Activated regenerated micro powder as well as preparation method and application thereof

Abstract

The invention discloses activated regenerated micro-powder as well as a preparation method and application thereof, and belongs to the technical field of waste concrete regenerated micro-powder. The activated regenerated micro-powder provided by the invention is prepared by the following steps: crushing waste concrete, carrying out ball milling, screening to obtain initial regenerated micro-powder with the particle size of less than 150 microns, adding the initial regenerated micro-powder into a carbon dioxide absorption solvent, and mixing to obtain regenerated micro-powder slurry; and heating the regenerated micro-powder slurry to 45-65 DEG C, introducing CO2 into the regenerated micro-powder slurry to carry out wet mineralization treatment, and carrying out suction filtration and drying to obtain the regenerated micro-powder. The preparation method of the regenerated micro powder provided by the invention is simple, not only is full utilization of active calcium and magnesium components in the waste concrete powder realized, but also permanent fixation and storage of carbon dioxide are effectively realized, the actual apparent carbon sequestration amount reaches 33-39%, the maximum mineralization efficiency can reach 94.41%, and the regenerated micro powder can be recycled. The method has a good promotion effect on protecting the ecological environment and promoting the development of circular economy.

Description

Technical Field

[0001] The invention belongs to the technical field of waste concrete recycled micropowder, and in particular relates to activated recycled micropowder and a preparation method and application thereof. Background Art

[0002] The resource utilization of waste concrete and the reduction of CO2 emissions are two major issues facing the construction industry. The demolition and reconstruction of a large number of buildings have led to a sharp increase in the amount of waste concrete. The usual way to deal with these wastes is to pile them in the open air or landfill them, but this practice not only consumes a lot of land resources, but also causes serious environmental pollution. In addition, with the increasing global attention to carbon emissions in the construction industry, reducing carbon emissions has become an urgent task that the industry must face and solve.

[0003] Recycled micropowder is produced in the process of recycling recycled aggregates from crushed waste concrete. It has the characteristics of uneven pore size distribution and complex components. When used directly as cement mineral admixture, it has low activity and will reduce the working performance, strength performance and durability of concrete. At present, the activation modification methods of recycled micropowder system include heat treatment, alkali excitation and mechanical treatment. Although these methods can effectively improve the reaction activity of recycled micropowder, their high cost hinders the widespread promotion and application of recycled micropowder recycling technology in the construction industry.

[0004] Based on the development of CO2 mineralization storage and utilization technology of cement-based materials, CO2 is used to react with calcium hydroxide, hydrated calcium silicate gel, calcium vanadium and unhydrated cement clinker in the regenerated micropowder to form calcium carbonate and amorphous silica gel, which can achieve permanent storage of CO2. Most of the existing mineralization methods are dry mineralization processes based on gas-solid reactions. The degree of mineralization reaction is not high, and the activity of the prepared regenerated micropowder is low, which is not suitable for large-scale batch use. Therefore, how to provide an activation method that can significantly stimulate the activity of regenerated micropowder, fully improve the degree of mineralization reaction of regenerated micropowder and has a low processing cost is a problem that technicians in this field need to solve. Summary of the invention

[0005] In view of the above-mentioned prior art, the present invention provides an activated regenerated micropowder and a preparation method and application thereof, so as to solve the problems of low activity of regenerated micropowder prepared in the prior art and low CO2 fixation absorption rate.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is to provide a method for preparing activated regenerated micropowder, comprising the following steps:

[0007] S1. Crushing: crushing the waste concrete to obtain crushed particles with a particle size of less than 2 mm;

[0008] S2. Ball milling: ball mill the crushed particles for 2 to 4 hours and sieve to obtain initial regenerated micro powder with a particle size of less than 150 μm;

[0009] S3. Slurrying: mixing the initial regenerated micropowder with the carbon dioxide absorbing solvent in a mass ratio of 1:3 to 20 to obtain a regenerated micropowder slurry;

[0010] S4. Mineralization treatment: The regenerated micropowder slurry is placed in a closed environment, heated to 45-65°C, stirred at a speed of 200-350rpm, and a flue gas containing CO2 is introduced during the stirring process, and then wet mineralization treatment is performed at normal pressure for 4-8h to obtain a mineralized regenerated micropowder slurry;

[0011] S5. Filtration and drying: Filtration and drying of the mineralized regenerated micro powder slurry are performed to obtain.

