KR20250137586A - Combustion system with fuel cell and carbon capture system - Google Patents

Abstract

A combustion system is provided. The combustion system includes a topping cycle and a bottoming cycle that generate a flow of exhaust gas. 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 a flow of exhaust gas from the HRSG through a cathode inlet line. The cathode side removes a first portion of pollutants from the exhaust gas. A carbon capture system is fluidly connected to the cathode side through a cathode outlet line. The carbon capture system removes a second portion of pollutants from the exhaust gas.

Description

Combustion system with fuel cell and carbon capture system

The present disclosure relates generally to a combustion system comprising a fuel cell and one or more additional carbon capture systems. In particular, the present disclosure relates to a combustion system comprising a fuel cell and a carbon capture system.

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 from the turbine, and at least one steam turbine in fluid communication with the HRSG. During operation, air enters the compressor through an inlet system and is progressively compressed as it is directed toward a compressor discharge or diffuser casing that at least partially surrounds the combustor(s) of the combustion section. At least a portion of the compressed air is mixed with fuel and burned within combustion chambers defined within the combustor(s) to produce high temperature and high pressure combustion gases.

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

Turbomachinery combustion systems typically burn hydrocarbon fuels, producing air pollutants such as nitrogen oxides (NOx), carbon monoxide (CO), and carbon dioxide ( _CO2 ). In an effort to reduce emissions, carbon capture systems are used to capture _CO2 and other pollutants before turbomachinery gases are exhausted into the atmosphere. However, known carbon capture systems are only partially effective and require significant amounts of energy.

Therefore, an improved combined cycle power plant with a carbon capture system that removes pollutants from emissions without requiring large amounts of electrical power will be in demand and will be recognized in this field.

Aspects and advantages of the combined cycle system and method according to the present disclosure are set forth in part in the following description, or may become apparent from this description, or may be learned by practice of the present technology.

According to one embodiment, a combustion system is provided. The combustion system includes a topping cycle and a bottoming cycle that generate a flow of exhaust gas. The combustion system further includes a fuel cell having an anode side, a cathode side, and an electrolyte. The cathode side receives a flow of exhaust gas from the topping cycle through 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 through a cathode outlet line. The HRSG generates a flow of steam for use in the bottoming cycle. A carbon capture system is fluidly connected to the HRSG through an HRSG outlet line. The carbon capture system removes a second portion of pollutants from the exhaust gas.

According to another embodiment, a method of removing pollutants from a combustion system is provided. The method comprises the step of operating a topping cycle of the combustion system, thereby generating a first power output and exhaust gas. The method may further comprise the step of passing 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 comprises the step of 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.

According to another embodiment, a combustion system is provided. The combustion system includes a topping cycle and a bottoming cycle that generate a flow of exhaust gas. 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 a flow of exhaust gas from the HRSG through a cathode inlet line. The cathode side removes a first portion of pollutants from the exhaust gas. A carbon capture system is fluidly connected to the cathode side through a cathode outlet line. The carbon capture system removes a second portion of pollutants from the exhaust gas.

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 exhaust gas from the turbine section through an exhaust gas outlet line. The cathode side removes a first portion of pollutants from the exhaust gas. A carbon capture system is fluidly connected 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.

These and other features, aspects, and advantages of the present combustion system and method will be 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 present technology and, together with the description, serve to explain the principles of the present technology.

A complete and enabling disclosure of the present combustion system and method, including the best mode of making and using the present combustion system and method, intended for those skilled in the art, is set forth in the specification, which reference is made to the accompanying drawings.
FIG. 1 is a schematic illustration of a combustion system according to an embodiment of the present disclosure.
FIG. 2 is a schematic illustration of a combustion system according to an embodiment of the present disclosure.
FIG. 3 is a flowchart of a method for removing pollutants from a combustion system according to an embodiment of the present disclosure.

Reference will now be made in detail to embodiments of the present combustion system and method, one or more of which are illustrated in the drawings. Each embodiment is provided by way of illustration and not limitation of the present technology. In fact, 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 may be combined with another embodiment to yield a still further embodiment. Accordingly, the present disclosure is intended to cover such modifications and variations as fall within the scope of the appended claims and their equivalents.

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

The detailed description uses numbers and letters to designate features within the drawings. The same or similar designations in the drawings and description are used to designate the same or similar parts 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 indicate the position or importance of individual components.

The term "fluid" may be a gas or a liquid. The term "fluid communication" means that a fluid can connect the designated areas.

As used herein, the terms "upstream" (or "forward") and "downstream" (or "backward") refer to the relative direction of fluid flow within a fluid path. For example, "upstream" refers to the direction in which fluid flows away from it, and "downstream" refers to the direction in which fluid flows toward it. However, the terms "upstream" and "downstream" as used herein may also refer to the flow of electricity. The term "radially" refers to a relative direction substantially perpendicular to the axial centerline of a particular component, the term "axially" refers to a relative direction substantially parallel and/or coaxially aligned with the axial centerline of a particular component, and the term "circumferentially" refers to a relative direction extending around the axial centerline of a particular component.

Approximation terms, such as "about," "approximately," "typically," and "substantially," are not limited to the exact values specified. In at least some instances, approximation expressions may correspond to the precision of the instrument that measures the value, or the precision of the method or machine that constructs or manufactures the component and/or system. For example, an approximation expression may mean within 1 percent, 2 percent, 4 percent, 5 percent, 10 percent, 15 percent, or 20 percent of an individual value, a range(s) of values, and/or an endpoint defining a range(s) of values. When used in the context of an angle or direction, such terms include within 10 degrees of the stated angle or direction. For example, "typically perpendicular" includes any direction, e.g., clockwise or counterclockwise, within 10 degrees of perpendicular.

