is not lower than 1200 ℃.

3. The method for extracting Mg and Al using LF refining slag as defined in claim 1, wherein in step a, the reducing agent is FeSi powder.

4. The method for extracting Mg and Al using LF refining slag as claimed in claim 3, wherein the Si content in the FeSi powder is 72wt% to 78wt%.

5. The method for extracting Mg and Al using LF refining slag as defined in claim 3 or 4, wherein in said step a, the amount of FeSi powder added is 20wt% to 30wt% of the LF refining slag.

6. The method for extracting Mg and Al using LF refinery slag according to claim 1, wherein in said step a, said reducing agent is added to LF refinery slag in batches.

7. The method for extracting Mg and Al using LF refining slag as defined in claim 1, wherein in the step b, the vacuum degree of the vacuum chamber is 5 to 20Pa.

8. The method for extracting Mg and Al using LF refining slag as defined in claim 1, wherein in said step b, said reaction temperature is 1300-1500 ℃.

9. The method for extracting Mg and Al using LF refining slag as defined in claim 1 or 8, wherein in said step b, said reaction time is 1 to 3 hours.