Combined cycle power plant with reduced parasitic pumping losses

Abstract

A combined cycle power plant (CCPP) is provided. The CCPP includes a gas turbine having a compressor section, a combustion section, and a turbine section. The CCPP further includes a heat recovery steam generator (HRSG) having a first economizer. The HRSG receives an exhaust gas flow from the turbine section. The HRSG further includes a fuel heating system having a fuel supply line and a high-temperature heat exchanger disposed in thermal communication with the fuel supply line. The fuel supply line is fluidly coupled to the combustion section. The high-temperature heat exchanger is fluidly coupled to the first economizer such that the high-temperature heat exchanger receives water from the first economizer. The CCPP further includes a feedwater pump fluidly coupled to the high-temperature heat exchanger.

Description

[Technical Field]

[0001] The present disclosure relates generally to combined cycle power plant systems, and more particularly to combined cycle power plant systems having a fuel heating system with reduced parasitic pumping losses. [Background technology]

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

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

[0004] In many HRSG systems, water from one or more sections of the HRSG may be diverted and used in a fuel heating circuit to preheat fuel (e.g., via a heat exchanger). The preheated fuel may then be supplied to the combustion section of the gas turbine. The water pressure in the fuel heating circuit must be high enough to ensure that the water remains in the liquid phase at the hottest operating conditions.

[0005] Known fuel heating systems are therefore configured to supply water to the fuel heater at a pressure sufficient to prevent flashing. Spent water from the fuel heater is recovered in the feedwater circuit, either in the condensate line supplying the low-pressure economizer or in the condenser hot well. The power required to repressurize this water for heating in the HRSG and return the reheated water to the fuel heater represents a parasitic loss to the performance benefit of capturing low-grade exhaust energy in the fuel. As the target temperature of the heated fuel increases, the water pressure must increase exponentially. As a result, the parasitic power lost in repressurizing and circulating water to heat the fuel represents a significant burden on CCPP performance.

[0006] Therefore, an improved HRSG system with a fuel heating circuit that reduces parasitic pumping losses compared to conventional designs is desired and would be appreciated by those skilled in the art. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] U.S. Patent No. 1,130,0011 Summary of the Invention

[0008] Aspects and advantages of the combined cycle power plant and feedwater pump control system according to the present disclosure will be set forth in part in the description that follows, or will be obvious from the description, or may be learned by practice of the present teachings.

[0009] According to one embodiment, a combined cycle power plant (CCPP) is provided. The CCPP includes a gas turbine having a compressor section, a combustion section, and a turbine section. The CCPP further includes a heat recovery steam generator (HRSG) having a first economizer. The HRSG receives an exhaust gas flow from the turbine section. The HRSG further includes a fuel heating system having a fuel supply line and a high-temperature heat exchanger disposed in thermal communication with the fuel supply line. The fuel supply line is fluidly coupled to the combustion section. The high-temperature heat exchanger is fluidly coupled to the first economizer such that the high-temperature heat exchanger receives water from the first economizer. The CCPP further includes a feedwater pump fluidly coupled to the high-temperature heat exchanger.

[0010] According to another embodiment, a combined cycle power plant (CCPP) is provided. The CCPP includes a gas turbine having a compressor section, a combustion section, and a turbine section. The CCPP further includes a heat recovery steam generator (HRSG) that receives an exhaust gas flow from the turbine section. The HRSG includes a high-pressure economizer and a low-pressure economizer. The CCPP further includes a fuel heating system having a fuel supply line, a high-temperature heat exchanger, and a low-temperature heat exchanger. The fuel supply line is fluidly coupled to the combustion section. The high-temperature heat exchanger and the low-temperature heat exchanger are disposed in thermal communication with the fuel supply line. The high-temperature heat exchanger is fluidly coupled to the high-pressure economizer, and the low-temperature heat exchanger is fluidly coupled to the low-pressure economizer. The CCPP further includes a feedwater pump fluidly coupled to the high-temperature heat exchanger.

[0011] According to yet another embodiment, a feedwater pump control system is provided. The feedwater pump control system includes a heat recovery steam generator (HRSG) having a low-pressure economizer and at least one high-pressure economizer. The feedwater pump control system further includes a fuel heating system having a fuel supply line fluidly coupled to the combustion section. The fuel heating system further includes a high-temperature heat exchanger and a low-temperature heat exchanger disposed in thermal communication with the fuel supply line. The feedwater pump control system further includes a feedwater pump having multiple stages. A first pump supply line extends between one of the low-pressure economizer, the low-pressure steam drum, or the deaerator and an initial stage of the multiple stages. A second pump supply line extends between the high-temperature heat exchanger and an intermediate stage of the multiple stages. A feedwater supply line extends between a final stage of the multiple stages and the at least one high-pressure economizer. The feedwater pump control system further includes sensors disposed in one or more of the first pump supply line, the second pump supply line, and the feedwater supply line. The one or more sensors are configured to provide data indicative of at least one of water pressure, temperature, or flow rate. One or more valves are disposed in one or more of the second pump supply line and the first feedwater supply line. The feedwater pump control system further includes a controller communicatively coupled to the one or more sensors and operably coupled to the one or more valves. The controller includes a memory and one or more processors. The memory stores instructions that, when executed by the one or more processors, cause the feedwater pump control system to perform operations. The operations include monitoring, via the one or more sensors, data indicative of a temperature difference between water entering the feedwater pump and water exiting the feedwater pump. The operations further include determining when the temperature difference exceeds a predetermined temperature range. The operations further include activating one or more valves to adjust the flow of water to the feedwater pump to restore the temperature difference to within the predetermined temperature range.

[0012] These and other features, aspects, and advantages of the present combined cycle power plant and feedwater pump control system will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present technology and, together with the description, serve to explain the principles of the technology.

[0013] A full and enabling disclosure of the present combined cycle power plant and feedwater pump control system, including the best mode of making and using the present system and method, directed to one of ordinary skill in the art, is set forth in this specification, which makes reference to the accompanying drawings. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram of a combined cycle power plant (CCPP) according to an embodiment of the present disclosure. [Figure 2] 1 is a schematic diagram of a combined cycle power plant (CCPP) according to an embodiment of the present disclosure. [Figure 3] FIG. 1 is a schematic diagram of a feedwater pump control system according to an embodiment of the present disclosure. [Figure 4] 1 is a schematic diagram of a combined cycle power plant (CCPP) according to an embodiment of the present disclosure. [Figure 5] 1 is a schematic diagram of a combined cycle power plant (CCPP) according to an embodiment of the present disclosure. [Figure 6] 1 is a schematic diagram of a combined cycle power plant (CCPP) according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

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

[0016] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Additionally, unless otherwise specified, all embodiments described herein should be considered exemplary.

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

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

[0019] As used herein, the terms "upstream" and "downstream" refer to relative directions with respect to fluid flow in a fluid pathway. For example, "upstream" refers to the direction from which fluid flows, and "downstream" refers to the direction to which fluid flows. However, the terms "upstream" and "downstream" as used herein can also refer to the flow of electricity. The terms "forward" and "aft" refer to locations relative to the inlet and outlet, respectively, of a system (such as a turbomachine or heat recovery steam generator), with the system having components near the inlet considered "forward" and components near the outlet considered "aft."

[0020] The term "radially" refers to a relative direction that is substantially perpendicular to the axial centerline of a particular component, the term "axially" refers to a relative direction that is substantially parallel to and / or coaxially aligned with the axial centerline of a particular component, and the term "circumferentially" refers to a relative direction that extends around the axial centerline of a particular component.

