Method for utilizing converter steel slag and fixing carbon dioxide

Abstract

The application discloses a method for utilizing converter steel slag and fixing carbon, and steps include mixing the steel tailing slag after crushing and grinding with water to obtain a slurry, and performing acid leaching with dilute hydrochloric acid, maintaining a certain pH value, and simultaneously heating and mechanically stirring the slurry; after the acid leaching, the slurry is separated by suction filtration to obtain a precipitate A and a leaching solution A; lime mud is added to the leaching solution A until the pH value of the solution is 6.8-7.2, CO2 gas is introduced until the pH value is constant, and suction filtration is performed to obtain a precipitate B and a leaching solution B. The method simplifies the operation process, improves the operation efficiency, has a smaller erosion degree on equipment, and is expected to bring remarkable environmental protection benefits and social values for the field of environmental protection.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical resource recycling technology, specifically a method for utilizing and carbonizing converter steel slag. Background Technology

[0002] my country's steel industry ranks first in the world, but behind this remarkable achievement, the problem of converter slag is becoming increasingly prominent. As an indispensable by-product of the steelmaking process, converter slag accounts for about 10% of crude steel production, and my country generates nearly 100 million tons of slag annually.

[0003] According to authoritative statistics, the comprehensive utilization rate of steel slag in my country is still insufficient, at only about 30%, far behind the international advanced level. Currently, many steel plants, after extracting iron through magnetic separation, pile up the remaining steel tailings into slag mountains. This not only occupies a large amount of land resources but also requires a natural aging process of nearly a year before it can be used in building materials and road materials. More importantly, my country implemented a policy banning steel slag cement in 2023, which undoubtedly makes the challenge of steel slag disposal even more severe, urgently requiring the exploration of new solutions to properly handle the mountains of steel slag.

[0004] Therefore, developing a highly efficient technology for treating accumulated steel tailings is particularly urgent. This technology should be able to accurately extract useful components from the slag, enabling its resource utilization while minimizing environmental pollution. Continuously improving the comprehensive utilization rate of steel slag can not only effectively address the current problems of resource waste and environmental pollution, but also open up new avenues for the green development of the steel industry.

[0005] Patent CN202111624915.6 discloses a method for preparing calcium carbonate by enriching vanadium in vanadium-containing steel slag. The specific steps are as follows: Vanadium-containing steel slag and an ammonium salt solution are mixed to obtain vanadium-rich slag and a calcium-rich solution. The calcium-rich solution is then purified by separating impurities. Micro-nano carbon dioxide bubbles are then introduced into the purified solution to induce a precipitation reaction. Solid-liquid separation is then performed to obtain the calcium carbonate product. However, the ammonium salt solution in this method is a weak acid salt and cannot effectively dissolve the calcium element in the steel slag.

[0006] Patent CN202311145171.9 discloses a comprehensive method for recovering vanadium and ferrovanadium from vanadium-containing steel slag. The specific content is as follows: vanadium-containing steel slag is roasted with ammonium sulfate at low temperature. After the roasted clinker is cooled, it undergoes a first leaching and filtration to obtain a first leachate and a first leaching residue. Ammonia and carbon dioxide or ammonium bicarbonate are then added to the first leaching residue for mineralization and carbon fixation. This method uses low-temperature roasting technology to treat the steel slag, solving the problem of calcium dissolution; however, heating consumes additional energy. Summary of the Invention

[0007] This invention provides a method for utilizing and carbonizing converter steel slag, aiming to effectively solve the problem of rapid treatment of steel tailings and significantly improve the utilization rate of steel slag, thereby avoiding resource waste. This invention not only has significant economic benefits but also greatly benefits society, demonstrating broad application prospects.

[0008] To achieve the above objectives, the present invention employs the following technical solution:

[0009] A method for utilizing and carbonizing converter steel slag, the method comprising the following steps:

[0010] Step 1: Mix the crushed and ground steel tailings with water to obtain a slurry, and use a dilute hydrochloric acid solution for acid leaching to maintain a certain pH. At the same time, heat and mechanically stir the slurry to improve the kinetic conditions and promote the dissolution of the dicalcium silicate phase.

