Method for preparing aragonite-type calcium carbonate by fixing carbon dioxide with steel slag

Abstract

The application discloses a method for preparing aragonite type calcium carbonate by fixing carbon dioxide with steel slag, which comprises the following steps: (1) crushing and grinding the steel slag into steel slag powder, and then activating the steel slag powder in ultrasonic waves to obtain ultrasonic-activated steel slag powder; (2) mixing the ultrasonic-activated steel slag powder with water, adding pure acetic acid solvent to warm and acidify, and preparing acidified steel slag; (3) CO2 gas quenching the acidified steel slag, adding water to the acetic acid leaching solution and the steel slag powder in a mass ratio of 3-10:1, adjusting the pH of the leaching solution to 7-9, stopping the CO2 input after 10-90 min of stirring, and filtering to obtain calcium bicarbonate filtrate; and (4) crystallizing and filtering the calcium bicarbonate filtrate to obtain aragonite type calcium carbonate. The method can fix carbon dioxide in tail gas on site by using the waste steel slag stacked in a steel plant, achieves the effect of "waste treatment by waste", the leaching reagent can be recycled, and the method is economic and environment-friendly, and solves the technical problems of utilization of steel slag waste and carbon dioxide resources.

Description

Technical Field

[0001] This invention belongs to the technical field of waste resource utilization, greenhouse gas CO2 emission reduction and resource utilization, and specifically relates to a method for preparing aragonite-type calcium carbonate by fixing carbon dioxide in steel slag. Technical Background

[0002] With the rapid development of global industrialization, the greenhouse effect caused by carbon dioxide is intensifying. Therefore, the emission control concept of "carbon capture, utilization, and storage" (CCUS) has received significant attention. Steel slag, a bulk alkaline solid waste, mainly contains calcium components including calcium hydroxide, dicalcium silicate, tricalcium silicate, tetracalcium aluminoferrite, and tricalcium aluminate. It also contains highly carbonitriding reactive components such as free calcium oxide and magnesium oxide, which contribute to poor stability. These components can react rapidly with high concentrations of carbon dioxide, making them a suitable raw material for carbon dioxide capture.

[0003] Currently, common methods for solidifying carbon dioxide using steel slag include direct carbonation and indirect carbonation. Direct carbonation involves the direct reaction of steel slag with carbon dioxide, and is typically used in the production of building materials. Patent CN200710038385 discloses a method for carbonation treatment of steel slag, in which steel slag with a particle size ≤15mm reacts with CO2 gas for 2–12 hours in a fluidized bed reactor at 350–800℃, 0.1–3.6 atm, and a water vapor content of 5–25%. Although the direct carbonation method is simple, it usually requires high temperature and pressure, resulting in high energy consumption and a slow reaction time.

[0004] The indirect carbonation method first leaches calcium and magnesium ions from steel slag, then reacts them with carbon dioxide to produce carbonates. The resulting product has high purity and can be used to produce chemical raw materials. Currently, the preparation of aragonite-type calcium carbonate mainly includes the metathesis reaction method, urea hydrolysis method, calcium bicarbonate thermal decomposition method, and carbonation method. Compared with other methods, the carbonation method has advantages such as wide availability of raw materials, simple operation process, and low production cost. However, this method often requires the addition of a crystal form control agent to the system at the beginning of the carbonation reaction. Patent 201510176522.1 discloses a method for preparing high aspect ratio aragonite-type calcium carbonate whiskers. This method adds magnesium chloride as a crystal form control agent to a Ca(OH)2 suspension, and introduces a mixed gas of CO2 and N2 to synthesize high aspect ratio calcium carbonate whiskers in one step. Patent ZL201010280862.6 discloses a method for preparing high aspect ratio calcium carbonate whiskers. This method uses quicklime as raw material and magnesium chloride as a crystal form control agent. Calcium carbonate whiskers are prepared through a carbonation reaction with carbon dioxide. The mother liquor is then recycled to obtain a multi-stage grown high aspect ratio calcium carbonate whisker product. However, this method does not utilize steel slag waste as raw material, and the system requires the addition of a crystal form control agent, increasing costs and introducing impurities. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing aragonite-type calcium carbonate by fixing carbon dioxide in steel slag, which can effectively solve the problems of steel slag waste and large-scale carbon dioxide emissions.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for preparing aragonite-type calcium carbonate by fixing carbon dioxide in steel slag includes the following steps:

[0008] (1) The steel slag is crushed and ground into steel slag powder, and then placed in an ultrasonic wave to activate it, so as to obtain ultrasonically activated steel slag powder.

