Combustion system with fuel cell and carbon capture system

Abstract

A combustion system is provided. The combustion system includes a top cycle and a bottom cycle, the top cycle generating an exhaust gas stream. The combustion system also includes a fuel cell including an anode side, a cathode side, and an electrolyte. The cathode side receives an exhaust stream from the top cycle via a cathode inlet line. The cathode side removes a first portion of the contaminant from the exhaust gas. The combustion system also includes a heat recovery steam generator (HRSG) that receives exhaust gas from the cathode side via a cathode outlet line. The HRSG produces a steam stream for use in the bottom cycle. The carbon capture system is fluidly coupled to the HRSG via an HRSG outlet line. The carbon capture system removes a second portion of the contaminant from the exhaust gas.

Description

Technical Field

[0001] The present disclosure generally relates to a combustion system having a fuel cell and one or more additional carbon capture systems. In particular, the present disclosure relates to a combustion system having a fuel cell and a carbon capture system. Background Art

[0002] A gas turbine power plant, such as a combined cycle power plant (CCPP) or a combined cycle system (CCS), typically includes a gas turbine having a compressor section, a combustion section, a turbine section; a heat recovery steam generator (HRSG) disposed downstream of the turbine; and at least one steam turbine in fluid communication with the HRSG. During operation, air enters the compressor via an inlet system and is progressively compressed as it is directed toward the compressor discharge or diffuser housing of a combustor that at least partially surrounds the combustion section. At least a portion of the compressed air is mixed with fuel and combusted within a combustion chamber defined within the combustor, thereby generating high-temperature, high-pressure combustion gases.

[0003] Combustion gases are directed from the combustor through the turbine along a hot gas path, where they gradually expand as they flow through alternating stages of stationary blades and rotatable turbine blades coupled to the rotor shaft. Energy is transferred from the combustion gases to the turbine blades, causing the rotor shaft to rotate. The rotational energy of the rotor shaft can be converted into electrical energy via a generator. The combustion gases leave the turbine as exhaust gas, and this exhaust gas enters the HRSG. The heat energy from the exhaust gas is transferred to water flowing through one or more heat exchangers in the HRSG, thereby producing superheated or supercritical steam. The superheated steam is then directed to a steam turbine, which can be used to generate additional electricity, thereby increasing the efficiency of the entire power plant.

[0004] Turbine combustion systems typically burn hydrocarbon fuels and produce air polluting emissions such as nitrogen oxides (NOx), carbon monoxide (CO), and carbon dioxide (CO2). To reduce these emissions, carbon capture systems are used to capture CO2 and other air polluting gases before the turbine gases are released into the atmosphere. However, known carbon capture systems are only partially effective and require significant amounts of energy.

[0005] Therefore, an improved combined cycle power plant with a carbon capture system that removes pollutants from emissions without requiring large amounts of electricity is desirable and would be appreciated in the art. Summary of the Invention

[0006] Aspects and advantages of combined cycle systems and methods according to the present disclosure will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the technology.

[0007] According to one embodiment, a combustion system is provided. The combustion system includes a topping cycle and a bottoming cycle, the topping cycle generating an exhaust gas stream. The combustion system also includes a fuel cell comprising an anode side, a cathode side, and an electrolyte. The cathode side receives the exhaust gas stream from the topping cycle via a cathode inlet line. The cathode side removes a first portion of pollutants from the exhaust gas. The combustion system also includes a heat recovery steam generator (HRSG) that receives the exhaust gas from the cathode side via a cathode outlet line. The HRSG generates a steam stream for use in the bottoming cycle. A carbon capture system is fluidly coupled to the HRSG via the HRSG outlet line. The carbon capture system removes a second portion of the pollutants from the exhaust gas.

[0008] According to another embodiment, a method for removing pollutants from a combustion system is provided. The method includes operating a topping cycle of the combustion system to generate a first power output and an exhaust gas. The method also includes passing the exhaust gas through the cathode side of a fuel cell, thereby removing a first portion of the pollutants from the exhaust gas. The method also includes providing the exhaust gas from an outlet on the cathode side to a carbon capture system. A second portion of the pollutants is removed from the exhaust gas by the carbon capture system.

[0009] According to another embodiment, a combustion system is provided. The combustion system includes a topping cycle and a bottoming cycle, the topping cycle generating an exhaust gas stream. The combustion system also includes a heat recovery steam generator (HRSG) that receives the exhaust gas from the topping cycle. The HRSG generates a steam stream for use in the bottoming cycle. The fuel cell includes an anode side, a cathode side, and an electrolyte. The cathode side receives the exhaust gas stream from the HRSG via a cathode inlet line. The cathode side removes a first portion of pollutants from the exhaust gas. A carbon capture system is fluidly coupled to the cathode side via a cathode outlet line. The carbon capture system removes a second portion of the pollutants from the exhaust gas.

[0010] According to another embodiment, a combustion system is provided. The combustion system includes a gas turbine having a compressor section, a combustion section, and a turbine section. The turbine section generates exhaust gas. A fuel cell includes an anode side, a cathode side, and an electrolyte. The cathode side receives the exhaust gas from the turbine section via an exhaust gas outlet line. The cathode side removes a first portion of pollutants from the exhaust gas. A carbon capture system is fluidly coupled to the fuel cell for removing a second portion of the pollutants from the exhaust gas. An exhaust gas recirculation line extends from the exhaust gas outlet line to the compressor section.

[0011] These and other features, aspects and advantages of the combustion system and method of the present invention will become better understood with reference to the following description and appended claims.The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with the description, serve to explain the principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] This specification, with reference to the accompanying drawings, sets forth a complete and enabling disclosure of the combustion system and method of the present invention, including the best mode of making and using the system and method of the present invention, to one of ordinary skill in the art, wherein:

[0013] Figure 1 is a schematic diagram of a combustion system according to an embodiment of the present disclosure;

[0014] Figure 2 is a schematic diagram of a combustion system according to an embodiment of the present disclosure; and

[0015] Figure 3 is a flow chart of a method of removing pollutants in a combustion system according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0016] Reference will now be made in detail to embodiments of the combustion systems and methods of the present invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the present invention, and not as a limitation thereto. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit of the present invention as protected by the claims. For example, features illustrated or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, the present disclosure is intended to cover such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0017] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations. Additionally, all embodiments described herein should be considered exemplary unless specifically stated otherwise.

[0018] The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar components of the invention. As used herein, the terms "first," "second," and "third" are used interchangeably to distinguish one component from another and are not intended to indicate the position or importance of each component.

[0019] The term "fluid" may be a gas or a liquid. The term "fluid communication" means that a fluid is able to connect between designated areas.

[0020] As used herein, the terms "upstream" (or "upward") and "downstream" (or "downward") refer to relative directions relative to the flow of a fluid in a fluid pathway. For example, "upstream" refers to the direction from which the fluid is flowing, and "downstream" refers to the direction toward which the fluid is flowing. However, the terms "upstream" and "downstream" as used herein may also refer to currents. The term "radially" refers to a relative direction that is substantially perpendicular to an axial centerline of a particular component, the term "axially" refers to a relative direction that is substantially parallel and / or coaxially aligned with an axial centerline of a particular component, and the term "circumferentially" refers to a relative direction that extends around the axial centerline of a particular component.

[0021] Terms with approximate meanings, such as "about," "approximately," "substantially," and "substantially," are not limited to the precise values specified. In at least some cases, approximate language may correspond to the precision of an instrument used to measure a value, or the precision of a method or machine used to construct or manufacture a component and / or system. For example, approximate language may refer to within a tolerance of 1%, 2%, 4%, 5%, 10%, 15%, or 20% of an individual value, a range of values, and / or an end value of a range of values. When used in the context of an angle or direction, such terms include within ten degrees greater than or less than the angle or direction. For example, "substantially vertical" includes directions within ten degrees of vertical in any direction (e.g., clockwise or counterclockwise).

