Systems and methods for improved exhaust gas recirculation

Abstract

An exhaust gas recirculation system includes a combustor configured to ignite a fuel mixture therein. The combustor includes an inlet, and an exhaust outlet downstream from the inlet. The exhaust gas recirculation system also includes a membrane assembly with an inlet coupled to receive at least a portion of combustion gases discharged from the combustor exhaust, and a membrane configured to facilitate separating the combustion gases into a ballast fluid stream and a treated exhaust gases stream, and a filtrate outlet for channeling treated exhaust gases towards to the combustor inlet, and a residue outlet channeling the ballast fluid stream from the membrane assembly.

Description

609418-WO-l(17851-1498)SYSTEMS AND METHODS FOR IMPROVED EXHAUST GAS RECIRCULATIONBACKGROUND

[0001] The field relates generally to gas turbine engines and, more particularly, to systems and methods for improved exhaust gas recirculation.

[0002] Exhaust gas recirculation (EGR) is widely used in industrial, power generation, and transportation systems. A conventional EGR system includes one or more combustors that ignite a fuel-air mixture to generate exhaust gases used to power a turbine engine or a diesel engine. Within known EGR systems, a portion of the exhaust gases are recirculated and reintroduced to the combustors. The recirculation process reduces the overall working temperature and reduces the amount of potential harmful emissions emitted during combustion.

[0003] Exhaust gases may include various combustion by-products, such as nitrogen oxides (NOx), carbon oxides (COx), water, and / or unburned hydrocarbons. COx and NOx are considered air pollutants that are harmful to the environment. Decreased working / operating temperatures and lower available oxygen (O2) levels within the combustors can reduce the formation of NOx and increase the production of COx. Recent efforts to further reduce such emissions include using carbon capture systems to capture and store COx in such a way that facilitates minimizing an adverse effect to the atmosphere.

[0004] The amount of COx in the exhaust gases can be controlled by varying the ratio of exhaust gases that are recirculated back to the combustor. Increasing the ratio of COx in the exhaust gases generally benefits the capture of the COx, but the benefits of the increased recirculation may be limited by the amount of oxygen available in the combustion mixture to support combustion. Within at least some known EGR systems, additional air is supplied to the combustors to increase the amount of oxygen in the combustion mixture. However, such processes may ultimately decrease the efficiency of overall power generation system.609418-WO-l(17851-1498)

[0005] Accordingly, there exist a need for systems and methods that facilitate increasing the O2 ratio of the combustion mixture in a cost-effective manner to enable the ratio of exhaust gases available to be recirculated in EGR systems to be increased to lower the level of emissions.SUMMARY

[0006] In one aspect, an exhaust gas recirculation system also includes a combustor configured to ignite a fuel mixture therein. The combustor may include an inlet, and an exhaust outlet downstream from the inlet. The system also includes a membrane assembly may include an inlet coupled to receive at least a portion of combustion gases discharged from the combustor exhaust, and a membrane configured to facilitate separating the combustion gases into a ballast fluid stream and a treated exhaust gases stream, and a filtrate outlet for recirculating treated exhaust gases into the combustor inlet, and a residue outlet for channeling the ballast fluid stream from the membrane assembly.

[0007] In another aspect, the power generation system also includes a rotary machine may include a compressor, and a turbine coupled to the compressor and configured to produce exhaust gases. The system also includes an exhaust gas recirculation system configured to recirculate exhaust gases discharged from the turbine towards the compressor, where the exhaust gas recirculation system may include a membrane assembly that facilitates removing a ballast fluid from the exhaust gases being recirculated, where the membrane assembly may include an inlet oriented to receive at least a portion of exhaust gases discharged from the turbine, and a membrane configured to facilitate separating the exhaust gases discharged from the turbine into a ballast fluid stream and a treated exhaust gases stream, and at least a first outlet for channeling the treated exhaust gases stream to the turbine, and at least a second outlet for channeling the ballast fluid stream from the membrane.