[0009] (2) The ultrasonically activated steel slag powder is mixed with water, pure acetic acid solvent is added and heated to acidify, thus producing acidified steel slag;

[0010] (3) The acidified steel slag is quenched with CO2 gas, water is added until the mass ratio of acetic acid leachate to steel slag powder is 3-10:1, the pH of the leachate is adjusted to 7-9, the CO2 is stopped after stirring for 10-90 minutes, and the calcium bicarbonate filtrate is obtained by filtration.

[0011] (4) Crystallize and filter the calcium bicarbonate filtrate to obtain aragonite-type calcium carbonate.

[0012] Furthermore, the main components and their mass percentages of the steel slag described in this invention are as follows: CaO: 40%–50%, MgO: 5%–15%, SiO2: 10%–20%, Al2O3: 1%–5%, FeO: 10%–20%, MnO: 1%–5%.

[0013] Furthermore, in step (1) of the present invention, the portion of the steel slag powder with a particle size of less than 74 μm accounts for 65% to 80% of the total mass, and the portion with a particle size between 74 and 150 μm accounts for 20% to 35% of the total mass.

[0014] Furthermore, the ultrasonic activation power in step (1) of the present invention is 500-800W, and the activation time is 20-60min.

[0015] Further, in step (2) of the present invention, the mass ratio of the steel slag powder to the total mass of the water and acetic acid solution is 1 to 3:1; the amount of water and pure acetic acid solvent is calculated based on the mass concentration of the acetic acid solution formed after mixing water and pure acetic acid solvent being 30 to 70%.

[0016] Furthermore, the pure acetic acid solvent in step (2) of the present invention has a mass concentration of 98% or higher.

[0017] Furthermore, the acidification temperature in step (2) of the present invention is 60-120°C, and the acidification time is 30-150 min.

[0018] Furthermore, in step (3) of the present invention, the CO2 gas quenching uses steel plant tail gas, the CO2 concentration in the steel plant tail gas is 10-50%, and the gas quenching pressure is 0.2-0.5 MPa.

[0019] Furthermore, the stirring rate in step (3) of the present invention is 200 to 500 rpm.

[0020] Furthermore, in step (3) of the present invention, the residence time of the heated acidified steel slag in air before CO2 gas quenching is less than 30s.

[0021] Furthermore, the stirring rate of the crystallization process in step (4) of the present invention is 200-600 rpm, and the pH is 9-11.

[0022] Furthermore, the filtrate produced by the crystallization and filtration process in step (4) of the present invention can be added to the acidified steel slag in step (2) and the CO2 quenched steel slag in step (3).

[0023] The aragonite-type calcium carbonate prepared by the method of the present invention has a content of more than 85% and a whiteness of more than 95.

[0024] This invention has the following advantages and positive effects:

[0025] (1) Ultrasonic activation of finely ground steel slag produces mechanical, thermal and activation effects, which improves the reactivity of steel slag and reduces the heat input in the subsequent heating and acidification steps. Pure acid acidification can expand the cracks in steel slag, allowing calcium in insoluble silicates to be fully released. The CO2 gas quenching method not only refines the steel slag particles, but also directly fixes CO2 in the steel slag, optimizing the carbon fixation step and improving the calcium leaching rate.

[0026] (2) Steel slag production sites are often sources of carbon dioxide release. On-site solidification of steel slag to treat carbon dioxide achieves the effect of "treating waste with waste and recycling", saving transportation costs while improving production efficiency. It has important research significance and application prospects. The combination of ultrasonic activation-pure acid acidification-CO2 gas quenching and cooling results in no wastewater generation, high product purity, simple operation, and environmental friendliness. It effectively solves the technical problems of steel slag waste and carbon dioxide resource utilization. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the method flow of the present invention.

[0028] Figure 2 The image shows the XRD pattern of the aragonite-type calcium carbonate prepared in Example 1.

[0029] Figure 3Microscopic image of aragonite-type calcium carbonate prepared in Example 1. Implementation

[0030] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. Example 1

[0031] The main components and mass percentages of the steel slag used in this embodiment are: CaO: 44%, MgO: 12%, SiO2: 13%, Al2O3: 3%, FeO: 12%, MnO: 4%.

[0032] The process flow for preparing aragonite-type calcium carbonate by fixing carbon dioxide in steel slag is as follows: Figure 1 Specifically, it includes the following steps:

[0033] (1) The steel slag is crushed and ground into steel slag powder, wherein the portion of the steel slag powder with a particle size of less than 74 μm accounts for 80% of the total mass and the portion with a particle size between 74 and 150 μm accounts for 20% of the total mass; the steel slag powder is placed in an ultrasonic wave with a power of 600W for 20 minutes to activate it and obtain ultrasonic steel slag powder.

