COMBUSTION SYSTEM AND CARBON CAPTURE SYSTEM WITH FUEL CELL - Patent application

Abstract

A combustion system is provided. The combustion system includes a topping cycle that generates an exhaust gas flow and a bottoming cycle. The combustion system further includes a heat recovery steam generator (HRSG) that receives exhaust gas from the topping cycle. The HRSG generates a steam flow 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 flow 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.

Description

[Technical Field]

[0001] The present disclosure relates generally 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 technology]

[0002] A gas turbine power plant, such as a combined cycle power plant (CCPP) or 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 through an intake system and is progressively compressed as it is channeled toward a compressor discharge or diffusion casing that at least partially surrounds a combustor in the combustion section. At least a portion of the compressed air is mixed with fuel and combusted in a combustion chamber defined within the combustor, thereby generating high-temperature, high-pressure combustion gases.

[0003] Combustion gases are routed from the combustor along a hot gas path through the turbine, where they gradually expand as they flow across alternating stages of rotatable turbine blades coupled to stationary vanes and 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 may be converted to electrical energy via a generator. The combustion gases exit the turbine as exhaust gases, which enter the HRSG. Thermal energy from the exhaust gases is transferred to water flowing through one or more heat exchangers in the HRSG, thereby generating superheated or supercritical steam. The superheated steam is then routed to a steam turbine where it can be used to generate additional electricity, improving overall power plant efficiency.

[0004] Turbomachinery combustion systems typically burn hydrocarbon fuels, resulting in the production of air-polluting emissions such as nitrogen oxides (NOx), carbon monoxide (CO), and carbon dioxide (CO2). In an effort to reduce emissions, carbon capture systems are utilized to capture CO2 and other air-polluting gases before the turbomachinery gases are discharged into the atmosphere. However, known carbon capture systems are only partially effective and require large amounts of energy.

[0005] Therefore, an improved combined cycle power plant having a carbon capture system that removes pollutants from the emissions without requiring large amounts of electrical power would be desirable and welcome in the art. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] US Patent Application Publication No. 2021 / 0299609 Summary of the Invention

[0007] Aspects and advantages of combined cycle systems and methods according to the present disclosure will be set forth in part in the description that follows, or may be obvious from the description, or may be learned through practice of the present teachings.

[0008] According to one embodiment, a combustion system is provided. The combustion system includes a topping cycle that generates an exhaust gas flow and a bottoming cycle. The combustion system further includes a fuel cell having an anode side, a cathode side, and an electrolyte. The cathode side receives the exhaust gas flow 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 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 flow 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 pollutants from the exhaust gas.

[0009] According to another embodiment, a method for removing pollutants in a combustion system is provided. The method includes operating a topping cycle of the combustion system, thereby producing a first power output and an exhaust gas. The method further includes conveying the exhaust gas through a cathode side of a fuel cell, thereby removing a first portion of the pollutants from the exhaust gas. The method further includes supplying 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.

[0010] According to another embodiment, a combustion system is provided. The combustion system includes a topping cycle that generates a flow of exhaust gas and a bottoming cycle. The combustion system further includes a heat recovery steam generator (HRSG) that receives exhaust gas from the topping cycle. The HRSG generates a flow of steam for use in the bottoming cycle. The fuel cell includes an anode side, a cathode side, and an electrolyte. The cathode side receives the flow of exhaust gas 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.

[0011] 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. The 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.

[0012] These and other features, aspects, and advantages of the present combustion systems and methods 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 technology and, together with the description, serve to explain the principles of the technology.

[0013] A full and enabling disclosure of the present combustion system and method, including the best mode of making and using the same, directed to one skilled in the art, is set forth in this specification, which makes reference to the accompanying drawings. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram of a combustion system according to an embodiment of the present disclosure. [Figure 2] 1 is a schematic diagram of a combustion system according to an embodiment of the present disclosure. [Figure 3] FIG. 1 is a flow diagram of a method for removing pollutants in a combustion system according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0015] Reference will now be made in detail to embodiments of the present combustion systems and methods, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the present technology, not limitation thereof. Indeed, it will be apparent to those skilled in the art that modifications and variations can be made in the present technology without departing from the scope or spirit of the claimed technology. For example, features illustrated or described as part of one embodiment can be used with another embodiment to yield yet a further embodiment. Accordingly, it is intended that the present disclosure cover such modifications and variations as come within the scope of the appended claims and their equivalents.

[0016] 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. Moreover, unless otherwise specified, all embodiments described herein should be considered exemplary.

[0017] The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description are used to refer to like or similar parts of the invention. As used herein, the terms "first," "second," and "third" may be used interchangeably to distinguish one component from another and do not denote the location or importance of the individual components.

[0018] The term "fluid" may be a gas or a liquid. The term "fluid communication" means that a fluid is capable of making a connection between designated areas.

[0019] As used herein, the terms "upstream" (or "forward") and "downstream" (or "aft") refer to relative directions with respect to fluid flow in a fluid pathway. For example, "upstream" refers to the direction from which fluid flows, and "downstream" refers to the direction from which fluid flows. However, as used herein, the terms "upstream" and "downstream" can also refer to electrical flow. The term "radially" refers to relative directions that are substantially perpendicular to the axial centerline of a particular component, the term "axially" refers to relative directions that are substantially parallel and / or coaxially aligned with the axial centerline of a particular component, and the term "circumferentially" refers to relative directions that extend around the axial centerline of a particular component.

[0020] Approximate terms such as "about," "approximately," "generally," and "substantially" are not limited to the exact value specified. In at least some cases, approximate language may correspond to the precision of an instrument for measuring a value or the precision of a method or machine for constructing or manufacturing a component and / or system. For example, approximate language may refer to within a margin of 1, 2, 4, 5, 10, 15, or 20% of an individual value, a range of values, and / or any of the endpoints defining the range of values. When used in the context of an angle or direction, such terms include a range of 10 degrees greater or less than the stated angle or direction. For example, "generally vertical" includes any direction, e.g., clockwise or counterclockwise, within 10 degrees of vertical.

[0021] Terms such as "coupled," "fixed," and "attached," unless otherwise specified herein, refer to both direct coupling, fixing, or attachment, and indirect coupling, fixing, or attachment via one or more intermediate components or features. As used herein, the terms "comprises," "comprising," "includes," "including," "has," and "having," 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 only those features and 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, not an exclusive or. For example, 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).

