Carbon capture using hydrophilic membranes in combination with cryogenic distillation

Abstract

The present disclosure provides systems and methods for producing liquid or supercritical CO2. The systems and methods can include a hydrophilic membrane separation module, a drying module, and a cryogenic separation module, wherein the distillate from the cryogenic separation module is used to regenerate the drying module (suck up water) and then recycled to the hydrophilic membrane separation module to recover residual CO2.

Description

Background Technology

[0001] Significantly mitigating the climate crisis and limiting global warming to 1.5°C requires a broader approach beyond electrification and renewable energy to deeply decarbonize industry. While power generation and transportation have begun transitioning to a carbon-neutral future, industrial decarbonization has yet to make meaningful progress. All pathways to achieving the 2050 carbon neutrality target require large-scale carbon capture, utilization, and storage (CCUS) in the industrial sector. A key aspect of such efforts is the development and deployment of efficient, scalable gas separation technologies capable of successfully addressing the dilution properties of CO2 emissions.

[0002] Current carbon capture solutions, such as amine and other solvent technologies, are used extensively in chemical plants, but they have failed to demonstrate their ability to consistently and cost-effectively meet capture requirements. These often fall short of promised capture rates and still face many unresolved issues (e.g., solvent degradation, ammonia emissions, high energy requirements, etc.). Summary of the Invention

[0003] This paper recognizes that synergistic combinations of separation modules can be used to generate liquid or supercritical CO2 from feed streams (e.g., flue gas streams). One such separation module is a hydrophilic membrane separation module that utilizes the advanced membrane technology described herein, which enables low-pressure and low-cost separation without the associated chemical emissions, regeneration requirements, or steam demands (e.g., as required for amine-based separations). These membranes are resistant to impurities present in the flue gas stream and separate CO2 from the humidified stream (i.e., the stream containing water vapor). This feature is convenient because flue gas streams typically contain at least some water, which is costly to remove. However, membranes acting alone cannot produce liquid CO2.

[0004] On the other hand, while cryogenic distillation modules can produce liquid and / or supercritical CO2 with high purity (i.e., greater than 98%), they cannot achieve high CO2 recovery rates from CO2 compositions commonly found in flue gas. Therefore, membrane modules can be used to concentrate CO2 in the flue gas before it is fed to the cryogenic distillation module, thereby achieving high recovery rates of liquid or supercritical CO2. Cryogenic distillation modules do require a small amount of water in their feed stream. However, a drying module can be placed between the membrane separation module and the cryogenic distillation module to produce liquid CO2 with high recovery rates from flue gas streams with relatively low CO2 concentrations.

[0005] Advantageously, the cryogenic distillation module also produces a distillate stream that is dry and contains a considerable amount of residual CO2 (e.g., greater than about 10%). This distillate can be synergistically first sent to a regeneration drying module (e.g., TSA) to carry some of the water required by the hydrophilic membrane, and then recycled to the membrane separation module (i.e., for recovering the residual CO2). Overall, the combination of modules described herein is uniquely and well-designed for producing liquid CO2 from flue gas streams with high recovery rates.

[0006] In one aspect, this paper provides a method for enriching CO2. The method may include: (a) separating a CO2-containing feed stream into a CO2-rich stream and a CO2-lean stream using a membrane separation module, wherein the membrane separation module comprises a hydrophilic membrane and the feed stream is humidified; (b) drying the CO2-rich stream using a drying module to produce a water stream and a dried CO2 stream; (c) separating the dried CO2 stream into a liquid or supercritical CO2 stream and a distillate stream using a cryogenic separation module; (d) recycling the distillate stream to the drying module, thereby merging the distillate stream with the water stream to produce a humidified distillate stream; and (e) recycling the humidified distillate stream to the membrane separation module.

[0007] In some implementations, the feed stream is flue gas.

[0008] In some implementations, the feed stream contains 4% to 30% CO2.

[0009] In some implementations, the feed stream has a pressure of about 1 bar.

[0010] In some implementations, the feed stream is compressed to 2 to 10 bar before being fed to the membrane separation module.

[0011] In some implementations, the membrane separation module has multiple hydrophilic membranes configured in at least two segments and / or at least two stages.

[0012] In some implementations, the hydrophilic membrane contains ionomers.

[0013] In some implementations, the hydrophilic membrane is fluorinated.

[0014] In some implementations, the hydrophilic membrane is a transport-enhancing membrane.

[0015] In some implementations, the hydrophilic membrane is a hollow fiber membrane, a plate-and-frame membrane, or a spiral wound membrane.

[0016] In some implementations, the hydrophilic membrane is humidified.

[0017] In some implementations, the drying module includes a temperature-switching adsorption (TSA) module.

[0018] In some implementations, the distillate stream is used to regenerate the TSA.

[0019] In some implementations, the heat used to regenerate the TSA is provided at least in part by compressing a CO2-rich stream.

[0020] In some implementations, the dried CO2 stream contains less than 100 ppm of water.

[0021] In some implementations, the cryogenic separation module includes a propylene refrigeration circuit.

[0022] In some implementations, the distillate stream is used to cool the dried CO2 stream before being recycled to the drying module.

[0023] In some implementations, the distillate stream contains 30% to 90% CO2.

[0024] In some implementations, the liquid or supercritical CO2 stream contains 98% to 99.9% CO2.

[0025] In some implementations, the humidified distillate stream is fed to a compressor upstream of the membrane separation module.

[0026] In some implementations, the humidified distillate stream is fed to a section or stage of the membrane separation module.

[0027] In some implementations, a portion of the humidified distillate stream is combined with a CO2-rich stream downstream of the membrane separation module.

[0028] In some implementations, a portion of the distillate stream is sent to the membrane separation module instead of first to the drying module.

[0029] In some embodiments, the method further includes feeding the dried CO2 stream to a deoxygenation module before feeding the dried CO2 stream to a cryogenic separation module.

[0030] In some embodiments, the method further includes deoxygenating a liquid or supercritical CO2 stream.

[0031] In another aspect, this paper provides a method for enriching CO2. The method includes: providing a feed stream containing at least about 60% CO2 on a dry basis, having a pressure of at least 30 bar, having less than about 500 ppm of water, and having a temperature below about 0°C; enriching CO2 from the feed stream at a low temperature to produce a bottom product containing at least 95% CO2 and a top product containing less than 40% CO2; expanding the top product to a pressure of less than about 5 bar; and enriching CO2 from the expanded top product using a membrane separation module and recycling the enriched CO2 back to the feed stream.

[0032] In some implementations, the feed stream comes from an oxy-combustion process.

[0033] In another aspect, this document provides a system configured to implement the method of any one of the preceding claims.

[0034] Other aspects and advantages of this disclosure will become apparent to those skilled in the art from the following detailed description, which shows and describes only exemplary embodiments of the disclosure. As will be appreciated, this disclosure is capable of other and different embodiments, and certain details thereof can be modified in a variety of obvious ways without departing from this disclosure. Therefore, the drawings and descriptions are to be considered illustrative in nature and not restrictive. Attached Figure Description

[0035] The novel features of the invention are particularly set forth in the appended claims. The features and advantages of the invention will be better understood with reference to the following detailed description and accompanying drawings (also referred to herein as “Figure” and “FIG.”), in which: Figure 1 An example of a system for enriching CO2 using a hydrophilic membrane and a cryogenic separation module, as described herein, is illustrated schematically.

[0036] Figure 2 An example of a system for enriching CO2 using a hydrophilic membrane and a cryogenic separation module, as described herein, is illustrated schematically, in which liquid or supercritical CO2 streams are deoxygenated.

[0037] Figure 3 An example of a system for enriching CO2 using a hydrophilic membrane and a cryogenic separation module, as described herein, is illustrated, wherein heat for regenerating the TSA is provided by compressing the CO2 stream.

[0038] Figure 4 An example of a cryogenic separation module applicable to the systems and methods described herein is illustrated schematically.

[0039] Figure 5 An example of a cryogenic separation and heat exchange module suitable for the systems and methods described herein is illustrated schematically.

[0040] Figure 6 An example of a membrane separation module as described herein is illustrated schematically.

[0041] Figure 7 An example of a single-stage membrane system for enriching CO2 from flue gas, as described herein, is illustrated schematically.

[0042] Figure 8 An example of a two-stage membrane system for enriching CO2 from flue gas, as described herein, is illustrated schematically.

[0043] Figure 9 An example of a three-stage membrane system for enriching CO2 from flue gas, as described herein, is illustrated schematically.

[0044] Figure 10 An example of a two-stage membrane system for enriching CO2 from flue gas, as described herein, is illustrated schematically.

[0045] Figure 11 An example of a two-stage, two-membrane system for enriching CO2 from flue gas, as described herein, is illustrated schematically.

[0046] Figure 12 An example of a three-stage, two-part membrane system for enriching CO2 from flue gas, as described herein, is illustrated schematically.

[0047] Figure 13 This illustration shows which system design described herein is typically preferred given a given feed CO2 concentration and desired CO2 product purity.

[0048] Figure 14 An example of a process for enriching CO2 from a stream with a high CO2 concentration is illustrated schematically.

[0049] Figure 15 An example of an existing method for enriching CO2 from flue gas is illustrated schematically.

[0050] Figure 16 Examples of the systems and methods described herein for enriching CO2 from flue gas are illustrated schematically.

[0051] Detailed description

[0052] The systems and methods described herein can be applied to post-combustion carbon capture from a variety of sources. Depending on the source of the flue gas, the stream typically comprises more than just a simple binary mixture of carbon dioxide (CO2) and nitrogen (N2). Different pretreatment and posttreatment processes are required depending on the specific existing technology used for capture (e.g., amines, pressure swing adsorption (PSA), or other membranes).

[0053] In contrast, the unique features of the membranes, systems, and methods of the present invention are CO2, O2, and SO2. x NO xH2 and H2S compounds (i.e., impurities) pass through the membrane at different rates without poisoning it. This allows for simplification of the rest of the supporting equipment for the surrounding system. This allows for easier integration of the system into brownfield plants and reduces capital costs and system complexity for greenfield applications.

[0054] When the term "at least," "greater than," or "greater than or equal to" precedes the first value in a series of two or more values, the term "at least," "greater than," or "greater than or equal to" can be applied to each value in the series. For example, greater than or equal to 1, 2, or 3 can be equivalent to greater than or equal to 1, greater than or equal to 2, or greater than or equal to 3.

[0055] When the terms "not exceeding," "less than," or "less than or equal to" precede the first value in a series of two or more values, the terms "not exceeding," "less than," or "less than or equal to" can be applied to each value in the series. For example, less than or equal to 3, 2, or 1 can be equivalent to less than or equal to 3, less than or equal to 2, or less than or equal to 1.

