Method and system for absorbing carbon dioxide using steel slag tailings

Abstract

The application provides a method and system for absorbing carbon dioxide by using steel slag tailings, and relates to the field of steelmaking solid waste treatment.The method for absorbing carbon dioxide by using steel slag tailings comprises the following steps: activation treatment, first-stage continuous carbonation reaction and second-stage continuous carbonation reaction.The method and system for absorbing carbon dioxide by using steel slag tailings can overcome the defects of low treatment efficiency, complex pretreatment and poor raw material adaptability of the existing process under the premise of large-scale industrialized treatment, and effectively realize continuous and stable treatment of steel slag on carbon dioxide.

Description

Technical Field

[0001] This invention relates to the field of steelmaking solid waste treatment, and in particular to a method and system for absorbing carbon dioxide using steel slag tailings. Background Technology

[0002] Steel slag, a solid waste byproduct of the steelmaking process (such as converter slag, electric furnace slag, foundry residue, and underflow slag), generates a huge annual emission, and its resource utilization has always been a challenge for the industry. Chemically, steel slag is rich in alkaline metal oxides, with CaO accounting for approximately 40-60 wt% and MgO for approximately 3-10 wt%. These components endow steel slag with high alkalinity and reactivity, theoretically enabling it to convert CO2 into stable carbonate minerals through mineral carbonation reactions, thereby achieving CO2 fixation and resource utilization. This not only reduces carbon emissions but also synergistically promotes solid waste resource utilization, offering the dual environmental benefits of "treating waste with waste."

[0003] However, despite the promising potential of steel slag carbon capture and mineralization technology, the current comprehensive utilization rate of steel slag is only 25%, and the following technical problems exist in the industrialization process:

[0004] 1. Low processing efficiency: Although the content of alkaline components in steel slag is relatively high, the reaction rate of its direct contact with CO2 is slow, the reaction cycle is long, the process continuity is poor, and the overall absorption and conversion rate of CO2 is less than 30%, which is difficult to meet the needs of large-scale industrial processing.

[0005] 2. Complex pretreatment: To improve the reactivity of steel slag with CO2, it is necessary to perform high-temperature and high-pressure thermal activation treatment (such as melting, hot quenching, etc.) or chemical activation treatment on the steel slag. Not only is the pretreatment process long, energy-intensive, and costly, but it may also cause a large amount of indirect carbon emissions during the pretreatment process, weakening the emission reduction effect of carbon capture and directly limiting large-scale application.

[0006] 3. Poor raw material compatibility: The composition of steel slag from different sources fluctuates greatly. Existing processes cannot effectively adapt to various steel slag raw materials, cannot accurately control the reaction process, and the quality of the calcium carbonate product obtained from the treatment is unstable. This directly leads to the inability to achieve continuous and stable large-scale processing, affecting resource utilization.

[0007] Based on this, a method and system for absorbing carbon dioxide using steel slag tailings are provided. While overcoming the above-mentioned defects, this method effectively achieves continuous and stable treatment of carbon dioxide by steel slag. It has important technical significance and research value for the comprehensive utilization of steel solid waste resources and carbon capture and storage (CCUS). Summary of the Invention

[0008] To address the technical problems existing in the prior art, this invention provides a method and system for absorbing carbon dioxide using steel slag tailings. Under the premise of large-scale industrial processing, it can overcome the defects of existing processes such as low processing efficiency, complex pretreatment, and poor raw material compatibility, and effectively achieve continuous and stable treatment of carbon dioxide by steel slag.

[0009] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0010] A method for absorbing carbon dioxide using steel slag tailings includes the following steps: activation treatment, primary continuous carbonation reaction, and secondary continuous carbonation reaction.

[0011] The activation treatment method is to perform hydrothermal activation or grinding activation on the crushed steel slag material to prepare a steel slag activation solution with a steel slag content of 5-6 wt%.

[0012] The method for the first-stage continuous carbonation reaction is as follows: steel slag activation liquid is continuously introduced into the first-stage fluidized reactor by top spray feeding. Under vortex stirring conditions, carbon dioxide-containing flue gas is continuously introduced below the liquid surface of the first-stage fluidized reactor. The carbon dioxide-containing flue gas is in continuous contact with the steel slag activation liquid to carry out the first-stage continuous carbonation reaction, continuously generating calcium carbonate / steel slag composite particles. The calcium carbonate / steel slag composite particles float up with the liquid and overflow into the second-stage fluidized reactor.

[0013] The method for the secondary continuous carbonation reaction is as follows: the secondary fluidized reactor continuously receives a liquid containing calcium carbonate / steel slag composite particles; under eddy current stirring conditions, the residual flue gas after the primary continuous carbonation reaction is bubbled to below the liquid surface of the secondary fluidized reactor, and the secondary continuous carbonation reaction is carried out in continuous contact; the precipitate at the bottom of the secondary fluidized reactor is collected periodically, and after dehydration and drying, calcium carbonate product is obtained.

[0014] Furthermore, the steel slag crushed material is obtained by crushing steel slag with a CaO content ≥40% to a particle size ≤5mm;

[0015] The steel slag is at least one of the following: converter slag, electric furnace slag, casting residue slag, and under-furnace slag.

[0016] Furthermore, in the activation treatment, the hydrothermal activation method involves immersing the crushed steel slag material in deionized water, heating it to 120-180°C in a closed environment, and stirring for 2-3 hours to obtain an activated steel slag solution.