[0022] Herein, throughout the specification and claims, range limitations are combinable and interchangeable, and unless the context and language dictate otherwise, such ranges are identified and include all subranges subsumed therein. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other.

[0023] As used herein, the term "line" may refer to a pipe, hose, tube, duct, or other fluid-carrying conduit.

[0024] Referring now to the drawings, FIGS. 1 and 2 each show a schematic diagram of an embodiment of a combustion or combined cycle system 100 including a topping cycle 102 and a bottoming cycle 104. In the topping cycle 102, fuel is combusted to generate electrical or mechanical power, resulting in exhaust gases 34 containing carbon dioxide. In the bottoming cycle 104, the exhaust gases 34 from the topping cycle 102 may then be used to generate additional electrical or mechanical power. In various embodiments, the topping cycle 102 may be an internal combustion engine, an industrial process in which fuel is combusted, or the like. In some embodiments, the bottoming cycle 104 may be a heat exchanger, a boiler, a supercritical CO2 cycle, a superheater, an evaporator, a pump, or the like. In an exemplary embodiment, the topping cycle 102 may be a gas turbine 10, and the bottoming cycle 104 may be a steam turbine system 22, as shown.

[0025] The combined cycle system 100 may include a gas turbine 10 for driving a first load 14. The first load 14 may be, for example, a generator for generating electrical power. 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 supply 15 may supply fuel to a combustor in the combustion section 18. The combustor fuel supply 15 may supply natural gas, such as a hydrocarbon fuel, which may include methane, propane, etc., to the combustion section 18. In an exemplary embodiment, the combustor fuel supply 15 may supply methane (CH4) to the combustion section 18. Additionally or alternatively, the combustor fuel supply 15 may supply a liquid fuel, such as diesel, crude oil, or syngas, to the combustor.

[0026] During operation of the gas turbine 10, a working fluid, such as air 171, enters the compressor section 20, where it is progressively compressed, thus providing compressed air to the combustors in the combustion section 18. The compressed air is mixed with fuel and burned in each combustor to generate combustion gases. The combustion gases pass through a hot gas path from the combustion section 18 to the turbine section 16, where energy (kinetic and / or thermal energy) is transferred from the combustion gases to rotor blades, thereby rotating one or more shafts 21. The mechanical rotational energy may then be used to power the compressor section 20 and / or generate electricity.

[0027] The heated exhaust gas 34 exiting the turbine section 16 then leaves the gas turbine 10 and is routed first through the fuel cell 106 to a heat recovery steam generator (HRSG) 32, where a first portion of pollutants (e.g., CO) are removed from the exhaust gas 34. For example, in some embodiments, as shown in FIG. 2, the exhaust gas 34 may be routed first through the HRSG 32 before entering the fuel cell 106. In such embodiments where the exhaust gas 34 is routed first through the HRSG 32 before entering the fuel cell 106, the exhaust gas is 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 should be between about 500°C and about 650°C. Therefore, a heat exchanger 180 may be disposed in the cathode inlet line 118 to preheat the exhaust gas 34 before entering the cathode side 116. The heat exchanger 180 may be disposed in thermal communication with 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 thermal fluid. For example, the heat exchanger 180 may be in fluid communication with the cathode outlet line 146. After passing through the heat exchanger 180, the cathode output product may be supplied 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 in 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 either natural gas (e.g., from the fuel supply 15) or the anode output product.

[0028] 1, the exhaust gas 34 may first be routed through a fuel cell 106 before entering the HRSG 32. In the HRSG 32, heat transfer occurs between the exhaust gas 34 and various components of the HRSG 32 to generate steam that is supplied to the steam turbine system 22. The exhaust gas 34 may then be routed to a carbon capture system 108, such as an adsorption bed, where a second portion (e.g., remainder) of the pollutants (e.g., CO) is removed from the exhaust gas. Finally, the exhaust gas 34 may exit the carbon capture system 108 to the atmosphere via an exhaust stack 110.

[0029] Upon exiting the turbine section 16, the exhaust gas 34 may contain mostly nitrogen (N), carbon dioxide (CO), oxygen (O), and water (HO). Additionally, the exhaust gas 34 may contain trace amounts of carbon monoxide (CO), nitrogen oxides (NOx), sulfur oxides (SOx), and / or argon (Ar). In an exemplary implementation of the combined cycle system 100, a first portion of the carbon dioxide (CO) may be removed from the exhaust gas 34 in the fuel cell 106, and a second portion of the carbon dioxide (CO) may be removed from the exhaust gas 34 in a further carbon capture system 108 (e.g., an adsorption bed). In many embodiments, the second portion of the CO removed in the carbon capture system 108 may be the remainder of the CO in the exhaust gas 34, such that all (e.g., 100%) of the CO may be removed from the exhaust gas 34 before being discharged via the exhaust stack 110.

[0030] The combined cycle system 100 may also include a steam turbine system 22 for driving a second load 24. The second load 24 may be a generator for generating electrical power. 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, while 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 tandem to drive a single load via a single shaft.

[0031] In the illustrated embodiment, 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. Low-pressure (LP) steam turbine 26, intermediate-pressure (IP) steam turbine 28, high-pressure (HP) steam turbine 30, and load 24 may each be disposed on one or more shafts 23 (such as a common shaft in some embodiments).

[0032] In an exemplary embodiment, the fuel cell 106 may include an anode side 112, a cathode side 116, and an electrolyte 114 (capable of conducting charged ions). The fuel cell 106 can directly convert 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 internal reforming MCFC and / or an external reforming MCFC. In such an embodiment, the electrolyte 114 may be a molten carbonate mixture suspended within a porous, chemically inert ceramic matrix of beta-alumina solid electrolyte (BASE). An MCFC may operate by passing a reactive fuel gas (e.g., natural gas) through the anode side 112 while passing an oxidizing gas (e.g., exhaust gas containing carbon dioxide along with oxygen) through the cathode side 116, whereby an electrochemical reaction occurs across the electrolyte 114, consuming (or chemically converting) carbon dioxide and producing electricity. In particular, in the cathode side 116, oxygen and carbon dioxide are converted into carbonate ions (CO3 2- )

[0033] As briefly mentioned above, the fuel cell 106 converts the anode fuel stream and the exhaust gas into electrical energy while removing CO from the exhaust gas (e.g., CO 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 convert the DC current to an AC current that can be effectively utilized by one or more subsystems. In particular, for the depicted 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 fuel cell 106, the carbon capture system 108, or the like. The electrical bus 124 is in electrical communication with one or more additional electrical devices 122, which may be an electrical power source, a power sink, or both. For example, the additional electrical device 122 may be an electrical storage device (such as one or more batteries), an electrical machine (a generator, an electric motor, or both). Alternatively or additionally, the power output 120 may be useful for driving the first load 14 and / or the second load 24. The combined cycle system 100 may generate a total power output (e.g., the sum of the power output 120 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.

