Co2 absorbent, enhanced amine-based flue gas decarbonization method, and decarbonization device

Abstract

A CO2 absorbent, an enhanced amine-based flue gas decarbonization method, and a decarbonization device. The absorbent is mainly composed of a shuttle agent and a proton acceptor; the molar ratio of the shuttle agent to the proton acceptor is 1:1-1:5; and the molar ratio of the shuttle agent to the proton acceptor is 1:3. By preparing the absorbent and introducing, into the absorbent, flue gas that has been broken into micro-bubbles, the micro-bubbles, under the action of a drag force, can move in synchrony with a liquid phase, thereby forming a uniform gas-liquid mixture, enhancing the cyclic loading of the absorbent, reducing the overall energy consumption of a decarbonization process, and improving CO2 removal efficiency.

Description

A CO2 absorbent, an enhanced amine method for flue gas decarbonization, and a decarbonization device. Technical Field

[0001] This invention belongs to the field of flue gas purification technology, specifically to a CO2 absorbent, an enhanced amine method for flue gas decarbonization, and a decarbonization device. Background Technology

[0002] In the field of CCUS (Carbon Capture, Utilization, and Storage), amine / ammonia decarbonization technology is widely used, playing a crucial role, especially in the large-scale capture and utilization of flue gas carbon sources. However, in practice, most decarbonization methods exhibit slow carbon dioxide capture rates and poor CO2 capture efficiency, resulting in high regeneration energy consumption. Therefore, effectively reducing regeneration energy consumption and achieving higher CO2 capture efficiency and rates is key to the widespread application of this technology.

[0003] In view of this, the present invention is hereby proposed. Summary of the Invention

[0004] The first objective of this invention is to provide a CO2 absorbent that combines a shuttle and a proton acceptor. By using the shuttle, the CO2 capture rate is accelerated, and by combining it with the proton acceptor, the capture rate of the shuttle is improved while also having a high CO2 absorption capacity.

[0005] The second objective of this invention is to provide an enhanced amine-based flue gas decarbonization method. This method involves preparing an absorbent and introducing flue gas broken into microbubbles into the absorbent. Under the influence of drag force, the microbubbles can advance synchronously with the liquid phase, thereby forming a uniform gas-liquid mixture. In this way, the cyclic load of the absorbent is increased, thereby reducing the total energy consumption of the decarbonization process and improving the CO2 removal efficiency.

[0006] The third objective of this invention is to provide a decarbonization device corresponding to the enhanced amine-based flue gas decarbonization method, which has low construction costs and is simple to operate.

[0007] To achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: A CO2 absorbent, wherein the absorbent is mainly composed of a shuttle and a proton receiver; preferably, the molar ratio of the shuttle and the proton receiver is 1:1-1:5; preferably, the molar ratio of the shuttle and the proton receiver is 1:3.

[0008] In this invention, the configuration of the absorbent is crucial. During the initial decarbonization of flue gas, the shuttle acts as a rate promoter while also capturing carbon dioxide and enhancing the activity of the proton acceptor. This accelerates CO2 capture and further increases the reaction rate during initial decarbonization. After initial decarbonization, the flue gas is introduced into the rich liquid. Here, the flue gas is broken into microbubbles, which, under drag, move synchronously with the rich liquid, forming a homogeneous gas-liquid mixture. The presence of the shuttle further enhances the activity of the proton acceptor because the reduced bubble size generates a free radical effect, causing the chemical bonds in the solution to break and form hydroxyl and hydrogen free radicals. Hydrogen radicals promote the chemical dissolution of CO2 and form protons. Due to the presence of a proton acceptor, these protons and hydroxyl radicals formed after breakage interact with the proton acceptor, preventing them from binding with the shuttle and occupying carbon dioxide sites on the shuttle, thus reducing its carbon dioxide capture efficiency. During preliminary decarbonization of flue gas, the presence of the shuttle ensures the presence of carbonic acid in the resulting rich solution. Due to the instability of carbonic acid, it decomposes to produce hydrogen ions and bicarbonate ions. These hydrogen ions can also combine with the proton acceptor, enhancing its activity. Furthermore, the presence of the proton acceptor prevents hydrogen ions from binding with the shuttle and occupying carbon dioxide sites, thus maintaining its carbon dioxide capture efficiency during preliminary decarbonization. Therefore, this invention combines a shuttle and a proton acceptor, using the shuttle to enhance the proton acceptor's activity while ensuring the shuttle's carbon dioxide capture efficiency remains unaffected. In summary, the molar ratio of shuttle to proton acceptor is crucial for this invention. In the decarbonization method of this invention, if there is too much shuttle, the amount of proton acceptor will be correspondingly reduced, causing some carbon dioxide sites on the shuttle to be occupied by hydrogen ions. This affects the shuttle's carbon dioxide capture effect and the reaction rate. If there is too little shuttle, there will be too much proton acceptor, and some of the proton acceptor will not be able to improve its activity. Furthermore, too little shuttle will reduce the initial decarbonization reaction rate and correspondingly reduce its capture of carbon dioxide in the flue gas.