[0021] Approximate terms such as "approximately," "about," "generally," and "substantially" are not intended to be limited to the exact value stated. In at least some cases, approximating language can correspond to the precision of an instrument for measuring a value or the precision of a method or machine for constructing or manufacturing a component and / or system. In at least some cases, approximating language can correspond to the precision of an instrument for measuring a value or the precision of a method or machine for constructing or manufacturing a component and / or system. For example, approximating language can refer to within a margin of 1, 2, 4, 5, 10, 15, or 20% of an individual value, a range of values, and / or any of the endpoints defining the range of values. When used in the context of angles or directions, such terms include a range of plus or minus 10 degrees of the stated angle or direction. For example, "approximately vertical" includes directions within 10 degrees of any direction, e.g., clockwise or counterclockwise, from vertical.

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

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

[0024] As used herein, "line" refers to a pipe, hose, or any other suitable fluid conduit or ductwork through which a fluid flows.

[0025] As used herein, the terms "high," "mid," and "low," or their respective comparatives (such as ~er, where applicable), when used in the context of system components, may refer to parameters associated with a particular system component as compared to other system components. For example, a low-pressure economizer, a medium-pressure economizer, and a high-pressure economizer may be defined relative to one another (i.e., the low-pressure economizer delivers fluid at a lower pressure relative to the medium / high-pressure economizer, etc.).

[0026] 1, 2, and 4-6 each illustrate a schematic flow diagram of an embodiment of a combined cycle power generation system, or combined cycle power plant (CCPP) 10, in accordance with an embodiment of the present disclosure. The CCPP 10 may include a gas turbine 12 for driving a first load 14. The first load 14 may be, for example, a generator for generating electrical power. The gas turbine 12 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.

[0027] During operation of the gas turbine 12, a working fluid, such as air, enters the compressor section 20, where it is progressively compressed, thus providing compressed air to the combustors in the combustion section 18. The compressed air is mixed with fuel and combusted in each combustor to generate combustion gases. The combustion gases pass through a hot gas path from the combustion section 18 to the turbine section 16, where energy (kinetic and / or thermal energy) is transferred from the combustion gases to rotor blades, thereby rotating one or more shafts 21. This mechanical rotational energy can then be used to power the compressor section 20 and / or generate electricity. Heated exhaust gases 34 exiting the turbine section 16 can then be exhausted from the gas turbine 12 via the exhaust section and enter a heat recovery steam generator (HRSG) 32, where heat is transferred between the heated exhaust gases 34 and various components of the HRSG. As such, the HRSG 32 may receive a flow of exhaust gases 34 from the turbine section 16 at the inlet 31, and the flow of exhaust gases 34 may be conveyed through the HRSG 32, via the various components contained therein, to the outlet 33. The exhaust gases 34 may exit the HRSG 32 to the atmosphere via the exhaust stack 105.

[0028] The CCPP 10 may also include a steam turbine system 22 for driving a second load 24. The second load 24 may be a generator for generating electrical power. However, both the first load 14 and the second load 24 may be other types of loads that are drivable by the gas turbine 12 and the steam turbine system 22. Furthermore, while the gas turbine 12 and the steam turbine system 22 may drive separate loads 14, 24 as shown in the illustrated embodiment, the gas turbine 12 and the steam turbine system 22 may also be utilized in tandem to drive a single load via a single shaft.

[0029] In the illustrated embodiment, the steam turbine system 22 may include one low-pressure (LP) steam turbine 26, one intermediate-pressure (IP) steam turbine 28, and one high-pressure (HP) steam turbine 30. The low-pressure (LP) steam turbine 26, the intermediate-pressure (IP) steam turbine 28, the high-pressure (HP) steam turbine 30, and the load 24 may each be disposed on one or more shafts 23 (such as a common shaft in some embodiments). In other embodiments, the LP steam turbine 26, the IP steam turbine 28, and the HP steam turbine 30 may be disposed on separate shafts (which may be coupled to one another). In some embodiments, the LP steam turbine 26 and the IP steam turbine 28 may be disposed on a common shaft of one or more shafts to form an LP / IP steam turbine, and the HP steam turbine 30 may be on a separate shaft or may not be included in the system.

[0030] The CCPP 10 may also include an HRSG 32 having multiple stages. The components of the HRSG 32 in the illustrated embodiment are a simplified diagram of the HRSG 32 and are not intended to be limiting. Rather, the illustrated HRSG 32 is shown to communicate the general operation of such an HRSG system. Heated exhaust gas 34 from the gas turbine 12 is transported to the HRSG 32 and can be used to heat steam used to power the steam turbine system 22.

[0031] Exhaust from the low-pressure steam turbine 26 of the steam turbine system 22 may be directed to a condenser 36. Condensate from the condenser 36 may then be directed to the low-pressure section of the HRSG 32 via a condensate pump 38. The condensate may then flow through a low-pressure economizer 40 (LPECON), which may be used to heat the condensate. For example, a condensate supply line 80 may extend between and fluidly couple the condenser 36 and the LPECON 40. The condensate pump 38 may be disposed in fluid communication with the condensate supply line 80.

[0032] From the low-pressure economizer 40, the condensate (e.g., water) may be directed into the low-pressure evaporator 42 (LPEVAP), to the feedwater pump 45, and / or to the low-temperature fuel heating heat exchanger 208 (FIGS. 1 and 2). From the feedwater pump 45, the feedwater may flow to either the IPECON 44 or the aft high-pressure economizer 49 (HPECON), e.g., via two separate pipes, tubes, or fluid conduits. For example, a first feedwater supply line 126 may extend from the feedwater pump 45 to the aft HPECON 49, and a second feedwater line 128 may extend from the feedwater pump 45 to the IPECON 44. From the intermediate-pressure economizer 44, the feedwater may be directed to the intermediate-pressure evaporator 46 (IPEVAP). Additionally, from the aft HPECON 49, the condensate may flow to the forward high-pressure economizer (HPECON) 48. It should be understood that the embodiments shown in Figures 1-5 may include multiple economizers, and the term "economizer" may refer to any one of multiple economizers, such as LPECON 40, IPECON 44, aft HPECON 49, or forward HPECON 48.

[0033] In many embodiments, the CCPP 10 may further include a low-pressure superheater 130 disposed within the HRSG 32. The low-pressure superheater 130 may be a heat exchanger that transfers heat between steam flowing therethrough and the exhaust gas 34 flowing through the HRSG 32. The low-pressure superheater 130 may receive steam from the LPEVAP 42 (and subsequently superheat the steam). The steam from the low-pressure superheater 130, along with steam from the exhaust of the intermediate-pressure steam turbine 28, may be mixed and supplied to the low-pressure steam turbine 26. For example, a connecting line 132 may fluidly couple an outlet of the intermediate-pressure steam turbine 28 to an inlet of the low-pressure steam turbine 26. An outlet line 134 extends from the low-pressure superheater 130 to the connecting line 132, thereby fluidly coupling the low-pressure superheater 130 to the connecting line 132. It should be noted that while Figures 1-5 each illustrate steam turbine systems 22 having separate IP and LP turbine casings connected by intersecting pipes, it should be understood that the steam turbine system may combine a single IP / LP turbine casing (with interstage admission of LP steam) without departing from the scope and / or spirit of the present disclosure.

[0034] Similarly, the CCPP 10 may further include an intermediate-pressure superheater 70 disposed within the HRSG 32. The intermediate-pressure superheater 70 may be a heat exchanger that transfers heat between steam flowing therethrough and the exhaust gas 34 flowing through the HRSG 32. The intermediate-pressure superheater 70 may receive steam from (and subsequently superheat) the IPEVAP 46. In some embodiments, the intermediate-pressure superheater 70 may be disposed within the HRSG 32 upstream (e.g., immediately upstream or directly upstream) of the low-pressure superheater 130 with respect to the flow of the heated exhaust gas 34 through the HRSG 32. The steam from the intermediate-pressure superheater 70, along with steam from the exhaust of the high-pressure steam turbine 30, may be mixed and supplied to the primary reheater 58. For example, an outlet line 118 may extend from the intermediate-pressure superheater 70 to a junction with an outlet line 124 of the high-pressure steam turbine 30.