[0034] In many embodiments, the cathode side 116 may be fluidly coupled (e.g., directly fluidly coupled) to the gas turbine 10 via a 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. In particular, the cathode side 116 may 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 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 the exemplary embodiment, all of the exhaust gas 34 from the outlet of the turbine section 16 may be routed through the cathode side 116 of the fuel cell 106 to remove a first portion of pollutants (e.g., CO) from the exhaust gas 34 (i.e., no branch line may extend from the cathode inlet line 118). In an optional embodiment, as shown in FIG. 1 , a fan or blower 157 may be included in the cathode inlet line 118. The fan 157 may 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 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.

[0035] In various embodiments, the anode side 112 can receive a flow of fuel and / or steam via an anode inlet line 126. The fuel and steam may be transported through the anode side 112. The anode inlet line 126 can fluidly couple the anode side 112 to an anode fuel supply 128. In some embodiments, the anode fuel supply 128 can be the same as the combustor fuel supply 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 supply 128 and the combustor fuel supply 15 can be different. In many implementations, the anode fuel supply 128 can supply natural gas (e.g., a hydrocarbon fuel) to the anode side 112 via the anode inlet line 126. The natural gas may include methane, propane, etc. In an exemplary embodiment, the anode fuel supply 128 can supply methane (CH4) to the anode side 112. A fuel preheater 130, such as a heat exchanger, may be disposed in thermal communication with the anode inlet line 126. The fuel preheater 130 may heat the fuel before it enters the anode side 112 of the fuel cell 106, thereby advantageously increasing the efficiency of the fuel cell 106.

[0036] In the exemplary embodiment, combined cycle system 100 may include an anode steam supply line 188. The anode steam supply line 188 may extend between heat exchanger 136 and anode inlet line 126. Steam may be generated by heat from the anode output product in heat exchanger 136 and supplied to anode inlet line 126. The anode steam supply line 188 may provide a flow of steam to 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 HRSG 32, such that HRSG 32 supplies steam to both steam turbine system 22 and the anode side 112 of the fuel cell 106.

[0037] 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 products from the anode side 112 after the electrochemical reaction in the fuel cell 106. In certain embodiments, the anode output products may include CO, CO, H, water, and unused CH (e.g., methane not utilized in the fuel cell 106 during the electrochemical reaction). The anode output product may be provided to a separation system 134 that may remove water and liquefied CO from the anode output product.

[0038] The separation system 134 may include, in serial flow order (e.g., from upstream to downstream), a heat exchanger 136, a water flash separator 138, a compressor 140, a chiller 142, and a liquid carbon dioxide separator 144. 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 entering the water flash separator 138, which produces steam at a steam inlet line 188 for use at the inlet of the anode side to maintain a desired steam-to-carbon molar ratio (which may be about 1.5 to about 5, or particularly about 2 to about 3). A water flash inlet line 137 may extend between and fluidly couple the heat exchanger 136 and the water flash separator 138. The water flash separator 138 may remove any water from the anode output product. For example, water in the anode output product may 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 may be passed through a water-gas shift reactor to convert carbon monoxide to hydrogen. In such embodiments, the water-gas shift reactor may be located between the heat exchanger 136 and the water flash separator 138.

[0039] In many embodiments, a compressor inlet line 139 may extend between and fluidly couple the water flash separator 138 and the compressor 140. The compressor 140 may compress the anode output product and supply the compressed anode output product to the chiller 142 via a chiller inlet line 141. The chiller 142 may liquefy the CO2 in the compressed anode output product by reducing the temperature of the compressed anode output product. The liquid CO2 may then be removed via a liquid carbon dioxide separator 144. The removed liquid carbon dioxide may be sent to carbon sequestration or carbon utilization. For example, the chiller 142 may be fluidly coupled to the liquid carbon dioxide separator 144 via a connecting line 143.

[0040] The anode recycle 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 recycle 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 (with water and liquid carbon dioxide removed) to the anode side 112. For example, the anode recycle line 145 may advantageously reintroduce any unused methane and excess hydrogen to the anode side 112 for electrochemical conversion.

[0041] 1 , the HRSG 32 may be located 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 an outlet of the cathode side 116 of the fuel cell 106. The HRSG 32 may generate a flow of steam for use in the bottoming cycle 104. For example, a cathode outlet line 146 may extend between and fluidly couple the outlet of the cathode side 116 and the HRSG 32. The HRSG 32 may generate steam from heat from the exhaust gases exiting the cathode side 116, and the steam may be supplied to the steam turbine system 22.

[0042] 2, the HRSG 32 may be located upstream of the cathode side 116. In such embodiments, the HRSG 32 may be fluidly coupled (e.g., directly fluidly coupled in some embodiments) to an outlet of the turbine section 16. The HRSG 32 may generate a flow of steam for use in the bottoming cycle 104. The HRSG 32 may generate steam from heat from the exhaust gases exiting the turbine section 16, and the steam may be supplied to the steam turbine system 22.

[0043] A steam supply line 148 may extend from the HRSG 32 to the steam turbine system 22. In particular, the steam supply line 148 may extend from the HRSG 32 to the HP steam turbine 30. An outlet of the HP steam turbine 30 may be fluidly coupled to an inlet of the IP steam turbine 28, which may be fluidly coupled to an 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 within the HRSG, be superheated, and then returned to the inlet of the IP steam turbine 28. An 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 to water, which may be returned to the HRSG 32 via a condensate return line 151.

