A method for selectively leaching calcium and magnesium components from smelting slag

Abstract

The present invention discloses a method for selectively leaching calcium and magnesium components from smelting slag. This method uses a short-chain fatty acid solution with an H⁺ concentration ≤ 5 mol / l as the initial leaching agent to perform multi-stage countercurrent leaching on the smelting slag, obtaining a calcium and magnesium leaching solution and leaching residue. Based on the occurrence forms of calcium and magnesium components in the smelting slag and the dissolution characteristics of low-concentration short-chain fatty acids, this method combines with a multi-stage countercurrent leaching process to achieve the efficient and selective leaching of calcium and magnesium components from the smelting slag. Moreover, the calcium and magnesium leaching solution can be used for flue gas carbon capture, and the leaching residue can be used as raw materials for ironmaking or building materials, realizing the efficient and high-quality utilization of smelting slag, greatly promoting the resource utilization of smelting slag and the carbon capture of metallurgical flue gas.

Description

Technical Field

[0001] The present invention relates to a method for selectively leaching calcium and magnesium components from smelting slag, and particularly to a method for selectively leaching calcium and magnesium components from smelting slag by multi-stage countercurrent leaching using a low-concentration short-chain fatty acid solution, belonging to the technical field of comprehensive utilization of industrial solid waste resources. Background Art

[0002] At present, the existing technologies for resource utilization of steel slag mainly use finely ground steel slag as building materials. However, due to the high content of free calcium oxide (f-CaO) in steel slag, it is easy to cause volume expansion of building materials and trigger structural safety problems.

[0003] Carbon emission reduction is an important problem faced by the high-quality development of the iron and steel industry. The existing carbon capture technologies mainly target the coal-fired power generation field. Due to the low concentration of CO 2 in the flue gas of the iron and steel industry, the capture is difficult and the cost is high.

[0004] The calcium and magnesium content in smelting slag is high, and the reaction with CO 2 can achieve carbon capture. The carbon sequestration in smelting slag not only helps iron and steel enterprises to realize the "in-situ" utilization of smelting slag and carbon emission reduction, but also can reduce the resource and energy consumption in the whole life cycle of iron and steel production. It is a very promising flue gas carbon capture process. The leaching of calcium and magnesium components in smelting slag is a prerequisite for efficient mineralization of CO 2 .

[0005] At present, some leaching methods for calcium and magnesium components in smelting slag have been published in the literature. Jo, et al., (Energy, 2017, 884–894) and Tian, et al., (Chem. Sus. Chem., 2015, 3839–3846) respectively used HCl and HNO 3 to extract the calcium-containing components in steel slag. It was found that although inorganic acids can quickly dissociate calcium and magnesium minerals in smelting slag and achieve the leaching of most calcium and magnesium in smelting slag, a large amount of iron, aluminum, and silicon elements will also be leached at the same time. The leaching solution needs to be purified before the selective leaching of calcium and magnesium components can be achieved. In recent years, short-chain fatty acids such as acetic acid, propionic acid, and butyric acid have been widely used in the extraction process of calcium and magnesium components in smelting slag. Chang et al., (ACS Sustain. Chem.Eng., 2012) used short-chain fatty acids to leach the calcium-containing components in smelting slag, but the results showed that there were problems such as slow dissolution rate and low leaching rate in the leaching process of short-chain fatty acids. Summary of the Invention

[0006] In view of the problems that existing smelting slag is difficult to utilize as a resource, the selectivity of the inorganic acid leaching process of smelting slag is poor, and the efficiency of organic acid leaching of smelting slag is low, the purpose of the present invention is to provide a method for selective leaching of calcium and magnesium components from smelting slag. The method utilizes the occurrence form of calcium and magnesium components in smelting slag and the solubility characteristics of low-concentration short-chain fatty acids to coordinate a multi-stage countercurrent leaching process to achieve selective leaching of calcium and magnesium components from smelting slag. The method has the characteristics of rapid and efficient leaching, and provides a new way for the harmless, high-value and large-scale utilization of smelting slag.

[0007] In order to achieve the above technical purpose, the present invention provides a method for selectively leaching calcium and magnesium components from smelting slag, which is based on H + A short-chain fatty acid solution with a concentration of ≤5 mol / l is used as an initial leaching agent to carry out multi-stage countercurrent leaching on the smelting slag to obtain a calcium-magnesium leaching solution and leaching slag.