[0009] Preferably, as a further feasible option, the shuttle agent is one or more selected from 2-amino-2-methyl-1-propanol, monoethanolamine, piperazine, N-methylpiperazine, benzylamine, and piperidine.

[0010] Preferably, as a further feasible option, the shuttle is a mixture of N-methylpiperazine and monoethanolamine.

[0011] In this invention, one or more of 2-amino-2-methyl-1-propanol, monoethanolamine, piperazine, N-methylpiperazine, benzylamine, and piperidine are selected as shuttle agents, and preferably a mixture of N-methylpiperazine and monoethanolamine is selected as the shuttle agent. This results in an absorbent with superior carbon dioxide capture performance. Furthermore, the mixture of the two agents further enhances the reaction rate of the initial decarbonization reaction. Monoethanolamine, as a shuttle agent, has high capture efficiency, high solubility, and the ability to efficiently capture carbon dioxide, allowing it to adsorb onto its surface and form a solution. However, for the process of monoethanolamine absorbing carbon dioxide, a high concentration of monoethanolamine is generally required to ensure the absorption rate and reaction stability, making the solution formed by monoethanolamine and carbon dioxide less prone to oxidation. Desorption occurred during subsequent operations. However, due to the toxicity of high-concentration monoethanolamine and the advanced technology required for its carbon dioxide absorption, which necessitates the control of multiple conditions and parameters to achieve optimal carbon dioxide capture, the process is challenging and difficult to control. The presence of N-methylpiperazine can reduce the concentration of monoethanolamine used and improve the stability of the solution formed after monoethanolamine combines with carbon dioxide. This makes the solution less prone to desorption during subsequent operations, thus affecting the absorbent's carbon dioxide capture efficiency. Furthermore, N-methylpiperazine itself also has a certain carbon dioxide capture effect. Therefore, the combination of the two can further enhance the removal of carbon dioxide by the absorbent and maintain stability, making desorption less likely to occur during subsequent operations.

[0012] Preferably, as a further feasible option, the molar ratio of N-methylpiperazine to monoethanolamine in the shuttle is (2:1)-(1:3).

[0013] Preferably, as a further feasible option, the molar ratio of N-methylpiperazine to monoethanolamine in the shuttle is 1:1.

[0014] In this invention, the molar ratio of N-methylpiperazine to monoethanolamine in the shuttle agent is crucial. This is because when the molar ratio of N-methylpiperazine to monoethanolamine is (2:1)-(1:3), preferably 1:1, the absorbent prepared by mixing the two exhibits excellent carbon dioxide capture performance. Furthermore, the mixing of the two provides the best rate increase for the decarbonization reaction, and the resulting carbon dioxide-rich solution is more stable and less prone to desorption in subsequent operations. Therefore, if there is too much N-methylpiperazine in the absorbent, the carbon dioxide capture performance of the prepared absorbent will be affected. Conversely, if there is too much monoethanolamine, the solution formed after its combination with carbon dioxide will be unstable and prone to desorption in subsequent operations, resulting in premature release of carbon dioxide.

[0015] Preferably, as a further feasible option, the proton acceptor is one or more of diethanolamine, diisopropanolamine, triethanolamine, and methyldiethanolamine.

[0016] Preferably, as a further feasible option, the proton acceptor is methyldiethanolamine.

