Surface carbonation modified high-strength deliquescence-resistant calcium-based CO2 adsorbent as well as preparation and application thereof

Abstract

The invention relates to a surface carbonation modified high-strength deliquescence-resistant calcium-based CO2 adsorbent as well as preparation and application thereof, and belongs to the field of CO2 trapping. The invention develops a surface carbonation modified high-strength deliquescence-resistant calcium-based CO2 adsorbent and a preparation method thereof. A compact and hard CaCO3 shell layer is formed on the surface layer of CaO particles in situ through controllable carbonation reaction, deliquescence resistance and mechanical strength are effectively considered, the problem that a traditional calcium-based adsorbent is prone to breakage in a humid environment is effectively solved, and meanwhile the two key indexes of high mechanical strength and high adsorption performance are also considered.

Description

Technical Field

[0001] This invention relates to the field of CO2 capture, and more specifically, to a high-strength, deliquescent-resistant calcium-based CO2 adsorbent with surface carbonation modification, its preparation and application. Background Technology

[0002] Carbon dioxide capture, utilization, and storage (CCUS) is considered a crucial technological approach supporting large-scale emission reduction. As a typical post-combustion capture scheme within the CCUS system, "Calcium Looping (CaL)" uses CaO as a carrier to capture CO2 from combustion exhaust gases, offering advantages such as mature technology and readily available raw materials. To meet engineering application requirements, calcium-based adsorbents typically need to be prepared in granular form to suit production, transportation, and storage processes. Furthermore, the adsorbent particles must possess good mechanical strength to prevent increased washing losses and reactor blockage due to wear and breakage during the cycle, ensuring the long-term stable operation of the calcium loop system.

[0003] However, CaO particles readily react with water in humid air to form Ca(OH)₂, leading to hygroscopic expansion and structural damage. This manifests macroscopically as deliquescence phenomena such as strength reduction, cracking, and pulverization, thus affecting subsequent recycling performance and storage and transportation stability. To address these technical problems, this invention constructs a continuous and dense CaCO₃ shell on the outer layer of the particles through controlled surface carbonation. This achieves dual suppression of water vapor diffusion and interfacial reactions without altering the core function of the CaO particles. This strategy aims to improve the material's resistance to deliquescence and mechanical strength, providing a more reliable material basis for the engineering application of calcium recycling processes in power plants, cement plants, steel plants, and mobile sources.

[0004] While some studies have attempted to enhance the anti-breakage properties of CaO particles by doping them with inert framework materials (such as cement, alumina, and silica), these methods typically only delay particle breakage and do not fundamentally solve the problem of CaO's hygroscopic expansion and breakage. Furthermore, some studies have proposed using alumina or silica to form a shell structure, thereby blocking water vapor from eroding the CaO particles. Although this method addresses the hygroscopic expansion and breakage issues to some extent, the coating layer relies primarily on physical bonding, resulting in weak adhesion and easy detachment, leading to structural failure. Simultaneously, both of these methods reduce the content of free calcium oxide in the adsorbent particles, thus affecting their CO2 adsorption performance. Summary of the Invention

[0005] This invention generates a dense CaCO3 coating layer on the surface of the formed adsorbent particles through a controllable directional carbonation reaction, thereby constructing an effective barrier interface against water molecules and inhibiting the penetration and reaction of water vapor into the CaO core. This significantly reduces the deliquescence problems caused by the hygroscopic hydration of CaO particles in humid environments, such as volume expansion, cracking, and powdering.

[0006] According to a first aspect of the present invention, a method for preparing a surface-carbonated modified, strength-enhanced, deliquescent-resistant calcium-based CO2 adsorbent is provided, comprising the following steps: (1) CaO particles are reacted with CO2 gas or CaO particles are reacted with a mixture of gas containing CO2 at a temperature of 550℃-750℃, wherein the mixture does not contain any acidic gas other than CO2, and the CaO particles undergo a carbonation reaction with CO2 to form a CaCO3 coating layer. (2) The particles with CaCO3 coating obtained in step (1) are naturally cooled in a non-purged, non-oxidizing atmosphere to avoid structural stress cracking caused by rapid cooling, thus obtaining a surface carbonization modified calcium-based CO2 adsorbent with improved strength and resistance to deliquescence.

[0007] Preferably, in step (1), the temperature condition is 600℃-650℃.

[0008] Preferably, in step (1), the volume concentration of CO2 in the CO2-containing mixed gas is greater than or equal to 10%.

[0009] Preferably, the mixed gas contains at least one of N2, Ar and O2 in addition to CO2.

