System and method for cooling exhaust gas in transition duct

Abstract

A system includes a heat recovery steam generator (HRSG) configured to generate steam using heat from an exhaust gas, an exhaust stack disposed downstream of the HRSG, and a cooling transition duct disposed downstream of the exhaust stack. The cooling transition duct includes a converging duct that decreases in a cross-sectional area in a flow direction from an inlet to an outlet of the converging duct. The cooling transition duct also includes one or more coolers disposed in the converging duct. The one or more coolers are configured to cool the exhaust gas within the converging duct between the inlet and the outlet. The cooling transition duct is configured to direct cooled exhaust gas to a gas capture system, an exhaust gas recirculation (EGR) system, or both.

Description

SYSTEM AND METHOD FOR COOLING EXHAUST GAS IN TRANSITION DUCTBACKGROUND

[0001] The present application relates generally to a system and method for cooling an exhaust gas in a transition duct adapted to an exhaust stack downstream of a heat recovery steam generator.

[0002] An industrial plant, such as a combustion-driven power plant, may produce a variety of gases, such as an exhaust gas of a combustion system. The combustion system may include a gas turbine engine, a reciprocating piston-cylinder engine, a furnace, a boiler, or other industrial equipment. These exhaust gases may include one or more undesirable gases, such as acid gases and / or greenhouse gases. For example, the undesirable gases may include carbon oxides (COx) such as carbon dioxide (CO2) and carbon monoxide (CO), nitrogen oxides (NOx) such as nitrogen dioxide (NO2), and / or sulfur oxides (SOx) such as sulfur dioxide (SO2). CO2 is both an acid gas and a greenhouse gas. Unfortunately, the atmospheric content of CO2 has generally increased over thousands of years, and currently exceeds about 420 parts per million by volume (ppmv) or 643 parts per million by weight (ppmw) in the atmosphere. With various regulations and environmental concerns regarding global warming, it would be desirable to reduce the output of undesirable gases (e.g., CO2) into the atmosphere, particularly for hydrocarbon fuel consuming equipment such as combustion systems.BRIEF DESCRIPTION

[0003] Certain embodiments commensurate in scope with the originally claimed subject matter are summarized below. These embodiments are not intended to limit the scope of the claimed embodiments, but rather these embodiments are intended only to provide a brief summary of possible forms of the subject matter. Indeed, the presently- claimed embodiments may encompass a variety of forms that may be similar to or different from the embodiments set forth below.

[0004] In certain embodiments, a system includes a heat recovery steam generator (HRSG) configured to generate steam using heat from an exhaust gas. an exhaust stack disposed downstream of the HRSG, and a cooling transition duct disposed downstream of the exhaust stack. The cooling transition duct includes a converging duct that decreases in a cross-sectional area in a flow direction from an inlet to an outlet of the converging duct. The cooling transition duct also includes one or more coolers disposed in the converging duct. The one or more coolers are configured to cool the exhaust gas within the converging duct between the inlet and the outlet. The cooling transition duct is configured to direct cooled exhaust gas to a gas capture system, an exhaust gas recirculation (EGR) system, or both.

[0005] In certain embodiments, a system includes a controller configured to control a gas capture system of a gas treatment system to capture an undesirable gas from a gas. The controller is further configured to monitor one or more sensors coupled to a cooling transition duct, wherein the cooling transition duct is located downstream of an exhaust stack located downstream of a heat recovery steam generator (HRSG), wherein the HRSG is configured to generate steam using heat from an exhaust gas. The cooling transition duct includes one or more coolers in a converging duct that decreases in a cross-sectional area in a flow direction from an inlet to an outlet of the converging duct, wherein the one or more coolers are configured to cool the exhaust gas within the converging duct between the inlet and the outlet. The cooling transition duct is configured to direct cooled exhaust gas to the gas capture system, an exhaust gas recirculation system, or both.

[0006] In certain embodiments, a method is provided for retrofitting a combined cycle power plant with a gas capture system of a gas treatment system and / or an exhaust gas recirculation (EGR) system. The method includes forming an opening in a side wall of an exhaust stack downstream of a heat recovery steam generator (HRSG). The method further includes adding a cooling transition duct to the opening in the side wall of the exhaust stack, wherein the cooling transition duct includes one or more coolers coupled to a converging duct that decreases in a cross-sectional area in a flow direction from an inlet to an outlet of the converging duct, wherein the one or more coolers are configured to cool an exhaust gas within the converging duct upstream from the gascapture system of the gas treatment system and / or the EGR system. The method further includes coupling a coolant supply system to the one or more coolers of the cooling transition duct.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] These and other features, aspects, and advantages of the presently disclosed techniques will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

[0008] FIG. 1 is a block diagram of an embodiment of a combined cycle system having a gas turbine system, a steam turbine system, a heat recovery’ steam generator (HRSG), a gas treatment system having one or more gas capture systems, a w aste heat recovery system, and a cooling transition duct configured to cool exhaust gas from the heat recovery7steam generator.

[0009] FIG. 2 is a schematic of an embodiment of the cooling transition duct, illustrating the flow path of the exhaust gas from the exhaust stack to the cooling transition duct where the gas is cooled and then sent to the gas treatment system and the exhaust gas recirculation system.

[0010] FIG. 3 is a schematic of an embodiment of a horizontal spray cooler with a vertical manifold for housing in the cooling transition duct.

[0011] FIG. 4 is a schematic of an embodiment of a vertical media cooler with a packing or porous material for housing in the cooling transition duct.

[0012] FIG. 5 is a schematic of an embodiment of a vertical spray' cooler for housing in the cooling transition duct.