[0056] The terms "at least one of A and B" and "at least one of A or B" can be understood as A only, B only, or both A and B. The terms "A and / or B" can be understood as A only, B only, or both A and B.

[0057] As used herein, the term “about” generally refers to a quantity within twenty percent (20%) of the stated quantity.

[0058] Unless otherwise indicated, all percentages are expressed as mole fractions (i.e., mol%) when used in the context of concentration.

[0059] See Figure 1 The system and method described herein can enrich CO2 from flue gas 100. The flue gas can have any suitable CO2 concentration (e.g., 4%-30%), temperature (e.g., 40-80°C), and pressure (e.g., ambient pressure). The flue gas can be compressed in compressor 102 (e.g., compressed to 2-10 bar according to a suitable membrane feed pressure), cooled to the membrane operating temperature (optionally with water removal), and supplied to membrane separation module 104. The membrane module can be a multi-stage and / or multi-section design. The lean CO2 stream 106 can be used in energy recovery process 108 (e.g., a turbine to drive another compressor, such as one of the post-membrane compressor stages 110).

[0060] continue Figure 1The CO2-rich stream 112, having approximately 30-95% CO2, exits the membrane module at ambient pressure and near the membrane operating temperature. This stream can be compressed to a suitable pressure (e.g., about 30-60 bar) in one or more post-membrane compressors 110 (accompanied by intercooling and water removal if necessary) and supplied to a water removal module (e.g., a temperature swing adsorption (TSA) 114 dryer) to remove water to about 10 ppm to about 1,000 ppm of H2O. Oxygen can then be removed to about 10 ppm to about 1,000 ppm of O2 using (e.g., a catalytic) oxidation module 116.

[0061] The deoxygenated stream 118 can be fed to a cryogenic separation module, which includes a cryogenic unit 120, a heat exchanger 122, and a refrigeration circuit 124 (e.g., using propylene). Using the heat exchanger 122, the distillate 125 from the cryogenic unit can be used to cool the deoxygenated stream 118 (i.e., the feed stream to the cryogenic separation module). Further cooling can be provided via an external refrigeration circuit 124. The main outputs of the systems and methods described herein may include a liquid or supercritical CO2 stream 126 and a residual stream 128. In some cases, the liquid or supercritical CO2 stream passes through a pump or valve 130.

[0062] Refrigeration circuit 124 may contain propylene, as the boiling point of propylene is close to the desired cooling temperature (e.g., approximately -47°C). Cooling to a temperature that is cold but not too close to the triple point of CO2 is desirable (i.e., where freezing / deposition may become problematic). The refrigeration circuit may also contain ammonia, or the system may be autorefrigerated (i.e., all cooling is achieved by overpressurizing and expanding the feed). The distillate can be used to cool the feed through a series of expansions.

[0063] The cryogenic distillate 132 can be used to regenerate TSA 114, which is then reverse-circulated to membrane separation module 104 (directly or indirectly, as described below). TSA can be regenerated by connection to heat exchanger 134. In some cases, additional heat 136 is added to the heat exchanger. Regenerating TSA using cryogenic distillate is an advantageous feature of the systems and methods described herein because the distillate is very dry and needs to be humidified before separation in a hydrophilic membrane, while water needs to be removed from the CO2-rich stream before cryogenic separation. Regenerating TSA using cryogenic distillate 132 produces a humidified distillate stream 138.

[0064] The humidified distillate 138 can be expanded and depressurized to ambient pressure and fed upstream of the feed compressor 102 (solid line, at position 140). In some embodiments, the humidified distillate 132 can be expanded to the membrane's operating pressure and fed downstream of the feed compressor (dashed line, at position 142) or at some point in a multi-stage membrane process (at position 144). It can also (e.g., partially) be fed back downstream of the membrane (at position 146), for example, to maintain stable recovery and reduce the size of the membrane system.

[0065] Finally, in some cases, some or all of the distillate can bypass 148 TSA and be sent to the membrane module (at any of positions 140, 142, or 144).

[0066] See Figure 2 Elements with the same number correspond to Figure 1 The elements described herein, the system and method, can be used for O2 separation 116 at the end of the process (i.e., after cryogenic separation 120 and before or after optional pump or valve 130). Figure 2 One advantage of the described implementation scheme is that it is compatible with... Figure 1 Compared to the aforementioned implementation scheme, a smaller amount of logistics processing is required to remove O2.

[0067] See Figure 3 Elements with the same number correspond to Figure 1 The elements described herein, in the system and method, can be implemented for TSA 114 prior to cryogenic feed compression 110 (or at some intermediate stage during compression). Such an implementation allows for TSA regeneration at lower temperatures and allows for the use of waste heat 136 from compression to heat the humidified distillate 138.

[0068] Figure 4 The cryogenic separation module (i.e., Figure 1More detailed examples of units 120, 122, 124, 125 are provided. A pressurized (e.g., 30-60 bar) feed 400 may be conveyed through a cold box 402 and cooled (e.g., to -30°C to 0°C) before being supplied to a distillation unit 404 (e.g., a flash tank or column). N2-rich vapor 406 may be condensed 408 (e.g., at approximately -43°C) by a (propylene) refrigeration unit. The resulting liquid phase 410 may be refluxed back to the distillation unit 404, while the distillate 412 undergoes energy recovery before being recycled to process 414 (i.e., for TSA regeneration, and then sent to a membrane feed compressor). This energy recovery process may include using it as a cooling medium in the cold box (as shown), expanding via a valve to achieve a lower temperature, and / or expanding via a turbine expander connected to one of a plurality of compressors in the propylene refrigeration unit. CO2-rich liquid 416 (e.g., >90% CO2) from the distillation unit can be partially boiled 418 and used as a heat sink in the cold box. Once partially boiled, the vapor 420 is recycled back to the distillation unit, and the liquid 422 can be pumped 424 to a supercritical state 426 (i.e., for pipeline transport and / or geological storage). For better energy efficiency, the reboiled vapor can be partially condensed by the CO2-rich liquid (when it is boiled) or by some other heatable cold stream.

[0069] Figure 5 A more detailed example of a cryogenic and heat exchange module that can be used to obtain high-purity, low-pressure (e.g., 14-16 bar) liquid CO2 is shown, where elements with the same number correspond to... Figure 4 The elements in this process. In this example, the bottom product 422 is expanded 500 (e.g., using valve 502) to the desired pressure (and thus cooled and flashed). The vapor 504 of this stream can pass through a condenser 506 driven by a refrigeration unit, accompanied by a liquid return 510. It can also be simply recycled back to process 508 (i.e., simple flashing without a condenser or return). The liquid stream 512 from the flash tank will inherently meet single-phase and pressure specifications. The heating temperature of the CO2-rich liquid stream from the distillation unit can be used to control the temperature. If it is desired to subcool the liquid product stream, this can be driven by a refrigeration unit or done by recycling a stream to the process. For better energy integration, the bottom product stream can be subcooled before flashing (either via the CO2-rich stream from the distillation unit or via any reverse-circulation of the process stream).

[0070] The use of CO2 capture and sequestration in heavy industrial flue gas streams (e.g., from cement or steel production) or in food and beverage applications provides illustrative examples of several advantages of the systems and methods described herein. These flue gas streams typically contain low to moderate (16-24%) CO2 concentrations. These concentrations are generally too low for cryogenic distillation to achieve high recovery rates (greater than about 90%). Therefore, for example... Figure 1 The design shown will be used to achieve high recovery rates for liquid CO2 (where CO2 can be used in food and beverage applications) or supercritical CO2 (where CO2 is encapsulated). In such a design, the membrane module can include a two-stage design. The second membrane step and the recirculated distillate stream enable high to very high CO2 recovery rates (90% to greater than 95%).

[0071] Another illustrative example of the advantages of the systems and methods described herein is the capture, utilization, or sequestration of CO2 from small, decentralized flue gas streams, such as those from industrial and residential boilers. These streams typically contain low to moderately low (approximately 3% to approximately 13%) CO2 concentrations. These concentrations are often too low for cryogenic distillation to achieve high recovery rates (greater than approximately 90%). In this case, a two-stage membrane module is used prior to cryogenic distillation to achieve sufficient CO2 purity enhancement. In both cases, the membrane module is synergistically integrated with the cryogenic distillation module using optimal system design to overcome the limitations of both technologies and produce liquid or supercritical CO2 with high recovery rates.

[0072] hydrophilic membrane

[0073] The systems and methods described herein may use hydrophilic membranes. The membrane may be a thin-film composite membrane having more than one layer. This layer may include a selective layer, a support layer, and may include a channel layer and / or a protective layer. Suitable channel layers are described in PCT patent application serial number PCT / US2022 / 036284 or PCT patent application serial number PCT / US2016 / 031135, each of which is incorporated herein by reference. The protective layer material is similar to the channel layer material.

[0074] In some cases, hydrophilic membranes are transport-enhancing membranes. The membrane can be bound to a carrier agent that increases the solubility of certain components in a gaseous feed stream (e.g., CO2) through a reversible reaction or complexation mechanism, thereby preferentially "facilitating" their transport through the membrane. The carrier agent can be covalently or electrostatically bound within the membrane to prevent its migration or loss from the membrane during use. Hydrophilic membranes made of polymeric materials that are ionomers are very useful in the separations described herein. In some embodiments, a carrier agent, such as an amine group, for selectively and reversibly reacting with CO2 can be bound within the ionomer.

[0075] Ionomers can be fluorinated or hydrocarbon-based. Ionomers can be used as selective layers in thin-film composites. As used herein, an ionomer is a copolymer containing covalently bonded ionic side groups, such as sulfonic acids, sulfonates, carboxylic acids, carboxylates, phosphates, phosphonium, or ammonium. As used herein, the ionomer equivalent weight is the weight of an ionomer containing one mole of sulfonate groups. The ionomer equivalent weight (EW) can be less than 5000 g / mol, less than 2000 g / mol, or from 500 g / mol to 800 g / mol.

[0076] Ionomers of copolymers containing sulfonic acid or sulfonate groups can be used to prepare selective layers. Suitable ionomers and films include those described in U.S. Patent Nos. 5,191,151; 10,639,591; and 10,029,248, each of which is incorporated herein by reference. Suitable ionomers may comprise repeating units A and B, wherein A is a polymeric derivative of a fluorinated monomer, and B comprises sulfonate groups. Ionomers may contain 50% or more of carbon-fluorine groups, relative to a carbon-fluorine group plus a carbon-hydrogen group. Some ionomers are perfluoropolymers, wherein there are no carbon-hydrogen groups in the repeating units of the polymer backbone. Examples of the latter include copolymers comprising repeating units of tetrafluoroethylene and perfluorovinyl ether monomers having side sulfonate groups, such as, for example, Nafion® (Chemours, Wilmington Del.) and Aquivion® (Solvay, Houston Tex.).