[0010] Preferably, the reaction time is 5 min to 20 min.

[0011] Preferably, the reaction time is 10 min to 20 min.

[0012] According to another aspect of the present invention, a surface-carbonated modified calcium-based CO2 adsorbent with improved strength and resistance to deliquescence is provided by a preparation method.

[0013] According to another aspect of the present invention, the application of the surface-carbonated modified, strength-enhanced, deliquescent-resistant calcium-based CO2 adsorbent in CO2 capture is provided.

[0014] Preferably, the CaCO3 coating layer on the surface of the surface-carbonated modified, strength-enhanced, deliquescent calcium-based CO2 adsorbent is interconnected with calcium oxide through chemical bonds, so that the CaCO3 coating layer can effectively block the contact between humid air and calcium oxide particles, thereby inhibiting the water absorption and swelling of the adsorbent particles and improving the deliquescent resistance of the adsorbent particles.

[0015] In summary, compared with the prior art, the above-described technical solutions conceived by this invention mainly possess the following technical advantages: (1) This invention develops a high-strength, deliquescent-resistant calcium-based CO2 adsorbent with surface carbonation modification and its preparation method. This invention achieves a dense CaCO3 shell layer in situ on the surface of CaO particles through a controlled carbonation reaction between calcium oxide particles and carbon dioxide gas, effectively balancing deliquescent resistance and mechanical strength. This invention not only effectively overcomes the problem of traditional calcium-based adsorbents being easily broken in humid environments, but also balances the two key indicators of high mechanical strength and high adsorption performance, possessing good industrial application prospects and promotional value. It significantly improves the mechanical stability of calcium-based adsorbents during production, transportation, storage, and use, meeting the performance requirements of high-energy-consuming industries such as thermal power, steel, cement, and transportation for CO2 capture materials.

[0016] (2) This invention develops a high-strength, deliquescent-resistant calcium-based CO2 adsorbent modified by surface carbonation and its preparation method. This invention uses a controlled carbonation reaction to directionally generate a dense CaCO3 coating layer on the surface of shaped CaO adsorbent particles, constructing an effective barrier interface against water molecules, inhibiting the penetration and reaction of water vapor into the CaO core, and improving the deliquescent resistance of the CaO adsorbent particles. The innovations of this invention are as follows: 1) A dense calcium carbonate shell is constructed in situ on the outside of calcium oxide particles through a controlled carbonation reaction. This calcium carbonate shell effectively blocks the contact between humid air and calcium oxide particles, inhibiting water absorption and swelling of the adsorbent particles from the source, and significantly improving the deliquescent resistance of the particles in humid environments; 2) The dense calcium carbonate coating layer and calcium oxide are connected by chemical bonds rather than physical adhesion, avoiding the risk of easy detachment of the coating layer and ensuring the durability and reliability of the protective function. Meanwhile, the dense calcium carbonate coating structure also significantly improves the overall mechanical strength of the particles and extends the service life of the material; 3) The adsorbent particles prepared by this method are mainly composed of calcium carbonate and calcium oxide. During the cyclic carbon capture process, the free calcium oxide content is relatively high, which can improve the CO2 capture performance of the adsorbent and achieve a dual improvement in CO2 adsorption efficiency and deliquescence resistance.

[0017] (3) The main technical problem to be solved by this invention is to improve the deliquescence resistance of calcium-based adsorbent particles in humid environments. In the CO2 capture application of calcium-based adsorbent particles, the particles are often exposed to humid air, causing the particles to react with moisture, resulting in volume expansion, structural cracking and pulverization, which seriously affects their mechanical strength and recyclability. At present, although common inert framework doping methods can delay particle cracking to a certain extent, they often cannot fundamentally solve the damage caused by moisture absorption and expansion, especially during long-term storage and transportation of particles, which still face a high risk of deactivation. In addition, although using materials such as alumina and silicon oxide to construct a coating layer on the particle surface can effectively block moisture penetration and thus improve the deliquescence resistance of the particles, this coating layer mainly relies on physical methods to bond with the particles, and the bonding force is weak and easy to fall off, resulting in structural failure and loss of protective function. At the same time, the presence of these inert frameworks or coating layers will also reduce the content of free calcium oxide in the adsorbent particles, thereby leading to a decrease in their CO2 adsorption capacity. It is evident that existing technologies still struggle to balance the moisture-proof stability and high adsorption performance required for adsorbents in applications. This bottleneck severely restricts the large-scale engineering application of calcium-based adsorbents in CCUS systems.

