Membrane coupled mixed amine solution carbon dioxide capture system

Abstract

The utility model belongs to carbon capture technology field, membrane coupling mixed amine solution's carbon dioxide capture system, include: absorption unit, absorption unit adopts hollow fiber membrane assembly, makes carbon -containing gas source and organic amine solution respectively from the both sides of membrane convection, heat exchange unit, heat exchange unit sets up between absorption unit and desorption unit, makes the rich amine liquid of high load carbon dioxide that absorption unit discharged and warmed up, and desorption unit, desorption unit adopts hollow fiber membrane assembly, makes the rich amine liquid after warming up flow in the one side of membrane, and the carbon dioxide that desorbs exports from the other side of membrane. The application constructs membrane coupling mixed amine's carbon dioxide capture system through the synergies of membrane and mixed amine, solves the problem that traditional amine absorption process is high in energy consumption and amine is degraded fast, and overcomes the defects that membrane separation technology is poor in low pressure adaptability and mixed membrane-amine system interface compatibility is insufficient.

Description

Technical Field

[0001] This invention belongs to the field of carbon capture technology, and particularly relates to a carbon dioxide capture system using a membrane-coupled mixed amine solution. Background Technology

[0002] Approximately 40% of global carbon dioxide emissions originate from coal-fired power plants, making the effective capture of carbon dioxide from these plants crucial for achieving carbon neutrality. Typical flue gas from coal-fired power plants is characterized by low carbon dioxide partial pressure (10–15%) and high flow rate (>10⁻⁶). 6 The presence of Nm3 / h and impurities (SOx / NOx) in the capture system presents requirements for high selectivity, low energy consumption, and pollution resistance.

[0003] Traditional amine absorption processes face numerous technical bottlenecks. In terms of energy consumption, the regeneration energy consumption of traditional MEA solvents is as high as 3.2–4.0 GJ / ton of carbon dioxide, leading to a 9–13% reduction in power plant net efficiency. This is mainly due to the latent heat of vaporization accounting for 28%, and the high specific heat capacity of water desorption. Although the later-developed MDEA / AMP mixed amine system saves 20–40% of regeneration heat compared to MEA, MDEA has a slow absorption rate, and AMP has an upper limit on its recycling capacity, limiting further improvements. Simultaneously, amine solvents undergo thermal degradation in the regeneration tower (120°C), generating irreversible products such as oxazolidinones. Especially under high O2 flue gas conditions, the MEA degradation rate can reach 3.5% / week, increasing solvent replenishment costs and posing problems of chemical degradation and corrosion.

[0004] Membrane separation technology also has limitations. Due to the flue gas pressure being close to atmospheric pressure (0.1 MPa), the driving force for membrane separation is insufficient. When the carbon dioxide partial pressure is <15 kPa, the capture rate of a single-stage membrane is <50%, requiring multi-stage series connection to improve efficiency, which increases energy consumption by 30%. Therefore, it has poor adaptability in low-pressure flue gas scenarios. Regarding material properties, commercial polymer membranes have a CO2 / N2 selectivity <50, while metal-doped MFI zeolite membranes, although improving selectivity (Cu~MFI: >150), suffer from a thickness inconsistency: membranes <10 μm are prone to mechanical failure, while those >100 μm experience a sharp drop in flux. Furthermore, there is a pore structure mismatch problem: N2 permeability surges when the pore size is >0.8 μm, while carbon dioxide flux is insufficient when the pore size is <0.1 μm.

[0005] While hybrid membrane-amine systems have made some progress and demonstrated potential for technological synergy—for example, membranes used as pretreatment units can increase flue gas carbon dioxide concentration (20% → 40%) and reduce amine absorption and regeneration energy consumption by 27.7%; amine-functionalized membranes (such as amine-modified MFIs) enhance carbon dioxide transport through chemisorption (increasing flux by 80%). However, this system still suffers from key drawbacks: poor interfacial compatibility, and the need for polymer membranes (such as...) When in contact with MDEA, swelling occurs, and the porosity decreases by 40%.