[0077] The selective layer may also comprise a polyphenylene ionomer, as described in PCT patent application serial number PCT / US2024 / 042529, filed August 27, 2024, entitled “Thin-film composite membranes incorporating a polyphenylene ionomer and separation process therewith,” which is incorporated herein by reference in its entirety.

[0078] The selectivity layer thickness has a significant impact on membrane cost and the productivity of the separation process per unit area. The selectivity layer can be thin (0.01 μm to 5 μm). The selectivity layer thickness can be optimized to achieve both high CO2 permeability and high CO2 selectivity relative to other gases through the thin-film composite membrane.

[0079] The porous layer support can be in the form of a flat sheet, hollow fiber, or tube. The porous layer support reinforces the thin selective layer and facilitates further mechanical reinforcement of the overall thin-film composite membrane, allowing the membrane to be fabricated into more complex geometries, such as spiral-wound or hollow fiber membrane modules. In the case of a flat sheet, the porous layer support can also incorporate an even stronger backing material, such as porous nonwoven polyester or polypropylene. Suitable porous layer support materials include, but are not limited to, polyvinylidene fluoride, expanded polytetrafluoroethylene, polyacrylonitrile, polysulfone, polyetheretherketone (PEEK), and polyethersulfone. Porous inorganic substrates (e.g., porous silica or porous alumina) are also suitable support materials. The permeating gas should flow relatively unimpeded through the typically much thicker porous layer support, which has a porosity of 40% or higher. The average pore size of the porous layer support can be less than 0.1 μm, or from 0.01 μm to 0.03 μm.

[0080] In thin-film composite membranes, the selective layer and the porous layer support are coplanar and in direct contact. The selective layer can also be primarily layered. "Primarily layered" means that at least 50% or more of the material in at least one of the two or more different layers does not penetrate the pores of the other layer.

[0081] The selective layer in a thin-film composite membrane can undergo a heat treatment step called "annealing" to further improve mechanical durability, long-term separation permeability and selectivity, and resistance to degradation caused by contact with liquid water. The ionomers in the selective layer can be annealed by heating the thin-film composite membrane (e.g., in some cases, to near or above the glass transition temperature of the ionomers). The exact glass transition temperature will depend on the ionomer composition and the associated counterions. Typically, annealing temperatures range from 50°C to 200°C.

[0082] Thin-film composite membranes are highly useful for separating CO2 from flue gas. The feed side of the membrane can be exposed to a flowing gaseous composition containing CO2. A driving force can be provided where the partial pressure of CO2 on the feed side is higher than that on the permeate side. Separation of CO2 from the gaseous composition occurs through the membrane, producing a composition with a higher concentration of CO2 on the permeate side than on the feed side. Separation can also be enhanced by including water vapor in the composition and / or by using a purge gas on the permeate side, the purge gas acting to reduce the partial pressure of CO2 in the permeate. For example, the purge gas can contain an inert gas, such as water vapor or nitrogen.

[0083] Membrane module

[0084] The systems and methods described herein can use hollow fiber membranes and / or spiral wound flat sheet membranes.

[0085] Reference Figure 6 A practical module can be formed from a composite hydrophilic membrane. Here, flue gas 600 containing CO2 and N2 can flow along the membrane, with CO2 selectively permeating through the membrane to produce (CO2-rich) permeate 604 and (N2-rich) residue 602. This paper provides materials and methods for forming the membrane separation module.

[0086] A selective film coating can be applied to a hollow fiber substrate by immersing the hollow fibers in a selective film coating solution and removing them at a specified constant rate. The polymer layer is allowed to dry, and additional layers can be applied using the same method. If desired, the coated fibers can undergo an annealing process at a temperature above ambient temperature. The selective coating can be applied to the interior or exterior of the hollow fiber substrate.

[0087] Small hollow fiber modules can contain straight fibers within a plastic or stainless steel shell. These micro-modules can contain any suitablely large number of fibers. The fill factor of micro-modules is typically low (e.g., < 20% v / v), which can allow for gas or liquid bypass if a shell feed is used. Methods exist for reducing bypass flow in shell-side feeds. One option is to combine a mandrel and a winding that guides fluid flow on the shell side of the module. Another option is to make the fiber bundles more compact and fill the extra space around the bundles with epoxy resin. Using more expensive components can make the fiber-containing tube smaller than the epoxy-containing tube.

[0088] The manufacturing process for straight fiber micromodules involves inserting fibers into a housing without damaging the external coating. There are several ways to do this, including: (a) placing a semi-rigid rod through the housing, tying the fibers to the rod, and pulling them through the housing; (b) if the fibers themselves are rigid enough, they can be pushed through the housing; or (c) an injection-molded housing divided into two halves allows the fibers to be placed into the housing before the two halves are glued together.

[0089] Once the fibers are inside the housing, epoxy resin can be injected into the end of the housing to fill the space between the fibers and the housing (i.e., creating a separation between the lumen side of the fibers and the shell side). Several options exist for this module potting operation, including: (a) (e.g., for smaller modules) directly injecting viscous epoxy resin into the end of the module; (b) (e.g., for medium-sized modules) adding a section of silicone tubing to the end of the housing and filling it with epoxy resin along with a portion of the housing; (c) (e.g., for larger modules) attaching silicone tubing to the end but sealing the fiber end to prevent epoxy resin from entering the lumen. An epoxy resin-containing syringe can be attached to the silicone tubing, forcing the epoxy resin to bulge upwards and around the fibers and into the housing. Slits can be cut in the silicone tubing to allow epoxy resin to be injected into voids (if voids are formed). Typically, this method is used to pot one end of the module at a time.

[0090] Once the epoxy has cured (which can take up to 18 hours), depending on the type of epoxy, excess epoxy can be removed, and the fiber cavities can be opened. This can be achieved by cutting the epoxy and fibers with a sharp blade. The process needs to be performed in a way that produces fully open fibers.

[0091] The following description pertains to the fabrication of large hollow fiber modules. This involves continuous hollow fiber coating, bundle winding, and tube filling.

[0092] Many factors need to be considered during hollow fiber coating. To produce a continuous coating, methods must be developed to remove and prevent dust deposition on the fibers; static electricity must be eliminated; temperature and humidity in the coating chamber must be controlled; and large fiber pores must be bridged by using a channel layer coating or adding a temporary pore filler (e.g., water). Coating thickness is controlled by polymer solution concentration, solvent system, coating solution viscosity, and coating speed. To prevent damage to the coating, drying temperature and drying dwell time need to be optimized, and systems for maintaining minimum fiber tension need to be developed. As the process scales up, multiple fiber management and solvent recovery methods are required.

[0093] Several factors can be optimized when winding fibers, including: the number of fibers in the winding tape; fiber tension; winding angle; the number of fiber crosses in the layers; the spacing between fibers; and the spacing between fiber strips. Permeating and humidifying fibers can be wound together to create modules that combine in-situ humidification. Multiple winding elements can be added inside the fiber bundle to improve residence time and contact with the fibers. Multiple winding elements can also reduce gas flow detours. Further expansion of winding involves multi-spindle winding and automated bundle cutting.

[0094] This article provides a potting method. The resin-to-curing agent ratio can be adjusted to reduce viscosity and delay curing and heat release, allowing the epoxy resin to penetrate into larger fiber bundles.

[0095] The curing schedule can be adjusted to control exothermic processes and epoxy resin penetration. For potting large modules, the potting mold can be initially heated to 35°C. As the epoxy resin fills the mold, its viscosity decreases. This improves the penetration of the epoxy resin into the fiber bundles. The mold can then be allowed to cool back to 30°C, which slows down the reaction rate of the two-component epoxy resin. Slowing down the reaction allows more time for epoxy resin penetration. When the epoxy resin hardens (e.g., after several hours), the final two curing stages can be performed to achieve maximum chemical resistance.

[0096] Adjusting the filling procedure can reduce air bubble formation in the epoxy resin. This is the reverse of the process of removing air bubbles from the epoxy resin. The ends of the fibers can be sealed with five minutes of epoxy resin. Furthermore, the space between the stopper and the fibers can be sealed. This effectively prevents the formation of large air bubbles during the filling process. Typically, filling is done from only one location to prevent trapped air bubbles.

[0097] Several methods for sealing fiber ends to prevent epoxy resin from filling the lumen can include heat sealing, ring forming, or fast-curing / high-viscosity epoxy sealing. In heat sealing, a hot knife is used to cut the wound bundle to a precise length. This not only performs the cutting operation but also melts and closes the fibers. This prevents epoxy resin from filling the lumen during the potting process.

[0098] The ring-forming method is another way to prevent epoxy resin from entering the lumen during potting. Here, the fiber bundle is not cut. If the bundle is wound to a precise length and no cutting is required, the fiber lumen remains closed. The ring ultimately has a significantly larger outer diameter than the bundle itself.

[0099] When coating an active layer onto the lumen side of a substrate, several factors can be optimized, including: straight fiber module design; polymer concentration; solvent system; solution viscosity; solution injection method; solution removal method; pore filling; and drying method. For lumen coating, a cylinder is typically fabricated from a hollow fiber substrate before the coating process.

[0100] Several options exist for minimizing pressure drop on both the feed and permeation sides of the module. The module can be designed to be "short and fat" (e.g., for permeation-side (lumen) pressure drop control). Fibers can be arranged in a weaving pattern to reduce feed-side pressure drop and optimize water vapor injection. CFD (Computational Fluid Dynamics) analysis can be used to improve module design to optimize mass transfer within the module.

[0101] Membrane separation module

[0102] The membranes described herein can be used to form membrane separation modules. These modules may have one or more membrane cartridges arranged in multiple segments and / or stages.

[0103] Figure 7 A schematic representation of a single membrane stage (and incidentally, a single segment) is shown. In a schematic diagram of membranes such as these, membrane 700 is shown as a diagonal dividing line within housing 702. The membrane receives a feed stream 704, which is separated into a permeate stream 706 (containing molecules that do not pass through the membrane) and a permeate stream 708 (containing molecules that pass through the membrane). The permeate stream is CO2-rich, while the permeate stream is CO2-poor (i.e., because the CO2 contained in the feed stream selectively permeates through the membrane). The feed stream can be compressed in compressor 710. In some cases, a portion of the permeate can be recycled 712 and / or a portion of the permeate can be recycled 714.