[0013] FIG. 6 is a schematic of an embodiment of the cooling transition duct, illustrating the various coolers of FIGS. 3-5 housed w ithin the cooling transition duct.DETAILED DESCRIPTION

[0014] One or more specific embodiments of the presently disclosed systems and methods are described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementationspecific decisions must be made to achieve the developers’ specific goals, such as compliance with system-related and business-related constraints, which may vary' from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

[0015] When introducing elements of various embodiments of the presently disclosed embodiments, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0016] The disclosed embodiments include systems and methods to reduce the carbon footprint of combustion systems, such as combustion-driven power plants and / or combined cycle power plants, using a gas treatment system having one or more gas capture systems and an exhaust gas recirculation (EGR) system. In particular, the disclosed embodiments provide a cooling transition duct configured to cool and transition an exhaust gas upstream of the gas treatment system and the EGR system, such as directly downstream from an exhaust stack and a heat recovery' steam generator (HRSG). Thus, the cooling transition duct serves multiple purposes (e.g., temperature control, pressure control, and flow control) within the footprint of the cooling transition duct, rather than cooling the exhaust gas separate from the transition duct. In certain embodiments, the cooling transition duct may eliminate the need for a separate cooling system for cooling the exhaust gas upstream of the gas treatment system and the EGR system. The cooling transition duct may include a plurality' of cooling systems arrangedin series and / or in parallel within the cooling transition duct. The plurality of cooling systems may be configured to cool the exhaust gas to a temperature suitable for the gas treatment system and / or the EGR system. V arious aspects of the cooling transition duct are discussed in detail below.

[0017] The gas treatment system includes one or more gas capture systems configured to remove undesirable gases (e.g., CCh) from the intake air and / or the exhaust gas of the combustion systems. The gas capture systems may include sorbentbased gas capture systems, solvent-based gas capture systems, cry ogenic gas capture systems, or a combination thereof. As discussed below, the plurality of cooling systems of the cooling transition duct is configured to adjust (e.g., reduce) the temperature of the exhaust gas (or other gas) prior to entry in the gas capture systems, thereby helping to improve the efficiency of adsorption of absorption of the undesirable gases (e.g., CO2).

[0018] As discussed below, the cooling transition duct may include the plurality of cooling systems in a variety7of configurations configured to cool the exhaust gas (or other gas) to a temperature suitable for the gas treatment system and the EGR system. Although specific examples are provided below, the cooling systems in the cooling transition duct may be used in any suitable manner to support various gas capture systems, including but not limited to, sorbent-based gas capture systems, solvent-based gas capture systems, and cry ogenic gas capture systems.

[0019] FIG. 1 is a block diagram of an embodiment of a combined cycle system 10 having a gas turbine system 12, a steam turbine system 14, a heat recovery steam generator (HRSG) 16, a gas treatment system 18 having one or more gas capture systems 20, a controller 22 coupled to each of the systems 12, 14, 16, and 18, and a cooling transition duct 24 (CTD). As illustrated, the HRSG 16 outputs an exhaust gas 62 to an exhaust stack 28 coupled to the CTD 24, wherein the exhaust gas 62 may be controlled to flow through an outlet 29 of the exhaust stack 62 and / or through an inlet 23 of the CTD 24. The CTD 24 includes a plurality' of cooling systems 30 (e.g., coolers and / or scrubbers) configured to cool and scrub the exhaust gas 62 while transitioning the exhaust gas 62 (e.g.. converging duct) between the inlet 23 and an outlet 25 of theCTD 24. The CTD 24 discharges the exhaust gas 62 through the outlet 25 and directs the exhaust gas 62 to either an exhaust gas recirculation (EGR) system 60 and / or the gas treatment system 18 as discussed in further detail below. The EGR system 60 is configured to recirculate the exhaust gas 62 through the gas turbine system 12. The one or more gas capture systems 20 of the gas treatment system 18 are configured to capture an undesirable gas (e.g., CO2) from the exhaust gas 62 downstream from the CTD 24.

[0020] Before discussing details of the gas treatment system 18, various aspects of the combined cycle system 10 are discussed in further detail. For purposes of orientation in the drawings, reference may be made to an axial direction or axis 40, a radial direction or axis 42 extending radially away from the axial direction or axis 40, and a circumferential direction or axis 44 extending circumferentially around the axial direction or axis 40. The directions or axes 40, 42, and 44 may be in reference to a rotational axis 36 of the gas turbine system 12, for example.

[0021] The gas turbine system 12 includes an air intake 50, a compressor 52 having one or more compressor stages, one or more combustors 54, a turbine 56 having one or more turbine stages, and a load 58 (e.g., electrical generator) driven by the turbine 56. In certain embodiments, the gas turbine system 12 further includes the EGR system 60 configured to recirculate the exhaust gas 62 into the air intake 50. The recirculated exhaust gas 62 helps to reduce the temperature and formation of certain emissions (e g., nitrogen oxides (NOx)) associated with combustion in the combustors 54. In operation, the compressor 52 receives air (and also exhaust gas 62 if the EGR system 60 is active) from the air intake 50. and compresses the air and / or exhaust gas 62 in one or more compressor stages (e.g., stages of rotating compressor blades). The combustors 54 then combust fuel from a fuel supply system with the compressed air and / or exhaust gas, and generate hot combustion gases. The hot combustion gases expand and drive one or more turbine stages (e.g., stages of rotating turbine blades) in the turbine 56, thereby driving rotation of the compressor 52 and the load 58 via shafts. The turbine 56 then outputs the hot combustion gases as the exhaust gas 62.

[0022] The HRSG 16 recovers waste heat from the exhaust gas 62 to generate steam for driving the steam turbine system 14. The HRSG 16 includes a high-pressure (HP)steam section 70, an intermediate-steam (IP) section 72, and a low-pressure (LP) steam section 74 configured to generate HP steam 76, IP steam 78, and LP steam 80. The steam turbine system 14 may include an HP steam turbine 82 driven by the HP steam 76, an IP steam turbine 84 driven by the IP steam 78, and a LP steam turbine 86 driven by the LP steam 80. In addition to the steam provided by the HRSG 16, the HP steam turbine 82 provides IP steam to the IP steam turbine 84, and the IP steam turbine 84 provides LP steam to the LP steam turbine 86. The LP steam turbine 86 then outputs any remaining steam / water to a condensate line 88 coupled to the LP steam section 74 of the HRSG 16. The condensate line 88 may include a condenser 90 configured to condense any remaining steam to form a condensate, and a pump 92 configured to pump the condensate back to the LP steam section 74. In operation, the steam turbine system 14 drives a load 94 (e.g., electrical generator) via a shaft. In certain embodiments, the steam turbine system 14 and / or the HRSG 16 may provide heated water and / or steam (e.g., HP steam 76, IP steam 78, and / or LP steam 80) to the gas treatment system 18 to support a desorption mode of the one or more gas capture systems 20. For example, the gas capture systems 20 may receive heated water and / or steam in a temperature range of 100 to 150 degrees Celsius, 110 to 150 degrees Celsius, 120 to 150 degrees Celsius, or 130 to 150 degrees Celsius.

