Method for extracting calcium and silicon from magnesium smelting waste residues

Abstract

The invention discloses a method for extracting calcium and silicon by using magnesium smelting waste residues, and relates to a magnesium smelting waste utilization method, which comprises the following steps: sieving the magnesium smelting waste residues to obtain fine powder; adding the calcium extraction agent solution and the magnesium smelting waste residue powder into a reaction container to enable the magnesium smelting waste residue powder to fully react with the calcium extraction agent solution; monitoring the calcium extraction rate of the reaction system; and carrying out acid treatment on the silicon-containing leaching residues to obtain silicon dioxide. According to the method, more than 90% of calcium components and more than 95% of silicon components in the Pidgeon process magnesium smelting waste residues containing dicalcium silicate, magnesium oxide, calcium ferrite and ferroferric oxide are separated and extracted, the calcium components are used for preparing calcium carbonate and other products, the silicon components are mainly produced in the form of silicon dioxide, and the purity of the silicon dioxide can reach more than 95%. High-value utilization of the magnesium smelting waste residues is realized, and new reference guidance is provided for cyclic utilization of solid waste resources and sustainable development of the magnesium smelting industry.

Description

Technical Field

[0001] The invention relates to a method for extracting magnesium smelting waste slag, in particular to a method for extracting calcium and silicon by utilizing magnesium smelting waste slag. Background Art

[0002] Magnesium is an important metal resource and an excellent raw material for the production of high-end equipment and new materials. my country is the world's largest producer and exporter of magnesium metal. The main magnesium smelting processes are ferrosilicon reduction and electrolysis, of which the ferrosilicon reduction is also known as the "Pijeng process". The "Pijeng process" has low cost, high magnesium purity and simple process. It has become the main smelting method used by magnesium smelting companies in my country. However, a large amount of magnesium smelting waste slag is generated in the process of producing magnesium metal. These waste slags are solid wastes with very low value, which will cause problems such as occupying land resources, dust pollution, alkalinizing soil and polluting groundwater.

[0003] At present, the application research of magnesium smelting waste slag mainly involves the fields of cementitious materials, refractory materials, desulfurizers, fertilizers, etc. However, a large amount of magnesium smelting waste slag can only be disposed of by landfill and cannot be effectively treated. Therefore, it is urgent to carry out research on the high-value recycling of magnesium smelting waste slag, which is also one of the hot topics in the current research field. Summary of the invention

[0004] The purpose of the present invention is to provide a method for extracting calcium and silicon from magnesium smelting waste slag. The method uses a calcium extracting agent to effectively extract the calcium component in the magnesium smelting waste slag, realizes efficient separation of the calcium and silicon components, and lays a foundation for further production of calcium and silicon chemical products with high added value. It not only effectively solves the problem of a large amount of magnesium smelting waste slag occupying land and causing environmental pollution, but also realizes the high-value utilization of magnesium smelting waste slag, turning waste into treasure.

[0005] The technical solution adopted by the present invention is: A method for extracting calcium and silicon components from magnesium smelting waste slag using the "Pidgeon process" includes the following steps: a. The magnesium smelting waste slag is sieved to obtain a fine magnesium smelting waste slag powder, and then a certain amount of calcium extracting agent solution is added to the reactor in a certain proportion, and the reactor is connected to the exhaust gas recycling device; b. The magnesium smelting waste slag powder reacts with the calcium extracting agent solution at a certain temperature. After the reaction is completed, the suspension is filtered to obtain a calcium salt solution and silicon-containing leaching slag; c. Silicon-containing leaching is carried out by treating with an acid solution of a certain concentration at a certain temperature, and then filtering to obtain silicon dioxide.

