Pre-concentration of carbon dioxide in a membrane from exhaust gas sources

Abstract

The process of pre-concentrating CO2 in an exhaust gas stream involves passing the entire exhaust gas stream from the exhaust gas source to a CO2 pre-concentration system. In the CO2 pre-concentration system, at least a portion of the exhaust gas stream is supplied to a membrane separation module equipped with a polymer membrane that has higher permeability selectivity for CO2 than for N2 and O2, thereby producing CO2-enriched exhaust gas. The exhaust gas stream may initially have a low CO2 content of around 400 ppm and can be pre-concentrated to more than 8 volume percent of CO2, thereby producing a feedstock that is more optimal for further processing.

Description

Technical Field

[0001] The present disclosure relates to membrane-based gas separation systems and methods for enhancing the recovery of carbon dioxide (CO2).

Background Art

[0002] This section is intended to introduce the reader to various technical aspects that may be related to the various aspects of the present disclosure described and / or claimed below. This discussion is thought to be useful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Thus, it should be understood that these descriptions are to be read from this perspective and not as an admission of prior art.

[0003] In upstream oil fields, a significant amount of steam is required and injected underground to enhance oil recovery operations. In cogeneration plants (combined heat and power plants), natural gas is burned as fuel to generate steam in a steam generator. In some of these cogeneration plants, the exhaust flue gas of a gas turbine engine is the main CO2 emission source and contains about 3 - 4 volume% of CO2. Such a CO2 level is often considered to be a relatively low CO2 concentration as exhaust gas. Other exhaust gases with low CO2 concentrations (e.g., less than 8 volume% of CO2) may be observed, for example, from combined cycle gas turbines (CCGTs), shipboard generators (operating on fuels such as liquefied natural gas or light oil), or natural gas combined cycle (NGCC) sources.

[0004] To reduce total CO2 emissions from these types of plants, flue gas CO2 needs to be recovered and reused / stored for other purposes. One method implemented for CO2 recovery is the use of amine absorption with a solvent such as monoethanolamine (MEA). In one example process, the flue gas is first cooled to a suitable temperature, such as 50°C, and then compressed by a blower to overcome pressure losses by downstream equipment. The flue gas then passes through an amine plant equipped with an amine absorber to remove CO2 and an amine regenerator to recover CO2 from the solvent. This process requires both power and steam to circulate and regenerate the solvent. One drawback of amine processes for recovering low-CO2 exhaust gas is the need for steam, and the associated costs are significantly higher compared to other high-CO2 emission sources. Furthermore, high steam consumption leads to higher operating costs, and consequently, higher indirect CO2 emissions from fuel combustion. When the CO2 concentration in the flue gas is low, the gas processing equipment in the amine plant also becomes larger due to the high volumetric flow rate. [Overview of the project]

[0005] The following outlines some of the specific embodiments disclosed herein. It should be understood that these embodiments are presented merely to provide the reader with a brief overview of these specific embodiments, and that they are not intended to limit the scope of this disclosure. In fact, this disclosure may encompass a variety of embodiments not shown below.

[0006] According to one embodiment, the process for pre-concentrating CO2 in an exhaust gas stream includes: feeding the entire exhaust gas stream from the exhaust gas source into a CO2 pre-concentration system; and within this CO2 pre-concentration system, supplying at least a portion of the exhaust gas stream to a membrane separation module equipped with a polymeric membrane having higher permeability selectivity for CO2 than for N2 and O2; generating CO2-enriched exhaust gas on the permeate side of the membrane separation module; and generating CO2-dilute gas on the holding side of the membrane separation module. This exhaust gas stream has a low CO2 concentration of about 400 ppm CO2, and the CO2-enriched exhaust gas has a CO2 concentration of up to 20 volume% CO2.