[0044] In certain embodiments, the combined cycle system 100 may further include a cathode recirculation line 168 that extends from the cathode outlet line 146 to and fluidly couples the cathode inlet line 118. For example, the cathode recirculation line 168 may fluidly extend between an inlet disposed in 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 disposed in the cathode inlet line 118. The cathode recirculation line may reintroduce any unreacted CO2 into the cathode side 116 for further reaction / removal from the exhaust gas.

[0045] In many embodiments, a carbon capture system 108, such as a sorbent-based carbon capture system, may 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, as shown in FIG. 1. In particular, the carbon capture system may be fluidly coupled to the outlet of the HRSG 32 via an HRSG outlet line 154. The HRSG outlet line 154 may convey exhaust gas from the outlet of the HRSG 32 to the carbon capture system 108. In exemplary embodiments, the carbon capture system 108 may include an adsorption bed 156 that removes a second portion of the pollutants (e.g., CO) from the exhaust gas. In particular, the adsorption bed 156 may remove the remainder of the CO from the exhaust gas, such that all of the CO is removed from the exhaust gas before it exits the exhaust stack 110. Furthermore, in some embodiments, as shown in FIG. 1, 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, a direct contact cooler 155 may be located in the HRSG outlet line 154 upstream of the carbon capture system 108. The direct contact cooler 155 may spray water (or other suitable coolant) into the exhaust gases, thereby cooling the temperature of the exhaust gases before they enter the carbon capture system 108.

[0046] 2, the carbon capture system 108 may be fluidly coupled (e.g., directly fluidly coupled) to the outlet of the cathode side 116 via the cathode outlet line 146. In such an embodiment, the cathode outlet line 146 may extend between and fluidly couple the cathode side 116 and the carbon capture system 108. The cathode outlet line 146 may convey exhaust gas from the outlet of the cathode side 116 to the carbon capture system 108.

[0047] Although the exemplary embodiment of the carbon capture system 108 includes an adsorption bed 156, the carbon capture system 108 may apply a variety of techniques to separate the remaining carbon dioxide from the exhaust gas, including, but not limited to, pressure swing adsorption, temperature swing adsorption, rapid thermal swing adsorption, vacuum temperature swing adsorption, chemical adsorption, cryogenic separation, and membrane separation.

[0048] In various embodiments, the carbon capture system 108 can use pressure swing adsorption (PSA). PSA may be used to separate carbon dioxide from a mixture of gases. In the PSA technique, at high partial pressures, solid molecular sieves can adsorb carbon dioxide. As a result, at high pressures, carbon dioxide is removed from the gas mixture as it passes through the adsorption bed. Bed regeneration is achieved by depressurization and purging. Typically, for critical operations, multiple adsorption vessels are used for continuous carbon dioxide separation, with one adsorption bed being used and the others being regenerated.

[0049] In an exemplary embodiment, the carbon capture system 108 can use temperature swing adsorption (TSA). In TSA, an adsorbent adsorbs CO from the cathode output product at low temperatures (preferably between cryogenic temperatures down to less than 60°C). The saturated adsorption bed then undergoes desorption by increasing the temperature (typically above 100°C). Desorption can occur under vacuum conditions or with the presence of a sweep gas to reduce the partial pressure of the CO. The heat required for desorption can be provided by steam from a low-pressure steam turbine. Finally, the adsorption bed is cooled to an initial temperature so that the bed is ready for the next adsorption cycle.

[0050] In certain embodiments, the carbon capture system 108 can separate carbon dioxide from the exhaust gas by chemical adsorption using oxides such as calcium oxide (CaO) and magnesium oxide (MgO) or a combination thereof. In one embodiment, at high pressure and temperature, CO2 is adsorbed by CaO to form calcium carbonate (CaCO3), thereby removing CO2 from the gas mixture. The adsorbent CaO can be regenerated by calcining the CaCO3, which can again reform CaCO3 back into CaO.

[0051] In some embodiments, membrane separation techniques 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 that are selective for CO. Membrane separators function more efficiently at higher pressures, and separating carbon dioxide from the exhaust gas using a membrane separator may be achieved with further compression (e.g., by one or more compressors upstream of the carbon capture system 108).

[0052] In other embodiments, another technique that may be used by the carbon capture system 108 for separation of CO from the exhaust gas may include, but is not limited to, amine-based CO chemisorption. The exhaust gas may be cooled to a temperature suitable for using amine-based carbon dioxide chemisorption. This technique is based on alkanolamine solvents, which have the ability to adsorb carbon dioxide at relatively low temperatures and are easily regenerated by increasing the temperature of the rich solvent. A carbon dioxide-rich stream is obtained after regeneration of the rich solvent. Solvents used in this technique may include pure or mixtures of triethanolamine, monoethanolamine, diethanolamine, diisopropanolamine, diglycolamine, and piperazine.

[0053] In some other embodiments, the carbon capture system may include at least one absorption vessel in which chemical absorption techniques are used. In yet another embodiment, the carbon dioxide separator includes at least one membrane separator.

[0054] In an exemplary embodiment, the carbon capture system may include at least one adsorbent bed 156, in which TSA techniques may be used to separate carbon dioxide from the outlet stream exhaust gas. In particular, in an exemplary embodiment, the carbon capture system 108 may include multiple adsorbent beds 156 (e.g., about 10 to about 500 adsorbent beds, or, for example, about 10 to about 400 adsorbent beds, or, for example, about 30 to about 250 adsorbent beds, or, for example, about 10 to about 100 adsorbent beds). During operation, some adsorbent beds 156 undergo adsorption, some adsorbent beds 156 may undergo desorption, while the remaining adsorbent beds undergo cooling for the temperature swing adsorption process. Under partial load, only some of the adsorbent beds need be operational, as the CO flow rate in the exhaust gas (or cathode output product) decreases, putting other adsorbent beds 156 on standby. Ambient air can be supplied to these standby adsorbent beds 156 to adsorb additional CO from the atmosphere, thereby achieving negative system emissions. Alternatively or additionally, several additional adsorbent beds can be added that can function as a direct air capture system, receiving steam from the steam turbine for desorption. In this way, negative carbon emissions may be achieved during normal full load conditions.

[0055] In other embodiments, the adsorbent bed 156 may be a direct contact adsorbent bed. A direct contact adsorbent bed comprises one large rotating bed containing many segments undergoing different processes. In such embodiments, the carbon capture system 108 may comprise from about 1 to about 100 direct contact adsorbent beds.