[0018] (4) While traditional physical coating methods (such as coating with silica or alumina) can isolate humid air to a certain extent, they usually suffer from weak interfacial bonding between the shell and CaO particles, making them prone to peeling. This invention uses a controlled carbonation reaction to directionally generate a dense CaCO3 coating layer on the surface of CaO adsorbent particles. This shell layer is chemically bonded to the core CaO structure, exhibiting good affinity and continuity, achieving more stable and denser interfacial protection, blocking moisture penetration at the source, and effectively inhibiting hygroscopic expansion and particle pulverization. Furthermore, this dense calcium carbonate shell structure significantly improves the overall mechanical strength of the particles, extending the material's service life. While traditional physical coating methods and inert framework doping can improve the deliquescence resistance of particles to a certain extent, they reduce the proportion of free calcium oxide in the adsorbent. Both methods lead to a decrease in the CO2 capture performance of the adsorbent. The CaCO3 coating layer constructed in this invention can effectively isolate the contact between humid air and CaO particles at room temperature, and can also participate in the cycle during the high-temperature CO2 capture process, thereby increasing the content of free calcium oxide inside the adsorbent and significantly improving the CO2 adsorption capacity. This achieves synergistic optimization of anti-deliquescence performance and high adsorption performance, successfully breaking through the technical bottleneck of traditional methods that are difficult to balance "anti-deliquescence performance" and "high adsorption activity". Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the process flow of the present invention.

[0020] Figure 2 This is a schematic diagram of the high-strength calcium-based particles modified by surface carbonation according to the present invention.

[0021] Figure 3 The results show the anti-deliquescence performance test results of the adsorbent particles in Comparative Example 1 and Examples 1-5.

[0022] Figure 4 The diagram shows the morphological evolution of the adsorbent particles in Comparative Example 1 and Example 3 under conditions of 35°C and 90% relative humidity.

[0023] Figure 5 The graph shows the mechanical strength results of the adsorbent particles in Comparative Example 1 and Examples 1-5.

[0024] Figure 6 The graph shows the adsorption performance of the adsorbent particles in Comparative Example 1 and Examples 1-5.

[0025] Figure 7 SEM images of the adsorbent particles in Comparative Example 1 and Example 3. (a) Comparative Example 1, (b) Example 3. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0027] This invention proposes a high-strength, deliquescent-resistant calcium-based CO2 adsorbent modified with surface carbonation and its preparation method. Figure 1 This is a schematic diagram of the process flow of the present invention. The detailed operation flow of this method is as follows: (1) Raw material preparation: Select industrial-grade CaO particles with uniform particle size and purity of not less than 90% as reaction raw materials (not limited to 90% purity, depending on actual industrial application requirements); weigh a certain amount of calcium oxide particles according to the total amount to be processed.

[0028] (2) Construction of a controllable surface carbonation reaction device: The calcium oxide particles are evenly spread in a high-temperature resistant ceramic boat and placed in the central reaction area of ​​a horizontal tube furnace; one end of the horizontal tube furnace is connected to a gas flow controller, which is equipped with a precision gas flow regulating valve to stably provide a mixture of N2 and CO2 at a certain flow rate (the volume fraction of each of the N2 and CO2 mixture is not specifically set here, it is only necessary to ensure that the CO2 volume concentration is higher than 10%); the temperature of the heating zone of the tube furnace is set to 600℃ to realize the carbonation reaction between CaO surface and CO2; the other end of the horizontal tube furnace is connected to a flue gas analyzer, and the degree of carbonation of the particles is judged by monitoring the concentration of CO2 gas flowing out after the reaction, thereby ensuring the controllability of the carbonation reaction.

[0029] (3) Controllable surface carbonation reaction process: CO2 is introduced at 600℃ to carry out a controllable carbonation reaction. During this process, the surface of calcium oxide particles undergoes in-situ carbonation reaction with CO2 to form a dense and uniform CaCO3 coating layer. After the reaction is completed, the gas inlet valve is quickly closed and the heating is terminated.

[0030] (4) Cooling and drying: The particles that have completed the controlled surface carbonation reaction are taken out along with the ceramic boat and immediately placed in a sealed nitrogen atmosphere for cooling; a sealed inert atmosphere desiccant is used for natural cooling to room temperature to avoid structural stress cracking caused by rapid cooling. Specifically: drying is completed in a desiccant with an inlet and an outlet. The desiccant is first filled with nitrogen or argon gas. After the particles that have completed the controlled surface carbonation reaction are placed in the desiccant, the inlet and outlet are closed.

