Composite geopolymer material as well as preparation method and application thereof

Abstract

The invention provides a composite geopolymer material as well as a preparation method and application thereof, and belongs to the technical field of geopolymer materials. The method comprises the following steps: providing initial alkalinity and soluble salt ions of a system by using papermaking black liquor ash, providing an aluminum-silicon precursor by using coal gangue powder, obtaining geopolymer slurry with proper rheology through coupling regulation and control of proportion, granularity and water-binder ratio, and forming the geopolymer slurry into a sample blank; then absorbing industrial furnace tail gas by using a composite amine solution to prepare a CO2-rich solution, soaking the sample blank for a short time to enable the CO2-rich solution to uniformly permeate into pores, heating in a medium-low temperature and high humidity environment to promote the CO2-rich solution to slowly release CO2 into the plate, and synchronously evolving with a gel network to form uniform and stable carbonate microcrystals and compact pore walls, so as to achieve the purpose of improving the performance of the plate. According to the process, the surface layer density and the size stability are rapidly improved, meanwhile, CO2 resource solid storage and amine liquid closed-loop circulation are achieved, NaOH / water glass does not need to be additionally added, the corrosivity and the safety risk are low, and the process is suitable for continuous industrial production.

Description

Technical Field

[0001] This invention belongs to the field of geopolymer materials technology, specifically relating to a composite geopolymer material, its preparation method, and its application. Background Technology

[0002] Geopolymers (alkali-activated aluminosilicates) are considered ideal materials to replace sintered ceramics and organic resin artificial stone as decorative panels due to their advantages of low-temperature molding, early strength, high durability and low environmental impact.

[0003] In existing technologies, the process of making geopolymer decorative panels generally relies on external strong alkaline activators (NaOH, KOH, liquid silicates, etc.), which have pain points such as strong in-situ corrosion, high occupational health and transportation safety risks, limited selection of equipment and materials, and unfavorable costs and carbon footprint of liquid alkali.

[0004] Carbon dioxide-accelerated setting / carbonization curing, as a green and low-carbon solidification method, has demonstrated comprehensive advantages in silicate cement systems, including shortening curing time, creating a dense surface, and encapsulating CO2. However, when direct gas-phase carbonization is used in low-calcium or calcium-free geopolymer systems, the system pH often drops sharply due to the CO2 acidification effect, inhibiting unreacted gel units and increasing sodium content. + / K + The outward migration of carbonate crystals exacerbates blooming and surface powdering. Especially under gas phase conditions, a dense carbonate "shell" easily forms on the surface, hindering further inward diffusion of CO2, resulting in uneven curing and a significant mechanical gradient.

[0005] Therefore, it is necessary to provide a composite geopolymer material, its preparation method, and its application to solve the above problems. Summary of the Invention

[0006] This invention provides a composite geopolymer material, its preparation method, and its application. The initial alkalinity and soluble salt ions are provided by black liquor ash from papermaking, and the aluminum-silicon precursor is provided by unsintered or low-temperature roasted coal gangue powder. A rheologically suitable geopolymer slurry is obtained through the coupled control of proportions, particle size, and water-binder ratio, and then formed into a sample blank. A CO2-rich solution is then prepared by absorbing industrial furnace tail gas using a composite amine solution. The sample blank is briefly soaked to allow the CO2-rich solution to uniformly penetrate the capillaries. Heating under a medium-low temperature and high humidity environment promotes the slow release of CO2 from the CO2-rich solution into the interior of the board, where it evolves synchronously with the cementitious network, forming uniform and stable carbonate microcrystals and dense pore walls. This rapidly improves surface density and dimensional stability, while simultaneously achieving resource-based CO2 storage and closed-loop amine solution circulation. This process does not require the addition of NaOH / water glass, has low corrosiveness and safety risks, and is suitable for continuous industrial production. Therefore, it can effectively solve at least one of the technical problems mentioned in the background art.

[0007] To solve the above-mentioned technical problems, the present invention is implemented as follows: A method for preparing a composite geopolymer material includes the following steps: Step S1: Mix 10-30 parts of papermaking black liquor ash, 55-80 parts of coal gangue powder, 0.5-10 parts of silicon compensation source and 0.5-10 parts of inert filler evenly according to the mass ratio, add water at a water-binder ratio of 0.28-0.40 and stir to form a geopolymer slurry. Step S2: Prepare sample blanks using geopolymer slurry and perform a curing process; Step S3: Prepare a composite amine solution. The mass fraction of methyldiethanolamine in the composite amine solution is 20%-40%, the mass fraction of piperazine is 2%-6%, and the remainder is deionized water. Pass the tail gas of the industrial furnace containing CO2 into the composite amine solution to adsorb CO2 and form a CO2-rich solution. Step S4: Place the CO2-rich solution in the soaking tank and immerse the sample blank after the first curing process into the soaking tank. Step S5: Place the soaked sample blank in a sealed humid heat curing chamber for secondary curing. After the secondary curing is completed, the finished geopolymer material is obtained.