[0056] For example, the combined cycle system 100 may further include an air inlet line 160 fluidly coupled to the atmosphere (or ambient environment) and the carbon capture system 108. In particular, 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 further 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 operable between an open position (allowing air to flow therethrough) and a closed position (restricting or preventing the passage of air). The valve 164 may be downstream of the pump 162. The pump 162 may create a pressure differential that draws air from the atmosphere when the pump is operating. The air from the atmosphere may pass through the carbon capture system 108 (e.g., the adsorption beds 156) to remove contaminants (e.g., CO) present in the air. This advantageously allows the combined cycle system 100 to have negative carbon dioxide emissions, as all (e.g., 100%) of the carbon dioxide 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 via the air inlet line 160 for further atmospheric carbon dioxide removal.

[0057] 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.

[0058] 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 stack 110. In particular, the exhaust line 166 may extend between the outlet of the adsorption bed 156 and the exhaust stack 110. The exhaust stack 110 may discharge the exhaust gas (with pollutants removed) to the atmosphere.

[0059] As described above, the fuel cell 106 and the carbon capture system 108 can collectively remove all of the pollutants (e.g., carbon dioxide) from the exhaust gas exiting the topping cycle 102 before discharging the exhaust gas to the atmosphere via the exhaust stack 110. For example, about 85% to about 100% of the pollutants from the exhaust gas exiting the topping cycle 102 can be collectively captured 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 remainder of the carbon dioxide from the exhaust gas. In particular, about 50% to about 90% of the carbon dioxide from the exhaust gas can be removed in the fuel cell 106 when exhaust gas recirculation is implemented, or about 75% to about 85%, etc. can be removed in the fuel cell 106 without exhaust gas recirculation. While more carbon dioxide may be removed within the fuel cell 106, this is not possible without unduly stressing the fuel cell 106, shortening its lifespan, and reducing its electrical efficiency (i.e., the ratio between the electricity generated from the fuel cell and the fuel energy supplied at the anode). Therefore, operating the fuel cell 106 to remove about 75% to about 85% of the carbon dioxide from the exhaust gas advantageously preserves the lifespan and enables efficient operation of the fuel cell 106. The remainder of the carbon dioxide in the exhaust gas exiting the turbine section 16, e.g., about 10% to about 30% of the carbon dioxide in the exhaust gas (or, such as, about 15% to about 25% of the carbon dioxide in the exhaust gas), may be removed by the carbon capture system 108 (e.g., adsorption bed 156 in an exemplary embodiment).

[0060] As mentioned above, in some embodiments, as shown in FIG. 1 , 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 embodiments, the cathode outlet line 146 may supply the exhaust gas (or cathode output products) to the HRSG 32, and the HRSG outlet line 154 may supply the exhaust gas to the carbon capture system 108. Alternatively, as shown in FIG. 2 , the HRSG 32 may be positioned upstream of the cathode side 116. In such embodiments, the HRSG 32 may receive the exhaust gas from the exhaust gas outlet line 117. The exhaust gas may then be supplied to the cathode side 116 via the cathode inlet line 118. Furthermore, as shown in FIG. 2 , when the HRSG 32 is positioned upstream of the fuel cell 106, the cathode output products may be supplied directly to the carbon capture system 108 (e.g., via the cathode outlet line 146).

[0061] In many embodiments, as shown in FIGS. 1 and 2 , the combined cycle system 100 may include an exhaust gas recirculation line 170 fluidly coupling the turbine section 16 to the compressor section 20, such that exhaust gas from the outlet of the turbine section 16 is supplied 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 embodiments, the compressor 20 may receive ambient air 171 as well as recirculated exhaust gas. When exhaust gas recirculation is implemented, the CO mole percent in the gas turbine exhaust gas increases from about 4.3% to about 8%, thereby enabling the fuel cell 106 to operate at a higher efficiency. For example, exhaust gas recirculation may enable the fuel cell 106 to remove up to 90% of the CO from the exhaust gas. The exhaust gas recirculation line 170 selectively returns a portion of the exhaust gas from the exhaust gas outlet line 117 to the inlet of the compressor section 20. For example, a valve 172 may be disposed in exhaust gas recirculation line 170. Valve 172 may be selectively actuated between an open position (allowing exhaust gas recirculation) and a closed position (restricting or preventing exhaust gas recirculation). Further, in the exemplary embodiment, an exhaust gas cooler 174 may be disposed in exhaust gas recirculation line 170. Exhaust gas cooler 174 may be a heat exchanger that cools the exhaust gas in exhaust gas recirculation line 170 to meet inlet temperature requirements for gas turbine 10.

[0062] Referring now to FIG. 3 , a flow diagram of one embodiment of a method 200 for removing contaminants in a combined cycle system is shown in accordance with an aspect of the present subject matter. Generally, the method 200 is described herein with reference to the combined cycle system 100 described above with reference to FIGS. 1 and 2 . However, it will be understood by those skilled in the art that the disclosed method 200 may generally be utilized with any suitable combined cycle system and / or may be utilized in connection with a system having any other suitable system configuration. Additionally, while FIG. 3 depicts steps performed in a particular order for purposes of illustration and explanation, the methods described herein are not limited to any particular order or arrangement unless otherwise specified in the claims. Those skilled in the art, using the disclosure provided herein, will understand that various steps of the methods disclosed herein may be omitted, rearranged, combined, and / or adapted in various ways without departing from the scope of the present disclosure.

[0063] As shown, the method 200 includes, at 202, operating the topping cycle 102 of the combined cycle system 100, thereby generating a first power output and exhaust gases. For example, operating the topping cycle 102 may include operating the gas turbine 10 at a partial load or a full load. As a result, the first power output and exhaust gases are generated. The first power output may be generated by a first load 14. The first load 14 may be, for example, 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 routed through a turbine section 16 and emitted as exhaust gases that may include pollutants such as carbon dioxide.