[0022] Unless otherwise stated herein, the terms "coupled," "fixed," "attached to," and the like refer to direct coupling, fixing, or attachment, as well as indirect coupling, fixing, or attachment through one or more intermediate components or features. As used herein, the terms "comprises," "includes," "has," or any other variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, article, or apparatus that includes a list of features is not necessarily limited to only those features but may include other features not expressly listed or inherent to such process, method, article, or apparatus. Furthermore, unless expressly stated to the contrary, "or" refers to an inclusive or and not an exclusive or. For example, condition A or B is satisfied by any one of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); and both A and B are true (or exist).

[0023] Here and throughout the specification and claims, unless context or language indicates otherwise, range limitations are combined and interchangeable, and such ranges are identified and include all sub-ranges contained therein. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other.

[0024] As used herein, the term "line" may refer to a fluid-carrying conduit, such as a pipe, hose, tubing, conduit, or other fluid-carrying conduit.

[0025] Now referring to the accompanying drawings, Figure 1 and Figure 2 Each shows a schematic diagram of an embodiment of a combustion system or combined cycle system 100, which includes a topping cycle 102 and a bottoming cycle 104. In the topping cycle 102, fuel is burned to generate electricity or mechanical power, and thus, an exhaust gas 34 containing carbon dioxide is generated. In the bottoming cycle 104, the exhaust gas 34 from the topping cycle 102 can then be used to generate additional electricity or mechanical power. In various embodiments, the topping cycle 102 can be an internal combustion engine, an industrial process in which fuel is burned, or other. In some embodiments, the bottoming cycle 104 can be a heat exchanger, a boiler, a supercritical CO2 cycle, a superheater, an evaporator, a pump, or other. In an exemplary embodiment, as shown, the topping cycle 102 can be a gas turbine 10, and the bottoming cycle 104 can be a steam turbine system 22.

[0026] The combined cycle system 100 may include a gas turbine 10 for driving a first load 14. For example, the first load 14 may be a generator for generating electricity. The gas turbine 10 may include a turbine section 16, a combustor or combustion section 18, and a compressor section 20. The turbine section 16 and the compressor section 20 may be connected by one or more shafts 21. A combustor fuel supplier 15 may supply fuel to the combustor in the combustion section 18. The combustor fuel supplier 15 may supply natural gas, such as a hydrocarbon fuel, to the combustion section 18. The hydrocarbon fuel may include methane, propane, or other. In an exemplary embodiment, the combustor fuel supplier 15 may supply methane (CH4) to the combustion section 18. Additionally or alternatively, the combustor fuel supplier 15 may supply liquid fuel, such as diesel, crude oil, syngas, or other, to the combustor.

[0027] During operation of the gas turbine 10, a working fluid, such as air 171, flows into the compressor section 20 where it is gradually compressed, providing the compressed air to the combustors of the combustion section 18. The compressed air is mixed with fuel and combusted within each combustor to produce combustion gases. From the combustion section 18, the combustion gases flow through a hot gas path into the turbine section 16, where energy (kinetic and / or thermal) is transferred from the combustion gases to the rotor blades, causing one or more shafts 21 to rotate. The mechanical rotational energy can then be used to power the compressor section 20 and / or generate electricity.

[0028] The heated exhaust gas 34 exiting the turbine section 16 may then be exhausted from the gas turbine 10 and directed first to a heat recovery steam generator (HRSG) 32 or through a fuel cell 106 where a first portion of the pollutants (e.g., CO 2 ) are removed from the exhaust gas 34 . For example, in some embodiments, such as Figure 2As shown in , the exhaust gas 34 may first be directed through the HRSG 32 before entering the fuel cell 106. In such an embodiment, where the exhaust gas 34 is first directed through the HRSG 32 before entering the fuel cell 106, the exhaust gas will be cooled to between about 60°C and about 150°C upon exiting the HRSG 32. The inlet temperature of the exhaust gas 34 at the cathode side 116 needs to be between about 500°C and about 650°C. Therefore, a heat exchanger 180 may be provided on the cathode inlet line 118 for preheating the exhaust gas 34 before entering the cathode side 116. The heat exchanger 180 may be provided in thermal communication on the cathode inlet line 118 downstream of the HRSG 32 and upstream of the cathode side 116. The heat exchanger 180 may receive the cathode output product (e.g., the entire cathode output product) as a hot fluid. For example, the heat exchanger 180 may be in fluid communication on the cathode outlet line 146. After passing through the heat exchanger 180, the cathode output product may be provided to the carbon capture system 108. The cathode output product may transfer heat to the exhaust gas in the cathode inlet line 118. Additionally or alternatively, a burner 184 may be included on the cathode inlet line 118 to increase the temperature of the exhaust gas before entering the cathode side 116. The burner 184 may combust a fuel, which may be natural gas (e.g., from the fuel supply 15) or the anode output product.

[0029] In other embodiments, Figure 1 As shown in FIG, the exhaust gas 34 may first be directed through a fuel cell 106 before entering the HRSG 32. Within the HRSG 32, heat transfer occurs between the exhaust gas 34 and various components of the HRSG 32 to generate steam, which is provided to the steam turbine system 22. The exhaust gas 34 may then be directed to a carbon capture system 108, such as an adsorption bed, where a second portion (e.g., the remaining portion) of the pollutants (e.g., CO2) is removed from the exhaust gas. Finally, the exhaust gas 34 may exit the carbon capture system 108 to be discharged to the atmosphere via an exhaust pipe 110.

[0030] Upon exiting the turbine section 16, the exhaust gas 34 may primarily include nitrogen (N2), carbon dioxide (CO2), oxygen (O2), and water (H2O). In addition, the exhaust gas 34 may include trace amounts of carbon monoxide (CO), nitrogen oxides (NOx), sulfur oxides (SOx), and / or argon (Ar). In an exemplary embodiment of the combined cycle system 100, a first portion of the carbon dioxide (CO2) may be removed from the exhaust gas 34 in the fuel cell 106, and a second portion of the carbon dioxide (CO2) may be removed from the exhaust gas 34 in a separate carbon capture system 108 (e.g., an adsorption bed). In many embodiments, the second portion of the CO2 removed in the carbon capture system 108 may be the remaining portion of the CO2 in the exhaust gas 34, such that all of the CO2 (e.g., 100%) may be removed from the exhaust gas 34 before being discharged through the exhaust pipe 110.

[0031] The combined cycle system 100 may also include a steam turbine system 22 for driving a second load 24. The second load 24 may also be a generator for generating electricity. However, both the first load 14 and the second load 24 may be other types of loads that can be driven by the gas turbine 10 and the steam turbine system 22. Furthermore, although the gas turbine 10 and the steam turbine system 22 may drive separate loads 14 and 24 as shown in the illustrated embodiment, the gas turbine 10 and the steam turbine system 22 may also be utilized in series to drive a single load via a single shaft.

[0032] In the illustrated embodiment, the steam turbine system 22 may include a low pressure (LP) steam turbine 26, an intermediate pressure (IP) steam turbine 28, and a high pressure (HP) steam turbine 30. The low pressure (LP) steam turbine 26, the intermediate pressure (IP) steam turbine 28, the high pressure (HP) steam turbine 30, and the load 24 may each be disposed on one or more shafts 23 (such as a common shaft in some embodiments).