[0031] (5) Product collection and preservation: After cooling, collect the treated adsorbent particles to obtain adsorbent particles with a dense calcium carbonate coating on the surface.

[0032] Figure 2This is a schematic diagram of the high-strength calcium-based particles modified by surface carbonation according to the present invention. The present invention achieves a dense CaCO3 coating layer on the surface of molded CaO adsorbent particles through a controllable surface carbonation reaction. This not only effectively overcomes the problem of traditional calcium-based adsorbents being easily broken in humid environments, but also achieves both high mechanical strength and high adsorption performance, offering the following significant advantages: 1. A dense and uniform calcium carbonate coating layer is formed in situ on the surface of CaO particles through a controllable surface carbonation reaction, effectively blocking the diffusion of humid air into the interior of the CaO particles and inhibiting deliquescence problems such as water absorption swelling and structural cracking of CaO particles in humid environments. 2. This calcium carbonate coating layer is chemically bonded to the core CaO structure, exhibiting good affinity and continuity, and is not easily detached. This provides a more stable and denser interface protection, blocking water vapor penetration at the source and effectively inhibiting hygroscopic swelling and particle pulverization. Furthermore, this dense and hard calcium carbonate shell structure significantly improves the overall mechanical strength of the particles and extends the service life of the material. Third, the CaCO3 coating layer constructed in this invention can effectively isolate the contact between humid air and CaO particles at room temperature, and can also participate in the cycle during the high-temperature CO2 capture process, thereby increasing the content of free calcium oxide inside the adsorbent and significantly improving the CO2 adsorption capacity. This achieves synergistic optimization of anti-deliquescence performance and high adsorption performance, and successfully breaks through the technical bottleneck of traditional methods that make it difficult to balance "anti-deliquescence performance" and "high adsorption activity".

[0033] In summary, this invention proposes a high-strength, deliquescent-resistant calcium-based CO2 adsorbent with surface carbonation modification and its preparation method, achieving the potential of improved stability, enhanced performance, and simplified process, providing effective technical support for the large-scale application of calcium-based adsorbent materials in carbon capture engineering.

[0034] In the process of constructing a calcium carbonate coating structure through a controlled surface carbonation reaction, this invention employs a horizontal tubular furnace. However, those skilled in the art should understand that this invention is not limited to this type of equipment, and the following alternative devices can also be used to achieve the process: vertical tubular furnace, moving bed reactor, fluidized bed reactor, rotary bed reactor, etc. All of these devices can achieve controlled surface carbonation reactions at different scales. The core reaction mechanism is: under certain temperature and CO2 concentration atmosphere conditions, a controlled carbonation reaction is achieved on the surface of CaO particles, generating a dense, uniform, and continuous calcium carbonate coating structure.

[0035] In the following examples, commercially available calcium hydroxide (Aladdin, purity >99%) was used as the calcium oxide precursor, and calcium oxide particles were prepared by extrusion molding. The particle preparation process included material mixing, extrusion, cutting, drying, and calcination to finally obtain calcium oxide particles. Subsequently, the prepared calcium oxide particles were placed in a horizontal tube furnace, and the reaction temperature was set to 550-750°C. One end of the tube furnace was connected to a gas flow controller, which precisely and continuously supplied a N2 / CO2 mixed gas into the tube furnace to ensure the full reaction. The other end of the tube furnace was connected to a flue gas analyzer, which monitored the CO2 concentration in the outflow gas after the reaction to achieve precise control of the carbonation reaction process, thereby controlling the coating thickness. After the controllable surface carbonation reaction was completed, the particles were quickly removed and transferred to a sealed cooling dish under a nitrogen atmosphere to cool naturally to room temperature. After cooling, adsorbent particles with a dense CaCO3 coating on the surface were obtained.

[0036] By measuring and recording the mass gain of the sample after each reaction, and calculating and analyzing the conversion ratio of the carbonation reaction in the sample based on the obtained weight gain data, a controllable assessment of the degree of carbonation can be achieved.

[0037] To evaluate the structural integrity and anti-breakage performance of adsorbent particles in a high-humidity environment, the prepared particle samples were placed in a constant temperature and humidity chamber for testing: Test conditions: temperature 35°C, relative humidity 90%; Placement time points: 0h, 12h, 24h, and 48h; At each time point, the particle samples were taken out, and the macroscopic morphology of the particles was photographed using a high-definition camera to observe their surface changes and breakage trends; After the 48h test, the particle samples were put into a standard sieve separator, and mechanical sieving was performed with vibration parameters set; The number of particles that still maintained their original morphology after sieving was recorded, and the particle retention rate (the percentage of particles that still maintained their original morphology after 48h relative to the initial number) was used as a quantitative evaluation index of deliquescence resistance.