[0017] To achieve the above-mentioned objectives of this invention, this invention also provides a flue gas decarbonization method compatible with the above-mentioned absorbent: an enhanced amine-based flue gas decarbonization method, comprising the following steps: preparing an absorbent and preheating the absorbent; introducing flue gas into the preheated absorbent to carry out a decarbonization reaction, obtaining a rich liquid; introducing flue gas broken into microbubbles again into the rich liquid, obtaining a gas-liquid mixture; and performing gas-liquid separation and regeneration on the supersaturated rich liquid to obtain high-purity CO2.

[0018] In the present invention, an absorbent is first prepared, and then flue gas is introduced into the absorbent to carry out a preliminary decarbonization reaction. In this preliminary decarbonization process, the absorbent can enrich the CO2 present in the flue gas. However, there is a certain limit to the enrichment of CO2 by the absorbent in this preliminary decarbonization process. Therefore, through a series of creative efforts, the present invention has discovered that after using the absorbent provided by the present invention to perform preliminary decarbonization of CO2, the load of the rich absorbent liquid generated at this time is the load of the traditional production process. However, the present invention introduces flue gas that has been broken into microbubbles into the rich liquid. Under the influence of drag force, the microbubbles can move synchronously with the liquid phase, thereby forming a uniform gas-liquid mixture. In this way, the circulating load of the absorbent is increased, thereby reducing the total energy consumption of the decarbonization process and improving the CO2 removal effect. The microbubbles have a diameter ranging from 100 to 300 μm. This method further enhances the activity of the absorbent, increases the cyclic load of the reaction solution, improves its CO2 enrichment effect, and gives it superior decarbonization performance. It also further reduces regeneration energy consumption, and the final supersaturated rich solution load is at least 1.2 times that of the rich solution obtained after preliminary decarbonization. This is because, in this invention, the rich solution obtained after preliminary decarbonization of flue gas is mixed with a new batch of flue gas broken into microbubbles to form a homogeneous gas-liquid mixture. The microbubbles generate free radical and interfacial electric field effects. Reducing the bubble size allows the hydrogen and hydroxide bonds in the solution to break, forming hydrogen and hydroxyl radicals. The hydrogen radicals promote CO2 dissolution, and the hydroxyl radicals interact with the absorbent. This combination enhances the activity of the proton acceptor, allowing it to accept more dissolved carbon dioxide, ultimately increasing the load.

[0019] Preferably, as a further feasible option, the microbubbles are micron-sized bubbles with a diameter of 100-300 μm; more preferably, the diameter of the microbubbles is 300 μm.

[0020] In this invention, the size of the microbubbles is crucial. This is because a suitable microbubble size allows the gas-liquid mixture formed from the flue gas and rich liquid to generate free radical and interfacial electric field effects through smaller bubble sizes. This enables the absorbent to achieve a higher loading, and the free radical effect enhances the absorbent's activity, thereby reducing the overall energy consumption of the process. Therefore, for this invention, a microbubble diameter of 100-300 μm results in a superior free radical effect that enhances the absorbent's activity, leading to better carbon dioxide absorption. If the microbubble diameter is too large, the free radical and interfacial electric field effects will be insufficient, hindering the absorption of the absorbent and affecting the decarbonization effect of the flue gas. Conversely, if the microbubbles are too small, a stable gas-liquid mixture cannot be formed after mixing the flue gas and rich liquid.

[0021] To achieve the above-mentioned objectives of the present invention, the present invention also provides a flue gas decarbonization system used in the above-mentioned flue gas decarbonization method: comprising a gas scrubbing tower, a micro-interface reaction tower, a gas-liquid separator, and a regeneration tower connected in sequence.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention provides an absorbent that combines a shuttle and a proton receiver. By using the shuttle, the CO2 capture speed is accelerated, and by combining with the proton receiver, the capture speed of the shuttle is improved while also having a high CO2 absorption capacity.

[0023] (2) The present invention provides an enhanced amine method for flue gas decarbonization. This method involves preparing an absorbent and then introducing flue gas that has been broken into microbubbles into the absorbent to form a uniform gas-liquid mixture, thereby enhancing the activity of the absorbent, increasing the cyclic load of the absorbent, reducing the total energy consumption of the decarbonization process, and improving the CO2 removal effect.