[0017] Furthermore, in the activation treatment, the grinding activation method involves mechanically grinding the crushed steel slag material until the specific surface area of ​​the steel slag powder is ≥500m². 2Steel slag powder is obtained by dispersing the steel slag powder in deionized water to obtain steel slag activation solution. The powder has a particle size of ≥90% of 40μm and a particle size of ≤40μm.

[0018] Preferably, in the first-stage continuous carbonation reaction, the rate at which the steel slag activation liquid is continuously introduced into the first-stage fluidized reactor is controlled to be 16-20 L / min;

[0019] The rate at which carbon dioxide-containing flue gas is continuously introduced into the primary fluidized reactor is controlled to be 1-10 L / min;

[0020] The volume concentration of carbon dioxide in the carbon dioxide-containing flue gas is 10-30%.

[0021] Preferably, in the first-stage continuous carbonation reaction, the reaction temperature is controlled at 60-90℃ and the vortex stirring rate is 100-500 rpm;

[0022] In the two-stage continuous carbonation reaction, the vortex stirring speed is controlled at 100-500 rpm.

[0023] Preferably, in the primary continuous carbonation reaction, the residence time of the steel slag activation liquid in the primary fluidized reactor is 1-4 hours;

[0024] In the two-stage continuous carbonation reaction, the residence time of the feed liquid containing calcium carbonate / steel slag composite particles in the two-stage fluidized reactor is 1-3 hours.

[0025] A system for implementing the aforementioned method includes: a raw material activation module, a primary continuous carbonation module, a secondary continuous carbonation module, and a post-processing module;

[0026] The primary continuous carbonation module includes: a primary fluidized bed reactor;

[0027] The primary fluidized reactor is equipped with a spray pipe at the top to continuously spray the steel slag activation solution into the primary fluidized reactor; the primary fluidized reactor is equipped with an overflow port at the top, which is connected to the feed inlet pipe of the secondary fluidized reactor of the secondary continuous carbonation module, so that the liquid containing calcium carbonate / steel slag composite particles can continuously overflow into the secondary fluidized reactor.

[0028] A separator is installed in the lower part of the primary fluidized reactor to separate the calcium carbonate / steel slag composite particles from the large-diameter impurity particles in the feed liquid; a first gas distributor is installed below the separator and is connected to a flue gas source to introduce carbon dioxide-containing flue gas into the steel slag activation liquid; a first vortex stirrer is installed below the first gas distributor to continuously stir the vortex during the primary continuous carbonation reaction.

[0029] Furthermore, the secondary continuous carbonation module includes: a secondary fluidized bed reactor;

[0030] The secondary fluidized reactor is equipped with an air inlet pipe at the top so that the residual flue gas after the primary continuous carbonation reaction can enter the secondary fluidized reactor.

[0031] A second gas distributor is provided in the middle of the secondary fluidized reactor to bubble the remaining flue gas below the liquid surface containing calcium carbonate / steel slag composite particles; a second vortex agitator is provided below the second gas distributor to continuously stir the liquid during the secondary continuous carbonation reaction.

[0032] Furthermore, the raw material activation module includes: a preparation tank and a slurry pump; the preparation tank is used to heat the crushed steel slag and deionized water for hydrothermal activation, or to mix the mechanically ground steel slag powder and deionized water evenly to prepare a steel slag activation solution; the outlet of the preparation tank is connected to the inlet pipe of the primary fluidized reactor via the slurry pump, so as to continuously introduce the steel slag activation solution into the primary fluidized reactor;

[0033] The post-processing module includes: a dewatering pump and a plate and frame filter press; the lower outlet of the secondary fluidized reactor is connected to the inlet pipe of the plate and frame filter press via the dewatering pump, so as to introduce the sediment at the bottom of the secondary fluidized reactor into the plate and frame filter press for dewatering.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] (1) The method and system for absorbing carbon dioxide using steel slag tailings of the present invention involves crushing and activating the steel slag tailings to prepare a steel slag activated liquid. Under vortex stirring conditions, the liquid undergoes a first-stage continuous carbonation reaction and a second-stage continuous carbonation reaction in a first-stage fluidized reactor and a second-stage fluidized reactor. The carbon dioxide-containing flue gas continuously and efficiently contacts and reacts with the steel slag to produce steel slag particles coated with calcium carbonate (i.e., calcium carbonate products with a purity ≥ 90 wt%). The aforementioned technical means work together synergistically to achieve a high contact reaction rate between the steel slag tailings and carbon dioxide in the flue gas. The process exhibits good continuity, with a total carbon dioxide absorption rate (i.e., carbon dioxide fixation rate) of ≥75% for flue gas. It can effectively absorb and fix carbon dioxide in flue gas using steel slag tailings, achieving a carbon dioxide absorption rate more than twice that of traditional static processes. Simultaneously, it can utilize waste heat from steelmaking or calcination for heating during the treatment process, eliminating the need for additional energy consumption and avoiding high-temperature, high-pressure activation or chemical activation of steel slag. It also demonstrates good adaptability to steel slag and flue gas from different sources, enabling continuous and stable treatment of carbon dioxide by steel slag under large-scale industrial conditions.

[0036] (2) The method and system for absorbing carbon dioxide using steel slag tailings of the present invention can process approximately 1 m³ per hour. 3 The activated steel slag solution (steel slag concentration 5-6wt%) can generate 0.4-0.6 tons of calcium carbonate product per ton of steel slag, and the purity of the obtained calcium carbonate product is ≥90wt%, with the remainder being steel slag and trace impurities. It meets the building material standard requirements of GB / T 30190-2013 "Limestone Powder Concrete" and can be used directly as a building material or as a soil conditioner for soil improvement.