[0012] The beneficial effects of the above technical solution are as follows: the main components of the initial regenerated micropowder include hydrated calcium silicate, calcium hydroxide and a small amount of unhydrated tricalcium silicate and dicalcium silicate. In the present invention, the initial regenerated micropowder is fully mixed with water at a liquid-solid ratio of 3 to 20:1 to form a regenerated micropowder slurry. After the flue gas is introduced, CO2 can first be fully dissolved in water to form carbonate ions, and then react with the active components in the slurry to undergo a mineralization reaction, wherein calcium hydroxide first reacts with CO2 to produce calcium carbonate; secondly, a small amount of tricalcium silicate, dicalcium silicate and a large amount of hydrated calcium silicate can all undergo a mineralization reaction, and the mineralization activity is relatively high, and the mineralization products are calcium carbonate and amorphous silica gel; this type of mineralization product can play a certain role in carbon fixation. Temperature control at 45 to 65°C can promote the dissolution of active calcium ions in the regenerated micropowder while ensuring the dissolution of CO2, thereby accelerating the mineralization reaction and reducing the agglomeration of the mineralization products.

[0013] At the same time, the present invention performs wet mineralization on the regenerated micropowder slurry under normal pressure, provides a gas-liquid-solid three-phase mineralization reaction environment for the regenerated micropowder, provides milder reaction conditions for the mineralization reaction, reduces the coating of the reactants by the mineralization product calcium carbonate, and further increases the degree of mineralization reaction. The prepared activated regenerated micropowder can be added to cement or concrete as an auxiliary cementitious material to improve its compressive strength, and can also obtain a product with higher purity when used to prepare light calcium carbonate.

[0014] Based on the above technical solution, the present invention can also be improved as follows.

[0015] Furthermore, the carbon dioxide absorption solvent is water or monoethanolamine solution.

[0016] Furthermore, the mass fraction of the monoethanolamine solution is 10-20%.

[0017] The beneficial effects of adopting the above technical scheme are: using monoethanolamine (MEA) solution as a solvent to prepare the regenerated micropowder slurry, the weak alkaline solution can absorb the acidic gas CO2, can enrich the CO2 in the flue gas, and then release the pure CO2 again after heating and regeneration, and undergo mineralization reaction with the active components in the slurry.

[0018] Furthermore, the concentration of CO2 in the CO2-containing flue gas is 5 to 100%.

[0019] Furthermore, the ambient temperature of S4. mineralization treatment is 25° C. and the humidity is 50% RH.

[0020] Furthermore, the flow rate of flue gas introduced into S4 is 1 to 5 L / min.

[0021] The invention also discloses an activated regenerated micropowder, which is prepared by the activated regenerated micropowder preparation method.

[0022] Furthermore, the average particle size of the activated regenerated micropowder is 10-20 μm, and the specific surface area is greater than 350 m 2 / kg, the content of calcium carbonate in the phase composition is greater than 60%.

[0023] The invention also discloses an application of the activated regenerated micro powder as an auxiliary gel material in cement concrete.

[0024] The beneficial effects of adopting the above technical scheme are: the nucleation effect of calcium carbonate in the activated regenerated micropowder can promote the growth of cement hydration products around the crystal nucleus, the filling effect can increase the density of the slurry microstructure, and the amorphous silica gel can react with calcium hydroxide to form a hydrated calcium silicate gel with a cross-linking effect, which is beneficial to improve the strength of concrete.

[0025] The invention also discloses an application of the activated regenerated micropowder to prepare light calcium carbonate with a purity greater than 99% by adding sodium hydroxide solution.

[0026] The beneficial effect of adopting the above technical solution is that the sodium hydroxide solution can remove the amorphous silica gel in the activated regenerated micropowder.

[0027] The beneficial effects of the present invention are:

[0028] 1. The preparation method of the activated regenerated micropowder of the present invention has the advantages of low cost, environmental friendliness and resource recycling. It not only significantly improves the reaction activity of the regenerated micropowder and realizes the full utilization of the active calcium and magnesium components in the waste concrete powder, but also effectively realizes the permanent fixation and storage of carbon dioxide. The actual apparent carbon fixation amount reaches 33-39%, and the maximum mineralization efficiency can reach 94.41%. Each ton of initial regenerated micropowder can fix 385.6 kg of CO2, which fully stimulates the carbon fixation potential of the active components in the regenerated micropowder, and has a good driving effect on protecting the ecological environment and promoting the development of the circular economy.