[0008] As a preferred improvement, the black liquor ash from papermaking includes at least the following components: 5-20 wt% Na2O and 1-8 wt% K2O; the coal gangue powder includes at least the following components: 20-35 wt% Al2O3 and 45-60 wt% SiO2. Papermaking black liquor ash is dried at 95-115℃ for 3-6 hours to constant weight, ensuring a moisture content of less than 0.5%, and then passed through a 200-mesh sieve to eliminate lumps and large particles. Coal gangue powder is obtained by directly fine grinding unsintered coal gangue powder or by fine grinding after low-temperature calcination. Specifically, unsintered coal gangue powder is directly ball-milled to a D50 of 8-25μm, or it is calcined at 600-800℃ for 1-2 hours and then ground to a D50 of 8-25μm.

[0009] As a preferred improvement, the silicon compensation source is selected as waste glass powder or ceramic waste powder; the inert filler is selected from one or more of quartz powder, limestone powder, feldspar powder and kaolin calcination residue.

[0010] As a preferred improvement, the sample blank can be formed by casting or low-pressure pressing.

[0011] As a preferred improvement, the volume fraction of CO2 in the exhaust gas of industrial furnaces and kilns is 8-20%. During the adsorption of CO2 by the composite amine solution, the temperature is controlled at 35-50℃, and the liquid-to-gas ratio is 1.5-3.0 L / Nm³. 3The solution is kept in a CO2 loading α until it reaches 0.30-0.40 mol CO2 / mol composite amine and the pH of the CO2-rich solution is between 9.5 and 10.5. Then the CO2-rich solution is cooled to 25-35℃ and filtered to remove impurities before being stored for later use.

[0012] As a preferred improvement, during the soaking process in step S4, the liquid-to-solid volume ratio is controlled at 3:1-5:1, the liquid temperature is 25-35℃, the soaking time is 10-45 minutes, and the liquid flow rate is maintained at 0.05-0.15m / s by a circulating pump during the soaking process. After soaking, the sample blank is lifted out of the soaking tank at a speed of 10-30mm / s and allowed to stand and drip for 2-5 minutes, leaving only a thin liquid film covering it.

[0013] As a preferred improvement, the relative humidity during secondary curing is maintained at 95%-100% for 6-18 hours. During the secondary curing process, a controllable process of gradually increasing the temperature, then maintaining a constant temperature, and finally gradually decreasing the temperature is adopted: first, preheat at 35-45℃ for 10-15 minutes, then increase the temperature at 0.5-1.0℃ / min to the target 50-60℃ and maintain the temperature for 6-12 hours, then slowly decrease the temperature at 0.5-1.0℃ / min to 35-40℃ and maintain the temperature for 30-60 minutes before removing it from the room. The endpoint of secondary maintenance is determined by a comprehensive assessment of the following indicators: The product quality gain rate is ≤0.1% / h, the total inorganic carbon growth rate in the solution is reduced to ≤0.5mmol / L·h, the surface phenolphthalein color change depth is 1-3mm and stable, and there is no blooming on the appearance.

[0014] As a preferred improvement, step S5 is followed by the following steps: Step S6: When the CO2 loading of the compound amine solution in the soaking tank exceeds 0.40 mol CO2 / mol compound amine or the pH drops below 9.3, the compound amine solution is transferred to the regeneration system and regenerated using air or nitrogen as the stripping medium. This process restores the pH of the compound amine solution to 10.2-10.8 and reduces the CO2 loading to 0.10-0.20 mol CO2 / mol compound amine. After regeneration, the solution is cooled to 25-35°C for reuse.

[0015] A composite geopolymer material is prepared by the above-mentioned method for preparing composite geopolymer materials. The open porosity of the composite geopolymer material is 5%-18%, the compressive strength at 28 days is ≥40MPa, the mass loss after 50 freeze-thaw cycles is ≤1.0%, and the linear shrinkage is ≤0.05%.

[0016] An application of the composite geopolymer material as described above is used to prepare geopolymer decorative panels, which include wall tiles and countertops.