[0037] (3) The method of absorbing carbon dioxide using steel slag tailings of the present invention has a simple process flow, mild reaction conditions, easy process control, low requirements for supporting equipment, and is conducive to large-scale continuous industrial processing. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of a system for absorbing carbon dioxide using steel slag tailings, according to an embodiment of the present invention.

[0039] In the figure, 1-preparation tank; 2-slurry pump; 3-first-stage fluidized bed reactor; 4-spray pipe; 5-separator; 6-first gas distributor; 7-first vortex agitator; 8-second-stage fluidized bed reactor; 9-second gas distributor; 10-second vortex agitator; 11-dehydration pump; 12-plate and frame filter press. Detailed Implementation

[0040] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described. It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0041] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, "first," "second," etc., are used to distinguish similar objects and are not used to describe a particular order or sequence. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0042] This invention provides a method for absorbing carbon dioxide using steel slag tailings, comprising the following steps: raw material processing, activation treatment, primary continuous carbonation reaction, and secondary continuous carbonation reaction.

[0043] The raw material processing method is to crush the steel slag to a particle size of ≤5mm to obtain crushed steel slag material for later use.

[0044] In the raw material processing, the steel slag is the tailings generated during the steelmaking process, specifically at least one of the following: converter slag, electric furnace slag, casting residue, and underflow slag; preferably, the steel slag has a CaO content of ≥40%.

[0045] The activation treatment is performed by hydrothermal activation or grinding activation, with hydrothermal activation being preferred.

[0046] In this embodiment of the invention, the hydrothermal activation method is as follows: steel slag crushed material is put into a preparation tank 1 containing deionized water to prepare a steel slag crushed material dispersion with a steel slag content of 5-6 wt%. After sealing the preparation tank 1, the stirring speed of the preparation tank 1 is controlled at 80-100 rpm, and the mixture is stirred and heated (steam heating or electric heating) to 120-180℃. The mixture is kept at this temperature and stirred for 2-3 hours to complete the hydrothermal activation and obtain the steel slag activated liquid.

[0047] In this embodiment of the invention, the grinding and activation method involves mechanically grinding the crushed steel slag until the specific surface area of ​​the steel slag powder is ≥500 m². 2 Steel slag powder is obtained by mixing steel slag powder with a particle size of ≥90% of 40μm or less per kg of water. Then, the steel slag powder is added to deionized water, and the content of steel slag powder is controlled at 5-6wt%. The mixture is then stirred evenly to obtain steel slag activation solution.

[0048] The method for the first-stage continuous carbonation reaction is as follows: steel slag activation liquid is continuously pumped into the first-stage fluidized reactor 3 at a feed rate of 16-20 L / min via top spray feeding. The material temperature in the first-stage fluidized reactor 3 is controlled at 60-90℃. Under vortex stirring conditions of 100-500 rpm (preferably 200-400 rpm), carbon dioxide-containing flue gas (carbon dioxide volume concentration of 10-30%) is continuously introduced into the first gas distributor 6 at an inlet rate of 1-10 L / min (preferably 5-9 L / min) below the liquid surface of the steel slag activation liquid in the first-stage fluidized reactor 3. The carbon dioxide-containing flue gas and the steel slag activation liquid continuously contact in countercurrent to carry out the first-stage continuous carbonation reaction, generating calcium carbonate / steel slag composite particles (i.e., steel slag particles with newly generated calcium carbonate crystals coated on the surface).

[0049] In the first-stage continuous carbonation reaction, the flue gas containing carbon dioxide can be steelmaking flue gas, lime kiln flue gas, sintering machine flue gas, etc. There is no restriction on the specific source of the flue gas. Flue gas with a carbon dioxide volume concentration of 10-30% can be treated. If the carbon dioxide concentration in the flue gas does not meet the standard, it can be adjusted to 10-30% by concentration or dilution before being fed into the first-stage fluidized reactor 3 for treatment.

[0050] In the primary continuous carbonation reaction, calcium on the surface of steel slag reacts with carbon dioxide to form calcium carbonate. During the reaction, the original structure of the steel slag changes, and the continuously generated calcium carbonate coats the surface of the steel slag to form calcium carbonate / steel slag composite particles. These particles are then separated from large-diameter impurities in the feed liquid by a separator 5 (with a sieve plate of 100-120 mesh) installed in the primary fluidized bed reactor 3. The calcium carbonate / steel slag composite particles are then separated by the flotation effect of flue gas continuously introduced through a gas distributor installed below the separator 5, and float up with the feed liquid to the secondary fluidized bed reactor 8 for subsequent secondary continuous carbonation reactions. Unreacted large-diameter impurities (other substances that have detached from calcium) in the feed liquid are deposited at the bottom of the primary fluidized bed reactor under gravity and periodically discharged.

[0051] During the first-stage continuous carbonation reaction, vortex stirring can break the carbon dioxide-containing flue gas introduced by the gas distributor into smaller bubbles, which is conducive to the continuous gas-liquid contact reaction and gas flotation separation. The remaining flue gas after the first-stage continuous carbonation reaction is collected at the top of the first-stage fluidized bed reactor and continuously introduced into the second-stage fluidized bed reactor through pipeline for subsequent second-stage continuous carbonation reaction.

[0052] In the first-stage continuous carbonation reaction process, the residence time of the steel slag activation liquid in the first-stage fluidized reactor 3 is 1-4 hours.