[0104] From an operational point of view, the primary system is the simplest. CO2 purity and recovery are functions of several factors, including membrane selectivity, operating pressure, and temperature. For high recovery systems (e.g., greater than 90%), concentration increases of 8–30% can be achieved. Such systems can be used in some CO2 utilization scenarios or as a general separation step prior to another process. Recycling a portion of the permeate stream can achieve higher purity, and recycling a portion of the residual stream can achieve higher recovery.

[0105] Figure 8 A schematic representation of a two-stage membrane separation module is shown. The membrane enriching the permeate stream is called a stage. Additional stages often contribute to achieving higher CO2 purity. In some cases, high purity can be achieved with fewer stages, but this may require a large recirculation rate. Adding additional stages can be cost and / or energy-efficient because they reduce the size of the recirculation flow.

[0106] like Figure 8 As shown, the permeate 800 from the first stage 802 becomes the feed for the second stage 804. The final CO2 product 806 is more concentrated than without the second stage. Here, the permeate 808 from the second stage can be recycled and added to the feed to the first stage 810.

[0107] This configuration is typically cost-effective for moderate (20-25%) initial CO2 concentrations with high purity and recovery requirements (e.g., approximately 90%). It is also effective for moderately low initial CO2 concentrations (e.g., 12-16%) with high recovery requirements but low purity requirements (e.g., approximately 60%). The second stage enables the system to achieve higher CO2 concentrations than selectively driven single-stage systems, and the recycling of second-stage permeate allows for high recovery rates.

[0108] Figure 9 A schematic representation of a three-stage membrane separation module is shown. Here, the permeate 900 from the second stage 902 becomes the feed stream for the third stage 904. The final CO2 product 906 is more concentrated (i.e., compared to the permeate from the first stage 908 or the second stage 902). Here, the residue 910 from the third stage can be recycled and added to the feed to the second and / or first stages.

[0109] This configuration is typically cost-effective for low to moderately low (e.g., 4-12%) initial CO2 concentrations with high to very high purity and recovery requirements (e.g., 90-95% or higher). Additional stages enable significant CO2 concentration increases and allow for high recovery rates in their residue recycling. For large concentration increases, this system may become more cost / energy efficient than a two-stage, two-part system (described below) because the latter's recycling rate can be progressively increased.

[0110] The membrane that enriches the permeate stream is called a step. Additional steps typically achieve higher CO2 recovery rates by recovering more CO2 from the stream that would otherwise be discharged and recycling it back into the process. Figure 10 A schematic representation of a two-stage membrane separation module is shown. Here, the permeate 1000 from the first stage 1002 becomes the feed stream for the second stage 1004. The permeate 1006 from the second stage can be recycled back to the feed to the first stage. When using a two-stage system instead of a single-stage system, more CO2 is recovered from the flue gas 1008 (i.e., the exhaust gas 1010 is less CO2-efficient).

[0111] This system is generally preferred for high (e.g., greater than 30%) initial CO2 purity requirements with medium (e.g., about 60%) to high (e.g., about 90%) purity and recovery rate requirements. It can also be used for medium (e.g., 20-24%) initial purity with low to medium purity and recovery rate requirements. Because it has only one stage, it is not preferred for large concentration increases. Its second stage allows it to achieve higher recovery rates than a single-stage system.

[0112] The number of segments and levels can vary. Figure 11 A schematic representation of a two-stage, two-section membrane separation module is shown. Here, permeate 1100 from the second stage 1102 can be returned to the first stage / section 1104 (and / or the second stage 1106). Residue 1108 from the second stage 1106 can be returned to the first stage / section 1104 (and / or the second stage 1102).

[0113] This system is typically cost-optimal for low to medium starting CO2 concentrations (e.g., 12-16%) with high purity and recovery requirements (e.g., 90%) and for medium starting CO2 concentrations with very high purity and recovery requirements (e.g., greater than 95%). Additional stages enable the system to achieve even higher purity, and a second stage allows for even higher recovery rates. Recycling the feed stream to a membrane outside the feed stage is generally not cost- or energy-optimal, but it can prove useful.

[0114] Figure 12 A schematic representation of a three-stage, two-part membrane separation module is shown. This design is similar to... Figure 11 The design incorporates a third stage (1200). This design can be used for low (e.g., 4-8%) initial CO2 concentrations and very high (e.g., greater than 95%) purity and recovery requirements. The additional stage enables a large concentration increase with a low recycling rate. The additional stage enables high CO2 recovery rates. It also helps reduce the stage cut required for the third stage.

[0115] Each design (i.e., such as) Figures 8-12 (As shown) also includes the option of incorporating a permeate vacuum. Similar to feed compression, a permeate vacuum increases the pressure differential across the membrane. However, this typically requires less energy because the permeate stream is smaller than the feed stream. Due to various trade-offs, incorporating a permeate vacuum on some or all membranes may be cost- and / or energy-efficient. Vacuum pressures can be approximately 0.3 psi, 0.5 psi, 1 psi, 2 psi, 3 psi, 4 psi, 5 psi, 6 psi, 8 psi, or 10 psia per square inch absolute.

[0116] Figure 13 An example graph showing the range of CO2 concentrations in the feed (horizontal axis) and the desired CO2 purity (vertical axis) is provided, with multiple zones where stage 1, 2, or 3 designs are typically preferred. Overall, these multiple designs allow for cost-effective carbon capture with recoveries greater than 90% and purity of 20%–95% for flue gas streams initially containing approximately 4% to 30% or higher CO2.

[0117] The capture, utilization, or sequestration of CO2 from heavy industrial flue gas (e.g., flue gas from cement or steel production) provides illustrative examples of several advantages of the methods described herein. These flue gas streams typically contain low to moderate (16-24%) CO2 concentrations and a certain amount of impurities. In many cases (i.e., utilization and sequestration), existing technologies would generally require significant pretreatment as described above. Where downstream processes require impurity treatment (i.e., some utilization and sequestration technologies), the methods described herein enable a less capital- and energy-intensive treatment step because smaller post-separation streams can be processed due to the membrane's tolerance to impurities. Where downstream processes do not require impurity treatment (i.e., some utilization technologies), the methods described herein completely eliminate the treatment step. Furthermore, where downstream technologies benefit from or require some or all of the present impurities (i.e., some bio-CO2 utilization technologies), this method both eliminates the treatment step and provides benefits to downstream processes. These flue gas streams will typically contain a certain level of VOCs and CO. In cases where downstream processes are intolerant to one or two of these substances, this method can eliminate treatment steps due to the membrane's highly efficient retention of these substances. When downstream processes require high-purity (greater than about 95%) CO2 and expect high CO2 recovery rates (greater than about 95%), a three-stage design can provide cost-optimal separation of the flue gas stream. When only moderate-purity (about 60% or lower) CO2 and moderately high to high recovery rates (about 90% to about 95%) are desired, a two-stage system can provide cost-optimal separation. Furthermore, in some cases, the systems and methods described herein offer significant advantages over existing techniques that would otherwise only deliver CO2 (i.e., amine absorption and cryogenic separation). The use of the systems and methods described herein avoids over-design for CO2 purity and saves capital and operating costs.

[0118] Another illustrative example of the advantages of the methods described herein over existing technologies is the CO2 capture and utilization or sequestration of small-scale distributed flue gas streams, such as those from industrial and residential boilers. These streams typically contain low to moderately low (approximately 3% to approximately 13%) CO2 concentrations and low CO2 flow rates (approximately 1,000 tonnes to 100,000 tonnes of CO2 / year) and a certain level of impurities. Such cases can offer the same advantages as the simplified or depleted treatment processes described above. Furthermore, many existing technologies require custom designs to meet a wide range of system sizes. In contrast, the systems and methods described herein can use multiple identical membrane products regardless of system size, and thus enable lower capital costs at these smaller scales.

[0119] Oxygen-enriched combustion

[0120] In some cases, the process described herein utilizes the fact that the oxygen-enriched combustion purge stream is under pressure. Since the hydrophilic membrane described herein can operate at low pressure, pressure expansion can be used to further cool the inlet leading to the column (i.e., to provide energy efficiency). Surprisingly, the membrane is used as a recovery step rather than a largely separation step.

[0121] In one aspect, this paper provides a method for enriching CO2. The method includes providing a feed stream containing at least about 55% CO2 on a dry basis, having a pressure of at least 30 bar, having less than about 500 ppm of water, and having a temperature below about 0°C. The feed stream may have a CO2 concentration (on a dry basis) greater than about 55%, greater than about 60%, greater than about 65%, greater than about 70%, greater than about 75%, greater than about 80%, greater than about 85%, or greater than about 90%. The feed stream may have a pressure of at least 30 bar, at least 35 bar, at least 40 bar, at least 45 bar, or at least 50 bar. The feed stream may have less than about 500 ppm of water, less than about 400 ppm of water, less than about 300 ppm of water, less than about 200 ppm of water, less than about 100 ppm of water, less than about 50 ppm of water, less than about 30 ppm of water, less than about 20 ppm of water, less than about 10 ppm of water, or less than about 5 ppm of water. The feed stream may have a temperature below about 0°C, below about -5°C, below about -10°C, below about -15°C, below about -20°C, below about -25°C, or below about -30°C.

[0122] The method may further include cryogenic enrichment of CO2 from the feed stream to produce a bottom product containing at least 95% CO2 and a top product containing less than 40% CO2. The bottom product may contain at least 95% CO2, at least 97% CO2, at least 99% CO2, at least 99.5% CO2, at least 99.75% CO2, at least 99.9% CO2, or at least 99.95% CO2. The top product may contain less than 40% CO2, less than 35% CO2, less than 30% CO2, less than 20% CO2, or less than 15% CO2.

[0123] The method may further include expanding the top product to a pressure of less than about 5 bar, less than about 4 bar, less than about 3 bar, or less than about 2 bar, and using a membrane separation module to enrich CO2 from the expanded top product and recycle the enriched CO2 to the feed stream.

[0124] In some implementations, the feed stream originates from an oxygen-enriched combustion process.

[0125] Figure 14The system shown can be used to enrich CO2 from a stream with a high CO2 concentration. In some cases, the stream is generated by an oxy-fuel combustion process. Stream 1400 can be cooled 1402 (with water knock-out) to approximately 40°C to 60°C. The cooled stream 1404 can be compressed 1406 (with additional water knock-out) to approximately 30-50 bar. Then, additional water is removed from the stream 1408, for example, using variable-temperature drying to produce a high-pressure stream 1410, where the water is at parts per million (ppm) levels. The stream can be pre-cooled in heat exchanger 1412 before being fed to a cryogenic separation tower 1414. Pre-cooling can reduce the temperature to approximately 0°C to -30°C. The bottom product 1416 is primarily CO2.