[0017] The beneficial effects of this invention are as follows: (1) Coal gangue powder, as a silicon-aluminum-containing solid waste with abundant reserves, can be used as a major silicon-aluminum precursor after low-temperature roasting or fine grinding and activation, realizing the resource utilization of bulk solid waste; the black liquor ash of papermaking is rich in soluble alkaline oxides such as Na2O and K2O, which can rapidly release OH after being mixed with water. - It also increases the pH of the system, thereby stimulating the dissolution of SiO2 and Al2O3 in the coal gangue powder to participate in condensation, replacing traditional external strong alkali activators such as NaOH and Na2SiO3, significantly reducing corrosivity, transportation hazards and costs, while avoiding the discharge of high-alkali waste liquid; (2) CO2-rich solution is prepared by capturing CO2 in industrial tail gas using a composite amine solution. This solution is then used to wet-soak and heat-cur the geopolymer material at medium and low temperatures, allowing CO2 to be released uniformly and slowly within the pores. Compared with direct carbonization of gas-phase CO2, this method avoids surface acidification and the formation of a carbon shell. CO2 can penetrate deep into the material and react gradually with pore liquid ions to generate submicron to micron-sized carbonate crystals that fill the pore walls, improving the uniformity of the pore structure and the density of the surface layer. This effectively inhibits ion migration and efflorescence, ensuring the decorative effect and durability of the geopolymer decorative panel. Furthermore, the composite amine solution is recyclable, with mild regeneration conditions (100-120℃), high CO2 release efficiency, and low solution loss. This forms a closed-loop circulation system of CO2-amine solution-geolithic material decorative panel, which not only improves the utilization rate of amine solution and reduces operating costs, but also realizes the large-scale resource utilization and solidification of CO2, achieving both carbon emission reduction and environmental benefits. (3) Traditional geopolymer decorative panels require 7-28 days to achieve stable performance under normal temperature or dry heat conditions, while the present invention only requires 6-18 hours of moist heat curing to obtain surface density and strength comparable to or even higher than the 28-day control group, shortening the curing cycle and improving mechanical properties. The compressive strength of the manufactured geopolymer decorative panels can reach 25-40 MPa after 7 days, and the compressive strength after 28 days exceeds 40 MPa. The flexural strength reaches more than 9 MPa, the water absorption rate is reduced to 4-6%, and the mass loss rate after 50 freeze-thaw cycles is ≤1.0%, which significantly improves durability and dimensional stability. (4) By making full use of industrial solid waste and industrial exhaust gas, the high-value resource utilization and carbon capture and utilization of multi-source waste have been realized. The preparation process has low energy consumption and high safety. The prepared geopolymer decorative board products have excellent performance, dense appearance and polishable appearance. It has significant technological progress, industrialization promotion value and environmental benefits. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] This embodiment provides a method for preparing a composite geopolymer material, including the following steps: Step S1: Mix 10-30 parts of papermaking black liquor ash, 55-80 parts of coal gangue powder, 0-10 parts of silicon compensation source and 0-10 parts of inert filler evenly according to the mass ratio, add water at a water-binder ratio of 0.28-0.40 and stir to form a geopolymer slurry.

[0020] Papermaking black liquor ash originates from the alkali recovery system of the pulp and paper industry. It contains a large amount of Na2O (5-20wt%), K2O (1-8wt%), CaO, MgO, and some Na2CO3, Na2SO4, NaOH, etc. It has high soluble alkalinity and a strength equivalent to 1-5% of an externally added NaOH solution, making it suitable as an embedded alkali activator for geopolymer materials. The fine particles and large specific surface area of ​​papermaking black liquor ash make it highly hygroscopic and soluble. Direct storage poses problems of leachate and dust pollution. This invention utilizes it as a high-value alkali source.

[0021] Papermaking black liquor ash is dried at 95-115℃ for 3-6 hours to constant weight, ensuring a moisture content of less than 0.5%, and then passed through a 200-mesh sieve to eliminate lumps and large particles, ensuring a uniform dissolution rate.

[0022] Coal gangue powder is obtained by directly finely grinding unsintered coal gangue powder or by finely grinding it after low-temperature roasting. As a byproduct of coal mining, coal gangue powder is mainly composed of kaolinite, illite, quartz, and feldspar, with an Al2O3 content typically of 20%-35% and a SiO2 content of 45%-60%. Unsintered coal gangue powder has low activity, but its activity is significantly improved by grinding it to a D50 of 8-25 μm or by low-temperature roasting at 600-800℃ to transform it into metakaolinite. It can dissolve reactive Si and Al units in an alkaline environment. Specifically, the unsintered coal gangue powder is ball-milled to a D50 of 8-25 μm, or it is roasted at 600-800℃ for 1-2 hours and then ground to a D50 of 8-25 μm to activate its activity. If necessary, ≤10% fine waste glass or ceramic slag can be added as an additional silicon source.

[0023] The pretreated black liquor ash from papermaking and coal gangue powder must be stored in sealed containers to prevent moisture absorption.

[0024] The silicon compensation source is selected as waste glass fine powder or ceramic waste slag fine powder.

[0025] The principle for raw material proportioning is: the equivalent alkali of the total system should be controlled at 1.5%-5.0% Na₂Oeq. Alkali can be added to the black liquor ash from papermaking to recover furnace ash and adjust the Na / K ratio and impurity levels.

[0026] Step S2: Prepare sample blanks using geopolymer slurry and perform a curing process.