[0011] Step 2: After acid leaching, the slurry from Step 1 is filtered and separated to obtain precipitate A and leachate A;

[0012] Step 3: Add lime slurry to leachate A obtained in Step 2 until the pH of the solution is 6.8~7.2, then introduce CO2 gas until the pH remains unchanged, and filter to separate precipitate B and leachate B.

[0013] Preferably, in step one, the pH value of the acid leaching solution is maintained at 3.0~3.5, the heating temperature is 40~50 ℃, and the reaction time is 1~2 h.

[0014] Preferably, in step two, due to the dissolution and separation of the dicalcium silicate phase in the converter steel tail slag, the main component of precipitate A is dicalcium ferrite, with a content of 72-80%, which can be returned to the smelting process as iron material.

[0015] Preferably, in step three, the main component of precipitate B is calcium carbonate, with a content of 85-94%, which can be used in multiple fields such as papermaking and coatings; the main component of leachate B is silica gel, which can be used as a high-quality raw material for cement or glass.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects:

[0017] (1) This invention proposes a method for utilizing and carbonizing converter steel slag. Its advantage lies in that it can be operated at room temperature and has a low degree of corrosion to equipment. This characteristic not only greatly simplifies the operation process and improves the operation efficiency, but also has a positive impact on extending the service life of the equipment. In addition, this invention is also of great significance in environmental protection and promoting sustainable development. Its application is expected to bring significant environmental benefits and social value to related fields.

[0018] (2) In the product developed in this invention, dicalcium ferrite, with its excellent metallurgical flux properties, can be returned to the smelting process. At the same time, the calcium carbonate in the product has shown significant advantages in many fields such as papermaking and coatings, and silica gel, with its excellent properties, has become an indispensable high-quality raw material in cement or glass manufacturing. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of exemplary embodiments of the experimental method is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1

[0022] In this embodiment, converter slag from a steel plant was used for the experiment. The chemical composition of the slag is shown in Table 1.

[0023] Table 1. Chemical composition (wt%) of converter steel slag in Example 1

[0024] 44.19 19.33 10.96 10.20 1.72 4.99 2.26 5.91

[0025] The steel tailings comprehensive utilization method of the present invention is used to treat steel tailings, and the treatment steps are as follows:

[0026] Step 1: Mix the crushed and ground steel tailings with water to obtain a slurry, and then perform acid leaching with a dilute hydrochloric acid solution. The acid leaching solution is heated to 50 ℃, the reaction time is 1 h, the pH value is controlled at 3.0, and the slurry is mechanically stirred at the same time.

[0027] Step 2: After acid leaching, the slurry from Step 1 is filtered and separated to obtain leachate A and precipitate A. The chemical composition of precipitate A is shown in Table 2, with dicalcium ferrite as the main component, which contains 75%.

[0028] Table 2 Chemical composition (wt%) of precipitate A in Example 1

[0029] 32.66 0.81 1.41 49.40 0.41 3.94 4.82 6.28

[0030] Step 3: Add lime slurry to leachate A obtained in Step 2 until the pH of the solution is 6.8. Then, introduce CO2 gas until the pH remains constant. Filter to separate precipitate B and leachate B. The main component of precipitate B is calcium carbonate, with a content of 94%. The chemical composition of precipitate B is shown in Table 3. The main component of leachate B is silica gel, which can be used as a high-quality raw material for cement or glass.

[0031] Table 3 Chemical composition (wt%) of precipitate B in Example 1

[0032] 98.32 0.02 0.50 0.05 0.08 0.09 0.05 0.73 Example 2

[0033] In this embodiment, converter slag from a steel plant was used for the experiment. The chemical composition of the slag is shown in Table 4.

[0034] Table 4 Chemical composition (wt%) of converter steel slag in Example 2

[0035] 52.01 16.53 7.55 9.66 1.53 3.05 2.65 5.78

[0036] The steel tailings comprehensive utilization method of the present invention is used to treat steel tailings, and the treatment steps are as follows:

[0037] Step 1: Mix the crushed and ground steel tailings with water to obtain a slurry, and then perform acid leaching with a dilute hydrochloric acid solution. The acid leaching solution is heated to 40 ℃, the reaction time is 1.5 h, the pH value is controlled at 3.0, and the slurry is mechanically stirred at the same time.