[0053] The method of the secondary continuous carbonation reaction is as follows: the secondary fluidized reactor 8 continuously receives the feed liquid containing calcium carbonate / steel slag composite particles, while the residual flue gas after the primary continuous carbonation reaction is bubbled through the second gas distributor 9 to below the surface of the feed liquid containing calcium carbonate / steel slag composite particles, and continuously contactes the feed liquid to carry out the secondary continuous carbonation reaction, further generating calcium carbonate. As the calcium carbonate crystals on the surface of the composite particles gradually increase in size, they settle to the bottom of the secondary fluidized reactor 8 under the action of gravity. They are periodically discharged to the plate and frame filter press 12 through the dewatering pump 11 for filter dewatering treatment, and then dried to obtain a calcium carbonate product with a purity ≥90wt% (the remainder is steel slag and its trace impurities).

[0054] In the two-stage continuous carbonation reaction process, the vortex stirring speed is controlled at 100-500 rpm (preferably 200-400 rpm), and the residence time of the liquid containing calcium carbonate / steel slag composite particles in the two-stage fluidized reactor 8 is 1-3 hours. The vortex stirring can break the flue gas introduced by the gas distributor into smaller bubbles, which is beneficial to the gas-liquid contact reaction.

[0055] In the two-stage continuous carbonation process, part of the residual flue gas after the two-stage continuous carbonation reaction is recycled to the first-stage fluidized reactor 3 as a supplement to the carbon dioxide-containing flue gas, and then carried out the first-stage continuous carbonation reaction again; the other part can be directly discharged into the air, or collected into the gas storage device after water removal and demisting, and then concentrated and carried out the first-stage continuous carbonation reaction and the second-stage continuous carbonation reaction again.

[0056] like Figure 1 As shown, this embodiment of the invention also provides a system for absorbing carbon dioxide using steel slag tailings to achieve the aforementioned method. The system includes: a raw material activation module, a primary continuous carbonation module, a secondary continuous carbonation module, and a post-treatment module.

[0057] The raw material activation module includes a preparation tank 1 and a slurry pump 2. The preparation tank 1 is equipped with a feeding unit, a heating unit, and a stirring unit. The feeding unit is used to introduce crushed steel slag and deionized water into the preparation tank 1 for hydrothermal activation treatment, or to introduce mechanically ground steel slag powder and deionized water into the preparation tank 1 to prepare a steel slag activation solution. The heating unit is a heat transfer coil installed on the preparation tank 1 to heat and maintain the temperature of the materials in the preparation tank 1 using waste heat steam or electric heating. The stirring unit includes a stirring motor and a stirring paddle to stir the materials in the preparation tank 1. The outlet of the preparation tank 1 is connected to the inlet of the slurry pump 2, and the outlet of the slurry pump 2 is connected to the inlet of the primary fluidized reactor 3, so that the steel slag activation solution is continuously pumped into the primary fluidized reactor 3 of the primary continuous carbonation module for top spraying.

[0058] The primary continuous carbonation module includes: a primary fluidized bed reactor 3. A spray pipe 4 is installed at the top of the primary fluidized bed reactor 3 to continuously spray the steel slag activation liquid into the primary fluidized bed reactor 3; an overflow port is installed at the top of the primary fluidized bed reactor 3, which is connected to the feed inlet pipe of the secondary fluidized bed reactor 8 of the secondary continuous carbonation module, so that the liquid containing calcium carbonate / steel slag composite particles continuously overflows into the secondary fluidized bed reactor 8; a separator 5 is installed in the lower part of the primary fluidized bed reactor 3, using a sieve plate with a pore size of 100-120 mesh, to separate the calcium carbonate / steel slag composite particles from large-diameter impurities in the liquid; a first gas distributor 6 is installed below the separator 5, connected to a flue gas source, to evenly distribute the carbon dioxide-containing flue gas into the steel slag activation liquid of the primary fluidized bed reactor 3; a first vortex agitator 7 is installed below the first gas distributor 6 to continuously perform vortex stirring during the primary continuous carbonation reaction.

[0059] The secondary continuous carbonation module includes a secondary fluidized bed reactor 8. An inlet pipe is provided at the top of the secondary fluidized bed reactor 8 to allow the residual flue gas from the primary continuous carbonation reaction to enter the secondary fluidized bed reactor 8. A second gas distributor 9 is provided in the middle of the secondary fluidized bed reactor 8 to bubble the residual flue gas below the surface of the liquid containing calcium carbonate / steel slag composite particles. A second vortex agitator 10 is provided below the second gas distributor 9 to continuously agitate the liquid during the secondary continuous carbonation reaction. The lower outlet of the secondary fluidized bed reactor 8 is connected to the inlet pipe of the dewatering pump 11 of the post-treatment module to discharge the precipitated calcium carbonate / steel slag composite particles in the secondary fluidized bed reactor 8 to the post-treatment module for processing.

[0060] The post-processing module includes a dewatering pump 11 and a plate and frame filter press 12. The outlet of the dewatering pump 11 is connected to the inlet of the plate and frame filter press 12 so as to introduce the calcium carbonate / steel slag composite particles precipitated in the secondary fluidized reactor 8 into the plate and frame filter press 12 for filter pressing.

[0061] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described below in conjunction with some specific embodiments.

[0062] Example 1

[0063] This embodiment provides a method for absorbing carbon dioxide using steel slag tailings. The aforementioned system is used to treat steel slag and carbon dioxide-containing flue gas. The specific method is as follows:

[0064] 1. Raw material processing

[0065] The converter slag with a CaO content of 50wt% was crushed to a particle size of 3mm to obtain steel slag crushed material, which was then put into use.