[0008] In another aspect, a method of operating a power generation system to facilitate improving emissions of the power generation system. The method of operating also includes recirculating at least a portion of exhaust gases discharged from a power generation system towards a combustor coupled within the power generation system; channeling the exhaust gases being recirculated into a membrane assembly to facilitate removing a ballast fluid from the exhaust gases to produce a treated exhaust gases stream; directing the ballast609418-WO-l(17851-1498)fluid from the membrane assembly to an external process; and directing a treated exhaust gas stream from the membrane assembly to the combustor.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein.

[0010] FIG. 1 is a schematic illustration of an exemplary exhaust gas recirculation (EGR) system including an exemplary membrane assembly;

[0011] FIG. 2 is a schematic illustration of an alternative EGR system including the exemplary membrane assembly of FIG. 1 and coupled to a power generation system;

[0012] FIG. 3 is a flow chart of an exemplary method of operating a power generation system including an EGR system.

[0013] Unless otherwise indicated, the drawings provided herein are meant to illustrate features of embodiments of the disclosure. These features are believed to be applicable in a wide variety of systems comprising one or more embodiments of the disclosure. As such, the drawings are not meant to include all conventional features known by those of ordinary skill in the art to be required for the practice of the embodiments disclosed herein.DETAILED DESCRIPTION

[0014] The embodiments described herein relate to systems and methods for operating a power generation system including an exhaust gas recirculation system (EGR). More specifically, at least some of the systems and methods described herein describe methods and systems that include a membrane that facilitates separating and removing ballast fluid from exhaust gases being recirculated in an EGR loop. More specifically, in the exemplary embodiment, an EGR system separates and removes ballast fluid from exhaust gases being recirculated to a power generation system that includes a combustor. The combustor ignites a fuel mixture therein to create combustion gases that are channeled609418-WO-l(17851-1498)downstream towards a membrane assembly. The membrane assembly receives at least a portion of the combustion gases discharged from the combustor, and a membrane that facilitates separating the combustion gases into a ballast fluid stream and a treated exhaust gases stream. A filtrate outlet channels treated exhaust gases towards the combustor, and a residue outlet channels the ballast fluid stream away from the membrane assembly and out of the EGR loop.

[0015] In an exemplary embodiment, the membrane has a higher selectivity for oxygen and carbon dioxide than for nitrogen. More specifically, in the exemplary embodiment, the membrane may include a bundle of selectively permeable hollow fibers that enable nitrogen to be separated from oxygen and carbon dioxide via selective permeation as the exhaust gases flow through the membrane wall. With this configuration the filtrate outlet is downstream from the membrane for discharging the oxygen and carbon dioxide, and the residue outlet is upstream from the membrane for channeling the nitrogen from the membrane assembly. The exemplary EGR system described herein may also include a compressor upstream from the membrane assembly that increases the pressure of the combustion gases entering the membrane assembly. In alternative embodiments, depending on the demands of the required EGR rate and / or other demands of the application, the system described herein may also include a vacuum pump and / or a combined configuration, such as, but not limited to a low and a high pressure EGR configuration. The increased pressure creates a pressure gradient across that membrane that can be selectively tuned to satisfy the requirements of the specific membrane selected and to facilitate achieving a desired permutation rate and / or selectivity quality, thus increasing the overall efficiency of the EGR system. The exemplary EGR system may include a flow divider that is downstream from the combustor exhaust to enable the exhaust gases to be variably split into at least two streams. The composition of each stream exiting the flow divider is generally homogonous, and the proportion (i.e., the volumetric proportion) of each stream exiting the flow divider can be statically or dynamically controlled. An exemplary controller used with the flow divider can include manually or automatically operated valves, control valves, and / or flow regulators.

[0016] The portion of the exhaust stream that is not being channeled to the membrane assembly is channeled to an external process. For example, the external process can be any process that is intended to use, refine, and / or store the combustor exhaust gases.609418-WO-l(17851-1498)In one embodiment, the combustor exhaust gases are channeled to a carbon capture plant that facilitates removing carbon from the stream for storage before releasing the treated gases into the atmosphere. In other embodiments the external process can also be configured to use, refine, or store the combustor exhaust gases.

