Efficient resource utilization method for smelting slag calcium and magnesium leaching tailings

Abstract

The invention discloses an efficient resource utilization method for smelting slag calcium and magnesium leaching tailings, and belongs to the technical field of solid waste resource utilization. According to the method, the smelting slag calcium and magnesium leaching tailings are subjected to Raymond mill or jet mill treatment, the obtained material is separated through high-gradient magnetic separation, and iron-rich concentrate and silicon-rich tailings are obtained, the Raymond mill or jet mill is combined with the high-gradient magnetic separation technology, and efficient separation of silicon and iron in the smelting slag calcium and magnesium leaching tailings can be achieved; the magnetic separation iron ore concentrate is used for the steel production process, the silicon-containing component is used as a building material or used for preparing a mineral material, and the problem that resource utilization of the smelting slag carbon sequestration tailings is difficult is effectively solved.

Description

Technical Field

[0001] The present invention relates to a method for the efficient resource utilization of the tailings of calcium and magnesium leached from smelting slag, specifically to a method for the efficient separation and resource utilization of silicon and iron in the tailings after calcium and magnesium are leached from smelting slag, belonging to the technical field of solid waste resource utilization. Background Art

[0002] In the process of steel manufacturing, a large amount of smelting waste slag including blast furnace slag, steel slag and refining slag will be generated. Taking steel slag as an example, its output accounts for about 10-15% of the crude steel output. The large accumulation of steel slag not only occupies valuable land resources, but also leads to waste of resources and potential environmental pollution. Therefore, how to effectively utilize these steel slag resources has become an urgent problem to be solved. A large amount of carbon dioxide is emitted in the steel production process, and reducing carbon emissions is also a major challenge faced by the steel industry. The use of calcium and magnesium components in smelting slag to react with CO2 to achieve mineralization and capture of CO2 is a flue gas carbon capture technology with application prospects. The effective leaching of calcium and magnesium components in smelting slag is the key step to achieve CO2 mineralization. For example, hydrochloric acid, nitric acid, organic acids, ammonium salts, etc. are used to extract calcium and magnesium components in steel slag, and the calcium and magnesium leaching solution is used in the CO2 mineralization process. However, the tailings after calcium and magnesium are leached from smelting slag are mainly composed of iron and silicon, and the two are complexly disseminated. In the prior art, mainly flotation or magnetic separation is used to recover some iron-containing components or silicon-containing components, but there are still problems such as low recovery rate of valuable components and iron-silicon inclusion in the separation process, resulting in low degree of resource utilization of the tailings of calcium and magnesium leached from smelting slag, which restricts the popularization and application of the technology of mineralization and capture of CO2 from smelting slag to a certain extent. Summary of the Invention

[0003] Aiming at the problems that the iron-silicon component dissemination relationship in the tailings of calcium and magnesium leached from smelting slag is complex, and there are problems such as low recovery rate of valuable components and iron-silicon inclusion in the conventional separation process, which affect the subsequent use and make it difficult to resourcefully utilize the carbon-fixing tailings of smelting slag. The purpose of the present invention is to provide a method for the efficient resource utilization of the tailings of calcium and magnesium leached from smelting slag. Based on the chemical composition, occurrence state and dissemination relationship of iron and silicon in the tailings of calcium and magnesium leached from smelting slag, Raymond mill or jet mill treatment is used to achieve the efficient dissociation of iron-silicon components in the tailings, and then high-gradient magnetic separation is used to achieve the efficient separation of iron-silicon components. The separated magnetic component has a high iron content and can be reused as raw materials for sintering, pelletizing, etc. The non-magnetic component has a high silicon content and can be used as building materials, thus realizing the efficient separation and resource utilization of the tailings, promoting the development of the carbon-fixing process of smelting slag, and being of great significance to carbon emission reduction and resource recycling in the steel industry.

[0004] In order to achieve the above technical purpose, the present invention provides a method for the efficient resource utilization of the tailings of calcium and magnesium leached from smelting slag, which is to subject the tailings of calcium and magnesium leached from smelting slag to Raymond mill or jet mill treatment, and the obtained material is separated by high-gradient magnetic separation to obtain iron-rich concentrate and silicon-rich tailings.