[0006] In summary, existing carbon dioxide capture technologies have shortcomings in terms of energy consumption, efficiency, and material performance, making it difficult to meet the actual needs of carbon dioxide capture in coal-fired power plants. Therefore, developing a more efficient, low-energy-consumption, and stable carbon dioxide capture system is of great practical significance and innovation necessity. Utility Model Content

[0007] To address the aforementioned technical problems, this application proposes a membrane-coupled carbon dioxide capture system for mixed amine solutions, the specific technical solution of which is as follows:

[0008] A membrane-coupled carbon dioxide capture system for mixed amine solutions includes:

[0009] The absorption unit employs a hollow fiber membrane module, allowing a carbon-containing gas source and an organic amine solution to convect from opposite sides of the membrane.

[0010] A heat exchange unit is provided between the absorption unit and the desorption unit to raise the temperature of the amine-rich liquid with a high carbon dioxide load discharged from the absorption unit.

[0011] The desorption unit employs a hollow fiber membrane module, allowing the heated amine-rich liquid to flow on one side of the membrane, while the desorbed carbon dioxide is discharged from the other side of the membrane.

[0012] Furthermore, the membrane of the hollow fiber membrane module is one of the following: superhydrophobic polyether ether ketone hollow fiber membrane, polytetrafluoroethylene hollow fiber membrane, Al2O3 ceramic membrane, ZIF-8 metal-organic framework membrane, GO / PI composite membrane, and SAPO-34 zeolite membrane.

[0013] Furthermore, the side of the desorption unit that discharges carbon dioxide is purged with low-pressure steam, steam, or nitrogen.

[0014] Furthermore, the side of the desorption unit that discharges carbon dioxide is set to a vacuum.

[0015] Furthermore, the lean solution discharged from the desorption unit is input into the heat exchange unit for heat exchange with the rich amine solution.

[0016] Furthermore, the surface area to volume ratio of the membrane in the hollow fiber membrane module is 1000–9000 m². 2 / m 3 .

[0017] The beneficial effects of this utility model are as follows:

[0018] (1) Significantly reduced energy consumption: On the one hand, the directional coupling of the membrane and the mixed amine reduces the additional energy consumption caused by feed compression, permeate side vacuuming or multi-stage series connection in the traditional process, thus reducing the reduction in net efficiency of the power plant; on the other hand, the membrane module of the regeneration unit can be loaded with metal catalysts, which can catalyze the decomposition of carbamate into carbon dioxide, directly reducing the energy demand of the regeneration process; in summary, the system regeneration energy consumption is reduced by 30% to 50% compared with the traditional MEA process (from 3.2 to 4.0 GJ / ton CO2 to 1.6 to 2.1 GJ / ton CO2).

[0019] (2) Comprehensive improvement of absorption performance: Mixed amine systems (such as combinations of MDEA and DEA, TEA and PZ, etc.) improve the inherent defects of single amines, solving the problem of slow absorption rate of MDEA and breaking through the bottleneck of limited AMP recycling capacity, significantly improving the system's absorption efficiency and recycling capacity for carbon dioxide; at the same time, the membrane module has a capacity of 1000-9000m 2 / m 3 Its high surface area to volume ratio provides a sufficient interface for gas-liquid contact, and the mass transfer efficiency is 15 times higher than that of traditional packed columns. The single-stage carbon dioxide absorption rate can reach 85% to 92%.

[0020] (3) Significantly enhances system stability: The membrane module has the characteristic of selectively permeating carbon dioxide, which can effectively block impurities such as O2, SOx, and NOx in flue gas, reducing the chemical degradation of amine solvents (the degradation rate is reduced from 3.5% / week in traditional MEA to <0.8% / week) and the corrosion of equipment (the annual corrosion rate is reduced from 0.5mm / year to <0.1mm / year) from the source. This not only reduces the cost of solvent replenishment and the frequency of equipment maintenance, but also ensures that the carbon dioxide removal rate remains stable at over 90% after the system has been running continuously for 150 to 200 hours.

