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 heat recovery steam generator (HRSG) that receives the exhaust gas from the top cycle. The HRSG produces a steam stream for use in the bottom cycle. A fuel cell includes an anode side, a cathode side, and an electrolyte. The cathode side receives an off-gas stream from the HRSG via a cathode inlet line. The cathode side removes a first portion of the contaminant from the exhaust gas. The 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 contaminant from the exhaust gas.

Description

Technical Field

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

[0002] Gas turbine power plants such as combined cycle power plants (CCPPs) or combined cycle systems (CCSs) typically include 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 gradually compressed as the air is directed toward a compressor discharge or diffuser housing that at least partially surrounds the burners of the combustion section. At least a portion of the compressed air is mixed with fuel and burned in a combustion chamber defined within the burners, thereby generating high temperature and high pressure combustion gases.

[0003] The combustion gases are directed along a hot gas path from the burners through the turbine, where the gases gradually expand as they flow through alternating stationary blade stages and rotatable turbine blade stages coupled to a 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 gases, and the exhaust gases enter the HRSG. Thermal energy from the exhaust gases is transferred to water flowing through one or more heat exchangers of the HRSG, thereby generating superheated or supercritical steam. The superheated steam is then directed into 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 pollution emissions such as nitrogen oxides (NOx), carbon monoxide (CO), and carbon dioxide (CO2). To reduce emissions, a carbon capture system is utilized to capture CO2 and other air pollution gases before the turbine gases are discharged into the ambient atmosphere. However, known carbon capture systems are only partially effective and require a large amount of energy.

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

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

[0007] According to one embodiment, a combustion system is provided. The combustion system includes a top cycle and a bottom cycle, and the top cycle generates an exhaust gas stream. The combustion system further includes a fuel cell that includes an anode side, a cathode side, and an electrolyte. The cathode side receives the exhaust gas stream from the top cycle via a cathode inlet line. The cathode side removes a first portion of pollutants from the exhaust gas. The combustion system further 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 bottom cycle. A carbon capture system is fluidly coupled to the HRSG via an HRSG outlet line. The carbon capture system removes a second portion of pollutants from the exhaust gas.

[0008] According to another embodiment, a method of removing pollutants from a combustion system is provided. The method includes operating a top cycle of the combustion system, thereby generating a first power output and an exhaust gas. The method further includes passing the exhaust gas through a cathode side of a fuel cell, thereby removing a first portion of pollutants from the exhaust gas. The method further includes providing the exhaust gas from an outlet of 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 top cycle and a bottom cycle, and the top cycle generates an exhaust gas stream. The combustion system further includes a heat recovery steam generator (HRSG) that receives the exhaust gas from the top cycle. The HRSG generates a steam stream for use in the bottom cycle. A 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 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 an 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 to remove a second portion of 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 the appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the technology of the present invention and, together with the description, serve to explain the principles of the technology of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] This specification sets forth a complete and enabling disclosure of the combustion systems and methods of the present invention, including the best mode of making and using the systems and methods of the present invention, with reference to the accompanying drawings, where:

[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 flowchart of a method for removing pollutants from 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 technology of the present invention and not as a limitation thereof. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the technology of the present invention without departing from the scope or spirit of the technology of the present invention as protected by the claims. For example, features illustrated or described as part of one embodiment can be used in another embodiment to yield yet another embodiment. Accordingly, this disclosure is intended to cover such modifications and variations that fall within the scope of the appended claims and their equivalents.

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

[0018] The detailed description uses numerical and alphabetical names to refer to features in the drawings. Similar or like names in the drawings and description have been used to refer to similar or like components of the present invention. As used herein, the terms "first", "second", and "third" may be used interchangeably to distinguish one component from another and are not intended to denote the position or importance of the individual components.

[0019] The term "fluid" can be a gas or a liquid. The term "fluidly connected" means that fluid can make a connection between specified regions.