[0126] To facilitate vaporization and reboiling at the bottom of the column, (e.g., ambient) air or a dry, high-pressure stream 1410 can be used for heating and energy recovery. To facilitate condensation and provide reflux at the top of the column, a refrigeration system can be used. The top stream 1418 can still contain a significant amount of CO2 (e.g., up to 30%-40%) and can expand 1420 to the operating pressure of the membrane 1422 (e.g., 2-4 bar) for further cooling. The expanded stream 1424 can be used for cooling in the heat exchanger 1412 to reduce the load on the refrigeration system. The hydrophilic membrane 1422 can use the input stream 1426 without further pressurization or treatment. The permeate 1428 will have a low CO2 level and can be discharged. The permeate 1430 has an increased CO2 concentration (on a dry basis, similar to the concentration of the input 1400) and will be at atmospheric pressure. It is recycled to the compression step 1406.

[0127] Advantages of the process regarding impurities

[0128] This paper recognizes that advanced membrane technologies hold the key to managing CO2 emissions on both large and small scales through modular, low-pressure, and low-cost separation without additional chemical emissions, regeneration requirements, or steam demands. The membrane technologies described herein can unlock practical, near-term feasible CCUS for CO2 emitters. The systems and methods described herein have demonstrated high performance, small footprint, resistance to poisons, and the ability to operate at low pressures, making them particularly suitable for point-source post-combustion carbon capture applications in several sectors, such as steel, cement, chemicals, and blue hydrogen.

[0129] Surprisingly, compared to existing methods, the system and method described herein can utilize CO2 emission streams (e.g., various post-combustion flue gases) and require relatively little pretreatment of the stream prior to membrane separation. For example, O2 and SO2, which are frequently present in flue gases... x NO xH2, H2S, CO, volatile organic compounds (VOCs), and even H2O (collectively referred to as "impurities") are substances that other methods require to remove before CO2 separation, but the membranes described herein are resistant to these substances. Therefore, using the systems and methods described herein, these impurities can instead be removed from the enriched CO2 stream. The enriched CO2 stream typically has a much lower total volumetric flow rate than flue gas (i.e., due to the separation of CO2 and N2). This reduction in volume synergistically reduces size and thus the capital and operating costs of units removing multiple impurities. Furthermore, the membrane effectively retains CO and VOCs. Therefore, the membrane is capable of completely removing these substances from any pretreatment or posttreatment process.

[0130] In one aspect, this paper provides a method for enriching CO2. The method may include providing a feed stream containing CO2 and impurities, wherein the impurities are O2, SO2, etc. x NO x H2, CO, VOC, H2S or any combination thereof; contacting the feed stream with the membrane to generate a permeate stream and a residual stream, wherein the permeate stream contains CO2 and impurities; and treating the permeate stream to remove impurities.

[0131] In another aspect, this paper provides a system for enriching CO2. The system may include: (a) a membrane separation module comprising a membrane, wherein the membrane separation module is configured to receive a feed stream and generate a permeate stream and a residual stream, wherein the feed stream contains CO2 and impurities, wherein the impurities are O2, SO2, etc. x NO x (a) H2, CO, VOC, H2S or any combination thereof, wherein the permeate stream contains CO2 and impurities; and (b) a processing module configured to process the permeate stream to remove impurities.

[0132] The systems and methods described herein can be used for post-combustion carbon capture from a variety of sources. Depending on the source of the flue gas, the stream typically contains more than just a simple binary mixture of carbon dioxide (CO2) and nitrogen (N2). Different pretreatment and posttreatment processes are required depending on the specific existing technology used for capture (e.g., amines, pressure swing adsorption (PSA), or other membranes).

[0133] In comparison, the membranes, systems, and methods of the present invention are unique in that they contain CO2, O2, and SO2. x NO x H2, CO, VOCs, and H2S compounds (i.e., impurities) pass through the membrane at varying rates without poisoning it. This allows for simplification of the remaining equipment in the surrounding system. It also allows for easier integration of the system into brownfield plants and reduces capital costs and system complexity for greenfield applications.

[0134] In comparison, Figure 15 A general process flow diagram is shown regarding competing and existing technologies (such as amines, PSA, and other membranes). Here, flue gas 1500 can enter a water wash 1502 (e.g., to cool the stream and / or remove particulate matter). A blower 1504 can increase pressure or move the stream through the process. Particulate matter 1506 can be removed from the stream using a wet or dry electrostatic precipitator (ESP) or a fabric filter baghouse. A carbon bed 1508 can remove various chemical impurities, such as organic molecules. One or more of (wet) flue gas desulfurization (FGD), spray dryer absorber (SDA), circulating dry scrubber (CDS), and dry adsorbent injection (DSI) and / or a lime scrubber (which can be specifically used for SO2) can be used. x Removal) to achieve the removal of acidic gases (e.g., SO2). x 1510 can be removed by HCl and HF. 1512 can be removed by one or more of catalytic oxidation, chemisorption (e.g., on copper), or other suitable methods. Low NO₂ levels can be used at the source by employing selective catalytic reduction (SCR) or non-catalytic reduction (NCR). x Combustion technology to achieve NO x Remove 1514. The stream can be dehydrated 1516 and the liquid removed via direct contact cooling or other cooling methods. Finally, the stream can be compressed 1518 (e.g., up to about 16 bar) to provide treated flue gas 1520, which is adapted to be separated 1522 (e.g., using amines, PSA, other existing membrane technologies) into an air-rich stream 1524 and a CO2-rich stream 1526. The air-rich stream 1524 can be post-treated 1528 and / or released to the atmosphere. The CO2-rich stream 1526 can be post-treated 1530 and subsequently either compressed 1532 for sequestration 1534 or utilized 1536 to produce product 1538. Note that the exact order of the pretreatment steps can vary and can be derived from... Figure 15 Remove or add one or more steps from the flowchart shown. In particular, amine systems typically also require (i) a tray tower employing a scrubbing liquid with added caustic soda to capture residual SO2 and particulate fly ash, (ii) a suite of booster fans to provide a pressure drop to draw flue gas from the main duct, drive the flue gas through a complete side-flow pilot unit, and return the flue gas to the main flue gas chimney, and (iii) a packed tower subcooler to reduce the flue gas temperature and condense water vapor from the flue gas.

[0135] Overall, the common limitation is that each pretreatment step increases capital costs, operating expenses, and introduces operator complexity. This is particularly true for operations involving large-volume N2 streams prior to the CO2 separation step 1522. In contrast, the system and method described herein enable low-cost carbon capture, for example, by reducing the amount of other equipment.

[0136] In contrast, this paper provides a method for enriching CO2. The method includes providing a feed stream containing CO2 and impurities, wherein the impurities are O2, SO2, etc. x NO x The feed stream may contain H2, CO, VOCs, H2S, or any combination thereof. The method may further include contacting the feed stream with the membrane to generate a permeate stream and a residual stream, wherein the permeate stream contains CO2 and impurities. The method may also include treating the permeate stream to remove impurities.

[0137] In another aspect, this document provides a system for enriching CO2. The system may include a membrane separation module comprising a membrane, wherein the membrane separation module is configured to receive a feed stream and generate a permeate stream and a residual stream, wherein the feed stream contains CO2 and impurities, wherein the impurities are O2, SO2, etc. x NO x The permeate stream contains H2, CO, VOC, H2S, or any combination thereof, and the permeate stream contains CO2 and impurities. The system may also include a processing module configured to process the permeate stream to remove impurities. In some cases, the system further includes a humidification module configured to humidify the membrane.

[0138] like Figure 16 As can be seen, the systems and methods described herein require fewer overall processing steps, especially fewer steps prior to using membranes to separate CO2. The membranes described herein operate at low pressures, for example, below about 10 bar, below about 8 bar, below about 6 bar, below about 4 bar, or below about 2 bar. They can operate at elevated temperatures, for example, from about 50°C to about 100°C, at least about 40°C, at least about 50°C, at least about 60°C, at least about 70°C, at least about 80°C, at least about 90°C, or at least about 100°C. The membranes described herein can operate at high relative humidity (e.g., water vapor-saturated flue gas).

[0139] The membranes described in this article typically do not require protection against O2 and SO2. x NO x Pretreatment is performed on H2, CO, VOCs, or H2S. This allows for the removal of H2S from the system disclosed herein. Figure 15 Any or all preprocessing shown. Here, because of O2, SO... x NO xH2, CO, VOCs, and H2S move through the membrane, so post-treatment can be applied to smaller, more concentrated streams with lower capital and operating costs. Furthermore, because CO and VOCs are effectively retained by the membrane, the burden of post-treatment on these substances can be reduced, even if post-treatment is not completely eliminated.

[0140] focus on Figure 16 In the example system of this disclosure shown, flue gas 1600 may be fed to a water scrubber and / or lime scrubber 1602, and then to a compressor 1604 to produce a compressed feed 1606 (e.g., compressed to a low pressure, such as 4 bar), which is then sent to a membrane separation module 1608. The compressed feed 1606 may be separated into a lean CO2 stream 1610 and a rich CO2 stream 1612. The lean CO2 stream 1610 may be post-treated 1614 and / or released to the atmosphere. The rich CO2 stream 1612 may be post-treated 1616 and then either compressed 1618 for sequestration 1620 or utilized 1622 to produce product 1624.

[0141] The systems and methods disclosed herein offer numerous advantages, including reducing the cost of the remaining equipment by 20% or more. When combined with technologies that utilize CO2, including but not limited to bio-CO2 conversion into chemicals, this system provides additional value because some post-processing uses O2. This means that post-processing of the CO2 stream can also be removed. Compared to existing technologies such as amine systems and cryogenic systems, membranes can produce CO2 streams of target concentrations. This reduces energy requirements and system CAPEX by up to at least 35%.

[0142] In some embodiments, the permeate stream is released into the atmosphere. In some embodiments, the membrane is operated for at least one year. In some embodiments, the membrane produces at least about 10,000 tons of permeate stream within one year. In some embodiments, the feed stream contains about 4 mol% to about 50 mol% CO2. In some embodiments, the feed stream contains about 0 mol% to about 15 mol% O2.

[0143] In some implementations, the feed stream contains less than about 1,000 ppm SO₂ x In some implementations, the feed stream contains less than about 1,000 ppm of NO. x In some embodiments, the feed stream contains about 0 mol% to about 5 mol% of H2. In some embodiments, the feed stream contains less than about 1,000 ppm of H2S.