[0006] The main components of the magnesium smelting waste slag in step a above include dicalcium silicate, magnesium oxide, and iron compounds, with mass fractions of 70%-80%, 1%-5%, and 10%-15%, respectively, wherein the iron compounds mainly include calcium ferrite and ferroferric oxide. But not limited thereto; The magnesium smelting waste slag powder described in step a has a particle size of 100-300 mesh; The calcium extracting agent in step a is ammonium acetate, glycine, or a mixture of the two; The concentration of the calcium extracting agent solution in step a is 80-400 g·L -1 ; The liquid-to-solid ratio between the volume of the calcium extracting agent solution and the mass of the magnesium smelting waste slag powder described in step a above is 60:1-200:1; The reaction temperature in step b is 40-100°C; The acid solution used in the above step c is an aqueous solution of hydrogen chloride; The proton concentration of the acid solution used in step c is 1.4-8.0 mol·L -1 ; The liquid-to-solid ratio between the volume of the acid solution and the mass of the leached residue in step c is 10:1-40:1; The reaction temperature in the above step c is 20-60°C.

[0007] Advantages and effects of the present invention: 1. The present invention utilizes magnesium smelting waste slag to extract calcium and silicon components, with mild reaction conditions, simple process, and easy industrialization.

[0008] 2. The calcium extracting agent used in the present invention has a significantly higher calcium extraction efficiency than the traditional calcium extracting agent for the "Pijeng process" magnesium smelting waste slag containing dicalcium silicate, magnesium oxide, and iron compounds, and can extract more than 90% of the calcium resources in the form of calcium salts, thereby achieving effective separation of calcium and silicon components. The calcium salt solution obtained by the inventive process can be used as a high-quality raw material for further preparing high-value-added products such as calcium carbonate. The leached slag can be properly treated to obtain a high-purity silicon dioxide product.

[0009] 3. The tail gas and calcium extracting agent in the filtrate produced by the present invention can be regenerated and recycled through reaction, which is in line with the concept of green chemistry.

[0010] 4. The present invention provides a resource utilization approach for waste slag from magnesium smelting using the "Pidgeon process", which can effectively reduce resource waste and alleviate environmental pollution, thereby creating economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a flow chart of the present invention; Figure 2The XRD diagram of the sieved magnesium slag of the present invention; Figure 3 A comparison chart of the calcium extraction rate of ammonium acetate used in the present invention and ammonium chloride used as a traditional calcium extraction agent for magnesium smelting waste slag at 45°C as a function of liquid-to-solid ratio; Figure 4 This is the XRD diagram of the silicon dioxide product of the present invention. DETAILED DESCRIPTION

[0012] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0013] It should be noted that in the following embodiments, the main components of the magnesium smelting waste slag used include dicalcium silicate, magnesium oxide, and iron compounds, with mass fractions of 70%-80%, 1%-5%, and 10%-15%, respectively, wherein the iron compounds mainly include calcium ferrite and ferroferric oxide. But not limited to this; Example 1

[0014] The magnesium smelting waste slag was passed through a 300-mesh sieve to remove the large pieces of dolomite, ferrosilicon, fluorite, bricks and other debris left over from magnesium smelting, and fine magnesium smelting waste slag powder was obtained. -1 The ammonium acetate solution was mixed with the magnesium smelting waste slag powder at a liquid-to-solid ratio of 160:1 by volume and mass, and the reaction temperature was 45 °C and the rotation speed was 300 r·min -1 The reaction was carried out under the conditions for 60 min, and the tail gas recycling device was connected to absorb the generated NH3. The calcium ion concentration in the clear solution was titrated by EDTA titration and the calcium extraction rate was calculated. The reaction was considered complete when the calcium extraction rate no longer increased significantly with the extension of the reaction time. The calcium extraction rate obtained under the above conditions was 91%. The suspension after the reaction was filtered, and the calcium component entered the leachate in the form of calcium salt. After the leaching residue was collected and dried, 10 g was weighed and added to 200 mL of a proton concentration of 6.0 mol·L -1 The reaction mixture was added into a hydrogen chloride aqueous solution at 50 °C for 30 min, and silica was obtained after filtration with a yield of 98% and a purity of 95%.

[0015] Example 2-4: The steps of Examples 2-4 are the same as those of Example 1, and the specific process conditions and performance are shown in Table 1.