[0027] The sample blank can be formed using casting or low-pressure pressing. During casting, fill the mold cavity to 95%-100% and gently vibrate for 10-20 seconds to remove large air bubbles. During pressing, control the pressure at 10-25 MPa and hold for 10-30 seconds. The initial curing conditions are 25-35℃ and relative humidity ≥95%, lasting 4-8 hours, allowing the geopolymer slurry to complete initial setting and partial condensation, forming a sufficient porous network to facilitate subsequent CO2-rich liquor infiltration, while preventing surface bleeding and early cracking.

[0028] Step S3: Prepare a composite amine solution with a mass fraction of 20%-40% for MDEA, a mass fraction of 2%-6% for PZ, and the remainder being deionized water; pass the CO2-containing industrial furnace tail gas into the composite amine solution to adsorb CO2 and form a CO2-rich solution.

[0029] In the composite amine solution, MDEA (methyldiethanolamine) is a tertiary amine with good selectivity, low vapor pressure, and low regeneration energy consumption; PZ (piperazine) is a strongly basic diamine with high reactivity and fast absorption rate. The composite amine solution formed by the combination of the two has both high CO2 loading capacity and excellent absorption kinetics. The mass fraction of MDEA in the composite amine solution is 20-40%, and the mass fraction of PZ is 2-6%, with a CO2 loading of 0.25-0.50 mol CO2 / mol composite amine. When absorbing industrial exhaust gas, a CO2-rich solution is formed. Heating to 50-70℃ allows for controlled CO2 release. Simultaneously, the solution has a certain buffering alkalinity and surface wettability, making it suitable for wet soaking and curing.

[0030] The volume fraction of CO2 in the exhaust gas of industrial furnaces and kilns is 8-20%. During the adsorption of CO2 by the composite amine solution, the temperature is controlled at 35-50℃, and the liquid-to-gas ratio is 1.5-3.0 L / Nm³. 3 The process continues until the CO2 loading α of the solution reaches 0.30-0.40 mol CO2 / mol composite amine. At this point, the pH of the CO2-rich solution is between 9.5 and 10.5, possessing both CO2 loading and buffering alkalinity. After cooling to 25-35℃ and filtering to remove impurities, it is stored for later use. To prevent amine mist loss, the CO2-rich solution preparation system must be equipped with a condenser and a water washing tower, and the amine content in the exhaust gas must be controlled to ≤5 mg / Nm³. 3 .

[0031] Step S4: Place the CO2-rich solution in the soaking tank and immerse the sample blank after the first curing process into the soaking tank.

[0032] During the soaking process, the liquid-to-solid volume ratio should be controlled at 3:1-5:1, the liquid temperature at 25-35℃, and the soaking time at 10-45 minutes. During soaking, maintain the tank solution flow rate at 0.05-0.15 m / s using a circulating pump to avoid dead zones and promote uniform penetration of the CO2-rich solution into the capillaries. To prevent excessive ion dissolution, the pH and conductivity of the tank solution should be monitored in real time. If the conductivity increases by more than 15% of the initial value, the soaking time should be shortened or the flow rate reduced. After soaking, lift the sample blank out of the soaking tank at a speed of 10-30 mm / s and allow it to drip for 2-5 minutes, leaving only a thin liquid film covering it.

[0033] The immersion tank can be a batch tank, a roller coating tank, or a continuous spray immersion production line. When the thickness of the sample blank is ≥15mm, a two-stage immersion method can be used, that is, immersing once with a low-concentration CO2-rich solution and once with a high-concentration CO2-rich solution. Specifically, first immerse briefly with a low-concentration CO2-rich solution (e.g., 10-15min) to achieve surface wetting and initial penetration, and then immerse deeply with a high-concentration CO2-rich solution (e.g., 20-30min) to enhance the deep CO2 supply and carbonate formation.

[0034] Step S5: Place the soaked sample blank in a sealed humid heat curing chamber for secondary curing. After the secondary curing is completed, the finished geopolymer material is obtained.

[0035] For the second curing, maintain a relative humidity of 95%-100% for 6-18 hours.

[0036] In a closed, humid heat curing chamber, CO2-rich solution gradually releases CO2 into the pores of the sample blank. CO2 absorbed in the composite amine solution exists in the form of bicarbonate / carbonate and amine-carbonate; this absorption process is reversible: the solution can release CO2 under conditions of increased temperature, dilution, or reduction of CO2 partial pressure. During secondary humid heat curing, temperature and chemical gradients promote the desorption of CO2 from the rich solution / film and its diffusion into the blank pores, where it reacts with Ca... 2+ Mg 2+ The alkaline components react to form carbonates, which fill the pores and form micro-anchoring structures. Meanwhile, during the secondary curing process, the high pH maintained by the system is mainly buffered by the complex amine (residual MDEA / PZ) and the soluble alkali (Na2Oeq, NaOH / Na2CO3, etc. provided by the black liquor ash) built into the blank, preventing the surface from being acidified or forming a dense carbonized shell.