[0023] After the HRSG 16, the exhaust gas 62 may flow through the exhaust stack 28 and / or the CTD 24. In certain embodiments, the exhaust stack 28 and / or the CTD 24 may include one or more flow control valves (e.g., dampers or valves) configured to open and close a first flow through the exhaust stack 28 and / or a second flow through the CTD 24. For example, the flow control valves may be configured to selectively move between positions to (1) completely open the first flow through the CTD 24 and completely close the second flow through the exhaust stack 28, (2) completely close the first flow through the CTD 24 and completely open the second flow through the exhaust stack 28. or (3) partially open the first flow through the CTD 24 and partially open the second flow through the exhaust stack 28. The CTD 24 includes the plurality of cooling systems 30 configured to cool the exhaust gas 62 for subsequent treatment in the gas treatment system 18 and / or recirculation into the gas turbine system 12 via the EGR system 60.

[0024] The CTD 24 includes the plurality of cooling systems 30, such as one or more indirect coolers (e.g., heat exchangers), one or more direct contact coolers (DCC), or a combination thereof. The cooling systems 30 may be arranged in series and / or in parallel relative to a flow direction of the exhaust gas 62 through the CTD 24. The CTD 24 is configured to cool the exhaust gas 62 via indirect heat exchange or direct contact cooling (e.g., direct gas-to-liquid contact) between the exhaust gas 62 and a cooling fluid (e.g.. cooling water). The direct contact cooler is configured to directly cool the exhaust gas 62 via direct injection of a cooling fluid (e.g., cooling water) into the exhaust gas 62, contact of the exhaust gas 62 with porous packing material, or a combination thereof. The heat exchanger may include a fin and tube heat exchanger, a plate and shell heat exchanger, a shell and tube heat exchanger, or any heat exchanger configuration with one or more cooling fluid passages isolated from the exhaust gas 62, such that indirect heat exchanger occurs between the cooling fluid (e.g., cooling water) and the exhaust gas 62. Thus, the plurality of cooling systems 30 is configured to cool the exhaust gas 62 to provide a cooled exhaust gas 62 prior to treatment in the gas treatment system 18 and / or prior to recirculation to the gas turbine system 12 via the EGR system 60.

[0025] In the illustrated embodiment, the exhaust gas 62 flows through one or more gas capture systems 20 configured to capture undesirable gases. The undesirable gases may include carbon oxides (COx) (e.g., carbon dioxide (CO2) and carbon monoxide (CO)), nitrogen oxides (NOx) (e.g., nitrogen dioxide (NO2)), sulfur oxides (SOx) (e.g., sulfur dioxide (SO2)), or any combination thereof. In the following discussion, CO2 may be used as an example of the undesirable gases; however, the gas capture systems 20 may be designed to capture any of the foregoing undesirable gases. For example, the gas capture systems 20 include one or more carbon capture systems 100 (e.g., CO2 capture systems). The gas capture systems 20 (e.g., carbon capture systems 100) may include sorbent-based gas capture systems, solvent-based gas capture systems, cryogenic gas capture systems, or any combination thereof, configured to remove and capture undesirable gases. The carbon capture system 100 may include components 102, 104, 106, and 108 configured to enable gas capture of undesirable gases (e.g., CO2) from the exhaust gas 62. thereby outputting a treated gas 110 and a captured gas 112(e.g., CO2). The treated gas 110 may be substantially free of the undesirable gases (e.g., CO2) and may be discharged through an exhaust stack (e.g., the exhaust stack 28 or a separate exhaust stack). The captured gas 112 (e.g.. CO2) may be compressed by a compression system 1 14 and stored and / or transported by a storage and / or pipeline system 116.

[0026] In certain embodiments, the carbon capture system 100 is a sorbent-based carbon capture system, and the components 102, 104, 106, and / or 108 include multiple sorbent-based carbon capture units (e.g., adsorbers). For example, the sorbent-based carbon capture units may include temperature swing adsorption (TSA) units or adsorbers, wherein a temperature swing or change is used to sequentially operate in an adsorption mode, a desorption mode, and a cooling mode at different temperatures. In the adsorption mode, the adsorber is configured to adsorb undesirable gases (e.g., CO2) into sorbent material at a first temperature. In the desorption mode, the adsorber is configured to desorb the undesirable gases (e.g., CO2) from the sorbent material, for example, by heating the sorbent material from the first temperature to a higher second temperature using a heat source. The heat source may include a heated fluid, such as a heated gas and / or liquid (e.g., steam). In the cooling mode, the adsorber is cooled in preparation for the next adsorption mode.

[0027] In certain embodiments, the carbon capture system 100 is a solvent-based carbon capture system, and the components 102, 104, 106, and / or 108 include one or more absorbers, strippers, and associated equipment. For example, the absorber is configured to absorb undesirable gases (e.g.. CO2) into a solvent, thereby outputting the treated gas 1 10 through an exhaust stack and a CCh-rich solvent to the stripper. The stripper is configured to apply heat to the CCh-rich solvent, thereby stripping the undesirable gases (e.g., CO2) from the solvent to produce the captured gas 112 and a CCh-lean solvent. The stripper may receive heat via a heat source, such as a heated gas and / or liquid (e.g., steam). The stripper returns the CCh-lean solvent to the absorber to repeat the cycle.

