A microbubble absorption and gas-liquid separation device and its application in carbon dioxide absorption.

Abstract

This application discloses a carbon dioxide microbubble absorption device. It includes a microbubble dispersion device, an absorption device, and a gas-liquid separation device. The microbubble dispersion device is filled with a Janus hollow fiber membrane. The hydrophilic layer of the Janus hollow fiber membrane has a water contact angle of less than 70°, and the hydrophobic layer has a water contact angle of greater than 100°. The gas-liquid separation device is filled with a hydrophobic separation membrane. The hydrophobic separation membrane is selected from at least one of polytetrafluoroethylene hollow fiber membrane, polypropylene hollow fiber membrane, and polyvinylidene fluoride hollow fiber membrane. The Janus separation membrane enables low-cost, continuous preparation of micron-sized bubbles. The use of micron-sized bubbles can significantly enhance gas-liquid mass transfer, improve CO2 absorption efficiency, and increase the CO2 concentration in the rich absorbent liquid.

Description

Technical Field

[0001] This application relates to a microbubble absorption and gas-liquid separation device and its application in carbon dioxide absorption, belonging to the field of chemical separation technology. Background Technology

[0002] Carbon dioxide emission reduction is a global issue that is closely related to economic and social development and energy use. Therefore, it requires close cooperation among countries to solve it together.

[0003] In my country, coal-fired power plants, as a fixed and concentrated source of CO2 emissions, account for over 70% of electricity generation and more than 95% of total CO2 emissions from power generation. Flue gas from coal-fired power plants is characterized by large flow rates, low CO2 partial pressure, and stable flow. This facilitates CO2 capture, but also requires more energy due to the high CO2 partial pressure. Chemical CO2 absorption technology based on absorbents was first proposed in 1930, primarily for CO2 removal from natural gas. Later, scholars proposed applying this technology to CO2 removal from flue gas emitted by coal-fired power plants. Chemical absorption process equipment mainly includes a pretreatment tower, absorption unit (tower), regeneration unit (tower), lean and rich liquid heat exchanger, and reboiler. Chemical absorption is currently the most mature carbon capture technology. The main factors limiting its large-scale commercial application are its high investment cost and high operating costs.

[0004] One problem hindering the high cost of CO2 chemical absorption towers is that the CO2-containing gas mixture flows in millimeter- to centimeter-level gas streams or bubbles within the tower. This results in a small gas-liquid contact area, limiting mass transfer and leading to large, complex towers with high fixed costs. Furthermore, problems such as flooding, entrainment, and channeling in packed towers or absorption towers severely restrict the stable operation of the chemical absorption process.

[0005] Chemical absorption is essentially a gas-liquid reaction process, with mass transfer and reaction rate being the key factors limiting its rate. The mass transfer rate is determined by the changes in gas composition before and after treatment and the gas-liquid contact area, while the reaction rate is primarily influenced by the properties of the absorbent. The main problem with chemical absorption is its high equipment investment and operating costs, which have become a bottleneck restricting its application in CO2 capture. Under the condition of a 90% flue gas capture rate in power plants, the equipment investment for chemical absorption is 2000-4000 yuan / kW, accounting for about 70% of the power plant's investment, and the operating cost reaches 250-300 yuan / ton of CO2. Regarding equipment investment, existing absorption devices are mostly bubble columns and absorption towers. These devices have a small specific surface area, can only generate millimeter-sized bubbles or gas flows, have insufficient gas-liquid contact area, and low mass transfer efficiency, resulting in large absorption equipment size, high investment, and susceptibility to channeling and flooding problems during operation. In terms of operating costs, organic amine solutions need to be heated from 40℃ to 100-120℃ to complete CO2 desorption, and the absorbent contains a large amount of water with high specific heat, resulting in high energy consumption for desorption. The energy consumption of the chemical absorption stage accounts for 60-70% of the entire carbon capture process.

[0006] Compared to millimeter-sized bubbles, micrometer-sized bubbles have the following advantages in chemical absorption processes:

[0007] (1) Increased gas-liquid contact area

[0008] As the microbubble particle size decreases, its gas-liquid contact area increases significantly. If the average particle size of the microbubble is about 50-100μm, its effective gas-liquid contact area is 50-100 times that of the traditional bubble column, which greatly enhances the gas-liquid mass transfer rate.

[0009] (2) High CO2 partial pressure

[0010] For microbubbles, due to their small radius of curvature and the liquid surface tension, the pressure inside the bubble is higher than the pressure of the liquid at its location. This higher pressure P follows the Young-Laplace equation:

[0011] The gas pressure in the microbubble is P = 2σ / r (1)

[0012] In equation (1), σ is the surface tension of the liquid phase; r is the radius of the microbubble. The smaller the size of the microbubble particles, the higher the gas pressure inside them, which leads to an increase in the partial pressure of CO2 inside the bubble, an increase in the driving force for gas film mass transfer, and enhanced gas phase mass transfer;

[0013] (3) Improved mass transfer capacity

[0014] According to literature research, compared with large bubbles, microbubbles have thinner gas and liquid films, higher mass transfer coefficients, and shorter mass transfer distances, which can effectively improve the gas-liquid mass transfer rate.