[0066] 2. Activation treatment

[0067] The steel slag crushed material was treated by hydrothermal activation. Specifically, the steel slag crushed material was put into a preparation tank 1 containing deionized water to prepare a steel slag crushed material dispersion with a steel slag content of 5wt%. After sealing the preparation tank 1, the stirring speed was controlled at 100rpm. Waste heat steam from steelmaking was used as the heat source to stir and heat to 150℃, and the mixture was kept at this temperature and stirred for 3 hours to complete the hydrothermal activation and obtain the activated steel slag liquid.

[0068] 3. First-order continuous carbonation reaction

[0069] The steel slag activation solution was continuously pumped into the primary fluidized reactor 3 (effective volume 4m³) at a feed rate of 16.5 L / min via top spray feeding. 3Inside the primary fluidized bed reactor 3, the material temperature is controlled at 80℃. Under vortex stirring at 300 rpm, carbon dioxide-containing flue gas is continuously introduced into the primary fluidized bed reactor 3 through the first gas distributor 6 at an inlet rate of 6 L / min, below the liquid surface of the steel slag activation liquid. The carbon dioxide-containing flue gas and the steel slag activation liquid continuously contact in countercurrent to carry out a primary continuous carbonation reaction, generating calcium carbonate / steel slag composite particles. After being separated from the impurity particles in the liquid by the separator 5 (with a 100-mesh sieve plate), the calcium carbonate / steel slag composite particles float up with the liquid and overflow into the secondary fluidized bed reactor 8 under the air flotation separation effect of the continuously introduced flue gas to carry out the subsequent secondary continuous carbonation reaction. Unreacted large-diameter impurity particles in the liquid are deposited at the bottom of the primary fluidized bed reactor under gravity and are periodically discharged.

[0070] The flue gas containing carbon dioxide is steelmaking flue gas, with a carbon dioxide volume concentration of 20%.

[0071] The residence time of the steel slag activation solution in the primary fluidized reactor 3 is 2.5 h.

[0072] The carbon dioxide concentration at the top outlet of the first-stage fluidized reactor 3 was detected by a gas analyzer. The carbon dioxide concentration in the residual flue gas after the first-stage continuous carbonation reaction was found to be 8.9%, which means that the carbon dioxide absorption rate of the first-stage continuous carbonation reaction was 55.5%.

[0073] 4. Second-order continuous carbonation reaction

[0074] Secondary fluidized reactor 8 (effective volume 2m³) 3 The reactor continuously receives a liquid containing calcium carbonate / steel slag composite particles. Simultaneously, the residual flue gas from the primary continuous carbonation reaction is bubbled through a second gas distributor 9 to below the surface of the liquid containing the calcium carbonate / steel slag composite particles, maintaining continuous contact with the liquid for a secondary continuous carbonation reaction. As the calcium carbonate crystals on the surface of the composite particles gradually increase in size, they settle to the bottom of the secondary fluidized bed reactor 8 under gravity. The sediment is then discharged through a dewatering pump 11 to a plate and frame filter press 12 for dewatering and drying to obtain the calcium carbonate product. Testing shows that the purity of the calcium carbonate product is 91.3 wt%, with the remainder being steel slag and trace impurities. This meets the national standard GB / T 30190-2013 "Limestone Powder Concrete" and can be used directly as a building material or soil conditioner.

[0075] The eddy current stirring speed is controlled at 300 rpm, and the residence time of the liquid containing calcium carbonate / steel slag composite particles in the secondary fluidized reactor 8 is 1.5 h.

[0076] The carbon dioxide concentration at the top outlet of the secondary fluidized reactor 8 was detected by a gas analyzer. The carbon dioxide concentration in the remaining flue gas after the secondary continuous carbonation reaction was found to be 3.5%, which means that the absorption rate of carbon dioxide in the flue gas in this embodiment is 82.5%.

[0077] Example 2

[0078] This embodiment provides a method for absorbing carbon dioxide using steel slag tailings. The aforementioned system is used to treat steel slag and carbon dioxide-containing flue gas. The specific method is as follows:

[0079] 1. Raw material processing

[0080] Electric furnace slag with a CaO content of 48wt% was crushed to a particle size of 4mm to obtain steel slag crushed material, which was then put into use.

[0081] 2. Activation treatment

[0082] The steel slag crushed material is treated by grinding and activation. Specifically, the steel slag crushed material is mechanically ground until the specific surface area of ​​the steel slag powder is 550 m². 2 The steel slag powder is obtained by mixing steel slag powder with a particle size of 40 μm or less, and 90% of the powder has a particle size of 40 μm or less. The steel slag powder is then added to deionized water, and the steel slag powder content is controlled at 5 wt%. The mixture is then stirred evenly to obtain steel slag activation solution.