[0021] (4) Optimize adaptability to low-pressure flue gas: Through the targeted design of membrane materials (such as SAPO-34 zeolite membrane, ZIF-8MOFs membrane, etc.) and the chemical reaction-driven mass transfer mechanism, the system can achieve a single-stage capture rate of more than 85% in a low-pressure flue gas environment with a carbon dioxide partial pressure of <15kPa without multi-stage series connection, overcoming the problem of insufficient driving force of traditional membrane separation technology in low-pressure scenarios.

[0022] (5) Significantly reduced space requirements: The high specific surface area of ​​membrane modules greatly reduces the size of the equipment. Compared with the traditional amine scrubbing tower process, the floor space is reduced by 50% to 60%, which not only reduces the difficulty of modifying the existing space of the power plant, but also reduces the visual impact, making it more suitable for the construction of new power plants and the upgrading and transformation of existing power plants. Attached Figure Description

[0023] Figure 1The diagram shows a schematic of a carbon dioxide capture system for a membrane-coupled mixed amine solution. Detailed Implementation

[0024] In the following description, certain specific details are set forth to provide a thorough understanding of various embodiments. However, those skilled in the art will understand that the present invention can be practiced without these details. In other instances, well-known structures have not been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments. Unless the context otherwise requires, throughout the specification and appended claims, the word "comprising" shall be interpreted in an open-ended, inclusive sense, i.e., as "including but not limited to".

[0025] The carbon dioxide capture system for membrane-coupled mixed amine solution of this application includes an absorption unit, a heat exchange unit, and a desorption unit.

[0026] In this absorption unit, a molecular sieve membrane separates a carbon-containing (carbon dioxide) gas source and an organic amine solution on opposite sides of the membrane. The two phases then undergo mass transfer through numerous micropores within the membrane. During membrane absorption, the membrane module selectively permeates carbon dioxide, effectively blocking impurities such as O2, SOx, and NOx in the flue gas. Under a certain gas-liquid pressure difference, a stable gas-liquid interface is formed at the membrane pores, allowing the solute to transfer mass between the two phases.

[0027] The membrane module (molecular sieve membrane) in the absorption unit provides a very high surface area to volume ratio for the contact of the mixed amine and carbon dioxide. Secondly, the membrane module has an extremely high surface area to volume ratio, providing an interface for the contact of the mixed amine and carbon dioxide. During operation, the carbon dioxide-containing gas flows through one side of the membrane, and the carbon dioxide permeates through the pores of the membrane to the other side, where it is absorbed by the amine solution flowing through that side.

[0028] In the membrane module, due to the chemical reaction between carbon dioxide and the absorbent solvent, the partial pressure of carbon dioxide on the permeate side can be considered close to zero. This overcomes the pressure ratio and concentration polarization problems encountered in traditional gas membrane separation processes. It does not require compression of the feed or application of a vacuum on the permeate side to generate the separation driving force to transport gas molecules through the membrane. The driving force depends on the performance of the mixed amine.

[0029] After carbon (carbon dioxide) gas enters the absorption unit, it is absorbed and discharged as low-carbon tail gas. The organic amine solution absorbs carbon dioxide and becomes a high-carbon dioxide-loaded amine solution.

[0030] The heat exchange unit is used to fully exchange heat between the rich liquid produced by the absorption unit and the lean liquid produced by the desorption unit. The temperature of the rich liquid increases and the temperature of the lean liquid decreases. The lean liquid with the lower temperature is then fed into the absorption unit, and the rich liquid with the higher temperature is fed into the desorption unit.

[0031] The desorption unit uses a molecular sieve membrane to separate carbon dioxide from a highly loaded amine solution.

[0032] In the desorption unit, a rich amine solution loaded with carbon dioxide is introduced into one side of the membrane module from one end, and a lean solution is removed from the opposite end, in which the carbon dioxide in the rich amine solution is removed.

[0033] A vacuum can also be applied to the other side of the molecular sieve membrane in the desorption unit to improve carbon dioxide separation efficiency.

[0034] It can also promote the removal of carbon dioxide in the pores of the hollow fibers of the molecular sieve membrane in the desorption unit.

[0035] See Figure 1 This is a schematic diagram of a carbon dioxide capture system for a membrane-coupled mixed amine solution, wherein the absorption unit is membrane module 10, the desorption unit is membrane module 30, and the heat exchange unit is heat exchanger 20.