[0008] Since the smelting slag contains a large amount of free calcium and magnesium oxides (f-MO, M represents Ca or Mg), these calcium and magnesium oxides are alkaline and have high leaching activity. At the same time, the smelting slag also contains bound calcium and magnesium MO, such as calcium silicate and magnesium silicate, etc., and the leaching activity of these bound calcium and magnesium is relatively low. Therefore, in the conventional acid leaching process, the free calcium and magnesium oxides in the smelting slag will be preferentially leached by acid at the beginning of leaching, resulting in not only a large amount of acid consumption in the early stage of leaching, but also mainly leaching free calcium and magnesium oxides (f-MO). In the later stage of leaching, due to the decrease in the acid concentration in the leachate, the residual calcium and magnesium are mainly bound calcium and magnesium, resulting in low calcium and magnesium leaching efficiency. If a high concentration of acid is used in the early stage of leaching, although the leaching of bound calcium and magnesium in the later stage of leaching can be guaranteed, the leaching selectivity will decrease. If a low concentration of acid is used in the early stage of leaching, the leaching selectivity can be guaranteed, but the leaching rate in the later stage of leaching is slow. The key to the technology of the present invention is to propose a method for leaching calcium and magnesium components from smelting slag through multi-stage countercurrent based on the occurrence form and dissolution control mineral phase characteristics of calcium and magnesium components in smelting slag, ingeniously combining the dissolution-promoting characteristics of short-chain fatty acid solution, and realizing efficient and highly selective dissolution of calcium and magnesium components from smelting slag, effectively overcoming the problems of poor selectivity of inorganic acid leaching process and low efficiency of organic acid leaching, and creating favorable conditions for efficient carbon fixation of smelting slag. The technical solution of the present invention adopts the specific process of leaching smelting slag through multi-stage countercurrent using short-chain fatty acid solution (see Figure 1 ) and the mechanism of action is that: due to the H + The concentration is relatively the lowest and is basically consumed. During the leaching process, the free calcium oxide and free magnesium oxide in the smelting slag preferentially combine with the water in the leaching solution, and release calcium ions and magnesium ions at the same time, realizing the initial leaching of calcium and magnesium components in the smelting slag (as shown in reaction formula 1). In the Nth stage countercurrent leaching process, H +The concentration is relatively the highest, and the free calcium oxide and free magnesium oxide in the smelting slag are basically consumed. It is mainly that the short-chain fatty acid leaches the bound calcium and magnesium M-O, and the M-O (M represents metal ions) chemical bonds in calcium silicate and magnesium silicate are broken by the H in the short-chain fatty acid. At the same time, RCOO- in the short-chain fatty acid complexes with M to form an organic ligand (Reaction Formula 2), reducing the liquid-phase saturation index and realizing the complete leaching of calcium and magnesium components in the smelting slag. Based on the relatively low initial concentration of the short-chain fatty acid solution in this leaching process, the leaching of other metals is avoided, improving the leaching selectivity. At the same time, the leaching of free calcium and magnesium oxides (f-MO) and bound calcium and magnesium (M-O) in the smelting slag is carried out step by step, minimizing the acid consumption and greatly improving the leaching efficiency. + is broken, and at the same time, RCOO- in the short-chain fatty acid complexes with M to form an organic ligand (Reaction Formula 2), reducing the liquid-phase saturation index and realizing the complete leaching of calcium and magnesium components in the smelting slag. Based on the relatively low initial concentration of the short-chain fatty acid solution in this leaching process, the leaching of other metals is avoided, improving the leaching selectivity. At the same time, the leaching of free calcium and magnesium oxides (f-MO) and bound calcium and magnesium (M-O) in the smelting slag is carried out step by step, minimizing the acid consumption and greatly improving the leaching efficiency.

[0009] f-MO + H 2 O → M 2+ + OH - (Reaction Formula 1)

[0010] MSiO 4 + H + → M 2+ + SiO 2 + H 2 O (Reaction Formula 2)

[0011] M represents Ca or Mg.