[0020] As used herein, the terms "upstream" (or "upward") and "downstream" (or "downward") refer to the relative direction with respect to the flow of fluid in a fluid passage. For example, "upstream" refers to the direction from which the fluid flows, and "downstream" refers to the direction towards which the fluid flows. However, the terms "upstream" and "downstream" as used herein may also refer to an electric current. The term "radially" refers to a relative direction that is substantially perpendicular to the axial centerline of a particular component, the term "axially" refers to a relative direction that is substantially parallel and / or coaxially aligned with the 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 having approximate meanings (such as "about", "approximately", "substantially", and "essentially") are not limited to the specified exact value. In at least some cases, the approximate language may correspond to the precision of the instrument used to measure the value, or the precision of the method or machine used to construct or manufacture the component and / or system. For example, the 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 the end values defining 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 stated angle or direction. For example, "substantially vertical" includes a direction within ten degrees of vertical in any direction (e.g., clockwise or counterclockwise).

[0022] Unless otherwise specified herein, the terms "coupled", "fixed", "attached to", etc. 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", "comprising", "has", or any other variation thereof are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that includes a list of features is not necessarily limited to those features, but may include other features not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, "or" refers to an inclusive or and not an exclusive or. For example, the condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or absent); A is false (or absent) and B is true (or present); and both A and B are true (or present).

[0023] Herein and throughout the specification and claims, unless the context or language indicates otherwise, range limitations are combined and interchanged, such ranges are identified and include all subranges subsumed therein. For example, all ranges disclosed herein include the end values, and the end values may be combined independently of each other.

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

[0025] Referring now to the drawings, Figure 1 and Figure 2 each shows a schematic diagram of an embodiment of a combustion system or combined cycle system 100 that includes a topping cycle 102 and a bottoming cycle 104. In the topping cycle 102, fuel is burned to generate electrical or mechanical power and, as a result, exhaust gas 34 containing carbon dioxide is produced. In the bottoming cycle 104, the exhaust gas 34 from the topping cycle 102 can then be used to generate additional electrical 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 others. 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 others. 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 can include a gas turbine 10 for driving a first load 14. For example, the first load 14 can be a generator for generating electricity. The gas turbine 10 can include a turbine section 16, a burner or combustion section 18, and a compressor section 20. The turbine section 16 and the compressor section 20 can be connected by one or more shafts 21. A burner fuel supply 15 can supply fuel to a burner in the combustion section 18. The burner fuel supply 15 can supply natural gas, such as a hydrocarbon fuel, to the combustion section 18, and the hydrocarbon fuel can include methane, propane, or others. In an exemplary embodiment, the burner fuel supply 15 can supply methane (CH4) to the combustion section 18. Additionally or alternatively, the burner fuel supply 15 can supply a liquid fuel, such as diesel, crude oil, syngas, or others, to the burner.

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

[0028] The heated exhaust gas 34 leaving the turbine section 16 can then be discharged from the gas turbine 10 and first directed to a heat recovery steam generator (HRSG) 32 or through a fuel cell 106 where a first portion of the contaminants (e.g., CO2) is removed from the exhaust gas 34. For example, in some embodiments, as Figure 2As shown, the exhaust gas 34 may first be directed through the HRSG 32 before entering the fuel cell 106. In such embodiments, 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 when leaving 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. Accordingly, 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 arranged 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 the 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 for increasing 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, as Figure 1 shown, the exhaust gas 34 may first be directed through the fuel cell 106 before entering the HRSG 32. In the HRSG 32, heat transfer occurs between the exhaust gas 34 and the various components of the HRSG 32 to generate steam, which is provided to the steam turbine system 22. Then, the exhaust gas 34 may be directed to the 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 leave the carbon capture system 108 to be discharged to the ambient atmosphere via the exhaust pipe 110.

[0030] Upon exiting the turbine section 16, the exhaust gas 34 may mainly include nitrogen (N2), carbon dioxide (CO2), oxygen (O2), and water (H2O). Additionally, 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 an additional 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 via the exhaust pipe 110.

[0031] The combined cycle system 100 may further 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 capable of being driven by the gas turbine 10 and the steam turbine system 22. Additionally, 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, a medium pressure (IP) steam turbine 28, and a high pressure (HP) steam turbine 30. The low pressure (LP) steam turbine 26, the medium 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 (in some embodiments, such as a common shaft).