[0005] The main components of smelting slag are oxides or silicates of Ca, Si, Fe, Mg, etc. Silicates, such as calcium silicate and calcium ferrite, are selectively leached out of calcium and magnesium through the leaching process. The main components of the leached tailings are Fe, Si, etc., and contain a certain amount of alloy components such as Cr and Mn. These components exist in the form of oxides, solid solutions or silicates, respectively. In terms of micromorphology, the crystals formed by these components are fine in size and wrap around each other. Therefore, it is difficult to achieve efficient separation of iron and silicon using conventional sorting processes, and the selected products are obviously impregnated. The conventional ball milling, rod milling and other processes in the prior art are fundamentally difficult to achieve the deep dissociation of silicon and iron in the smelting slag calcium and magnesium leaching tailings, mainly because the ball milling, rod milling and other processes mainly use the impact and extrusion of the grinding medium to achieve the purpose of particle crushing, but the iron component in the form of elemental iron or alloy in the smelting slag calcium and magnesium leaching tailings is extended under the impact and extrusion of the grinding medium, and at the same time, under the action of the friction generated by the inner wall lining surface of the cylinder, it is inevitable to curl, etc., thereby coating the fine-grained particles, resulting in the difficulty of fully dissociating ferrosilicon. The present invention adopts a grinding process such as Raymond mill or air flow mill, and the smelting slag calcium and magnesium leaching tailings are mainly subjected to the cutting force, so that its surface is refined. At the same time, the refined small particles are quickly dissociated from the parent particles under the action of centrifugal force and inertia, avoiding mutual adhesion between materials, thereby achieving full dissociation of ferrosilicon, and effectively avoiding the iron element and its alloy from encapsulating silicon minerals during the grinding process. In addition, the smelting slag calcium and magnesium leaching tailings form a porous structure during the leaching process of calcium and magnesium (specifically, Figure 1 As shown). Moreover, since the grinding methods such as Raymond mill or air flow mill will not cause serious damage to the pore structure of the tailings, it can maintain its original porous characteristics, avoid the components from covering each other, and the fine particles produced by the cutting action are quickly separated from the tailings, and can produce ultrafine powders with uniform particle size and fine particles, meeting the needs of high-efficiency and low-consumption ultrafine grinding of tailings.

[0006] As a preferred solution, the smelting slag calcium and magnesium leaching tailings are the residues after at least one of blast furnace slag, electric furnace steel slag, converter steel slag, and ladle refined slag has been acid-leached, alkaline-leached or water-leached to remove calcium and magnesium. Smelting slags such as blast furnace slag and electric furnace steel slag are used for carbon dioxide fixation after leaching calcium and magnesium, and the remaining residues are mainly silicon and iron components. Due to the presence of difficult-to-grind components in smelting slag, such as calcium silicate and calcium ferrite, if fine grinding is directly performed, high energy consumption will result, and large particles will still exist after fine grinding, and the particle size distribution range is wide. At the same time, the difficult-to-grind components will inevitably damage the mill and grinding media. After leaching calcium and magnesium from the smelting slag, not only can some difficult-to-grind minerals be leached, but also a large number of pores will be generated inside the particles, which is conducive to the crushing and refinement of particles in the subsequent fine grinding process, greatly improving the fine grinding efficiency while reducing damage to the equipment.

[0007] As a preferred solution, the TFe of the tailings from the calcium and magnesium leaching of smelting slag is ≥20%, the average particle size is ≤3 mm, and a large number of pores are generated inside the particles. The iron content and particle size of the tailings from the calcium and magnesium leaching of smelting slag have an important impact on the quality of magnetic separation products and the ultrafine grinding process. When the iron content is less than 20%, the main component in the leaching tailings is silicon-containing substances, which can be used as high-silicon mineral materials for cement admixtures, etc. And when the iron content is low, even if the tailings are subjected to ultrafine grinding and high-gradient magnetic separation, the total amount of recoverable iron-containing substances is limited, resulting in high energy consumption and poor economy in the whole process. Therefore, the suitable iron content of the carbon sequestration tailings of smelting slag should be ≥20%. The ultrafine grinding technology has high requirements for the particle size of the feed. When the particle size is coarser or the particle size distribution range is wider, it will lead to problems such as uneven discharge particle size and large equipment damage in the fine grinding process. Previous studies have found that when the particle size is ≤1 mm, the fine grinding effect is better. Therefore, the further preferred particle size of the tailings from the calcium and magnesium leaching of smelting slag is ≤1 mm.