[0038] To assess the mechanical strength of the sample particles, the intact particles retained after sieving were subjected to mechanical strength tests. The tests were conducted using a particle strength tester, and the maximum crushing force of each particle was recorded. To more visually demonstrate the distribution characteristics of particle mechanical strength, box plots were created for statistical analysis.

[0039] The CO2 capture performance of the sample particles was tested using a fixed-bed reactor. 5g of calcium-based adsorbent sample was loaded into a vertical fixed-bed reactor, and simulated flue gas was introduced for performance evaluation. The test operating conditions of the fixed-bed reactor were: simulated flue gas flow rate 1L / min, composition 15% CO2 and 85% N2, adsorption temperature 650℃, and reaction time 30min. The CO2 adsorption capacity of the calcium-based adsorbent sample was measured, with a cumulative measurement of ten cycles.

[0040]

[0041] In the formula: The value represents the CO2 adsorption capacity of the calcium-based adsorbent sample, expressed in gCO2 / g adsorbent. The mass of the carbonated calcium-based adsorbent sample. The mass of the calcium-based adsorbent sample after the Nth calcination cycle is given.

[0042] The morphology and structure of the particle surface were observed using scanning electron microscopy (SEM) on some samples.

[0043] Example 1 The preparation process of this invention is as follows: Figure 1 As shown, 5g of calcium oxide particles were placed in a quartz boat in a horizontal tube furnace, and the constant temperature heating zone was set to 600°C. A mass flow controller was connected to one end of the furnace body to continuously and precisely introduce a CO2 / N2 mixture (total flow rate 500 mL / min, CO2 volume fraction 20%) into the furnace. The reaction time was controlled to 5 min, and a sample with a carbonation conversion rate of about 10% could be obtained. After the reaction was completed, the sample was quickly removed from the furnace and immediately placed in a nitrogen-filled desiccator to cool naturally to room temperature, resulting in adsorbent particles with a dense CaCO3 coating on the surface.

[0044] The mass of the sample particles prepared by the method described in Example 1 before and after the controlled surface carbonation reaction was weighed and recorded. The weight gain was 0.30g, which translates to a carbonation rate of approximately 10%.

[0045] The particle samples prepared by the method described in Example 1 were subjected to deliquescence resistance testing. The experimental test conditions and operating conditions were as described above. The particle retention rate of the Example 1 sample was measured to be 37.25%. After the deliquescence resistance test, the adsorbent particles were subjected to mechanical strength testing. The average mechanical strength of the Example 1 sample particles was measured to be 44 N.

[0046] The adsorbent particles prepared by the method described in Example 1 were subjected to CO2 capture performance testing in a fixed-bed reactor. The experimental test conditions and operating conditions were as described above. The initial CO2 adsorption capacity of the sample in Example 1 was measured to be 0.56 gCO2 / g adsorbent, the cumulative CO2 adsorption capacity after ten cycles was 5.27 gCO2 / g adsorbent, and the average CO2 adsorption capacity was 0.527 gCO2 / g adsorbent.

[0047] Example 2 The preparation process of this invention is as follows: Figure 1As shown, 5g of calcium oxide particles were placed in a quartz boat in a horizontal tube furnace, and the constant temperature heating zone was set to 600°C. A mass flow controller was connected to one end of the furnace body to continuously and precisely introduce a CO2 / N2 mixed gas (total flow rate 500 mL / min, CO2 volume fraction 20%) into the furnace. The reaction time was controlled at 10 min to obtain a sample with a carbonation conversion rate of about 20%. After the reaction was completed, the sample was quickly removed from the furnace and immediately placed in a nitrogen-filled desiccator to cool naturally to room temperature, resulting in adsorbent particles with a dense CaCO3 coating on the surface.

[0048] The mass of the sample particles prepared by the method described in Example 2 before and after the controlled surface carbonation reaction was weighed and recorded. The weight gain was 0.61 g, which translates to a carbonation rate of approximately 20%.

[0049] The particle samples prepared by the method described in Example 2 were subjected to deliquescence resistance testing. The experimental test conditions and operating conditions were as described above. The particle retention rate of the Example 2 sample was measured to be 75.22%. After the deliquescence resistance test, the adsorbent particles were subjected to mechanical strength testing. The average mechanical strength of the Example 2 sample particles was measured to be 78 N.