[0024] (3) The present invention provides a decarbonization device corresponding to the enhanced amine method for flue gas decarbonization. The device has low construction cost and simple operation. Attached Figure Description

[0025] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 is a graph plotted based on the results of the invention measured according to Experimental Example 3; Figure 2 is a graph plotted based on the results of the invention measured according to Experimental Example 4. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0027] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0028] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0029] To more clearly illustrate the technical solutions in this invention, specific embodiments are described below.

[0030] Example 1: The implementation steps of this decarbonization method are as follows: 2-Amino-2-methyl-1-propanol and diethanolamine are prepared as absorbents at a molar ratio of 1:1. The prepared absorbents are then preheated to 40°C and introduced into a gas scrubbing tower for preliminary decarbonization reaction. After preliminary decarbonization, the flue gas is discharged from the top of the scrubbing tower. The absorbent undergoes preliminary decarbonization reaction in the scrubbing tower to obtain a rich liquid. A new batch of flue gas is introduced into the rich liquid and then into a micro-interface generator. By adjusting the micro-interface generator, microbubbles with a diameter of 100 μm are generated, forming a stable gas-liquid mixture. The gas-liquid mixture is naturally overflowed into a micro-interface reaction tower for further flue gas decarbonization reaction, generating a supersaturated rich liquid. The supersaturated rich liquid is sequentially introduced into a gas-liquid separator and a regeneration tower for separation and regeneration of flue gas and reaction liquid to obtain high-purity CO2 gas.

[0031] Example 2: The implementation steps of this decarbonization method are as follows: 2-Amino-2-methyl-1-propanol and diethanolamine are prepared as absorbents at a molar ratio of 1:5. The prepared absorbents are then preheated to 40°C and introduced into a gas scrubbing tower for preliminary decarbonization reaction. After preliminary decarbonization, the flue gas is discharged from the top of the scrubbing tower. The absorbent undergoes preliminary decarbonization reaction in the scrubbing tower to obtain a rich liquid. A new batch of flue gas is introduced into the rich liquid and then into a micro-interface generator. By adjusting the micro-interface generator, microbubbles with a diameter of 600 μm are generated, forming a stable gas-liquid mixture. The gas-liquid mixture is naturally overflowed into a micro-interface reaction tower for further flue gas decarbonization reaction, generating a supersaturated rich liquid. The supersaturated rich liquid is sequentially introduced into a gas-liquid separator and a regeneration tower for separation and regeneration of flue gas and reaction liquid to obtain high-purity CO2 gas.

[0032] Example 3: The implementation steps of this decarbonization method are as follows: 2-Amino-2-methyl-1-propanol and diethanolamine are prepared as absorbents at a molar ratio of 1:3. The prepared absorbents are then preheated to 40°C and introduced into a gas scrubbing tower for preliminary decarbonization reaction. After preliminary decarbonization, the flue gas is discharged from the top of the scrubbing tower. The absorbent undergoes preliminary decarbonization reaction in the scrubbing tower to obtain a rich liquid. A new batch of flue gas is introduced into the rich liquid and then into a micro-interface generator. By adjusting the micro-interface generator, microbubbles with a diameter of 500 μm are generated, forming a stable gas-liquid mixture. The gas-liquid mixture is naturally overflowed into a micro-interface reaction tower for further flue gas decarbonization reaction to generate a supersaturated rich liquid. The supersaturated rich liquid is sequentially introduced into a gas-liquid separator and a regeneration tower for separation and regeneration of flue gas and reaction liquid to obtain high-purity CO2 gas.

[0033] Example 4 follows the same implementation steps as Example 3, except that the shuttle 2-amino-2-methyl-1-propanol is replaced with monoethanolamine, while the molar ratio with the proton acceptor diethanolamine remains unchanged.

[0034] Example 5 The specific implementation steps are the same as in Example 3, except that the shuttle agent 2-amino-2-methyl-1-propanol is replaced with N-methylpiperazine.

[0035] Example 6 The specific implementation steps are the same as in Example 3, except that the shuttle agent is replaced with N-methylpiperazine and monoethanolamine mixed in a molar ratio of 2:1.

