Method for supercritical fixation of carbon dioxide by using steel slag semi-dry method

Abstract

The invention discloses a method for supercritical fixation of carbon dioxide through a steel slag semi-dry method, and belongs to the technical field of greenhouse gas carbon dioxide emission reduction and solid waste resource utilization. The method for supercritical fixation of carbon dioxide through the steel slag semi-dry method comprises the following steps that steel slag and water are mixed to obtain slurry, the slurry is fed into a reaction kettle, CO2 is introduced, a mineralization reaction is conducted in the CO2 supercritical state, a carbonation product is obtained, and fixation of carbon dioxide is completed. In order to reduce the consumption of water resources, a semi-dry method is adopted to carry out mineralization reaction, and on the basis, the defect of low reaction efficiency of a traditional process is overcome while the carbon sequestration amount is ensured by utilizing high diffusivity and high solubility of supercritical CO2, so that efficient mineralization and resource utilization of the steel slag are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of greenhouse gas carbon dioxide emission reduction and solid waste resource utilization, and in particular to a method for supercritical carbon dioxide fixation using steel slag semi-dry process. Background Art

[0002] CO2 mineralization is a key CO2 utilization method within the CO2 capture, utilization, and storage (CCUS) technology system. Within the CCUS technical framework, CO2 mineralization and storage technology demonstrates significant technical advantages and long-term storage potential due to its ability to convert CO2 into stable carbonate minerals by reacting elements such as calcium and magnesium in raw materials such as natural ores and industrial waste with CO2 to form stable carbonate products.

[0003] In this field, the use of natural ores for CO2 mineralization and storage faces many challenges, such as difficulty in obtaining resources, high costs, and the potential for a heavy burden on the environment. In contrast, the use of industrial waste for mineralization treatment can significantly save costs. Steel slag, as a solid waste generated by the steel industry, is rich in alkaline components such as calcium and magnesium oxides. It exhibits good performance in CO2 mineralization and fixation and can be used as a carbon capture material. However, it is relatively difficult to achieve a high carbon fixation rate, and due to the presence of f-CaO, etc., the product utilization rate is low, so further improvement is still needed. Summary of the Invention

[0004] The present invention aims to provide a method for supercritical carbon dioxide fixation using steel slag semi-dry process to address the above-mentioned problems in the background art. To reduce water resource consumption, the present invention adopts a semi-dry process for mineralization reaction. On this basis, by utilizing the high diffusivity and solubility of supercritical CO2, while ensuring the carbon fixation rate, it overcomes the shortcomings of the low reaction efficiency of the traditional process, thereby achieving efficient mineralization and resource utilization of steel slag.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention is to provide a method for supercritical carbon dioxide fixation using steel slag semi-dry method, comprising the following steps:

[0007] The steel slag is mixed with water to obtain a slurry, which is sent to a reactor and CO2 is introduced. A mineralization reaction is carried out under the supercritical state of CO2 to obtain a carbonation product, thus completing the fixation of carbon dioxide.

[0008] Preferably, the mass ratio of water to steel slag is 0.2-2:1.

[0009] Under the amount of water added in the present invention, the humidity conditions achieved can still enable CO2 to react quickly with steel slag.

[0010] Preferably, the steel slag is crushed to 100-200 mesh.

[0011] Preferably, the CO2 pressure during the mineralization reaction is 7.4-10 MPa.

[0012] Preferably, the temperature of the mineralization reaction is 40-80°C.

[0013] Preferably, the mineralization reaction time is 60-120 minutes.

[0014] Preferably, after the mineralization reaction, the method further comprises a step of drying the carbonation product.

[0015] More preferably, the drying temperature is 80-100° C. and the drying time is 1.5 h.

[0016] The reaction rate of traditional mineralization treatment in this field is too slow in the diffusion stage, which seriously restricts the carbonation efficiency. In view of this, the present invention designs an efficient carbon fixation solution by utilizing steel slag and supercritical carbon dioxide to carry out carbonation reaction.

[0017] The beneficial technical effects of the present invention are as follows:

[0018] In order to reduce water resource consumption, the present invention adopts a semi-dry method for mineralization reaction, and on this basis, by utilizing the high diffusivity and high solubility of supercritical CO2, while ensuring the carbon fixation amount, overcomes the shortcomings of low reaction efficiency of traditional processes, and realizes efficient mineralization and resource utilization of steel slag.