[0029] 2. The activated regenerated micropowder prepared by the present invention is treated by mineralization by absorbing and enriching CO2 in a solvent. The chemical composition is calcium carbonate and amorphous silica gel, which can be applied to cement or concrete to promote its hydration and effectively improve its compressive performance. DETAILED DESCRIPTION

[0030] The waste concrete used in the embodiments of the present invention and the comparative examples comes from construction waste of old buildings. The waste concrete has a service life of 12 years and a strength grade of C25.

[0031] The specific implementation modes of the present invention are described in detail below with reference to the embodiments.

[0032] Example 1

[0033] A method for preparing activated regenerated micropowder comprises the following steps:

[0034] S1. Crushing: Use a jaw crusher to initially crush the waste concrete and sieve it, separate the particles larger than 2 mm and crush them repeatedly to obtain crushed particles with a particle size of less than 2 mm;

[0035] S2. Ball milling: The crushed particles are ball milled for 2 hours by a drum ball mill, and then the ball milled particles are screened by an electric vibrating screen to screen out powder with a particle size of less than 150 μm to obtain the initial regenerated micro powder;

[0036] S3. Pulping: The initial regenerated powder was mixed with water and stirred evenly, and the mass ratio of water to the initial regenerated powder was controlled to be 3:1 to obtain a regenerated powder slurry;

[0037] S4. Mineralization treatment: Pour the regenerated micropowder slurry into a three-necked flask, and use a water bath heating device to control its temperature to 60°C, then use a mechanical stirring device to continuously stir the regenerated micropowder slurry, the speed of the stirring device is 300rpm, and during the stirring process, flue gas is passed into the regenerated micropowder slurry at a flow rate of 2L / min, wherein the volume concentration of CO2 in the flue gas is 99.5%, and the regenerated micropowder slurry is subjected to wet mineralization treatment for 4h under normal pressure conditions to obtain a mineralized regenerated micropowder slurry; the ambient temperature of the mineralization treatment is 25°C and the humidity is 50% RH;

[0038] S5. Filtration and drying: The mineralized regenerated micropowder slurry is filtered and then placed in a constant temperature drying oven at 105°C to dry to constant weight to obtain activated regenerated micropowder.

[0039] Example 2

[0040] A method for preparing activated regenerated micropowder comprises the following steps:

[0041] S1. Crushing: Use a jaw crusher to initially crush the waste concrete and sieve it, separate the particles larger than 2 mm and crush them repeatedly to obtain crushed particles with a particle size of less than 2 mm;

[0042] S2. Ball milling: The crushed particles are ball milled for 2 hours by a drum ball mill, and then the ball milled particles are screened by an electric vibrating screen to screen out powder with a particle size of less than 150 μm to obtain the initial regenerated micro powder;

[0043] S3 pulping: the initial regeneration powder and water were mixed and stirred evenly, the mass ratio of water to the initial regeneration powder was controlled to be 20: 1, to obtain a regeneration powder slurry;

[0044] S4. Mineralization treatment: Pour the regenerated micropowder slurry into a three-necked flask, and use a water bath heating device to control its temperature to 60°C, then use a mechanical stirring device to continuously stir the regenerated micropowder slurry, the speed of the stirring device is 300rpm, and during the stirring process, flue gas is passed into the regenerated micropowder slurry at a flow rate of 2L / min, wherein the volume concentration of CO2 in the flue gas is 99.5%, and the regenerated micropowder slurry is subjected to wet mineralization treatment for 4h under normal pressure conditions to obtain a mineralized regenerated micropowder slurry; the ambient temperature of the mineralization treatment is 25°C and the humidity is 50% RH;

[0045] S5. Filtration and drying: The mineralized regenerated micropowder slurry is filtered and then placed in a constant temperature drying oven at 105°C to dry to constant weight to obtain activated regenerated micropowder.