The terms "coupled," "fixed," "attached," and the like, unless otherwise stated herein, refer to direct coupling, fixation, or attachment, as well as indirect coupling, fixation, or attachment via one or more intermediate components or features. As used herein, the terms "comprise," "comprising," "include," "comprising," "have," "having," or any other variation thereof, are intended to include a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of features is not necessarily limited to only those features but may include other features not expressly listed or inherent to such process, method, article, or apparatus. Furthermore, unless expressly stated to the contrary, "or" refers to an "inclusive or" and not an "exclusive or." For example, condition A or condition B is satisfied by either: A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or both A and B are true (or exist).

Throughout this specification and claims, range limits are combined and interchangeable, and such ranges are identified and include all subranges contained therein, unless context or language dictates otherwise. For example, all ranges disclosed herein are inclusive of endpoints, and the endpoints are independently combinable.

As used herein, the term "line" may refer to a fluid conveying conduit, such as a pipe, hose, tube, duct, or other fluid conveying conduit.

Referring to the drawings, FIGS. 1 and 2 illustrate schematic diagrams of one embodiment of a combustion system or combined cycle system (100) comprising a topping cycle (102) and a bottoming cycle (104), respectively. In the topping cycle (102), fuel is burned to generate electrical or mechanical power, resulting in the production of exhaust gas (34) containing carbon dioxide. Then, in the bottoming cycle (104), the exhaust gas (34) from the topping cycle (102) can be used to generate additional electrical and mechanical power. In various embodiments, the topping cycle (102) may be an internal combustion engine, such as in an industrial process where fuel is burned. In some embodiments, the bottoming cycle (104) may be a heat exchanger, a boiler, a supercritical CO ₂ cycle, a superheater, an evaporator, a pump, or the like. In an exemplary embodiment, as shown, the topping cycle (102) may be a gas turbine (10) and the bottoming cycle (104) may be a steam turbine system (22).

A combined cycle system (100) may include a gas turbine (10) driving a first load (14). The first load (14) may be, for example, an electric generator that generates 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 of the combustion section (18). The combustor fuel supply (15) may supply natural gas, for example, a hydrocarbon fuel, to the combustion section (18), which may include methane, propane, or the like. In an exemplary embodiment, the combustor fuel supply (15) may supply methane (CH ₄ ) to the combustion section (18). Additionally or alternatively, the combustor fuel supply unit (15) may supply liquid fuel, such as diesel, crude oil, synthesis gas, etc., to the combustor.

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

The heated exhaust gas (34) exiting the turbine section (16) may then be discharged from the gas turbine (10) and may first be sent through a heat recovery steam generator (HRSG) (32) or a fuel cell (106), where a first portion of the pollutants (e.g., CO ₂ ) are removed from the exhaust gas (34). For example, in some embodiments, as illustrated in FIG. 2 , the exhaust gas (34) may first be sent through the HRSG (32) before being introduced into the fuel cell (106). In such embodiments where the exhaust gas (34) is first sent through the HRSG (32) before being introduced into the fuel cell (106), the exhaust gas will be cooled to between about 60° C. and about 150° C. as it exits 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 disposed on the cathode inlet line (118) to preheat the exhaust gas (34) prior to introduction into 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 provided to the carbon capture system (108). The cathode output product may transfer heat to the exhaust gas within the cathode inlet line (118). Additionally or alternatively, a burner (184) may be included on the cathode inlet line (118) to increase the temperature of the exhaust gas before it is introduced into the cathode side (116). The burner (184) may combust a fuel, which may be natural gas (e.g., from the fuel supply (15)) or an anode output product.

In another embodiment, as illustrated in FIG. 1, the exhaust gas (34) may first be routed through a fuel cell (106) before being introduced into the HRSG (32). In the HRSG (32), heat transfer occurs between the exhaust gas (34) and various components of the HRSG (32) to produce steam, which is provided to the steam turbine system (22). Next, the exhaust gas (34) may be routed to a carbon capture system (108), such as an absorption bed, where a second portion (e.g., the remainder) of the pollutants (e.g., CO ₂ ) are removed from the exhaust gas. Finally, the exhaust gas (34) may exit the carbon capture system (108) and be exhausted to the atmosphere through an exhaust stack (110).

The exhaust gas (34) may primarily comprise nitrogen (N ₂ ), carbon dioxide (CO ₂ ), oxygen (O ₂ ), and water (H ₂ O) as it exits the turbine section (16). Additionally, the exhaust gas (34) may comprise 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 (CO ₂ ) may be removed from the exhaust gas (34) in a fuel cell (106), and a second portion of the carbon dioxide (CO ₂ ) may be removed from the exhaust gas (34) in an additional carbon capture system (108) (e.g., an adsorption bed). In some embodiments, the second portion of the CO ₂ removed from the carbon capture system (108) may be the remainder of the CO ₂ in the exhaust gas (34), such that all of the CO ₂ (e.g., 100%) may be removed from the exhaust gas (34) before it is exhausted through the exhaust stack (110).

The combined cycle system (100) may also include a steam turbine system (22) that drives a second load (24). The second load (24) may also be an electric generator that generates electrical power. However, the first and second loads (14, 24) may be other types of loads that can be driven by the gas turbine (10) and the steam turbine system (22). Furthermore, 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.

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

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 electrically charged ions. The fuel cell (106) may directly convert chemical energy stored in a hydrocarbon fuel into electrical energy by 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 embodiments, the electrolyte (114) may be a molten carbonate mixture suspended within a porous, chemically inert ceramic matrix of a beta-alumina solid electrolyte (BASE). An MCFC can be operated by passing a reactant fuel gas (e.g., natural gas) across the anode side (112) while an oxidizing gas (e.g., exhaust gas containing carbon dioxide along with oxygen) passes across the cathode side (116), which causes an electrochemical reaction across the electrolyte (114) that consumes (or chemically converts) carbon dioxide and generates electricity. In particular, at the cathode side (116), the oxygen and carbon dioxide produce carbonate ions (CO ₃ ^2- ).