[0035] Each economizer described herein (e.g., LPECON 40, IPECON 44, aft HPECON 49, and forward HPECON 48) may be a device configured to heat feedwater or condensate with heated exhaust gas 34. As such, LPECON 40, IPECON 44, aft HPECON 49, and forward HPECON 48 may be heat exchangers that transfer heat between the heated exhaust gas 34 generated by gas turbine 12 and water used in steam turbine system 22. HRSG 32 may include multiple economizers arranged in serial flow order (from upstream to downstream with respect to the flow of exhaust gas 34 through HRSG 32): forward HPECON 48, IPECON 44, aft HPECON 49, and LPECON 40. In this arrangement, forward HPECON 48 may be located upstream of IPECON 44 within HRSG 32. IPECON 44 may be located upstream of aft HPECON 49 within HRSG 32. The aft HPECON 49 may be located upstream of the LPECON 40 within the HRSG 32. In general, the operating temperature of the economizer may decrease from the front end to the aft end of the HRSG 32 (e.g., an economizer closer to the front end of the HRSG 32 operates at a higher temperature than an economizer closer to the aft end of the HRSG 32).

[0036] Finally, feedwater from the forward high-pressure economizer 48 may be directed into a high-pressure evaporator 50 (HPEVAP) and / or a high-temperature fuel heating heat exchanger 206. Steam exiting the high-pressure evaporator 50 may be directed to a primary high-pressure superheater 52 and a finishing high-pressure superheater 54, where the steam is superheated and ultimately delivered to the high-pressure steam turbine 30 of the steam turbine system 22. Each of the superheaters 52, 54 may be a heat exchanger that transfers heat from the heated exhaust gas 34 from the gas turbine 12 flowing through the HRSG 32 to the steam used in the steam turbine system 22.

[0037] The interstage desuperheater 56 may be located in fluid communication between the primary high-pressure superheater 52 and the finishing high-pressure superheater 54. The interstage desuperheater 56 may enable more robust control of the discharge temperature of the steam from the finishing high-pressure superheater 54. Specifically, the interstage desuperheater 56 may be configured to control the temperature of the steam exiting the finishing high-pressure superheater 54 by injecting a cold feedwater spray into the superheated steam from upstream of the finishing high-pressure superheater 54 whenever the discharge temperature of the steam exiting the finishing high-pressure superheater 54 exceeds a predetermined value. For example, the cold feedwater spray may be water from the forward HPECON 48. Notably, the interstage desuperheater 56 may be in fluid communication with the HPECON via a first desuperheater cooling line 160.

[0038] Additionally, exhaust from the high-pressure steam turbine 30 of the steam turbine system 22 may be mixed with intermediate-pressure steam from the intermediate-pressure superheater 70 and both may be directed into the primary reheater 58 and the finish reheater 60, where they may be reheated before being directed into the intermediate-pressure steam turbine 28 of the steam turbine system 22. The primary reheater 58 may be fluidly coupled to the finish reheater 60 via a reheater connection line. The reheater connection line may extend between and fluidly couple the primary reheater 58 and the finish reheater 60.

[0039] In various embodiments, the primary reheater 58 and the finish reheater 60 may also be associated with an interstage desuperheater 62 for controlling the discharge steam temperature from the finish reheater 60. Specifically, the interstage desuperheater 62 may be configured to control the temperature of the steam exiting the finish reheater 60 by injecting low-temperature feedwater spray into the superheated steam from upstream of the finish reheater 60 whenever the discharge temperature of the steam exiting the finish reheater 60 exceeds a predetermined value. For example, the interstage desuperheater 62 may be disposed in fluid communication with a reheater connecting line (e.g., between the primary reheater 58 and the finish reheater 60). The interstage desuperheater 62 may be fluidly coupled to the feedwater pump 45. In particular, the interstage desuperheater 62 may receive a portion of the water or condensate exiting the feedwater pump 45. For example, as shown, the interstage desuperheater 62 may receive a flow of water or condensate from the second feedwater line 128. In particular, the interstage desuperheater 62 may be in fluid communication with the second feedwater supply line 128 via the second desuperheater cooling line 162. It should be understood that the water used to control the temperature of the reheat steam (i.e., the water received by the interstage desuperheater 62) may come from anywhere on the medium-pressure or high-pressure feedwater circuit, including, but not limited to, the IPECON, and may be discharged into the medium-pressure drum or made into HP feedwater for reheating the desuperheater.

[0040] 1-6 each illustrate several valves 150, which are not individually numbered but are designated by common symbols throughout. For example, each of the valves 150 may be selectively actuated between an open position and a closed position. In the open position, fluid flowing through the line to which the valve 150 is attached may be unrestricted. In contrast, in the closed position, fluid flowing through the line to which the valve 150 is attached may be restricted. Each valve may be selectively actuated to a partially closed (or partially open) position, which allows the valve 150 to control the flow rate of fluid through the line to which the valve 150 is attached.

[0041] The generation cycle of the gas turbine 12 is often referred to as the "topping cycle," and the generation cycle of the HRSG 32 and steam turbine system 22 is often referred to as the "bottoming cycle." By combining these two cycles, as shown in Figures 1 through 6, the combined cycle power plant 10 can provide even greater combined plant efficiency. In particular, waste heat from the topping cycle can be captured and used to generate steam for use in the bottoming cycle.

[0042] The CCPP 10 advantageously recaptures heat from the heated exhaust gas 34 through the use of the HRSG 32. As shown in FIG. 1 , the gas turbine 12 and HRSG 32 components may be separated into separate functional units. In other words, the gas turbine 12 may generate heated exhaust gas 34 and direct the heated exhaust gas 34 toward the HRSG 32, which may be primarily responsible for recapturing heat from the heated exhaust gas 34 by generating superheated steam. The superheated steam may then be used as a power source by the steam turbine system 22. The heated exhaust gas 34 may be transported to the HRSG 32 through a series of ductwork, which may vary based on the specific design of the CCPP 10.

[0043] In many embodiments, CCPP 10 may further include a fuel heating system 200 for preheating fuel supplied to combustion section 18. For example, fuel heating system 200 may include a fuel supply line 202 fluidly coupled to combustion section 18. In many embodiments, fuel supply line 202 may extend between a fuel supply 204 (e.g., a tank, reservoir, or other fuel source) and combustion section 18. In the exemplary embodiment shown in FIGS. 1, 2, and 4-6, fuel heating system 200 may include a high-temperature heat exchanger 206 disposed in thermal communication with fuel supply line 202. For example, high-temperature heat exchanger 206 may exchange heat between fuel flowing through fuel supply line 202 and a thermal fluid. High-temperature heat exchanger 206 may be fluidly coupled to an economizer such that high-temperature heat exchanger 206 receives water from the economizer. In particular, as shown in FIGS. 1 and 2, the high temperature heat exchanger 206 may be in fluid communication with the forward high pressure economizer 48 via a high temperature input line 210 .

[0044] 1 and 2, the feedwater pump 45 may be fluidly coupled to one or more economizers such that the feedwater pump 45 receives water from one of the one or more economizers and supplies water to another one of the one or more economizers. For example, the feedwater pump 45 may be fluidly coupled (e.g., individually fluidly coupled) to the high-temperature heat exchanger 206, the low-pressure economizer 40, the intermediate-pressure economizer 44, and the aft-high-pressure economizer 49. In particular, the feedwater pump 45 may receive water from an outlet of the high-temperature heat exchanger 206 and from an outlet of the LPECON 40 (e.g., via one or more fluid conduits 211, 212).