[0015] (4) Microbubbles have a carrying effect, which improves operational stability.

[0016] As the bubble size decreases, the probability of bubble aggregation decreases, the buoyancy of the bubbles in the absorbent decreases, and the bubble and absorbent are in a stable foam fluid state, so that bubbling and flooding will not occur in the absorption tower, and the operational stability will be greatly increased.

[0017] In summary, microbubbles outperform millimeter-sized bubbles in absorption towers in both gas-liquid mass transfer area and mass transfer coefficient. The applicant proposes to prepare CO2-containing flue gas or mixed gas into 50-100 μm microbubbles and disperse them in the absorbent. Utilizing the inherent properties of microbubbles, this method aims to enhance the chemical absorption process, potentially breaking the limitations of existing absorption devices on the type and concentration of absorbents, broadening the range of absorbent types and concentrations that can be used, significantly reducing the size and investment of chemical absorption devices, and decreasing energy consumption and operating costs in the desorption process. This provides a new approach to carbon removal technology using chemical absorption.

[0018] Flue gas emissions are large, with low CO2 content. To achieve good chemical absorption efficiency, microbubble preparation technology should meet the requirements of high gas production, low production cost, and narrow bubble size distribution. Microbubble preparation technologies include pressurized dissolved gas release, air dispersion, electrolysis, and air flotation pump gas generation. However, these technologies have drawbacks such as high energy consumption, wide bubble diameter distribution, limitations imposed by gas solubility, and low gas production efficiency, making them unsuitable for the chemical absorption process of flue gas. The method of preparing microbubbles by dispersing gas using microporous membranes can meet the above requirements, but the wetting problem of the membrane pores limits its long-term use.

[0019] Comparison of microbubble preparation methods and performance

[0020]

[0021] Therefore, Janus separation membranes can prepare microbubbles at low cost and continuously, making them particularly suitable for decarbonization processes of large-volume CO2 mixtures such as flue gas. However, the characteristics of microbubbles lead to severe foaming during chemical absorption. The presence of foam causes serious gas-liquid entrainment problems. In actual operation, demisters need to be added to both the absorption tower and the packed tower to remove foam, but the demisting effect is poor, and a large amount of foam is still entrained during use, leading to operational instability and significant absorbent loss. Therefore, improving the defoaming effect of gas-liquid separation devices is of great significance for improving the stable operation of microbubble technology in CO2 chemical absorption processes. Summary of the Invention

[0022] To address this issue, this application employs a hollow fiber hydrophobic membrane with high specific surface area and high penetration pressure for gas-liquid separation. The high specific surface area of ​​the hydrophobic membrane increases the probability of foam contact with the membrane material, enhancing foam removal. Simultaneously, the membrane pores block the absorbent liquid while allowing the removed gas to escape through the pores, thus achieving gas-liquid separation. Compared to traditional gas-liquid separation devices, this method offers advantages such as smaller size, higher defoaming efficiency, suppression of gas-liquid entrainment, and reduced absorbent loss.

[0023] This addresses the issue of high equipment investment and operating costs in traditional absorption towers used for CO2 capture via chemical absorption methods, due to factors such as small gas-liquid contact area and insufficient mass transfer driving force.

[0024] To address the above issues, this application employs a combination of Janus separation membranes and hydrophobic separation membranes to replace the traditional absorption tower and gas-liquid separation device in the absorption process. This significantly increases the gas-liquid contact area, enhances mass transfer, and reduces equipment investment and operating energy consumption in the chemical absorption process.

[0025] The CO2 absorption and gas-liquid separation method based on the combined use of Janus separation membrane and hydrophobic separation membrane is characterized by the use of membrane separation technology to replace the traditional absorption tower and gas-liquid separation device.

[0026] According to one aspect of this application, a carbon dioxide microbubble absorption device is provided, the carbon dioxide microbubble absorption device comprising a microbubble dispersion device, an absorption device, and a gas-liquid separation device;

[0027] The microbubble dispersion device is filled with a Janus hollow fiber membrane.

[0028] The water contact angle of the hydrophilic layer of the Janus hollow fiber membrane is less than 70°, and the water contact angle of the hydrophobic layer is greater than 100°.

[0029] Optionally, the water contact angle of the hydrophilic layer is less than 65°, and the water contact angle of the hydrophobic layer is greater than 110°.

[0030] The Janus hollow fiber membrane has an inner diameter of 0.7–0.8 mm, an outer diameter of 1.2–1.4 mm, and a pore size of 0.2–0.3 μm.

[0031] The length of the membrane filaments in the Janus hollow fiber membrane ranges from 20 to 100 cm;

[0032] The gas-liquid separation device is filled with a hydrophobic separation membrane;

[0033] The hydrophobic separation membrane is selected from at least one of polytetrafluoroethylene hollow fiber membrane, polypropylene hollow fiber membrane, and polyvinylidene fluoride hollow fiber membrane.

[0034] The length of the membrane filaments in the hydrophobic separation membrane ranges from 20 to 100 cm;

[0035] The microbubble dispersion device is equipped with inlet I-1, inlet I-2, and outlet I;

[0036] The inlet I-1 is the absorbent inlet;

[0037] The inlet I-2 is a mixed gas inlet;

[0038] The absorption device is equipped with an inlet II and an outlet II;

[0039] The gas-liquid separation device is equipped with inlet III, outlet III-1, and outlet III-2.