[0064] In an exemplary implementation, as shown, the method 200 further includes, at 204, conveying the exhaust gas through the cathode side 116 of the fuel cell 106, thereby removing a first portion of the pollutants from the exhaust gas. For example, an electrochemical reaction may occur within the fuel cell 106 to remove carbon dioxide from the exhaust gas and generate electricity, which may be supplied 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. An MCFC may operate by passing a reactive fuel gas (e.g., natural gas mixed with steam) through the anode side 112 while passing an oxidizing gas (e.g., exhaust gas containing carbon dioxide and oxygen) through the cathode side 116, whereby an electrochemical reaction occurs across the electrolyte 114, removing (or chemically converting) carbon dioxide and producing electricity and hydrogen.

[0065] In many implementations, as shown, the method 200 may further include, at 206, supplying the exhaust gas from the cathode outlet (i.e., the cathode output product) to a carbon capture system 108. A second portion of the contaminants (e.g., carbon dioxide) is removed from the exhaust gas as it passes through the carbon capture system 108. For example, the carbon capture system 108 may be an adsorption bed 156 that removes the remainder of the carbon dioxide from the exhaust gas downstream of the fuel cell 106.

[0066] For example, the pollutants may be carbon dioxide, and the first portion of the pollutants 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 as it exits the gas turbine 10. Thus, the second portion of the pollutants removed from the exhaust gas by the carbon capture system 108 may be the remainder of the carbon dioxide in the exhaust gas. In particular, 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 of the carbon dioxide (e.g., approximately 15%) may be removed by the carbon capture system 108 before being discharged from the exhaust stack 110. For example, approximately 85% to approximately 100% of the pollutants from the exhaust gas exiting the topping cycle 102 may be collectively captured by the fuel cell 106 and the carbon capture system 108 (e.g., adsorption bed 156). The fuel cell 106 may remove a 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. In particular, about 70% to about 90%, or about 75% to about 85%, etc., of the carbon dioxide from the exhaust gas may be removed in the fuel cell 106. While more carbon dioxide may be removed in the fuel cell 106, this is not possible without unduly stressing the fuel cell 106, shortening its lifespan, and reducing its efficiency. Therefore, operating the fuel cell 106 to remove about 50% to about 85% of the carbon dioxide from the exhaust gas (or about 50% to about 90%, etc., when exhaust gas recirculation is implemented) advantageously preserves the lifespan and enables efficient operation of the fuel cell 106. The remainder of the carbon dioxide in the exhaust gas exiting the turbine section 16, for example, about 15% to about 50% (or about 15% to about 25%, etc.) of the exhaust gas, may be removed by the carbon capture system 108 (e.g., adsorption bed 156 in an exemplary embodiment).

[0067] In many implementations, the combined cycle system 100 can generate 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 embodiment, operating the fuel cell 106 and carbon capture system 108 may require a power source of about 0.5% to about 5% (or about 3% to about 5%, etc.) of the total power output. As discussed above, the fuel cell 106 may be capable of more aggressive operation, in which more than 85-90% of the carbon dioxide is captured within the fuel cell 106, but this significantly increases contributions from loss mechanisms such as cathode polarization (which is the dominant resistance due to the low concentration of carbon dioxide), ohmic resistance, anode polarization, and activation losses. This reduces the overall plant efficiency, or the 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., adsorption bed 156 in the exemplary embodiment) advantageously requires only about 3% to about 5% of the total power output of the combined cycle system 100 to achieve a 100% carbon capture rate, which is lower than other designs, because the specific energy required to capture CO (MJ / kg of captured CO) increases monotonically as the carbon capture rate increases. Furthermore, the integration of the fuel cell 106 (such as an MCFC) generates about 20% to 25% additional power, thereby increasing the net power output of the plant, while all other carbon capture technologies consume energy, thereby reducing the net power output from the plant. A fuel cell 106 (e.g., an MCFC) can generate approximately 20% to 25% excess power (assuming a carbon capture rate of approximately 85%) (a lower range of excess power may be approximately 10% if the carbon capture rate is reduced to approximately 50%), but it also consumes fuel to do so. Increasing the CO2 capture rate from the fuel cell 106 increases losses within the fuel cell 106, thus reducing the fuel-to-electricity conversion efficiency to the electrical efficiency of the fuel cell 106, thereby making power generation from the fuel cell 106 relatively less efficient compared to power generation from a combined cycle power plant.Additionally, the separation system 134 consumes parasitic loads that contribute to a reduction in overall plant efficiency of more than about 2%, which may increase as the carbon capture rate in the fuel cell 106 increases. In implementations where the carbon capture rate in the fuel cell 106 decreases to about 50%, the reduction in overall plant efficiency may be about 1%.

[0068] The maximum CO2 capture limit of a fuel cell 106 (such as an MCFC) varies as a function of the CO2 concentration in the exhaust gas. The gas turbine 10 typically emits an exhaust gas 34 containing approximately 5% molar CO2. When exhaust gas recirculation is implemented, the %molar increases to approximately 8% molar CO2, thereby increasing the maximum CO2 capture by the fuel cell 106 to approximately 85% to approximately 90%. Other processes, such as industrial processes, may have exhaust gases with high CO2 concentrations (e.g., cement plant exhaust has approximately 30% molar CO2). In such implementations, when the fuel cell is fed exhaust gas from an industrial process (such as a cement plant or coal plant) with a high %molar CO2, the fuel cell can achieve a higher capture rate (such as a carbon capture rate of over 90%).

[0069] In any implementation, as indicated by the dashed box, the method 200 may include conveying the exhaust gas from the outlet of the cathode side 116 through a heat recovery steam generator 32 (HRSG) at 208 before supplying 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 supplying 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 power. The second load 24 may be a generator to generate power.

[0070] In some embodiments, the method 200 may include, at 214, supplying air from the atmosphere to the carbon capture system 108 in addition to the exhaust gas (e.g., when the topping cycle 102 operates at part-load for a normally sized adsorbent bed or when the topping cycle 102 operates at full-load for an oversized adsorbent bed). For example, air from the atmosphere may be introduced to the carbon capture system 108 via the air inlet line 160 when the gas turbine 10 is operating at part-load for a system having a carbon capture system 108 sized based on the carbon dioxide output of the topping cycle 102. Alternatively, air from the atmosphere may be introduced to the carbon capture system 108 via the air inlet line 160 when the gas turbine 10 is operating at full-load for a system having an oversized carbon capture system 108 (e.g., sized greater than the carbon dioxide output requirements of the gas turbine). As a result of supplying air in addition to the exhaust gas from the gas turbine, carbon dioxide is removed from the air and the exhaust gas such that the combustion system produces negative carbon capture emissions. The gas turbine 10 may be capable of operating 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, which is able to utilize the full carbon dioxide capture capacity of the fuel cell 106 and carbon capture system 108, can produce large amounts of exhaust gas. However, at part load conditions, the gas turbine 10 may produce less exhaust gas, thereby providing the carbon capture system 108 with additional capacity to capture carbon dioxide. This additional capacity may be utilized to capture carbon dioxide from the atmosphere, thereby advantageously enabling the fuel cell 106 and 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 may be captured collectively by the fuel cell 106 and the carbon capture system 108, and additional carbon dioxide may be captured from the atmosphere by introducing air from the atmosphere into the carbon capture system 108 in addition to the exhaust gases.