As briefly mentioned above, the fuel cell (106) converts the anode fuel stream and 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 sent to a power converter (121) to change the DC current into AC current that can be effectively utilized by one or more subsystems. In particular, in the illustrated embodiment, the power output (120) may be provided from the power converter to one or more electrical devices (122) via an electric bus (124). The electric bus (124) may be a dedicated electric bus, such as an electric bus for the combined cycle system (100), the gas turbine (10), the steam turbine system (22), the fuel cell (106), or the carbon capture system (108). The electric bus (124) is electrically connected to one or more additional electrical devices (122), which may be a power source, a power sink, or both. For example, the additional electrical devices (122) may be power storage devices (e.g., one or more batteries), electric machines (e.g., an electric generator, an electric motor, or both). Alternatively or additionally, the power output (120) may assist in driving the first load (14) and/or the second load (24). The combined cycle system (100) may produce a total power output (e.g., the sum of the first load (14), the second load (24), and the power output (120) of the fuel cell (106). In various embodiments, the power output (120) of the fuel cell (106) may be about 10% to about 30% of the total power output of the combined cycle system (100). In another embodiment, the power output (120) of the fuel cell (106) may be about 15% to about 25% of the total power output of the combined cycle system (100).

In various embodiments, the cathode side (116) may be fluidly coupled (e.g., directly coupled) to the gas turbine (10) via a cathode inlet line (118). The cathode inlet line (118) may be identical to an exhaust outlet line (117) extending from an outlet of the turbine section (16), or the cathode inlet line (118) may extend from the exhaust outlet line (117). In particular, the cathode side (116) may be fluidly coupled with an 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, a cathode inlet line (118) can extend (e.g., directly) between the outlet of the turbine section (16) and the inlet of the cathode side (116) of the fuel cell (106) to convey 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) can be directed through the cathode side (116) of the fuel cell (106) to remove a first portion of the contaminants (e.g., CO ₂ ) from the exhaust gas (34) (i.e., a branch line cannot extend from the cathode inlet line (118). In an alternative embodiment, a fan or blower (157) can be included in the cathode inlet line (118), as illustrated in FIG. 1 . The fan (157) can advantageously overcome the flow resistance in the cathode side (116), HRSG (32), direct contact cooler (155), and carbon capture system (108). That is, the fan (157) can promote the flow of exhaust gas passing through the cathode side (116), HRSG (32), direct contact cooler (155), and carbon capture system (108).

In various embodiments, the anode side (112) can receive fuel and/or vapor through an anode inlet line (126). Fuel and vapor can be delivered 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 identical to the combustor fuel supply (15) such that the same fuel is supplied to 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 various embodiments, the anode fuel supply (128) can supply natural gas (e.g., a hydrocarbon fuel) to the anode side (112) through the anode inlet line (126). The natural gas can include methane, propane, etc. In an exemplary embodiment, the anode fuel supply (128) can supply methane (CH ₄ ) to the anode side (112). A fuel preheater (130), such as a heat exchanger, can be positioned in thermal communication with the anode inlet line (126). The fuel preheater (130) can heat the fuel before it enters the anode side (112) of the fuel cell (106), which advantageously increases the efficiency of the fuel cell (106).

In an exemplary embodiment, the combined cycle system (100) may include an anode vapor supply line (188). The anode vapor supply line (188) may extend between a heat exchanger (136) and an anode inlet line (126). Steam may be generated by heat from the anode output product within the heat exchanger (136) and provided to the anode inlet line (126). The anode vapor supply line (188) may provide a flow of steam 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 vapor supply line (126) may be fluidly coupled to the HRSC (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).

In various embodiments, the combined cycle system (100) can include an anode outlet line (132) that is fluidly connected to an outlet of the anode side (112) such that the anode outlet line receives output products from the anode side (112) after the electrochemical reaction within the fuel cell (106). In certain embodiments, the anode output products can include CO ₂ , CO, H ₂ , water, and unutilized CH ₄ (e.g., methane that was not utilized during the electrochemical reaction within the fuel cell (106). The anode output products can be supplied to a separation system (134), which can remove water and liquefied CO ₂ from the anode output products.

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 fluidically 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). A heat exchanger (136) can remove heat from the anode output product before it enters the water flash separator (138), which generates steam in the steam inlet line (188) for use at the inlet on the anode side to maintain a desired steam to carbon molecular ratio (which may be from about 1.5 to about 5, or specifically from about 2 to about 3). A water flash inlet line (137) extends between and fluidly connects the heat exchanger (136) and the water flash separator (138). The water flash separator (138) can remove water from the anode output product. For example, water in the anode output product can be cooled to a liquefaction temperature by the heat exchanger (136) and subsequently removed by the water flash separator (138). In some embodiments, the anode output product can be passed through a water gas shift reactor to convert carbon monoxide to hydrogen. In such an embodiment, the water gas shift reactor may be placed between the heat exchanger (136) and the water flash separator (138).

In many embodiments, a compressor inlet line (139) may extend between and be connected in fluid communication with a water flash separator (138) and a compressor (140). The compressor (140) may pressurize the anode output product and provide the pressurized anode output product to a chiller (142) via a chiller inlet line (141). The chiller (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 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 connected in fluid communication with the liquid carbon dioxide separator (144) via a connection line (143).

An 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 (water and liquid carbon dioxide removed) into the anode side (112). For example, the anode recycle line (145) may advantageously reintroduce any unutilized methane and excess hydrogen back into the anode side (112) for electrochemical conversion.

In some embodiments, as illustrated in FIG. 1, the HRSG (32) may be positioned downstream of the cathode side (116). In such embodiments, the HRSG (32) may be fluidly coupled (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 and be fluidly coupled between the outlet of the cathode side (116) and the HRSG (32). The HRSG (32) may generate steam from heat from exhaust gases exiting the cathode side (116), which may be supplied to the steam turbine system (22).