[0045] 1 , the feedwater pump 45 may receive water from the low-pressure evaporator 42 (such as a low-pressure steam drum of the low-pressure evaporator) and / or the deaerator 41. In this manner, the feedwater pump 45 may be fluidly coupled to one of the economizer 40, the low-pressure evaporator 42, or the deaerator 41 such that the feedwater pump 45 receives water from one or more of the economizer 40, the low-pressure evaporator 42, or the deaerator 41. The deaerator 41 may be fluidly coupled to one or more water / steam-carrying components of the HRSG 32 and may be operable to remove dissolved gases from the water / steam.

[0046] The low-pressure economizer 40 may be fluidly coupled to a feedwater pump 45 via a first pump supply line 211, and the high-temperature heat exchanger may be fluidly coupled to the feedwater pump 45 via a second pump supply line 212. The first pump supply line 211 may extend (e.g., directly) between the LPECON 40 and the feedwater pump 45. Similarly, the second pump supply line 212 may extend (e.g., directly) between the high-temperature heat exchanger 206 and the feedwater pump 45, such that the feedwater pump 45 can receive spent thermal fluid from the high-temperature heat exchanger 206 (e.g., water from the high-temperature heat exchanger 206 that has undergone energy transfer).

[0047] In such an embodiment, the feedwater pump 45 may receive a first flow of water from the outlet of the LPECON 40 (via supply line 211) and a second flow of water from the high-temperature heat exchanger 206 (via supply line 212). By returning water from the high-temperature heat exchanger 206 to the feedwater pump 45, parasitic pumping losses are significantly reduced compared to conventional designs. For example, the pressure required to circulate water to (and through) the high-temperature heat exchanger 206, and the power consumed, may be approximately matched (e.g., equalized) to the actual friction losses through the circuit in which the high-temperature heat exchanger 206 is located.

[0048] Water may flow from the feedwater pump 45 to the IPECON 44, the aft high-pressure economizer 49, and / or the interstage desuperheaters 56 and 62, e.g., via separate pipes, tubes, or fluid conduits. For example, a first feedwater supply line 126 may extend from the feedwater pump 45 to the aft high-pressure economizer 49, and a second feedwater line 128 may extend from the feedwater pump 45 to the IPECON 44. Further, the interstage desuperheater 62 may be in fluid communication with the second feedwater supply line 128 via a second desuperheater cooling line 162. Alternatively, or in addition, the interstage desuperheater 56 may receive water from the feedwater pump 45 (e.g., from the first feedwater supply line 126).

[0049] 1 and 2 , the fuel heating system 200 may further include a low-temperature heat exchanger 208 disposed in thermal communication with the fuel supply line 202, upstream of the high-temperature heat exchanger 206 relative to the flow of fuel through the fuel supply line 202. The low-temperature heat exchanger 208 may operate at a lower temperature than the high-temperature heat exchanger 206. In many embodiments, a low-temperature input line 216 may fluidly couple and extend between the LPECON 40 and the low-temperature heat exchanger 208. Additionally, a low-temperature output line 218 may fluidly couple and extend between the low-temperature heat exchanger 208 and the condensate supply line 80. In some embodiments, as shown in FIG. 1 , the low-temperature output line 218 may be fluidly coupled to the condensate supply line 80, downstream of the condensate pump 38 relative to the flow of water through the condensate supply line 80. In other embodiments, as shown in FIG. 2, the cold output line 218 may be fluidly coupled to the condensate supply line 80 upstream of the condensate pump 38 relative to the flow of water through the condensate supply line 80 .

[0050] 1 , a low temperature bypass line 220 may fluidly couple the low temperature input line 216 to the condensate supply line 80. One or more valves 150 may be disposed in fluid communication with the low temperature bypass line 220, such that the amount (and / or flow rate) of water entering the low temperature heat exchanger 208 can be regulated by the one or more valves 150 disposed in the low temperature bypass line 220. Additionally, in many embodiments, a low temperature pump 222 may be disposed in fluid communication with the low temperature input line 216.

[0051] 3, a feedwater pump control system 600 according to an embodiment of the present disclosure is illustrated. For example, the feedwater pump control system 600 may be used in the CCPP 10 described above with reference to FIGS. 1-2.

[0052] 3 , the feedwater pump control system 600 may include a heat recovery steam generator 32 that includes a low-pressure economizer 40, an intermediate-pressure economizer 44, an aft-high-pressure economizer 49, and a forward-high-pressure economizer 48 (shown in opposing positions for simplicity). The feedwater pump control system 600 may further include a fuel heating system 200 that includes a fuel supply line 202 fluidly coupled to the combustion section 18 of the gas turbine 12. The fuel heating system 200 further includes a high-temperature heat exchanger 206 and a low-temperature heat exchanger 208 disposed in thermal communication with the fuel supply line 202.

[0053] In an exemplary embodiment, the feedwater pump control system 600 may be implemented in the CCPP 10 described above with reference to Figures 1 and 2. In particular, the heat recovery steam generator 32 shown in Figure 3 is intended to illustrate which components may be included in the system, independent of gas flow. In contrast, Figures 1, 2, and 4-6 illustrate the placement of the various components of the HRSG 32 as they relate to the exhaust gases 34 flowing through the HRSG 32 (where the exhaust gases 34 flow from left to right).

[0054] In an exemplary embodiment, the feedwater pump control system 600 may include a feedwater pump 45 having multiple stages 602. For example, the feedwater pump 45 may be a multi-stage pump having multiple stages 602. The feedwater pump 45 may include a motor 610 coupled to a shaft 612. The shaft 612 may be coupled to one or more impellers (e.g., one impeller per stage), such that water flowing through the multi-stage feedwater pump 45 experiences a progressive increase in pressure as it flows from stage to stage. The multiple stages 602 may include one or more initial stages, including a first stage 604 (or a suction side stage), two or more intermediate stages 606, and one or more subsequent stages, including a final or last stage 608. The pressure of the water in each stage of the multiple stages 602 of the feedwater pump 45 may progressively increase from the first stage 604, through each intermediate stage 606, to the last stage 608. Although the embodiment shown in FIG. 3 depicts feedwater pump 45 having 11 stages, it should be understood that feedwater pump 45 may have any number of stages, and the present disclosure is not limited to any particular number of stages unless specifically recited in the claims.

[0055] In many embodiments, the first pump supply line 211 may extend between and fluidly couple the LPECON 40 and the first stage 604 of the plurality of stages 602. That is, water from an outlet of the LPECON 40 may be supplied to the first stage 604 of the plurality of stages 602 (e.g., via the first inlet). The second pump supply line 212 may extend between and fluidly couple the high-temperature heat exchanger 206 and the first intermediate stage 606. In many embodiments, the first feedwater supply line 126 may extend between and fluidly couple the final stage 608 of the plurality of stages 602 and the aft-high-pressure economizer 49. In this manner, at least a portion of the water from the final stage 608 of the feedwater pump 45 may be supplied to the aft-high-pressure economizer 49. Additionally, the second feedwater supply line 128 may extend between and fluidly couple the second intermediate stage 606 of the plurality of stages 602 and the intermediate-pressure economizer 44.