[0007] According to another embodiment, the CO2 pre-concentration system comprises a channel configured to receive a CO2 source stream having a CO2 concentration of less than 8 volume percent; and a membrane separation module positioned along the channel and configured to receive at least a portion of the CO2 source stream. The membrane separation module comprises a polymer membrane having greater permeation selectivity for CO2 than for N2 and O2. The system also comprises a vacuum source connected to the permeate side of the membrane separation module, which is configured to create a pressure difference across the polymer membrane, thereby facilitating gas permeation across the polymer membrane to generate a retainate flow and a permeate flow. The permeate flow has a higher CO2 concentration than the CO2 source stream. The system further comprises a channel for a pre-concentration stream configured to pass the permeate flow into a system configured to utilize, store, or further concentrate the CO2 in the permeate flow.

[0008] Various embodiments of this disclosure, along with further objectives and advantages, can be best understood by referring to the following description in conjunction with the accompanying drawings. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 shows an example of an existing exhaust gas recirculation (EGR) system.

[0010] [Figure 2] Figure 2 shows an example of a pre-enrichment system that, according to an embodiment of the present disclosure, uses a membrane module for pre-enriching CO2 from exhaust gas having 3 volume% CO2 to produce pre-enriched exhaust gas having more than 8 volume% CO2.

[0011] [Figure 3] Figure 3 shows another exemplary embodiment of a pre-concentration system that, according to embodiments of the present disclosure, utilizes a membrane module to pre-concentrate CO2 from exhaust gas having 3 volume% CO2 to produce pre-concentrated exhaust gas having more than 8 volume% CO2.

[0012] [Figure 4] Figure 4 shows an exemplary embodiment of a pre-enrichment system that, according to an embodiment of the present disclosure, utilizes a membrane module to pre-enrich CO2 from an atmosphere having approximately 400 ppm of CO2 to produce a pre-enriched gas having approximately 8-20 volume percent of CO2.

[0013] [Figure 5] Figure 5 shows an exemplary embodiment of a pre-enrichment system that, according to an embodiment of the present disclosure, utilizes a membrane module to pre-enrich CO2 from an atmosphere having approximately 400 ppm of CO2 to produce a pre-enriched gas having approximately 8-20 volume percent of CO2.

[0014] [Figure 6] Figure 6 shows an exemplary embodiment of a pre-concentration system, which uses a membrane module to pre-concentrate CO2 from exhaust gas containing approximately 8-10 volume percent CO2, according to an embodiment of the present disclosure.

[0015] [Figure 7] Figure 7 shows an exemplary embodiment of a pre-concentration system that utilizes a membrane module for pre-concentrating CO2 from exhaust gas having 3 volume% CO2, according to an embodiment of the present disclosure. [Modes for carrying out the invention]

[0016] The terms exhaust gas, exhaust flue gas, and flue gas are used interchangeably herein. As described above, recovering CO2 from flue gas with low CO2 concentrations using amine-based systems can be inefficient. A different approach available for flue gas with low CO2 concentrations (e.g., less than 8 vol% CO2) is to pre-enrich the CO2 in the flue gas (or other source gas) before it reaches the amine-based process (or other process) for final CO2 recovery (thereby reducing the energy / cost load). By enriching the CO2, the volumetric flow rate of the flue gas is also reduced, which allows for the use of smaller or fewer gas treatment equipment overall compared to processes without pre-enrichment. One example is to reduce the number of absorption rows or rows, thereby reducing both equipment footprint and system costs. It may also be preferable that the pre-enrichment step does not require additional steam and does not result in significant process inefficiencies or increases in other emissions.

[0017] Existing approaches for pre-concentrating CO2 are to use exhaust gas recirculation (EGR) or semi-closed-cycle processes, as shown in Figure 1 illustrating an exemplary embodiment of an EGR system 10. Starting from the center of Figure 1, the engine / combustor system 12 generates power and exhaust gases 14 through fuel combustion. From a process perspective, the exhaust gases 14 are generally recirculated back into the engine / combustor system 12 via an intake 16.