[0008] As a preferred solution, the process parameters of the Raymond mill are as follows: the roller pressure is 8 - 12 MPa, the main shaft speed is 100 - 120 r / min, and the classification speed is 200 - 400 r / min. The working process of the Raymond mill mainly realizes the crushing of materials through the force between the grinding rollers and the grinding ring, and combines the classification system to control the fineness of the finished product. The roller pressure, the main shaft speed, the classifier speed, etc. are the key process parameters. Since the tailings have a relatively high hardness, a higher roller pressure is required to effectively crush the materials. The stronger the rolling pressure, the finer the finished product, but the energy consumption and the wear of the grinding rollers will increase. A higher main shaft speed can increase the output, but too high a speed will cause heat generation. Excessive heat will soften the metal and increase the ductility of the metal, which is disadvantageous. The higher the classifier speed, the finer the particle size of the finished product. Due to the relatively high hardness of the tailings and the relatively fine particle size of the required crushed powder, considering the dissociation effect and production cost comprehensively, the preferred roller pressure is 8 - 12 MPa, the main shaft speed is 100 - 120 r / min, and the classification speed is 200 - 400 r / min.

[0009] As a preferred solution, the process parameters of the jet mill are as follows: the air flow velocity is 300 - 500 m / s, the working pressure is 0.8 - 1.2 MPa, and the gas-solid volume ratio is 0.5 - 1.5. The working principle of the jet mill is to crush materials through air flow acceleration, particle collision and shearing. When using the jet mill to finely grind the tail slag, it is necessary to optimize the process parameters of the jet mill according to the physical properties of the tail slag (high hardness, high iron content, poor grindability) and the required fineness of the finished product. The jet mill realizes pulverization through high-speed air flow impact and particle collision, and has advantages such as no medium wear and narrow particle size distribution, but there is also the problem of high energy consumption. The steel slag has a high hardness and requires a higher speed impact to achieve effective pulverization. Similarly, the greater the pressure, the higher the kinetic energy, but too high an air flow pressure will lead to increased equipment loss and energy consumption. Too low a gas-solid ratio will result in insufficient particle collision, and too high a ratio will increase energy consumption. Therefore, the preferred process parameters of the jet mill are an air flow velocity of 300 - 500 m / s, a working pressure of 0.8 - 1.2 MPa, and a gas-solid ratio of 0.5 - 1.5.

[0010] As a preferred solution, the Raymond mill or jet mill is used to control the particle size of the material to be less than 125 μm. When the particle size of the material reaches below 125 μm, the silicon-iron components are fully dissociated, which is beneficial for subsequent magnetic separation. Conventional grinding technologies such as ball milling, rod milling, and roller milling can control the particle size of the calcium-magnesium leaching tail slag of the smelting slag to be <125 μm, but repeated grinding and screening are required to obtain the relevant products, resulting in low production process efficiency, high labor intensity, and based on these grinding methods mainly relying on impact and extrusion, even if the particle size of the calcium-magnesium leaching tail slag of the smelting slag is controlled within the range of <125 μm, the silicon-iron is difficult to be fully dissociated due to the encapsulation of iron and its alloys on the silicon minerals.

[0011] As a preferred solution, the magnetic field intensity of the high-gradient magnetic separation is 10000 - 16000 Gs. Since the iron in the carbon-fixing tail slag of the smelting slag mainly exists in the form of Fe2O3, compared with magnetite or elemental iron, its magnetism is weaker. Using high-gradient magnetic separation not only has the advantages of stable magnetic field and strong suction, can efficiently realize the separation and recovery of iron resources, high working efficiency, and convenient use. At the same time, the materials do not agglomerate and there is no blockage phenomenon, greatly improving the processing capacity. The magnetic field intensity is the key factor for separation. A large number of studies have found that when the magnetic field intensity is less than 10000 Gs, the iron content in the silicon-rich phase is high, and the recovery efficiency of iron resources is affected. Although a magnetic field intensity higher than 16000 Gs is helpful for the recovery of iron resources, it will cause some silicon-containing substances to be entrained in the recovered iron resources, reducing the iron grade. Therefore, the preferred magnetic field intensity is 10000 - 16000 Gs.