[0144] In some implementations, the feed stream contains O2 and SO2. x NO xThe feed stream contains at least two of the following: O2, H2, CO, VOC, and H2S. In some embodiments, the feed stream contains O2 and SO2. x NO x The feed stream contains at least three of the following: O2, H2, CO, VOC, and H2S. In some embodiments, the feed stream contains O2 and SO2. x NO x The feed stream contains at least four of the following: O2, H2, CO, VOC, and H2S. In some embodiments, the feed stream contains O2 and SO2. x NO x At least five of the following: O2, H2, CO, VOC, and H2S. In some implementations, the feed stream contains O2, SO2, and H2S. x NO x At least six of the following: O2, H2, CO, VOC, and H2S. In some embodiments, the feed stream contains O2, SO2, and H2S. x NO x All seven of them: H2, CO, VOC, and H2S.

[0145] In some embodiments, the feed stream is flue gas produced by combustion. In some embodiments, the feed stream also contains N2. In some embodiments, the feed stream contains about 0 mol% to about 20 mol% H2O. In some embodiments, the feed stream is saturated with water vapor.

[0146] In some embodiments, the feed stream has a temperature of about 40°C to about 80°C. In some embodiments, the feed stream has a temperature of about 150°C to about 300°C.

[0147] In some embodiments, the method further includes pressurizing the feed stream to at least about 6 psi before contacting the feed stream with the membrane. In some embodiments, the method further includes pressurizing the feed stream to at most about 60 psi before contacting the feed stream with the membrane.

[0148] In some embodiments, a vacuum pressure is applied to the permeate stream. In some embodiments, impurities are not removed from the feed stream before it comes into contact with the membrane. In some embodiments, water vapor is not removed from the feed stream before it comes into contact with the membrane. In some embodiments, particulate matter is not removed from the feed stream before it comes into contact with the membrane. In some embodiments, the method further includes removing impurities from the permeate stream to produce a CO2-rich stream.

[0149] In some implementations, lime scrubbers are used to remove SO2. x In some implementations, spray dryer absorbers, circulating dry scrubbers, or dry adsorbent injectors are used to remove SO2. xIn some implementations, catalytic oxidation or chemisorption is used to remove O2. In some implementations, selective catalytic reduction (SCR) or non-catalytic reduction (NSCR) is used to remove NO. x In some embodiments, separation or reaction is used to remove H2. In some embodiments, separation or reaction is used to remove H2S. In some embodiments, a carbon bed is used to remove organic molecules.

[0150] In some implementations, the mass flow rate of the permeate stream is at least about 4-10 times smaller than the mass flow rate of the feed stream. In some implementations, the permeate stream is used to produce the final product. In some implementations, the permeate stream is encapsulated.

[0151] In some embodiments, the CO2-rich stream contains at least about 50% CO2. In some embodiments, the CO2-rich stream contains at least about 90% CO2. In some embodiments, the CO2-rich stream contains less than about 8 mol% O2 or less than about 0.5 mol% O2. In some embodiments, the CO2-rich stream contains less than about 1,000 ppm SO2. x In some implementations, the CO2-rich stream contains less than about 1,000 ppm of NO. x In some embodiments, the CO2-rich stream contains less than about 8 mol% H2 or less than about 0.5 mol% H2. In some embodiments, the CO2-rich stream contains less than about 1,000 ppm H2S.

[0152] In some embodiments, the membrane comprises an ionomer. In some embodiments, the ionomer is fluorinated. In some embodiments, the membrane is a transport-enhancing membrane. In some embodiments, the membrane is a hollow fiber membrane, a plate-and-frame membrane, or a spiral-wound flat sheet membrane. In some embodiments, the membrane is humidifying.

[0153] Humidification

[0154] The hydrophilic membranes used herein can be humidified. Humidification can be provided by hydrating the feed stream and / or the permeate side of the housing containing the membrane (membrane separation module), as described in U.S. Patent Application No. 17 / 276,639, which is incorporated herein by reference. In some embodiments, the membrane separation module combines the continuous addition of a stream of liquid water or a purge stream containing water vapor to the permeate gas stream to form a humidified permeate gas stream with the selective permeation of CO2 using a hydrophilic membrane as described in U.S. Patent Application No. 17 / 772,247 (which is incorporated herein by reference). At high operating feed pressures, humidifying the permeate gas stream may be simpler than conventional feed gas humidification. That is, the requirements for separate humidification unit operation for large feed gas streams and precise temperature control between membranes can be reduced.

[0155] Suitable methods for humidifying the membrane include introducing a hydrated fluid containing liquid water into the permeate side of a pressure vessel containing the membrane (permeate-side humidification). This differs from permeate-gas purging humidification, in which a gas or gas composition different from the permeate gas is humidified separately and then passed through the permeate side of the pressure vessel. Here, the hydrated fluid containing liquid water and the permeate-side interface of the membrane are in communication within the pressure vessel (i.e., liquid water or water vapor from the hydrated fluid contacts the permeate-side interface of the membrane). The membrane can be in the form of a flat sheet, hollow fiber, or spiral wound membrane module. The membrane can be non-porous and may also include other layers, such as high diffusion rate (channel) layers and porous supports in composite membrane structures.

[0156] Permeate-side humidification at high operating feed pressures can be simpler than conventional feed gas humidification. That is, by using a hydrated fluid containing liquid water within the permeate side of the pressure vessel, the requirements for precise temperature control between a separate humidification unit operating a large feed gas flow and the membrane can be minimized. The hydrated fluid can also be at the same or slightly lower pressure as the permeate gas and can also act as a permeate purging agent to reduce the permeate concentration at the permeate-side interface and improve overall membrane selectivity. The permeate gas forms bubbles in the hydrated fluid, which either move away from the permeate-side interface due to buoyancy or are purged away from the flowing or recirculating hydrated fluid system. The hydrated fluid can be replenished as it diffuses into the membrane, evaporates, or moves away from the membrane with the permeate bubbles.

[0157] The systems and methods described herein can also utilize membrane separation modules that combine parallel humidification and selective permeation within a single operating unit. This humidification and selective permeation module can comprise two sets of hollow fibers: humidification hollow fibers containing a fluid comprising liquid water within their hollow cores; and hollow fibers containing a non-porous membrane. Continuous humidification of the feed stream within the module can be provided via the humidification hollow fibers, while selective permeation of components in the feed stream occurs via the hollow fibers containing the non-porous membrane. The humidity level in the gaseous feed stream can be maintained and continuously replenished along the flow path of the feed stream because the humidification hollow fibers and the hollow fibers containing the non-porous membrane can be closely overlapped, aligned, mixed, layered, or interwoven. Furthermore, humidification within the module is simpler than conventional feed gas humidification because it eliminates or reduces the requirement for precise temperature control of the gaseous feed stream between individual unit operations.

[0158] Humidifying hollow fibers provide more uniform hydration to hollow fiber membranes, resulting in more consistent permeability and selectivity across the entire module length. The walls of the humidifying hollow fibers permeate with water vapor and act as a barrier to prevent liquid water from entering the flow path of the gaseous feed stream and contacting the hollow fibers containing the non-porous membrane, which can negatively impact overall performance. The humidifying and selective permeation modules described herein can be used where humidification is desired or required to improve gas separation efficiency using membranes, particularly at higher stage cut ratios where a significant portion of the feed stream permeates the membrane.

[0159] The humidifying hollow fiber can be porous (e.g., microporous). The hollow fiber can be made of the same or different materials. The humidifying hollow fiber contains a fluid containing liquid water as a humidification source within its lumen. Water vapor permeates the walls of the humidifying hollow fiber, and it also acts as a barrier to prevent liquid water from entering the flow path of the gaseous feed stream and contacting the membrane, which could be detrimental to overall performance. The hollow fiber is also permeable and acts as a porous support for the non-porous membrane in the composite structure. The composite structure can include additional layers, such as high diffusion rate (channel) layers, which can help reduce interfacial resistance between the hollow fiber and the non-porous membrane and contribute to improved overall permeability and selectivity.

[0160] The humidification and selective permeation modules described herein can be used where humidification is desired or required to improve the gas separation efficiency of the membrane, particularly when operating at higher stage cut ratios, where a large portion of the feed stream permeates the membrane.

[0161] Process conditions

[0162] In one aspect, this paper provides a method for enriching CO2. The method includes providing a feed stream containing CO2 and impurities, wherein the impurities are O2, SO2, etc. x NO x The feed stream may contain H2, CO, VOCs, H2S, or any combination thereof. The method may further include contacting the feed stream with the membrane to generate a permeate stream and a residual stream, wherein the permeate stream contains CO2 and impurities. The method may also include treating the permeate stream to remove impurities. The residual stream may be released into the atmosphere.

[0163] In another aspect, this document provides a system for enriching CO2. The system may include a membrane separation module comprising a membrane, wherein the membrane separation module is configured to receive a feed stream and generate a permeate stream and a residual stream, wherein the feed stream contains CO2 and impurities, wherein the impurities are O2, SO2, etc. x NO xThe permeate stream contains H2, CO, VOC, H2S, or any combination thereof, and the permeate stream contains CO2 and impurities. The system may also include a processing module configured to process the permeate stream to remove impurities. In some cases, the system further includes a humidification module configured to humidify the membrane.

[0164] Before replacement or repair, the membrane can be operated for any appropriate period of time. In some cases, the membrane should be operated for at least 3 months, at least 6 months, at least 1 year, at least 1.5 years, at least 2 years, at least 3 years, at least 4 years, at least 5 years, or at least 10 years.

[0165] Membrane separation modules can produce any suitable amount of permeate within one year. In some cases, membrane separation modules (e.g., as multi-stage or multi-stage configurations) can produce at least about 10,000 tons, at least about 50,000 tons, at least about 100,000 tons, at least about 500,000 tons, or at least about 1,000,000 tons of permeate stream within one year.

[0166] The feed stream (e.g., flue gas) may have any suitable concentration of CO2. In some cases, the feed stream has about 4 mol% to about 50 mol% of CO2, or about 0 mol% to about 15 mol% of O2. In some cases, the feed stream has at least about 2 mol%, at least about 4 mol%, at least about 7 mol%, at least about 10 mol%, at least about 20 mol%, at least about 30 mol%, at least about 40 mol%, and at least about 50 mol% of CO2. In some cases, the feed stream has at most about 2 mol%, at most about 4 mol%, at most about 7 mol%, at most about 10 mol%, at most about 20 mol%, at most about 30 mol%, at most about 40 mol%, and at most about 50 mol% of CO2.

[0167] The feed stream can have any suitable amount of SO x In some cases, the feed stream has SO₂ concentrations of approximately 10 ppm, 50 ppm, 100 ppm, 500 ppm, 1,000 ppm, 5,000 ppm, 10,000 ppm, or 50,000 ppm. x In some cases, the feed stream has SO₂ concentrations of less than about 10 ppm, less than about 50 ppm, less than about 100 ppm, less than about 500 ppm, less than about 1,000 ppm, less than about 5,000 ppm, less than about 10,000 ppm, or less than about 50,000 ppm. xIn some cases, the feed stream has SO₂ concentrations of more than about 10 ppm, more than about 50 ppm, more than about 100 ppm, more than about 500 ppm, more than about 1,000 ppm, more than about 5,000 ppm, more than about 10,000 ppm, or more than about 50,000 ppm. x .