[0083] 3. First-order continuous carbonation reaction

[0084] The steel slag activation solution was continuously pumped into the primary fluidized reactor 3 (effective volume 4m³) at a feed rate of 16.7 L / min via top spray feeding. 3 Inside the primary fluidized bed reactor 3, the material temperature is controlled at 70℃. Under vortex stirring at 350 rpm, carbon dioxide-containing flue gas is continuously introduced into the primary fluidized bed reactor 3 through the first gas distributor 6 at an inlet rate of 7 L / min, below the liquid surface of the steel slag activation liquid. The carbon dioxide-containing flue gas and the steel slag activation liquid continuously contact in countercurrent to carry out a primary continuous carbonation reaction, generating calcium carbonate / steel slag composite particles. After being separated from the impurity particles in the liquid by the separator 5 (with a 100-mesh sieve plate), the calcium carbonate / steel slag composite particles float up with the liquid and overflow into the secondary fluidized bed reactor 8 under the air flotation separation effect of the continuously introduced flue gas to carry out the subsequent secondary continuous carbonation reaction. Unreacted large-diameter impurity particles in the liquid are deposited at the bottom of the primary fluidized bed reactor under gravity and are periodically discharged.

[0085] The flue gas containing carbon dioxide is steelmaking flue gas, with a carbon dioxide volume concentration of 15%.

[0086] The residence time of the steel slag activation solution in the primary fluidized reactor 3 is 2 hours.

[0087] The carbon dioxide concentration at the top outlet of the first-stage fluidized reactor 3 was detected by a gas analyzer. The carbon dioxide concentration in the residual flue gas after the first-stage continuous carbonation reaction was found to be 6.9%, which means that the carbon dioxide absorption rate of the first-stage continuous carbonation reaction was 54%.

[0088] 4. Second-order continuous carbonation reaction

[0089] Secondary fluidized reactor 8 (effective volume 2m³) 3 The reactor continuously receives a liquid containing calcium carbonate / steel slag composite particles. Simultaneously, the residual flue gas from the primary continuous carbonation reaction is bubbled through a second gas distributor 9 to below the surface of the liquid containing the calcium carbonate / steel slag composite particles, maintaining continuous contact with the liquid for a secondary continuous carbonation reaction. As the calcium carbonate crystals on the surface of the composite particles gradually increase in size, they settle to the bottom of the secondary fluidized bed reactor 8 under gravity. The sediment is then discharged through a dewatering pump 11 to a plate and frame filter press 12 for dewatering and drying to obtain the calcium carbonate product. Testing shows that the purity of the calcium carbonate product is 88.4 wt%, with the remainder being steel slag and trace impurities. This meets the national standard GB / T 30190-2013 "Limestone Powder Concrete" and can be used directly as a building material or soil conditioner.

[0090] The vortex stirring speed was controlled at 350 rpm, and the residence time of the liquid containing calcium carbonate / steel slag composite particles in the secondary fluidized reactor 8 was 1 hour.

[0091] The carbon dioxide concentration at the top outlet of the secondary fluidized reactor 8 was detected by a gas analyzer. The carbon dioxide concentration in the remaining flue gas after the secondary continuous carbonation reaction was found to be 3.3%, which means that the absorption rate of carbon dioxide in the flue gas in this embodiment is 78.0%.

[0092] Example 3

[0093] This embodiment provides a method for absorbing carbon dioxide using steel slag tailings. The aforementioned system is used to treat steel slag and carbon dioxide-containing flue gas. The specific method is as follows:

[0094] 1. Raw material processing

[0095] The foundry residue with a CaO content of 52wt% was crushed to a particle size of 2mm to obtain steel slag crushed material, which was then put into use.

[0096] 2. Activation treatment

[0097] The steel slag crushed material was treated by hydrothermal activation. Specifically, the steel slag crushed material was put into a preparation tank 1 containing deionized water to prepare a steel slag crushed material dispersion with a steel slag content of 5wt%. After sealing the preparation tank 1, the stirring speed was controlled at 90rpm. The waste heat steam from lime kiln calcination was used as the heat source to stir and heat to 130℃, and the temperature was kept and stirred for 4 hours to complete the hydrothermal activation and obtain the steel slag activated liquid.

[0098] 3. First-order continuous carbonation reaction

[0099] The steel slag activation solution was continuously pumped into the primary fluidized reactor 3 (effective volume 4m³) at a feed rate of 16.7 L / min via top spray feeding. 3 Inside the primary fluidized bed reactor 3, the material temperature is controlled at 90℃. Under vortex stirring at 250 rpm, carbon dioxide-containing flue gas is continuously introduced into the primary fluidized bed reactor 3 through the first gas distributor 6 at an inlet rate of 5 L / min, below the liquid surface of the steel slag activation liquid. The carbon dioxide-containing flue gas and the steel slag activation liquid continuously contact in countercurrent to carry out a primary continuous carbonation reaction, generating calcium carbonate / steel slag composite particles. After being separated from the impurity particles in the liquid by the separator 5 (with a 100-mesh sieve plate), the calcium carbonate / steel slag composite particles float up with the liquid and overflow into the secondary fluidized bed reactor 8 under the air flotation separation effect of the continuously introduced flue gas to carry out the subsequent secondary continuous carbonation reaction. Unreacted large-diameter impurity particles in the liquid are deposited at the bottom of the primary fluidized bed reactor under gravity and are periodically discharged.

[0100] The flue gas containing carbon dioxide is lime kiln flue gas, with a carbon dioxide volume concentration of 25%.

[0101] The residence time of the steel slag activation solution in the primary fluidized reactor 3 is 3 hours.

[0102] The carbon dioxide concentration at the top outlet of the first-stage fluidized reactor 3 was detected by a gas analyzer. The carbon dioxide concentration in the residual flue gas after the first-stage continuous carbonation reaction was found to be 10.5%, which means that the carbon dioxide absorption rate of the first-stage continuous carbonation reaction was 58%.