[0034] (2) The ultrasonically treated steel slag powder is mixed with water, and then pure acetic acid solvent is added. The mixture is acidified at 90°C for 150 min to produce acidified steel slag. The mass ratio of the steel slag powder to the total mass of the water and acetic acid solution is 3:1. The amount of water and pure acetic acid solvent is calculated based on the mass concentration of the acetic acid solution formed after mixing water and pure acetic acid solvent being 30%. The mass concentration of the pure acetic acid solvent is 98%.

[0035] (3) The acidified steel slag was placed in the gas quenching chamber for CO2 gas quenching and rapid cooling. Water was added until the mass ratio of acetic acid leaching solution to steel slag powder was 3:1. The pH of the leaching solution was adjusted to 7. After stirring at a rate of 300 rpm for 90 min, the CO2 was stopped. The solution was filtered to obtain calcium bicarbonate filtrate and tailings. The CO2 gas quenching process used steel plant tail gas with a CO2 concentration of 50% and a quenching pressure of 0.2 MPa. The acidified steel slag was kept in the air for 27 s before CO2 gas quenching.

[0036] (4) Crystallize the calcium bicarbonate filtrate and filter it to obtain aragonite-type calcium carbonate and filtrate; the stirring rate during crystallization is 200 rpm and the pH is adjusted to 9; the filtrate produced after crystallization and filtration is added to acidified steel slag and CO2 gas quenched steel slag.

[0037] In this embodiment, the calcium leaching rate in the calcium bicarbonate filtrate was 90.42%. Using the same minerals and without ultrasonic activation, acidified steel slag was directly subjected to CO2 gas quenching and rapid cooling under identical conditions, resulting in a calcium leaching rate of 80.50%.

[0038] The aragonite-type calcium carbonate prepared in this embodiment has a content of 88% and a whiteness of 96%.

[0039] The XRD pattern of the aragonite-type calcium carbonate prepared in this embodiment is shown in the figure. Figure 2 See microscope image Figure 3 .Depend on Figure 2 It can be seen that the mineral phase composition is calcium carbonate, composed of... Figure 3 It can be seen that the mineral crystal form is aragonite, indicating that the product prepared by the technical solution of the present invention is aragonite-type calcium carbonate. Example 2

[0040] The main components and their mass percentages of the steel slag in this embodiment are CaO: 50%, MgO: 5%, SiO2: 20%, Al2O3: 1%, FeO: 10%, and MnO: 1%.

[0041] The method for preparing aragonite-type calcium carbonate by fixing carbon dioxide with steel slag is the same as in Example 1, except that:

[0042] (1) In steel slag powder, the portion with a particle size less than 74 μm accounts for 65% of the total mass, and the portion with a particle size between 74 and 150 μm accounts for 35% of the total mass; the ultrasonic activation power is 500 W and the activation time is 40 min;

[0043] (2) The mass ratio of steel slag powder to the total mass of water and acetic acid solution is 1:1; the amount of water and pure acetic acid solvent is calculated based on the mass concentration of the acetic acid solution formed after mixing water and pure acetic acid solvent being 70%; the acidification temperature is 60℃; the acidification time is 90min;

[0044] (3) Add water until the mass ratio of acetic acid leachate to steel slag powder is 6, adjust the pH of leachate to 8, stir for 60 min, stir at 200 rpm; CO2 quenching pressure is 0.5 MPa; CO2 gas concentration in tail gas is 10%; acidified steel slag stays in air for 28 s before CO2 quenching.

[0045] (4) The stirring rate during the crystallization process is 600 rpm, and the pH is adjusted to 11;

[0046] In this embodiment, the calcium leaching rate in the calcium bicarbonate filtrate was 92.15%. Using the same minerals and without ultrasonic activation, acidified steel slag was directly subjected to CO2 gas quenching under identical conditions, resulting in a calcium leaching rate of 82.67%.

[0047] The aragonite-type calcium carbonate prepared in this embodiment has a content of 85% and a whiteness of 95%. Example 3

[0048] The main components and their mass percentages of the steel slag in this embodiment are CaO: 40%, MgO: 15%, SiO2: 10%, Al2O3: 5%, FeO: 20%, and MnO: 5%.