[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 the chemical energy stored in a 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 embodiments, the electrolyte 114 may be a molten carbonate mixture suspended in a porous chemically inert ceramic matrix of a β-aluminum 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) carbon dioxide and generates 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., CO2 is removed via an electrochemical reaction within the fuel cell 106). For example, the fuel cell power output 120 may be directed to a power converter 121 to change the DC current into an AC current that can be effectively 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 may 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 in electrical communication with one or more additional electrical devices 122, which may be a power source, a power receiver, or both. For example, the additional electrical device 122 may be a power storage device (such as one or more batteries), an electric machine (a generator, an electric motor, or both). Alternatively or in addition, the power output 120 may assist in driving the first load 14 and / or the second load 24. The combustion cycle system 100 may generate a total power output (e.g., the sum of the power outputs of the first load 14, the second load 24, and the fuel cell 106). In many embodiments, the power output 120 of the fuel cell 106 may 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 may 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 may be fluidly coupled (e.g., directly fluidly coupled) to the gas turbine 10 via the cathode inlet line 118. The cathode inlet line 118 may be the same conduit as the exhaust gas outlet line 117 extending from the outlet of the turbine section 16, or the cathode inlet line 118 may extend from the exhaust gas outlet line 117. Specifically, the cathode side 116 may be fluidly coupled to the outlet of the turbine section 16 such that the cathode side 116 receives the exhaust gas 34 flow from the turbine section 16. For example, the cathode inlet line 118 may 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 convey 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 contaminants (e.g., CO2) from the exhaust gas 34 (i.e., no branch line may extend from the cathode inlet line 118). In an alternative embodiment, as Figure 1 shown, a fan or blower 157 may be included on the cathode inlet line 118. The fan 157 may advantageously overcome the 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 may facilitate the flow of the 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 the anode inlet line 126. The fuel and steam may be conveyed through the anode side 112. The anode inlet line 126 may fluidly couple the anode side 112 to the anode fuel supplier 128. In some embodiments, the anode fuel supplier 128 may be the same as the burner fuel supplier 15 such that the same fuel is supplied to both the combustion section and the anode side of 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. The natural gas may include methane, propane, or others. 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 disposed on the anode inlet line 126 in thermal communication. The fuel preheater 130 may heat the fuel before it enters the anode side 112 of the fuel cell 106, which advantageously improves 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 by the heat from the anode output product within the heat exchanger 136 and supplied 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 the outlet of the anode side 112 such that the anode outlet line 132 receives the output product from the anode side 112 after the electrochemical reaction within the fuel cell 106. In certain embodiments, the anode output product may include CO2, CO, H2, water, and unutilized CH4 (e.g., methane not utilized within the fuel cell 106 during the electrochemical reaction). The anode output product may be supplied to a separation system 134, which may remove water and liquefied CO2 from the anode output product.

[0039] The separation system 134 may include, in a series flow order (e.g., from upstream to downstream), a heat exchanger 136, a water flash separator 138, a compressor 140, a cooler 142, and a liquid carbon dioxide separator 144. The heat exchanger 136 may be thermally coupled 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 the 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 to the water flash separator. The water flash separator 138 may remove any water from the anode output product. For example, the water in the anode output product may be cooled to the liquefaction temperature by the heat exchanger 136 and then removed by the water flash separator 138. In some embodiments, the anode output product may pass through a water gas shift reactor to convert carbon monoxide to hydrogen. In such embodiments, the water gas shift reactor may be disposed between the heat exchanger 136 and the water flash separator 138.

[0040] In many embodiments, the 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 supply the pressurized anode output product to the cooler 142 via the 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. Subsequently, the liquid CO2 may be removed via the 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 the connection line 143.

[0041] The 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 (which has had water and liquid carbon dioxide removed) into the anode side 112. For example, the anode recirculation line 145 may advantageously reintroduce any unutilized methane and excess hydrogen back into the anode side 112 for electrochemical conversion.

[0042] In some embodiments, as Figure 1 shown, the HRSG 32 may be disposed downstream 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 cathode side 116 of the fuel cell 106. The HRSG 32 may generate a steam stream for use in the bottom cycle 104. For example, the cathode outlet line 146 may 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 may generate steam with the heat from the exhaust gas leaving the cathode side 116, and the steam may be supplied to the steam turbine system 22.