In another embodiment, as illustrated in FIG. 2, the HRSG (32) may be positioned upstream of the cathode side (116). In such an embodiment, the HRSG (32) may be fluidly coupled (e.g., directly fluidly coupled in some embodiments) to the 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 use heat from exhaust gases exiting the turbine section (16) to generate steam, which may be supplied to the steam turbine system (22).

A steam supply line (148) may extend from the HSRG (32) to the steam turbine system (22). In particular, the steam supply line (148) may extend from the HSRG (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 another embodiment (not shown), the outlet steam of the HP steam turbine (30) may re-enter the reheater of the HRSG and, after being superheated, may be 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 can convert steam from the outlet of the LP steam turbine (26) into water, which can be supplied back to the HRSG (32) via a condensate return line (151).

In certain embodiments, the combined cycle system (100) may further include a cathode recycle line (168) extending from the cathode outlet line (146) to the cathode inlet line (118) and coupled in fluid communication therewith. For example, the cathode recycle line (168) may extend in fluid communication between an inlet disposed 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 disposed on the cathode inlet line (118). The cathode recycle line may reintroduce any unreacted CO ₂ to the cathode side (116) for further reaction/removal from the exhaust gas.

In various embodiments, as illustrated in FIG. 1, a carbon capture system (108), e.g., an adsorbent-based carbon capture system, may be fluidly coupled to the fuel cell (106) such that the carbon capture system (108) receives cathode output products from the cathode side (116) of the fuel cell (106). 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 an exemplary embodiment, the carbon capture system (108) may be an adsorbent bed (156) that removes a second portion of the pollutants (e.g., CO ₂ ) from the exhaust gas. In particular, the adsorption layer (156) can remove the remainder of the CO ₂ from the exhaust gas such that all of the CO ₂ is removed from the exhaust gas before it exits the exhaust stack (110). Additionally, in some embodiments, as illustrated in FIG. 1, a direct contact cooler (155) can be included in the HRSG outlet line (154) to further cool the exhaust gas exiting the HRSG (32) before it enters the carbon capture system (108). For example, the direct contact cooler (155) can be positioned in the HRSG outlet line (154) upstream of the carbon capture system (108). The direct contact cooler (155) can spray water (or other suitable coolant) into the exhaust gas, thereby cooling the temperature of the exhaust gas before it enters the carbon capture system (108).

In another embodiment, as illustrated in FIG. 2, the carbon capture system (108) may be fluidly coupled (e.g., directly coupled) to the outlet of the cathode side (116) via a cathode outlet line (146). In such an embodiment, the cathode outlet line (146) may extend between and be fluidly coupled with 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 (146) to the carbon capture system (108).

Although the exemplary embodiment of the carbon capture system (108) includes an adsorbent layer (156), the carbon capture system (108) may utilize 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.

In various embodiments, the carbon capture system (108) may employ pressure swing adsorption (PSA). PSA may be used to separate carbon dioxide from a gas mixture. In PSA technology, at high partial pressures, a solid molecular sieve may adsorb carbon dioxide. Consequently, at elevated pressures, carbon dioxide is removed from the gas mixture as it passes through the adsorption bed. Regeneration of the bed is achieved by depressurization and purging. Typically, for essential operations, multiple adsorption vessels are used for continuous separation of carbon dioxide, where one adsorption bed is in use while another adsorption bed is being regenerated.

In an exemplary embodiment, the carbon capture system (108) may employ temperature swing adsorption (TSA). In TSA, the adsorbent adsorbs _CO2 from the cathode output product at low temperatures (preferably between cryogenic temperatures and up to 60°C). Subsequently, the saturated adsorbent bed is desorbed by increasing the temperature (typically above 100°C). Desorption may occur in the presence of a sweep gas that lowers the partial pressure of the _CO2 or under vacuum. The heat required for desorption may be supplied by steam from a low-pressure steam turbine. Finally, the adsorbent bed will be cooled back to its initial temperature to prepare the bed for the next adsorption cycle.

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 elevated pressure and temperature, CO ₂ is absorbed by the CaO to form calcium carbonate (CaCO ₃ ), thereby removing CO ₂ from the gas mixture. The adsorbent CaO is regenerated by calcination of the CaCO ₃ , which can reform the CaCO ₃ back into CaO.

In some embodiments, membrane separation technology may also be used for the separation of carbon dioxide from the exhaust gas by the carbon capture system (108). Membranes used for high temperature carbon dioxide separation include zeolite membranes and ceramic membranes, which are selective for _CO2 . Membrane separators operate more efficiently at higher pressures, and the use of membrane separators to separate carbon dioxide from the exhaust gas may be accomplished by additional compression (e.g., by one or more compressors upstream of the carbon capture system (108)).

In another embodiment, other technologies that may be used for the separation of _CO2 from the exhaust gas by the carbon capture system (108) may include, but are not limited to, chemical absorption of _CO2 using amines. The exhaust gas may be cooled to a temperature suitable for chemical absorption of carbon dioxide using amines. This technology is based on an alkanol amine solvent, which has the ability to absorb carbon dioxide at relatively low temperatures and is 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 technology may include pure triethanolamine, monoethanolamine, diethanolamine, diisopropanolamine, diglycolamine, and piperazine, or mixtures thereof.

In some embodiments, the carbon capture system may include at least one absorption vessel, wherein chemical absorption technology is used. In another embodiment, the carbon dioxide separator includes at least one membrane separator.