[0019] The present invention discloses a method for carbonation and sequestration of CO2 using a semi-dry process with steel slag and supercritical technology. By precisely controlling process parameters such as reaction temperature and pressure, combined with optimization of the material particle size distribution, the unique advantages of supercritical CO2 can be fully utilized. With its excellent diffusion properties and extremely low viscous stress, the supercritical CO2 fluid can quickly penetrate the surface of the material. Before the CaCO3 generated by the reaction has completely covered the material surface, it can quickly penetrate into the microporous structure inside the material, fully contacting and reacting with the active sites hidden inside, thereby significantly improving the depth and efficiency of the carbonation reaction, increasing the utilization rate of the steel slag, and achieving efficient mineralization of the steel slag.

[0020] The present invention not only achieves the permanent storage of CO2 greenhouse gas, but also simultaneously completes the resource utilization of industrial solid waste steel slag, showing significant environmentally friendly characteristics. DETAILED DESCRIPTION

[0021] Various exemplary embodiments of the present invention are now described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention.

[0022] In addition, for numerical ranges in the present invention, it is understood that each intervening value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any stated value or stated range, and any other stated value or intervening value in the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0023] Unless otherwise specified, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which the present invention pertains. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention. It should be noted that any details not described herein are conventional procedures in the art and are not the focus of the present invention.

[0024] The terms “include,” “including,” “have,” “contain,” etc. used in the present invention are open-ended terms, meaning including but not limited to.

[0025] CO2 mineralization and storage technology converts CO2 into stable carbonate minerals through chemical means. Its core principle is to utilize alkaline oxides (such as CaO and MgO) in natural ores or industrial waste to react with CO2 to form long-term stable carbonate minerals. This technology has become a key component of the CCUS (Carbon Capture, Utilization, and Storage) technology ecosystem due to its dual advantages of reducing CO2 emissions and repurposing solid waste.

[0026] Currently, research and application of CO2 mineralization and storage technologies are primarily focused on natural ores and industrial waste. While natural ores (such as olivine and serpentine) are abundant, they face bottlenecks such as fragmented resources, high mining costs, and slow reaction rates, making them difficult to meet the needs of large-scale emission reductions. In contrast, industrial waste (such as steel slag, fly ash, and carbide slag) has become a more promising mineralization raw material due to its rich calcium and magnesium content and concentrated sources. Steel slag, in particular, has become a research hotspot due to its high calcium oxide content.

[0027] Traditional mineralization technology faces two major bottlenecks: first, low reaction efficiency: while industrial waste reacts quickly, traditional wet processes are still limited by mass transfer; second, significant water consumption: approximately 25 cubic meters of water are required to store each ton of CO2, limiting its scalable application. Conventional wet mineralization processes require large amounts of water as a reaction medium. While this results in a more complete reaction, it is costly and produces significant amounts of wastewater. Dry processes, while less water-intensive, are limited by the CO2 diffusion rate, resulting in low reaction efficiency.

[0028] In view of the problems faced in these prior arts, the present invention designs a method for supercritical carbon dioxide fixation using steel slag semi-dry method, comprising the following steps:

[0029] The steel slag is mixed with water to obtain a slurry, which is sent to a reactor and CO2 is introduced. Under the supercritical state of CO2 (when the temperature reaches 31.1°C and the pressure reaches 7.38MPa, CO2 enters the supercritical state), a mineralization reaction is carried out to obtain a carbonation product, thereby completing the fixation of carbon dioxide.

[0030] Furthermore, the mass ratio of water to steel slag is 0.2-2:1.

[0031] Under the amount of water added in the present invention, the humidity conditions achieved can still enable CO2 to react quickly with steel slag.

[0032] Furthermore, the steel slag is crushed to 100-200 mesh.

[0033] Furthermore, the CO2 pressure during the mineralization reaction is 7.4-10 MPa.

[0034] Furthermore, the temperature of the mineralization reaction is 40-80°C.

[0035] Furthermore, the mineralization reaction time is 60-120 minutes.

[0036] Furthermore, after the mineralization reaction, the method further includes a step of drying the carbonation product.

[0037] Furthermore, the drying temperature is 80-100° C. and the drying time is 1.5 hours.

[0038] The steel slag used in the following examples and comparative examples of the present invention contains the following components: 50.07wt% CaO, 28.12wt% SiO2, 10.17wt% Al2O3 and 1.47wt% MgO.

[0039] Unless otherwise specified, the "room temperature" in the present invention is 10-30°C.