[0046] Example 3

[0047] A method for preparing activated regenerated micropowder comprises the following steps:

[0048] S1. Crushing: Use a jaw crusher to initially crush the waste concrete and sieve it, separate the particles larger than 2 mm and crush them repeatedly to obtain crushed particles with a particle size of less than 2 mm;

[0049] S2. Ball milling: The crushed particles are ball milled for 2 hours by a drum ball mill, and then the ball milled particles are screened by an electric vibrating screen to screen out powder with a particle size of less than 150 μm to obtain the initial regenerated micro powder;

[0050] S3. Pulping: The initial regenerated powder was mixed with water and stirred evenly, and the mass ratio of water to the initial regenerated powder was controlled to be 10:1 to obtain a regenerated powder slurry;

[0051] S4. Mineralization treatment: Pour the regenerated micropowder slurry into a three-necked flask, and use a water bath heating device to control its temperature to 60°C, then use a mechanical stirring device to continuously stir the regenerated micropowder slurry, the speed of the stirring device is 300rpm, and during the stirring process, flue gas is passed into the regenerated micropowder slurry at a flow rate of 2L / min, wherein the volume concentration of CO2 in the flue gas is 20%, and the regenerated micropowder slurry is subjected to wet mineralization treatment for 4h under normal pressure conditions to obtain a mineralized regenerated micropowder slurry; the ambient temperature of the mineralization treatment is 25°C and the humidity is 50% RH;

[0052] S5. Filtration and drying: The mineralized regenerated micropowder slurry is filtered and then placed in a constant temperature drying oven at 105°C to dry to constant weight to obtain activated regenerated micropowder.

[0053] Example 4

[0054] A method for preparing activated regenerated micropowder comprises the following steps:

[0055] S1. Crushing: Use a jaw crusher to initially crush the waste concrete and sieve it, separate the particles larger than 2 mm and crush them repeatedly to obtain crushed particles with a particle size of less than 2 mm;

[0056] S2. Ball milling: The crushed particles are ball milled for 2 hours by a drum ball mill, and then the ball milled particles are screened by an electric vibrating screen to screen out powder with a particle size of less than 150 μm to obtain the initial regenerated micro powder;

[0057] S3. Pulping: The initial regenerated powder was mixed with water and stirred evenly, and the mass ratio of water to the initial regenerated powder was controlled to be 10:1 to obtain a regenerated powder slurry;

[0058] S4. Mineralization treatment: Pour the regenerated micropowder slurry into a three-necked flask, and use a water bath heating device to control its temperature to 60°C, then use a mechanical stirring device to continuously stir the regenerated micropowder slurry, the speed of the stirring device is 300rpm, and during the stirring process, flue gas is passed into the regenerated micropowder slurry at a flow rate of 2L / min, wherein the volume concentration of CO2 in the flue gas is 20%, and the regenerated micropowder slurry is subjected to wet mineralization treatment for 8h under normal pressure conditions to obtain a mineralized regenerated micropowder slurry; the ambient temperature of the mineralization treatment is 25°C and the humidity is 50% RH;

[0059] S5. Filtration and drying: The mineralized regenerated micropowder slurry is filtered and then placed in a constant temperature drying oven at 105°C to dry to constant weight to obtain activated regenerated micropowder.

[0060] Example 5

[0061] A method for preparing activated regenerated micropowder comprises the following steps:

[0062] S1. Crushing: Use a jaw crusher to initially crush the waste concrete and sieve it, separate the particles larger than 2 mm and crush them repeatedly to obtain crushed particles with a particle size of less than 2 mm;

[0063] S2. Ball milling: The crushed particles are ball milled for 2 hours by a drum ball mill, and then the ball milled particles are screened by an electric vibrating screen to screen out powder with a particle size of less than 150 μm to obtain the initial regenerated micro powder;

[0064] S3. Pulping: preparing a 15% mass fraction of monoethanolamine (MEA) solution, mixing the initial regenerated powder with the monoethanolamine solution, and controlling the mass ratio of the solution to the initial regenerated powder to be 10:1 to obtain a regenerated powder slurry;

[0065] S4. Mineralization treatment: Pour the regenerated micropowder slurry into a three-necked flask, and use a water bath heating device to control its temperature to 60°C, then use a mechanical stirring device to continuously stir the regenerated micropowder slurry, the speed of the stirring device is 300rpm, and during the stirring process, flue gas is passed into the regenerated micropowder slurry at a flow rate of 2L / min, wherein the volume concentration of CO2 in the flue gas is 20%, and the regenerated micropowder slurry is subjected to wet mineralization treatment for 4h under normal pressure conditions to obtain a mineralized regenerated micropowder slurry; the ambient temperature of the mineralization treatment is 25°C and the humidity is 50% RH;

[0066] S5. Filtration and drying: The mineralized regenerated micropowder slurry is filtered and then placed in a constant temperature drying oven at 105°C to dry to constant weight to obtain activated regenerated micropowder.