[0036] Example 7 The specific implementation steps are the same as those in Example 6, except that the shuttle agent is replaced with N-methylpiperazine and monoethanolamine mixed in a molar ratio of 2:3.

[0037] Example 8 follows the same implementation steps as Example 6, except that the shuttle agent is replaced with N-methylpiperazine and monoethanolamine mixed in a molar ratio of 1:1.

[0038] Example 9 follows the same implementation steps as Example 8, except that the proton acceptor diethanolamine is replaced with diisopropanolamine.

[0039] Example 10 follows the same implementation steps as Example 8, except that the proton acceptor diethanolamine is replaced with triethanolamine.

[0040] Example 11 follows the same implementation steps as Example 8, except that the proton acceptor diethanolamine is replaced with methyldiethanolamine.

[0041] Comparative Example 1 follows the same implementation steps as Example 11, except that N-methylpiperazine and monoethanolamine in the shuttle are mixed in a molar ratio of 0.5:1.

[0042] Comparative Example 2 follows the same implementation steps as Example 11, except that N-methylpiperazine and monoethanolamine in the shuttle are mixed in a molar ratio of 1:6.

[0043] Comparative Example 3 follows the same implementation steps as Example 11, except that the molar ratio of the mixture of shuttle N-methylpiperazine and monoethanolamine and the proton acceptor methyldiethanolamine is adjusted to 0.5:1.

[0044] Comparative Example 4 follows the same implementation steps as Example 11, except that the molar ratio of the shuttle N-methylpiperazine and monoethanolamine to the proton acceptor methyldiethanolamine is adjusted to 3:1.

[0045] Comparative Example 5 follows the same implementation steps as Example 11, except that the diameter of the microbubbles is adjusted to 50 μm.

[0046] Comparative Example 6 follows the same implementation steps as Example 11, except that the diameter of the microbubbles is adjusted to 800 μm.

[0047] Comparative Example 7 follows the same implementation steps as Example 11, except that the flue gas is not broken into microbubbles after being introduced into the rich liquid, but is instead directly introduced into the micro-interface reaction tower for decarbonization reaction.

[0048] Example 1: CO2 Absorption Rate Determination. Following the implementation schemes of Examples 1-11 and Comparative Examples 1-7, the pre-set feed gas was treated, and the CO2 absorption rate was finally determined by gas chromatography. The micro-interface generator used was a gas-liquid servo micro-interface generator. The specific determination method is as follows: Chromatographic conditions: Detector: Thermal Conductivity Detector (TCD); Column: Activated carbon column; Detection current: 140 mA; Detection temperature: 220 °C.

[0049] Test absorbent: The absorbent shown in Example 1 was used, and 7.5 L of the absorbent was used to carry out the reaction at the micro-interface.

[0050] Detection steps: The decarbonized flue gas after the reaction is introduced into the gas chromatograph at a rate of 100 ml / min every 1 min to determine the CO2 concentration in the decarbonized flue gas, and then the absorption rate of the absorbent per minute is estimated according to the formula.

[0051] The calculation formula is as follows:

[0052] In the formula, V absorb V represents the amount of CO2 absorbed in 1 minute. total The total amount of flue gas introduced; This represents the total amount of inert components in the introduced flue gas; This represents the proportion of inert components detected by gas chromatography.

[0053] Experimental Example 2: Determination of CO2 Load, Regeneration Rate, Cycle Capacity, and Regeneration Energy Consumption. The supersaturated rich solutions obtained after treatment according to Examples 1-11 and Comparative Examples 1-7 were titrated to determine the final CO2 absorption load. The specific determination method is as follows: Detection steps: Take 1g of supersaturated rich solution and add it to 30g of water for absorption. Add the diluted solution to a closed reactor connected to the gas measuring tube. Add dilute sulfuric acid to the reactor to release the absorbed CO2 from the liquid phase. Measure the change in total gas volume in the gas measuring tube. Use the formula to determine the total CO2 load 'a'.

[0054] The calculation formula is as follows:

[0055] In the formula, a is the carbon dioxide loading (mol / kg), and mabs is the sample mass of the absorbent (kg). and These represent the volume changes of the trachea and the acid burette, respectively.