[0049] The method for preparing aragonite-type calcium carbonate by fixing carbon dioxide with steel slag is the same as in Example 1, except that:

[0050] (1) In steel slag powder, the portion with a particle size less than 74 μm accounts for 78% of the total mass, and the portion with a particle size between 74 and 150 μm accounts for 22% of the total mass. ; Ultrasonic activation power 800W, activation time 60min;

[0051] (2) The ratio of the mass of steel slag powder to the total mass of water and acetic acid solution is 2:1; the amount of water and pure acetic acid solvent is calculated based on the mass concentration of the acetic acid solution formed after mixing water and pure acetic acid solvent being 50%; the acidification temperature is 120℃; the acidification time is 30min.

[0052] (3) Add water until the mass ratio of acetic acid leachate to steel slag powder is 10, adjust the pH of leachate to 9, stir for 10 min, and stir at 500 rpm; CO2 quenching pressure is 0.3 MPa; CO2 gas concentration is 30%; acidified steel slag is kept in air for 29 s before CO2 quenching.

[0053] (4) The stirring rate during the crystallization process is 300 rpm, and the pH is adjusted to 10;

[0054] In this embodiment, the calcium leaching rate in the calcium bicarbonate filtrate was 96.53%. Using the same minerals and without ultrasonic activation, acidified steel slag was directly subjected to CO2 gas quenching under identical conditions, resulting in a calcium leaching rate of 84.32%.

[0055] The aragonite-type calcium carbonate prepared in this embodiment has a content of 90% and a whiteness of 97%.

Claims

1. A method for preparing aragonite-type calcium carbonate by fixing carbon dioxide in steel slag, characterized in that, Includes the following steps: (1) The steel slag is crushed and ground into steel slag powder, and then placed in an ultrasonic wave to activate it, so as to obtain ultrasonically activated steel slag powder. (2) The ultrasonically activated steel slag powder is mixed with water, pure acetic acid solvent is added and heated to acidify, thus producing acidified steel slag; (3) The acidified steel slag is quenched with CO2 gas, water is added until the mass ratio of acetic acid leachate to steel slag powder is 3-10:1, the pH of leachate is adjusted to 7-9, CO2 is stopped after stirring for 10-90 min, and calcium bicarbonate filtrate is obtained by filtration. (4) Crystallize and filter the calcium bicarbonate filtrate to obtain aragonite-type calcium carbonate. The stirring rate during the crystallization process is 200-600 rpm and the pH is 9-11.

2. The method for preparing aragonite-type calcium carbonate by fixing carbon dioxide in steel slag according to claim 1, characterized in that, The main components and their mass percentages of the steel slag are as follows: CaO: 40%–50%, MgO: 5%–15%, SiO2: 10%–20%, Al2O3: 1%–5%, FeO: 10%–20%, MnO: 1%–5%.

3. The method for preparing aragonite-type calcium carbonate by fixing carbon dioxide in steel slag according to claim 1, characterized in that, In step (1), the portion of the steel slag powder with a particle size of less than 74 μm accounts for 65% to 80% of the total mass, and the portion with a particle size between 74 and 150 μm accounts for 20% to 35% of the total mass.

4. The method for preparing aragonite-type calcium carbonate by fixing carbon dioxide in steel slag according to claim 1, characterized in that, The ultrasonic activation power in step (1) is 500-800W, and the activation time is 20-60min.

5. The method for preparing aragonite-type calcium carbonate by fixing carbon dioxide in steel slag according to claim 1, characterized in that, In step (2), the mass ratio of the steel slag powder to the total mass of the water and acetic acid solution is 1 to 3:1; the amount of water and pure acetic acid solvent used is calculated based on the mass concentration of the acetic acid solution formed after mixing water and pure acetic acid solvent, which is 30 to 70%.

6. The method for preparing aragonite-type calcium carbonate by fixing carbon dioxide in steel slag according to claim 1, characterized in that, The acidification temperature in step (2) is 60-120℃ and the acidification time is 30-150min.

7. The method for preparing aragonite-type calcium carbonate by fixing carbon dioxide in steel slag according to claim 1, characterized in that, The CO2 gas quenching in step (3) uses steel plant tail gas with a CO2 concentration of 10-50% and a quenching pressure of 0.2-0.5 MPa.

8. The method for preparing aragonite-type calcium carbonate by fixing carbon dioxide in steel slag according to claim 1, characterized in that, The residence time of the acidified steel slag in air before CO2 gas quenching in step (3) is less than 30s.

9. The method for preparing aragonite-type calcium carbonate by fixing carbon dioxide in steel slag according to claim 1, characterized in that, The aragonite-type calcium carbonate prepared by the method has a content of over 85% and a whiteness of over 95.

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