[0071] 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 device or system and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they contain structural elements that do not differ from the literal language of the claims, or if they contain equivalent structural elements that differ only insignificantly from the literal language of the claims.

[0072] Further aspects of the invention are provided by the subject matter of the following clauses.

[0073] 1. A combustion system comprising: a topping cycle that generates an exhaust gas stream; a bottoming cycle; a fuel cell including 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) receiving the exhaust gas from the cathode side via a cathode outlet line, the HRSG generating a steam stream for use in the bottoming cycle; and a carbon capture system fluidly coupled to the HRSG via the HRSG outlet line, the carbon capture system removing a second portion of pollutants from the exhaust gas.

[0074] The combustion system of any preceding clause, wherein the carbon capture system comprises an adsorbent bed.

[0075] The combustion system of any preceding clause, further comprising an air inlet line fluidly coupled to the atmosphere and to the carbon capture system.

[0076] The combustion system of any preceding clause, 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 exhaust gases.

[0077] 10. The combustion system of any preceding clause, further comprising an exhaust gas recirculation line fluidly coupling the turbine section to the compressor section.

[0078] 10. The combustion system of any preceding clause, wherein the fuel cell is a molten carbonate fuel cell (MCFC).

[0079] 10. The combustion system of any preceding clause, further comprising a cathode recirculation line extending from the cathode outlet line to the cathode inlet line.

[0080] 10. The combustion system of any preceding clause, further comprising an exhaust line fluidly extending between the carbon capture system and the exhaust stack.

[0081] The combustion system of any preceding clause, wherein the anode side receives a flow of fuel and / or steam via an anode inlet line.

[0082] 10. The combustion system of any preceding clause, further comprising an anode outlet line fluidly coupled to a separation system for removing water and liquid carbon dioxide from the anode output product.

[0083] The combustion system of any preceding clause, wherein about 85% to about 100% of pollutants from the exhaust gas exiting the topping cycle are collectively captured by the fuel cell and carbon capture system.

[0084] 1. A method for removing pollutants in a combustion system, the method including: operating a topping cycle of the combustion system, thereby producing a first power output and an exhaust gas; conveying the exhaust gas through a cathode side of a fuel cell, thereby removing a first portion of pollutants from the exhaust gas; and supplying 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.

[0085] The method of any of the preceding clauses, wherein the pollutants include carbon dioxide, and wherein a 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 a 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.

[0086] The method of any preceding clause, wherein the pollutants include carbon dioxide, and wherein about 50% to about 90% of the carbon dioxide from the exhaust gas is removed at the cathode side of the fuel cell, and the remainder of the carbon dioxide from the exhaust gas is removed in a carbon capture system.

[0087] The method of any preceding clause, wherein the combustion system produces a total power output and operating the fuel cell and carbon capture system requires a power source that is between about 0.5% and about 5% of the total power output.

[0088] The method of any preceding clause, further comprising conveying the exhaust gas from the cathode side outlet through a heat recovery steam generator (HRSG) before supplying the exhaust gas to the carbon capture system.

[0089] 10. The method of any preceding clause, further comprising generating steam with the HRSG and supplying the steam to a bottoming cycle of the combustion system, the bottoming cycle producing a second electrical power output.

[0090] 10. The method of any preceding clause, further comprising supplying air from the atmosphere in addition to the exhaust gas to the carbon capture system, whereby carbon dioxide is removed from the air such that the combustion system produces negative carbon capture emissions.

[0091] The method of any preceding clause, further comprising conveying fuel and / or steam through the anode side of the fuel cell.

[0092] 1. A combustion system comprising: a topping cycle that generates a stream of exhaust gas; a bottoming cycle; a heat recovery steam generator (HRSG) that receives exhaust gas from the topping cycle, the HRSG generating a stream of steam for use in the bottoming cycle; a fuel cell including an anode side, a cathode side, and an electrolyte, the cathode side receiving the stream of exhaust gas 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.

[0093] The combustion system of any preceding clause, wherein the carbon capture system comprises an adsorbent bed.

[0094] The combustion system of any preceding clause, further comprising an air inlet line fluidly coupled to the atmosphere and to the carbon capture system.

[0095] The combustion system of any preceding clause, 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 exhaust gases.

[0096] 10. The combustion system of any preceding clause, wherein the fuel cell is a molten carbonate fuel cell (MCFC).

[0097] 10. The combustion system of any preceding clause, further comprising a cathode recirculation line extending from the cathode outlet line to the cathode inlet line.

[0098] 10. The combustion system of any preceding clause, further comprising an exhaust line fluidly extending between the carbon capture system and the exhaust stack.

[0099] The combustion system of any preceding clause, wherein the anode side receives a flow of fuel and / or steam via an anode inlet line.

[0100] 10. The combustion system of any preceding clause, further comprising an anode outlet line fluidly coupled to a separation system for removing water and liquid carbon dioxide from the anode output product.

[0101] The combustion system of any preceding clause, wherein about 85% to about 100% of pollutants from the exhaust gas exiting the topping cycle are collectively captured by the fuel cell and carbon capture system.

[0102] 1. A combustion system comprising: a gas turbine including a compressor section, a combustion section, and a turbine section, the turbine section producing an 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.

[0103] The combustion system of any preceding clause, wherein the carbon capture system comprises an adsorbent bed.

[0104] The combustion system of any preceding clause, further comprising an air inlet line fluidly coupled to the atmosphere and to the carbon capture system.

[0105] 10. The combustion system of any preceding clause, wherein the fuel cell is a molten carbonate fuel cell (MCFC).