[0103] 4. Second-order continuous carbonation reaction

[0104] Secondary fluidized reactor 8 (effective volume 2m³) 3The reactor continuously receives a liquid containing calcium carbonate / steel slag composite particles. Simultaneously, the residual flue gas from the primary continuous carbonation reaction is bubbled through a second gas distributor 9 to below the surface of the liquid containing the calcium carbonate / steel slag composite particles, maintaining continuous contact with the liquid for a secondary continuous carbonation reaction. As the calcium carbonate crystals on the surface of the composite particles gradually increase in size, they settle to the bottom of the secondary fluidized bed reactor 8 under gravity. The sediment is then discharged through a dewatering pump 11 to a plate and frame filter press 12 for dewatering and drying to obtain the calcium carbonate product. Testing shows that the purity of the calcium carbonate product is 92.3 wt%, with the remainder being steel slag and trace impurities. This meets the national standard GB / T 30190-2013 "Limestone Powder Concrete" and can be used directly as a building material or soil conditioner.

[0105] The eddy current stirring speed is controlled at 250 rpm, and the residence time of the liquid containing calcium carbonate / steel slag composite particles in the secondary fluidized reactor 8 is 2 hours.

[0106] The carbon dioxide concentration at the top outlet of the secondary fluidized reactor 8 was detected by a gas analyzer. The carbon dioxide concentration in the remaining flue gas after the secondary continuous carbonation reaction was found to be 3.7%, which means that the absorption rate of carbon dioxide in the flue gas in this embodiment is 85.2%.

[0107] Example 4

[0108] This embodiment provides a method for absorbing carbon dioxide using steel slag tailings. The aforementioned system is used to treat steel slag and carbon dioxide-containing flue gas. The specific method is as follows:

[0109] 1. Raw material processing

[0110] The underflow slag with a CaO content of 48wt% was crushed to a particle size of 5mm to obtain steel slag crushed material, which was then put into use.

[0111] 2. Activation treatment

[0112] The steel slag crushed material is treated by grinding and activation. Specifically, the steel slag crushed material will be mechanically ground until the specific surface area of ​​the steel slag powder is 600 m². 2 The steel slag powder is obtained by mixing steel slag powder with a particle size of 40 μm or less, and 90% of the powder has a particle size of 40 μm or less. The steel slag powder is then added to deionized water, and the steel slag powder content is controlled at 5 wt%. The mixture is then stirred evenly to obtain steel slag activation solution.

[0113] 3. First-order continuous carbonation reaction

[0114] The steel slag activation liquid is continuously pumped into the primary fluidized reactor 3 (effective volume 4m³) at a feed rate of 16 L / min via top spray feeding. 3Inside the primary fluidized bed reactor 3, the material temperature is controlled at 60℃. Under vortex stirring at 200 rpm, carbon dioxide-containing flue gas is continuously introduced into the primary fluidized bed reactor 3 through the first gas distributor 6 at an inlet rate of 7.6 L / min, below the liquid surface of the steel slag activation liquid. The carbon dioxide-containing flue gas and the steel slag activation liquid continuously contact in countercurrent to carry out a primary continuous carbonation reaction, generating calcium carbonate / steel slag composite particles. After being separated from the impurity particles in the liquid by the separator 5 (with a 100-mesh sieve), the calcium carbonate / steel slag composite particles float up with the liquid and overflow into the secondary fluidized bed reactor 8 under the air flotation separation effect of the continuously introduced flue gas to carry out the subsequent secondary continuous carbonation reaction. Unreacted large-diameter impurity particles in the liquid are deposited at the bottom of the primary fluidized bed reactor under gravity and are periodically discharged.

[0115] The flue gas containing carbon dioxide is steelmaking flue gas, with a carbon dioxide volume concentration of 12%.

[0116] The residence time of the steel slag activation solution in the primary fluidized reactor 3 is 1.25 h.

[0117] The carbon dioxide concentration at the top outlet of the first-stage fluidized reactor 3 was detected by a gas analyzer. The carbon dioxide concentration in the residual flue gas after the first-stage continuous carbonation reaction was found to be 5.8%, which means that the carbon dioxide absorption rate of the first-stage continuous carbonation reaction was 51.7%.

[0118] 4. Second-order continuous carbonation reaction

[0119] Secondary fluidized reactor 8 (effective volume 2m³) 3 The reactor continuously receives a liquid containing calcium carbonate / steel slag composite particles. Simultaneously, the residual flue gas from the primary continuous carbonation reaction is bubbled through a second gas distributor 9 to below the surface of the liquid containing the calcium carbonate / steel slag composite particles, maintaining continuous contact with the liquid for a secondary continuous carbonation reaction. As the calcium carbonate crystals on the surface of the composite particles gradually increase in size, they settle to the bottom of the secondary fluidized bed reactor 8 under gravity. The sediment is then discharged through a dewatering pump 11 to a plate and frame filter press 12 for dewatering and drying to obtain the calcium carbonate product. Testing shows that the purity of the calcium carbonate product is 85.7 wt%, with the remainder being steel slag and trace impurities. This meets the national standard GB / T 30190-2013 "Limestone Powder Concrete" and can be used directly as a building material or soil conditioner.

[0120] The eddy current stirring speed is controlled at 300 rpm, and the residence time of the liquid containing calcium carbonate / steel slag composite particles in the secondary fluidized reactor 8 is 1 hour.

[0121] The carbon dioxide concentration at the top outlet of the secondary fluidized reactor 8 was detected by a gas analyzer. The carbon dioxide concentration in the remaining flue gas after the secondary continuous carbonation reaction was found to be 3.0%, which means that the absorption rate of carbon dioxide in the flue gas in this embodiment is 75%.