[0056] The above-mentioned testing methods are applicable not only to CO2 absorption processes but also to CO2 regeneration processes. The regeneration rate is determined by the ratio of the difference in absorbent load before and after regeneration; the circulation capacity is determined by the difference between the supersaturated rich solution and the regenerated lean solution.

[0057] The regeneration energy consumption was measured using an electricity meter after a regeneration test conducted on a pilot-scale device. The measured energy consumption consisted of three parts: the heat of reaction, the sensible heat used for heating the solution, and the heat of evaporation used for water evaporation.

[0058] Testing steps: The regeneration temperature is maintained at 373.15K, the liquid flow rate is 0 to 100 mL / min, and the gas flow rate is 0 to 30 L / min; the regeneration energy consumption is measured using an electricity meter.

[0059] The final measurement results are shown in Table 1 below:

[0060] The specific implementation steps for determining the molar ratio of shuttle agent and proton acceptor in Experiment 3 are the same as in Example 11. Absorbent 1, absorbent 2, and absorbent 3 are prepared according to the molar ratios of shuttle agent and proton acceptor of 1:1, 1:3, and 1:5, respectively. The prepared absorbents are then used to decarbonize the flue gas according to the implementation steps in Example 11. Then, the CO2 absorption rate is measured according to Experiment 1. The curve plotted based on the measurement results is shown in Figure 1.

[0061] Therefore, as can be seen from Figure 1, the present invention explores the most suitable molar ratio between the shuttle and the proton acceptor by conducting experiments. When the molar ratio between the shuttle and the proton acceptor is 1:3 as described in the present invention, the absorbent prepared therefrom has the best absorption effect on CO2.

[0062] The specific implementation steps for determining the molar ratio of N-methylpiperazine and monoethanolamine in the shuttle in Experimental Example 4 were the same as in Example 11. The shuttle was prepared according to the molar ratio of N-methylpiperazine and monoethanolamine of 1:3, 2:1 and 1:1. Then, the shuttle and the proton acceptor methyldiethanolamine were prepared into absorbent 4, absorbent 5 and absorbent 6 respectively at a molar ratio of 1:1. The prepared absorbents were used to decarbonize the flue gas according to the implementation steps in Example 11. Then, the CO2 load was measured according to the method for measuring CO2 load in Experimental Example 2. The curve plotted based on the measurement results is shown in Figure 2.

[0063] Therefore, as can be seen from Figure 2, this invention explores the most suitable molar ratio by measuring the molar ratio of the raw materials in the shuttle agent. When the molar ratio of N-methylpiperazine and monoethanolamine in the shuttle agent is 1:1, the absorbent prepared by it has the best absorption effect on CO2.

[0064] Experiment 5: Determination of the decarbonization effect of the micro-interface generator. The decarbonized flue gas from Example 11 and Comparative Example 7 of this invention was taken and measured according to the measurement methods in Experiment 1 and Experiment 2. It can be seen from the setup of Comparative Example 7 that the only difference between Comparative Example 7 and Example 11 is that Comparative Example 7 does not introduce a micro-interface generator. The specific measurement results are shown in Table 2 below.

[0065] Table 2. Effects of Example 11 and Comparative Example 7

[0066] Therefore, the experimental data in Table 1 shows that, through comparison of Examples 3-6, the selection of the shuttle agent is crucial for this invention. When the shuttle agent is a mixture of N-methylpiperazine and monoethanolamine, the resulting absorbent exhibits excellent absorption of carbon dioxide in flue gas. This is because the mixture of the two agents further enhances the reaction rate of the initial decarbonization reaction. Monoethanolamine, as a shuttle agent, captures carbon dioxide with high capture efficiency and high solubility, enabling it to adsorb carbon dioxide onto its surface and form a solution. However, for the process of absorbing carbon dioxide with monoethanolamine, a high concentration of monoethanolamine is generally required to ensure the absorption rate and reaction stability, preventing the solution formed by monoethanolamine and carbon dioxide from easily deteriorating in subsequent reactions. Desorption occurs during the process, but high concentrations of monoethanolamine are toxic, and the process for absorbing carbon dioxide with high concentrations of monoethanolamine is technically demanding, requiring control of multiple conditions and parameters to achieve a good capture effect. This makes the operation difficult and hard to control. The presence of N-methylpiperazine can reduce the concentration of monoethanolamine used and improve the stability of the solution formed after monoethanolamine combines with carbon dioxide. This makes the solution less prone to desorption in subsequent operations, thus affecting the absorbent's carbon dioxide capture effect. Furthermore, N-methylpiperazine itself also has a certain carbon dioxide capture effect. Therefore, the combination of the two can further enhance the removal of carbon dioxide by the absorbent and maintain stability, making desorption less likely in subsequent operations.