[0033] In an exemplary embodiment, the fuel cell 106 may include an anode side 112, a cathode side 116, and an electrolyte 114 (which may conduct charged ions). The fuel cell 106 may directly convert chemical energy stored in the hydrocarbon fuel into electrical energy through an electrochemical reaction. In an exemplary embodiment, the fuel cell 106 may be a molten carbonate fuel cell (MCFC), such as an internally reformed MCFC and / or an externally reformed MCFC. In such an embodiment, the electrolyte 114 may be a molten carbonate mixture suspended in a porous, chemically inert ceramic matrix of a beta-alumina solid electrolyte (BASE). The MCFC may be operated by passing a reactant fuel gas (e.g., natural gas) through the anode side 112 while passing an oxidizing gas (e.g., an exhaust gas containing carbon dioxide and oxygen) through the cathode side 116, which causes an electrochemical reaction across the electrolyte 114 that consumes (or chemically converts) the carbon dioxide and produces electricity. Specifically, in the cathode side 116, oxygen and carbon dioxide form carbonate ions (CO3 2- ).

[0034] As briefly mentioned above, the fuel cell 106 converts the anode fuel stream and the exhaust gas into electrical energy while removing CO2 from the exhaust gas (e.g., the CO2 is removed via an electrochemical reaction within the fuel cell 106). For example, the fuel cell power output 120 can be directed to a power converter 121 to change the DC current into an AC current that can be efficiently utilized by one or more subsystems. Specifically, for the described embodiment, the power output 120 is provided from the power converter to one or more electrical devices 122 via an electrical bus 124. The electrical bus 124 can be an electrical bus dedicated to the combined cycle system 100, the gas turbine 10, the steam turbine system 22, the electrical bus of the fuel cell 106, the electrical bus of the carbon capture system 108, etc. The electrical bus 124 is electrically connected to one or more additional electrical devices 122, which can be power sources, power receivers, or both. For example, the additional electrical devices 122 can be power storage devices (such as one or more batteries), electric machines (generators, electric motors, or both). Alternatively or in addition, the power output 120 can help drive the first load 14 and / or the second load 24. The combustion cycle system 100 can generate a total power output (e.g., the sum of the first load 14, the second load 24, and the power output 120 of the fuel cell 106). In many embodiments, the power output 120 of the fuel cell 106 can be between about 10% and about 30% of the total power output of the combined cycle system 100. In other embodiments, the power output 120 of the fuel cell 106 can be between about 15% and about 25% of the total power output of the combined cycle system 100.

[0035] In many embodiments, the cathode side 116 can be fluidly coupled (e.g., directly fluidly coupled) to the gas turbine 10 via a cathode inlet line 118. The cathode inlet line 118 can be the same conduit as the exhaust outlet line 117 extending from the outlet of the turbine section 16, or the cathode inlet line 118 can extend from the exhaust outlet line 117. Specifically, the cathode side 116 can be fluidly coupled to the outlet of the turbine section 16 such that the cathode side 116 receives a flow of exhaust gas 34 from the turbine section 16. For example, the cathode inlet line 118 can extend (e.g., directly) between the outlet of the turbine section 16 and the inlet of the cathode side 116 of the fuel cell 106 to deliver the exhaust gas 34 from the turbine section 16 to the cathode side 116. In an exemplary embodiment, all of the exhaust gas 34 from the outlet of the turbine section 16 may be directed through the cathode side 116 of the fuel cell 106 to remove a first portion of the pollutants (e.g., CO 2 ) from the exhaust gas 34 (i.e., no branch lines may extend from the cathode inlet line 118 ). In an alternative embodiment, as Figure 1 As shown, a fan or blower 157 can be included on the cathode inlet line 118. The fan 157 can advantageously overcome flow resistance in the cathode side 116, the HRSG 32, the direct contact cooler 155, and the carbon capture system 108. In other words, the fan 157 can facilitate the flow of exhaust gas through the cathode side 116, the HRSG 32, the direct contact cooler 155, and the carbon capture system 108.

[0036] In various embodiments, the anode side 112 may receive a fuel stream and / or a steam stream via an anode inlet line 126. Fuel and steam may be transported through the anode side 112. The anode inlet line 126 may fluidly couple the anode side 112 to an anode fuel supplier 128. In some embodiments, the anode fuel supplier 128 may be identical to the burner fuel supplier 15 so that the same fuel is simultaneously supplied to the anode side of the combustion section and the fuel cell 106. In other embodiments, the anode fuel supplier 128 and the burner fuel supplier 15 may be different. In many specific implementations, the anode fuel supplier 128 may supply natural gas (e.g., hydrocarbon fuel) to the anode side 112 via the anode inlet line 126. Natural gas may include methane, propane or other. In an exemplary embodiment, the anode fuel supplier 128 may supply methane (CH4) to the anode side 112. A fuel preheater 130, such as a heat exchanger, may be provided on the anode inlet line 126 in a thermally connected manner. The fuel preheater 130 may heat the fuel before it enters the anode side 112 of the fuel cell 106 , which advantageously increases the efficiency of the fuel cell 106 .

[0037] In an exemplary embodiment, the combined cycle system 100 may include an anode steam supply line 188. The anode steam supply line 188 may extend between the heat exchanger 136 and the anode inlet line 126. Steam may be generated from heat from the anode output product within the heat exchanger 136 and provided to the anode inlet line 126. The anode steam supply line 188 may provide a steam flow to the anode inlet line 126 for use in the anode side 112 of the fuel cell 106. In various embodiments (not shown), the anode steam supply line 126 may be fluidly coupled to the HRSG 32 such that the HRSG 32 supplies steam to both the steam turbine system 22 and the anode side 112 of the fuel cell 106.

[0038] In many embodiments, the combined cycle system 100 may include an anode outlet line 132 fluidly coupled to an outlet of the anode side 112 such that the anode outlet line 132 receives output products from the anode side 112 after the electrochemical reaction within the fuel cell 106. In certain embodiments, the anode output products may include CO2, CO, H2, water, and unused CH4 (e.g., methane not utilized within the fuel cell 106 during the electrochemical reaction). The anode output products may be supplied to a separation system 134, which may remove water and liquefied CO2 from the anode output products.

[0039] The separation system 134 may include a heat exchanger 136, a water flash separator 138, a compressor 140, a cooler 142, and a liquid carbon dioxide separator 144 in a series flow order (e.g., from upstream to downstream). The heat exchanger 136 may be thermally and fluidly coupled to the anode outlet line 132. For example, the anode outlet line 132 may extend between the outlet of the anode side 112 and the heat exchanger 136. The heat exchanger 136 may remove heat from the anode output product before the anode output product enters the water flash separator 138, which generates steam in a steam inlet line 188 for use at the inlet of the anode side in order to maintain a desired steam to carbon molar ratio (which may be between about 1.5 and about 5, or specifically between about 2 and about 3). The water flash inlet line 137 may extend between the heat exchanger 136 and the water flash separator 138 and fluidly couple the heat exchanger and the water flash separator. The water flash separator 138 can remove any water from the anode output product. For example, the water in the anode output product can be cooled to a liquefaction temperature by the heat exchanger 136 and then removed by the water flash separator 138. In some embodiments, the anode output product can be passed through a water-gas shift reactor to convert carbon monoxide into hydrogen. In such embodiments, the water-gas shift reactor can be positioned between the heat exchanger 136 and the water flash separator 138.