[0012] In the technical solution of the present invention, the control of the concentration of short-chain fatty acids is crucial. A high solution concentration will cause the leaching of components such as iron and aluminum while the calcium and magnesium components in the smelting slag are leached, resulting in a decrease in the selectivity of calcium and magnesium components during the leaching process. In addition, the calcium and magnesium leaching solution obtained by this leaching method can be used for the capture of flue gas carbon in steel production, boosting the development of carbon capture technology in the steel industry. At the same time, according to the iron content of the leaching slag of the present invention, the iron-rich slag can be used as a raw material for steel production, for processes such as sintering and pelletizing, and the leaching slag with a lower iron content can be used as a raw material for building materials, efficiently realizing the recycling of resources.

[0013] As a preferred solution, the smelting slag includes at least one of blast furnace slag, electric furnace steel slag, converter steel slag, and ladle refining slag, and the preferred smelting slag contains rich calcium and magnesium components.

[0014] As a preferred solution, the smelting slag is classified according to the cooling method and includes at least one of water-quenched slag, hot-poured slag, air-quenched slag, roller slag, granulated slag, and hot-soaked slag.

[0015] As a preferred solution, after the smelting slag is crushed and screened, the average particle size of the smelting slag is controlled to be ≤3 mm. If the average particle size of the smelting slag is too coarse, the solid-liquid reaction rate and diffusion rate during the leaching process of the smelting slag will be severely reduced, affecting the leaching rate of calcium and magnesium components, resulting in a slow leaching rate and a low leaching rate.

[0016] As a preferred solution, the H + concentration of the short-chain fatty acid solution is 1-5 mol / l. Within the preferred H + concentration range, not only can the efficient and highly selective leaching of bound calcium and magnesium in the smelting slag be ensured, but also the leaching of other metals can be avoided.

[0017] As a preferred solution, the short-chain fatty acid is a fatty acid with less than 6 carbon atoms. The present invention makes full use of the fact that H + in the organic fatty acid during the dissolution process of the smelting slag can destroy the chemical bond between metal ions and oxygen atoms in bound calcium silicate and magnesium silicate in the smelting slag. At the same time, RCOO- in the organic fatty acid complexes with metal ions to form an organic ligand, reducing the liquid-phase saturation index, thereby promoting the dissolution of calcium ions and magnesium ions in the leaching system. Compared with other organic fatty acids, the short-chain organic fatty acid with less than 6 carbon atoms is more likely to hydrolyze H + in the leaching system, which has a better promoting effect on the leaching effect of calcium and magnesium components in the smelting slag.

[0018] As a more preferred solution, the low-concentration short-chain fatty acid is at least one of acetic acid, propionic acid, isobutyric acid, butyric acid, isovaleric acid, and valeric acid.

[0019] As a preferred solution, the multi-stage countercurrent leaching includes N-stage countercurrent leaching. The process of multi-stage countercurrent leaching is as follows: In the first-stage countercurrent leaching, the leaching solution obtained from the second-stage countercurrent leaching is used as the leaching agent to leach the smelting slag. The obtained leaching residue enters the second-stage countercurrent leaching. In the second-stage countercurrent leaching, the leaching solution obtained from the third-stage countercurrent leaching is used as the leaching agent to leach the leaching residue obtained from the first-stage countercurrent leaching, and so on. In the N-stage countercurrent leaching, the initial leaching agent is used to leach the leaching residue obtained from the (N-1)-stage countercurrent leaching.