[0067] As can be seen from the comparison of Examples 6-8 and Comparative Examples 1-2, the molar ratio of N-methylpiperazine to monoethanolamine in the shuttle is also very important for this invention. This is because the main purpose of this invention is to improve the reaction rate of the initial decarbonization reaction by using the shuttle and to further enhance the activity of the proton acceptor. The proton acceptor can ensure that the carbon dioxide sites on the shuttle are not occupied by other substances, thereby affecting the carbon dioxide capture effect of the shuttle. Therefore, the molar ratio of N-methylpiperazine to monoethanolamine in the shuttle is crucial. This is because when the molar ratio of N-methylpiperazine to monoethanolamine is (2:1)-(1:3), preferably 1:1, the absorbent prepared by mixing the two has excellent carbon dioxide capture effect, and the mixing of the two is also the best for improving the rate of the decarbonization reaction. Furthermore, the rich liquid formed after capturing carbon dioxide has more stable properties and is less prone to desorption in subsequent operations. If there is too much N-methylpiperazine in the absorbent, the absorbent prepared by it will affect the carbon dioxide capture effect. If there is too much monoethanolamine, the solution formed after it combines with carbon dioxide will be unstable and prone to desorption in subsequent operations, thus causing the carbon dioxide to be released prematurely.

[0068] As can be seen from the comparison of Examples 9-11, the selection of the proton receiver is also very important for this invention. This is because when a new batch of flue gas is introduced into the rich liquid and enters the micro-interface generator together, the flue gas is broken into microbubbles. Under the influence of drag force, the microbubbles can move forward synchronously with the rich liquid, forming a uniform gas-liquid mixture. This process generates a free radical effect. In order to avoid the shuttle agent combining with the generated free radicals, which would occupy the carbon dioxide sites on the shuttle agent and affect its capture effect, it is also necessary to ensure that it has excellent carbon dioxide capture effect. Therefore, this invention selects one or more of diethanolamine, diisopropanolamine, triethanolamine, and methyldiethanolamine as the proton receiver. Methyldiethanolamine is preferred because it has a strong ability to combine with free radicals and can absorb more free radicals, thereby preventing free radicals from occupying the carbon dioxide sites on the shuttle agent. This allows the combination of the proton receiver and the shuttle agent to further improve the capture effect of the shuttle agent on carbon dioxide, while the shuttle agent can also improve the activity of the proton receiver.

[0069] Comparing Example 11 with Comparative Examples 3-4 reveals that the molar ratio of the shuttle agent to the proton receiver is crucial for this invention. This is because the absorbent is prepared by mixing the shuttle agent and the proton receiver. After preliminary decarbonization of the flue gas using the absorbent, a rich liquid is formed. Flue gas is then introduced into the rich liquid and fed into a micro-interface generator to form a homogeneous gas-liquid mixture, further enhancing the capture of carbon dioxide from the flue gas. The shuttle agent, acting as a rate enhancer, also possesses a certain carbon dioxide capture effect and can enhance the activity of the proton receiver, accelerating the CO2 capture rate and further increasing the reaction rate during preliminary decarbonization of the flue gas. After preliminary decarbonization, flue gas is introduced into the rich liquid obtained and fed into the micro-interface generator to form a stable gas-liquid mixture. The presence of the shuttle agent further enhances the proton receiver's ability to capture carbon dioxide. The activity of the receiver is enhanced because the reduction in bubble size generates a free radical effect, causing the chemical bonds in the solution to break, forming hydroxyl radicals and protons. Due to the presence of the proton receiver, these broken protons and hydroxyl radicals interact with the proton receiver, preventing them from binding with the shuttle and occupying carbon dioxide sites on the shuttle, thus reducing its carbon dioxide capture efficiency. During the initial decarbonization of flue gas, the presence of the shuttle ensures the presence of carbonic acid in the resulting rich solution. Due to the instability of carbonic acid, it decomposes to produce hydrogen ions and bicarbonate ions. These hydrogen ions can also combine with the proton receiver, increasing its activity. Furthermore, the presence of the proton receiver prevents hydrogen ions from binding with the shuttle and occupying carbon dioxide sites, thus maintaining its carbon dioxide capture efficiency during the initial decarbonization process. Therefore, this invention combines a shuttle and a proton receiver, using the shuttle to enhance the proton receiver's activity while ensuring that the shuttle's carbon dioxide capture efficiency remains unaffected. In summary, the molar ratio of shuttle to proton acceptor is crucial for this invention. In the decarbonization method of this invention, if there is too much shuttle, the amount of proton acceptor will be correspondingly reduced, causing some carbon dioxide sites on the shuttle to be occupied by hydrogen ions. This affects the shuttle's carbon dioxide capture effect and the reaction rate. If there is too little shuttle, there will be too much proton acceptor, and some of the proton acceptor will not be able to improve its activity. Furthermore, too little shuttle will reduce the initial decarbonization reaction rate and correspondingly reduce its capture of carbon dioxide in the flue gas.