[0043] In other embodiments, as Figure 2 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 stream for use in the bottom cycle 104. The HRSG 32 may generate steam with the heat from the exhaust gas leaving the turbine section 16, 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, the direct contact cooler 155 can be included in the HRSG outlet line 154 to further cool the exhaust gas before the exhaust gas leaving the HRSG 32 enters the carbon capture system 108. For example, the direct contact cooler 155 can be disposed on the HRSG outlet line 154 upstream of the carbon capture system 108. The direct contact cooler 155 can 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, as Figure 2 shown, the carbon capture system 108 can be fluidly coupled (e.g., directly fluidly coupled) to the outlet of the cathode side 116 via the cathode outlet line 146. In such embodiments, the cathode outlet line 146 can extend between the cathode side 116 and the carbon capture system 108 and fluidly couple the cathode side and the carbon capture system. The cathode outlet line 146 can convey the exhaust gas from the outlet of the cathode side 146 to the carbon capture system 108.

[0048] Although the exemplary embodiment of the carbon capture system 108 includes the adsorption bed 156, the carbon capture system 108 can apply 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 exhaust gas.

[0049] In various embodiments, the carbon capture system 108 can employ pressure swing adsorption (PSA). PSA can be used to separate carbon dioxide from a gas mixture. In the PSA technology, at high partial pressure, the solid molecular sieve is capable of adsorbing carbon dioxide. Thus, at elevated pressure, when the gas mixture passes through the adsorption bed, carbon dioxide is removed from the mixture. The regeneration of the bed is achieved by reducing the pressure and purging. Typically, for critical operations, multiple adsorption vessels are used to continuously separate carbon dioxide, where one adsorption bed is used to regenerate other adsorption beds simultaneously.

[0050] In an exemplary embodiment, the carbon capture system 108 can employ temperature swing adsorption (TSA). In TSA, the adsorbent adsorbs CO2 from the cathode output product at low temperature (preferably between low temperature and <60 °C). Subsequently, the saturated adsorbent bed undergoes desorption by raising the temperature (usually >100 °C). The desorption can occur under vacuum conditions or in the presence of a purge gas to reduce the partial pressure of CO2. The heat required for desorption can be provided by steam from a low-pressure steam turbine. Finally, the adsorbent bed is cooled back to the 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, at elevated pressure and temperature, CO2 is absorbed by CaO to form calcium carbonate (CaCO3), thereby removing CO2 from the gas mixture. The adsorbent CaO is regenerated by calcining CaCO3, which can reform CaCO3 back into CaO again.

[0052] In some embodiments, membrane separation technology can also be used by the carbon capture system 108 to separate carbon dioxide from the exhaust gas. Membranes for high-temperature carbon dioxide separation include zeolites and ceramic membranes, which are selective for CO2. Membrane separators work more efficiently at higher pressures, and separating carbon dioxide from the exhaust gas using a membrane separator 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 technique that can be used by the carbon capture system 108 to separate CO2 from the exhaust gas can include, but is not limited to, using amine chemical absorption of CO2. The exhaust gas can be cooled to a suitable temperature to use amine chemical absorption of carbon dioxide. This technique is based on alkanolamine solvents, which have the ability to absorb carbon dioxide at relatively low temperatures and are easily regenerated by raising the temperature of the rich solvent. A carbon dioxide-rich stream is obtained after the rich solvent is regenerated. Solvents used in this technique can include pure triethanolamine, monoethanolamine, diethanolamine, diisopropanolamine, diethylene glycolamine, and piperazine or mixtures thereof.

[0054] In some other embodiments, the carbon capture system can include at least one absorption container where 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 stream of the exhaust gas. 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, such as from about 10 to about 400 adsorption beds, 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 partial 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, leaving the other adsorption beds 156 in standby. Ambient air may be supplied to these standby adsorption beds 156 to adsorb additional CO2 from the atmospheric environment, 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 the steam turbine for desorption. In this way, negative carbon emissions may be achieved during normal full load conditions.