[0028] In the illustrated embodiment, the controller 22 is configured to control all aspects of the combined cycle system 10. The controller 22 includes one or moreprocessors 120, memory 122, instructions 124 stored on the memory 122 and executable by the processor 120, and communication circuitry 126 configured to communicate with sensors and various equipment of the combined cycle system 1 . For example, the controller 22 is configured to receive sensor feedback from sensors coupled to the gas turbine system 12, the steam turbine system 14, the HRSG 16, the gas treatment system 18 (e.g., gas capture systems 20), the CTD 24 (including cooling systems 30), and the EGR system 60, and control the same equipment based on the sensor feedback, operating modes, user input, computer models, or any combination thereof. The sensors may include temperature sensors, pressure sensors, flow rate sensors, gas composition sensors, or any combination thereof. In certain embodiments, the controller 22 is configured to control the cooling systems 30 of the CTD 24 to control the temperature of the exhaust gas 62 upstream of the gas treatment system 18 and the EGR system 60, control the amount of exhaust gas 62 through the EGR system 60, and control the amount of exhaust gas 62 through the gas treatment system 18. Additionally, the controller 22 is configured to control operation of the gas capture systems 20 (e.g.. carbon capture systems 100), such by controlling modes of operation (e.g., adsorption mode, desorption mode, and cooling mode), controlling heat sources for supplying heated fluid (e.g., steam) to the gas capture systems 20, controlling cooling sources for supply cooled fluids to the gas capture systems 20, or any combination thereof.

[0029] In certain embodiments, sensors may monitor the temperature, pressure, flow rate, gas composition, moisture content, or any combination thereof, of the exhaust gas 62 flowing through the CTD 24 at a plurality of positions disposed at, upstream from, and / or downstream from each cooling system (e.g., cooler) of the plurality of cooling systems 30 in the CTD 24. By further example, the sensors may monitor the temperature, pressure, flow rate, or any combination thereof, of the cooling fluid (e.g., water) flowing through each of the plurality of cooling systems 30 of the CTD 24. In response to the feedback from the sensors, the controller 22 may adjust the temperature, pressure, flow rate, or any combination thereof, of the cooling fluid (e g., water) flowing through each of the plurality of cooling systems 30 of the CTD 24.

[0030] FIG. 2 is a schematic of an embodiment of the CTD 24 located dow nstream of the exhaust stack 28. The CTD 24 features exhaust gas conditioning that may be adapted to any size plant, as described in more detail below. As discussed below, the CTD 24 includes a cooling system 231 having one or more scrubbers and / or coolers 232 within a converging duct 234, wherein the converging duct 234 converges the exhaust gas 62 in a flow direction from an inlet 23 to an outlet 25 of the converging duct 234 of the CTD 24. and the one or more coolers 232 cool and scrub the exhaust gas 62 within the converging duct 234. The converging duct 234 decreases in a cross- sectional area (e.g., continuously and / or stepwise) in the flow direction from the inlet 23 to the outlet 25 of the converging duct 234. For example, the converging duct 234 may decrease in the cross-sectional area in the flow direction over at least 50, 60, 70, 80, 90, 95, or 100 percent of a total length of the converging duct 234 from the inlet 23 to the outlet 25. In certain embodiments, one or more coolers 232 also may be disposed in a duct betw een the HRSG 16 and the exhaust stack 28, in the exhaust stack 28, in the HRSG 16 adjacent the exhaust stack 28, or any combination thereof. Additional details of the coolers 232 are discussed below.

[0031] Within the converging duct 234, the one or more coolers 232 cool the exhaust gas 62 to reduce the flow7velocity and scrub the exhaust gas 62 to remove particulate. Absent the cooling, the decreasing cross-sectional area in the converging duct 234 causes an increase in the flow- velocity of the exhaust gas 62. Accordingly, by cooling the exhaust gas 62 while decreasing the cross-sectional area in the converging duct 234. the one or more coolers 232 help to counteract (e.g., reduce or eliminate) increases in the flow velocity of the exhaust gas 62 caused by the decreasing cross- sectional area. Thus, the CTD 24 simultaneously cools, scrubs, converges, and controls the flow velocity of the exhaust gas 62 within the volume of the converging duct 234, rather than performing cooling and / or scrubbing downstream from the converging duct 234. The cooling within the converging duct 234 of the CTD 24 helps to reduce pressure losses and / or reduce subsequent duct sizing (e.g., ductwork downstream from the outlet 25 of the converging duct 234).

[0032] The cooling system 231 also includes a coolant supply system 236 coupled to the one or more coolers 232. In the illustrated embodiment, the coolant supplysystem 236 includes a valve 246 and a coolant source 248 coupled to each of the one or more coolers 232. The coolant sources 248 may include one or more tanks, conduits, pumps, compressors, cooling systems (e.g., heat exchangers and fans), filters (e.g.. particulate filters, chemical filters, etc.), or any combination thereof. The coolant sources 248 may store one or more cooling fluids or coolants, such as water. The cooling systems, if included, may be configured to cool the coolant the same or different for each of the coolers 232. The valves 246 are configured to control a flow of the coolant from each coolant source 248 to each respective cooler 232. In some embodiments, the coolers 232 may include direct contact coolers (DCCs), indirect coolers (e.g., heat exchangers), or a combination thereof. The illustrated coolers 232 are arranged in series between the inlet 23 and the outlet 25 of the converging duct 234 of the CTD 24. However, the coolers 232 may be arranged in series, in parallel, at a top portion of the converging duct 234, at a bottom portion of the converging duct 234, at an intermediate portion of the converging duct 234, or any combination thereof. Additionally, the coolers 232 may be the same or different from one another, e.g., same or different cooler types (e.g.. direct or indirect coolers), spray orientations, sizes, or any combination thereof.

[0033] As illustrated in FIG. 2, the flow path of the exhaust gas 62 moves from the HRSG 16, into and through the exhaust stack 28, and into and through the CTD 24 for cooling by the coolers 232 within the CTD 24. The cooled exhaust gas 62, 218 is then routed through an outlet of the CTD 24 towards the gas treatment system 18 and / or the EGR system 60. The exhaust stack 28 may include a flow control valve 38 (e.g., damper, hinged bypass door, or flapper valve) that, when opened, allows the exhaust gas 62 to exit the exhaust stack 28 through an exhaust outlet 29 and at least partially bypass the CTD 24. Alternatively, if the flow control valve 38 is closed, the exhaust gas 62 may flow entirely into an inlet 23 of the CTD 24, through the CTD 24, and out through an outlet 25 of the CTD 24. In certain embodiments, the flow control valve 38 is a three-way flow control valve configured move between a first position that blocks flow through the outlet 29 of the exhaust stack 28 and opens flow through the inlet 23 of the CTD 24, a second position that opens flow through the outlet 29 of the exhaust stack 28 and blocks flow through the inlet 23 of the CTD 24. and a third position thatpartially blocks and partially opens flow through both the outlet 29 and the inlet 23. In some embodiments, a flow control valve 39 may be disposed adjacent the inlet 23 of the CTD 24, wherein the controller 22 is configured to open or close the flow control valve 39 to adjust the flow of exhaust gas 62 through the CTD 24, and the controller 22 is configured to open or close the flow control valve 38 to adjust the flow of exhaust gas 62 through the outlet 29 of the exhaust stack 28. The exhaust gas 62 may be free to enter the CTD 24 naturally (i.e. without blowers or fans), or it may be directed to flow into the CTD 24 via one or more blowers or fans coupled to the controller 22.