[0036] Membrane module 10 uses a hollow fiber molecular sieve membrane, with the inside of the hollow fiber serving as the tube side and the outside of the hollow fiber serving as the shell side. Membrane module 10 has an input port 10a, an input port 20b, an output port 10c, and an output port 20d. Input port 10a inputs a carbon-containing (carbon dioxide) gas source to the shell side of membrane module 10, and input port 20b inputs lean liquid to the tube side of membrane module 10. The carbon dioxide in the flue gas is absorbed by the lean liquid on the other side of the membrane absorber. The gas after absorbing carbon dioxide is discharged through output port 10c, and the amine-rich liquid after absorbing carbon dioxide is discharged from output port 20d.

[0037] The circulation paths of the carbon (carbon dioxide) gas source and the absorbent in membrane module 10 are interchangeable.

[0038] Membrane module 2 30 uses a hollow fiber molecular sieve membrane, with the inside of the hollow fiber serving as the tube side and the outside of the hollow fiber serving as the shell side. Membrane module 2 30 has an input port 30a, an input port 40c, an output port 30b, and an output port 40d. The amine-rich solution after absorbing carbon dioxide is input into the shell side of membrane module 2 30 through input port 30a. After desorbing the carbon dioxide, the lean solution is discharged from output port 40d. The desorbed carbon dioxide is discharged from output port 30b. During this process, the amine-rich solution is introduced from the shell side of membrane module 2 30 and removes the carbon dioxide released from the solvent through the hollow fiber pores. The carbon dioxide is separated through the membrane pores and discharged through the tube side.

[0039] The circulation paths of the absorbent and the desorbed carbon dioxide in membrane module 2 30 can be interchanged.

[0040] To improve the desorption efficiency of carbon dioxide, the tube side of membrane module 2 30 is set as a low-pressure zone or even a vacuum zone; steam can also be input into the tube side of membrane module 2 30 through input interface 4 30c.

[0041] Heat exchanger 20 exchanges heat between membrane module 10 and membrane module 30. The amine-rich solution discharged from the output port 20d of membrane module 10 is heated by heat exchanger 20 and input through the input port 30a of membrane module 30. The desorbed lean solution is discharged from the output port 40d of membrane module 30, cooled by heat exchanger 20, and input through the input port 20b of membrane module 10.

[0042] Example 1

[0043] Superhydrophobic PEEK hollow fiber membrane coupled with K2CO3 / piperazine (PZ) mixed solvent system

[0044] Membrane material: Superhydrophobic polyetheretherketone (PEEK) hollow fiber membrane (specific surface area 2400 m²) 2 / m 3 ).

[0045] Mixed amine system: 25wt% K2CO3 + 5wt% PZ aqueous solution (PZ acts as a promoter to increase the carbon dioxide reaction rate, and K2CO3 reduces the liquid-side mass transfer resistance).

[0046] Absorption Unit: Simulated flue gas (13% carbon dioxide, 87% N2, containing 3% O2 ​​and 145 ppm SO2) enters the tube side of the membrane module, while a mixed amine-lean solution (40°C) comes into countercurrent contact with it in the shell side. The superhydrophobic properties of the PEEK membrane prevent wetting, and carbon dioxide is absorbed by the solvent through the membrane pores, achieving an absorption rate of 91%, with purified gas carbon dioxide <1.2%.

[0047] Heat exchange unit: rich amine solution (55℃) exchanges heat with regenerated lean solution (90℃), the rich solution is heated to 80℃, and the lean solution is cooled to 50℃.

[0048] Desorption unit: The rich amine solution is heated to 95°C and enters the regenerated membrane module. Low-pressure steam (100°C) is introduced into the shell side for purging. The carbon dioxide desorption purity reaches 99.5%. The regeneration energy consumption is reduced by 30% compared with MEA. The lean solution is recycled back to the absorption unit.

[0049] After 150 hours of continuous operation, the carbon dioxide removal rate remained stable at over 90%, and it exhibited excellent resistance to pollution from impurities such as SO2 and O2. After regeneration, the amine solution was recycled 50 times, and the absorption efficiency still maintained 92% of the initial value.