[0067] Comparative Example 1

[0068] A method for preparing activated regenerated micropowder comprises the following steps:

[0069] S1. Crushing: Use a jaw crusher to initially crush the waste concrete and sieve it, separate the particles larger than 2 mm and crush them repeatedly to obtain crushed particles with a particle size of less than 2 mm;

[0070] S2. Ball milling: The crushed particles are ball milled for 2 hours by a drum ball mill, and then the ball milled particles are screened by an electric vibrating screen to screen out powder with a particle size of less than 150 μm to obtain the initial regenerated micro powder;

[0071] S3. Pulping: The initial regenerated powder was mixed with water and stirred evenly, and the mass ratio of water to the initial regenerated powder was controlled to be 3:1 to obtain a regenerated powder slurry;

[0072] S4. Mineralization treatment: Pour the regenerated micropowder slurry into a three-necked flask, and use a water bath heating device to control its temperature to 20°C, then use a mechanical stirring device to continuously stir the regenerated micropowder slurry, the speed of the stirring device is 300rpm, and during the stirring process, flue gas is passed into the regenerated micropowder slurry at a flow rate of 2L / min, wherein the volume concentration of CO2 in the flue gas is 20%, and the regenerated micropowder slurry is subjected to wet mineralization treatment for 4h under normal pressure conditions to obtain a mineralized regenerated micropowder slurry; the ambient temperature of the mineralization treatment is 25°C and the humidity is 50% RH;

[0073] S5. Filtration and drying: The mineralized regenerated micropowder slurry is filtered and then placed in a constant temperature drying oven at 105°C to dry to constant weight to obtain activated regenerated micropowder.

[0074] Comparative Example 2

[0075] A method for preparing activated regenerated micropowder comprises the following steps:

[0076] S1. Crushing: Use a jaw crusher to initially crush the waste concrete and sieve it, separate the particles larger than 2 mm and crush them repeatedly to obtain crushed particles with a particle size of less than 2 mm;

[0077] S2. Ball milling: The crushed particles are ball milled for 2 hours by a drum ball mill, and then the ball milled particles are screened by an electric vibrating screen to screen out powder with a particle size of less than 150 μm to obtain the initial regenerated micro powder;

[0078] S3 pretreatment: spray water mist on the surface of the initial regenerated powder and mix evenly, control the water-solid ratio of the water mist to the initial regenerated powder to be 0.25: 1, to obtain a pretreated powder;

[0079] S4. Mineralization: The pretreated powder was placed in a mineralization reactor, CO2 was introduced into the mineralization reactor at a volume concentration of 20% flue gas, the pressure of the mineralization reactor was maintained at 0.1MPa, and the pretreated powder was mineralized at 60°C and 50% RH for 4h to obtain activated regenerated micropowder;

[0080] S5. Drying: Place the activated regenerated micropowder in a constant temperature drying oven at 105°C and dry to constant weight to obtain the activated regenerated micropowder.

[0081] Comparative Example 3

[0082] A method for preparing activated regenerated micropowder comprises the following steps:

[0083] S1. Crushing: Use a jaw crusher to initially crush the waste concrete and sieve it, separate the particles larger than 2 mm and crush them repeatedly to obtain crushed particles with a particle size of less than 2 mm;

[0084] S2. Ball milling: The crushed particles are ball milled for 2 hours by a drum ball mill, and then the ball milled particles are screened by an electric vibrating screen to screen out powder with a particle size of less than 150 μm to obtain the initial regenerated micro powder;

[0085] S3 pretreatment: spray water mist on the surface of the initial regenerated powder and mix evenly, control the water-solid ratio of the water mist to the initial regenerated powder to be 0.25: 1, to obtain a pretreated powder;

[0086] S4. Mineralization: The pretreated powder was placed in a mineralization reactor, CO2 was introduced into the mineralization reactor at a volume concentration of 20% flue gas, the pressure of the mineralization reactor was maintained at 0.1MPa, and the pretreated powder was mineralized at 60°C and 50% RH for 8h to obtain activated regenerated micropowder;

[0087] S5. Drying: Place the activated regenerated micropowder in a constant temperature drying oven at 105°C and dry to constant weight to obtain the activated regenerated micropowder.