[0070] By comparing Example 1 and Comparative Examples 5-6, it is evident that the diameter of the microbubbles is crucial for this invention. This is because a suitable microbubble size allows for the formation of a stable gas-liquid mixture from the flue gas and the rich liquid. The smaller bubble size generates free radical and interfacial electric field effects, enabling the absorbent to achieve a higher loading. The free radical effect enhances the absorbent's activity, thereby reducing the overall energy consumption of the process. Therefore, in this invention, a microbubble diameter of 100-300 μm effectively enhances the absorbent's activity through its free radical effect, leading to better carbon dioxide absorption. If the microbubble diameter is too large, it fails to generate the free radical and interfacial electric field effects, hindering absorbent activity and affecting decarbonization. Conversely, if the microbubbles are too small, a stable gas-liquid mixture cannot be formed.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A CO2 absorbent, characterized in that, The absorbent is mainly composed of a shuttle agent and a proton acceptor; Preferably, the molar ratio of the shuttle agent to the proton acceptor is 1:1 to 1:5; Preferably, the molar ratio of the shuttle agent to the proton acceptor is 1:

3.

2. The absorbent according to claim 1, characterized in that, The shuttle agent is one or more of 2-amino-2-methyl-1-propanol, monoethanolamine, piperazine, N-methylpiperazine, benzylamine, and piperidine.

3. The absorbent according to claim 2, characterized in that, The shuttle agent is a mixture of N-methylpiperazine and monoethanolamine.

4. The absorbent according to claim 3, characterized in that, The molar ratio of N-methylpiperazine to monoethanolamine in the shuttle agent is (2:1)-(1:3).

5. The absorbent according to claim 4, characterized in that, The molar ratio of N-methylpiperazine to monoethanolamine in the shuttle agent is 1:

1.

6. The absorbent according to claim 1, characterized in that, The proton acceptor is one or more of diethanolamine, diisopropanolamine, triethanolamine, and methyldiethanolamine.

7. The absorbent according to claim 6, characterized in that, The proton acceptor is methyldiethanolamine.

8. A method for enhanced amine-based flue gas decarbonization using the CO2 absorbent as described in any one of claims 1-7, characterized in that, Includes the following steps: Prepare the absorbent and preheat it; Flue gas is introduced into the preheated absorbent to carry out a decarbonization reaction, resulting in a rich liquid. Flue gas, broken into microbubbles, is introduced into the rich liquid again to obtain a gas-liquid mixture; High-purity CO2 is obtained by gas-liquid separation and regeneration of the supersaturated rich liquid.

9. The decarbonization method according to claim 8, characterized in that, The microbubbles are micron-sized bubbles with a diameter of 100-300 μm; Preferably, the diameter of the microbubbles is 300 μm.

10. A flue gas decarbonization system using the CO2 absorbent as described in any one of claims 1-7 and employing the flue gas decarbonization method as described in claim 9, characterized in that, It includes a gas scrubbing tower, a micro-interface reaction tower, a gas-liquid separator, and a regeneration tower connected in sequence.

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