[0056] In other embodiments, the adsorption bed 156 may be a direct contact adsorption bed. The direct contact adsorption bed includes a large rotating bed that includes a plurality of zones that undergo 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 atmospheric environment (or surrounding 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 such that additional air may be supplied to the standby 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 the air inlet line 160 in a fluid communication manner. The valve 164 may be actuated between an open position (which allows air to flow therethrough) and a closed position (which restricts or otherwise blocks air passage). The valve 164 may be located downstream of the pump 162. When the pump 162 operates, the pump may create a pressure differential that draws air from the atmospheric environment. Air from the atmospheric environment may pass through the carbon capture system 108 (e.g., the adsorption bed 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 of the carbon dioxide (e.g., 100%) in the exhaust gas from the turbine section 16 may be captured by the fuel cell 106 and the carbon capture system 108, and additional atmospheric air may be introduced into the carbon capture system 108 through the air inlet line 160 for removing the carbon dioxide of the additional atmospheric air.

[0058] 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 can be sequestered or output for any other industrial use.

[0059] In many embodiments, the combined cycle system 100 may further include an exhaust pipeline 166 extending between the carbon capture system 108 and the exhaust pipe 110. Specifically, the exhaust pipeline 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 ambient atmosphere.

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

[0061] As discussed above, in some embodiments, as Figure 1 shown, the HRSG 32 may be disposed 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 embodiments, the cathode outlet pipeline 146 supplies the exhaust gas (or the cathode output product) to the HRSG 32, and the HRSG outlet pipeline 154 may supply the exhaust gas to the carbon capture system 108. Alternatively, as Figure 2As shown, the HRSG 32 can be disposed upstream of the cathode side 116. In such an embodiment, the HRSG 32 can receive exhaust gas from the exhaust gas outlet line 117. Subsequently, the exhaust gas can be provided to the cathode side 116 via the cathode inlet line 118. Additionally, as Figure 2 shown, when the HRSG 32 is disposed upstream of the fuel cell 106, the cathode output product can be directly provided to the carbon capture system 108 (e.g., via the cathode outlet line 146).

[0062] In many embodiments, as Figure 1 and Figure 2 shown, the combined cycle system 100 can include an exhaust gas recirculation line 170 that fluidly couples the turbine section 16 to the compressor section 20 such that the 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 can extend from the exhaust gas outlet line 117 to the compressor section 20. In such an embodiment, the compressor 20 can 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 from about 4.3% to about 8%, which allows the fuel cell 106 to operate at higher efficiency. For example, in the case of 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 transfers 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 can be disposed on the exhaust gas recirculation line 170. The valve 172 can be selectively actuated between an open position (which allows exhaust gas recirculation) and a closed position (which limits or prevents exhaust gas recirculation). Additionally, in an exemplary embodiment, an exhaust gas cooler 174 can be disposed on the exhaust gas recirculation line 170. The exhaust gas cooler 174 can be a heat exchanger that cools the exhaust gas within the exhaust gas recirculation line 170 to meet the inlet temperature requirements of the gas turbine 10.

[0063] Now referring to Figure 3 , a flowchart of one embodiment of a method 200 for removing pollutants in a combined cycle system is shown in accordance with aspects of the present subject matter. Generally speaking, the method 200 will be described herein with reference to the combined cycle system 100 described above with reference to Figure 1 and Figure 2 . However, those of ordinary skill in the art will understand that the disclosed method 200 can generally be used with any suitable combined cycle system and / or can be combined with a system having any other suitable system configuration. Additionally, although 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 can be carbon dioxide, and the first portion of the pollutant removed from the exhaust gas through the cathode side can be most (e.g., greater than 50%) of the carbon dioxide in the exhaust gas when leaving the gas turbine 10. Thus, the second portion of the pollutant removed from the exhaust gas by the carbon capture system 108 can be the remaining portion of the carbon dioxide in the exhaust gas. Specifically, up to about 85% of the carbon dioxide in the exhaust gas from the turbine section 16 can be removed (i.e., electrochemically converted) in the cathode side 116 of the fuel cell 106, and the remaining portion of the carbon dioxide (e.g., about 15%) can be removed by the carbon capture system 108 before being discharged from the exhaust pipe 110. For example, between about 85% and about 100% of the pollutants from the exhaust gas leaving the topping cycle 102 are captured jointly by the fuel cell 106 and the carbon capture system 108 (e.g., the adsorption bed 156). The fuel cell 106 can remove most of the carbon dioxide from the exhaust gas, and the carbon capture system 108 can remove the remaining portion 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% of the carbon dioxide, can be removed from the exhaust gas in the fuel cell 106. Although more carbon dioxide can be removed in the fuel cell 106, this is not possible without overusing the fuel cell 106, reducing the life of the fuel cell 106, and reducing the efficiency of the fuel cell 106. Thus, operating the fuel cell 106 in a manner that removes between about 50% and about 85% (or when exhaust gas recirculation is implemented, such as between about 50% and about 90%) of the carbon dioxide from the exhaust gas advantageously maintains the life of the fuel cell 106 and allows for efficient operation. The remaining portion of the carbon dioxide in the exhaust gas leaving the turbine section 16, e.g., 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., the 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 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 (e.g., cement plant exhaust gases will have about 30% mole of CO2). In such specific implementations, when the fuel cell is supplied with exhaust gas from an industrial process (such as a cement plant or a coal plant) with a high %mol of CO2, the fuel cell can achieve a higher capture rate (such as a carbon capture rate greater than 90%).