[0020] As a more preferred embodiment, the multi-stage countercurrent leaching includes 2 to 6 stages of countercurrent leaching. During the countercurrent leaching process of each stage, the mass ratio of the smelting slag to the leaching agent is 1:1 to 10, the leaching temperature is 5 to 80 °C, and mechanical stirring is used to assist the leaching. The dosage of the leaching agent determines the leaching rate of calcium and magnesium components in the smelting slag. Appropriately increasing the dosage of the short-chain fatty acid solution is beneficial to improving the leaching rate of calcium and magnesium components. However, when the dosage of the short-chain fatty acid is too high, it will cause the rapid dissolution of free calcium and magnesium in the primary leaching stage. In the subsequent leaching process, the excessive short-chain fatty acid will combine with iron- and aluminum-containing components, resulting in a large amount of iron and aluminum leaching, thereby increasing the leaching cost, reducing the leaching rate of calcium and magnesium components and the leaching selectivity of calcium and magnesium components. The number of leaching stages determines the solid-liquid contact time between the short-chain fatty acid solution and the smelting slag. Increasing the number of leaching stages is beneficial to the full contact between the smelting slag and the leaching medium and improving the leaching rate of calcium and magnesium components. However, it will also cause the extension of the leaching time and affect the leaching efficiency per unit time. It is found that when the number of leaching stages is 2 to 6, the leaching rate of calcium and magnesium components in the smelting slag and the leaching efficiency per unit time are both relatively good, and less iron, aluminum and other components are dissolved during the leaching process, showing a high selective leaching effect for calcium and magnesium. Too low temperature will lead to slow reaction rate and affect the leaching efficiency. Increasing the temperature is beneficial to improving the leaching rate. However, too high temperature will accelerate the volatilization of short-chain fatty acids, resulting in a decrease in the content of short-chain fatty acids in the leaching system and having an adverse effect on leaching. It is found that when the leaching temperature is 5 to 80 °C, the leaching efficiency of calcium and magnesium components in the smelting slag is relatively good. As a preferred embodiment, the stirring method used in the multi-stage countercurrent leaching is at least one of mechanical stirring, gas stirring, ultrasonic wave and oscillation. Stirring can strengthen the solid-liquid contact during the leaching process and improve the leaching efficiency.

[0021] As a preferred embodiment, the calcium and magnesium leaching solution is used for flue gas carbon capture.

[0022] As a preferred embodiment, the leaching residue is used as raw material for ironmaking or building materials.

[0023] Compared with the prior art, the beneficial technical effects brought by the technical solution of the present invention are as follows:

[0024] 1) The method for selectively leaching calcium and magnesium components from the smelting slag of the present invention cleverly utilizes the principle of promoting dissolution by short-chain fatty acid ligands to construct a selective leaching medium system mainly composed of low-concentration short-chain fatty acids, creating favorable conditions for the selective leaching of calcium and magnesium in the smelting slag, and deeply revealing the occurrence forms of calcium and magnesium components in the smelting slag, the leaching behaviors of different mineral phases and the dissolution-controlled mineral phases.

[0025] 2) The method for selectively leaching calcium and magnesium components from smelting slag of the present invention constructs a multi-stage countercurrent leaching process with low-concentration short-chain fatty acids. By making the leaching medium contact the smelting slag countercurrently, on the one hand, it realizes the step-by-step leaching of calcium and magnesium components in different mineral phases such as free calcium oxide and silicate in the smelting slag in water and weak acid, and on the other hand, it makes full use of the countercurrent process to increase the solid-liquid contact time, ensuring the full leaching of calcium and magnesium components, so as to synergistically achieve the efficient and selective leaching of calcium and magnesium components from the smelting slag, effectively solving the problems of low calcium and magnesium dissolution rate and poor selectivity during the carbon sequestration process of the smelting slag.

[0026] 3) The leaching solution obtained by the leaching method of the present invention can be used for the capture of flue gas carbon in steel production, boosting the development of carbon capture technology in the steel industry. At the same time, according to the iron content of the leaching slag of the present invention, the iron-rich slag can be used as a raw material for steel production, for processes such as sintering and pelletizing, and the leaching slag with a lower iron content can be used as a raw material for building materials, featuring strong operability, low cost, and suitability for large-scale production.

[0027] 4) The present invention requires less leaching medium and has a short treatment process flow, showing the potential for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the method for selectively leaching calcium and magnesium components from smelting slag.

[0029] Figure 2 It is a process flow diagram of the method for selectively and efficiently dissolving calcium and magnesium components from smelting slag. DETAILED DESCRIPTION OF THE INVENTION

[0030] To facilitate the understanding of the present invention, the following will describe the present invention in a more comprehensive and detailed manner in combination with preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0031] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0032] Unless otherwise specified, various reagents and raw materials used in the present invention are all commercially available products or products that can be prepared by well-known methods.

[0033] In the following embodiments, converter steel slag is used as the raw material, and its main components are CaO, SiO 2 , Fe 2 O 3 , MgO, etc., and the specific components are shown in Table 1.