[0050] The adsorbent particles prepared by the method described in Example 2 were subjected to CO2 capture performance testing in a fixed-bed reactor. The experimental test conditions and operating conditions were as described above. The initial CO2 adsorption capacity of the sample in Example 2 was measured to be 0.50 gCO2 / g adsorbent, the cumulative CO2 adsorption capacity after ten cycles was 5.23 gCO2 / g adsorbent, and the average CO2 adsorption capacity was 0.523 gCO2 / g adsorbent.

[0051] Example 3 The preparation process of this invention is as follows: Figure 1 As shown, 5g of calcium oxide particles were placed in a quartz boat in a horizontal tube furnace, and the constant temperature heating zone was set to 600°C. A mass flow controller was connected to one end of the furnace body to continuously and precisely introduce a CO2 / N2 mixture (total flow rate 500 mL / min, CO2 volume fraction 20%) into the furnace. The reaction time was controlled at 20 min to obtain a sample with a carbonation conversion rate of about 30%. After the reaction was completed, the sample was quickly removed from the furnace and immediately placed in a nitrogen-filled desiccator to cool naturally to room temperature, resulting in adsorbent particles with a dense CaCO3 coating on the surface.

[0052] The mass of the sample particles prepared by the method described in Example 3 before and after the controlled surface carbonation reaction was weighed and recorded. The weight gain was 0.91 g, which translates to a carbonation rate of approximately 30%.

[0053] The particle samples prepared by the method described in Example 3 were subjected to deliquescence resistance testing. The experimental test conditions and operating conditions were as described above. The particle retention rate of the Example 3 sample was measured to be 97.51%. After the deliquescence resistance test was completed, the adsorbent particles were subjected to mechanical strength testing. The average mechanical strength of the Example 3 sample particles was measured to be 97 N.

[0054] The adsorbent particles prepared by the method described in Example 3 were used to test their CO2 capture performance in a fixed-bed reactor. The experimental test conditions and operating conditions were as described above. The initial CO2 adsorption capacity of the sample in Example 3 was measured to be 0.43 gCO2 / g adsorbent, the cumulative CO2 adsorption capacity over ten cycles was 5.17 gCO2 / g adsorbent, and the average CO2 adsorption capacity was 0.517 gCO2 / g adsorbent.

[0055] Example 4 The preparation process of this invention is as follows: Figure 1 As shown, 5g of calcium oxide particles were placed in a quartz boat in a horizontal tube furnace, and the constant temperature heating zone was set to 550°C. A mass flow controller was connected to one end of the furnace body to continuously and precisely introduce a CO2 / N2 mixed gas (total flow rate 500 mL / min, CO2 volume fraction 20%) into the furnace. The reaction time was controlled at 20 min to obtain a sample with a carbonation conversion rate of about 20%. After the reaction was completed, the sample was quickly removed from the furnace and immediately placed in a nitrogen-filled desiccator to cool naturally to room temperature, resulting in adsorbent particles with a dense CaCO3 coating on the surface.

[0056] The mass of the sample particles prepared by the method described in Example 4 before and after the controlled surface carbonation reaction was weighed and recorded. The weight gain was 0.60 g, which translates to a carbonation rate of approximately 20%.

[0057] The particle samples prepared by the method described in Example 4 were subjected to deliquescence resistance testing. The experimental test conditions and operating conditions were as described above. The particle retention rate of the Example 4 sample was measured to be 74.93%. After the deliquescence resistance test, the adsorbent particles were subjected to mechanical strength testing. The average mechanical strength of the Example 3 sample particles was measured to be 79 N.

[0058] The adsorbent particles prepared by the method described in Example 4 were subjected to CO2 capture performance testing in a fixed-bed reactor. The experimental test conditions and operating conditions were as described above. The initial CO2 adsorption capacity of the sample in Example 4 was measured to be 0.51 gCO2 / g adsorbent, the cumulative CO2 adsorption capacity after ten cycles was 5.24 gCO2 / g adsorbent, and the average CO2 adsorption capacity was 0.524 gCO2 / g adsorbent.

[0059] Example 5 The preparation process of this invention is as follows: Figure 1 As shown, 5g of calcium oxide particles were placed in a quartz boat in a horizontal tube furnace, and the constant temperature heating zone was set to 750°C. A mass flow controller was connected to one end of the furnace body to continuously and precisely introduce a CO2 / N2 mixed gas (total flow rate 500 mL / min, CO2 volume fraction 20%) into the furnace. The reaction time was controlled to 5 min, and a sample with a carbonation conversion rate of about 20% could be obtained. After the reaction was completed, the sample was quickly removed from the furnace and immediately placed in a nitrogen-filled desiccator to cool naturally to room temperature, resulting in adsorbent particles with a dense CaCO3 coating on the surface.