[0034] In the illustrated embodiment, the controller 22 may be coupled to various components of the CTD 24, including the valves 246 and the coolant sources 248 of the coolant supply system 236, and the one or more coolers 232. The controller 22 may be configured to receive feedback from various sensors 222 coupled to and distributed throughout the CTD 24. The sensors 222 (designated with an “S’") are configured to monitor various operational parameters of the CTD 24. In certain embodiments, the sensors 222 may include temperature sensors, pressure sensors, flow rate sensors, fluid composition sensors (e.g., gas composition sensors), humidity7and / or moisture sensors, or any combination thereof. The sensors 222 may monitor the parameters (e.g., temperature, pressure, flow rate, and fluid composition) at one or more locations of the converging duct 234 of the CTD 24, such as the exhaust gas 62 at the inlet 23, the outlet 25, and various intermediate positions between the inlet 23 and the outlet 25. The sensors 222 also may monitor the parameters (e.g., temperature, pressure, flow rate, and fluid composition) in the coolant supply system 236, such as the coolant stored in the coolant sources 248. The controller 22 also may receive feedback from the gas treatment system 18, the EGR system 60, the HRSG 16, and the gas turbine system 12 to help adjust the cooling system 231 to provide a suitable amount of cooling for the exhaust gas 62, such as by controlling the temperature of the exhaust gas 62 to be within a suitable temperature range for the gas treatment system 18 and the EGR system 60.

[0035] The controller 22 may be configured to control the valves 246 and the coolant sources 248 to regulate the cooling by the coolers 232. In certain embodiments, the coolers 232 include direct contact coolers configured to inject (e.g., spray, mist, rain, etc.) the coolant (e.g., water) directly into the exhaust gas 62, such that directcontact cooling occurs between the coolant and the exhaust gas 62 flowing through the CTD 24. That is, as the coolant is released from the one or more coolers 232, the coolant may cool the exhaust gas 62 via direct contact to lower the temperature and remove particulates, such that the exhaust gas 62 is suitable for downstream processes. As the sensors 222, the valves 246, and the coolant sources 248 are controlled and monitored by the controller 22, the valves 246 and the coolant sources 248 may be controlled to provide more or less coolant based on the sensor feedback. For example, in response to temperature sensors indicating that the exhaust gas 62 in the CTD 24 is higher than an upper temperature threshold or lower than a lower temperature threshold, the controller 22 may signal the valves 246 and the coolant sources 248 to inject more or less coolant through the coolers 232 onto the exhaust gas 62 to respectively decrease or increase the temperature of the exhaust gas 62. In this way, the CTD 24 may cool the exhaust gas 62 to a suitable temperature range via the coolers 232 based on sensor feedback. In certain embodiments, the suitable temperature range may include upper and lower temperature thresholds, such as from 220 degrees Fahrenheit to 70 degrees Fahrenheit. The CTD 24 may cool and scrub exhaust gas 62 downstream of the HRSG 16 and then direct the cooled, scrubbed exhaust gas 62, 218 to the gas treatment system 18 and EGR system 60. Excess coolant that may fall to the bottom of the CTD 24 may be disposed via a drain system 240. Alternatively, excess coolant may be collected via the drain system 240 and recycled or recirculated for continued use by the coolant supply system 236.

[0036] In certain embodiments, the one or more coolers 232 may include indirect coolers, such as a heat exchanger, condenser, or other indirect cooling system, such that there is no contact between the gas and the coolant. The coolant supply system 236 (e.g., valves 246 and coolant sources 248) supplies the coolant (e.g., water) for circulation through the coolers 232 (e.g., indirect coolers or heat exchangers), which indirectly transfer heat from the exhaust gas 62 to the coolant. The coolant then returns to the coolant source 248 for additional cooling by cooling systems, such as air cooled heat exchangers or liquid cooled heat exchangers. In certain embodiments, the controller 22 is configured to control the coolant supply system 236 to control the temperature, pressure, and flow rate of the coolant circulating through the coolers 232(e.g., indirect coolers or heat exchangers) based on the sensor feedback from sensors 222, thereby controlling (e.g., increasing or decreasing) the temperature of the exhaust gas 62 based on the upper and lower temperature thresholds.

[0037] In accordance with the embodiment depicted in FIG. 2, the CTD 24 may also include a pre-cooling extension 484 (e.g.. extension duct) located upstream of the exhaust stack 28 and downstream of the HRSG 16 that houses at least one cooler 232 (e.g., direct and / or indirect cooler). In this way, the CTD 24 features a modular design that may be customizable and scalable to meet application needs. The CTD 24 may be installed as part of a new system or it may be installed as a retrofit to existing plant equipment with minimal modification. The modularity and customizability of the CTD 24 is described in more detail below with respect to FIGS. 3-6.

[0038] FIGS. 3-5 illustrate example embodiments of the one or more scrubbers and / or coolers 232 (e.g.. coolers 460, 466, and 472) for installation in the converging duct 234 of the CTD 24. For purposes of orientation in the drawings, reference may be made to a horizontal or axial direction 480, and a vertical direction or radial 482 extending away from the axial direction 480. The axial and radial directions 480 and 482 are generally crosswise (e.g., perpendicular) relative to one another. The axial and radial directions 480 and 482 are used to describe various orientations of the coolers 232 of the cooling system 231 .