[0012] The grade of the magnetically separated iron concentrate obtained by the present invention is greater than 36%. The magnetic separation process includes at least one of dry weak magnetic separation, dry strong magnetic separation, wet weak magnetic separation, and wet strong magnetic separation. If the magnetic field strength used is low, some iron-containing particles will be difficult to be effectively recovered and enter the magnetic separation tailings, affecting the recovery rate of iron. The magnetic field strength will increase the energy consumption of the whole process.

[0013] The magnetically separated iron concentrate obtained by the present invention can be used as raw materials for sintering and pelletizing, and realize the internal circulation of steel enterprises. The non-magnetic material is silicon-rich tailings, which has fine particle size and can be used as additives for high-activity building materials.

[0014] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0015] 1) The method for efficient resource utilization of smelting slag calcium and magnesium leaching tailings of the present invention is based on the characteristics of the smelting slag carbon fixation process and the current situation of difficulty in resource utilization of carbon fixation tailings, develops a technology for efficient separation and reuse of valuable components in tailings, realizes the resource utilization of tailings, solves the blockages and bottlenecks of the smelting slag carbon fixation process, promotes the development of smelting slag carbon fixation technology, and promotes carbon emission reduction and resource recycling in the steel industry.

[0016] 2) The method for efficient resource utilization of smelting slag calcium and magnesium leaching tailings of the present invention is based on the basic physical and chemical properties of smelting slag calcium and magnesium leaching tailings and the principle of mineral processing engineering. The conventional grinding method cannot achieve ferrosilicon separation at all. The present invention is based on the special method of crushing minerals by Raymond mill or air flow mill, which can avoid the wrapping effect of iron and ferroalloy on silicon during the grinding process, achieve efficient fine grinding of tailings, and thus achieve full dissociation of iron and silicon components. Then, by utilizing the difference in magnetic properties between iron-containing components and silicon-containing components, high-gradient magnetic separation is adopted, which has the advantages of low consumption and high efficiency, and realizes resource utilization of tailings.

[0017] 3) The present invention is mainly based on the previous research results (CN118996129A, CN118745520A), on which basis the valuable components in the tailings are further dissociated and recovered in a targeted manner, and together with the previous technologies, a smelting slag carbon fixation and resource utilization technology system is constructed.

[0018] 4) The present invention adopts a dry process to achieve the dissociation and recovery of valuable components, which has the advantages of short process flow and low pollution, and has the potential for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The microstructure of smelting slag carbon-fixed tailings. DETAILED DESCRIPTION

[0020] In order to facilitate the understanding of the present invention, the present invention will be described in more comprehensive and detailed manner in conjunction with preferred embodiments below, but the protection scope of the present invention is not limited to the following specific embodiments.

[0021] Unless otherwise defined, all technical terms used hereinafter have the same meanings as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of the present invention.

[0022] Unless otherwise specified, the smelting slag carbon sequestration tail slag used in the present invention is the waste after carbon sequestration of converter slag from iron and steel enterprises, and its chemical composition is shown in Table 1.

[0023]

[0024] Example 1

[0025] The tail slag was processed by a Raymond mill with a roller pressure of 8 MPa, a main shaft speed of 120 r / min, and a classification speed of 400 r / min. The tail slag was refined to a particle size < 125 μm. High-gradient magnetic separation was used with a magnetic field intensity of 12000 Gs. The iron content of the obtained magnetic substance measured by chemical titration was 47.6%, and the iron content in the magnetic separation tail slag was 7.23%.

[0026] Example 2

[0027] The tail slag was processed by a jet mill with an air flow speed of 500 m / s, a working pressure of 1.0 MPa, and a gas-solid volume ratio of 0.5. The tail slag was refined to a particle size < 75 μm. High-gradient magnetic separation was used with a magnetic field intensity of 10000 Gs. The iron content of the obtained magnetic substance measured by chemical titration was 46.1%, and the iron content in the magnetic separation tail slag was 8.09%.