[0037] During the secondary curing process, a controlled process of gradually increasing temperature, maintaining a constant temperature, and then gradually decreasing temperature is adopted: first, preheat at 35-45℃ for 10-15 minutes, then increase the temperature at 0.5-1.0℃ / min to the target 50-60℃ and maintain the temperature for 6-12 hours, then slowly decrease the temperature at 0.5-1.0℃ / min to 35-40℃ and maintain the temperature for 30-60 minutes before removing from the chamber; for thick plates or systems requiring stronger densification, the insulation temperature can be appropriately increased to 60-65℃ and the insulation time extended. Humidity control is crucial to prevent shrinkage cracks caused by capillary water evaporation. The endpoint of the secondary curing is determined by a comprehensive assessment of the following indicators: the plate quality gain stabilizes (growth rate ≤ 0.1% / h), the growth rate of total inorganic carbon (TIC) in the solution decreases to ≤ 0.5 mmol / L·h, the surface phenolphthalein discoloration depth is stable at 1-3 mm, and there is no blooming on the surface.

[0038] After the second curing, spray the sample with clean water or diluted lean solution at 30-40℃ for 0.5-2 minutes to remove residual amine solution on the surface, and then let it drip dry naturally or dry it with warm air at 35-45℃ for 5-10 minutes.

[0039] Furthermore, if used as a high-end decorative panel, the prepared sample can be subjected to progressive grinding and polishing (240 mesh → 600 mesh → 1200 mesh → 2000 mesh) to obtain a bright and smooth surface; then, 0.2%-0.8% of an organosilicon water-repellent agent is sprayed to seal the surface micropores and improve the anti-fouling and anti-seepage performance.

[0040] Step S5 is followed by the following steps: Step S6: When the CO2 loading of the compound amine solution in the soaking tank exceeds 0.40 mol CO2 / mol compound amine or the pH drops below 9.3, the compound amine solution is transferred to the regeneration system and regenerated using air or nitrogen as the stripping medium. This process restores the pH of the compound amine solution to 10.2-10.8 and reduces the CO2 loading to 0.10-0.20 mol CO2 / mol compound amine. After regeneration, the solution is cooled to 25-35°C for reuse.

[0041] The temperature conditions during the regeneration process are 100-120℃, and the flow rate of the stripping medium is 0.8-1.5 Nm³. 3 / h·m 3 Solution. The CO2 released during the regeneration process can be recycled.

[0042] To prevent particle accumulation, a solid-liquid separation unit is required during the regeneration process, such as using a 5-10μm filter to ensure suspended solids ≤10mg / L and turbidity ≤5NTU. Fresh MDEA and PZ are periodically added based on material balance to maintain solution stability.

[0043] This embodiment also provides a composite geopolymer material, which is prepared using the above-described method for preparing composite geopolymer materials.

[0044] This embodiment also provides an application of the above-mentioned composite geopolymer material for preparing geopolymer decorative panels. These panels can be used as ordinary architectural decorative components, such as wall tiles and countertops. Furthermore, before polishing, the geopolymer decorative panels can be filled with mineral pigments or colored glass powder to form colored decorative panels, further enriching their surface appearance.

[0045] Testing revealed that the dry density of the geopolymer decorative board produced by this invention is 1.20-1.90 g / cm³. 3 The open porosity is 5%-18%, the 24-hour water absorption rate is ≤6%, the 7-day flexural strength is ≥6MPa, and the 28-day flexural strength is ≥9MPa; the 7-day compressive strength is ≥25MPa, and the 28-day compressive strength is ≥40MPa. After 50 freeze-thaw cycles, the mass loss is ≤1.0%, and the linear shrinkage is ≤0.05%. Compared with traditional dry heat curing, this process can achieve the same apparent density and mechanical properties as 28 days within 6-18 hours, shortening the curing cycle by more than 70%.

[0046] After polishing, the surface gloss is increased by 10-20 GU, the surface electrical flux is reduced by 20%-40%, and the anti-blooming ability is improved by one level.

[0047] The preparation method of the composite geopolymer material provided by the present invention will be described in detail below with reference to specific embodiments.

[0048] Example 1 In this embodiment, unsintered coal gangue was selected, ball-milled to D50=18μm for activation treatment, and then mixed with papermaking black liquor ash and CRT waste glass powder as raw materials, with a ratio of 70wt% coal gangue powder, 20wt% papermaking black liquor ash, and 10wt% CRT waste glass powder. After pretreatment, the raw materials were mixed evenly. The Na2Oeq content in the papermaking black liquor ash was approximately 12wt%, and the equivalent alkali equivalent of the system was 3.0%.