[0056] By way of example only, the feedwater pump 45 may include initial stages including a first stage 604 and the first 25% of the stages, intermediate stages after the initial stages extending from 25% to 75% of the stages, and later stages after the intermediate stages extending over the last 25% of the stages and including a final stage 608. In the embodiment shown in FIG. 3 , the LPECON 40 may be fluidly coupled to the first stage 604, the IPECON 44 may be fluidly coupled to an intermediate stage 606 (such as the middle or sixth stage), the high-temperature heat exchanger 206 may be fluidly coupled to the later stage 606 (such as the second through last or tenth stage), and the aft high-pressure economizer 49 may be fluidly coupled to the final stage 608.

[0057] In an exemplary embodiment, a sensor 614 (designated with the symbol "S" in FIG. 3 ) may be disposed in one or more of the first pump supply line 211, the second pump supply line 212, the first feedwater supply line 126, and the second feedwater supply line 128. The sensor 614 may be configured to provide data indicative of at least one of the pressure, temperature, or flow rate of the water. The sensor 614 may provide data indicative of such parameters of the water flowing through the line to which the sensor is attached. For example, the sensor 614 disposed in the first pump supply line 211 may be configured to provide (e.g., to the controller 106) data indicative of at least one of the pressure, temperature, or flow rate of the water in the first pump supply line 211.

[0058] Additionally, in many embodiments, valves 150 may be disposed in one or more of the second pump supply line 212, the first feedwater supply line 126, and the second feedwater supply line 128. Each of the valves 150 may be selectively and independently actuated (e.g., by the controller 106) between an open position and a closed position. In the open position, fluid flowing through the line to which the valve 150 is attached may not be restricted. In contrast, in the closed position, fluid flowing through the line to which the valve 150 is attached may be restricted. Each valve may be selectively actuated to a partially closed (or partially open) position by command from the controller 106, thereby allowing the valve 150 to control the flow rate of fluid flowing through the line to which the valve 150 is attached.

[0059] In the exemplary embodiment, the feedwater pump control system 600 may further include a controller 106 communicatively coupled to the sensors 614 and operably coupled to the valves 150. For example, the controller 106 may independently actuate each of the valves 150. As shown in FIG. 3 , the controller 106 is depicted in a block diagram to illustrate suitable components that may be included in the controller 106. For example, the controller 106 may include one or more processors 114 and associated memory devices 116 configured to perform various computer-implemented functions (e.g., executing methods, steps, calculations, etc., and storing associated data as disclosed herein). Additionally, the controller 106 may also include a communications module 119 to facilitate communication between the controller 106 and the various components of the system 600. For example, the communications module 119 may be in communication with the sensors 614 and the valves 150.

[0060] Additionally, the communications module 119 may include a sensor interface (e.g., one or more analog-to-digital converters) that allows signals transmitted from one or more sensors 614 to be converted into signals that can be understood and processed by the processor 114. It should be understood that the sensors 614 may be communicatively coupled to the communications module 119 using any suitable means. For example, the sensors 614 may be coupled to the communications module 119 via a wired connection. However, in other embodiments, the sensors may be coupled to the communications module 119 via a wireless connection, such as by using any suitable wireless communication protocol known in the art.

[0061] As used herein, the term "processor" refers not only to integrated circuits referred to in the art as being included in a computer, but also to controllers, microcontrollers, microcomputers, programmable logic controllers (PLCs), application-specific integrated circuits, and other programmable circuits. Additionally, memory device 116 may generally include memory elements including, but not limited to, computer-readable medium (e.g., random access memory (RAM)), computer-readable non-volatile medium (e.g., flash memory), floppy disks, compact disk read-only memories (CD-ROMs), magneto-optical disks (MODs), digital versatile disks (DVDs), and / or other suitable memory elements.

[0062] Such memory device 116 may generally be configured to store suitable computer-readable instructions that, when executed by processor 114, configure controller 106 to perform various functions and / or operations, including, but not limited to, monitoring, via one or more sensors 614, data indicative of the temperature difference between the water entering and exiting feedwater pump 45. The operations may further include determining when the temperature difference exceeds a predetermined temperature range (or a predetermined temperature difference range). For example, controller 106 may determine when the temperature difference exceeds a maximum threshold of the predetermined temperature range or falls below a minimum threshold of the predetermined temperature range. In response to determining that the temperature difference exceeds the predetermined temperature range, controller 106 may operate one or more valves 150 to adjust the flow of water to feedwater pump 45 to remedy the temperature difference so that it is within the predetermined temperature range. The predetermined temperature range (i.e., the predetermined temperature difference between the water entering the feedwater pump 45 and the water leaving the feedwater pump 45) may be approximately ±30°F, or ±20°F, or approximately ±10°F, or approximately ±5°F, or the like.

[0063] For example, if the water entering the feedwater pump 45 via the second pump supply line 212 is too hot (e.g., the temperature difference between the water entering the feedwater pump 45 and the water leaving the feedwater pump 45 exceeds the maximum threshold of the predetermined temperature range of the feedwater pump 45), the controller 106 can operate the valve 150 in the second pump supply line 212 to restrict (or slow) the flow of water, thereby reducing the temperature in line 212 to closer to the fuel temperature entering the high temperature fuel heater 206. This acts to restore the temperature difference between the water entering and leaving the feedwater pump 45 so that it is within the predetermined temperature range. In contrast, when the water entering the feedwater pump 45 via the second pump supply line 212 is too cold (e.g., the temperature difference between the water entering the feedwater pump 45 and the water leaving the feedwater pump 45 is below the minimum threshold for the feedwater pump 45's predetermined temperature range), the controller 106 can operate the valve 150 in the second pump supply line 212 to not restrict the flowing water (or increase the flow rate), which causes the high-temperature heat exchanger 206 to increase the temperature of the water flowing through the second pump supply line 212 and restore the temperature difference between the water entering and leaving the feedwater pump 45 to be within the predetermined temperature range.

[0064] 2 and 4 , CCPP 10 may further include a bridge line 224 fluidly coupling and extending between first pump supply line 211 and condensate supply line 80. In such embodiments, bridge pump 226 and bridge valve 228 may be disposed in fluid communication with bridge line 224. Bridge line 224, bridge pump 226, and bridge valve 228 may enable more robust temperature control at feedwater pump 45 by selectively allowing water from first pump supply line 211 to be routed back into condensate supply line 80. This may further enable more robust temperature control of fuel heating system 200, e.g., more robust temperature control of low-temperature heat exchanger 208 in particular.

[0065] 4 , the fuel heating system 200 of the CCPP 10 is configured without the low-temperature heat exchanger 208. In this embodiment, the high-temperature heat exchanger 206 may be fluidly coupled to the forward high-pressure economizer 48. A high-temperature input line 210 may fluidly couple the forward high-pressure economizer 48 to the high-temperature heat exchanger 206. For example, the high-temperature input line 210 may extend between the forward high-pressure economizer 48 and the high-temperature heat exchanger 206 to supply high-temperature water to the high-temperature heat exchanger 206.

[0066] In such an embodiment, a recirculation line 214 may extend (e.g., extend directly) from the high-temperature heat exchanger 206 to the condensate supply line 80. The recirculation line 214 may at least partially fluidly couple the high-temperature heat exchanger 206 to the HRSG 32 downstream of an economizer (e.g., the forward high-pressure economizer 48) relative to the flow of the exhaust gas 34 through the HRSG 32. For example, the high-temperature heat exchanger 206 may be fluidly coupled to the condensate supply line 80 via the recirculation line 214. In particular, the recirculation line 214 may fluidly couple the high-temperature heat exchanger 206 to the condensate supply line 80.

[0067] In such an embodiment, a water turbine 230 (or hydro turbine) may be disposed (external to the HRSG 32) in fluid communication with the recirculation line 214. The water turbine 230 may be a rotary turbine that converts the energy of the high-pressure water flowing through the recirculation line 214 into rotational / electrical energy, and while doing so, the water turbine 230 may advantageously throttle the high-pressure water from the high-temperature heat exchanger 206 (originally supplied by the forward HPECON 48) down to a condensate pressure that safely enters the condensate supply line 80.