[0106] 10. The combustion system of any preceding clause, further comprising a cathode recirculation line extending from the cathode outlet line to the cathode inlet line.

[0107] 10. The combustion system of any preceding clause, further comprising an exhaust line fluidly extending between the carbon capture system and the exhaust stack.

[0108] The combustion system of any preceding clause, wherein the anode side receives a flow of fuel and / or steam via an anode inlet line.

[0109] 10. The combustion system of any preceding clause, further comprising an anode outlet line fluidly coupled to a separation system for removing water and liquid carbon dioxide from the anode output product.

[0110] The combustion system of any preceding clause, wherein about 85% to about 100% of pollutants from the exhaust gas exiting the topping cycle are collectively captured by the fuel cell and carbon capture system. [Explanation of symbols]

[0111] 10. Gas turbine 14 First Load 15 Combustor fuel supply source 16 Turbine Section 18 Combustor or Combustion Section 20 Compressor Section 21 Shaft 22 Steam Turbine System 23 Shaft 24 Second Load 26 Low-pressure (LP) steam turbine 28 Intermediate Pressure (IP) Steam Turbine 30 High Pressure (HP) Steam Turbine 32 Heat Recovery Steam Generator (HRSG) 34 Exhaust gas 100 Combustion or Combined Cycle Systems 102 Topping Cycle 104 Bottoming Cycle 105 exhaust stack 106 Fuel Cell 108 Carbon Capture System 110 exhaust stack 112 Anode side 114 Electrolytes 116 Cathode side 117 Exhaust gas outlet line 118 Cathode inlet line 120 fuel cell power output 121 Power Converter 122 Electrical Devices 124 Electric Bus 126 Anode inlet line 128 Anode Fuel Supply 130 Fuel preheater 132 Anode outlet line 134 Separation System 136 Heat exchanger 137 Water flush inlet line 138 Water Flash Separator 139 Compressor inlet line 140 Compressor 141 Chiller inlet line 142 Chiller 143 Connection Line 144 Liquid carbon dioxide separator 145 Anode recirculation line 146 Cathode outlet line 148 Steam Supply Line 150 Condenser 151 Condensate return line 152 Turbine outlet line 154 HRSG Exit Line 155 Direct Contact Cooler 156 Adsorption bed 157 Fan or blower 158 Carbon Dioxide-Rich Streams 160 Air Inlet Line 162 Pump 164 Valve 166 Exhaust line 168 Cathode recirculation line 170 Exhaust gas recirculation line 171 Ambient air 172 Valve 174 Exhaust Gas Cooler 180 Heat exchanger 184 Burner 186 Anode vapor supply source 188 Anode vapor supply line 200 ways

Claims

1. a topping cycle (102) for generating a flow of exhaust gas (34); a bottoming cycle (104); a heat recovery steam generator (HRSG) (32) that receives the exhaust gases (34) from the topping cycle (102), the HRSG (32) producing a stream of steam for use in the bottoming cycle (104); a fuel cell (106) including an anode side (112), a cathode side (116), and an electrolyte (114), the cathode side (116) receiving a flow of the exhaust gas (34) from the HRSG (32) via a cathode inlet line (118), the cathode side removing a first portion of pollutants from the exhaust gas (34); a carbon capture system (108) fluidly coupled to the cathode side (116) via a cathode outlet line (146), the carbon capture system (108) removing a second portion of pollutants from the exhaust gas (34); A combustion system (100) comprising:

2. The combustion system (100) of claim 1, wherein the carbon capture system (108) comprises an adsorption bed (156).

3. The combustion system (100) of claim 1, further comprising an air inlet line (160) fluidly coupled to the atmosphere and the carbon capture system (108).

4. 2. The combustion system of claim 1, 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 gases.

5. The combustion system (100) of any preceding claim, wherein the fuel cell (106) is a molten carbonate fuel cell (MCFC).

6. The combustion system (100) of claim 1, further comprising a cathode recirculation line (168) extending from the cathode exit line (146) to the cathode inlet line (118).

7. The combustion system (100) of any preceding claim, further comprising an exhaust line (166) fluidly extending between the carbon capture system (108) and an exhaust stack (110).

8. The combustion system (100) of any preceding claim, wherein the anode side (112) receives a flow of fuel and / or steam via an anode inlet line (126).

9. The combustion system (100) of claim 1, further comprising an anode outlet line (132) fluidly coupled to a separation system (134) for removing water and liquid carbon dioxide from the anode output product.

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

11. a gas turbine (10) including a compressor section (20), a combustion section (18), and a turbine section (16), the turbine section (16) producing exhaust gases (34); a fuel cell (106) including an anode side (112), a cathode side (116), and an electrolyte (114), the cathode side (116) receiving the exhaust gas (34) from the turbine section (16) via an exhaust gas outlet line (117), the cathode side (116) removing a first portion of pollutants from the exhaust gas (34); a carbon capture system (108) fluidly coupled to the fuel cell (106) for removing a second portion of pollutants from the exhaust gas (34); an exhaust gas recirculation line (170) extending from the exhaust gas outlet line (117) to the compressor section (20); A combustion system (100) comprising:

12. The combustion system (100) of claim 11, wherein the carbon capture system (108) comprises an adsorption bed (156).

13. The combustion system (100) of claim 11, further comprising an air inlet line (160) fluidly coupled to the atmosphere and the carbon capture system (108).

14. The combustion system (100) of claim 11, wherein the fuel cell (106) is a molten carbonate fuel cell (MCFC).

15. The combustion system (100) of claim 11, further comprising a cathode recirculation line (168) extending from the cathode exit line (146) to the cathode inlet line (118).

16. The combustion system (100) of claim 11, further comprising an exhaust line (166) fluidly extending between the carbon capture system (108) and an exhaust stack (110).

17. The combustion system (100) of claim 11, wherein the anode side (112) receives a flow of fuel and / or steam via an anode inlet line (126).

18. The combustion system (100) of claim 11, further comprising an anode outlet line (132) fluidly coupled to a separation system (134) for removing water and liquid carbon dioxide from the anode output product.

19. 12. The combustion system (100) of claim 11, wherein between about 85% and about 100% of the pollutants from the exhaust gas (34) exiting the topping cycle (102) are collectively captured by the fuel cell (106) and the carbon capture system (108).

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