[0034] Table 1 Chemical Composition of Converter Steel Slag (%)

[0035]

[0036] Example 1

[0037] The converter steel slag was crushed and screened to obtain particles with an average particle size ≤ 3 mm. A 3 mol / l acetic acid solution was used as the leaching medium. The mass ratio of the converter steel slag to the acetic acid solution was maintained at 1:4, the number of leaching stages was 2, the leaching temperature was 30 °C, mechanical stirring was carried out at a rotation speed of 100 rpm, and countercurrent leaching was performed. After leaching was completed, filtration was carried out, and the concentrations of Ca 2+ , Mg 2+ , Fe 3+ , Al 3+ in the leachate were detected by ICP. According to the initial content in the converter steel slag, the leaching rates of Ca 2+ , Mg 2+ were 87.9% and 73.7% respectively, and the concentrations of Fe 3+ , Al 3+ were 0.9 mg / l and 0.4 mg / l respectively.

[0038] Example 2

[0039] The converter steel slag was crushed and screened to obtain particles with an average particle size ≤ 3 mm. A mixed solution of acetic acid, propionic acid, and butyric acid was used as the leaching medium. The contents of acetic acid, propionic acid, and butyric acid in the mixed solution were 1:1:1, and the concentration of the mixed solution was 5 mol / l. The mass ratio of the converter steel slag to the mixed acid solution was maintained at 1:6, the number of leaching stages was 6, the leaching temperature was 25 °C, and oscillating stirring was carried out for countercurrent leaching. After leaching was completed, filtration was carried out, and the concentrations of Ca 2+ , Mg 2+ , Fe 3+ , Al 3+ in the leachate were detected. According to the initial content in the converter steel slag, the leaching rates of Ca 2+ , Mg 2+ were 99.6% and 94.3% respectively, and the concentrations of Fe 3+ , Al 3+ were 1.1 mg / l and 0.9 mg / l respectively.

[0040] Example 3

[0041] The converter steel slag was crushed and screened to obtain particles with an average particle size ≤ 3 mm. A 1 mol / l valeric acid solution was used as the leaching medium. The mass ratio of the converter steel slag to the valeric acid solution was maintained at 1:10, the number of leaching stages was 4, the leaching temperature was 80 °C, mechanical stirring was carried out at a rotation speed of 150 rpm, and countercurrent leaching was performed. After leaching was completed, filtration was carried out, and the concentrations of Ca 2+ , Mg 2+ , Fe 3+ , Al 3+ in the leachate were detected. According to the initial content in the converter steel slag, calculate Ca2+ , Mg 2+ The leaching rates are 92.1% and 88.5% respectively, and the concentrations of Fe 3+ , Al 3+ are 0.4 mg / l and 0.5 mg / l respectively.

[0042] Example 4

[0043] The converter steel slag was crushed and screened to obtain particles with an average particle size ≤ 3 mm. A mixed solution of acetic acid and butyric acid with a concentration of 4 mol / l was used as the leaching medium. The content of acetic acid and butyric acid in the mixed solution was 2:1. The mass ratio of converter steel slag to the mixed solution was kept at 1:1, the number of leaching stages was 2, the leaching temperature was 5 °C, and N 2 gas stirring was carried out with a gas flow rate of 1.0 m 3 / (min·m 2 ). Countercurrent leaching was carried out. After the leaching was completed, filtration was carried out, and the concentrations of Ca 2+ , Mg 2+ , Fe 3+ , Al 3+ in the leachate were detected. According to the initial content in the converter steel slag, the leaching rates of Ca 2+ , Mg 2+ were calculated to be 89.4% and 75.2% respectively, and the concentrations of Fe 3+ , Al 3+ were 0.3 mg / l and 0.3 mg / l respectively.

[0044] Comparative Example 1

[0045] Compared with Example 1, the only difference is that the concentration of the acetic acid solution is 8 mol / l.

[0046] The finally obtained leaching rates of Ca 2+ , Mg 2+ are 90.1% and 74.4% respectively. The leaching rates of Ca 2+ , Mg 2+ are slightly higher than those in Example 1, but the concentrations of Fe 3+ , Al 3+ are 34.6 mg / l and 29.7 mg / l respectively. When the short-chain fatty acid solution of the leaching medium is too high, the leaching selectivity of Ca 2+ , Mg 2+ decreases.

[0047] Comparative Example 2

[0048] Compared with Example 3, the only difference is that the mass ratio of converter steel slag to valeric acid solution is 1:15.