[0040] In many embodiments, a compressor inlet line 139 may extend between the water flash separator 138 and the compressor 140 and fluidly couple the water flash separator and the compressor. The compressor 140 may pressurize the anode output product and provide the pressurized anode output product to a cooler 142 via a cooler inlet line 141. The cooler 142 may liquefy the CO2 in the pressurized anode output product by reducing the temperature of the pressurized anode output product. The liquid CO2 may then be removed via a liquid carbon dioxide separator 144. The removed liquid carbon dioxide may be transported for carbon sequestration or utilization. For example, the cooler 142 may be fluidly coupled to the liquid carbon dioxide separator 144 via a connecting line 143.

[0041] An anode recirculation line 145 may extend from the outlet of the separation system 134 to the anode inlet line 126 (upstream of the fuel preheater 130). For example, the anode recirculation line 145 may extend from the liquid carbon dioxide separator 144 to the anode inlet line 126 downstream of the fuel preheater 130 to reintroduce the anode output product (from which water and liquid carbon dioxide have been removed) into the anode side 112. For example, the anode recirculation line 145 may advantageously reintroduce any unused methane and excess hydrogen back into the anode side 112 for electrochemical conversion.

[0042] In some embodiments, as Figure 1 As shown, the HRSG 32 can be disposed downstream of the cathode side 116. In such embodiments, the HRSG 32 can be fluidly coupled (e.g., in some embodiments, directly fluidly coupled) to the outlet of the cathode side 116 of the fuel cell 106. The HRSG 32 can generate a steam flow for use in the bottoming cycle 104. For example, a cathode outlet line 146 can extend between the outlet of the cathode side 116 and the HRSG 32 and fluidly couple the outlet of the cathode side and the HRSG. The HRSG 32 can generate steam using heat from the exhaust gas exiting the cathode side 116, and the steam can be supplied to the steam turbine system 22.

[0043] In other embodiments, Figure 2 As shown, the HRSG 32 may be disposed upstream of the cathode side 116. In such embodiments, the HRSG 32 may be fluidly coupled (e.g., in some embodiments, directly fluidly coupled) to the outlet of the turbine section 16. The HRSG 32 may generate a steam flow for use in the bottoming cycle 104. The HRSG 32 may use heat from the exhaust gas exiting the turbine section 16 to generate steam, and the steam may be supplied to the steam turbine system 22.

[0044] A steam supply line 148 may extend from the HRSG 32 to the steam turbine system 22. Specifically, the steam supply line 148 may extend from the HRSG 32 to the HP steam turbine 30. The outlet of the HP steam turbine 30 may be fluidly coupled to the inlet of the IP steam turbine 28, and the outlet of the IP steam turbine 28 may be fluidly coupled to the inlet of the LP steam turbine 26. Alternatively, in other embodiments (not shown), the outlet steam of the HP steam turbine 30 may re-enter a reheater in the HRSG and be superheated and then returned to the inlet of the IP steam turbine 28. The outlet of the LP steam turbine may be fluidly coupled to a condenser 150 via a turbine outlet line 152. The condenser may convert steam from the outlet of the LP steam turbine 26 into water, which may be provided back to the HRSG 32 via a condensate return line 151.

[0045] In certain embodiments, the combined cycle system 100 may further include a cathode recirculation line 168 extending from the cathode outlet line 146 and fluidly coupling the cathode outlet line to the cathode inlet line 118. For example, the cathode recirculation line 168 may fluidly extend between an inlet provided on the cathode outlet line 146 (e.g., between the outlet of the cathode side 116 and the inlet of the HRSG 32) and an outlet provided on the cathode inlet line 118. The cathode recirculation line may reintroduce any unreacted CO back to the cathode side 116 for further reaction / removal from the exhaust gas.

[0046] In many embodiments, such as Figure 1 As shown, a carbon capture system 108 (such as an adsorbent-based carbon capture system) can be fluidly coupled to the fuel cell 106 such that the carbon capture system 108 receives a cathode output product from the cathode side 116 of the fuel cell 106. Specifically, the carbon capture system can be fluidly coupled to the outlet of the HRSG 32 via a HRSG outlet line 154. The HRSG outlet line 154 can transport the exhaust gas from the outlet of the HRSG 32 to the carbon capture system 108. In an exemplary embodiment, the carbon capture system 108 can be an adsorption bed 156 that removes a second portion of the pollutants (e.g., CO2) from the exhaust gas. Specifically, the adsorption bed 156 can remove the remaining portion of the CO2 from the exhaust gas such that all of the CO2 is removed from the exhaust gas before exiting the exhaust pipe 110. Additionally, in some embodiments, such as Figure 1As shown, a direct contact cooler 155 may be included in the HRSG outlet line 154 to further cool the exhaust gas exiting the HRSG 32 before entering the carbon capture system 108. For example, the direct contact cooler 155 may be positioned on the HRSG outlet line 154 upstream of the carbon capture system 108. The direct contact cooler 155 may inject water (or other suitable coolant) into the exhaust gas to cool the temperature of the exhaust gas before it enters the carbon capture system 108.

[0047] In other embodiments, Figure 2 As shown, the carbon capture system 108 can be fluidly coupled (e.g., directly fluidly coupled) to the outlet of the cathode side 116 via a cathode outlet line 146. In such embodiments, the cathode outlet line 146 can extend between and fluidly couple the cathode side 116 and the carbon capture system 108. The cathode outlet line 146 can transport exhaust gas from the outlet of the cathode side 146 to the carbon capture system 108.

[0048] While the exemplary embodiment of the carbon capture system 108 includes an adsorption bed 156 , the carbon capture system 108 may employ various technologies, including but not limited to pressure swing adsorption, temperature swing adsorption, rapid temperature swing adsorption, vacuum temperature swing adsorption, chemical adsorption, cryogenic separation, and membrane separation, to separate the remaining carbon dioxide from the flue gas.

[0049] In various embodiments, the carbon capture system 108 may employ pressure swing adsorption (PSA). PSA can be used to separate carbon dioxide from a gas mixture. In PSA technology, solid molecular sieves are capable of adsorbing carbon dioxide at high partial pressures. Thus, at elevated pressures, carbon dioxide is removed from the gas mixture as it passes through an adsorption bed. The bed is regenerated by depressurization and purging. Typically, for critical operations, multiple adsorption vessels are used to continuously separate carbon dioxide, wherein one adsorption bed is in use while the other adsorption beds are being regenerated.

[0050] In an exemplary embodiment, the carbon capture system 108 may employ temperature swing adsorption (TSA). In TSA, an adsorbent adsorbs CO2 from the cathode output product at low temperatures (preferably between low temperatures and <60°C). Subsequently, the saturated adsorbent bed undergoes desorption by increasing the temperature (typically >100°C). Desorption may occur under vacuum conditions or in the presence of a purge gas to reduce the partial pressure of CO2. The heat required for desorption may be provided by steam from a low-pressure steam turbine. Finally, the adsorbent bed is cooled back to its initial temperature so that the bed is ready for the next adsorption cycle.

[0051] In certain embodiments, the carbon capture system 108 can separate carbon dioxide from the exhaust gas by chemical absorption using oxides such as calcium oxide (CaO) and magnesium oxide (MgO), or a combination thereof. In one embodiment, CO2 is absorbed by the CaO at elevated pressure and temperature to form calcium carbonate (CaCO3), thereby removing CO2 from the gas mixture. The adsorbent CaO is regenerated by calcining the CaCO3, which can reform the CaCO3 into CaO again.

[0052] In some embodiments, membrane separation technology may also be used by the carbon capture system 108 to separate carbon dioxide from the exhaust gas. Membranes used for high-temperature carbon dioxide separation include zeolite and ceramic membranes, which are selective for CO2. Membrane separators operate more efficiently at higher pressures, and separation of carbon dioxide from the exhaust gas using membrane separators can be achieved by further compression (e.g., using one or more compressors upstream of the carbon capture system 108).