[0040] The outlet I is connected to the inlet II pipeline;

[0041] The outlet II is connected to the inlet III pipeline.

[0042] The Janus hollow fiber membrane is obtained through the following steps:

[0043] The inner and outer film-forming solutions are co-extruded using a dual-channel nozzle with a spinning core solution to obtain a double-layer hollow fiber membrane. Modified monomers are then grafted onto the membrane to obtain the Janus hollow fiber membrane.

[0044] The inner layer film-forming solution contains film-forming polymer A, inner layer additive, organic solvent A, and amphiphilic polymer A;

[0045] The outer film-forming solution contains film-forming polymer B, outer layer additive, organic solvent B, and amphiphilic polymer B;

[0046] The amphiphilic polymer A and the amphiphilic polymer B are independently selected from amphiphilic polymer I and amphiphilic polymer II;

[0047] The amphiphilic polymers described herein contain both hydrophilic and hydrophobic structures. One type of amphiphilic polymer contains hydroxyl groups and hydrophobic groups, and is named amphiphilic polymer I. The other type of amphiphilic polymer is named amphiphilic polymer II. The amphiphilic polymers are synthesized via free radical polymerization, selecting hydrophilic and hydrophobic monomers, with the monomers containing olefin structures.

[0048] The amphiphilic polymer I is obtained by polymerizing hydrophilic monomer I and hydrophobic monomer I;

[0049] The amphiphilic polymer II is obtained by polymerizing hydrophilic monomer II and hydrophobic monomer II;

[0050] The hydrophilic monomer I is selected from olefin monomers containing hydroxyl groups, specifically from at least one of allyl alcohol and butenol;

[0051] The hydrophilic monomer II is selected from at least one of polyethylene glycol acrylate and vinylpyrrolidone;

[0052] The hydrophobic monomer I and the hydrophobic monomer II are independently selected from at least one of styrene, methyl acrylate, acrylonitrile, and hexafluorobutyl acrylate;

[0053] The amphiphilic polymer A in the inner layer film-forming solution and the amphiphilic polymer B in the outer layer film-forming solution are different from each other.

[0054] The modified monomer is selected from at least one of hexafluorohexyltriethoxysilane and tridecafluorooctyltriethoxysilane.

[0055] The film-forming polymer A and film-forming polymer B are independently selected from at least one of polysulfone, polyethersulfone, polyvinylidene fluoride, polymethyl methacrylate, polyvinyl chloride, and polyacrylonitrile;

[0056] The inner layer additive is selected from at least one of polyethylene glycol, anhydrous lithium chloride, and polyvinylpyrrolidone.

[0057] The outer layer additive is selected from at least one of polyethylene glycol, anhydrous lithium chloride, and polyvinylpyrrolidone.

[0058] The organic solvent A and organic solvent B are independently selected from at least one of dimethylacetamide, dimethylformamide, N-methylpyrrolidone, and tetrahydrofuran;

[0059] The film-forming polymer A in the inner layer film-forming solution has a mass concentration of 10-25 wt%, the inner layer additive has a mass concentration of 5-20 wt%, and the amphiphilic polymer A has a mass concentration of 1-20 wt%.

[0060] Optionally, the mass concentration of film-forming polymer A in the inner layer film-forming solution is any value of 10wt%, 15wt%, 20wt%, 25wt%, or any range between two of these values; the mass concentration of the inner layer additive is any value of 5wt%, 10wt%, 15wt%, 20wt%, or any range between two of these values; and the mass concentration of amphiphilic polymer A is any value of 1wt%, 5wt%, 10wt%, 15wt%, 20wt%, or any range between two of these values.

[0061] The outer film-forming polymer B in the outer film-forming solution has a mass concentration of 10–25 wt%, the outer layer additive has a mass concentration of 5–20 wt%, and the amphiphilic polymer B has a mass concentration of 1–20 wt%.

[0062] Optionally, the mass concentration of film-forming polymer B in the outer film-forming solution is any value of 10wt%, 15wt%, 20wt%, 25wt%, or any range between two of these values; the mass concentration of the outer additive is any value of 5wt%, 10wt%, 15wt%, 20wt%, or any range between two of these values; and the mass concentration of amphiphilic polymer B is any value of 1wt%, 5wt%, 10wt%, 15wt%, 20wt%, or any range between two of these values.

[0063] The polymerization temperature is 50–80°C;

[0064] Optionally, the polymerization temperature is any value of 50°C, 60°C, 70°C, 80°C, or a range between any two.

[0065] The polymerization time is 40–600 min;

[0066] Optionally, the aggregation time is any value of 40 min, 600 min, or a range between both.

[0067] The polymerization involves a catalyst;

[0068] The catalyst is selected from at least one of azobisisobutyronitrile and benzoyl peroxide.

[0069] The grafted modified monomer includes the following steps:

[0070] The double-layer hollow fiber membrane is immersed in a solvent solution containing modified monomers;

[0071] The solvent is selected from at least one of n-hexane, cyclohexane, n-heptane, toluene, ethylbenzene, and ethyl acetate;

[0072] In the solvent solution containing the modified monomer, the mass ratio of the modified monomer to the solvent is 0.01 to 0.15:1.