[0068] Further, the electrical energy generated by the hydro turbine 230 may be used to power one or more components of the CCPP 10. For example, the hydro turbine 230 may recover at least a portion of the parasitic losses incurred by the feedwater pump 45. In some embodiments, the electrical energy generated by the hydro turbine 230 may be stored in a battery, which is then used to power one or more components of the CCPP 10. For example, as shown by the dotted line in FIG. 4 , the hydro turbine 230 may be electrically coupled to one or more electrical components 235 (such as a battery or other energy storage, a power converter, the HRSG 32 or another component within the CCPP 10, or other electrical components). In this manner, the electrical power generated by the hydro turbine 230 may be delivered as a power output to the one or more electrical components 235. It should be understood that in some embodiments, the hydro turbine 230 may be disposed in the second pump supply line 212, as described above with reference to FIGS. 1 and 2 . In such an embodiment, the water exiting the water turbine 230 may join the first pump supply line 211 and the second pump supply inlet may be omitted.

[0069] 5 , the fuel heating system 200 may include a high-temperature heat exchanger 306 disposed in fluid communication with a dedicated loop 308. In particular, the high-temperature heat exchanger 306 may be disposed in thermal communication with the fuel supply line 202 and the dedicated loop 308, a portion of which is external to the HRSG 32. The dedicated loop 308 may extend at least partially through the HRSG 32 and may have a dedicated heat exchanger 314 disposed within the HRSG 32. In many embodiments, the dedicated loop 308 may be collectively formed by one or more fluid conduits extending from an outlet of the high-temperature heat exchanger 306 to an inlet of the high-temperature heat exchanger 306. For example, in such embodiments, the dedicated loop 308 may be fluidly isolated from various components of the HRSG 32 (e.g., not in fluid communication with the water / steam circulating through the various HRSG 32 components). In this manner, the dedicated loop 308 may circulate a thermal fluid other than water (i.e., a thermal fluid different from water). In an exemplary embodiment, the thermal fluid in the dedicated loop 308 may be a synthetic organic thermal fluid (e.g., synthetic oil). In particular, the thermal fluid in the dedicated loop may be one of DowTherm™ heat transfer fluids from Dow Chemical Company or Therminol® fluids from Eastman Chemical Company of Kingsport, Tennessee.

[0070] As shown in FIG. 5 , the dedicated loop 308 may include an expansion tank 310, a recirculation pump 312, and a dedicated heat exchanger 314. In an exemplary embodiment, the expansion tank 310, the recirculation pump 312, and the dedicated heat exchanger 314 may each be in fluid communication with the dedicated loop 308, such that thermal fluid passes through each component of the dedicated loop 308. The expansion tank 310 and the recirculation pump 312 may be located external to the HRSG 32 (so that these components are not exposed to the hot exhaust gases flowing through the HRSG 32). The expansion tank 310 may be a container, reservoir, or vessel used to protect the dedicated loop 308 from overpressure. For example, in some embodiments, the expansion tank 310 may be at least partially filled with air to absorb some of the shock caused by overpressure due to thermal expansion of the thermal fluid in the dedicated loop 308 (e.g., due to the compressibility of air).

[0071] A dedicated heat exchanger 314 may be disposed within the HRSG 32 such that the exhaust gases 34 flowing through the HRSG 32 transfer thermal energy to a thermal fluid in a dedicated loop 308 for use in the high temperature heat exchanger 306. In many embodiments, the dedicated heat exchanger 314 may extend within the HRSG 32 from the outlet 33 of the HRSG 32 to upstream of the forward high pressure economizer 48 relative to the flow of exhaust gases through the HRSG 32.

[0072] 6 , the fuel heating system 200 may include a high-temperature heat exchanger 406 disposed in thermal communication with the fuel supply line 202. In such an embodiment, the high-temperature heat exchanger 406 may exchange heat between a portion of the exhaust gas 34 extracted from the HRSG 32 and the fuel flowing through the fuel supply line 202. For example, the CCPP 10 may further include an exhaust extraction system 400 that removes a portion of the exhaust gas 34 from the HRSG 32 for use in heating one or more components (e.g., the high-temperature heat exchanger 406) external to the HRSG 32. The exhaust extraction system 400 may thermally couple the HRSG 32 to the high-temperature heat exchanger 406.

[0073] In the exemplary embodiment, the exhaust gas extraction system 400 may include an exhaust gas extraction duct 408 extending from within the HRSG 32 to the exterior of the HRSG 32, and an exhaust gas recovery duct 412 extending from the exterior of the HRSG 32 to the interior of the HRSG 32. The exhaust gas extraction duct 408 may extend from the HRSG 32 to the high-temperature heat exchanger 406, fluidly coupling them. In particular, as shown in FIG. 6 , the exhaust gas extraction duct 408 may extend from an inlet 410 within the HRSG 32 to the high-temperature heat exchanger 406. The inlet 410 may be positioned upstream of the forward high-pressure economizer 48 with respect to the flow of exhaust gas through the HRSG 32. Furthermore, the exhaust gas recovery duct 412 may extend from the high-temperature heat exchanger 406 to an outlet 414 within the HRSG 32. The outlet 414 may be located within the HRSG 32 immediately downstream of the LPECON 40 (and / or immediately upstream of the outlet 33 of the HRSG 32) relative to the flow of exhaust gases through the HRSG 32. Alternatively, the outlet 414 may be defined within or directly coupled to the exhaust stack 105 without being routed through the HRSG 32. Additionally, in other embodiments, the outlet 414 may be located within the HRSG 32 upstream of the LPECON 40.

[0074] In various embodiments, a fan 411 may be disposed in the exhaust recovery duct 412 and may function to draw a portion of the exhaust gases 34 from the HRSG 32 toward the high-temperature heat exchanger 406. In an exemplary embodiment, the fan 411 may be disposed downstream (e.g., immediately downstream) of the high-temperature heat exchanger 406, relative to the flow of the exhaust gases 34 through the exhaust recovery duct 412. The fan 411 may function to create a pressure differential within the exhaust extraction system 400, thereby moving the exhaust gases from the inlet 410, through the exhaust extraction duct 408 and the exhaust recovery duct 412, and to the outlet 414.

[0075] The CCPP 10 described above with reference to Figures 1, 2, and 4-6, and the feedwater pump control system 600 described above with reference to Figure 3, can each achieve a fuel temperature of greater than about 480°F (about 250°C) at the inlet to the combustion section 18 with less pumping power than conventional designs. For example, recovering water from the high-temperature heat exchanger 206 to the feedwater pump 45 can advantageously reduce the overall parasitic pumping losses incurred in the CCPP 10 system while maintaining the desired fuel temperature at the inlet to the combustion section 18.

[0076] 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 related methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they contain structural elements that do not differ from the literal language of the claims, or if they contain equivalent structural elements that do not have insubstantial differences from the literal language of the claims.

[0077] Further aspects of the present invention are provided by the subject matter of the following clauses.

[0078] 1. A combined cycle power plant (CCPP) comprising: a gas turbine having a compressor section, a combustion section, and a turbine section; a heat recovery steam generator (HRSG) having a first economizer, the HRSG receiving a flow of exhaust gas from the turbine section; a fuel heating system including a fuel supply line and a high-temperature heat exchanger disposed in thermal communication with the fuel supply line, the fuel supply line fluidly coupled to the combustion section and the high-temperature heat exchanger fluidly coupled to the first economizer such that the high-temperature heat exchanger receives water from the first economizer; and a feedwater pump fluidly coupled to the high-temperature heat exchanger.