[0040] The raw materials used in the following examples and comparative examples of the present invention are all commercially available products.

[0041] Example 1

[0042] A method for supercritical carbon dioxide fixation using steel slag semi-dry method, the specific preparation process is as follows:

[0043] (1) The steel slag is mechanically crushed to 150 mesh to obtain steel slag powder.

[0044] (2) Water and steel slag powder were mixed at a liquid-to-solid mass ratio of 0.4:1 to obtain a slurry, which was then added to a high-temperature and high-pressure reactor.

[0045] (3) Use CO2 to purge the high-temperature and high-pressure reactor to remove the air in the reactor and complete the gas tightness test.

[0046] (4) Set the reaction temperature to 40°C, turn on the heater, and after the reactor temperature reaches the set temperature, turn on the power of the CO2 pump to increase the mineralization pressure to the predetermined pressure value of 7.5 MPa.

[0047] (5) After the reaction time reaches 60 min, the gas in the autoclave is released and the temperature is lowered to room temperature.

[0048] (6) flushing the autoclave with water and discharging the reaction mixture through the bottom discharge valve to obtain a mixed material.

[0049] (7) The obtained mixture is separated into water and carbonation product through a suction filtration device, and the separated water is recycled.

[0050] (8) The carbonation product is dried (dried at 100°C for 1.5 hours) to obtain a carbon-fixed product, which can be used as a building material.

[0051] The carbon fixation rate of this embodiment is 8.296% as determined by the ratio of the mass of the carbon fixation product to the mass of the steel slag before mineralization. Based on this, it can be seen that in this embodiment, 1 ton of steel slag powder can fix 82.96 kg of CO2.

[0052] Example 2

[0053] A method for supercritical carbon dioxide fixation using steel slag semi-dry method, the specific preparation process is as follows:

[0054] (1) The steel slag is mechanically crushed to 150 mesh to obtain steel slag powder.

[0055] (2) Water and steel slag powder are mixed in a liquid-to-solid mass ratio of 1:1 to obtain a slurry, which is then added to a high-temperature and high-pressure reactor.

[0056] (3) Use CO2 to purge the high-temperature and high-pressure reactor to remove the air in the reactor and complete the gas tightness test.

[0057] (4) Set the reaction temperature to 75°C, turn on the heater, and after the reactor temperature reaches the set temperature, turn on the power of the CO2 pump to increase the mineralization pressure to the predetermined pressure value of 7.5 MPa.

[0058] (5) After the reaction time reaches 60 min, the gas in the autoclave is released and the temperature is lowered to room temperature.

[0059] (6) flushing the autoclave with water and discharging the reaction mixture through the bottom discharge valve to obtain a mixed material.

[0060] (7) The obtained mixture is separated into water and carbonation product through a suction filtration device, and the separated water is recycled.

[0061] (8) The carbonation product is dried (dried at 100°C for 1.5 hours) to obtain a carbon-fixed product, which can be used as a building material.

[0062] The carbon fixation rate of this embodiment is 10.414% using the ratio of the mass of the carbon fixation product to the mass of the steel slag before mineralization. Based on this, it can be seen that in this embodiment, 1 ton of steel slag powder can fix 104.14 kg of CO2.

[0063] Example 3

[0064] A method for supercritical carbon dioxide fixation using steel slag semi-dry method, the specific preparation process is as follows:

[0065] (1) The steel slag is mechanically crushed to 150 mesh to obtain steel slag powder.

[0066] (2) Water and steel slag powder were mixed at a liquid-to-solid mass ratio of 0.4:1 to obtain a slurry, which was then added to a high-temperature and high-pressure reactor.

[0067] (3) Use CO2 to purge the high-temperature and high-pressure reactor to remove the air in the reactor and complete the gas tightness test.

[0068] (4) Set the reaction temperature to 75°C, turn on the heater, and after the reactor temperature reaches the set temperature, turn on the power of the CO2 pump to increase the mineralization pressure to the predetermined pressure value of 7.5 MPa.

[0069] (5) After the reaction time reaches 60 min, the gas in the autoclave is released and the temperature is lowered to room temperature.

[0070] (6) flushing the autoclave with water and discharging the reaction mixture through the bottom discharge valve to obtain a mixed material.

[0071] (7) The obtained mixture is separated into water and carbonation product through a suction filtration device, and the separated water is recycled.

[0072] (8) The carbonation product is dried (dried at 100°C for 1.5 hours) to obtain a carbon-fixed product, which can be used as a building material.