[0073] Optionally, in the solvent solution containing the modified monomer, the mass ratio of the modified monomer to the solvent is any value among 0.01:1, 0.05:1, and 0.15:1, or any range between two of them.

[0074] The inner layer film-forming solution is stirred I;

[0075] The temperature of stirring I is 10–120°C;

[0076] Optionally, the temperature of the stirring I is any value or a range between 10℃, 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, and 120℃.

[0077] The stirring time for the first stirring step is 1 to 20 hours.

[0078] Optionally, the stirring time I is any value among 1h, 5h, 10h, 15h, and 20h, or a range between any two.

[0079] The outer film-forming solution is stirred (II);

[0080] The temperature of stirring II is 10–120°C;

[0081] Optionally, the temperature of the stirring II is any value or a range between 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, and 120°C.

[0082] The stirring time for the second stage is 1 to 20 hours.

[0083] Optionally, the stirring time II is any value among 1h, 5h, 10h, 15h, and 20h, or a range between any two.

[0084] The spinning core solution is selected from water or an aqueous solution containing ethanol, methanol, or an organic solvent;

[0085] The aqueous solution containing ethanol, methanol, or an organic solvent has a mass concentration of 10–80 wt%.

[0086] The total extrusion volume of the inner layer film-forming solution and the outer layer film-forming solution is 3-20 mL / min;

[0087] Optionally, the total extrusion volume of the inner layer film-forming solution and the outer layer film-forming solution is any value among 3 mL / min, 5 mL / min, 10 mL / min, 15 mL / min, and 20 mL / min, or a range between any two.

[0088] The ratio of the extrusion amount of the inner layer film-forming solution to the outer layer film-forming solution is 0.1 to 10:1.

[0089] Optionally, the ratio of the extrusion amount of the inner layer film-forming liquid to the outer layer film-forming liquid is any value among 0.1:1, 0.5:1, 1:1, 5:1, and 10:1, or any range between the two.

[0090] The double-layer hollow fiber membrane is gel-formed.

[0091] The solution used for gel molding is selected from water or an aqueous solution containing ethanol, methanol, or organic solvents.

[0092] The aqueous solution containing ethanol, methanol, or an organic solvent has a mass concentration of 10–80 wt%.

[0093] The Janus hollow fiber membrane undergoes washing, solvent exchange, and drying.

[0094] The washing is water washing;

[0095] The solvent exchange is a solvent exchange using ethanol and n-hexane as solvents;

[0096] The drying method is natural air drying or ethanol-n-hexane replacement air drying.

[0097] Janus hollow fiber membranes with different hydrophilic / hydrophobic layer thicknesses, hydrophilic / hydrophobic properties, and pore structures can be prepared by changing the composition, flow rate, core solution, and gel bath composition of the inner and outer membrane-forming solutions.

[0098] The Janus hollow fiber membrane packed in the microbubble dispersion device has a packing density of 5-65%.

[0099] The packing density of the hydrophobic separation membrane packed in the gas-liquid separation device is 5-65%.

[0100] The number of the microbubble dispersion device and the gas-liquid separation device is independently selected from positive integers between 1 and 10;

[0101] Multiple microbubble dispersion devices are connected in series or parallel.

[0102] Multiple gas-liquid separation devices are connected in series or in parallel.

[0103] According to another aspect of this application, a method for carbon dioxide absorption and gas-liquid separation is provided, employing the aforementioned carbon dioxide microbubble absorption device.

[0104] (1) Using Janus separation membrane instead of absorption tower, the mixed gas containing CO2 is converted into microbubbles and dispersed in the absorbent solution through Janus separation membrane to form CO2-rich absorbent liquid;

[0105] (2) Use a polytetrafluoroethylene (PTFE) separation membrane to replace the gas-liquid separation device. Construct a membrane contactor through the PTFE separation membrane to defoam the CO2-rich absorbent liquid and complete the gas-liquid separation.

[0106] The CO2 absorption and gas-liquid separation method based on the combined use of Janus and hydrophobic separation membranes employs an apparatus comprising an absorbent storage tank, a centrifugal pump, a Janus membrane module, a CO2 mixture, an absorption tube, a gas-liquid separator, and a gas flow meter, connected in sequence. The liquid outlet of the gas-liquid separator is connected to the inlet of the absorbent storage tank, and the outlet of the absorbent storage tank is connected to the liquid inlet of the Janus membrane module. The CO2-containing gas mixture flows into the hydrophobic layer of the Janus membrane and flows out through the hydrophilic layer, forming microbubbles upon contact with the absorbent. These microbubbles react with the absorbent inside the Janus membrane module and the absorption tube to obtain a CO2-rich absorbent.

[0107] In the carbon dioxide microbubble absorption device, the gas pressure is 0.02–10 MPa, the liquid pressure is 0.01–10 MPa, and the gas-liquid pressure difference is 0.001–0.3 MPa.