[0050] Example 2

[0051] PTFE hollow fiber membrane coupled with MDEA / diethanolamine (DEA) mixed solvent system

[0052] Membrane material: Polytetrafluoroethylene (PTFE) hollow fiber membrane (specific surface area 3000 m²) 2 / m 3 (Resistant to chemical corrosion), the surface is modified with fluoride to enhance hydrophobicity.

[0053] Mixed amine system: 35wt% MDEA + 10wt% DEA aqueous solution (DEA enhances reaction kinetics, MDEA expands cycle capacity).

[0054] Absorption Unit: Simulated flue gas (14% carbon dioxide, containing 300ppm NOx) flows through the shell side of the membrane module, while the lean amine solution (45℃) flows in countercurrent contact through the tube side. The PTFE membrane blocks NOx (rejection rate >90%), and carbon dioxide permeates through the membrane and reacts with the amine solution, achieving a single-stage absorption rate of 89%.

[0055] Desorption unit: The amine-rich liquid enters the regeneration tower after heat exchange (85°C). Vacuum is drawn on the membrane pore side (~0.07MPa) to promote carbon dioxide desorption. The heat requirement for regeneration of MDEA / DEA mixed liquid is reduced by 20% compared with pure MDEA.

[0056] After 100 hours of operation, the membrane permeation performance showed no decline.

[0057] Example 3

[0058] Al2O3 ceramic membrane coupled triethanolamine (TEA) / piperazine (PZ) mixed solvent system

[0059] Membrane material: Al2O3 ceramic membrane, not limited to DDR, MFI, CHA, etc. (specific surface area 1500m²) 2 / m 3 Temperature resistance ≤200℃), Cu load 2+ Enhance regeneration catalytic activity.

[0060] Mixed amine system: 20wt% TEA + 15wt% PZ aqueous solution (TEA has low regeneration energy consumption, and PZ accelerates carbon dioxide absorption).

[0061] Absorption Unit: Simulated flue gas (12% carbon dioxide, 50°C) enters the membrane module's tube side, while lean amine solution (50°C) flows counter-currently into the shell side. The high stability of the ceramic membrane ensures high carbon dioxide permeability, achieving an absorption rate of 92%.

[0062] Desorption unit: Amine-rich solution heated to 100℃, Cu2... + Catalyzed decomposition of carbamates, with N2 purging and desorption of carbon dioxide on the membrane side, achieving a purity of 99.2%.

[0063] It is resistant to high temperature and chemical corrosion, suitable for flue gas with high impurities, and has stable performance after 150 hours of continuous operation. Its mass transfer efficiency is 15 times higher than that of packed columns.

[0064] Example 4

[0065] ZIF-8MOFs membrane coupled N,N-dimethylethanolamine (DMEA) / activated K2CO3 mixed solvent system

[0066] Membrane material: ZIF-8 metal-organic framework membrane (pore size 0.34nm, carbon dioxide / nitrogen selectivity ≈120, specific surface area 2000m²) 2 / m 3 ).

[0067] Mixed amine system: 25wt% DMEA + 20wt% K2CO3 aqueous solution (DMEA resists degradation, K2CO3 increases the reaction rate).

[0068] Absorption Unit: Simulated flue gas (11% carbon dioxide, containing 200 ppm SO2) flows through the shell side of the membrane module, while the lean solution (40℃) flows in countercurrent contact through the tube side. The ZIF-8 membrane retains SO2 (>95%), and carbon dioxide is rapidly absorbed, achieving a removal rate of 90%.

[0069] Desorption unit: The rich liquid is heated to 90°C, and carbon dioxide is desorbed by vacuuming on the membrane pore side. The regeneration energy consumption is 2.0 GJ / ton of carbon dioxide.

[0070] High selectivity reduces liquid-side resistance, mixed solvent degradation rate is <0.8% / week, and the footprint is reduced by 60% compared to traditional processes.

[0071] Example 5

[0072] GO / PI composite film (graphene oxide-polyimide) coupled with 2-amino-2-methyl-1-propanol (AMP) / K2CO3 mixed solvent system

[0073] Membrane material: GO / PI composite membrane (specific surface area 1800 m²) 2 / m 3 (Resistant to acid corrosion).