[0039] FIG. 3 illustrates an embodiment of a cooler 232, 460 (e.g., horizontal spray cooler or direct contact cooler) having a plurality of sprayers 462 (e.g.. horizontal sprayers) coupled to a manifold 470 (e.g., vertical manifold) for installation in the CTD 24. The manifold 470 of the horizontal spray cooler 460 may be equipped with one or more sprayers 462 coupled to an upstream side 474 and a downstream side 476 of the manifold 470 relative to a flow of the exhaust gas 62 through the converging duct 234 of the CTD 24. The sprayers 462 may include micro sprayers, atomizers, nozzles, orifices, or any combination thereof. The sprayers 462 may be oriented at one or more angles relative to the upstream and downstream sides 474 and 476, wherein the angles may vary between 10 to 90 degrees. In some embodiments, each of the sprayers 462 may include a diverging nozzle 478 (e.g., conical section). In some embodiments, thesprayers 462 may be flush with or recessed into the upstream and downstream sides 474 and 476 of the manifold 470. The manifold 470 includes one or more internal flow paths or passages coupled to the coolant supply system 236. which controls the flow of coolant through the manifold 470 to each of the sprayers 462. In some embodiments, one or more first internal flow paths extend through the manifold 470 to the sprayers 462 on the upstream side 474, while one or more second internal flow paths extend through the manifold 470 to the sprayers 462 on the downstream side 476. Thus, the controller 22 may be configured to control the coolant flow from the coolant supply system 236 independently to the sprayers 462 on the upstream and downstream sides 474 and 476 via the first and second internal flow paths through the manifold 470. In certain embodiments, the cooler 232, 460 may be installed in a horizontal orientation, rather than a vertical orientation, in the converging duct 234 of the CTD 24, such that the sprayers 462 are vertical sprayers and the manifold 470 is a horizontal manifold. In this way, the sprayers 462 of the one or more coolers 232 may be flexibly operated to spray the coolant 464 (e.g.. water) throughout the CTD 24 with customized conditions.

[0040] FIG. 4 illustrates an embodiment of a cooler 232, 466 (e.g., vertical media cooler or direct contact media cooler) for installation in the CTD 42. The vertical media cooler 466 may include packing or porous material 468 disposed in a housing or cartridge 486 (e.g., porous cartridge). The packing material 468 may include any configuration of packing, support trays or screens, wire meshes, coolant distributors, or any combination thereof. For example, each packing may include a plurality of beads, balls, or mixture inducing structures, which are configured to facilitate mixing between the exhaust gas 62 and the flow of the coolant 464. Each support tray or screen may include a wire mesh, a plate having a plurality of openings, or another suitable structure that holds the packing in position, while permitting fluid flow of gas and coolant. Additionally, the vertical media cooler 466 may include manifolds 488 on opposite end portions of the cartridge 486 to facilitate the supply of coolant 464 (e.g., water) from the coolant supply system 236 into the packing material 468, and to facilitate the return of the coolant 464 from the vertical media cooler 466 back to the coolant supply system 236 and / or to the drain system 240. The vertical media cooler 466 is generally oriented crosswise (e.g., perpendicular or normal) to the flow direction of the exhaust gas 62through the converging duct 234 of the CTD 24. However, the vertical media cooler 466 may be oriented at an angle greater than 0 degrees and less than or equal to 90 degrees relative to the flow direction of the exhaust gas 62.

[0041] FIG. 5 illustrates an embodiment of a cooler 232, 472 (e.g., vertical spraycooler or direct contact cooler) for installation in the CTD 24. The vertical spray cooler 472 may include one or more manifolds 470 (e.g.. horizontal manifolds) equipped with one or more sprayers 462 (e g., vertical sprayers) fastened vertically to the manifolds 470. The one or more sprayers 462 may include micro sprayers, atomizers, nozzles, orifices, or any combination thereof. The sprayers 462 may be oriented at one or more angles relative to a vertically facing side 490 (e.g., top side and / or bottom side) of the manifolds 470, wherein the angles may vary between 10 to 90 degrees. In some embodiments, each of the sprayers 462 may include the diverging nozzle 478 (e.g., conical section). In some embodiments, the sprayers 462 may be flush with or recessed into the vertically facing side 490 of the manifold 470. The sprayers 462 may be configured to spray the liquid coolant 464 throughout the CTD 24.

[0042] In certain embodiments, the sprayers 462 may be configured to inject the coolant 464 downwardly from one or more vertical locations in the converging duct 234 as a sheet, a mist, a shower, or any combination thereof, of droplets of the coolant 464 (e.g., water). Additionally, in certain embodiments, the sprayers 462 may be configured to inject the coolant 464 upwardly from one or more vertical locations in the converging duct 234 as a sheet, a mist, a cloud, a jet, or any combination thereof, of droplets of the coolant 464 (e.g., water). As illustrated in FIG. 5, the vertical spray coolers 472 are arranged in four vertical locations along a common vertical plane, wherein each vertical location may include 1, 2, 3, 4, 5, or more vertical spray coolers 472. In certain embodiments, the vertical spray coolers 472 may be arranged in one or more 2-dimensional grids across the flow path of exhaust gas 62 in the converging duct 234 of the CTD 24. In certain embodiments, the vertical spray coolers 472 may be arranged in a 3-dimensional array across the flow path of exhaust gas 62 in the converging duct 234 of the CTD 24, wherein the 3-dimensional array has multiple vertical spray coolers 472 arranged to spray the coolant 464 (e.g., water) in the axial direction 480 (e.g., upstream and / or downstream horizontal direction) and the radialdirection 482 (e.g., vertically upward and / or downward direction). In further embodiments, the vertical spray coolers 472 may be arranged in a array across the flow path of exhaust gas 62 in the converging duct 234 of the CTD 24, wherein the 3- dimensional array has multiple vertical spray coolers 472 consisting of vertical pipes arranged in one plane and to spray the coolant 464 (e.g., water) substantially in a direction normal to the axial direction 480 and substantially normal to the extension of the pipes.