[0079] The CCPP of any one or more of these clauses, further comprising at least one of an evaporator or a deaerator, wherein the feedwater pump is fluidly coupled to one of the first economizer, the evaporator, or the deaerator.

[0080] The CCPP according to one or more of these clauses, wherein the feedwater pump is a multi-stage pump.

[0081] The CCPP described in one or more of these clauses, wherein the fuel heating system further comprises a low-temperature heat exchanger disposed in thermal communication with the fuel supply line, upstream of the high-temperature heat exchanger with respect to the flow of fuel through the fuel supply line.

[0082] The CCPP of any one or more of these clauses, further comprising a steam turbine system fluidly coupled to a second economizer in the HRSG at least in part via a condensate supply line.

[0083] 10. The CCPP of claim 9, wherein the first economizer is a high-pressure economizer and the second economizer is a low-pressure economizer upstream of the high-pressure economizer relative to the flow of the exhaust gas through the HRSG, a high-temperature input line fluidly coupling the high-pressure economizer to the high-temperature heat exchanger, and a low-temperature input line fluidly coupling the low-pressure economizer to the low-temperature heat exchanger.

[0084] The CCPP of any one or more of these clauses, wherein a low temperature output line fluidly couples the low temperature heat exchanger to the condensate supply line.

[0085] The CCPP of any one or more of these clauses, wherein a low temperature bypass line fluidly couples the low temperature input line to the condensate supply line.

[0086] The CCPP of any one or more of these clauses, wherein a cryogenic pump is disposed in fluid communication with the cryogenic input line.

[0087] 10. The CCPP of claim 9, wherein the low-pressure economizer is fluidly coupled to the feedwater pump via a first pump supply line and the high-temperature heat exchanger is fluidly coupled to the feedwater pump via a second pump supply line.

[0088] The CCPP of any one or more of these clauses, wherein a bridge line fluidly couples the first pump supply line to the condensate supply line, and wherein a bridge pump and a bridge valve are disposed in fluid communication with the bridge line.

[0089] 1. A combined cycle power plant (CCPP) comprising: a gas turbine having a compressor section, a combustion section, and a turbine section; a heat recovery steam generator (HRSG) receiving an exhaust gas flow from the turbine section, the HRSG having a high-pressure economizer and a low-pressure economizer; a fuel heating system including a fuel supply line, a high-temperature heat exchanger, and a low-temperature heat exchanger, wherein the fuel supply line is fluidly coupled to the combustion section, the high-temperature heat exchanger, and the low-temperature heat exchanger disposed in thermal communication with the fuel supply line, the high-temperature heat exchanger being fluidly coupled to the high-pressure economizer, and the low-temperature heat exchanger being fluidly coupled to the low-pressure economizer; and a feedwater pump fluidly coupled to the high-temperature heat exchanger.

[0090] The CCPP according to one or more of these clauses, wherein the feedwater pump is a multi-stage pump.

[0091] 10. The CCPP of claim 9, wherein the low-temperature heat exchanger is disposed in the fuel supply line upstream of the high-temperature heat exchanger relative to the flow of fuel through the fuel supply line.

[0092] The CCPP of any one or more of these clauses, further comprising a steam turbine system fluidly coupled to the low-pressure economizer at least in part via a condensate supply line.

[0093] 10. The CCPP of claim 9, wherein the low-pressure economizer is downstream of the high-pressure economizer relative to the flow of the exhaust gas through the HRSG, a high-temperature input line fluidly coupling the high-pressure economizer to the high-temperature heat exchanger, and a low-temperature input line fluidly coupling the low-pressure economizer to the low-temperature heat exchanger.

[0094] The CCPP of any one or more of these clauses, wherein a low temperature output line fluidly couples the low temperature heat exchanger to the condensate supply line.

[0095] 10. The CCPP of claim 9, wherein the low-pressure economizer is fluidly coupled to the feedwater pump via a first pump supply line and the high-temperature heat exchanger is fluidly coupled to the feedwater pump via a second pump supply line.

[0096] The CCPP of any one or more of these clauses, wherein a bridge line fluidly couples the first pump supply line to a condensate supply line, and wherein a bridge pump and a bridge valve are disposed in fluid communication with the bridge line.

[0097] a heat recovery steam generator (HRSG) having a low-pressure economizer and at least one high-pressure economizer; a fuel heating system having a fuel supply line fluidly coupled to a combustion section, a high-temperature heat exchanger and a low-temperature heat exchanger disposed in thermal communication with the fuel supply line; a feedwater pump having a plurality of stages; a first pump supply line extending between one of the low-pressure economizer, low-pressure steam drum, or deaerator and a first of the plurality of stages; a second pump supply line extending between the high-temperature heat exchanger and an intermediate stage of the plurality of stages; a feedwater supply line extending between a last of the plurality of stages and the at least one high-pressure economizer; and one or more sensors disposed in one or more of the first pump supply line, the second pump supply line, and the feedwater supply line, which sensors receive data indicative of at least one of a water pressure, a water temperature, or a water flow rate. a controller communicatively coupled to the sensor and operably coupled to the valve, the controller including a memory and one or more processors, the memory including memory storing instructions that, when executed by the one or more processors, cause the feedwater pump control system to perform operations including monitoring, via the one or more sensors, data indicative of a temperature difference between water entering the feedwater pump and water exiting the feedwater pump, determining when the temperature difference exceeds a predetermined temperature range, and activating the one or more valves to adjust the flow of water to the feedwater pump to correct the temperature difference to be within the predetermined temperature range. [Explanation of symbols]

[0098] 10 Combined Cycle Power Plant (CCPP) 12 Gas turbine 14 First Load 16 Turbine Section 18 Combustion Section 20 Compressor Section 21 Shaft 22 Steam Turbine System 23 Shaft 24 Second Load 26 Low-pressure (LP) steam turbine 28 Intermediate Pressure (IP) Steam Turbine 30 High Pressure (HP) Steam Turbine 31 Entrance 32 Heat Recovery Steam Generator (HRSG) 33 Exit 34 Exhaust gas 36 Condenser 38 Condensate pump 40 Low-pressure economizer (LPECON) 41 Deaerator 42 Low-pressure evaporator (LPEVAP) 44 Intermediate pressure economizer (IPECON) 45 Water Pump 46 Medium Pressure Evaporator (IPEVAP) 48 Forward High Pressure Economizer (HPECON) 49 Rear High Pressure Economizer (HPECON) 50 High-Pressure Evaporator (HPEVAP) 52 Primary high pressure superheater 54 Finishing high pressure superheater 56 Interstage overheating prevention device 58 Primary reheater 60 Finishing Reheater 62 Interstage overheating prevention device 70 Medium pressure superheater 80 Condensate supply line 105 exhaust stack 106 Controller 114 processors 116 Memory Devices 118 Exit Line 119 Communication Module 124 Exit Line 126 First Water Supply Line 128 Second Water Supply Line 130 Low pressure superheater 132 connection lines 134 Exit Line 150 valves 160 First desuperheater cooling line 162 Second desuperheater cooling line 200 Fuel Heating System 202 Fuel supply line 204 Fuel supply 206 High temperature heat exchanger, high temperature fuel heating heat exchanger, high temperature fuel heater 208 Low temperature heat exchanger, low temperature fuel heating heat exchanger 210 High temperature input line 211 first pump supply line, fluid conduit 212 second pump supply line, fluid conduit 214 Recirculation Line 216 Low temperature input line 218 Low Temperature Output Line 220 Low-temperature bypass line 222 Cryogenic Pump 224 Bridge Line 226 Bridge Pump 228 Bridge Valve 230 Hydro turbine 235 Electrical Components 306 High temperature heat exchanger 308 dedicated loop 310 Expansion Tank 312 Recirculation Pump 314 Dedicated Heat Exchanger 400 Exhaust Extraction System 406 High temperature heat exchanger 408 Exhaust Extraction Duct 410 Entrance 411 Fan 412 Exhaust gas recovery duct 414 Exit 600 Water Supply Pump Control System 602 Multiple columns 604 First Dan 606 Middle and rear stages 608 Final Stage 610 Motor 612 Shaft 614 Sensors