[0074] Mixed amine system: 20wt% AMP + 25wt% K2CO3 aqueous solution (AMP increases the cycle capacity, K2CO3 accelerates the reaction).

[0075] Absorption Unit: Simulated flue gas from a gas-fired power plant (8% carbon dioxide, 0.12 MPa pressure) enters the membrane module's tube side, while lean liquor (35°C) contacts the shell side in counter-current flow. The composite membrane is suitable for low-pressure flue gas, achieving a single-stage capture rate of 85%.

[0076] Desorption unit: The rich liquid is heated to 95°C, and carbon dioxide is desorbed by steam purging, with a purity of 99.0%.

[0077] Resistant to NOx pollution (retention rate >90%).

[0078] Example 6

[0079] SAPO-34 zeolite membrane coupled piperazine (PZ) / diethanolamine (DEA) mixed solvent system

[0080] Membrane material: SAPO-34 zeolite membrane (pore size 0.38nm, carbon dioxide / nitrogen selectivity ≈150, specific surface area 2200m²) 2 / m 3 ).

[0081] Mixed amine system: 20wt% PZ + 15wt% DEA aqueous solution (PZ accelerates absorption, DEA enhances capacity).

[0082] Absorption Unit: Simulating flue gas from a coal-fired power plant (14% carbon dioxide, 5% O2), the membrane module's shell side flows, while the lean liquor (45℃) tube side engages in counter-current contact. The SAPO-34 membrane can efficiently separate carbon dioxide, achieving a carbon dioxide absorption rate of 0.42 kg / (m³). 2 ·h).

[0083] Desorption unit: The rich liquid is heated to 92°C, and carbon dioxide is desorbed by vacuuming on the membrane side. The regeneration energy consumption is 1.9 GJ / ton of carbon dioxide.

[0084] It is suitable for low-pressure flue gas, requires no multi-stage series connection, and has stable performance after 200 hours of continuous operation.

[0085] All cases demonstrate the core advantages of membrane-coupled mixed amine systems: high specific surface area to improve mass transfer efficiency, superhydrophobicity to avoid membrane wetting, and antifouling properties to adapt to complex flue gas.

[0086] Table 1 shows the key parameters and cycle performance of different embodiments.

[0087]

[0088] Table 1

[0089] The above embodiments are only used to illustrate the technical solution of this utility model, and are not intended to limit it.

Claims

1. A carbon dioxide capture system for a membrane-coupled mixed amine solution, characterized in that, include: The absorption unit employs a hollow fiber membrane module, allowing a carbon-containing gas source and an organic amine solution to convect from opposite sides of the membrane. A heat exchange unit is provided between the absorption unit and the desorption unit to raise the temperature of the amine-rich liquid with a high carbon dioxide load discharged from the absorption unit. The desorption unit employs a hollow fiber membrane module, allowing the heated amine-rich liquid to flow on one side of the membrane, while the desorbed carbon dioxide is discharged from the other side of the membrane. The hollow fiber membrane module uses one of the following membranes: superhydrophobic polyetheretherketone hollow fiber membrane, polytetrafluoroethylene hollow fiber membrane, Al2O3 ceramic membrane, ZIF-8 metal-organic framework membrane, GO / PI composite membrane, and SAPO-34 zeolite membrane; the surface area to volume ratio of the membrane in the hollow fiber membrane module is 1000~9000 m². 2 / m 3 .

2. The carbon dioxide capture system for membrane-coupled mixed amine solution according to claim 1, characterized in that, The side of the desorption unit that discharges carbon dioxide is purged with low-pressure steam, steam, or nitrogen.

3. The carbon dioxide capture system for membrane-coupled mixed amine solution according to claim 1, characterized in that, The side of the desorption unit that discharges carbon dioxide is set to a vacuum.

4. The carbon dioxide capture system for membrane-coupled mixed amine solution according to claim 1, characterized in that, The lean solution discharged from the desorption unit is input into the heat exchange unit for heat exchange with the rich amine solution.

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