[0017] The exemplary embodiments described herein facilitate removing ballast gases in an EGR system, while overcoming several technical challenges associated with the same. Removing ballast gases from an EGR system enables a greater ratio of exhaust gases to be recirculated in the EGR system. Recirculating the gases as described herein facilitates decreasing the production of potentially environmentally harmful combustion by-products, such as nitrogen oxides (NOx), while increasing the density of carbon oxides, such as carbon monoxide (CO) and carbon dioxide (CO2), in the combustion gas stream. The increased density of carbon oxides in the combustion gas stream are still considered an atmospheric pollutant, but such pollutants can be readily processed in an environmentally responsible way, such as through a carbon capture system. The ratio of combustion gases that can be recirculated may be limited by the amount of available oxygen ratio of the combustion mixture within the combustor. In the exemplary embodiments, the inclusion of the membrane within the EGR system, facilitates increasing the oxygen ratio in the combustion gases by reducing the amount of ballast fluids, such as nitrogen and water, that do not contribute to the combustion reaction in a positive manner.

[0018] In the following specification and the claims, reference will be made to a number of terns, which shall be defined to have the following meanings.

[0019] The singular forms “a,” “an,” “the,” and “said” include plural references unless the context clearly dictates otherwise.

[0020] The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0021] “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.609418-WO-l(17851-1498)

[0022] References to “one embodiment’’ or “an embodiment” are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, although specific features of various embodiments described herein may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the present disclosure, any feature of a drawing and / or embodiment described herein may be referenced and / or claimed in combination with any feature of any other drawing and / or embodiment described herein. Furthermore, unless explicitly stated to the contrary, embodiments “including” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property.

[0023] As used herein, the term “real-time” refers to either the time of occurrence of the associated events, the time of measurement and collection of predetermined data, the time to process the data, or the time of a system response to the events and the environment. In the embodiments described herein, these activities and events occur substantially instantaneously.

[0024] As used herein, the terms “processor” and “computer” and related terms, e.g., “processing device,” “computing device,” and “controller” are not limited to just those integrated circuits referred to in the art as a computer, but instead refer broadly to a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and / or other programmable circuits, and such terms are used interchangeably herein. In the embodiments described herein, memory may include, but is not limited to, a computer-readable medium, such as a random-access memory (RAM), and a computer-readable non-volatile medium, such as flash memory. Alternatively, a floppy disk, a compact disc - read only memory (CD-ROM), a magneto-optical disk (MOD), and / or a digital versatile disc (DVD) may also be used. Also, in the embodiments described herein, additional input channels may be, but are not limited to only being, computer peripherals associated with an operator interface such as a mouse and a keyboard. Alternatively, other computer peripherals may also be used such as, but not limited to, a scanner. Furthermore, in the embodiments described herein, additional output channels may include, but are not limited to only being, an operator interface monitor.609418-WO-l(17851-1498)

[0025] Unless otherwise indicated, approximating language, such as “generally,” “substantially,” and “about,” as used herein indicates that the term so modified may apply to only an approximate degree, as would be recognized by one of ordinary skill in the art, rather than to an absolute or perfect degree. Accordingly, a value modified by a term or terms such as “about,” “approximately,” and “substantially” is not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Additionally, unless otherwise indicated, the terms “first,” “second,” etc. are used herein merely as labels, and are not intended to impose ordinal, positional, or hierarchical requirements on the items to which these terms refer. Moreover, reference to, for example, a “second” item does not require or preclude the existence of, for example, a “first” or lower-numbered item or a “third” or higher-numbered item.