[0168] The feed stream can have any suitable amount of NO x In some cases, the feed stream has NO concentrations of approximately 10 ppm, 50 ppm, 100 ppm, 500 ppm, 1,000 ppm, 5,000 ppm, 10,000 ppm, or 50,000 ppm. x In some cases, the feed stream has NO concentrations of less than about 10 ppm, less than about 50 ppm, less than about 100 ppm, less than about 500 ppm, less than about 1,000 ppm, less than about 5,000 ppm, less than about 10,000 ppm, or less than about 50,000 ppm. x In some cases, the feed stream has more than about 10 ppm, more than about 50 ppm, more than about 100 ppm, more than about 500 ppm, more than about 1,000 ppm, more than about 5,000 ppm, more than about 10,000 ppm, or more than about 50,000 ppm of NO. x .

[0169] The feed stream (e.g., flue gas) may have any suitable amount of H2. In some cases, the feed stream has about 0 mol% to about 5 mol% of H2. In some cases, the feed stream has about 0 mol%, about 1 mol%, about 3 mol%, about 5 mol%, about 10 mol%, about 15 mol%, about 20 mol%, or about 30 mol% of H2. In some cases, the feed stream has at least about 0 mol%, at least about 1 mol%, at least about 3 mol%, at least about 5 mol%, at least about 10 mol%, at least about 15 mol%, at least about 20 mol%, or at least about 30 mol% of H2. In some cases, the feed stream has at most about 0 mol%, at most about 1 mol%, at most about 3 mol%, at most about 5 mol%, at most about 10 mol%, at most about 15 mol%, at most about 20 mol%, or at most about 30 mol% of H2.

[0170] The feed stream can contain any suitable amount of CO. In some cases, the feed stream contains about 0 mol% to about 5 mol% CO. In some cases, the feed stream contains about 0 mol%, about 1 mol%, about 3 mol%, about 5 mol%, about 10 mol%, about 15 mol%, about 20 mol%, or about 30 mol% CO. In some cases, the feed stream contains at least about 0 mol%, at least about 1 mol%, at least about 3 mol%, at least about 5 mol%, at least about 10 mol%, at least about 15 mol%, at least about 20 mol%, or at least about 30 mol% CO. In some cases, the feed stream contains at most about 0 mol%, at most about 1 mol%, at most about 3 mol%, at most about 5 mol%, at most about 10 mol%, at most about 15 mol%, at most about 20 mol%, or at most about 30 mol% CO.

[0171] The feed stream can have any suitable amount of VOC. In some cases, the feed stream has VOC of about 10 ppm, about 50 ppm, about 100 ppm, about 500 ppm, about 1,000 ppm, about 5,000 ppm, about 10,000 ppm, or about 50,000 ppm. In other cases, the feed stream has VOC of less than about 10 ppm, less than about 50 ppm, less than about 100 ppm, less than about 500 ppm, less than about 1,000 ppm, less than about 5,000 ppm, less than about 10,000 ppm, or less than about 50,000 ppm. In some cases, the feed stream has more than about 10 ppm, more than about 50 ppm, more than about 100 ppm, more than about 500 ppm, more than about 1,000 ppm, more than about 5,000 ppm, more than about 10,000 ppm, or more than about 50,000 ppm of VOCs.

[0172] The feed stream can have any suitable amount of H2S. In some cases, the feed stream has about 10 ppm, about 50 ppm, about 100 ppm, about 500 ppm, about 1,000 ppm, about 5,000 ppm, about 10,000 ppm, or about 50,000 ppm of H2S. In other cases, the feed stream has less than about 10 ppm, less than about 50 ppm, less than about 100 ppm, less than about 500 ppm, less than about 1,000 ppm, less than about 5,000 ppm, less than about 10,000 ppm, or less than about 50,000 ppm of H2S. In some cases, the feed stream has more than about 10 ppm, more than about 50 ppm, more than about 100 ppm, more than about 500 ppm, more than about 1,000 ppm, more than about 5,000 ppm, more than about 10,000 ppm, or more than about 50,000 ppm of H2S.

[0173] The feed stream can be flue gas produced by combustion. The feed stream can be complex (e.g., containing several types of impurities). The feed stream can contain O2, SO2, etc. x NO x The feed stream may contain at least two, at least three, at least four, at least five, at least six, or all seven of the following: H2, CO, VOC, and H2S.

[0174] The feed stream may contain water vapor and may be saturated with water vapor. The feed stream may contain about 0 mol% to about 20 mol% H2O. In some cases, the feed stream contains about 0 mol%, about 1 mol%, about 3 mol%, about 5 mol%, about 10 mol%, about 15 mol%, about 20 mol%, about 25 mol%, about 30 mol%, or about 35 mol% H2O. In some cases, the feed stream contains at least about 0 mol%, at least about 1 mol%, at least about 3 mol%, at least about 5 mol%, at least about 10 mol%, at least about 15 mol%, at least about 20 mol%, at least about 25 mol%, at least about 30 mol%, or at least about 35 mol% H2O. In some cases, the feed stream has up to about 0 mol%, up to about 1 mol%, up to about 3 mol%, up to about 5 mol%, up to about 10 mol%, up to about 15 mol%, up to about 20 mol%, up to about 25 mol%, up to about 30 mol%, or up to about 35 mol% H2O.

[0175] The feed stream can have any suitable temperature. In some cases, the feed stream has a temperature of about 80°C to about 300°C. In some cases, the feed stream has a temperature of about 20°C, about 30°C, about 40°C, about 60°C, about 80°C, about 100°C, about 120°C, about 140°C, about 160°C, about 180°C, about 200°C, about 250°C, about 300°C, about 350°C, or about 400°C. In some cases, the feed stream has a temperature of at least about 20°C, at least about 30°C, at least about 40°C, at least about 60°C, at least about 80°C, at least about 100°C, at least about 120°C, at least about 140°C, at least about 160°C, at least about 180°C, at least about 200°C, at least about 250°C, at least about 300°C, at least about 350°C, or at least about 400°C. In some cases, the feed stream has a temperature of up to about 20°C, up to about 30°C, up to about 40°C, up to about 60°C, up to about 80°C, up to about 100°C, up to about 120°C, up to about 140°C, up to about 160°C, up to about 180°C, up to about 200°C, up to about 250°C, up to about 300°C, up to about 350°C, or up to about 400°C.

[0176] The systems and methods described herein may also include pressurizing the feed stream and / or applying a vacuum pressure to the permeate stream (e.g., before bringing the feed stream into contact with the membrane). The pressure differential across the membrane (e.g., the feed stream pressure and / or the vacuum pressure of the permeate) may be approximately 2 psi, approximately 4 psi, approximately 6 psi, approximately 8 psi, approximately 10 psi, approximately 15 psi, approximately 20 psi, approximately 30 psi, approximately 40 psi, approximately 60 psi, approximately 80 psi, approximately 100 psi, approximately 120 psi, approximately 140 psi, or approximately 160 psi. The transmembrane pressure differential can be at least approximately 2 psi, at least approximately 4 psi, at least approximately 6 psi, at least approximately 8 psi, at least approximately 10 psi, at least approximately 15 psi, at least approximately 20 psi, at least approximately 30 psi, at least approximately 40 psi, at least approximately 60 psi, at least approximately 80 psi, at least approximately 100 psi, at least approximately 120 psi, at least approximately 140 psi, or at least approximately 160 psi. The transmembrane pressure differential can be at most approximately 2 psi, at most approximately 4 psi, at most approximately 6 psi, at most approximately 8 psi, at most approximately 10 psi, at most approximately 15 psi, at most approximately 20 psi, at most approximately 30 psi, at most approximately 40 psi, at most approximately 60 psi, at most approximately 80 psi, at most approximately 100 psi, at most approximately 120 psi, at most approximately 140 psi, or at most approximately 160 psi.

[0177] The systems and methods described herein simplify the handling of impurities. In some cases, impurities are not removed from the feed stream before it comes into contact with the membrane. In some cases, water vapor is not removed from the feed stream before it comes into contact with the membrane. In some embodiments, particulate matter is not removed from the feed stream before it comes into contact with the membrane. The systems and methods may also include removing impurities from the permeate stream to produce a CO2-rich stream. SO2 can be removed using a lime scrubber. x SO2 can be removed using spray dryer absorbers, circulating dry scrubbers, or dry adsorbent injectors. x O2 can be removed using catalytic oxidation or chemisorption. NO can be removed using selective catalytic reduction (SCR) or non-catalytic reduction (NSCR). x H2 can be removed by separation or reaction. H2S can be removed by separation or reaction. Organic molecules can be removed using a carbon bed.

[0178] The advantage of the system and method described herein is that the mass flow rate of the permeate stream is less than that of the feed stream. The mass flow rate of the permeate stream can be at least about 4 to 10 times smaller than that of the feed stream. In some cases, the mass flow rate of the permeate stream can be at least about 2, 3, 4, 6, 8, 10, 20, or 50 times smaller than that of the feed stream.

[0179] Permeate streams can be used to produce final products. Permeate streams can be sealed.

[0180] The CO2-rich stream can have any suitable high concentration of CO2. In some embodiments, it contains about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, about 85%, about 90%, about 95%, about 97%, about 99%, about 99.5%, or about 99.9% CO2. In some embodiments, it contains at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 97%, at least about 99%, at least about 99.5%, or at least about 99.9% CO2.

[0181] CO2-rich streams can have any suitable low concentration of one or more impurities. In some cases, CO2-rich streams have less than about 12 mol% O2, less than about 10 mol% O2, less than about 8 mol% O2, less than about 6 mol% O2, less than about 4 mol% O2, less than about 2 mol% O2, less than about 1 mol% O2, less than about 0.5 mol% O2, less than about 0.1 mol% O2, less than about 0.05 mol% O2, or less than about 0.001 mol% O2.

[0182] CO2-rich streams can have any suitable amount of SO2. x In some cases, the feed stream has SO₂ concentrations of approximately 10 ppm, 50 ppm, 100 ppm, 500 ppm, 1,000 ppm, 5,000 ppm, 10,000 ppm, or 50,000 ppm. x In some cases, CO2-rich streams have SO2 concentrations of less than about 10 ppm, less than about 50 ppm, less than about 100 ppm, less than about 500 ppm, less than about 1,000 ppm, less than about 5,000 ppm, less than about 10,000 ppm, or less than about 50,000 ppm. x In some cases, CO2-rich streams have SO2 concentrations of more than about 10 ppm, more than about 50 ppm, more than about 100 ppm, more than about 500 ppm, more than about 1,000 ppm, more than about 5,000 ppm, more than about 10,000 ppm, or more than about 50,000 ppm. x .