[0088] Experimental example

[0089] 1. Composition determination

[0090] The chemical compositions of the initial regenerated micropowders prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were measured, and the results are shown in Table 1.

[0091] Table 1 Determination results of chemical composition of initial regenerated micropowder

[0092]

[0093] As can be seen from Table 1, the chemical composition of the initial regenerated micropowder is mainly calcium oxide and silicon oxide, and the larger loss on ignition is attributed to the decarbonization of calcium carbonate produced by air carbonization.

[0094] 2. Carbon fixation capacity detection

[0095] The apparent carbon fixation amount of the activated regenerated micropowder prepared in Examples 1 to 5 and Comparative Examples 1 to 3 was tested.

[0096] Calcium carbonate decomposes at 500°C to 950°C, resulting in mass loss. The present invention uses a pyrolysis method to test the weight loss of activated regenerated micropowder in the range of 500°C to 950°C as the CO2 fixation amount. The CO2 fixation amount represents the mass fraction of carbon dioxide sealed in the material in the form of carbonate, which is determined by formula (1); the actual apparent carbon fixation amount represents the ability of the activated regenerated micropowder material to absorb and fix carbon dioxide, which is obtained by formula (2) and is calculated as follows:

[0097]

[0098] Among them, Δm (500-950 ℃) Refers to the mass loss of CaCO3 decomposition between 500 and 950°C; m 105 ℃ refers to the mass of the powder sample at 105℃; CO2 fixation refers to the CO2 fixation of the activated regenerated micropowder calculated according to formula (1); CO2 initial fixation refers to the CO2 fixation of the initial regenerated micropowder calculated according to formula (1).

[0099] The theoretical carbon fixation is the theoretical mass fraction of CO2 sequestration that can be achieved based on stoichiometry and the content of reactive oxides in the regenerated micropowder, which is determined by formula (3); the degree of mineralization refers to the ratio of the actual apparent carbon fixation to the theoretical carbon fixation, reflecting the degree of mineralization reaction, which is determined by formula (4) and the calculation formula is as follows:

[0100]

[0101] Wherein, each mineral in formula (3) is expressed in mass percentage, and the stoichiometric mass factor assumes that all CaO (except that bound in CaCO3 and CaSO4) forms CaCO3, all MgO forms MgCO3, and all Na2O and K2O form Na2CO3 and K2CO3.

[0102] The theoretical carbon fixation of the initial regenerated micropowder was calculated based on the chemical composition of the initial regenerated micropowder, wherein the CaCO3 content was calculated by formula (1) combined with the stoichiometric relationship; the theoretical carbon fixation of the initial regenerated micropowder, the actual apparent carbon fixation of the activated regenerated micropowder and the degree of mineralization were calculated. The results are shown in Table 2.

[0103] Table 2 Carbon fixation capacity test results

[0104]

[0105] From the results in Table 2, it can be seen that the initial CO2 fixation of the initial regenerated micropowder prepared in Examples 1 to 5 and Comparative Examples 1 to 3 is 5.36%. According to the stoichiometric relationship, the initial regenerated micropowder contains 11.51% CaCO3. This is because the initial regenerated micropowder comes from the construction waste of abandoned buildings, in which the concrete has a service life of 12 years. The concrete itself is alkaline and has been in a complex air environment for a long time, causing a certain degree of natural carbonization. Concrete carbonization refers to the process in which CO2 gas in the air penetrates into the concrete through the pores of hardened concrete, reacts chemically with its alkaline substances (Ca(OH)2) to form calcium carbonate, and reduces the alkalinity of the concrete. This process is related to the CO2 concentration and humidity in the medium in which the concrete is located. The theoretical carbon fixation amount calculated based on the initial CO2 fixation and chemical composition of the initial regenerated micropowder is 40.84%, which shows that even if the abandoned concrete will inevitably undergo natural carbonization, the initial regenerated micropowder obtained after crushing and grinding it still has a huge carbon fixation potential.