[0026] Referring now to the drawings, FIG. 1 is a schematic illustration of an exemplary exhaust gas recirculation (EGR) system 100. In the exemplary embodiment, the EGR system 100 includes a rotary machine assembly 30 that includes a gas turbine engine including an inlet 22 and an exhaust 24 that is downstream from the inlet 22. The EGR system 100 also includes a membrane assembly 102. In the exemplary embodiment, the membrane assembly 102 includes an inlet 104, a membrane 106, a filtrate outlet 108, and a residue outlet 110. The membrane assembly inlet 104 is oriented to receive at least a portion of combustion gases discharged from the combustor exhaust 24 via the combustion gases stream 26. More specifically, in the exemplary embodiment, membrane 106 facilitates separating combustion gases flowing therethrough into a ballast fluid stream 114, that is channeled away from the membrane assembly 102 via the residue outlet 110, and a treated exhaust gas stream 112 that is channeled away from the membrane assembly 102 via the filtrate outlet 108. The treated exhaust gas stream 112 is then recirculated back to the rotary machine assembly 30

[0027] Although the exemplary embodiment includes rotary machine assembly 30, alternatively, the EGR system 100 may be coupled to any other apparatus that is used to convert chemical energy to another form through the means of combustion, wherein the apparatus includes an inlet for receiving a combustion mixture, and an exhaust for discharging the combustion gases created within. For example, the EGR system 100609418-WO-l(17851-1498)described herein may be used with a turbine assembly, a power generation system, an internal combustion engine, and / or a furnace. Moreover, the EGR system 100 described herein may be used with any other apparatus or system that operates using any chemical fuel capable of burning in the presence of an oxygen mixture such as, but not limited to only being, natural gas, propane, kerosene, diesel, petrol, charcoal, coal, wood, hydrogen, ammonia, and / or combinations thereof.

[0028] The membrane assembly 102 may be oriented in any orientation that enables the inlet 104 to receive a combustion gas stream 26 and that enables a treated exhaust gases stream 112 to be discharged via the filtrate outlet 108 and a ballast fluid stream 114 to be discharged via the residue outlet 110. In the exemplary embodiment, the membrane 106 facilitates separating the combustion gases via selective permeability into a ballast fluid stream 114 and a treated exhaust gases stream 112. For example, in one embodiment, the membrane is fabricated from, but is not limited to only being fabricated from, hollow fibers, polymers, crystalline porous membrane, mixed matrix membrane, organic material, inorganic material, and other any other known material, combination of known materials, and / or any other type or construction of materials that enables the membrane 106 and the membrane assembly 102 to function as described herein.

[0029] FIG. 2 is a schematic illustration of an alternative exhaust gas recirculation (EGR) system 200 that includes the membrane assembly 102. In the exemplary embodiment, EGR system 200 is coupled to a power generation system 202 that includes a rotary machine assembly 30. In the exemplary embodiment, rotary machine assembly 30 includes a gas turbine engine. The rotary machine assembly 30 includes a compressor 32, one or more combustors 20, and a turbine 34 coupled together in a serial flow relationship. More specifically, in the exemplary embodiment, an axial shaft 38 couples the machine assembly components together and rotatably couples the compressor 32 to the turbine 34. The rotary machine assembly 30 may be coupled to a generator 36 to produce electrical power. While the exemplary rotary machine assembly 30 includes a combustor 20, it should be noted that the EGR system 200 is not limited to only being used with any particular type of rotary machine. Any suitable rotary machine assembly 30 operable producing combustion gases, in any suitable configuration may be used with the EGR system 200.609418-WO-l(17851-1498)

[0030] In some embodiments EGR system 200 includes a compressor 50 that is upstream from the membrane assembly 102. The compressor 50 facilitates increasing the pressure of the combustion gases stream 26 prior to the stream 26 being channeled into the inlet 104 of the membrane assembly 102. Increasing a pressure gradient across the membrane 106 facilitates improving the separation of the combustion gases 26. In the exemplary embodiment, the magnitude of the pressure gradient can be tuned to meet desired requirements of the specific membrane 106 selected and to enable a desired permutation rate and selectivity quality to be achieved. In some embodiments, the system 200 may also include a vacuum pump (not shown) used to facilitate creating the pressure gradient which will induce a vacuum force on stream 110. In alternative embodiments, system 200 may includes a compressor and / or a vacuum pump, and / or any other device that can create the pressure gradient described herein and that will enable system 200 to function as described herein.