[0108] A membrane contactor constructed from polytetrafluoroethylene (PTFE) hollow fibers is used for gas-liquid separation of CO2-rich absorbent. The gas-liquid separation device includes a rich-liquid transfer pump, a PTFE hollow fiber membrane module, and valves. These components are connected sequentially.

[0109] The CO2-rich absorbent is pumped into the shell side of the PTFE hollow fiber membrane module by a rich liquid transfer pump. After the CO2-rich absorbent comes into contact with the PTFE hollow fiber membrane, the foam is squeezed and ruptured, and the gas is discharged from the membrane pores. The absorbent that has been degassed is trapped by the hydrophobic membrane pores and flows out from the shell side of the PTFE hollow fiber membrane module, thus achieving gas-liquid separation.

[0110] The gas-liquid separation device has a temperature of 10–60°C and a pressure of 0.01–0.05 MPa.

[0111] Optionally, in the gas-liquid separation device, the temperature is 40–60℃ and the pressure is 0.02–0.04 MPa.

[0112] The beneficial effects that this application can produce include:

[0113] (1) The carbon dioxide microbubble absorption device and CO2 absorption / gas-liquid separation method provided in this application achieve the purpose of low-cost, continuous preparation of micron-sized bubbles through Janus separation membrane. Micron-sized bubbles can significantly enhance gas-liquid mass transfer, improve CO2 absorption efficiency, and increase the CO2 concentration in the rich absorbent liquid;

[0114] (2) The carbon dioxide microbubble absorption device and CO2 absorption / gas-liquid separation method provided in this application achieve foam elimination and enhance gas-liquid separation through the high specific surface area and hydrophobicity of the hydrophobic hollow fiber membrane;

[0115] (3) The carbon dioxide microbubble absorption device and CO2 absorption / gas-liquid separation method provided in this application can significantly reduce the investment and operating costs of CO2 absorption and gas-liquid separation devices, and have the advantages of small size, light weight and wide applicability. Attached Figure Description

[0116] Figure 1 This is a schematic diagram of the microbubble absorption and desorption device described in Embodiment 1 of this application; wherein, (1) absorption liquid storage tank, (2) centrifugal pump, (3) Janus membrane module (microbubble dispersion device), (4) CO2 mixed gas, (5) absorption tube, and (6) gas-liquid separation device.

[0117] Figure 2 This is a schematic diagram of the gas-liquid separation device in the microbubble absorption and desorption device described in Embodiment 1 of this application; wherein, (7) CO2-rich absorbent inlet, (8) rich liquid booster pump, (9) hydrophobic hollow fiber membrane contactor, (10) valve, (11) desorption tower, and (12) CO2 gas outlet. Detailed Implementation

[0118] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0119] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0120] Device example 1

[0121] Figure 1 This is a schematic diagram of the microbubble absorption described in Embodiment 1 of this application;

[0122] (1) The absorbent storage tank is connected to (3) the Janus membrane module via (2) the centrifugal pump line;

[0123] (4) The CO2 mixture is connected to the pipeline of (3) Janus membrane module;

[0124] (3) Connect the Janus membrane module to the (5) absorption tube pipeline;

[0125] (5) The absorption pipe is connected to the (6) gas-liquid separator pipeline.

[0126] Figure 2 This is a schematic diagram of the gas-liquid separation device described in Embodiment 1 of this application;

[0127] (7) The CO2-rich absorbent inlet enters the (9) hydrophobic hollow fiber membrane contactor via the (8) rich liquid booster pump. The carbon dioxide gas is discharged through the (12) CO2 gas outlet. The liquid is controlled by the (10) valve to flow into the (11) desorption tower for desorption.

[0128] Preparation Example 1

[0129] Dissolve 8g of allyl alcohol and 2g of styrene in 415g of dimethylacetamide, add 0.1g of azobisisobutyronitrile, purge with nitrogen gas, and heat and stir at 50℃ for 40min to obtain a solution containing amphiphilic polymer I. Add 50g of PVDF and 25g of polyethylene glycol 400 to this solution to obtain the inner layer film-forming solution.

[0130] Take 20g of vinylpyrrolidone and 5g of styrene, dissolve them in 350g of dimethylacetamide, add 0.5g of azobisisobutyronitrile, and heat and stir at 60℃ for 80min to obtain a solution containing amphiphilic polymer II. Add 100g of PVDF and 25g of polyethylene glycol 400 to this solution to obtain the outer layer film-forming solution.

[0131] The inner and outer layer film-forming solutions were added to the inner and outer layer film-forming solution spinning tanks, respectively, and vacuum degassing was performed for 24 hours. The outer and inner layer film-forming solutions were then fed into a dual-channel nozzle, using ethanol as the core solution and deionized water as the outer gel bath, to spin a double-layer hollow fiber membrane. The flow rate of the outer layer film-forming solution was 5 ml / min, and the flow rate of the inner layer film-forming solution was 0.5 ml / min, resulting in a double-layer hollow fiber membrane. The obtained double-layer hollow fiber membrane was immersed in a grafting modification solution, and the grafting reaction was carried out for 24 hours. The grafting modification solution consisted of 1 g of hexafluorohexyltriethoxysilane and 100 g of n-hexane. The grafted double-layer membrane was rinsed in deionized water for 48 hours, and then dried using a successive ethanol-n-hexane displacement process to obtain a Janus hollow fiber membrane. This Janus membrane has a hydrophobic inner layer and a hydrophilic outer layer structure.