[0106] Comparing Examples 1 to 5 and Comparative Example 1, the actual apparent carbon fixation of the activated regenerated micropowder prepared in Comparative Example 1 is 22.80%, and the degree of mineralization is only 55.84%, which is relatively low. The actual apparent carbon fixation of the activated regenerated micropowder prepared in Examples 1 to 5 is above 33%, and the degree of mineralization is also above 80%. This shows that the activation method of wet mineralization at room temperature cannot fully stimulate the mineralization activity of the regenerated micropowder. Even if CO2 can be better dissolved in the slurry, the dissolution amount of active calcium ions in the regenerated micropowder at room temperature is very low. The calcium carbonate and silica gel formed in the initial stage of the reaction will cover the solid reactants, thereby limiting the further occurrence of the mineralization reaction; and when the temperature of the reactor is controlled at 60°C using a water bath heating device, it can promote the dissolution of active calcium ions in the regenerated micropowder while ensuring the dissolution of CO2, thereby accelerating the mineralization reaction. At the same time, the increase in temperature is also conducive to reducing the agglomeration of the mineralized products.

[0107] Comparing Examples 1 to 5 and Comparative Examples 2 to 3, the actual apparent carbon fixation of the activated regenerated micropowder prepared based on dry mineralization for 4h and 8h in Comparative Examples 2 to 3 was only 26.67% and 27.73%, and the degree of mineralization was only 65.30% and 67.90%, while the actual apparent carbon fixation of the activated regenerated micropowder prepared based on wet mineralization for 4h and 8h in Examples 1 to 5 reached 38.44% and 38.56%, and the degree of mineralization reached 94.13% and 94.41%, and the degree of mineralization of wet mineralization was 41.55% higher than that of dry mineralization. This shows that compared with dry mineralization, wet mineralization significantly stimulates the activity of regenerated micropowder and significantly improves the degree of mineralization of regenerated micropowder. Wet mineralization fully utilizes the active components in the regenerated micropowder through mineralization reaction, and completely converts them into calcium carbonate and amorphous silica gel, which are components that are beneficial to the development of concrete strength, and is beneficial to the practical application of the activated regenerated micropowder as cement auxiliary cementitious material and light calcium carbonate preparation.

[0108] Comparing Example 1 and Example 2, the actual apparent carbon fixation of Example 1 is 34.67%, and the degree of mineralization is 84.89%. When the liquid-solid ratio of the regenerated micropowder slurry is increased from 3:1 to 20:1, the actual apparent carbon fixation of Example 2 is increased to 38.44%, and the degree of mineralization is also increased to 94.13%. At this time, the apparent carbon fixation achieved is close to the theoretical carbon fixation of the initial regenerated micropowder. This is because the exothermic reaction in the mineral carbonation process and the reaction temperature of 60°C will cause water evaporation. When the liquid-solid ratio is relatively low, the mineralization efficiency cannot reach the maximum value. A higher liquid-solid ratio is conducive to the dissolution of CO2 and the dissolution of active calcium ions in the regenerated micropowder, so that the mineralization reaction can be fully carried out and the carbon fixation potential of the active components in the regenerated micropowder can be fully released.

[0109] Comparing Example 2 with Examples 3 to 4, the actual apparent carbon fixation of Example 2 is 38.44%, and the degree of mineralization is 94.13%. When the concentration of CO2 in the flue gas is reduced from 99.5% to 20%, and the liquid-solid ratio of the regenerated micropowder slurry is reduced from 20:1 to 10:1, the actual apparent carbon fixation of Example 3 reaches 33.44%, and the degree of mineralization reaches 81.88%; when the mineralization reaction time is further increased from 4h to 8h, the actual apparent carbon fixation of Example 4 reaches 38.56%, and the degree of mineralization reaches 94.41%. This shows that when the CO2 concentration in the flue gas decreases, the actual apparent carbon fixation and mineralization of the activated regenerated micropowder are reduced, but by extending the reaction time, its actual apparent carbon fixation and mineralization can still reach the maximum value.

[0110] Comparing Example 5 with Example 4, the actual apparent carbon fixation amount of Example 5 is 31.25%, and the degree of mineralization is 92.21%, which are close to Example 4. However, Example 5 reduces the reaction time from 8h to 4h, which indicates that the amine solution is more conducive to the enrichment of CO2 and the mineralization reaction.