[0049] All raw material powders were dry-mixed in a planetary mixer for 1 minute, then water was added in two batches, with the water-to-binder ratio controlled at 0.35. After mixing, the geopolymer slurry had a pH of 10.6, and its fluidity met the casting requirements. The geopolymer slurry was poured into a 400×400×10mm mold, gently vibrated for 15 seconds to release air, and the surface was smooth. The sample was cured in a humid chamber at 30℃ and relative humidity ≥95% for 6 hours before demolding.

[0050] A complex amine solution was prepared with a ratio of 30 wt% MDEA, 5 wt% PZ, and the remainder being deionized water. This complex amine solution was used to absorb CO2-containing (12% by volume) industrial kiln exhaust gas to produce a CO2-rich solution. The absorption temperature was 40℃, and the liquid-to-gas ratio was 2.0 L / Nm³. 3 The CO2 loading was increased until the CO2 loading α = 0.35 mol CO2 / mol composite amine and the pH of the enriched solution was 9.8. The CO2-rich solution was filtered through a 10 μm filter and cooled to 30 °C for later use.

[0051] The sample blank was immersed in a CO2-rich solution for 30 minutes, with a liquid-to-solid ratio of 4:1 and a solution temperature of 30°C. After being lifted out of the immersion tank, the sample was dripped for 3 minutes, forming a thin film on the surface. It was then placed in a humid heat chamber, initially kept at a constant temperature of 45°C for 15 minutes, and then linearly increased to 60°C at a rate of 1.0°C / min (taking 15 minutes). After reaching 60°C, the temperature was kept constant, making the total curing time (including the heating period) 12 hours, with a relative humidity of 98%. After curing for 12 hours, the finished product 1 was obtained.

[0052] Test results show that the 7-day compressive strength of finished product 1 is 28 MPa, which is 35% higher than the control without CO2 wet curing; the 28-day compressive strength is 42 MPa, and the flexural strength reaches 10.5 MPa. The water absorption rate is 5.2%, and the open porosity is 6.8%. The phenolphthalein discoloration depth on the surface is ≤1.8 mm, and the electrical flux is 32% lower than the control without CO2 wet curing. There is no blooming on the surface, and the gloss after polishing is 18 GU higher than the control without CO2 wet curing. After 50 freeze-thaw cycles, the mass loss rate is 0.9%, and the dimensional shrinkage rate is 0.035%, indicating excellent performance. The surface is dense and smooth after polishing, meeting the requirements of high-end decorative panels.

[0053] Example 2 In this embodiment, coal gangue was calcined at 700℃ for 2 hours and then ground to a D50 of 12 μm to obtain metakaolinite-phase active powder. Papermaking black liquor ash was dried at 105℃ for 5 hours and passed through a 200-mesh sieve. Waste glass powder from fluorescent tubes was ball-milled to a D50 of 15 μm. Using the above three materials as raw materials, the proportions were: 60 wt% calcined coal gangue powder, 25 wt% papermaking black liquor ash, and 15 wt% waste glass powder. The Na2Oeq content of the papermaking black liquor ash was 12 wt%; the equivalent alkali equivalent of the system was 4.0%.

[0054] All raw materials were premixed into powder form, then water was added and stirred. The water-to-binder ratio was 0.30, the geopolymer slurry pH was 10.9, and the viscosity was moderate. The geopolymer slurry was pressed into 300×300×12mm boards at a pressing pressure of 15MPa for 20 seconds. After molding, the boards were cured in a humid chamber at 35℃ and relative humidity ≥97% for 4 hours.

[0055] A complex amine solution was prepared with a ratio of 25 wt% MDEA, 4 wt% PZ, and the remainder being deionized water. This complex amine solution was used to absorb CO2-containing (15% by volume) industrial kiln exhaust gas to produce a CO2-rich solution. The absorption temperature was 40℃, and the liquid-to-gas ratio was 2.0 L / Nm³. 3 The CO2 loading was increased until the CO2 loading α = 0.40 mol CO2 / mol composite amine and the pH of the rich solution was 9.7. The CO2 rich solution was then filtered through a 10 μm filter and cooled to 28 °C for later use.

[0056] The sample was immersed in a CO2-rich solution for 20 minutes at a liquid-to-solid ratio of 3.5:1 and a solution temperature of 28°C. After removal, it was dripped for 5 minutes and then cured in a humid heat chamber at 50°C and 99% relative humidity for 16 hours to obtain product 2.

[0057] Performance testing results show that: the 7-day compressive strength of finished product 2 is 32 MPa, which is 42% higher than the control without CO2 wet curing; the 28-day compressive strength is 45 MPa, and the flexural strength is 11.3 MPa. The water absorption rate is 4.0%, and the open porosity is 7.5%. The phenolphthalein discoloration depth on the surface is ≤2 mm, and the electrical flux is 38% lower than the control without CO2 wet curing; there is no blooming on the surface, and the gloss after polishing is 20.5 GU higher than the control without CO2 wet curing. After 50 freeze-thaw cycles, the mass loss rate is 0.8%, the dimensional shrinkage rate is 0.04%, and the surface is dense and smooth after polishing, meeting the requirements of high-end decorative panels.