[0038] Step 2: After acid leaching, the slurry from Step 1 is filtered and separated to obtain leachate A and precipitate A. The chemical composition of precipitate A is shown in Table 5, with dicalcium ferrite as the main component, which contains 80%.

[0039] Table 5 Chemical composition (wt%) of precipitate A in Example 2

[0040] 39.60 0.75 1.58 42.87 0.38 3.05 5.30 5.78

[0041] Step 3: Add lime slurry to leachate A obtained in Step 2 until the pH of the solution is 7.1. Then, introduce CO2 gas until the pH remains constant. Filter to separate precipitate B and leachate B. The main component of precipitate B is calcium carbonate, with a content of 92%. The chemical composition of precipitate B is shown in Table 6. The main component of leachate B is silica gel, which can be used as a high-quality raw material for cement or glass.

[0042] Table 6 Chemical composition (wt%) of precipitate B in Example 2

[0043] 98.05 0.02 0.45 0.05 0.07 0.07 0.06 0.99

[0044] Example 3

[0045] In this embodiment, converter slag from a steel plant was used for the experiment. The chemical composition of the slag is shown in Table 7.

[0046] Table 7 Chemical composition (wt%) of converter steel slag in Example 3

[0047] 52.13 15.87 7.86 9.59 1.93 2.50 2.99 5.99

[0048] The steel tailings comprehensive utilization method of the present invention is used to treat steel tailings, and the treatment steps are as follows:

[0049] Step 1: Mix the crushed and ground steel tailings with water to obtain a slurry, and then perform acid leaching with a dilute hydrochloric acid solution. The acid leaching solution is heated to 50 ℃, the reaction time is 2 h, the pH value is controlled at 3.5, and the slurry is mechanically stirred at the same time.

[0050] Step 2: After acid leaching, the slurry from Step 1 is filtered and separated to obtain leachate A and precipitate A. The chemical composition of precipitate A is shown in Table 8, with a dicalcium ferrite content of 72%.

[0051] Table 8 Chemical composition (wt%) of precipitate A in Example 3

[0052] 41.33 0.73 1.02 42.15 0.36 2.42 5.79 5.80

[0053] Step 3: Add lime slurry to leachate A obtained in Step 2 until the pH of the solution is 6.8. Then, introduce CO2 gas until the pH remains constant. Filter to separate precipitate B and leachate B. The main component of precipitate B is calcium carbonate, with a content of 86%. The chemical composition of precipitate B is shown in Table 9. The main component of leachate B is silica gel, which can be used as a high-quality raw material for cement or glass.

[0054] Table 9 Chemical composition (wt%) of precipitate B in Example 3

[0055] 98.10 0.03 0.66 0.05 0.07 0.09 0.05 0.70

Claims

1. A method for utilizing and carbonizing converter steel slag, characterized in that, Includes the following steps: Step 1: Mix the crushed and ground steel tailings with water to obtain a slurry, and use a dilute hydrochloric acid solution for acid leaching to maintain a certain pH. At the same time, heat and mechanically stir the slurry. Step 2: After acid leaching, the slurry described in Step 1 is filtered and separated to obtain precipitate A and leachate A; Step 3: Add lime slurry to the leachate A described in Step 2 until the pH of the solution is 6.8~7.2, then introduce CO2 gas until the pH remains unchanged, and filter to separate the precipitate B and leachate B.

2. The method for utilizing and carbonizing converter steel slag according to claim 1, characterized in that, In step one, the pH value of the acid leaching solution is maintained at 3.0~3.5, the heating temperature is 40~50 ℃, and the reaction time is 1~2 h.

3. The method for utilizing and carbonizing converter steel slag according to claim 1, characterized in that, In step two, the main component of precipitate A is dicalcium ferrite, with a content of 72-80%.

4. The method for utilizing and carbonizing converter steel slag according to claim 1, characterized in that, In step three, the main component of precipitate B is calcium carbonate, with a content of 85-94%.