[0060] The mass of the sample particles prepared by the method described in Example 5 before and after the controlled surface carbonation reaction was weighed and recorded. The weight gain was 0.62 g, which translates to a carbonation rate of approximately 20%.

[0061] The particle samples prepared by the method described in Example 5 were subjected to deliquescence resistance testing. The experimental test conditions and operating conditions were as described above. The particle retention rate of the Example 5 sample was measured to be 73.15%. After the deliquescence resistance test, the adsorbent particles were subjected to mechanical strength testing. The average mechanical strength of the Example 5 sample particles was measured to be 78 N.

[0062] The adsorbent particles prepared by the method described in Example 5 were subjected to CO2 capture performance testing in a fixed-bed reactor. The experimental test conditions and operating conditions were as described above. The initial CO2 adsorption capacity of the sample in Example 5 was measured to be 0.52 gCO2 / g adsorbent, the cumulative CO2 adsorption capacity after ten cycles was 5.24 gCO2 / g adsorbent, and the average CO2 adsorption capacity was 0.524 gCO2 / g adsorbent.

[0063] Comparative Example 1 The comparative sample in this invention is CaO particles that have not undergone surface carbonation. The CaO particle sample from Comparative Example 1 was subjected to a deliquescence resistance test under the experimental and operating conditions as described above. The particle retention rate of Comparative Example 1 was measured to be 24.95%. After the deliquescence resistance test, the adsorbent particles were subjected to a mechanical strength test. The average mechanical strength of the particles from Comparative Example 1 was measured to be 24 N.

[0064] The CO2 capture performance of the CaO particle sample in Comparative Example 1 was tested using a fixed-bed reactor. The experimental test conditions and operating conditions were as described above. The initial CO2 adsorption capacity of Comparative Example 1 was measured to be 0.62 gCO2 / g adsorbent, the cumulative CO2 adsorption capacity over ten cycles was 5.37 gCO2 / g adsorbent, and the average CO2 adsorption capacity was 0.537 gCO2 / g adsorbent.

[0065] Table 1 shows the weight gain of samples from Examples 1-5 before and after the controlled surface carbonation reaction. The sample of Example 1 gained 0.3 g after the reaction, which translates to a carbonation conversion rate of approximately 10%. The sample of Example 2 gained 0.61 g after the reaction, which translates to a carbonation conversion rate of approximately 20%. The sample of Example 3 gained 0.91 g after the reaction, which translates to a carbonation conversion rate of approximately 30%. The sample of Example 4 gained 0.60 g after the reaction, which translates to a carbonation conversion rate of approximately 20%. The sample of Example 5 gained 0.62 g after the reaction, which translates to a carbonation conversion rate of approximately 20%.

[0066] Table 1. Weight gain before and after surface carbonation reaction in Examples 1-5

[0067] Figure 3 The results show the deliquescence resistance of the particles from Examples 1-5 and Comparative Example 1 after being placed at 35°C and 90% relative humidity for 48 hours. Comparative Example 1 consists of CaO particles without controlled surface carbonation treatment, with a particle retention rate of only 24.95%. In contrast, the adsorbent particles from Examples 1-5, obtained after controlled surface carbonation treatment and possessing a dense CaCO3 coating, achieved a particle retention rate as high as 97.51%. Figure 4 The figure shows the morphological evolution of the adsorbent particles in Comparative Example 1 and Example 3 under conditions of 35°C and 90% relative humidity. As can be observed from the figure, the particle structure of the Comparative Example 1 sample deteriorated rapidly; some particles showed obvious cracks as early as 2 hours, and by 24 hours, a large number of particles had pulverized, with only a few particles retaining their original morphology. In contrast, the Example 3 sample, even after being placed under high humidity conditions for 48 hours, still largely maintained its original morphology and did not show significant pulverization, demonstrating good resistance to deliquescence.

[0068] Figure 5 The figure shows the mechanical strength distribution of the adsorbent particles in Comparative Example 1 and Examples 1-5. The average strength of the particles in Comparative Example 1 is concentrated around 25 N, indicating that the particle structure is relatively fragile and prone to breakage. The average mechanical strength of the adsorbent particles in Examples 1-5 is significantly improved, and the distribution is more uniform, indicating that the particle structure stability is enhanced. The sample in Example 3 has the highest mechanical strength, with an average mechanical strength of approximately 97 N. This result indicates that the dense CaCO3 coating layer generated after the controlled surface carbonation reaction significantly improves the overall particle integrity and load-bearing capacity, thereby improving mechanical stability.