[0058] Example 3 In this embodiment, unsintered coal gangue was selected, ball-milled to D50=20μm, and mixed with alkali recovery furnace ash and waste glass powder as raw materials. The ratio was: 65wt% coal gangue powder, 25wt% alkali recovery furnace ash, and 10wt% waste glass powder. The Na2Oeq content of the alkali recovery furnace ash was 10.5wt%, and the equivalent alkali equivalent of the system was 3.5%.

[0059] After mixing all the raw materials into powder evenly, add water at a water-to-binder ratio of 0.33 and stir. The pH of the geopolymer slurry is 10.7, and the fluidity meets the casting requirements. Pour the geopolymer slurry into a 300×300×15mm mold, gently vibrate for 15 seconds to remove air, and the surface is smooth. The sample is then demolded after curing for 5 hours in an environment of 30℃ and relative humidity ≥96%.

[0060] A complex amine solution was prepared with the following ratio: 30 wt% MDEA, 5 wt% PZ, and the remainder deionized water. This complex amine solution was used to absorb CO2-containing (12% by volume) industrial kiln exhaust gas to produce a CO2-rich solution. The absorption temperature was 40℃, and the liquid-to-gas ratio was 2.2 L / Nm³. 3 The CO2 loading was increased until the CO2 loading α = 0.38 mol CO2 / mol composite amine and the pH of the enriched solution was 9.9. The CO2-rich solution was filtered through a 10 μm filter and cooled to 30°C for later use.

[0061] The sample was immersed in CO2-rich solution for 25 minutes at a liquid-to-solid ratio of 4:1. After being removed and dripped for 3 minutes, it was cured at 55°C and 98% relative humidity for 14 hours.

[0062] After maintenance, the pH of the CO2-rich solution decreased to 9.2, the loading rate increased to 0.45 mol CO2 / mol composite amine, and the solution's absorption capacity was significantly reduced.

[0063] The CO2-rich solution was transferred to the regeneration system, where it was heated to 110°C. Nitrogen gas was then introduced as the stripping medium at a flow rate of 1.0 Nm³. 3 / h·m 3 Solution. After 1.5 hours of regeneration, the CO2 loading decreased from 0.45 mol CO2 / mol composite amine to 0.15 mol CO2 / mol composite amine, and the pH of the CO2-rich solution recovered to 10.5. After condensation and moisture recovery of the gas at the top of the regeneration tower, the CO2 collection volume was 28 kg, equivalent to the net solids of eight 300×300×15 mm decorative panels. The regenerated CO2-rich solution was cooled to 30°C and reused for the curing of the next batch of panels.

[0064] The curing effect of regenerated CO2-rich solution was verified as follows: The second batch of decorative panels (prepared with the same ratio) were soaked in regenerated CO2-rich solution for 20 minutes and cured under the conditions of 55℃, 99% relative humidity, for 12 hours. Performance tests showed that the 7-day compressive strength was 29 MPa, which was 30% higher than that of the conventional wet-cured control; the 28-day compressive strength was 43 MPa, the water absorption rate was 5.0%, the phenolphthalein discoloration depth on the surface was 2 mm, and there was no blooming; after 50 freeze-thaw cycles, the mass loss rate was 0.9%, which was comparable to the performance of the first use of CO2-rich solution.

[0065] Through material balance calculations, every 1m 3 Within an operating window of α = 0.15-0.45 mol CO2 / mol composite amine, the composite amine solution can complete the curing of approximately 3 batches (24 panels in total), with a regeneration energy consumption of approximately 0.9 GJ / t-CO2, which is about 20% lower than that of the conventional MEA system. The solution loss is less than 1.5%, and only 0.5% MDEA and 0.2% PZ need to be added to maintain stable operation.

[0066] The results show that the composite amine solution in the process of this invention can be recycled and reused multiple times, ensuring the stability of the CO2-rich wet curing effect, significantly reducing operating costs, and realizing a closed-loop cycle of CO2 capture—building material curing—CO2-rich solution regeneration, which has both economic and environmental benefits.

[0067] The embodiments of the present invention have been described above, but the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit of the present invention, and all of these forms are within the protection scope of the present invention.

Claims

1. A method for preparing a composite geopolymer material, characterized in that, Includes the following steps: Step S1: Mix 10-30 parts of papermaking black liquor ash, 55-80 parts of coal gangue powder, 0.5-10 parts of silicon compensation source and 0.5-10 parts of inert filler evenly according to the mass ratio, add water at a water-binder ratio of 0.28-0.40 and stir to form a geopolymer slurry. Step S2: Prepare sample blanks using geopolymer slurry and perform a curing process; Step S3: Prepare a composite amine solution. The mass fraction of methyldiethanolamine in the composite amine solution is 20%-40%, the mass fraction of piperazine is 2%-6%, and the remainder is deionized water. Pass the tail gas of the industrial furnace containing CO2 into the composite amine solution to adsorb CO2 and form a CO2-rich solution. Step S4: Place the CO2-rich solution in the soaking tank and immerse the sample blank after the first curing process into the soaking tank. Step S5: Place the soaked sample blank in a sealed humid heat curing chamber for secondary curing. After the secondary curing is completed, the finished geopolymer material is obtained.