[0028] Example 3

[0029] The tail slag was processed by a jet mill with an air flow speed of 400 m / s, a working pressure of 0.9 MPa, and a gas-solid volume ratio of 1.0. The tail slag was refined to a particle size < 90 μm. High-gradient magnetic separation was used with a magnetic field intensity of 16000 Gs. The iron content of the obtained magnetic substance measured by chemical titration was 50.3%, and the iron content in the magnetic separation tail slag was 6.62%.

[0030] Example 4

[0031] The tail slag was processed by a jet mill with an air flow speed of 300 m / s, a working pressure of 0.8 MPa, and a gas-solid volume ratio of 1.5. The tail slag was refined to a particle size < 106 μm. High-gradient magnetic separation was used with a magnetic field intensity of 15000 Gs. The iron content of the obtained magnetic substance measured by chemical titration was 51.1%, and the iron content in the magnetic separation tail slag was 6.03%.

[0032] Comparative Example 1

[0033] Compared with Example 1, the only difference is that the tailings are refined to a particle size ranging from 0 to 250 μm, and the content of particles with a size of 125 - 250 μm accounts for 16%. The iron content of the obtained magnetic substance measured by chemical titration is 34.7%, and the iron content in the magnetic separation tailings is 29.41%.

[0034] Comparative Example 2

[0035] Compared with Example 2, the only difference is that the magnetic field intensity is 5000 Gs. The iron content of the obtained magnetic substance measured by chemical titration is 28.4%, and the iron content in the magnetic separation tailings is 8.23%.

[0036] Comparative Example 3

[0037] Compared with Example 1, the only difference is that a rod mill is used to finely grind the tailings. The rod diameter is 50 - 100 mm, the filling rate is 35%, and the rotational speed is 60% of the critical speed. The iron content of the obtained magnetic substance measured by chemical titration is 34.1%, and the iron content in the magnetic separation tailings is 12.79%. It shows that it is difficult to achieve iron-silicon separation by conventional rod milling methods.

[0038] Comparative Example 4

[0039] Compared with Example 1, the only difference is that a ball mill is used to finely grind the tailings. Zirconia grinding balls are used, the ball-to-material ratio is 1:20, and the ball mill rotational speed is 200 rmp. The tailings are refined to a particle size < 125 μm. The iron content of the obtained magnetic substance measured by chemical titration is 32.3%, and the iron content in the magnetic separation tailings is 13.64%. It shows that it is difficult to achieve iron-silicon separation by conventional ball milling methods.

Claims

1. A method for efficient resource utilization of smelting slag calcium and magnesium leaching tailings, characterized by: The calcium and magnesium leaching tailings from the smelting slag are processed by Raymond mill or air flow mill, and the resulting materials are separated by high gradient magnetic separation to obtain iron-rich concentrate and silicon-rich tailings.

2. The method for efficient resource utilization of smelting slag calcium and magnesium leaching tailings according to claim 1, characterized in that: The smelting slag calcium and magnesium leaching tailings are the residues after at least one of blast furnace slag, electric furnace slag, converter slag and ladle refining slag has been subjected to acid leaching, alkali leaching or water leaching to remove calcium and magnesium.

3. A method for efficient resource utilization of smelting slag calcium and magnesium leaching tailings according to claim 1 or 2, characterized in that: The TFe of the smelting slag calcium and magnesium leaching tailings is ≥20%, the average particle size of the particles is ≤3mm, and a large number of pores are generated inside the particles.

4. The method for efficient resource utilization of smelting slag calcium and magnesium leaching tailings according to claim 1, characterized in that: The process parameters of the Raymond mill are: grinding roller pressure of 8-12 MPa, spindle speed of 100-120 r / min, and classification speed of 200-400 r / min.

5. The method for efficient resource utilization of smelting slag calcium and magnesium leaching tailings according to claim 1, characterized in that: The process parameters of the jet mill are: air flow velocity of 300-500 m / s, working pressure of 0.8-1.2 MPa, and gas-solid volume ratio of 0.5-1.

5.

6. A method for efficient resource utilization of smelting slag calcium and magnesium leaching tailings according to claim 1, 4 or 5, characterized in that: The Raymond mill or air flow mill is used to control the particle size of the material to be less than 125 μm.

7. The method for efficient resource utilization of smelting slag calcium and magnesium leaching tailings according to claim 1, characterized in that: The magnetic field strength of the high gradient magnetic separation is 10000~16000Gs.

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