[0031] In some embodiments the EGR system 200 includes an air inlet 80 that can be upstream or downstream from the membrane assembly 102. The air inlet 80 enables an oxygenated mixture to be introduced which increases combustion efficiency.

[0032] In some embodiments the power generation system 202 used with either EGR system 100 or 200 includes a heat recovery steam generator 40 that is upstream from the membrane assembly 102.

[0033] In some embodiments the EGR system 100 or 200 includes a catalytic converter 60 that is upstream from the membrane assembly 102. This catalytic converter 60 can be configured to convert nitrogen oxides to nitrogen and carbon oxides, and carbon monoxide to carbon dioxide. These newly converted gases are then channeled to the membrane assembly inlet 104 to be separated by the membrane 106.

[0034] In the exemplary embodiments the EGR system includes a flow divider 120 that is upstream from the membrane assembly 102. In the exemplary embodiment, the flow divider 120 is oriented to split the stream of combustion gases 26 into at least two streams. At least one of the streams 206 is channeled towards the membrane assembly inlet 104 and at least one of the exiting streams 204 is channeled to an external process 70. The composition of each stream 206 and 204 exiting the flow divider 120 is generally609418-WO-l(17851-1498)homogonous. The flow divider 120 can variably selected to ensure a desired proportion or division of the exhaust gas stream via a fixed or an adjustable means. For example, the flow divider 120 may include channel restrictions, flow regulators, and / or a system of valves.

[0035] In some embodiments the proportion of each stream 206 and 204 exiting the flow divider can be adjusted by a controller 130 that includes a processor. This controller 130 may continuously monitor the EGR system 100 to determine the proportion of each stream 206 and 204 exiting the flow divider 120 based on the combustion temperature, combustion gas composition, and / or combustion gas flow rate, for example. _ In the exemplary embodiment, the controller 130 can also selectively control the rotational speed of the compressor 50 and / or selectively change the pressure discharge from the compressor 50. Moreover, the controller 130 can also control the separation efficiency of the membrane 106 and / or the oxygen O2 content in stream 108 based on at least the EGR ratio.

[0036] FIG. 3 is a flow chart of an exemplary method 300 that may be implemented to operate a power generation system, such as a system including an exhaust gas recirculation (EGR) system, such as power generation system 202 (shown in FIG. 2). In the exemplary embodiment, the method 300 includes recirculating 302 at least a portion of exhaust gases discharged from a power generation system towards a combustor coupled within the power generation system. The method 300 also includes channeling 304 the exhaust gases being recirculated into a membrane assembly 102 to facilitate removing a ballast fluid from the exhaust gases to produce a treated exhaust gases stream. Additionally, the method 300 includes directing 306 the ballast fluid 114 from the membrane assembly to an external process, and directing 308 a treated exhaust gas stream 26 from the membrane assembly to the combustor.

[0037] In some embodiments, the method 300 also includes compressing the exhaust gases prior to channeling 304 the exhaust gases being recirculated into a membrane assembly to facilitate removing a ballast fluid from the exhaust gases to produce a treated exhaust gases stream. More specifically, compressing the exhaust gases as such, facilitates increasing a pressure gradient across the membrane. In some of such embodiments, the method 300 may also include variably tuning the pressure gradient to enable desired outputs from the specific membrane selected, and to enable desired permutation rate and / or selectivity quality to be achieved. In other embodiments, the method 300 may include609418-WO-l(17851-1498)dividing the exhaust gases prior to channeling 304 the exhaust gases being recirculated into a membrane assembly to produce a treated exhaust gases stream. The divided flow can then be channeled to an external process, such as a carbon capture plant.