[0070] In an alternative specific implementation, as shown by the dashed box, the method 200 may include, at (208), before providing the exhaust gas to the carbon capture system 108, conveying the exhaust gas through a heat recovery steam generator 32 (HRSG) from the outlet of the cathode side 116. In such an embodiment, the method may include generating steam with the HRSG 32 at (210) and providing the steam to the bottom cycle 104 at (212). The bottom cycle 104 may generate a second power output. For example, the bottom 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, method 200 may include providing air from the ambient atmosphere, other than exhaust gas, to carbon capture system 108 (e.g., when operating top cycle 102 at a partial load for a normally sized adsorption bed, or when operating top cycle 102 at a full load for an oversized adsorption bed). For example, for a system with a carbon capture system 108 sized based on the carbon dioxide output of top cycle 102, when gas turbine 10 is operating at a partial load, air from the ambient atmosphere may be introduced into carbon capture system 108 via air inlet line 160. Alternatively, for a system with a carbon capture system 108 that is oversized (e.g., sized larger than the carbon dioxide output requirements of gas turbine), when gas turbine 10 is operating at a full load, air from the ambient atmosphere may be introduced into carbon capture system 108 via 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 both the air and the exhaust gas, such that the combustion system produces negative carbon capture emissions. Gas turbine 10 may operate at full load (e.g., maximum capacity or 100%) and partial load (e.g., less than maximum capacity or less than 100%). During full load, gas turbine 10 may produce a large amount of exhaust gas, which may utilize the full carbon dioxide capture capacity of fuel cell 106 and carbon capture system 108. However, under partial load conditions, gas turbine 10 may produce less exhaust gas, thereby giving carbon capture system 108 additional capacity for capturing carbon dioxide. This additional capacity may be used to capture carbon dioxide from the ambient atmosphere, which advantageously allows fuel cell 106 and carbon capture system 108 to capture more than 100% of the carbon dioxide produced in top cycle 102 (e.g., gas turbine 10). For example, all of the carbon dioxide produced in top cycle 102 may be captured jointly by fuel cell 106 and carbon capture system 108, and in addition to the exhaust gas, additional carbon dioxide may be captured from the ambient atmosphere by introducing air from the ambient atmosphere into carbon capture system 108.

[0072] This written description uses examples to disclose the invention, including the best mode, and also enables any person skilled in the art to practice the invention, including making and using any device or system and performing any incorporated method. 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 these other examples include structural elements that are not different from the literal language of the claims, or if they include equivalent structural elements that are not substantially different from the literal language of the claims, then these other examples are intended to be within the scope of the claims.

[0073] Other 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 one of the preceding clauses, wherein between about 85% and about 100% of the pollutants from the exhaust gas leaving the top cycle are jointly captured by the fuel cell and the carbon capture system.

[0085] A method for removing pollutants from a combustion system, the method comprising: operating a top cycle of the combustion system, thereby generating a first power output and exhaust gas; conveying 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] The method according to any one of the preceding clauses, wherein the pollutants include carbon dioxide, wherein the first portion of the pollutants removed from the exhaust gas through the cathode side includes most 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 remaining portion of the carbon dioxide in the exhaust gas.

[0087] The method according to any one of the preceding clauses, 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 remaining portion of the carbon dioxide from the exhaust gas is removed in the carbon capture system.