[0183] CO2-rich streams can have any suitable amount of NO x In some cases, CO2-rich streams have NO concentrations of approximately 10 ppm, 50 ppm, 100 ppm, 500 ppm, 1,000 ppm, 5,000 ppm, 10,000 ppm, or 50,000 ppm. x In some cases, CO2-rich streams have NO concentrations of less than about 10 ppm, less than about 50 ppm, less than about 100 ppm, less than about 500 ppm, less than about 1,000 ppm, less than about 5,000 ppm, less than about 10,000 ppm, or less than about 50,000 ppm. xIn some cases, CO2-rich streams have NO concentrations of more than about 10 ppm, more than about 50 ppm, more than about 100 ppm, more than about 500 ppm, more than about 1,000 ppm, more than about 5,000 ppm, more than about 10,000 ppm, or more than about 50,000 ppm. x .

[0184] A CO2-rich stream can have any suitable amount of H2. In some cases, the CO2-rich stream has about 0 mol% to about 5 mol% of H2. In some cases, the CO2-rich stream has about 0 mol%, about 1 mol%, about 3 mol%, about 5 mol%, about 10 mol%, about 15 mol%, about 20 mol%, or about 30 mol% of H2. In some cases, the CO2-rich stream has at least about 0 mol%, at least about 1 mol%, at least about 3 mol%, at least about 5 mol%, at least about 10 mol%, at least about 15 mol%, at least about 20 mol%, or at least about 30 mol% of H2. In some cases, the CO2-rich stream has at most about 0 mol%, at most about 1 mol%, at most about 3 mol%, at most about 5 mol%, at most about 10 mol%, at most about 15 mol%, at most about 20 mol%, or at most about 30 mol% of H2.

[0185] CO2-rich streams can have any suitable amount of H2S. In some cases, CO2-rich streams have about 10 ppm, about 50 ppm, about 100 ppm, about 500 ppm, about 1,000 ppm, about 5,000 ppm, about 10,000 ppm, or about 50,000 ppm of H2S. In other cases, CO2-rich streams have less than about 10 ppm, less than about 50 ppm, less than about 100 ppm, less than about 500 ppm, less than about 1,000 ppm, less than about 5,000 ppm, less than about 10,000 ppm, or less than about 50,000 ppm of H2S. In some cases, CO2-rich streams have H2S concentrations of more than about 10 ppm, more than about 50 ppm, more than about 100 ppm, more than about 500 ppm, more than about 1,000 ppm, more than about 5,000 ppm, more than about 10,000 ppm, or more than about 50,000 ppm.

[0186] The performance of hydrophilic membranes can be characterized in terms of permeability and selectivity. Permeability is the rate at which a component travels across the membrane surface area under a given driving force and is an effective measure of the separation volume. Increased permeability enables the processing of large streams with minimal surface area. This performance metric is typically expressed in GPUs (gas permeation units). The selectivity of one component over another is the ratio of the permeabilities of the two components and is a measure of the quality of separation. This indicates how much CO2 passes through the membrane compared to N2. Both metrics are functions of membrane operating conditions and are only useful when measured under actual field conditions (e.g., pressure, temperature, stage cut ratio).

[0187] Example 1 - Generation of Liquid or Supercritical CO2

[0188] Figure 1 The system shown can be used to generate liquid or supercritical CO2. Various streams can have any suitable composition, temperature, and pressure, and unit operations can operate under any suitable conditions.

[0189] In this embodiment, the flue gas 100 may contain approximately 4-30% CO2, have a pressure of approximately 1 bar, and a temperature of approximately 40-80°C. The flue gas can be compressed 102 to approximately 2-10 bar. The membrane separation module 104 can generate a lean CO2 stream 106 with approximately 0.5-4% CO2, a pressure of approximately 2-10 bar, and a temperature of approximately 40-80°C. Energy can be recovered 108 to reduce the pressure of the residual stream 128 to approximately 1 bar.

[0190] continue Figure 1 The CO2-rich stream 112 can have approximately 30% to approximately 95% CO2 at 1 bar and 40-80°C. It can be compressed 110 to approximately 30-60 bar and supplied to the TSA 114, where water is removed to less than 30 ppm. Oxygen can be removed 116 to less than 30 ppm. The cryogenic separation module can produce a distillate 125 with approximately 30-90% CO2 at a pressure of 30-50 bar and a temperature of approximately -45°C to approximately -30°C. After heat exchange 122, the cryogenic distillate 132 can have approximately 30-90% CO2 at a pressure of 1-10 bar and a temperature of approximately -0°C to approximately 30°C.

[0191] Finally, continue Figure 1 The output 126 from the cryogenic separation module can be liquid or supercritical CO2 with 98-99.5% or more CO2, at a pressure of 30-50 bar (or 30-50 bar if passing through pump or valve 130) and a temperature of about -30°C to about 10°C (or -30°C to 30°C if passing through pump or valve 130).

[0192] Although preferred embodiments of the invention have been shown and described herein, it will be apparent to those skilled in the art that these embodiments are provided by way of example only. The invention is not intended to be limited to the specific examples provided in the specification. Although the invention has been described with reference to the foregoing description, the description and illustration of embodiments herein should not be construed as limiting. Many variations, alterations, and substitutions will occur to those skilled in the art without departing from the invention. Furthermore, it should be understood that all aspects of the invention are not limited to the specific depictions, constructions, or relative proportions set forth herein, as these depend on various conditions and variables. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in carrying out the invention. Therefore, the invention is also intended to cover any such alternatives, modifications, variations, or equivalents. The scope of the invention is intended to be defined by the following claims, and thereby covers methods and structures falling within the scope of these claims and their equivalents.

[0193] These and other modifications can be made to the embodiments based on the detailed description above. Generally, the terminology used in the following claims should not be construed as limiting the claims to the specific embodiments disclosed in the specification and claims, but rather as encompassing all possible embodiments and the full scope of equivalents to which these claims are entitled. Therefore, the claims are not limited by the disclosure. This application claims priority to U.S. Provisional Application No. 63 / 592,073, filed October 20, 2023, U.S. Provisional Application No. 63 / 592,083, filed October 20, 2023, and U.S. Provisional Application No. 63 / 670,575, filed July 12, 2024, the entire contents and disclosure of which are incorporated herein by reference.

Claims

1. A method for enriching CO2, the method comprising: a. Using a membrane separation module to separate a CO2-containing feed stream into a CO2-rich stream and a CO2-lean stream, wherein the membrane separation module comprises a hydrophilic membrane and the feed stream is humidified; b. Use a drying module to dry the CO2-rich stream to produce a water-containing stream and a dried CO2 stream; c. Use a low-temperature separation module to separate the dried CO2 stream into a liquid or supercritical CO2 stream and a distillate stream; d. The distillate stream is recycled to the drying module, thereby merging the distillate stream with the water-containing stream to produce a humidified distillate stream; as well as e. Recycle the humidified distillate stream back to the membrane separation module.

2. The method according to claim 1, wherein the feed stream is flue gas.

3. The method according to claim 1 or 2, wherein the feed stream contains 4% to 30% CO2.

4. The method according to any one of claims 1-3, wherein the feed stream has a pressure of about 1 bar.

5. The method according to any one of claims 1-4, wherein the feed stream is compressed to 2 bar to 10 bar before being fed to the membrane separation module.

6. The method according to any one of claims 1-5, wherein the membrane separation module has a plurality of hydrophilic membranes configured in at least two segments and / or at least two stages.

7. The method according to any one of claims 1-6, wherein the hydrophilic membrane comprises an ionomer.

8. The method according to any one of claims 1-7, wherein the hydrophilic membrane is fluorinated.

9. The method according to any one of claims 1-8, wherein the hydrophilic membrane is a transport-enhancing membrane.

10. The method according to any one of claims 1-9, wherein the hydrophilic membrane is a hollow fiber membrane, a plate-and-frame membrane, or a spiral wound membrane.

11. The method according to any one of claims 1-10, wherein the hydrophilic membrane is humidified.

12. The method according to any one of claims 1-11, wherein the drying module comprises a temperature-switching adsorption (TSA) module.

13. The method of claim 12, wherein the TSA is regenerated using the distillate stream.

14. The method according to any one of claims 12 or 13, wherein the heat for regenerating the TSA is provided at least in part by compressing the CO2-rich stream.

15. The method according to any one of claims 1-14, wherein the dried CO2 stream has less than 100 ppm of water.

16. The method according to any one of claims 1-15, wherein the cryogenic separation module comprises a propylene refrigeration circuit.

17. The method according to any one of claims 1-16, wherein the distillate stream is used to cool the dried CO2 stream before being recycled to the drying module.

18. The method according to any one of claims 1-17, wherein the distillate stream comprises 30% to 90% CO2.

19. The method according to any one of claims 1-18, wherein the liquid or supercritical CO2 stream comprises 98% to 99.9% CO2.

20. The method according to any one of claims 1-19, wherein the humidified distillate stream is fed to a compressor upstream of the membrane separation module.

21. The method according to any one of claims 1-20, wherein the humidified distillate stream is fed to a section or stage of the membrane separation module.

22. The method according to any one of claims 1-21, wherein a portion of the humidified distillate stream is combined with a CO2-rich stream downstream of the membrane separation module.

23. The method according to any one of claims 1-22, wherein a portion of the distillate stream is fed to the membrane separation module, rather than first to the drying module.

24. The method according to any one of claims 1-23, further comprising feeding the dried CO2 stream to a deoxygenation module before feeding the dried CO2 stream to the cryogenic separation module.

25. The method according to any one of claims 1-24, further comprising deoxygenating the liquid or supercritical CO2 stream.

26. A method for enriching CO2, the method comprising: a. Provide a feed stream containing at least about 60% CO2 on a dry basis, having a pressure of at least 30 bar, having less than about 500 ppm of water, and having a temperature below about 0°C; b. Low-temperature enrichment of CO2 from the feed stream to produce a bottom product containing at least 95% CO2 and a top product containing less than 40% CO2; c. Inflate the top product to a pressure of less than about 5 bar; as well as d. Use a membrane separation module to enrich CO2 from the expanded top product and recycle the enriched CO2 back to the feed stream.

27. The method of claim 26, wherein the feed stream originates from an oxygen-enriched combustion process.

28. A system configured to carry out the method of any one of the preceding claims.

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