[0053] In other embodiments, another technology that can be used by the carbon capture system 108 to separate CO2 from the exhaust gas may include, but is not limited to, chemical absorption of CO2 using amines. The exhaust gas can be cooled to a suitable temperature to chemically absorb the carbon dioxide using amines. This technology is based on alkanolamine solvents, which have the ability to absorb carbon dioxide at relatively low temperatures and are easily regenerated by increasing the temperature of the rich solvent. After regeneration of the rich solvent, a carbon dioxide-rich stream is obtained. The solvents used in this technology can include pure triethanolamine, monoethanolamine, diethanolamine, diisopropanolamine, diglycolamine, and piperazine, or mixtures thereof.

[0054] In some other embodiments, the carbon capture system may include at least one absorption vessel in which chemical absorption technology is used. In another embodiment, the carbon dioxide separator includes at least one membrane separator.

[0055] In an exemplary embodiment, the carbon capture system may include at least one adsorption bed 156 in which TSA technology may be used to separate carbon dioxide from the outlet exhaust gas stream. Specifically, in an exemplary embodiment, the carbon capture system 108 may include a plurality of adsorption beds 156 (e.g., from about 10 to about 500 adsorption beds, or such as from about 10 to about 400 adsorption beds, or such as from about 30 to about 250 adsorption beds, or such as from about 10 to about 100 adsorption beds). In operation, some of the adsorption beds 156 will undergo adsorption and some of the adsorption beds 156 may undergo desorption, while the remaining adsorption beds undergo cooling for the temperature swing adsorption process. At part load, due to the reduced CO2 flow rate in the exhaust gas (or cathode output product), only some of the adsorption beds need to operate, which leaves the other adsorption beds 156 in standby. Ambient air can be supplied to these standby adsorption beds 156 to adsorb additional CO2 from the ambient atmosphere, thereby achieving negative system emissions. Alternatively or in addition, some additional adsorption beds may be added, which may act as a direct air capture system that receives steam from a steam turbine for desorption. In this way, negative carbon emissions can be achieved during normal full-load conditions.

[0056] In other embodiments, the adsorption bed 156 may be a direct contact adsorption bed. A direct contact adsorption bed comprises a large rotating bed that includes multiple sections undergoing different processes. In such embodiments, the carbon capture system 108 may include from about 1 to about 100 direct contact adsorption beds.

[0057] For example, the combined cycle system 100 may also include an air inlet line 160 fluidly coupled to the atmosphere (or ambient environment) and the carbon capture system 108. Specifically, the air inlet line 160 may be in fluid communication with each of the adsorption beds 156 so that additional air can be supplied to the spare adsorption beds 156 for additional carbon capture. In many embodiments, a pump 162 (such as a fan or blower) and a valve 164 may be disposed in fluid communication with the air inlet line 160. The valve 164 may be actuated between an open position (which allows air to flow therethrough) and a closed position (which restricts or otherwise prevents the passage of air). The valve 164 may be located downstream of the pump 162. When the pump 162 is operating, the pump may create a pressure differential that draws air from the atmosphere. The air from the atmosphere may be passed through the carbon capture system 108 (e.g., the adsorption beds 156) to remove any contaminants (e.g., CO2) present in the air. This advantageously allows the combined cycle system 100 to have negative carbon dioxide emissions because all (e.g., 100%) of the carbon dioxide in the exhaust from the turbine section 16 can be captured by the fuel cell 106 and the carbon capture system 108, and additional atmospheric air can be introduced into the carbon capture system 108 via the air inlet line 160 for removal of carbon dioxide from the additional atmospheric air.

[0058]

[0046] Using the various techniques described herein, a carbon dioxide rich stream 158 is produced from the carbon capture system 108. The carbon dioxide rich stream 158 may be sequestered or exported for any other industrial use.

[0059] In many embodiments, the combined cycle system 100 may further include an exhaust line 166 extending between the carbon capture system 108 and the exhaust pipe 110. Specifically, the exhaust line 166 may extend between the outlet of the adsorption bed 156 and the exhaust pipe 110. The exhaust pipe 110 may discharge the exhaust gas (from which pollutants have been removed) into the atmosphere.

[0060] As described above, the fuel cell 106 and the carbon capture system 108 can jointly remove all pollutants (e.g., carbon dioxide) from the exhaust gas exiting the topping cycle 102 before the exhaust gas is discharged into the atmosphere via the exhaust pipe 110. For example, between approximately 85% and approximately 100% of the pollutants from the exhaust gas exiting the topping cycle 102 are jointly captured by the fuel cell 106 and the carbon capture system 108 (e.g., the adsorbent bed 156). The fuel cell 106 can remove the majority of the carbon dioxide from the exhaust gas, and the carbon capture system 108 can remove the remainder of the carbon dioxide from the exhaust gas. Specifically, when exhaust gas recirculation is implemented, between approximately 50% and approximately 90% of the carbon dioxide can be removed from the exhaust gas in the fuel cell 106, or, for example, between approximately 75% and approximately 85% can be removed without exhaust gas recirculation. While more carbon dioxide can be removed in the fuel cell 106, this is not possible without overusing the fuel cell 106, reducing the lifespan of the fuel cell 106, and reducing the electrical efficiency of the fuel cell 106 (i.e., the ratio of electricity generated from the fuel cell to the fuel energy supplied at the anode). Thus, operating the fuel cell 106 in a manner that removes between about 75% and about 85% of the carbon dioxide from the exhaust gas advantageously preserves the life of the fuel cell 106 and allows for efficient operation. The remainder of the carbon dioxide in the exhaust gas exiting the turbine section 16, for example, between about 10% and about 30% of the carbon dioxide in the exhaust gas (or such as between about 15% and about 25% of the carbon dioxide in the exhaust gas), can be removed by the carbon capture system 108 (e.g., adsorption bed 156 in the exemplary embodiment).

[0061] As discussed above, in some embodiments, Figure 1 As shown in , the HRSG 32 may be positioned downstream of the cathode side 116 such that the exhaust gas 34 travels through the cathode side 116 before entering the HRSG 32. In such an embodiment, the cathode outlet line 146 provides the exhaust gas (or cathode output product) to the HRSG 32, and the HRSG outlet line 154 may provide the exhaust gas to the carbon capture system 108. Alternatively, as shown in Figure 2As shown, the HRSG 32 may be positioned upstream of the cathode side 116. In such an embodiment, the HRSG 32 may receive exhaust gas from an exhaust gas outlet line 117. The exhaust gas may then be provided to the cathode side 116 via a cathode inlet line 118. Figure 2 As shown, when the HRSG 32 is positioned upstream of the fuel cell 106 , the cathode output product may be provided directly to the carbon capture system 108 (eg, via the cathode outlet line 146 ).

[0062] In many embodiments, such as Figure 1 and Figure 2 As shown, the combined cycle system 100 may include an exhaust gas recirculation line 170 that fluidly couples the turbine section 16 to the compressor section 20, such that exhaust gas from the outlet of the turbine section 16 is provided to the inlet of the compressor section 20. The exhaust gas recirculation line 170 may extend from the exhaust gas outlet line 117 to the compressor section 20. In such an embodiment, the compressor 20 may receive ambient air 171 as well as recirculated exhaust gas. When exhaust gas recirculation is introduced, this increases the CO₂ mol% in the gas turbine exhaust gas from approximately 4.3% to approximately 8%, allowing the fuel cell 106 to operate at a higher efficiency. For example, with exhaust gas recirculation, the fuel cell 106 can remove up to 90% of the CO₂ from the exhaust gas. The exhaust gas recirculation line 170 selectively diverts a portion of the exhaust gas from the exhaust gas outlet line 117 back to the inlet of the compressor section 20. For example, a valve 172 may be provided on the exhaust gas recirculation line 170. Valve 172 is selectively actuatable between an open position (which allows exhaust gas recirculation) and a closed position (which restricts or prevents exhaust gas recirculation). In addition, in an exemplary embodiment, an exhaust gas cooler 174 may be provided on exhaust gas recirculation line 170. Exhaust gas cooler 174 may be a heat exchanger that cools the exhaust gas within exhaust gas recirculation line 170 to meet the inlet temperature requirement of gas turbine 10.