[0122] As can be seen, the methods and systems for absorbing carbon dioxide using steel slag tailings in Examples 1-3 involve crushing and activating the steel slag tailings to produce an activated steel slag liquid. Under vortex stirring conditions, the liquid undergoes a first-stage continuous carbonation reaction and a second-stage continuous carbonation reaction in a primary fluidized bed reactor and a secondary fluidized bed reactor. This allows for continuous and efficient contact and reaction between the carbon dioxide-containing flue gas and the steel slag, producing steel slag particles coated with calcium carbonate (i.e., calcium carbonate products with a purity ≥90wt%). The aforementioned technical means work together synergistically, resulting in a high contact reaction rate between the steel slag tailings and carbon dioxide in the flue gas, good process continuity, and a high overall carbon dioxide absorption rate (i.e., carbon dioxide fixation). With an absorption rate of ≥75%, it can effectively absorb and fix carbon dioxide in flue gas using steel slag tailings, increasing the carbon dioxide absorption rate by more than 2 times compared to the traditional static process. Simultaneously, it can utilize waste heat from steelmaking or calcination during the treatment process, eliminating the need for additional energy consumption and avoiding high-temperature, high-pressure activation or chemical activation of the steel slag. It exhibits good adaptability to steel slag and flue gas from different sources, enabling continuous and stable carbon dioxide treatment of steel slag under large-scale industrial conditions. The resulting calcium carbonate product meets the building materials standard requirements of GB / T30190-2013 and can be used directly as a building material or as a soil conditioner for soil improvement.

[0123] Unless otherwise stated, all percentages used in this invention are mass percentages.

[0124] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for absorbing carbon dioxide using steel slag tailings, characterized in that, The process includes the following steps: activation treatment, primary continuous carbonation reaction, and secondary continuous carbonation reaction; The activation treatment method is to perform hydrothermal activation or grinding activation on the crushed steel slag material to prepare a steel slag activation solution with a steel slag content of 5-6 wt%. The hydrothermal activation method involves immersing crushed steel slag material in deionized water, heating it to 120-180°C in a closed environment, and stirring for 2-3 hours to obtain an activated steel slag solution. The grinding and activation method involves mechanically grinding the crushed steel slag material until the specific surface area of ​​the steel slag powder is ≥500 m². 2 Steel slag powder is obtained by dispersing the steel slag powder in deionized water to obtain steel slag activation solution. The powder has a particle size of ≥90% of 40μm and a particle size of ≤40μm. The method of the first-stage continuous carbonation reaction is as follows: the steel slag activation liquid is continuously introduced into the first-stage fluidized reactor (3) by top spray feeding. Under vortex stirring conditions, the flue gas containing carbon dioxide is continuously introduced into the first-stage fluidized reactor (3) below the liquid surface of the liquid. The flue gas containing carbon dioxide is in continuous contact with the steel slag activation liquid to carry out the first-stage continuous carbonation reaction and continuously generate calcium carbonate / steel slag composite particles. The calcium carbonate / steel slag composite particles are separated from the large-diameter impurity particles in the liquid by the separator (5) set in the lower part of the first-stage fluidized reactor (3). Through the air flotation separation effect of the continuously introduced flue gas, the calcium carbonate / steel slag composite particles float up with the liquid and overflow to the second-stage fluidized reactor (8). The method of the secondary continuous carbonation reaction is as follows: the secondary fluidized reactor (8) continuously receives the liquid containing calcium carbonate / steel slag composite particles. Under vortex stirring conditions, the residual flue gas after the primary continuous carbonation reaction is bubbled to below the liquid surface of the liquid in the secondary fluidized reactor (8) and continuously contacted to carry out the secondary continuous carbonation reaction. The precipitate at the bottom of the secondary fluidized reactor (8) is collected periodically, and after dehydration and drying, calcium carbonate product is obtained.

2. The method for absorbing carbon dioxide using steel slag tailings according to claim 1, characterized in that, The steel slag crushed material is obtained by crushing steel slag with a CaO content of ≥40% to a particle size of ≤5mm; The steel slag is at least one of the following: converter slag, electric furnace slag, casting residue slag, and under-furnace slag.

3. The method for absorbing carbon dioxide using steel slag tailings according to claim 1, characterized in that, In the first-stage continuous carbonation reaction, the rate at which the steel slag activation liquid is continuously introduced into the first-stage fluidized reactor (3) is controlled to be 16-20 L / min; The rate at which carbon dioxide-containing flue gas is continuously introduced into the primary fluidized reactor (3) is controlled to be 1-10 L / min; The volume concentration of carbon dioxide in the carbon dioxide-containing flue gas is 10-30%.

4. The method for absorbing carbon dioxide using steel slag tailings according to claim 1, characterized in that, In the first-stage continuous carbonation reaction, the reaction temperature is controlled at 60-90℃ and the vortex stirring speed is 100-500rpm. In the two-stage continuous carbonation reaction, the vortex stirring speed is controlled at 100-500 rpm.

5. The method for absorbing carbon dioxide using steel slag tailings according to claim 1, characterized in that, In the first-stage continuous carbonation reaction, the residence time of the steel slag activation liquid in the first-stage fluidized reactor (3) is 1-4 hours; In the secondary continuous carbonation reaction, the residence time of the liquid containing calcium carbonate / steel slag composite particles in the secondary fluidized reactor (8) is 1-3 hours.

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