[0018] The EGR process produces CO2-enriched exhaust gas, which can be further treated, but the EGR process has certain limitations. For example, the EGR process reduces the oxygen concentration in the engine's gas combustor. As the oxygen concentration decreases (due to recycled gas), the engine's combustion efficiency may decrease, and there may also be an increase in other emissions (e.g., an increase in carbon monoxide (CO)). One way the EGR process addresses the reduction in O2 is to add an air separator 18 upstream of the combustor to increase the O2 concentration in the combustor, as shown on the far left of Figure 1. The air separator requires considerable power due to the presence of one or more compressors, in addition to its capital and operational expenditures.

[0019] Another limitation of the EGR process is that the water associated with the cooled exhaust gas is also recirculated back to the combustor, which can negatively impact engine efficiency. One way to mitigate the presence of water is to add another cooler (before recycling), which increases costs and complexity. In Figure 1, the exhaust gas produced in the combustor is sent to a cooler 20 and a water separation unit 22, which produces a CO2-enriched exhaust gas 24 (e.g., having more than 8 volume% CO2) and a CO2-lean exhaust gas 26. The CO2-lean exhaust gas is recirculated to the intake 16 as shown.

[0020] To address these and other shortcomings of existing approaches, this disclosure relates to the use of a CO2-selective membrane system for pre-concentrating low-CO2 exhaust flue gas to an intermediate CO2 concentration useful for other concentration, storage, or utilization processes. The term “CO2 selectivity” of a membrane means that the membrane used in such a system (or module) is highly permeable to CO2 compared to other gases such as oxygen and nitrogen. Higher permeability to one gas than to another may also be called permeability selectivity. The membrane is a polymer, and is generally made of glassy or rubbery polymers. Such membranes and their structures for use in membrane modules are well known. As an example, the CO2 / N2 selectivity of a membrane used according to this disclosure may be at least 10, for example, 10 to 100.

[0021] Advantageously, the membrane-based separation system can operate in continuous mode and requires neither steam nor a regeneration step. While there have been examples of using membranes for flue gas CO2 recovery (e.g., via multiple membrane stages and / or from high CO2 exhaust gas sources), this embodiment uses only membranes to pre-concentrate CO2 for low-concentration CO2 emission sources. According to this disclosure, low-CO2 concentration exhaust sources may have CO2 concentrations of up to 8 vol% CO2, but generally less than 8 vol% CO2.

[0022] In fact, membrane-based separation systems (e.g., membrane modules, which may also be referred to as membrane separation modules instead) are modular and recognized to be applicable to various flue gas sources. The membrane system can obtain a stream with a CO2 concentration as low as about 400 ppm CO2 and generate a CO2-enriched stream of up to 8 - 10 volume %, which can be passed to other recovery paths or applied to CO2 utilization paths. Another example is using such a membrane-based separation system to concentrate a stream with a moderately low CO2 concentration (e.g., 8 - 10 volume %) to above 15 volume % (e.g., between 15 - 30 volume %, e.g., 16 - 20 volume %) for other recovery methods, and this system typically requires such a minimum concentration to operate efficiently. Thus, membrane-based separation systems can also be used in some hybrid configurations to make a particular CO2 recovery process more efficient and economical overall. Therefore, the present disclosure includes using a pre-concentration system having a membrane separation module to pre-concentrate CO2 in exhaust gas having a first CO2 concentration to generate a pre-concentrated exhaust gas having a second CO2 concentration higher than the first CO2 concentration. In some embodiments, the second CO2 concentration is a concentration corresponding to an exhaust gas CO2 concentration at which another type of CO2 treatment process is optimal or otherwise particularly suitable. The membrane-based pre-concentration system of the present disclosure can generate a pre-concentrated stream having a CO2 concentration at least 1.25 times higher than the input stream. As an example, the pre-concentration system can generate a pre-concentrated stream having a CO2 concentration 1.25 - 20 times higher than the input stream, e.g., 1.5 - 10 times higher, 1.75 - 6 times higher, or 2 - 4 times higher than the input stream.