[0038] In each embodiment, the inclusion of a membrane assembly within an EGR loop facilitates the removal of a ballast fluid and a facilitates increasing the density of carbon oxides in the exhaust gas stream. A greater partial pressure of carbon oxides in the exhaust gas stream is a more advantageous emissions profile for many situations including when used in combination with carbon capture. A greater density of carbon oxides in the exhaust gas stream can facilitate a more efficient carbon capture, and thus enables the carbon capture unit to have a smaller footprint, be less expensive to operate, and / or operate more effectively. This bodes true for many post-processing or uses of a carbon rich exhaust gas stream.

[0039] Further aspects of the present disclosure are provided by the subject matter of the following clauses:

[0040] An exhaust gas recirculation system includes a combustor configured to ignite a fuel mixture therein, wherein the combustor includes an inlet, and an exhaust outlet downstream from the inlet, and a membrane assembly that includes an inlet coupled to receive at least a portion of combustion gases discharged from the combustor exhaust. The membrane assembly also includes a membrane configured to facilitate separating the combustion gases into a ballast fluid stream and a treated exhaust gases stream, a filtrate outlet for recirculating treated exhaust gases into the combustor inlet, and a residue outlet for channeling the ballast fluid stream from the membrane assembly.

[0041] The exhaust gas recirculation system in accordance with any of the preceding clauses, wherein the membrane has a higher selectivity for oxygen and carbon dioxide than for nitrogen, and wherein the filtrate outlet is downstream from the membrane and the residue outlet is upstream from the membrane.

[0042] The exhaust gas recirculation system in accordance with any of the preceding clauses wherein a compressor is upstream from the membrane assembly to facilitate increasing the pressure of combustion gases discharged from the combustor.

[0043] The exhaust gas recirculation system in accordance with any of the preceding clauses, further including an air inlet for supplying an oxygen mixture to the combustor.609418-WO-l(17851-1498)

[0044] The exhaust gas recirculation system in accordance with any of the preceding clauses, wherein the membrane assembly inlet is coupled to a heat recovery' steam generator.

[0045] The exhaust gas recirculation system in accordance with any of the preceding clauses, further including a catalytic converter upstream from the membrane assembly for processing combustion gases discharged from the combustor.

[0046] The exhaust gas recirculation system in accordance with any of the preceding clauses, further including a flow divider downstream from the combustor exhaust outlet, wherein the flow divider is oriented to split the exhaust gases into a first portion channeled to the membrane assembly and into a second portion channeled to an external process that uses the gases.

[0047] The exhaust gas recirculation system in accordance with any of the preceding clauses, further including a controller configured to selectively control at least one of the flow of combustion gases discharged from the combustor exhaust outlet based at least on a detected oxygen ratio of the treated exhaust gases, compressor pressure discharge, compressor rotational speed, and membrane separation efficiency

[0048] The exhaust gas recirculation system in accordance with any of the preceding clauses, wherein the external process is a carbon capture unit that facilitates extracting carbon dioxide from the combustion gases discharged from the combustor exhaust outlet.

[0049] A power generation system includes a rotary machine including a compressor, and a turbine that is coupled to the compressor and that produces exhaust gases. The power generation system also includes an exhaust gas recirculation system configured to recirculate exhaust gases discharged from the turbine towards the compressor, wherein the exhaust gas recirculation system includes a membrane assembly that facilitates removing a ballast fluid from the exhaust gases being recirculated. The membrane assembly includes an inlet oriented to receive at least a portion of exhaust gases discharged from the turbine, and a membrane configured to facilitate separating the exhaust gases discharged from the turbine into a ballast fluid stream and into a treated exhaust gases stream. The membrane assembly also includes at least a first outlet for channeling the treated exhaust gases stream to the turbine, and at least a second outlet for channeling the ballast fluid stream from the membrane.609418-WO-l(17851-1498)

[0050] The power generation system in accordance with any of the preceding clauses, further including a compressor upstream from the membrane assembly operable to facilitate increasing the pressure of the exhaust gases discharged from the turbine.