[0132] Example 1

[0133] The apparatus described in Example 1 was used. The Janus membrane obtained in Preparation Example 1 was used.

[0134] The outer layer is a hydrophilic layer with a water contact angle of 35°, and the inner layer is a hydrophobic layer with a water contact angle of 135°. The hollow fiber membrane has an inner diameter of 0.7 mm and an outer diameter of 1.2 mm, and the Janus membrane has a pore size of 0.3 μm. 300 hollow fiber membranes were used to fabricate a hollow fiber membrane module with a fiber packing density of 55% and an effective length of 100 cm.

[0135] A N2 / CO2 mixture (85% N2, 15% CO2) and an absorbent (composed of 5% anhydrous piperazine, 38% N-methyl-diethanolamine, and 57% deionized water) were introduced into the Janus membrane module under pressure through the inlet. The mixture flowed from the outer surface of the Janus hollow fiber membrane into the membrane interior, combining with the absorbent to form microbubbles. The pressure of the mixed gas was 0.15 MPa, and the pressure of the absorbent was 0.02 MPa. The microbubbles combined with the absorbent inside the membrane module and in the subsequent absorption tubes. Gas-liquid separation was achieved through a gas-liquid separator, and the CO2 content in the mixed gas was tested.

[0136] The test results are as follows: the average diameter of the microbubbles in the mixed gas is 30 μm, and the processing capacity of the mixed gas is 7 m³. 3 / m 2 The CO2 absorption rate in the mixed gas after absorption is 99.97%, and the absorption rate of the absorbent liquid can reach 75%, allowing for long-term stable operation.

[0137] The gas-liquid separator consists of a polytetrafluoroethylene (PTFE) hollow fiber membrane module. The PTFE separation membrane has a water contact angle of 115°, the hollow fiber membrane module has a packing density of 55%, and the membrane module is 100 cm long. The CO2-rich absorbent flows through the hollow fiber membrane module, is pressurized to 0.03 MPa, and flows into the hollow fiber membrane contactor shell. After the absorbent contacts the hollow fiber membrane, air bubbles are eliminated, and the gas flows out through the membrane pores.

[0138] After the CO2-rich absorbent liquid is degassed, it can flow out and enter the desorption tower for desorption.

[0139] Before entering the gas-liquid separation device, the gas content in the CO2-rich absorbent liquid exceeds 85%, and after flowing through the polytetrafluoroethylene hollow fiber membrane module, the gas content is less than 2%.

[0140] Preparation Example 2

[0141] Take 30g of butenol and 10g of methyl methacrylate, dissolve them in 350g of dimethylacetamide, add 0.1g of azobisisobutyronitrile, purge with nitrogen gas, and heat and stir at 70℃ for 200min to obtain a solution containing amphiphilic polymer I. Add 100g of polyethersulfone and 20g of anhydrous lithium chloride to this solution to obtain the outer layer film-forming solution.

[0142] 40g of polyethylene glycol acrylate and 10g of methyl acrylate were dissolved in 360g of dimethylacetamide. 0.5g of azobisisobutyronitrile was added, and the mixture was heated and stirred at 60℃ for 400min to obtain a solution containing amphiphilic polymer II. 70g of polyethersulfone and 20g of anhydrous lithium chloride were added to this solution to obtain the inner layer film-forming solution.

[0143] The inner and outer layer film-forming solutions were added to the inner and outer layer film-forming solution spinning tanks, respectively, and vacuum degassing was performed for 24 hours. The outer and inner layer film-forming solutions were then fed into a dual-channel nozzle, using water as the core liquid and propanol as the outer gel bath, to spin a double-layer hollow fiber membrane. The flow rate of the outer layer film-forming solution was 1.5 ml / min, and that of the inner layer film-forming solution was 3.5 ml / min, resulting in a double-layer hollow fiber membrane. The obtained double-layer hollow fiber membrane was immersed in a grafting modification solution, and the grafting reaction was carried out for 24 hours. The grafting modification solution consisted of 5 g of hexafluorohexyltriethoxysilane and 95 g of toluene. The grafted double-layer membrane was rinsed in deionized water for 48 hours, and then dried using a successive ethanol-n-hexane displacement process to obtain a Janus hollow fiber membrane. This Janus membrane has a hydrophobic outer layer and a hydrophilic inner layer structure.

[0144] Example 2

[0145] The apparatus described in Example 1 was used. The Janus membrane obtained in Preparation Example 2 was used.

[0146] The outer layer is a hydrophilic layer with a water contact angle of 25°, and the inner layer is a hydrophobic layer with a water contact angle of 125°. The hollow fiber membrane has an inner diameter of 0.8 mm and an outer diameter of 1.2 mm, and the Janus membrane has a pore size of 0.2 μm. 200 hollow fiber membranes were used to fabricate a hollow fiber membrane module with a fiber packing density of 50% and an effective length of 100 cm.