[0023] Figures 2 and 3 illustrate an example of the membrane pre-concentration system 100. Referring now to FIG. 2, the system 100 includes an exhaust gas flow path that receives flue gas 102, particularly exhaust gas with a low CO2 concentration (in the illustrated embodiment, as a non-limiting example, corresponding to approximately 3% by volume of CO2 (e.g., a first concentration)). As described above, such a flue gas flow can be generated in a cogeneration plant, a combined cycle gas turbine (CCGT), a shipboard generator (e.g., operating on LNG), or a natural gas combined cycle (NGCC) source, etc. in a particular combustion system 103. These sources can generate other concentrations in some embodiments. For example, the flue gas 102 can have less than 8% by volume of CO2, e.g., 0.5% to 8% by volume of CO2, 1% to 6% by volume of CO2, or 2% to 4% by volume of CO2.

[0024] The pre-concentration system 100 can receive all of the exhaust gas generated by the combustion system 103 along the exhaust gas flow path. As will be described below with respect to FIGS. 2, 3, 6, and 7, various functional components are arranged along the exhaust gas flow path to process the exhaust gas.

[0025] [[ID=Z]] The system 100 in Figure 2 comprises various functional units arranged along the exhaust gas flow path, including a blower or compressor 104 which provides sufficient pressure driving force to the flue gas 102 through at least one cooler 106 arranged along the exhaust gas flow path of the system 100. The flue gas 102 from the combustion system 103 may be too hot to be processed directly by the membrane module 108, and therefore, the flue gas 102 may be cooled in the cooler 106 to a temperature of 25°C to 80°C, as a non-limiting example. The cooled flue gas is then sent to the feed side of the membrane module 108 for CO2 separation. The membrane separation module 108 is also arranged along the exhaust gas flow path of the pre-concentration system 100. Membrane separation is driven by a vacuum source 110 downstream or on the permeate side, which generates a CO2-enriched gas or pre-concentrated CO2 stream 112 (corresponding in this embodiment to the permeate side stream 113) having more than 8 volume% CO2, which may be called a pre-concentrated CO2 stream. As a non-limiting example, a pre-enriched CO2 stream 112 may contain 8 vol% to 20 vol% CO2, for example, 10 vol% to 18 vol% CO2, or 12 vol% to 16 vol% CO2.

[0026] The membrane separation module 108 comprises one or more CO2-selective membranes 114, as shown in the figure, enabling the selective permeation of CO2 over oxygen (O2) and nitrogen (N2). Thus, the flow exiting the permeate side of module 108 is a CO2-enriched flow (i.e., CO2-enriched gas, pre-enriched flow 112), while the flow exiting the retaining side of module 108 is a CO2-reduced flow (i.e., CO2-dilute gas 116). Generally, according to this embodiment, it is preferable to create a pressure difference between the permeate and retaining sides of the membrane 114 using a vacuum source 110. This is because, when the initial CO2 concentration of the supply gas is relatively low (e.g., less than 8 volume percent CO2), this technique has been found to allow for a greater amount of CO2 enrichment compared to most sweep gas configurations. However, using a sweep gas either instead of or in addition to the vacuum pump 110 to facilitate CO2 permeation by the polymer membrane 114 (intended to represent one or more membranes) is also within the scope of this disclosure for specific embodiments.

[0027] The pre-concentration flow, a CO2-enriched flow (pre-concentration flow 112) generated by system 100, can be delivered to another system 118 for further concentration, storage, or further use. In non-limiting examples, system 118 may be an amine-based system, another membrane-based separation system, a CO2 injection system, a system that converts CO2 to another chemical substance, or any combination thereof. The pre-concentration system 100 may include a pre-concentration flow path that fluidly connects the permeate side of the membrane separation module 108 to system 118. According to this embodiment, system 118 is not an exhaust gas recirculation / recycle (EGR) system. In other words, the permeate side flow 113, either alone or in combination with other flows, is not sent as a recycle flow to a gas turbine engine.