[0051] The power generation system in accordance with any of the preceding clauses, further including a heat recovery steam generator coupled to the rotary machine.

[0052] The power generation system in accordance with any of the preceding clauses, wherein the membrane facilitates separating the exhaust gases discharged from the turbine into a ballast fluid stream including nitrogen and water, and into a treated exhaust gases stream.

[0053] The power generation system in accordance with any of the preceding clauses, further including a flow divider for channeling a first portion of the exhaust gases discharged from the turbine to an external process, and for channeling a second portion of the exhaust gases discharged from the turbine to the membrane assembly.

[0054] The power generation system in accordance with any of the preceding clauses, further including a controller configured to selectively divide the exhaust gases discharged from the turbine based on a detected oxygen ratio of the treated exhaust gases stream.

[0055] The power generation system in accordance with any of the preceding clauses, wherein the external process is a carbon capture unit that facilitates extracting carbon dioxide from the exhaust gases.

[0056] A method of operating a power generation system facilitates improving emissions of the power generation system. The method includes recirculating at least a portion of exhaust gases discharged from a power generation system towards a combustor coupled within the power generation system, channeling the exhaust gases being recirculated into a membrane assembly to facilitate removing a ballast fluid from the exhaust gases to produce a treated exhaust gases stream, and directing the ballast fluid from the membrane assembly to an external process. The method also includes directing a treated exhaust gas stream from the membrane assembly to the combustor.

[0057] The method of operating a power generation system in accordance with any of the preceding clauses, further including pressurizing the exhaust gases discharged from the power generation system prior to channeling the pressurized exhaust gases into the membrane assembly.609418-WO-l(17851-1498)

[0058] The method of operating a power generation system in accordance with any of the preceding clauses, further including directing the exhaust gases generated in the power generation system to a flow divider upstream from the membrane assembly, wherein the flow divider diverts a portion of the exhaust gases to an external process.

[0059] The method of operating a power generation system in accordance with any of the preceding clauses, further including extracting carbon dioxide from the exhaust gases discharged from the power generation system using the external process.

[0060] The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the disclosure. Modifications, which fall within the scope of the present disclosure, will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims. The systems and methods described herein are not limited to the specific embodiments described herein, but rather components of the various systems may be utilized independently and separately from other systems and components described herein. For example, the membrane assembly can be implemented and utilized in connection with any application where exhaust gas recirculation is desired to be used with any combustor.

[0061] The methods and systems described herein are not limited to the specific embodiments described herein. For example, components of each system and / or steps of each method may be utilized independently and separately from other components and / or steps described herein. For example, the method and systems may also be used in combination with other combustion systems, and are not limited to practice only with the power generation system as described herein. Rather, the exemplary embodiment can be implemented and utilized in connection with many other combustion applications.

[0062] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims

609418-WO-l(17851-1498)WHAT IS CLAIMED IS:

1. An exhaust gas recirculation system comprising:a combustor configured to ignite a fuel mixture therein, the combustor comprising;an inlet; andan exhaust outlet downstream from the inlet; anda membrane assembly comprising:an inlet coupled to receive at least a portion of combustion gases discharged from the combustor exhaust; anda membrane configured to facilitate separating the combustion gases into a ballast fluid stream and a treated exhaust gases stream; anda filtrate outlet for recirculating treated exhaust gases into the combustor inlet; anda residue outlet for channeling the ballast fluid stream from the membrane assembly.

2. The exhaust gas recirculation system of claim 1, wherein the membrane has a higher selectivity for oxygen and carbon dioxide than for nitrogen, and wherein the filtrate outlet is downstream from the membrane and the residue outlet is upstream from the membrane.

3. The exhaust gas recirculation system of claim 1 further comprising at least one of a vacuum pump and a compressor upstream from the membrane assembly to facilitate increasing pressure of combustion gases discharged from the combustor.