In an exemplary embodiment, the carbon capture system may include at least one adsorbent bed (156), wherein TSA technology may be used to separate carbon dioxide from the exhaust stream exhaust gas. In particular, in an exemplary embodiment, the carbon capture system (108) may include a plurality of adsorbent beds (156) (e.g., from about 10 to about 500 adsorbent beds, or from about 10 to about 400 adsorbent beds, or from about 30 to about 250 adsorbent beds, or from about 10 to about 100 adsorbent beds). During operation, some adsorbent beds (156) may undergo adsorption, some adsorbent beds (156) may undergo desorption, while the remaining adsorbent beds are cooled for the temperature swing adsorption process. Under partial load, only some of the adsorbent beds need to be operated due to the reduced _CO2 flow rate in the exhaust gas (cathode output product), allowing the other adsorbent beds (156) to stand by. Ambient air may be supplied to these atmospheric adsorption layers (156) to adsorb additional _CO2 from the atmosphere, thereby achieving negative system emissions. Alternatively, or additionally, several additional adsorption layers may be added, which may operate as a direct air capture system that receives steam from a steam turbine for desorption. In this manner, negative carbon emissions may be achieved during normal full load conditions.

In another embodiment, the adsorption layer (156) may be a direct contact adsorption layer. The direct contact adsorption layer comprises a single large rotating bed, which includes many segments in which different processes occur. In such an embodiment, the carbon capture system (108) may comprise from about 1 to about 100 direct contact adsorption layers.

For example, the combined cycle system (100) may further include an air inlet line (160) fluidly coupled to the atmosphere (or surrounding environment) and to the carbon capture system (108). In particular, the air inlet line (160) may be in fluid communication with each of the adsorbent beds (156) such that additional air may be supplied to the standby adsorbent beds (156) for additional carbon capture. In various embodiments, a pump (162) (e.g., 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 otherwise preventing the passage of air). The valve (164) may be downstream of the pump (162). The pump (162) may create a differential pressure that draws air from the atmosphere when the pump is operated. Air from the atmosphere can be passed through a carbon capture system (108) (e.g., an adsorption layer (156)) to remove any contaminants (e.g., CO ₂ ) present in the air. This advantageously allows the combined cycle system (100) to have negative carbon dioxide emissions, since all (e.g., 100%) of the carbon dioxide in the exhaust gas from the turbine section (16) can be captured by the fuel cell (106) and the carbon capture system (108), and additional atmospheric air can be introduced to the carbon capture system (108) via the air inlet line (160) for additional carbon dioxide removal from the atmospheric air.

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

In various 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 layer (156) and the exhaust stack (110). The exhaust stack (110) may exhaust the exhaust gas (from which pollutants have been removed) to the atmosphere.

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 the exhaust gas is exhausted into 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) are collectively captured by the fuel cell (106) and the carbon capture system (108) (e.g., the adsorption layer (156)). The fuel cell (106) can remove a majority of the carbon dioxide from the exhaust gas, and the carbon capture system (108) can remove the remainder of the carbon dioxide from the exhaust gas. In particular, about 50% to about 90% of the carbon dioxide from the exhaust gas can be removed by the fuel cell (106) when exhaust gas recirculation is implemented, or, for example, about 75% to about 85% without exhaust gas recirculation. While more carbon dioxide can be removed from the fuel cell (106), this is not possible without undue stress on the fuel cell (106), reducing the life of the fuel cell (106), and reducing the electrical efficiency (i.e., the ratio between electricity produced by the fuel cell and fuel energy supplied at the anode) of the fuel cell (106). 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 preserves the life of the fuel cell (106) and allows it to operate efficiently. 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, e.g., 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 adsorbent layer (156) in the exemplary embodiment).

As previously discussed, in some embodiments, as illustrated 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 provide the exhaust gas (or cathode output product) to the HRSG (32), and the HRSG outlet line (154) may provide the exhaust gas to the carbon capture system (108). Alternatively, as illustrated 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 provided to the cathode side (116) via the cathode inlet line (118). Additionally, as illustrated in FIG. 2, when the HRSG (32) is positioned upstream of the fuel cell (106), the cathode output product can be provided directly to the carbon capture system (108) (e.g., via the cathode outlet line (146)).

In various embodiments, as illustrated in FIGS. 1 and 2, the combined cycle system (100) may include an exhaust gas recirculation line (170) that fluidly couples the turbine section (16) to the compressor section (20) such that exhaust gas from the outlet of the turbine section (16) is provided to the inlet of the compressor section (20). The exhaust gas recirculation line (170) may extend from the exhaust gas outlet line (117) to the compressor section (20). In such embodiments, the compressor (20) may receive ambient air (171) as well as the recycled exhaust gas. When exhaust gas recirculation is introduced, this increases the CO ₂ mol% in the gas turbine exhaust gas from about 4.3% to up to about 8%, which allows the fuel cell (106) to operate at a higher efficiency. For example, with exhaust gas recirculation, the fuel cell (106) may remove up to 90% of the CO ₂ from the exhaust gas. An exhaust gas recirculation line (170) selectively diverts a portion of the exhaust gas from the exhaust gas outlet line (117) back to the inlet of the compressor section (20). For example, a valve (172) may be disposed in the exhaust gas recirculation line (170). The valve (172) may be selectively operable between an open position (allowing exhaust gas recirculation) and a closed position (restricting or preventing exhaust gas recirculation). Additionally, in an exemplary embodiment, an exhaust gas cooler (174) may be disposed in the exhaust gas recirculation line (170). The exhaust gas cooler (174) may be a heat exchanger that cools the exhaust gas within the exhaust gas recirculation line (170) to meet the inlet temperature requirements for the gas turbine (10).

Referring to FIG. 3, a flow diagram of one embodiment of a method (200) for removing contaminants from a combined cycle system is illustrated in accordance with aspects of the present subject matter. Generally, the method (200) will be described herein with reference to the combined cycle system (100) described above with reference to FIGS. 1 and 2 . However, it will be appreciated by those skilled in the art that the disclosed method (200) can generally be utilized with any suitable combined cycle system and/or in connection with a system having any other suitable system configuration. Furthermore, while FIG. 3 depicts steps performed in a particular order for purposes of illustration and discussion, the methods discussed herein are not limited to any particular order or arrangement unless otherwise specified in the claims. Those skilled in the art will appreciate, using the teachings provided herein, that the various steps of the methods disclosed herein can be omitted, rearranged, combined, and/or adjusted in various ways without departing from the scope of the present disclosure.