[0111] In summary, the regenerated micropowder activation method based on the alcoholamine method to absorb and enrich CO2 and wet mineralization is suitable for treating low-concentration industrial flue gas with a CO2 concentration of 15-25%. It can quickly react with the regenerated micropowder slurry under normal pressure conditions to mineralize. At the same time, the apparent carbon fixation of the activated regenerated micropowder can reach 33-39%, and the maximum actual apparent carbon fixation reaches 38.56%, which fully stimulates the carbon fixation potential of the active components in the regenerated micropowder, and can fix 385.6 kg CO2 / ton of initial regenerated micropowder, and the maximum mineralization efficiency can reach 94.41%. At the same time, the activation method using alcoholamine solution to absorb and enrich CO2 mineralized regenerated micropowder realizes a rapid and efficient mineralization reaction, and the mineralization efficiency within 4 hours can reach 92.21%.

[0112] The activated regenerated micropowders prepared in Examples 1 to 5 above have an average particle size of 10 to 20 μm and a specific surface area of ​​more than 350 m 2 / kg, the content of calcium carbonate in the physical phase composition is greater than 60%, which can be used as an auxiliary cementitious material for cement and applied to the production of ordinary silicate cement, composite silicate cement and special cement, replacing part of cement clinker, reducing the amount of clinker and the cost of cement production; sodium hydroxide solution can also be used to remove the amorphous silica gel in the activated regenerated micropowder to obtain light calcium carbonate with a purity of more than 99%, which is widely used in rubber, plastics, papermaking, coatings, paints, inks, cables, building supplies, food, medicine, textiles, feed, toothpaste and other daily chemical industries as a filler to increase the volume of the product and reduce production costs.

[0113] Although the specific implementation of the present invention is described in detail in conjunction with the embodiments, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A method for preparing activated regenerated micropowder, characterized in that: The following steps are involved: S1. Crushing: crushing the waste concrete to obtain crushed particles with a particle size of less than 2 mm; S2. Ball milling: ball mill the crushed particles for 2 to 4 hours and sieve to obtain initial regenerated micro powder with a particle size of less than 150 μm; S3. Slurrying: mixing the initial regenerated micropowder with the carbon dioxide absorbing solvent in a mass ratio of 1:3 to 20 to obtain a regenerated micropowder slurry; S4. Mineralization treatment: The regenerated micropowder slurry is placed in a closed environment, heated to 45-65°C, stirred at a speed of 200-350rpm, and a flue gas containing CO2 is introduced during the stirring process, and then wet mineralization treatment is performed at normal pressure for 4-8h to obtain a mineralized regenerated micropowder slurry; S5. Filtration and drying: Filtration and drying of the mineralized regenerated micro powder slurry are performed to obtain.

2. The preparation method according to claim 1, characterized in that: The carbon dioxide absorption solvent is water or monoethanolamine solution.

3. The preparation method according to claim 2, characterized in that: The mass fraction of the monoethanolamine solution is 10-20%.

4. The preparation method according to claim 1, characterized in that: The concentration of CO2 in the CO2-containing flue gas is 5-100%.

5. The preparation method according to claim 1, characterized in that: S4. The ambient temperature of the mineralization treatment is 25°C and the humidity is 50% RH.

6. The preparation method according to claim 1, characterized in that: The flow rate of flue gas introduced into S4 is 1 to 5 L / min.

7. An activated regenerated micro powder, characterized in that: The activated regenerated micropowder is prepared by the method for preparing the activated regenerated micropowder according to any one of claims 1 to 6.

8. The activated regenerated micropowder according to claim 7, characterized in that: The particle size of the activated regenerated micropowder is 10-20 μm, and the specific surface area is greater than 350 m 2 / kg, the content of calcium carbonate in the phase composition is greater than 60%.

9. The use of the activated regenerated micropowder according to claim 7 or 8, characterized in that: The activated regenerated micro powder is used as an auxiliary gel material in cement concrete.

10. The use of the activated regenerated micropowder according to claim 7 or 8, characterized in that: The activated regenerated micropowder is added into a sodium hydroxide solution to prepare light calcium carbonate with a purity greater than 99%.

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