[0147] A N2 / CO2 mixture (88% N2, 12% CO2) and an absorbent (composed of 5% anhydrous piperazine, 38% N-methyl-diethanolamine, and 57% deionized water) were introduced into the Janus membrane module under pressure through the inlet. The mixture flowed from the outer surface of the Janus hollow fiber membrane into the membrane interior, combining with the absorbent to form microbubbles. The pressure of the mixed gas was 0.1 MPa, and the pressure of the absorbent was 0.02 MPa. The microbubbles combined with the absorbent inside the membrane module and in the subsequent absorption tubes. Gas-liquid separation was achieved through a gas-liquid separator, and the CO2 content in the mixed gas was tested.

[0148] The test results are as follows: the average diameter of the microbubbles in the mixed gas is 60 μm, and the processing capacity of the mixed gas is 3 m³. 3 / m 2 The CO2 absorption rate in the mixed gas after absorption is 99.95%, and the absorption rate of the absorbent liquid can reach 75%, allowing for long-term stable operation.

[0149] The gas-liquid separator consists of a polypropylene hollow fiber membrane module. The water contact angle of the polypropylene separation membrane is 110°, the packing density of the hollow fiber membrane module is 65%, and the length of the membrane module is 100 cm. The CO2-rich absorbent flows through the hollow fiber membrane module, is pressurized to 0.02 MPa, and flows into the shell of the hollow fiber membrane contactor. After the absorbent contacts the hollow fiber membrane, air bubbles are eliminated, and the gas flows out through the membrane pores. The CO2-rich absorbent, after the air bubbles are removed, can then enter a desorption tower for desorption.

[0150] Before entering the gas-liquid separation device, the gas content in the CO2-rich absorption liquid exceeds 78%, and after flowing through the polytetrafluoroethylene hollow fiber membrane module, the gas content is less than 3%.

[0151] Example 3

[0152] The apparatus described in Example 1 is used.

[0153] The Janus separation membrane, fabricated using polyvinylidene fluoride (PVDF), has an outer hydrophilic layer with a water contact angle of 55° and an inner hydrophobic layer with a water contact angle of 140°. The hollow fiber membrane has an inner diameter of 0.8 mm and an outer diameter of 1.4 mm, and the pore size of the Janus membrane is 0.2 μm. Two hundred hollow fiber membranes were used to construct a hollow fiber membrane module with a fiber packing density of 53% and an effective length of 100 cm.

[0154] A N2 / CO2 mixture (83% N2, 17% CO2) and an absorbent (composed of 5% anhydrous piperazine, 38% N-methyl-diethanolamine, and 57% deionized water) were introduced into the Janus membrane module under pressure through the inlet. The mixture flowed from the outer surface of the Janus hollow fiber membrane into the membrane interior, combining with the absorbent to form microbubbles. The pressure of the mixed gas was 0.1 MPa, and the pressure of the absorbent was 0.02 MPa. The microbubbles combined with the absorbent inside the membrane module and in the subsequent absorption tubes. Gas-liquid separation was achieved through a gas-liquid separator, and the CO2 content in the mixed gas was tested.

[0155] The test results are as follows: the average diameter of the microbubbles in the mixed gas is 50 μm, and the processing capacity of the mixed gas is 4 m³. 3 / m 2 The CO2 absorption rate in the mixed gas after absorption is 99.95%, and the absorption rate of the absorbent liquid can reach 85%, allowing for long-term stable operation.

[0156] The gas-liquid separator consists of a polyvinylidene fluoride (PVDF) hollow fiber membrane module. The PVDF separation membrane has a water contact angle of 145°, the hollow fiber membrane module has a packing density of 55%, and the membrane module length is 100 cm. The CO2-rich absorbent flows through the hollow fiber membrane module, is pressurized to 0.05 MPa, and flows into the shell of the hollow fiber membrane contactor. After contacting the hollow fiber membrane, the absorbent eliminates air bubbles, and the gas flows out through the membrane pores. The CO2-rich absorbent, after being degassed, can then enter a desorption tower for desorption.

[0157] Before entering the gas-liquid separation device, the gas content in the CO2-rich absorbent liquid exceeds 78%, and after flowing through the polytetrafluoroethylene hollow fiber membrane module, the gas content is less than 2%.

[0158] Comparative Example 1

[0159] An absorption tower (equipped with a simple degassing device) was used as the chemical absorption equipment. A N2 / CO2 mixture (83% N2, 17% CO2) and an absorbent (composed of 5% anhydrous piperazine, 38% N-methyl-diethanolamine, and 57% deionized water) were introduced into the absorption tower. The CO2 in the mixture combined with the absorbent, and preliminary gas-liquid separation was achieved through the degassing device. The CO2 content in the mixture was tested, and the CO2 absorption rate in the absorbed mixture was 90.15%, while the absorption rate of the absorbent liquid reached 65%. The gas content of the CO2-rich absorbent liquid was 55%, and after leaving the absorption tower, the gas content was 25%.

[0160] Conclusion: In ordinary absorption towers, the gas-liquid contact area is insufficient, resulting in poor CO2 absorption and a low absorption rate. Furthermore, existing degassing devices have poor degassing efficiency, leaving a high gas content in the CO2-rich absorbent, which complicates the subsequent desorption process.