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

In an exemplary embodiment, as illustrated, the method (200) may further include the step of passing the exhaust gas through the cathode side (116) of the fuel cell (106) at block 204, whereby a first portion of the pollutants are removed 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 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. An MCFC can be operated by passing a reactant fuel gas (e.g., natural gas mixed with steam) across the anode side (112) while an oxidizing gas (e.g., exhaust gas containing carbon dioxide and oxygen) passes across the cathode side (116), which causes an electrochemical reaction across the electrolyte (114) to remove (or chemically convert) carbon dioxide and produce electricity and hydrogen.

In various implementations, as illustrated, the method (200) may further include the step of providing exhaust gas (i.e., cathode output product) from the outlet of the cathode side at block 206 to a carbon capture system (108). A second portion of the contaminant (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 layer (156) that removes the remainder of the carbon dioxide from the exhaust gas downstream of the fuel cell (106).

For example, the pollutant may be carbon dioxide, and a first portion of the pollutant removed from the exhaust gas by the cathode side may be a majority (e.g., greater than 50%) of the carbon dioxide in the exhaust gas as it exits the gas turbine (10). Accordingly, a second portion of the pollutant removed from the exhaust gas by the carbon capture system (108) may be the remainder of the carbon dioxide in the exhaust gas. In particular, up to about 85% of the carbon dioxide in the exhaust gas from the turbine section (16) may be removed (i.e., electrochemically converted) at the cathode side (116) of the fuel cell (106), and the remainder of the carbon dioxide (e.g., about 15%) may be removed by the carbon capture system (108) prior to exhaust from the exhaust stack (110). For example, about 85% to about 100% of the pollutants from the exhaust gas exiting the topping cycle (102) are collectively captured by the fuel cell (106) and the carbon capture system (108) (e.g., the adsorption layer (156)). The fuel cell (106) can remove a majority of the carbon dioxide from the exhaust gas, and the carbon capture system (108) can remove the remainder of the carbon dioxide from the exhaust gas. In particular, about 70% to about 90%, or, for example, about 75% to about 85%, of the carbon dioxide from the exhaust gas can be removed by the fuel cell (106). While more carbon dioxide can be removed by the fuel cell (106), this is not possible without undue stress on the fuel cell (106), reducing the life of the fuel cell (106), and reducing the efficiency of the fuel cell (106). Accordingly, operating the fuel cell (106) in a manner that removes from about 50% to about 85% (or, for example, from about 50% to about 90% when exhaust gas recirculation is implemented) of the carbon dioxide from the exhaust gas advantageously preserves the life of the fuel cell (106) and allows for efficient operation. The remainder of the carbon dioxide in the exhaust gas exiting the turbine section (16), for example, from about 15% to about 50% (or, for example, from about 15% to about 25%) of the exhaust gas, can be removed by the carbon capture system (108) (e.g., the adsorbent layer (156) in the exemplary embodiment).

In various implementations, operating the combined cycle system (100) may produce a total power output (e.g., the sum of the power produced by the first load (14), the power produced by the second load (24), and the power output (120) of the fuel cell (106). In exemplary implementations, operating the fuel cell (106) and the carbon capture system (108) may require a power supply of about 0.5% to about 5% (or, for example, about 3% to about 5%) of the total power output. As discussed above, the fuel cell (106) may be capable of more aggressive operation, where greater than 85-90% of the carbon dioxide is captured in the fuel cell (106), but this significantly increases the impact of loss mechanisms, such as cathode polarization (dominant resistance due to low concentrations of carbon dioxide), ohmic resistance, anode polarization, and activation losses. This reduces the overall plant efficiency, or electrical efficiency, of the fuel cell (106). Operating the fuel cell (106) to consume up to about 85% of the carbon dioxide 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 a power supply of about 3% to about 5% of the total power output of the combined cycle system (100), which is lower than other designs that achieve a 100% carbon capture rate because the specific energy required to capture _CO2 (MJ/kg of _CO2 captured) increases monotonically as the carbon capture rate increases. Additionally, integrating a fuel cell (106) (e.g., MCFC) generates about 20-25% additional power, thus increasing the net power output of the plant, whereas all other carbon capture technologies consume energy, thereby lowering the net power output from the plant. A fuel cell (106) (e.g., MCFC) can generate about 20% to 25% surplus power (assuming a carbon capture ratio of about 85%; if the carbon capture ratio is reduced to about 50%, the lower bound for surplus power may be about 10%); however, it also consumes fuel to do so. Increasing the _CO2 capture ratio from the fuel cell (106) increases losses within the fuel cell (106), thus decreasing the fuel-to-electricity efficiency of the fuel cell (106), 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 a parasitic load, which contributes to a decrease in overall plant efficiency of greater than about 2% (which may increase as the carbon capture ratio in the fuel cell (106) increases). In an embodiment where the carbon capture ratio in the fuel cell (106) is reduced to about 50%, the decrease in overall plant efficiency may be about 1%.

The maximum _CO2 capture limit of a fuel cell (106) (e.g., MCFC) will vary as a function of the _CO2 concentration in the exhaust gas. Gas turbine (10) exhaust gas (34) typically contains about 5% molar _CO2 . When exhaust gas recirculation is implemented, the % molar increases to about 8% molar _CO2 , which in turn increases the maximum _CO2 capture by the fuel cell (106) from about 85% to about 90%. Other processes, such as industrial processes, may have high _CO2 concentration exhaust gases (e.g., cement plant exhaust will have about 30% molar _CO2 ). In such embodiments, when the fuel cell is fed exhaust gas from an industrial process having a high % molar _CO2 (e.g., a cement plant or a coal plant), the fuel cell can achieve higher capture rates (e.g., greater than 90%).