[0043] The one or more coolers 232 (e.g., direct contact coolers and / or indirect coolers, such as heat exchangers), such as described above with reference to FIGS. 2-5, may be housed in the CTD 24 in a variety of ways, depending on cooling demands and gas composition and concentration levels. For example, FIG. 6 illustrates one possible configuration of the one or more coolers 232. For purposes of orientation in the drawings, reference may be made to position 1, position 2, position 3, and position 4 to demonstrate various possible configurations of the one or more coolers 232 housed within the CTD 24. Such references are for demonstration purposes only. Further, some embodiments may include more or less than four coolers or cooler positions.

[0044] As illustrated in FIG. 6, the exhaust gas 62 may enter the exhaust stack 28. If the flow control valve 38 is shut and the flow control valve 39 is open, then the exhaust gas may be free to flow into the CTD 24. In the embodiment illustrated in FIG.6, the vertical media cooler 466 is in position 1. Downstream of the vertical media cooler 466 may be the horizontal spray cooler 460 in position 2. Downstream of the horizontal spray cooler 460 may be the vertical spray cooler 472 in position 3. Downstream of the vertical spray cooler 472 is another vertical media cooler 466 in position 4. In this way, as the exhaust gas 62 moves downstream through CTD 24, it may be cooled throughout the CTD 24 by contact with the coolant dispersed via the various coolers 232 (e.g., coolers 460, 466, and 472). Excess coolant 464 may be drained via the drain system 240. The cooled exhaust gas 62, 218 may then be directed to the gas treatment system 18 and / or the EGR system 60.

[0045] Although FIG. 6 illustrates one possible configuration of the one or more contact coolers 232, Table 1 presents other various configurations of the one or morecontact coolers 232. The following scenarios indicate each of the coolers 460, 466, and 472 as being in position 1, position 2, position 3, position 4, or any combination thereof. As previously mentioned, the configurations represented in FIG. 6 and Table 1 are not exhaustive and may include additional configurations not presented in this disclosure.Table 1: Embodiments of Cooler Configurations

[0046] As indicated above, the disclosed embodiments include multiple scenarios for the coolers 232 (e g., 460, 466, 472) in the CTD 24. Additional scenarios are also contemplated using other cooler ty pes and configurations.

[0047] Technical effects of the disclosed embodiments enable a combination of coolers 232 with a converging duct 234 of the CTD 24, thereby reducing or eliminating the need for a separate cooling system between the exhaust stack 28 and the gas treatment system 18 and / or the EGR system 60. In other words, the coolers 232 use the same footprint as the converging duct 234 of the CTD 24, rather than consuming additional space at a power plant site where space may be limited. Thus, the coolers 232 and converging duct 234 simultaneously cool and converge the flow of exhaust gas62 prior to deliver}' to the gas treatment system 18 and / or the EGR system 60. The coolers 232 may include only direct contact coolers, only indirect coolers, or a combination of both direct contact coolers and indirect coolers. Additionally, the direct contact coolers may direct the coolant into the exhaust gas 62 in the horizontal direction 480 (e.g., upstream and / or downstream directions) and / or the vertical direction 482 (e.g., upward and / or downward directions).

[0048] The subject matter described in detail above may be defined by one or more clauses, as set forth below'.

[0049] A system, includes a heat recovery steam generator (HRSG) configured to generate steam using heat from an exhaust gas, an exhaust stack disposed downstream of the ITRSG, and a cooling transition duct disposed dow nstream of the exhaust stack. The cooling transition duct includes a converging duct that decreases in a cross- sectional area in a flow direction from an inlet to an outlet of the converging duct. The cooling transition duct also includes one or more coolers disposed in the converging duct. The one or more coolers are configured to cool the exhaust gas within the converging duct between the inlet and the outlet. The cooling transition duct is configured to direct cooled exhaust gas to a gas capture system, an exhaust gas recirculation (EGR) system, or both.

[0050] The system of the preceding clause, further including a cooling system having the one or more coolers, a coolant supply system configured to supply a coolant to the one or more coolers, a controller configured to control the cooling system, and one or more sensors in the coolant supply system and / or the converging duct.

[0051] The system of any preceding clause, wherein the one or more coolers include one or more direct contact coolers configured to directly contact a coolant with the exhaust gas within the converging duct to cool the exhaust gas.

[0052] The system of any preceding clause, wherein the one or more direct contact coolers include a spray cooler, a media cooler, or a combination thereof.

[0053] The system of any preceding clause, wherein cooling transition duct includes a drain system configured to collect excess coolant for recirculation to a coolant supply system coupled to the one or more coolers.

[0054] The system of any preceding clause, wherein the one or more direct contact coolers are configured to scrub the exhaust gas.

[0055] The system of any preceding clause, wherein the one or more coolers include one or more indirect coolers configured to indirectly transfer heat between a coolant and the exhaust gas from the HRSG.

[0056] The system of any preceding clause, wherein the one or more coolers are configured to cool the exhaust gas to reduce or eliminate an increase in flow velocity7caused by the decrease in the cross-sectional area from the inlet to the outlet of the converging duct.

[0057] The system of any preceding clause, further including the gas capture system, wherein the gas capture system includes a carbon capture system.

[0058] A system includes a controller configured to control a gas capture system of a gas treatment system to capture an undesirable gas from a gas. The controller is further configured to monitor one or more sensors coupled to a cooling transition duct, wherein the cooling transition duct is located downstream of an exhaust stack located downstream of a heat recovery steam generator (HRSG), wherein the HRSG is configured to generate steam using heat from an exhaust gas. The cooling transition duct includes one or more coolers in a converging duct that decreases in a cross- sectional area in a flow direction from an inlet to an outlet of the converging duct, wherein the one or more coolers are configured to cool the exhaust gas within the converging duct between the inlet and the outlet. The cooling transition duct is configured to direct cooled exhaust gas to the gas capture system, an exhaust gas recirculation system, or both.

[0059] The system of any preceding clause, wherein the controller is configured to control a cooling system having the one or more coolers, and a coolant supply system configured to supply a coolant to the one or more coolers.

[0060] The system of any preceding clause, wherein the one or more sensors are temperature sensors, flow rate sensors, pressure sensors, gas composition sensors, or any combination thereof.

[0061] The system of any preceding clause, wherein the one or more coolers include one or more direct contact coolers configured to directly contact a coolant with the exhaust gas within the converging duct to cool the exhaust gas.