[0063] Now see Figure 3 , a flow chart of one embodiment of a method 200 for removing pollutants in a combined cycle system is shown according to aspects of the present subject matter. Figure 1 and Figure 2 The method 200 is described with reference to the combined cycle system 100 described herein. However, one of ordinary skill in the art will appreciate that the disclosed method 200 may generally be used with any suitable combined cycle system and / or may be used in conjunction with a system having any other suitable system configuration. Figure 3For the purposes of illustration and discussion, the steps are depicted as being performed in a particular order, but unless otherwise indicated in the claims, the methods discussed herein are not limited to any particular order or arrangement. One skilled in the art, using the disclosure provided herein, will understand that the various steps of the methods disclosed herein may be omitted, rearranged, combined, and / or adjusted in various ways without departing from the scope of the present disclosure.

[0064] As shown, method 200 may include operating the topping cycle 102 of the combined cycle system 100 at (202), thereby generating a first power output and an exhaust gas. For example, operating the topping cycle 102 may include operating the gas turbine 10 at partial or full load. Thus, a first power output and an exhaust gas are generated. The first power output may be generated by a first load 14. For example, the first load 14 may be a generator coupled to the gas turbine 10 via one or more shafts that rotate to generate the first power output. The gas turbine 10 may combust natural gas fuel in a combustion section 18, which may be directed through the turbine section 16 and discharged as an exhaust gas that may contain pollutants such as carbon dioxide.

[0065] In an exemplary embodiment, as shown, the method 200 may further include passing the exhaust gas through the cathode side 116 of the fuel cell 106 at (204), thereby removing a first portion of the pollutants from the exhaust gas. For example, an electrochemical reaction may occur within the fuel cell 106 that both removes carbon dioxide from the exhaust gas and produces electricity, which may be provided to one or more electrical devices 122 via an electrical bus 124. In an exemplary embodiment, the fuel cell 106 may be a molten carbonate fuel cell (MCFC), such as an internal reforming MCFC and / or an external reforming MCFC. The MCFC may operate by passing a reactant fuel gas (e.g., natural gas mixed with steam) through the anode side 112 while passing an oxidizing gas (e.g., an exhaust gas containing carbon dioxide and oxygen) through the cathode side 116, which causes an electrochemical reaction across the electrolyte 114 that removes (or chemically converts) carbon dioxide and produces electricity and hydrogen.

[0066] In many implementations, as shown, the method 200 may further include providing the exhaust gas from the outlet of the cathode side (i.e., cathode output product) to the carbon capture system 108 at (206). A second portion of the pollutants (e.g., carbon dioxide) is removed from the exhaust gas once it passes through the carbon capture system 108. For example, the carbon capture system 108 may be an adsorption bed 156 that removes the remaining portion of the carbon dioxide from the exhaust gas downstream of the fuel cell 106.

[0067] For example, the pollutant may be carbon dioxide, and the first portion of the pollutant removed from the exhaust gas by the cathode side may be a majority (e.g., greater than 50%) of the carbon dioxide in the exhaust gas upon exiting the gas turbine 10. Thus, the second portion of the pollutant removed from the exhaust gas by the carbon capture system 108 may be the remainder of the carbon dioxide in the exhaust gas. Specifically, up to approximately 85% of the carbon dioxide in the exhaust gas from the turbine section 16 may be removed (i.e., electrochemically converted) in the cathode side 116 of the fuel cell 106, and the remainder (e.g., approximately 15%) of the carbon dioxide may be removed by the carbon capture system 108 before exiting the exhaust pipe 110. For example, between approximately 85% and approximately 100% of the pollutants from the exhaust gas exiting the topping cycle 102 may be captured by both the fuel cell 106 and the carbon capture system 108 (e.g., the adsorption beds 156). The fuel cell 106 may remove the majority of the carbon dioxide from the exhaust gas, and the carbon capture system 108 may remove the remainder of the carbon dioxide from the exhaust gas. Specifically, between about 70% and about 90% of the carbon dioxide, or such as between about 75% and about 85%, can be removed from the exhaust gas in the fuel cell 106. While more carbon dioxide can be removed in the fuel cell 106, this is not possible without overworking the fuel cell 106, reducing the lifespan of the fuel cell 106, and decreasing the efficiency of the fuel cell 106. Therefore, operating the fuel cell 106 in a manner that removes between about 50% and about 85% of the carbon dioxide from the exhaust gas (or, when exhaust gas recirculation is implemented, such as between about 50% and about 90%) advantageously preserves the lifespan of the fuel cell 106 and allows for efficient operation. The remainder of the carbon dioxide in the exhaust gas exiting the turbine section 16, for example, about 15% to about 50% (or such as about 15% to about 25%) of the exhaust gas, can be removed by the carbon capture system 108 (e.g., adsorption bed 156 in the exemplary embodiment).

[0068] In many implementations, operating the combined cycle system 100 may produce a total power output (e.g., the sum of the power generated by the first load 14, the power generated by the second load 24, and the power output 120 of the fuel cell 106). In an exemplary implementation, operating the fuel cell 106 and the carbon capture system 108 may require a power supply of between about 0.5% and about 5% (or, such as between about 3% and about 5%) of the total power output. As discussed above, the fuel cell 106 may be capable of more aggressive operation, wherein greater than 85%-90% of the carbon dioxide is captured in the fuel cell 106; however, this significantly increases the contribution from loss mechanisms such as cathode polarization (which is the primary resistance due to low concentrations of carbon dioxide), ohmic resistance, anode polarization, and activation losses. This reduces the overall power plant efficiency or electrical efficiency of the fuel cell 106. Operating the fuel cell 106 at up to about 85% carbon dioxide consumption, while capturing the remaining carbon dioxide with an additional carbon capture system 108 (e.g., adsorbent bed 156 in the exemplary embodiment), advantageously requires only a power supply of between about 3% and about 5% of the total power output of the combined cycle system 100 (which is lower than other designs) to achieve a 100% carbon capture rate, because the specific energy required to capture CO2 (MJ / kg captured CO2) increases monotonically with increasing carbon capture rate. In addition, the fuel cell 106 (such as an MCFC) integrates and generates about 20%-25% additional power, thereby increasing the net power output of the power plant, while all other carbon capture technologies consume energy, thereby reducing the net power output from the power plant. The fuel cell 106 (e.g., an MCFC) can generate about 20% to 25% excess power (assuming a carbon capture rate of about 85%; when the carbon capture rate is reduced to about 50%, the lower limit of the excess power can be about 10%); however, doing so also consumes fuel. Increasing the CO2 capture rate from the fuel cell 106 increases losses within the fuel cell 106, thereby reducing the fuel-to-electricity efficiency of the fuel cell 106, making the efficiency of generating electricity from the fuel cell 106 relatively low compared to generating electricity from a combined cycle power plant. In addition, the separation system 134 consumes parasitic loads, and these result in a reduction in the overall efficiency of the power plant of greater than about 2% (which may increase as the carbon capture rate in the fuel cell 106 increases). In an embodiment where the carbon capture rate in the fuel cell 106 is reduced to about 50%, the reduction in the overall efficiency of the power plant may be about 1%.