[0028] The embodiment of the pre-concentration system 100 illustrated in Figure 3 operates on the same principle as the system 100 in Figure 2 with respect to the treatment of exhaust gas 102. Instead of treating the entire flue gas flow, the system 100 in Figure 3 treats a first partial flow 130 generated by a gas split 132 located upstream of the membrane separation module 108 and along the exhaust gas flow path. In this embodiment, the gas split 132 is located upstream of the blower or compressor 104 and the cooler 106. However, the gas split 132 may be located at any point upstream of the membrane separation module 108, such as between the blower or compressor 104 and the membrane separation module 108.

[0029] The first partial flow 130 of flue gas 102 is delivered via a blower or compressor 104, while the second partial flow 134 of flue gas 102 is delivered directly to the gas combiner 136. The gas combiner 136 combines the permeate sideflow 113 from the membrane module 108 with the second partial flow 134 of flue gas 102 to produce a pre-concentrated CO2 flow 112.

[0030] The difference when using the pre-concentration system 100 in Figure 2 or 3 depends primarily on the type of membrane selected for separation and its separation characteristics. The separation characteristics of the membrane 114 may include gas permeability and selectivity. Table 1 shows examples of two different membranes and their impact on the resulting CO2 purity. In this particular example, according to system 100 in Figure 3, 80% of the flue gas volume is permeated through membrane module 108, while 20% of the flue gas bypasses membrane module 108. In other words, in the example in Table 1, 80% of the flue gas 102 is the first portion 130 and 20% is the second portion 134.

[0031] Therefore, 80% undergoes pre-concentration (generating permeate side flow 113), and is recombined with untreated flue gas (flow 130) to produce CO2-enriched exhaust gas 112, as shown in Figure 3. This is labeled as "combined CO2-enriched exhaust gas" in Table 1. [Table 1]

[0032] As shown in Table 1, the two exemplary membranes differ in CO2 permeability and CO2 / N2 selectivity. Specifically, the first membrane has 25 times the selectivity for CO2 compared to nitrogen (N2), while the second membrane has 100 times the selectivity. The first membrane has lower permeability than the second membrane. The combined CO2-enriched exhaust gas produced by the second membrane has higher purity compared to the first membrane (9.1 mol% CO2 compared to 8.1 mol% CO2). Therefore, the higher the CO2 permeability and CO2 selectivity, the higher the purity of the combined CO2-enriched exhaust gas, resulting in a trade-off where the first membrane (low CO2 permeability and low CO2 selectivity) recovers more CO2 (82% vs. 80%). It was also found that the second membrane, with its higher permeability and selectivity, requires less overall power compared to the first membrane.

[0033] Figures 4–7 illustrate several exemplary embodiments of a CO2 pre-concentration system 100 that uses a membrane to concentrate CO2 from another CO2 source to produce a pre-concentrated CO2 stream 112. As shown in Figure 4, an embodiment of the pre-concentration system 100 takes in air 150 having about 400 ppm of CO2, sends it through a blower or compressor 104, cools it in a cooler 106 (which may be optional depending on the output temperature of the compressed / pressurized air), and sends the resulting compressed air stream 152 through a membrane separation module 108. The membrane separation module 108 outputs a dilute CO2 gas stream 116 (i.e., a retaining stream) and a CO2-enriched gas as a permeate stream 113, which in this embodiment corresponds to the pre-concentrated CO2 stream 112. The CO2-enriched gas may have 8–20 volume% CO2, as described above, and may be sent for further processing (e.g., further concentration), storage, or utilization 118.

[0034] The pre-concentration system 100 in Figure 5 operates in the same manner as described above with respect to Figure 3, but takes in air 150 as described with respect to Figure 4. Thus, the system 100 outputs a dilute CO2 gas with less than 400 ppm of CO2 and a concentrated CO2 gas with 8-20 volume percent of CO2, which may be sent for further processing (e.g., further concentration), storage, or utilization.