[0088] The method according to any one of the preceding clauses, wherein the combustion system generates 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.

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

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

[0091] The method according to any one of the preceding clauses, the method further comprising providing air from the ambient atmosphere 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.

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

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

[0094] The combustion system according to any one of the preceding clauses, wherein the carbon capture system includes an adsorption bed.

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

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

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

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

[0099] The carbon capture system according to any one of the preceding clauses, the carbon capture system further comprising an exhaust pipe line fluidly extending between the carbon capture system and an exhaust pipe.

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

[0101] The combustion system according to any one of the preceding clauses, the combustion system 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 one of the preceding clauses, wherein between about 85% and about 100% of the pollutants from the exhaust gas leaving the top cycle are jointly captured by the fuel cell and the carbon capture system.

[0103] A combustion system, the combustion system comprising: a gas turbine including a compressor section, a combustion section, and a turbine section, the turbine section generating exhaust gas; a fuel cell including 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 coupled 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] A combustion system according to any one of the preceding clauses, wherein the carbon capture system includes an adsorption bed.

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

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

[0107] A combustion system according to any one of the preceding clauses, the combustion system 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 one of the preceding clauses, the carbon capture system further comprising an exhaust pipe line fluidly extending between the carbon capture system and the exhaust pipe.

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

[0110] A combustion system according to any one of the preceding clauses, the combustion system 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 one of the preceding clauses, wherein between about 85% and about 100% of the pollutants from the exhaust gas leaving the top cycle are jointly captured by the fuel cell and the carbon capture system.

Claims

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

2. The combustion system according to claim 1, wherein the carbon capture system includes an adsorption bed.

3. The combustion system according to claim 1, the combustion system further including an air inlet line fluidly coupled to the ambient atmosphere and the carbon capture system.

4. The combustion system according to claim 1, wherein the top cycle is a gas turbine coupled to a first load, the gas turbine including a compressor section, a combustion section, and a turbine section, the turbine section generating the exhaust gas.

5. The combustion system according to claim 1, wherein the fuel cell is a molten carbonate fuel cell (MCFC).

6. The combustion system according to claim 1, the combustion system further including a cathode recirculation line extending from the cathode outlet line to the cathode inlet line.

7. The carbon capture system according to claim 1, the carbon capture system further including an exhaust pipe line fluidly extending between the carbon capture system and an exhaust pipe.

8. The combustion system according to claim 1, wherein the anode side receives a fuel stream and / or a steam stream via an anode inlet line.

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

10. The combustion system according to claim 1, wherein between about 85% and about 100% of the pollutants from the exhaust gas leaving the top cycle are captured jointly by the fuel cell and the carbon capture system.

11. A combustion system, the combustion system comprising: A gas turbine that includes a compressor section, a combustion section, and a turbine section, the turbine section generating an exhaust gas; A fuel cell that includes 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 the pollutants from the exhaust gas; A carbon capture system that is fluidly coupled to the fuel cell for removing a second portion of the pollutants from the exhaust gas; and An exhaust gas recirculation line that extends from the exhaust gas outlet line to the compressor section.

12. The combustion system according to claim 11, wherein the carbon capture system includes an adsorption bed.

13. The combustion system according to claim 11, wherein the combustion system further comprises an air inlet line fluidly coupled to the ambient atmosphere and the carbon capture system.

14. The combustion system according to claim 11, wherein the fuel cell is a molten carbonate fuel cell (MCFC).

15. The combustion system according to claim 11, wherein the combustion system further comprises a cathode recirculation line extending from the cathode outlet line to the cathode inlet line.

16. The carbon capture system according to claim 11, wherein the carbon capture system further comprises an exhaust line fluidly extending between the carbon capture system and the exhaust pipe.

17. The combustion system according to claim 11, wherein the anode side receives a fuel stream and / or a steam stream via an anode inlet line.

18. The combustion system according to claim 11, wherein the combustion system further comprises an anode outlet line fluidly coupled to a separation system for removing water and liquid carbon dioxide from the anode output product.

19. The combustion system according to claim 11, wherein between about 85% and about 100% of the pollutants from the exhaust gas leaving the top cycle are captured jointly by the fuel cell and the carbon capture system.

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