4. The exhaust gas recirculation system of claim 1 further comprising an air inlet for supplying an oxygen mixture to the combustor.609418-WO-l(17851-1498)5. The exhaust gas recirculation system of claim 1, wherein the membrane assembly inlet is coupled to a heat recovery steam generator.

6. The exhaust gas recirculation system of claim 1 further comprising a catalytic converter upstream from the membrane assembly for processing combustion gases discharged from the combustor.

7. The exhaust gas recirculation system of claim 1, further comprising a flow divider downstream from the combustor exhaust outlet, the flow divider oriented to split the exhaust gases into a first portion channeled to the membrane assembly and a second portion channeled to an external process that uses the gases.

8. The exhaust gas recirculation system of claim 7, further comprising a controller configured to selectively control at least one of the flow of combustion gases discharged from the combustor exhaust outlet based at least on a detected oxygen ratio of the treated exhaust gases, compressor rotation speed, compressor discharge pressure, and vacuum separation efficiency based on at least EGR ratio 9. The exhaust gas recirculation system of claim 7, wherein the external process is a carbon capture unit that facilitates extracting carbon dioxide from the combustion gases discharged from the combustor exhaust outlet.

10. A power generation system comprising:a rotary machine comprising:a compressor; anda turbine coupled to the compressor and configured to produce exhaust gases; andan exhaust gas recirculation system configured to recirculate exhaust gases discharged from the turbine towards the compressor, wherein the exhaust gas recirculation system comprises a membrane assembly that facilitates removing a ballast fluid from the exhaust gases being recirculated, wherein the membrane assembly comprises:609418-WO-l(17851-1498)an inlet oriented to receive at least a portion of exhaust gases discharged from the turbine; anda membrane configured to facilitate separating the exhaust gases discharged from the turbine into a ballast fluid stream and a treated exhaust gases stream; andat least a first outlet for channeling the treated exhaust gases stream to the turbine; andat least a second outlet for channeling the ballast fluid stream from the membrane.

11. The power generation system of claim 10 further comprising a compressor upstream from the membrane assembly operable to facilitate increasing pressure of the exhaust gases discharged from the turbine.

12. The power generation system of claim 10, further comprising a heat recovery steam generator coupled to the rotary machine.

13. The power generation system of claim 10, wherein the membrane facilitates separating the exhaust gases discharged from the turbine into a ballast fluid stream comprising nitrogen and water, and into a treated exhaust gases stream.

14. The power generation system of claim 10, further comprising a flow divider for channeling a first portion of the exhaust gases discharged from the turbine to an external process, and for channeling a second portion of the exhaust gases discharged from the turbine to the membrane assembly.

15. The power generation system of claim 14, further comprising a controller configured to selectively divide the exhaust gases discharged from the turbine based on a detected oxygen ratio of the treated exhaust gases stream.

16. The power generation system of claim 14, wherein the external process is a carbon capture unit that facilitates extracting carbon dioxide from the exhaust gases.609418-WO-l(17851-1498)17. A method of operating a power generation system to facilitate improving emissions of the power generation system, the method comprising:recirculating at least a portion of exhaust gases discharged from a power generation system towards a combustor coupled within the power generation system;channeling the exhaust gases being recirculated into a membrane assembly to facilitate removing a ballast fluid from the exhaust gases to produce a treated exhaust gases stream;directing the ballast fluid from the membrane assembly to an external process; anddirecting a treated exhaust gas stream from the membrane assembly to the combustor.

18. The method of operating a power generation system of claim 17, further comprising pressurizing the exhaust gases discharged from the power generation system prior to channeling the pressurized exhaust gases into the membrane assembly.

19. The method of operating a power generation system of claim 17, further comprising directing the exhaust gases generated in the power generation system to a flow divider upstream from the membrane assembly, wherein the flow divider diverts a portion of the exhaust gases to an external process.

20. The method of operating a power generation system of claim 19, further comprising extracting carbon dioxide from the exhaust gases discharged from the power generation system using the external process.

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