In an alternative embodiment, as indicated by the dashed box, the method (200) may include passing the exhaust gas from the outlet of the cathode side (116) through a heat recovery steam generator (HRSG) (32) prior to providing the exhaust gas to the carbon capture system (108) at block 208. In such an embodiment, the method may include generating steam with the HRSG (32) at block 210 and providing the steam to a bottoming cycle (104) at block 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 electrical power. The second load (24) may also be an electric generator that generates electrical power.

In some embodiments, the method (200) may include providing air from the atmosphere to the exhaust gas to the carbon capture system (108) at block 214 (e.g., when the topping cycle (102) is operated at partial load for a normal-sized adsorbent bed, or when the topping cycle (102) is operated at full load for an oversized adsorbent bed). For example, the air from the atmosphere may be introduced to the carbon capture system (108) through the air inlet line (160) when the gas turbine (10) is operated at partial 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 can be introduced into the carbon capture system (108) via the air inlet line (160) when the gas turbine (10) is operated at full load for a system having an oversized carbon capture system (108) (e.g., sized larger than the gas turbine carbon dioxide output requirement). As a result of providing air in addition to the exhaust gas from the gas turbine, carbon dioxide is removed from the air and exhaust gas, causing the combustion system to produce a negative carbon capture emission. The gas turbine (10) can be operated at full load (e.g., full capacity or 100%) and part load (e.g., less than full capacity or less than 100%). At full load, the gas turbine (10) can produce a large amount of exhaust gas, which can utilize the full carbon dioxide capture capacity of the fuel cell (106) and carbon capture system (108). However, at partial load, the gas turbine (10) may produce less exhaust gas, which may provide additional capacity for capturing carbon dioxide to the carbon capture system (108). This additional capacity may be utilized to capture carbon dioxide from the atmosphere, advantageously allowing 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 collectively captured by the fuel cell (106) and carbon capture system (108), and additional carbon dioxide may be captured from the atmosphere by introducing air from the atmosphere to the carbon capture system (108) in addition to the exhaust gas.

This written description discloses the invention, including the best mode, and also uses examples to enable any person skilled in the art to practice the invention, including making and using any device or system and performing any integrated 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. These other embodiments are intended to be within the scope of the claims if they include structural elements that do not differ from the literal expression of the claims, or if they include equivalent structural elements with minor differences from the literal expression of the claims.

Additional aspects of the present invention are provided by the following subject matter:

A combustion system comprising: a topping cycle generating a flow of exhaust gas; a bottoming cycle; a fuel cell comprising an anode side, a cathode side, and an electrolyte, the cathode side receiving a flow of exhaust gas from the topping cycle through 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 through a cathode outlet line, the HRSG generating a flow of steam for use in the bottoming cycle; and a carbon capture system fluidly connected to the HRSG through an HRSG outlet line, the carbon capture system removing a second portion of pollutants from the exhaust gas.

A combustion system, wherein in any one of the preceding items, the carbon capture system comprises an adsorbent layer.

A combustion system, further comprising an air inlet line fluidly connected to said atmosphere and said carbon capture system, in any one of the preceding items.

A combustion system in any one of the preceding items, 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.

A combustion system according to any one of the preceding claims, further comprising an exhaust gas recirculation line fluidly connecting the turbine section to the compressor section.

A combustion system, wherein in any one of the preceding items, the fuel cell is a molten carbonate fuel cell (MCFC).

A combustion system further comprising a cathode recirculation line extending from the cathode outlet line to the cathode inlet line in any one of the preceding items.

A carbon capture system, further comprising an exhaust line extending in fluid communication between the carbon capture system and the exhaust stack, in any one of the preceding items.

A combustion system in any of the preceding items, wherein the anode side receives a flow of fuel and/or steam through an anode inlet line.

A combustion system further comprising an anode outlet line fluidly connected to a separation system for removing water and liquid carbon dioxide from the anode output product, in any one of the preceding items.

A combustion system, wherein in any one of the preceding items, about 85% to about 100% of the pollutants from the exhaust gas exiting the topping cycle are collectively captured by the fuel cell and the carbon capture system.

A method of removing a pollutant from a combustion system, the method comprising: operating a topping cycle of the combustion system, whereby a first power output and exhaust gas are generated; passing the exhaust gas through a cathode side of a fuel cell, whereby a first portion of the pollutant is removed from the exhaust gas; and providing the exhaust gas from an outlet of the cathode side to a carbon capture system, whereby a second portion of the pollutant is removed from the exhaust gas by the carbon capture system.

A method according to any one of the preceding claims, wherein the pollutant comprises carbon dioxide, wherein the first portion of the pollutant removed from the exhaust gas by the cathode side comprises a majority of the carbon dioxide in the exhaust gas, and wherein the second portion of the pollutant removed from the exhaust gas by the carbon capture system is the remainder of the carbon dioxide in the exhaust gas.

A method according to any one of the preceding claims, wherein the pollutant comprises 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 the carbon capture system.

A method according to any preceding claim, wherein the combustion system generates a total power output, and the step of operating the fuel cell and the carbon capture system requires a power supply of about 0.5% to about 5% of the total power output.

A method according to any preceding item, further comprising the step of delivering the exhaust gas from the outlet of the cathode side through a heat recovery steam generator (HRSG) prior to providing the exhaust gas to the carbon capture system.

A method further comprising the steps of: generating steam with the HRSG; and providing the steam to a bottoming cycle of the combustion system, the bottoming cycle generating a second power output.

A method according to any preceding claim, further comprising the step of providing 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.

A method according to any preceding item, further comprising the step of delivering fuel and/or vapor through the anode side of the fuel cell.