[0161] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A carbon dioxide microbubble absorption device, characterized in that, The carbon dioxide microbubble absorption device includes a microbubble dispersion device, an absorption device, and a gas-liquid separation device. The microbubble dispersion device is filled with a Janus hollow fiber membrane. The water contact angle of the hydrophilic layer of the Janus hollow fiber membrane is less than 70°, and the water contact angle of the hydrophobic layer is greater than 100°. The Janus hollow fiber membrane has an inner diameter of 0.7~0.8 mm, an outer diameter of 1.2~1.4 mm, and a pore size of 0.2~0.3 μm. The gas-liquid separation device is filled with a hydrophobic separation membrane; The hydrophobic separation membrane is selected from at least one of polytetrafluoroethylene hollow fiber membrane, polypropylene hollow fiber membrane, and polyvinylidene fluoride hollow fiber membrane; The Janus hollow fiber membrane is obtained through the following steps: The inner and outer film-forming solutions are co-extruded using a dual-channel nozzle with a spinning core solution to obtain a double-layer hollow fiber membrane. Modified monomers are then grafted onto the membrane to obtain the Janus hollow fiber membrane. The inner layer film-forming solution contains film-forming polymer A, inner layer additive, organic solvent A, and amphiphilic polymer A; The outer film-forming solution contains film-forming polymer B, outer layer additive, organic solvent B, and amphiphilic polymer B; The amphiphilic polymer A and the amphiphilic polymer B are independently selected from amphiphilic polymer I and amphiphilic polymer II; The amphiphilic polymer I is obtained by polymerizing hydrophilic monomer I and hydrophobic monomer I; The amphiphilic polymer II is obtained by polymerizing hydrophilic monomer II and hydrophobic monomer II; The hydrophilic monomer I is selected from at least one of allyl alcohol and butenol; The hydrophilic monomer II is selected from at least one of polyethylene glycol acrylate and vinylpyrrolidone; The hydrophobic monomer I and the hydrophobic monomer II are independently selected from at least one of styrene, methyl acrylate, acrylonitrile, and hexafluorobutyl acrylate; The amphiphilic polymer A in the inner layer film-forming solution and the amphiphilic polymer B in the outer layer film-forming solution are different from each other. The modified monomer is selected from at least one of hexafluorohexyltriethoxysilane and tridecafluorooctyltriethoxysilane; The film-forming polymer A and film-forming polymer B are independently selected from at least one of polysulfone, polyethersulfone, polyvinylidene fluoride, polymethyl methacrylate, polyvinyl chloride, and polyacrylonitrile; The inner layer additive is selected from at least one of polyethylene glycol, anhydrous lithium chloride, and polyvinylpyrrolidone. The outer layer additive is selected from at least one of polyethylene glycol, anhydrous lithium chloride, and polyvinylpyrrolidone. The organic solvent A and organic solvent B are independently selected from at least one of dimethylacetamide, dimethylformamide, N-methylpyrrolidone, and tetrahydrofuran; The film-forming polymer A in the inner layer film-forming solution has a mass concentration of 10-25 wt%, the inner layer additive has a mass concentration of 5-20 wt%, and the amphiphilic polymer A has a mass concentration of 1-20 wt%. The outer film-forming polymer B in the outer film-forming solution has a mass concentration of 10-25 wt%, the outer layer additive has a mass concentration of 5-20 wt%, and the amphiphilic polymer B has a mass concentration of 1-20 wt%.

2. The carbon dioxide microbubble absorption device according to claim 1, characterized in that, The microbubble dispersion device is equipped with inlet I-1, inlet I-2, and outlet I; The inlet I-1 is the absorbent inlet; The inlet I-2 is a mixed gas inlet; The absorption device is equipped with an inlet II and an outlet II; The gas-liquid separation device is equipped with inlet III, outlet III-1, and outlet III-2.

3. The carbon dioxide microbubble absorption device according to claim 2, characterized in that, The outlet I is connected to the inlet II pipeline; The outlet II is connected to the inlet III pipeline.

4. The carbon dioxide microbubble absorption device according to claim 1, characterized in that, The Janus hollow fiber membrane filled in the microbubble dispersion device has a packing density of 5-65%.

5. The carbon dioxide microbubble absorption device according to claim 1, characterized in that, The packing density of the hydrophobic separation membrane packed in the gas-liquid separation device is 5-65%.

6. The carbon dioxide microbubble absorption device according to claim 1, characterized in that, The number of the microbubble dispersion device and the gas-liquid separation device is independently selected from positive integers between 1 and 10; Multiple microbubble dispersion devices are connected in series or in parallel. Multiple gas-liquid separation devices are connected in series or in parallel.

7. A method for carbon dioxide absorption and gas-liquid separation, characterized in that, The carbon dioxide microbubble absorption device according to any one of claims 1 to 6 is used.

8. The method according to claim 7, characterized in that, In the carbon dioxide microbubble absorption device, the gas pressure is 0.02~10 MPa, the liquid pressure is 0.01~10 MPa, and the gas-liquid pressure difference is 0.001~0.3 MPa.

9. The method according to claim 7, characterized in that, The gas-liquid separation device has a temperature of 10~60℃ and a pressure of 0.01~0.05Mpa.

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