[0035] More specifically, similar to the system in Figure 3, the gas split 132 of system 100 in Figure 5 splits the atmosphere 150 into a first subflow 160 and a second subflow 162. The first subflow 160 is compressed and cooled to produce an airflow 164, which is supplied to the feed side of the membrane separation module 108 to produce a dilute CO2 gas 116 and a permeate sideflow 113. The gas combiner 136 combines the second subflow 162 and the permeate sideflow 113 to produce a pre-enriched CO2 flow 112 having the above CO2 concentration. The pre-enriched CO2 flow 112 may then be sent to further CO2 enrichment or storage 118.

[0036] Figures 6 and 7 show embodiments of system 100 operating in the same manner as described above with respect to Figures 2 and 3, respectively, in which the pre-concentration system 100 takes in flue gas 170 having a moderate CO2 concentration (e.g., 8 vol% to 10 vol% CO2) along the exhaust gas flow path. Examples of flue gas with such a CO2 concentration include exhaust gas from a natural gas combustion furnace boiler or steam boiler. Thus, the combustion system 103 can correspond to a natural gas combustion furnace boiler or steam boiler, etc.

[0037] In the pre-concentration system 100 of Figure 6, the CO2-enriched flue gas 170 is compressed and cooled and supplied to the feed side of the membrane separation module 108. The permeate side flow 113 has a higher CO2 concentration than the CO2-enriched flue gas 170. As a non-limiting example, the pre-concentrated CO2 flow 112 of Figure 6 may have a CO2 concentration greater than 16 vol% CO2, e.g., 16 vol% to 30 vol% CO2. The retaining side flow, i.e., the dilute CO2 gas 116, has less than 8 vol% CO2. The CO2-enriched exhaust gas may be sent for further processing (e.g., further concentration), storage, or utilization 118.

[0038] The pre-concentration system 100 in Figure 7 receives the CO2-concentrated flue gas 170, and the gas splitter 132 divides this flow into a first sub-flow 172 and a second sub-flow 174. The first sub-flow 172 is boosted / compressed and cooled to generate a cooled flow 176, which is supplied to the feed side of the membrane separation module 108. The second sub-flow 174 is combined with the permeate side flow 113 generated by the membrane separation module 108 in the gas conjugate 136 to generate a pre-concentrated CO2 flow 112.

[0039] As a non-limiting example, the pre-enriched CO2 stream 112 in Figure 7 may have a CO2 concentration exceeding 16 vol% CO2, for example, 16 vol% to 30 vol% CO2. The retaining stream, i.e., the dilute CO2 gas 116, has less than 8 vol% CO2. The CO2-enriched exhaust gas may be sent for further processing (e.g., further enrichment), storage, or utilization 118.

[0040] The embodiments described with respect to Figures 2-7 show specific exemplary input flows (flue gas, atmosphere) and exemplary combustion systems, but this disclosure is not necessarily limited to these specific embodiments unless otherwise indicated. For example, in some embodiments, the source of flue gas used as the input flow may be an exhaust gas recirculation (EGR) system, which concentrates a certain amount, and this is then provided as an input flow to a pre-concentration system 100. In such embodiments, the pre-concentration system 100 produces a pre-concentrated CO2 flow, which is not recirculated back to the EGR system.

[0041] The specific embodiments described above are provided as examples only, and it should be understood that these embodiments may be subject to various modifications and alternative forms, and may be used in any appropriate combination. Furthermore, it should be understood that the claims are not intended to be limited to any specific form disclosed, but rather to encompass all modifications, equivalents, and alternative forms that fall within the spirit and scope of this disclosure.

Claims

1. CO in exhaust gas stream ２ A process for pre-enriching, as follows: All of the aforementioned exhaust gas flow is removed from the exhaust gas source by CO ２ To be sent to the pre-concentration system; CO ２ In the pre-concentration system, at least a portion of the exhaust gas flow is N ２ and O ２ CO ２ CO is supplied to a membrane separation module equipped with a polymer membrane that has permeation selectivity, and CO is supplied to the permeation side of the membrane separation module. ２ Concentrated exhaust gas and CO2 are released to the holding side of the membrane separation module. ２ Including the generation of a dilute gas; and Here, the exhaust gas stream has a CO of about 400 ppm ２ at a low CO level ２ concentration, and the CO ２ enriched exhaust gas has a CO of up to 20% by volume ２ in CO ２ concentration for the process.