[0069] The maximum CO2 capture limit of the fuel cell 106 (such as an MCFC) will vary as a function of the CO2 concentration in the exhaust gas. The exhaust gas 34 of the gas turbine 10 typically contains about 5% mole of CO2. When exhaust gas recirculation is implemented, the %mol increases to about 8% mole of CO2, which in turn increases the maximum CO2 capture of the fuel cell 106 from about 85% to about 90%. Other processes, such as industrial processes, may have exhaust gases with high CO2 concentrations (for example, cement plant exhaust gas will have about 30% mole of CO2). In such specific implementations, when the fuel cell is supplied with exhaust gas from an industrial process with a high %mol of CO2 (such as a cement plant or coal plant), the fuel cell can achieve a higher capture rate (such as a carbon capture rate of greater than 90%).

[0070] In an alternative embodiment, as shown in the dashed box, the method 200 may include, at (208), passing the exhaust gas from the outlet of the cathode side 116 through a heat recovery steam generator 32 (HRSG) before providing the exhaust gas to the carbon capture system 108. In such an embodiment, the method may include generating steam with the HRSG 32 at (210) and providing the steam to the bottoming cycle 104 at (212). The bottoming cycle 104 may generate a second power output. For example, the bottoming cycle 104 may be a steam turbine system 22 that drives a second load 24 to generate electricity. The second load 24 may also be a generator for generating electricity.

[0071] In some embodiments, the method 200 may include providing air from the atmosphere in addition to the exhaust gas to the carbon capture system 108 at (214) (e.g., when operating the topping cycle 102 at part load for a properly sized adsorption bed, or when operating the topping cycle 102 at full load for an oversized adsorption bed). For example, for a system having a carbon capture system 108 sized based on the carbon dioxide output of the topping cycle 102, when the gas turbine 10 is operating at part load, air from the atmosphere may be introduced to the carbon capture system 108 via the air inlet line 160. Alternatively, for a system having an oversized carbon capture system 108 (e.g., sized larger than the gas turbine carbon dioxide output requirement), when the gas turbine 10 is operating at full load, air from the atmosphere may be introduced to the carbon capture system 108 via the air inlet line 160. As a result of providing air in addition to the exhaust gas from the gas turbine, carbon dioxide is removed from the air and the exhaust gas, causing the combustion system to produce negative carbon capture emissions. The gas turbine 10 can operate at full load (e.g., maximum capacity or 100%) and part load (e.g., less than maximum capacity or less than 100%). During full load, the gas turbine 10 can produce a large amount of exhaust gas, which can utilize the full carbon dioxide capture capacity of the fuel cell 106 and the carbon capture system 108. However, under part load conditions, the gas turbine 10 can produce less exhaust gas, thereby giving the carbon capture system 108 additional capacity for capturing carbon dioxide. This additional capacity can be used to capture carbon dioxide from the atmosphere, which advantageously allows the fuel cell 106 and the carbon capture system 108 to capture more than 100% of the carbon dioxide produced in the topping cycle 102 (e.g., the gas turbine 10). For example, all of the carbon dioxide produced in the topping cycle 102 can be captured by the fuel cell 106 and the carbon capture system 108, and additional carbon dioxide can be captured from the atmosphere by introducing air from the atmosphere into the carbon capture system 108 in addition to the exhaust gas.

[0072] 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 combined 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. If such other examples include 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, such other examples are intended to be within the scope of the claims.

[0073] Further aspects of the invention are provided by the subject matter of the following clauses:

[0074] A combustion system comprising: a topping cycle, the topping cycle generating an exhaust gas flow; a bottoming cycle; a fuel cell comprising an anode side, a cathode side, and an electrolyte, the cathode side receiving the exhaust gas flow from the topping cycle via a cathode inlet line, the cathode side removing a first portion of pollutants from the exhaust gas; a heat recovery steam generator (HRSG), the HRSG receiving the exhaust gas from the cathode side via a cathode outlet line, the HRSG generating a steam flow for use in the bottoming cycle; and a carbon capture system fluidly coupled to the HRSG via a HRSG outlet line, the carbon capture system removing a second portion of pollutants from the exhaust gas.

[0075] The combustion system of any preceding clause, wherein the carbon capture system comprises an adsorption bed.

[0076] The combustion system of any of the preceding clauses further comprising an air inlet line fluidly coupled to atmosphere and the carbon capture system.

[0077] The combustion system according to any of the preceding clauses, wherein the topping cycle is a gas turbine coupled to a first load, the gas turbine comprising a compressor section, a combustion section and a turbine section, the turbine section generating the exhaust gas.

[0078] The combustion system of any of the preceding clauses further comprising an exhaust gas recirculation line fluidly coupling the turbine section to the compressor section.

[0079] The combustion system according to any of the preceding clauses, wherein the fuel cell is a molten carbonate fuel cell (MCFC).

[0080] The combustion system of any of the preceding clauses further comprising a cathode recirculation line extending from the cathode outlet line to the cathode inlet line.

[0081] A carbon capture system according to any preceding clause, further comprising an exhaust line extending fluidly between the carbon capture system and an exhaust pipe.

[0082] The combustion system according to any of the preceding clauses, wherein the anode side receives a fuel flow and / or a steam flow via an anode inlet line.

[0083] The combustion system of any of the preceding clauses, further comprising an anode outlet line fluidly coupled to a separation system for removing water and liquid carbon dioxide from the anode output product.

[0084] A combustion system according to any of the preceding clauses, wherein between about 85% and about 100% of the pollutants from the exhaust gas exiting the topping cycle are captured by both the fuel cell and the carbon capture system.

[0085] A method for removing pollutants from a combustion system, the method comprising: operating a topping cycle of the combustion system, thereby producing a first power output and an exhaust gas; passing the exhaust gas through a cathode side of a fuel cell, thereby removing a first portion of the pollutants from the exhaust gas; and providing the exhaust gas from an outlet of the cathode side to a carbon capture system, wherein a second portion of the pollutants is removed from the exhaust gas by the carbon capture system.

[0086] A method according to any of the preceding clauses, wherein the pollutants include carbon dioxide, wherein the first portion of the pollutants removed from the exhaust gas by the cathode side includes a majority of the carbon dioxide in the exhaust gas, and wherein the second portion of the pollutants removed from the exhaust gas by the carbon capture system is the remainder of the carbon dioxide in the exhaust gas.

[0087] A method according to any of the preceding clauses, wherein the pollutant includes carbon dioxide, and wherein between about 50% and about 90% of the carbon dioxide from the exhaust gas is removed in the cathode side of the fuel cell, and wherein the remainder of the carbon dioxide from the exhaust gas is removed in the carbon capture system.

[0088] The method of any of the preceding clauses, wherein the combustion system produces a total power output, and wherein operating the fuel cell and the carbon capture system requires a power supply of between about 0.5% and about 5% of the total power output.

[0089] A method according to any of the preceding clauses, further comprising passing the exhaust gas from an outlet of the cathode side through a heat recovery steam generator (HRSG) before providing the exhaust gas to the carbon capture system.

[0090] The method of any of the preceding clauses, further comprising: generating steam with the HRSG; and providing the steam to a bottoming cycle of the combustion system, the bottoming cycle generating a second power output.

[0091] A method according to any of the preceding clauses, further comprising providing air from the atmospheric environment to the carbon capture system in addition to the flue gas, thereby removing carbon dioxide from the air such that the combustion system produces negative carbon capture emissions.