2. The method for preparing the composite geopolymer material according to claim 1, characterized in that, The black liquor ash from papermaking shall contain at least the following components: 5-20 wt% Na2O and 1-8 wt% K2O; the coal gangue powder shall contain at least the following components: 20-35 wt% Al2O3 and 45-60 wt% SiO2. Papermaking black liquor ash is dried at 95-115℃ for 3-6 hours to constant weight, ensuring a moisture content of less than 0.5%, and then passed through a 200-mesh sieve to eliminate lumps and large particles. Coal gangue powder is obtained by directly fine grinding unsintered coal gangue powder or by fine grinding after low-temperature calcination. Specifically, unsintered coal gangue powder is directly ball-milled to a D50 of 8-25μm, or it is calcined at 600-800℃ for 1-2 hours and then ground to a D50 of 8-25μm.

3. The method for preparing the composite geopolymer material according to claim 2, characterized in that, The silicon compensation source is selected as waste glass fine powder or ceramic waste residue fine powder; the inert filler is selected from one or more of quartz powder, limestone powder, feldspar powder and kaolin calcination residue.

4. The method for preparing the composite geopolymer material according to claim 1, characterized in that, The sample blank can be formed by casting or low-pressure pressing.

5. The method for preparing the composite geopolymer material according to claim 1, characterized in that, The volume fraction of CO2 in the exhaust gas of industrial furnaces and kilns is 8-20%. During the adsorption of CO2 by the composite amine solution, the temperature is controlled at 35-50℃, and the liquid-to-gas ratio is 1.5-3.0 L / Nm³. 3 The solution is kept in a CO2 loading α until it reaches 0.30-0.40 mol CO2 / mol composite amine and the pH of the CO2-rich solution is between 9.5 and 10.

5. Then the CO2-rich solution is cooled to 25-35℃ and filtered to remove impurities before being stored for later use.

6. The method for preparing the composite geopolymer material according to claim 1, characterized in that, During the soaking process in step S4, the liquid-to-solid volume ratio is controlled at 3:1-5:1, the liquid temperature is 25-35℃, the soaking time is 10-45 minutes, and the liquid flow rate is maintained at 0.05-0.15m / s by a circulating pump during the soaking process. After soaking, the sample blank is lifted out of the soaking tank at a speed of 10-30mm / s and allowed to stand and drip for 2-5 minutes, leaving only a thin liquid film covering it.

7. The method for preparing the composite geopolymer material according to claim 1, characterized in that, The relative humidity for secondary curing should be maintained at 95%-100% for 6-18 hours. During the secondary curing process, a controllable process of gradually increasing the temperature, then maintaining a constant temperature, and finally gradually decreasing the temperature should be adopted: first, preheat at 35-45℃ for 10-15 minutes, then increase the temperature at 0.5-1.0℃ / min to the target 50-60℃ and maintain the temperature for 6-12 hours, then slowly decrease the temperature at 0.5-1.0℃ / min to 35-40℃ and keep it at that temperature for 30-60 minutes before removing it from the room. The endpoint of secondary maintenance is determined by a comprehensive assessment of the following indicators: The product quality gain rate is ≤0.1% / h, the total inorganic carbon growth rate in the solution is reduced to ≤0.5mmol / L·h, the surface phenolphthalein color change depth is 1-3mm and stable, and there is no blooming on the appearance.

8. The method for preparing the composite geopolymer material according to claim 1, characterized in that, Step S5 is followed by the following steps: Step S6: When the CO2 loading of the compound amine solution in the soaking tank exceeds 0.40 mol CO2 / mol compound amine or the pH drops below 9.3, the compound amine solution is transferred to the regeneration system and regenerated using air or nitrogen as the stripping medium. This process restores the pH of the compound amine solution to 10.2-10.8 and reduces the CO2 loading to 0.10-0.20 mol CO2 / mol compound amine. After regeneration, the solution is cooled to 25-35°C for reuse.

9. A composite geopolymer material, characterized in that, The composite geopolymer material is prepared by the preparation method of any one of claims 1-8. The open porosity of the composite geopolymer material is 5%-18%, the compressive strength at 28 days is ≥40MPa, the mass loss after 50 freeze-thaw cycles is ≤1.0%, and the linear shrinkage is ≤0.05%.

10. An application of the composite geopolymer material as described in claim 9, characterized in that, Used to prepare geopolymer decorative panels, which include wall tiles and countertops.