2. The process according to claim 1, wherein supplying at least a portion of the exhaust gas flow to the membrane separation module includes supplying all of the exhaust gas flow to the membrane separation module.

3. Supplying at least a portion of the exhaust gas flow to the membrane separation module means supplying a first portion of the exhaust gas flow to the membrane separation module, wherein the first portion is the CO ２ The process according to claim 1, comprising the part of the exhaust gas flow that flows into the pre-concentration system.

4. The exhaust gas flow is divided into the first portion of the exhaust gas flow and the second portion of the exhaust gas flow, and the CO2 flow is divided into the second portion of the exhaust gas flow and the CO2 flow downstream of the membrane separation module. ２ The process according to claim 3, comprising mixing with concentrated exhaust gas to produce pre-concentrated exhaust gas.

5. The process according to claim 1, comprising: pressurizing or compressing the exhaust gas flow to generate a pressurized or compressed exhaust gas flow; and cooling the pressurized or compressed exhaust gas flow upstream of the membrane separation module.

6. The exhaust gas flow contains 3-4 volume% CO ２ Low CO2 ２ The exhaust gas is of a certain concentration, and the CO ２ Concentrated exhaust gases exceeding 8 volume percent CO ２ The process according to claim 1, comprising:

7. The exhaust gas flow contains 8-10 volume% CO ２ Having the CO ２ Concentrated exhaust gases exceeding 16 volume percent CO ２ The process according to claim 1, comprising:

8. The polymer film has a CO2 concentration of 10 to 100. ２ / N ２ The process according to claim 1, having permeability selectivity.

9. The aforementioned CO ２ The process according to claim 1, wherein the pre-concentration system has only one membrane separation step.

10. From the exhaust gas source the CO ２ The process according to claim 1, wherein the flow of the entire exhaust gas flow to the pre-enrichment system includes the flow of the entire exhaust gas flow from the gas turbine system to the pre-enrichment system.

11. From the exhaust gas source the CO ２ The process according to claim 1, wherein the flow of the entire exhaust gas stream into the pre-concentration system includes flowing all of the pre-exhaust gas from a natural gas combustion furnace boiler or steam boiler into the pre-concentration system.

12. The CO on the permeation side of the membrane separation module ２ The concentrated exhaust gas is the CO ２ CO2 levels 1.25 to 20 times higher than the exhaust gas flow received by the pre-concentration system ２ The process according to claim 1, wherein the concentration is present.

13. The aforementioned CO ２ The concentrated exhaust gas is treated with the CO ２ The CO in concentrated exhaust gas ２ The process according to claim 1, comprising providing a system for further concentrations of the

14. CO ２ It is a preliminary enrichment system: Less than 8% by volume of CO ２ CO2 ２ A channel configured to receive a source flow; Arranged along the aforementioned flow path, the CO ２ A membrane separation module configured to accept at least a portion of the supply source flow, N ２ and O ２ CO ２ The membrane separation module comprises a polymer membrane having permeability selectivity to; A vacuum source connected to the permeate side of the membrane separation module, configured to generate a pressure difference across the polymer membrane, thereby promoting gas permeation across the polymer membrane and generating a retaining side flow and a permeate side flow, wherein the permeate side flow is CO ２ Higher CO2 than the source ２ A vacuum source with concentration; The CO in the permeate side flow ２ A pre-concentration system comprising: a pre-concentration flow channel configured to carry a permeate side flow through a system configured to utilize, store, or further concentrate a substance.

15. The aforementioned CO ２ The CO2 flow path configured to receive the supply flow is an exhaust gas flow path configured to receive all of the exhaust gas generated by the combustion system, according to claim 14. ２ Pre-concentration system.

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