[0092] A method according to any of the preceding clauses, further comprising passing fuel and / or steam through the anode side of the fuel cell.

[0093] A combustion system comprising: a topping cycle, the topping cycle producing an exhaust gas flow; a bottoming cycle; a heat recovery steam generator (HRSG), the HRSG receiving the exhaust gas from the topping cycle, the HRSG producing a steam flow for use in the bottoming cycle; and a fuel cell comprising an anode side, a cathode side, and an electrolyte, the cathode side receiving the exhaust gas flow from the HRSG via a cathode inlet line, the cathode side removing a first portion of pollutants from the exhaust gas; and a carbon capture system fluidly coupled to the cathode side via a cathode outlet line, the carbon capture system removing a second portion of pollutants from the exhaust gas.

[0094] The combustion system of any preceding clause, wherein the carbon capture system comprises an adsorption bed.

[0095] The combustion system of any of the preceding clauses further comprising an air inlet line fluidly coupled to atmosphere and the carbon capture system.

[0096] The combustion system according to any of the preceding clauses, wherein the topping cycle is a gas turbine coupled to a first load, the gas turbine comprising a compressor section, a combustion section and a turbine section, the turbine section generating the exhaust gas.

[0097] The combustion system according to any of the preceding clauses, wherein the fuel cell is a molten carbonate fuel cell (MCFC).

[0098] The combustion system of any of the preceding clauses further comprising a cathode recirculation line extending from the cathode outlet line to the cathode inlet line.

[0099] A carbon capture system according to any preceding clause, further comprising an exhaust line extending fluidly between the carbon capture system and an exhaust pipe.

[0100] The combustion system according to any of the preceding clauses, wherein the anode side receives a fuel flow and / or a steam flow via an anode inlet line.

[0101] The combustion system of any of the preceding clauses, further comprising an anode outlet line fluidly coupled to a separation system for removing water and liquid carbon dioxide from the anode output product.

[0102] A combustion system according to any of the preceding clauses, wherein between about 85% and about 100% of the pollutants from the exhaust gas exiting the topping cycle are captured by both the fuel cell and the carbon capture system.

[0103] A combustion system, the combustion system comprising: a gas turbine, the gas turbine comprising a compressor section, a combustion section and a turbine section, the turbine section generating exhaust gas; a fuel cell, the fuel cell comprising an anode side, a cathode side and an electrolyte, the cathode side receiving the exhaust gas from the turbine section via an exhaust gas outlet line, the cathode side removing a first portion of pollutants from the exhaust gas; a carbon capture system fluidly connected to the fuel cell for removing a second portion of pollutants from the exhaust gas; and an exhaust gas recirculation line extending from the exhaust gas outlet line to the compressor section.

[0104] The combustion system of any preceding clause, wherein the carbon capture system comprises an adsorption bed.

[0105] The combustion system of any of the preceding clauses further comprising an air inlet line fluidly coupled to atmosphere and the carbon capture system.

[0106] The combustion system according to any of the preceding clauses, wherein the fuel cell is a molten carbonate fuel cell (MCFC).

[0107] The combustion system of any of the preceding clauses further comprising a cathode recirculation line extending from the cathode outlet line to the cathode inlet line.

[0108] A carbon capture system according to any preceding clause, further comprising an exhaust line extending fluidly between the carbon capture system and an exhaust pipe.

[0109] The combustion system according to any of the preceding clauses, wherein the anode side receives a fuel flow and / or a steam flow via an anode inlet line.

[0110] The combustion system of any of the preceding clauses, further comprising an anode outlet line fluidly coupled to a separation system for removing water and liquid carbon dioxide from the anode output product.

[0111] A combustion system according to any of the preceding clauses, wherein between about 85% and about 100% of the pollutants from the exhaust gas exiting the topping cycle are captured by both the fuel cell and the carbon capture system.

Claims

1. A combustion system, comprising: a topping cycle that produces an exhaust gas stream; bottoming cycle; a fuel cell comprising an anode side, a cathode side, and an electrolyte, the cathode side receiving the exhaust gas stream from the topping cycle via a cathode inlet line, the cathode side removing a first portion of pollutants from the exhaust gas; a heat recovery steam generator (HRSG), the HRSG receiving the exhaust gas from the cathode side via a cathode outlet line, the HRSG generating a steam flow for use in the bottoming cycle; and A carbon capture system is fluidly coupled to the HRSG via a HRSG outlet line, the carbon capture system removing a second portion of the pollutants from the exhaust gas.

2. The combustion system of claim 1, wherein the carbon capture system comprises an adsorption bed. 3 . The combustion system of claim 1 , further comprising an air inlet line fluidly coupled to an atmospheric environment and the carbon capture system. 4 . The combustion system of claim 1 , wherein the topping cycle is a gas turbine coupled to a first load, the gas turbine comprising a compressor section, a combustion section, and a turbine section, the turbine section generating the exhaust gas. 5 . The combustion system of claim 4 , further comprising an exhaust gas recirculation line fluidly coupling the turbine section to the compressor section.

6. The combustion system of claim 1, wherein the fuel cell is a molten carbonate fuel cell (MCFC). 7 . The combustion system of claim 1 , further comprising a cathode recirculation line extending from the cathode outlet line to the cathode inlet line.

8. The carbon capture system of claim 1, further comprising an exhaust line fluidly extending between the carbon capture system and an exhaust pipe.

9. The combustion system of claim 1, wherein the anode side receives a fuel flow and / or a steam flow via an anode inlet line.

10. The combustion system of claim 1, further comprising an anode outlet line fluidly coupled to a separation system for removing water and liquid carbon dioxide from the anode output product.

11. The combustion system of claim 1 , wherein between about 85% and about 100% of the pollutants from the exhaust gas exiting the topping cycle are captured by both the fuel cell and the carbon capture system.

12. A method for removing pollutants from a combustion system, the method comprising: operating a topping cycle of the combustion system to thereby produce a first power output and an exhaust gas; passing the exhaust gas through a cathode side of a fuel cell, thereby removing a first portion of the contaminants from the exhaust gas; as well as The exhaust gas from the outlet of the cathode side is provided to a carbon capture system, wherein a second portion of the pollutants are removed from the exhaust gas by the carbon capture system.

13. A method according to claim 12, wherein the pollutants include carbon dioxide, wherein the first portion of the pollutants removed from the exhaust gas by the cathode side includes a majority of the carbon dioxide in the exhaust gas, and wherein the second portion of the pollutants removed from the exhaust gas by the carbon capture system is the remainder of the carbon dioxide in the exhaust gas.

14. The method of claim 12, wherein the pollutants include carbon dioxide, and wherein between about 50% and about 90% of the carbon dioxide from the exhaust gas is removed in the cathode side of the fuel cell, and wherein the remainder of the carbon dioxide from the exhaust gas is removed in the carbon capture system.

15. The method of claim 12, wherein the combustion system produces a total power output, and wherein operating the fuel cell and the carbon capture system requires a power supply between about 0.5% and about 5% of the total power output.

16. The method of claim 12, further comprising routing the exhaust gas from an outlet of the cathode side through a heat recovery steam generator (HRSG) before providing the exhaust gas to the carbon capture system.

17. The method according to claim 16, further comprising: generating steam with the HRSG; as well as The steam is provided to a bottoming cycle of the combustion system, the bottoming cycle generating a second power output.

18. The method of claim 12, further comprising providing air from the atmospheric environment to the carbon capture system in addition to the exhaust gas, thereby removing carbon dioxide from the air such that the combustion system produces negative carbon capture emissions.

19. The method of claim 12, further comprising delivering fuel and / or steam through the anode side of the fuel cell.

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