[0049] The finally obtained Ca 2+ , Mg 2+The leaching rates are 89.8% and 71.5% respectively, and the Fe 3+ and Al 3+ concentrations are 25.4 mg / l and 18.8 mg / l respectively. When the dosage of the low-concentration short-chain fatty acid solution is too high, free calcium and magnesium dissolve rapidly in the primary leaching stage. However, in the subsequent leaching process, the excessive short-chain fatty acids combine with iron- and aluminum-containing components, resulting in a large amount of iron and aluminum dissolution and reducing the leaching selectivity of Ca 2+ and Mg 2+ .

[0050] Comparative Example 3

[0051] Compared with Example 2, the only difference is that the average particle size of the converter steel slag > 3 mm.

[0052] The finally obtained Ca 2+ and Mg 2+ leaching rates are 82.5% and 67.4% respectively, and the Fe 3+ and Al 3+ concentrations are 1.4 mg / l and 0.8 mg / l respectively. The increase in particle size seriously reduces the solid-liquid reaction and diffusion rates during leaching, resulting in a significant decrease in the leaching rates of Ca 2+ and Mg 2+ .

[0053] Comparative Example 4

[0054] Compared with Example 2, the only difference is that the leaching stage is 1 stage, that is, the converter steel slag is directly mixed with the short-chain fatty acid solution for leaching.

[0055] The finally obtained Ca 2+ and Mg 2+ leaching rates are 80.7% and 59.3% respectively, and the Fe 3+ and Al 3+ concentrations are 7.6 mg / l and 5.1 mg / l respectively. By using direct leaching, the calcium, magnesium, iron, and aluminum components in the converter steel slag directly react with the short-chain fatty acids, resulting in a large amount of acid consumption by the preferentially dissolved free calcium and free magnesium, affecting the dissolution of calcium silicate and magnesium silicate in the subsequent process. Moreover, there is a competitive relationship between the reaction of iron and aluminum components and the dissolution of calcium and magnesium, resulting in a decrease in the leaching rates and selectivity of Ca 2+ and Mg 2+ .

Claims

1. A method for selectively leaching calcium and magnesium components from smelting slag, characterized in that: Using a short-chain fatty acid solution with an H + concentration ≤ 5 mol / l as the initial leaching agent, the smelting slag is subjected to multi-stage countercurrent leaching to obtain a calcium and magnesium leachate and a leaching residue; the average particle size of the smelting slag is ≤ 3 mm; The H of the short-chain fatty acid solution + has a concentration of 1 to 5 mol / l; the multi-stage countercurrent leaching includes N-stage countercurrent leaching, and the process of multi-stage countercurrent leaching is as follows: the first-stage countercurrent leaching uses the leachate obtained from the second-stage countercurrent leaching as the leaching agent to leach the smelting slag, and the obtained leached slag enters the second-stage countercurrent leaching. The second-stage countercurrent leaching uses the leachate obtained from the third-stage countercurrent leaching as the leaching agent to leach the leached slag obtained from the first-stage countercurrent leaching, and so on. The N-stage countercurrent leaching uses the initial leaching agent to leach the leached slag obtained from the (N - 1)-stage countercurrent leaching; the multi-stage countercurrent leaching includes 2 - 6 stages of countercurrent leaching. During the countercurrent leaching process of each stage, the mass ratio of the smelting slag to the leaching agent is 1:1 - 10, the leaching temperature is 5 - 80 °C, and stirring is used to assist leaching.

2. A method for selectively leaching calcium and magnesium components from smelting slag according to claim 1, characterized in that: the smelting slag includes at least one of blast furnace slag, electric furnace steel slag, converter steel slag, and ladle refining slag.

3. A method for selectively leaching calcium and magnesium components from smelting slag according to claim 1, characterized in that: the short-chain fatty acid is a fatty acid with less than 6 carbon atoms.

4. A method for selectively leaching calcium and magnesium components from smelting slag according to claim 3, characterized in that: the short-chain fatty acid is at least one of acetic acid, propionic acid, isobutyric acid, butyric acid, isovaleric acid, and valeric acid.

5. A method for selectively leaching calcium and magnesium components from smelting slag according to claim 1, characterized in that: the calcium and magnesium leachate is used for flue gas carbon capture; the leached slag is used as raw material for ironmaking or building materials.

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