[0016] Table 1 Specific process conditions and performance of Examples 2-4 Serial number Screening mesh number Reaction temperature / ℃ <![CDATA[Calcium agent concentration / g·L -1 > Liquid-to-solid ratio Time / min <![CDATA[Rotational speed / r·min -1 > Calcium extraction rate / % Silicon dioxide yield / % Example 2 300 45 120 60 60 300 85 98% Example 3 300 45 120 80 60 300 86 98% Example 4 300 45 120 120 60 300 87 98% Attached Figure 2 It shows that the main components of the magnesium smelting waste slag used are dicalcium silicate, magnesium oxide, calcium ferrite and ferrosoferric oxide.

[0017] Attached Figure 3The results show that under different liquid-to-solid ratios, the calcium extraction rate of the calcium extracting agent ammonium acetate used in the present invention on magnesium smelting waste slag is significantly better than that of the traditional calcium extracting agent ammonium chloride.

[0018] Attached Figure 4 The main component of the silica product is amorphous silica.

[0019] The present invention discloses a method for extracting calcium and silicon components from magnesium smelting waste slag by using the "Pidgeon method", which has a high calcium extraction rate and realizes efficient extraction and separation of calcium and silicon components from magnesium smelting waste slag. The obtained calcium-containing leaching solution and silicon-containing leaching slag have high effective component content and can be directly used as excellent raw materials for preparing calcium and silicon products. The tail gas NH3 and acetate in the filtrate generated in the process of extracting calcium from magnesium smelting waste slag can be recycled, which promotes the comprehensive resource utilization of magnesium smelting waste slag and reduces the pollution of magnesium smelting waste slag to the environment. The prepared calcium and silicon products are expected to create greater economic benefits.

Claims

1. A method for extracting calcium and silicon from magnesium smelting waste slag, characterized in that: The method comprises the following steps: a. The magnesium smelting waste slag is sieved to obtain a fine magnesium smelting waste slag powder, and then added to the reactor in proportion with the calcium extracting agent solution, and the reactor is connected to the exhaust gas recycling device; b. The magnesium smelting waste slag powder reacts with the calcium extracting agent solution, and after the reaction, the suspension is filtered to obtain a calcium salt solution and a silicon-containing leached slag; c. The silicon-containing leaching is treated with an acid solution and then filtered to obtain silicon dioxide; The components of the magnesium smelting waste slag in the above step a include dicalcium silicate, magnesium oxide, and iron compounds, with their mass fractions being 70%-80%, 1%-5%, and 10%-15%, respectively, wherein the iron compounds include calcium ferrite and ferroferric oxide.

2. The method for extracting calcium and silicon from magnesium smelting waste slag according to claim 1, characterized in that: The particle size of the magnesium smelting waste slag powder in step a is 100-300 meshes.

3. The method for extracting calcium and silicon from magnesium smelting waste slag according to claim 1, characterized in that: The calcium extracting agent in step a is ammonium acetate, glycine, or a mixture of the two.

4. The method for extracting calcium and silicon from magnesium smelting waste slag according to claim 1, characterized in that: The concentration of the calcium extracting agent solution in step a is 80-400 g·L -1 .

5. The method for extracting calcium and silicon from magnesium smelting waste slag according to claim 1, characterized in that: The liquid-to-solid ratio between the volume of the calcium extracting agent solution and the mass of the magnesium smelting waste slag powder in step a is 60:1-200:

1.

6. The method for extracting calcium and silicon from magnesium smelting waste slag according to claim 1, characterized in that: The reaction temperature in step b is 40-100°C.

7. The method for extracting calcium and silicon from magnesium smelting waste slag according to claim 1, characterized in that: The acid solution used in step c is an aqueous solution of hydrogen chloride.

8. The method for extracting calcium and silicon from magnesium smelting waste slag according to claim 1, characterized in that: The proton concentration of the acid solution used in step c is 1.4-8.0 mol·L -1 .

9. The method for extracting calcium and silicon from magnesium smelting waste slag according to claim 1, characterized in that: The liquid-to-solid ratio between the volume of the acid solution in step c and the mass of the leached residue is 10:1-40:

1.

10. The method for extracting calcium and silicon from magnesium smelting waste slag according to claim 1, characterized in that: The reaction temperature in step c is 20-60°C.

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