Claims

1. a gas turbine (12) having a compressor section (20), a combustion section (18), and a turbine section (16); a heat recovery steam generator (HRSG) (32) having a first economizer (48), the HRSG (32) receiving the flow of exhaust gases (34) from the turbine section (16); a fuel heating system (200) including a fuel supply line (202) and a high-temperature heat exchanger (206) disposed in thermal communication with the fuel supply line (202), the fuel supply line (202) being fluidly coupled to the combustion section (18) and the high-temperature heat exchanger (206) being fluidly coupled to the first economizer (48) such that the high-temperature heat exchanger (206) receives water from the first economizer (48); a feedwater pump (45) fluidly coupled to the high temperature heat exchanger (206); Equipped with Combined cycle power plant (CCPP) (10).

2. 2. The CCPP (10) of claim 1, further comprising at least one of an evaporator (42, 46, 50) or a deaerator (41), wherein the feedwater pump (45) is fluidly coupled to one of the first economizer (48), the evaporator (42, 46, 50), or the deaerator (41).

3. The CCPP (10) of claim 2, wherein the feedwater pump (45) is a multi-stage pump.

4. 2. The CCPP of claim 1, wherein the fuel heating system further comprises a low-temperature heat exchanger disposed in thermal communication with the fuel supply line upstream of the high-temperature heat exchanger relative to the flow of fuel through the fuel supply line.

5. 10. The CCPP (10) of claim 1, further comprising a steam turbine system (22) fluidly coupled to a second economizer (40) in the HRSG (32) at least in part via a condensate supply line (80).

6. 6. The CCPP of claim 5, wherein the first economizer is a high-pressure economizer and the second economizer is a low-pressure economizer downstream of the high-pressure economizer with respect to the flow of the exhaust gas through the HRSG, a high-temperature input line fluidly coupling the high-pressure economizer to the high-temperature heat exchanger, and a low-temperature input line fluidly coupling the low-pressure economizer to the low-temperature heat exchanger.

7. The CCPP (10) of claim 6, wherein a low temperature output line (218) fluidly couples the low temperature heat exchanger (208) to the condensate supply line (80).

8. The CCPP (10) of claim 6, wherein a low temperature bypass line (220) fluidly couples the low temperature input line (216) to the condensate supply line (80).

9. The CCPP (10) of claim 6, wherein a cryogenic pump (222) is disposed in fluid communication with the cryogenic input line (216).

10. 7. The CCPP (10) of claim 6, wherein the low-pressure economizer (40) is fluidly coupled to the feedwater pump (45) via a first pump supply line (211) and the high-temperature heat exchanger (206) is fluidly coupled to the feedwater pump (45) via a second pump supply line (212).

11. 11. The CCPP of claim 10, wherein a bridge line fluidly couples the first pump supply line to the condensate supply line, and a bridge pump and a bridge valve are disposed in fluid communication with the bridge line.

12. a gas turbine (12) having a compressor section (20), a combustion section (18), and a turbine section (16); a heat recovery steam generator (HRSG) (32) receiving the flow of exhaust gas (34) from the turbine section (16), the HRSG (32) having a high-pressure economizer (48, 49) and a low-pressure economizer (40); a fuel heating system (200) including a fuel supply line (202), a high-temperature heat exchanger (206), and a low-temperature heat exchanger (208), wherein the fuel supply line (202) is fluidly coupled to the combustion section (18), the high-temperature heat exchanger (206), and the low-temperature heat exchanger (208) disposed in thermal communication with the fuel supply line (202), the high-temperature heat exchanger (206) is fluidly coupled to the high-pressure economizer (48), and the low-temperature heat exchanger (208) is fluidly coupled to the low-pressure economizer (40); a feedwater pump (45) fluidly coupled to said high temperature heat exchanger (206); A combined cycle power plant (CCPP) (10) comprising:

13. The CCPP (10) of claim 12, wherein the feedwater pump (45) is a multi-stage pump.

14. 13. The CCPP of claim 12, wherein the low-temperature heat exchanger is disposed in the fuel supply line upstream of the high-temperature heat exchanger relative to the flow of fuel through the fuel supply line.

15. The CCPP (10) of claim 12, further comprising a steam turbine system (22) fluidly coupled to the low-pressure economizer (40) at least in part via a condensate supply line (80).

16. 16. The CCPP (10) of claim 15, wherein the low-pressure economizer (40) is downstream of the high-pressure economizer (48) relative to the flow of the exhaust gas (34) through the HRSG (32), a high-temperature input line (210) fluidly couples the high-pressure economizer (48) to the high-temperature heat exchanger (206), and a low-temperature input line (216) fluidly couples the low-pressure economizer (40) to the low-temperature heat exchanger (208).

17. The CCPP (10) of claim 15, wherein a low temperature output line (218) fluidly couples the low temperature heat exchanger (208) to the condensate supply line (80).

18. 13. The CCPP (10) of claim 12, wherein the low-pressure economizer (40) is fluidly coupled to the feedwater pump (45) via a first pump supply line (211) and the high-temperature heat exchanger (206) is fluidly coupled to the feedwater pump (45) via a second pump supply line (212).

19. 20. The CCPP of claim 18, wherein a bridge line fluidly couples the first pump supply line to a condensate supply line, and a bridge pump and a bridge valve are disposed in fluid communication with the bridge line.

20. A water supply pump control system (600), comprising: a heat recovery steam generator (HRSG) (32) having a low-pressure economizer (40) and at least one high-pressure economizer (48, 49); a fuel heating system (200) having a fuel supply line (202) fluidly coupled to a combustion section (18), a high-temperature heat exchanger (206) and a low-temperature heat exchanger (208) disposed in thermal communication with the fuel supply line (202); a water pump (45) having multiple stages (602); a first pump supply line (211) extending between one of the low-pressure economizer (40), low-pressure steam drum, or deaerator (41) and a first stage (604) of the plurality of stages (602); a second pump supply line (212) extending between the high-temperature heat exchanger (206) and an intermediate stage (606) of the plurality of stages (602); a feedwater supply line (128) extending between a final stage (608) of the plurality of stages (602) and the at least one high-pressure economizer (48, 49); one or more sensors (614) disposed in one or more of the first pump supply line (211), the second pump supply line (212), and the feedwater supply line (128), the sensors (614) configured to provide data indicative of at least one of water pressure, temperature, or flow rate; one or more valves (150) disposed in one or more of the second pump supply line (212) and the feedwater supply line (128); a controller (106) communicatively coupled to the sensor (614) and operably coupled to the valve (150), the controller (106) including a memory (116) and one or more processors (114), the memory (116) when executed by the one or more processors (114) causing the feedwater pump control system (600) to: monitoring, via said one or more sensors (614), data indicative of a temperature difference between the water entering said feedwater pump (45) and the water leaving said feedwater pump (45); determining when the temperature difference exceeds a predetermined temperature range; activating the one or more valves (150) to adjust the flow of water to the feedwater pump (45) to restore the temperature difference to within the predetermined temperature range; a controller (106) including a memory (116) for storing instructions for performing operations, including A water supply pump control system (600) comprising:

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