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

A combustion system, wherein in any one of the preceding items, the carbon capture system comprises an adsorbent layer.

A combustion system, further comprising an air inlet line fluidly connected to said atmosphere and said carbon capture system, in any one of the preceding items.

A combustion system in any one of the preceding items, 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.

A combustion system, wherein in any one of the preceding items, the fuel cell is a molten carbonate fuel cell (MCFC).

A combustion system further comprising a cathode recirculation line extending from the cathode outlet line to the cathode inlet line in any one of the preceding items.

A carbon capture system, further comprising an exhaust line extending in fluid communication between the carbon capture system and the exhaust stack, in any one of the preceding items.

A combustion system in any of the preceding items, wherein the anode side receives a flow of fuel and/or steam through an anode inlet line.

A combustion system further comprising an anode outlet line fluidly connected to a separation system for removing water and liquid carbon dioxide from the anode output product, in any one of the preceding items.

A combustion system, wherein in any one of the preceding items, about 85% to about 100% of the pollutants from the exhaust gas exiting the topping cycle are collectively captured by the fuel cell and the carbon capture system.

A combustion system comprising: a gas turbine comprising a compressor section, a combustion section, and a turbine section, the turbine section generating exhaust gas; a fuel cell comprising an anode side, a cathode side, and an electrolyte, the cathode side receiving the exhaust gas from the turbine section through 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 the pollutants from the exhaust gas; and an exhaust gas recirculation line extending from the exhaust gas outlet line to the compressor section.

A combustion system, wherein in any one of the preceding items, the carbon capture system comprises an adsorbent layer.

A combustion system, further comprising an air inlet line fluidly connected to said atmosphere and said carbon capture system, in any one of the preceding items.

A combustion system, wherein in any one of the preceding items, the fuel cell is a molten carbonate fuel cell (MCFC).

A combustion system further comprising a cathode recirculation line extending from the cathode outlet line to the cathode inlet line in any one of the preceding items.

A carbon capture system, further comprising an exhaust line extending in fluid communication between the carbon capture system and the exhaust stack, in any one of the preceding items.

A combustion system in any of the preceding items, wherein the anode side receives a flow of fuel and/or steam through an anode inlet line.

A combustion system further comprising an anode outlet line fluidly connected to a separation system for removing water and liquid carbon dioxide from the anode output product, in any one of the preceding items.

A combustion system, wherein in any one of the preceding items, about 85% to about 100% of the pollutants from the exhaust gas exiting the topping cycle are collectively captured by the fuel cell and the carbon capture system.

Claims (19)

As a combustion system,
Topping cycle which creates a flow of exhaust gases;
Botting cycle;
a heat recovery steam generator (HRSG) receiving the exhaust gas from the topping cycle (the HRSG generating a flow of steam for use in the bottoming cycle); and
A fuel cell comprising an anode side, a cathode side and an electrolyte, said cathode side receiving a flow of said exhaust gas from a HRSG through a cathode inlet line, said cathode side removing a first portion of contaminants from said exhaust gas;
A combustion system comprising a carbon capture system fluidly connected to the cathode side via a cathode outlet line, said carbon capture system removing a second portion of pollutants from said exhaust gas. A combustion system in accordance with claim 1, wherein the carbon capture system comprises an adsorbent layer. A combustion system, further comprising an air inlet line fluidly connected to the atmosphere and the carbon capture system in accordance with the first aspect of the invention. A combustion system in accordance with claim 1, wherein the topping cycle is a gas turbine coupled to a first load, the gas turbine comprising a compressor section, a combustion section and a turbine section, the turbine section generating the exhaust gas. A combustion system in claim 1, wherein the fuel cell is a molten carbonate fuel cell (MCFC). A combustion system, further comprising a cathode recirculation line extending from the cathode outlet line to the cathode inlet line in the first aspect. A carbon capture system, further comprising an exhaust line extending in fluid communication between the carbon capture system and the exhaust stack in accordance with the first aspect. A combustion system in accordance with claim 1, wherein the anode side receives a flow of fuel and/or steam through an anode inlet line. A combustion system, further comprising an anode outlet line fluidly connected to a separation system for removing water and liquid carbon dioxide from the anode output product. A combustion system in accordance with claim 1, wherein about 85% to about 100% of the pollutants from the exhaust gas exiting the topping cycle are collectively captured by the fuel cell and the carbon capture system. As a combustion system,
A gas turbine comprising a compressor section, a combustion section, and a turbine section, the turbine section generating exhaust gas;
A fuel cell comprising an anode side, a cathode side and an electrolyte, said cathode side receiving said exhaust gas from said turbine section through an exhaust gas outlet line, said cathode side removing a first portion of pollutants from said exhaust gas;
a carbon capture system fluidly coupled to the fuel cell for removing a second portion of pollutants from the exhaust gas; and
A combustion system comprising an exhaust gas recirculation line extending from the exhaust gas outlet line to the compressor section. A combustion system in claim 11, wherein the carbon capture system includes an absorbent layer. A combustion system, in accordance with claim 11, further comprising an air inlet line fluidly connected to the atmosphere and the carbon capture system. A combustion system in claim 11, wherein the fuel cell is a molten carbonate fuel cell (MCFC). A combustion system in accordance with claim 11, further comprising a cathode recirculation line extending from the cathode outlet line to the cathode inlet line. A carbon capture system, further comprising an exhaust line extending in fluid communication between the carbon capture system and the exhaust stack, in accordance with claim 11. A combustion system in accordance with claim 11, wherein the anode side receives a flow of fuel and/or steam through an anode inlet line. A combustion system, further comprising an anode outlet line fluidly connected to a separation system for removing water and liquid carbon dioxide from the anode output product in accordance with claim 11. A combustion system in accordance with claim 11, wherein about 85% to about 100% of the pollutants from the exhaust gas exiting the topping cycle are collectively captured by the fuel cell and the carbon capture system.