[0062] The system of any preceding clause, wherein the one or more coolers include a media cooler, a spray cooler, or a combination thereof.

[0063] The system of any preceding clause, wherein the controller is configured to control the one or more coolers based on sensor feedback from the one or more sensors coupled to the cooling transition duct.

[0064] The system of any preceding clause, wherein the undesirable gas includes carbon dioxide (CO2).

[0065] The system of any preceding clause, wherein the gas capture system includes a sorbent-based gas capture system, a solvent-based gas capture system, or both.

[0066] A method is provided for retrofitting a combined cycle power plant with a gas capture system of a gas treatment system and / or an exhaust gas recirculation (EGR) system. The method includes forming an opening in a side wall of an exhaust stack downstream of a heat recovery steam generator (HRSG). The method further includes adding a cooling transition duct to the opening in the side wall of the exhaust stack, wherein the cooling transition duct includes one or more coolers coupled to a converging duct that decreases in a cross-sectional area in a flow direction from an inlet to an outlet of the converging duct, wherein the one or more coolers are configured to cool an exhaust gas within the converging duct upstream from the gas capture systemof the gas treatment system and / or the EGR system. The method further includes coupling a coolant supply system to the one or more coolers of the cooling transition duct.

[0067] The method of the preceding clause, wherein the one or more coolers include direct contact coolers configured to directly contact a coolant with the exhaust gas within the converging duct to cool the exhaust gas.

[0068] The system of any preceding clause, wherein the one or more direct contact coolers are configured to scrub the exhaust gas.

[0069] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims

CLAIMS:

1. A system, comprising: a heat recovery steam generator (HRSG) configured to generate steam using heat from an exhaust gas; an exhaust stack disposed downstream of the HRSG; and a cooling transition duct disposed downstream of the exhaust stack, wherein the cooling transition duct comprises: a converging duct that decreases in a cross-sectional area in a flow direction from an inlet to an outlet of the converging duct; and one or more coolers disposed in the converging duct, wherein the one or more coolers are configured to cool the exhaust gas within the converging duct between the inlet and the outlet, and the cooling transition duct is configured to direct cooled exhaust gas to a gas capture system, an exhaust gas recirculation (EGR) system, or both.

2. The system of claim 1, comprising a cooling system having the one or more coolers, a coolant supply system configured to supply a coolant to the one or more coolers, a controller configured to control the cooling system, and one or more sensors in the coolant supply system and / or the converging duct.

3. The system of claim 1, wherein the one or more coolers comprise one or more direct contact coolers configured to directly contact a coolant with the exhaust gas within the converging duct to cool the exhaust gas.

4. The system of claim 3, wherein the one or more direct contact coolers comprise a spray cooler, a media cooler, or a combination thereof.

5. The system of claim 3, wherein cooling transition duct comprises a drain system configured to collect excess coolant for recirculation to a coolant supply system coupled to the one or more coolers.

6. The system of claim 1, wherein the one or more direct contact coolers are configured to scrub the exhaust gas.

7. The system of claim 1, wherein the one or more coolers comprise one or more indirect coolers configured to indirectly transfer heat between a coolant and the exhaust gas from the HRSG.

8. The system of claim 1, wherein the one or more coolers are configured to cool the exhaust gas to reduce or eliminate an increase in flow velocity caused by the decrease in the cross-sectional area from the inlet to the outlet of the converging duct.

9. The system of claim 1, comprising the gas capture system, wherein the gas capture system comprises a carbon capture system.

10. A system, comprising: a controller configured to: control a gas capture system of a gas treatment system to capture an undesirable gas from a gas; and monitor one or more sensors coupled to a cooling transition duct, wherein the cooling transition duct is located downstream of an exhaust stack located downstream of a heat recovery steam generator (HRSG), wherein the HRSG is configured to generate steam using heat from an exhaust gas, wherein the cooling transition duct comprises one or more coolers in a converging duct that decreases in a cross-sectional area in a flow direction from an inlet to an outlet of the converging duct, wherein the one or more coolers are configured to cool the exhaust gas within the converging duct between the inlet and the outlet, and wherein the cooling transition duct is configured to direct cooled exhaust gas to the gas capture system, an exhaust gas recirculation system, or both.

11. The system of claim 10, wherein the controller is configured to control a coolingsystem having the one or more coolers, and a coolant supply system configured to supply a coolant to the one or more coolers.

12. The system of claim 10, wherein the one or more sensors are temperature sensors, flow rate sensors, pressure sensors, gas composition sensors, or any combination thereof.

13. The system of claim 10, wherein the one or more coolers comprise one or more direct contact coolers configured to directly contact a coolant with the exhaust gas within the converging duct to cool the exhaust gas.

14. The system of claim 13, wherein the one or more coolers comprise a media cooler, a spray cooler, or a combination thereof.

15. The system of claim 13, wherein the controller is configured to control the one or more coolers based on sensor feedback from the one or more sensors coupled to the cooling transition duct.

16. The system of claim 10, wherein the undesirable gas comprises carbon dioxide (CO2).

17. The system of claim 10, wherein the gas capture system comprises a sorbentbased gas capture system, a solvent-based gas capture system, or both.

18. A method of retrofitting a combined cycle power plant with a gas capture system of a gas treatment system and / or an exhaust gas recirculation (EGR) system, the method comprising: forming an opening in a side wall of an exhaust stack downstream of a heat recovery steam generator (HRSG); adding a cooling transition duct to the opening in the side wall of the exhaust stack, wherein the cooling transition duct comprises one or more coolers coupled to a converging duct that decreases in a cross-sectional area in a flow direction from an inletto an outlet of the converging duct, wherein the one or more coolers are configured to cool an exhaust gas within the converging duct upstream from the gas capture system of the gas treatment system and / or the EGR system; and coupling a coolant supply system to the one or more coolers of the cooling transition duct.

19. The method of claim 18, wherein the one or more coolers comprise direct contact coolers configured to directly contact a coolant with the exhaust gas within the converging duct to cool the exhaust gas.

20. The system of claim 19. wherein the one or more direct contact coolers are configured to scrub the exhaust gas.

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