[0069] Figure 6The CO2 capture performance of the adsorbent particles in Comparative Example 1 and Examples 1-5 is demonstrated. The initial adsorption capacity of the Comparative Example 1 sample was 0.62 g CO2 / g adsorbent. As the controlled surface carbonation reaction continued, the free calcium oxide content in the sample decreased, leading to a decline in the initial CO2 adsorption capacity. The initial adsorption capacity of the Example 1 sample was 0.56 g CO2 / g adsorbent, while the initial CO2 capture capacity of the adsorbent particles in Example 3 was only 0.43 g CO2 / g adsorbent. Nevertheless, with the progress of cycling, the initially formed CaCO3 coating layer gradually decomposed under pyrolysis. Therefore, the adsorption performance of the Examples 1-5 samples improved in subsequent cycles and gradually approached the performance of Comparative Example 1. After ten cycles, the cumulative adsorption capacity of Comparative Example 1 was 5.37 g CO2 / g adsorbent, while the cumulative adsorption capacity of Example 3, which had the worst initial adsorption performance, was 5.17 g CO2 / g adsorbent after ten cycles.

[0070] Figure 7 The image shows the SEM morphology of the adsorbent particles in Comparative Example 1 and Example 3. The sample from Example 1 exhibits obvious breakage and irregular agglomeration on its surface. A loose structure forms between the particles, with large cracks and pores, demonstrating poor structural stability. The surface is rough and uneven, possibly related to lower mechanical strength or an unstable crystal structure. In contrast, the sample from Example 3 shows a more uniform and dense structure. The particles are tightly packed without obvious cracks, the surface is relatively smooth, and the grain boundaries are clear, indicating that this sample has higher stability and better structural integrity. Therefore, the sample from Example 3 possesses better mechanical strength and deliquescence resistance.

[0071] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a strength-improved, deliquescence-resistant calcium-based CO2 adsorbent modified by surface carbonation, characterized in that, The method comprises the following steps: (1) reacting CaO particles with CO2 gas or with a mixed gas containing CO2 at a temperature of 550-750°C, wherein the mixed gas does not contain any other acid gas besides CO2, and the CaO particles are carbonated to form a CaCO3 coating layer; (2) naturally cooling the particles with the CaCO3 coating layer obtained in step (1) in a non-purged non-oxidizing atmosphere to avoid structural stress cracking caused by rapid cooling, thereby obtaining a surface carbonation-modified high-strength moisture-resistant calcium-based CO2 adsorbent.

2. The method of producing a strength-improved, deliquescence-resistant calcium-based CO2 adsorbent with surface carbonation modification according to claim 1, wherein In step (1), the temperature is 600-650°C.

3. The method of producing a strength-improved, deliquescence-resistant calcium-based CO2 adsorbent with surface carbonation modification according to claim 1, wherein In step (1), the volume concentration of CO2 in the mixed gas is greater than or equal to 10%.

4. The method for producing the strength-improved, deliquescence-resistant calcium-based CO2 adsorbent with surface carbonation modification according to claim 1 or 3, characterized in that, The mixed gas contains at least one of N2, Ar and O2 besides CO2.

5. The method of producing a strength-improved, deliquescence-resistant calcium-based CO2 adsorbent with surface carbonation modification according to claim 1, characterized in that, The reaction time is 5-20 min.

6. The method of producing a strength-improved, deliquescence-resistant calcium-based CO2 adsorbent with surface carbonation modification according to claim 5, characterized in that, The reaction time is 10-20 min.

7. A surface carbonation-modified high-strength moisture-resistant calcium-based CO2 adsorbent prepared by the method of any one of claims 1-6.

8. Use of the surface carbonation-modified high-strength moisture-resistant calcium-based CO2 adsorbent of claim 7 in CO2 capture.

9. Use according to claim 8, wherein the compound is ###0002### The CaCO3 coating layer on the surface of the surface carbonation-modified high-strength moisture-resistant calcium-based CO2 adsorbent is chemically connected to the calcium oxide, so that the CaCO3 coating layer can effectively block the contact of humid air with the calcium oxide particles, thereby inhibiting the water absorption and swelling of the adsorbent particles and improving the moisture resistance of the adsorbent particles.

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