[0073] The carbon fixation rate of this embodiment is 15.48% as determined by the ratio of the mass of the carbon fixation product to the mass of the steel slag before mineralization. Based on this, it can be seen that in this embodiment, 1 ton of steel slag powder can fix 154.8 kg of CO2.

[0074] Comparative Example 1

[0075] A method for fixing carbon dioxide, the specific preparation process is as follows:

[0076] (1) The steel slag is mechanically crushed to 150 mesh to obtain steel slag powder.

[0077] (2) Water and steel slag powder were mixed at a liquid-to-solid mass ratio of 0.4:1 to obtain a slurry, which was then added to a high-temperature and high-pressure reactor.

[0078] (3) Use CO2 to purge the high-temperature and high-pressure reactor to remove the air in the reactor and complete the gas tightness test.

[0079] (4) Set the reaction temperature to 40°C, turn on the heater, and after the reactor temperature reaches the set temperature, turn on the power of the CO2 pump to increase the mineralization pressure to the predetermined pressure value of 0.85 MPa.

[0080] (5) After the reaction time reaches 60 min, the gas in the autoclave is released and the temperature is lowered to room temperature.

[0081] (6) flushing the autoclave with water and discharging the reaction mixture through the bottom discharge valve to obtain a mixed material.

[0082] (7) The obtained mixture is separated into water and carbonation product through a suction filtration device, and the separated water is recycled.

[0083] (8) The carbonation product is dried (dried at 100°C for 1.5 hours) to obtain a carbon-fixed product, which can be used as a building material.

[0084] The carbon fixation rate of this comparative example is 6.81% based on the ratio of the mass of the carbon fixation product to the mass of the steel slag before mineralization. Based on this, it can be seen that in this comparative example, 1 ton of steel slag powder can fix 68.1 kg of CO2.

[0085] Comparative Example 2

[0086] A method for fixing carbon dioxide, the specific preparation process is as follows:

[0087] (1) The steel slag is mechanically crushed to 150 mesh to obtain steel slag powder.

[0088] (2) Water and steel slag powder are mixed in a liquid-to-solid mass ratio of 1:1 to obtain a slurry, which is then added to a high-temperature and high-pressure reactor.

[0089] (3) Use CO2 to purge the high-temperature and high-pressure reactor to remove the air in the reactor and complete the gas tightness test.

[0090] (4) Set the reaction temperature to 4°C, turn on the heater, and after the reactor temperature reaches the set temperature, turn on the power of the CO2 pump to increase the mineralization pressure to the predetermined pressure value of 0.85 MPa.

[0091] (5) After the reaction time reaches 60 min, the gas in the autoclave is released and the temperature is lowered to room temperature.

[0092] (6) flushing the autoclave with water and discharging the reaction mixture through the bottom discharge valve to obtain a mixed material.

[0093] (7) The obtained mixture is separated into water and carbonation product through a suction filtration device, and the separated water is recycled.

[0094] (8) The carbonation product is dried (dried at 100°C for 1.5 hours) to obtain a carbon-fixed product, which can be used as a building material.

[0095] The carbon fixation rate of this comparative example is 5.6%, calculated from the ratio of the mass of the carbon fixation product to the mass of the steel slag before mineralization. Based on this, it can be seen that in this comparative example, 1 ton of steel slag powder can fix 56 kg of CO2.

[0096] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for supercritical carbon dioxide fixation using steel slag semi-dry process, characterized in that: The following steps are involved: The steel slag is mixed with water to obtain a slurry, which is sent to a reactor and CO2 is introduced. A mineralization reaction is carried out under the supercritical state of CO2 to obtain a carbonation product, thus completing the fixation of carbon dioxide.

2. The method according to claim 1, characterized in that The mass ratio of water to steel slag is 0.2-2:

1.

3. The method according to claim 1, characterized in that The steel slag is crushed to 100-200 mesh.

4. The method according to claim 1, wherein The CO2 pressure during the mineralization reaction is 7.4-10 MPa.

5. The method according to claim 1, wherein The temperature of the mineralization reaction is 40-80°C.

6. The method according to claim 1, wherein The mineralization reaction time is 60-120 minutes.

7. The method according to claim 1, characterized in that After the mineralization reaction, the method further comprises the step of drying the carbonation product.

8. The method according to claim 7, characterized in that The drying temperature is 80-100° C. and the drying time is 1.5 h.