Combined cycle power plant with steam turbine bypass for simple cycle operation using a heat recovery steam generator and method of use

Abstract

To provide a combined cycle power plant.SOLUTION: A combined cycle power plant (10) with steam turbine bypass for simple cycle operation using a heat recovery steam generator (HRSG, 32) and method of use are disclosed. In the disclosed combined cycle power plant (10), a steam flow valving arrangement (34) is operably coupled with the steam turbine (14), the HRSG (32), and the condenser (30). A steam flow valve device (54) is configured to direct a flow of steam generated in the HRSG (32) to the condenser (30) bypassing the steam turbine (14) during the simple cycle mode of operation. In addition, a steam flow valve device (54) is configured to direct the flow of steam generated in the HRSG (32) to the steam turbine (14) during the combined cycle mode of operation.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] Embodiments of the present disclosure relate generally to combined cycle power plants, and more particularly to a valving arrangement that allows a combined cycle power plant (CCPP) to bypass a steam turbine system and perform simple cycle operation utilizing a gas turbine system and a heat recovery steam generator (HRSG), or to perform combined cycle operation utilizing a gas turbine system and a steam turbine system with an HRSG, while maintaining emissions compliance for both operations. [Background technology]

[0002] Generally, a CCPP includes a gas turbine system and a steam turbine system that work together to generate energy. The gas turbine system combusts a mixture of fuel and airflow and directs the combusted mixture through a turbine to generate power. Exhaust from the gas turbine system can be used in an HRSG to generate steam that is directed to the steam turbine system to generate power. Power plant operators can operate the gas turbine system in a CCPP in simple cycle operation, which uses only the gas turbine system to generate power, or in combined cycle operation, which uses the gas turbine system, HRSG, and steam turbine system to generate power.

[0003] Currently, a diverter damper and bypass stack upstream of the HRSG are required for CCPPs to alternate between simple and combined cycle operating modes. The diverter damper typically includes a single blade that can move to close either the outlet of the damper that directs the exhaust to the bypass stack or the outlet of the damper that directs the exhaust to the HRSG, depending on whether the gas turbine system is operating in simple or combined cycle mode. Generally, bypass stacks used for simple cycle operation are not emissions compliant. Because simple cycle operation is considered temporary due to a steam turbine trip, this operation is typically considered acceptable despite not complying with emissions regulations. To meet the ever-changing demand for electricity on the power grid, more power plant operators want the gas turbine systems in CCPPs to have the flexibility to operate in either simple or combined cycle operating modes and maintain emissions compliance for both modes.

[0004] Currently available technology allows simple cycle operation to be emissions compliant by using a high-temperature selective catalytic reduction (SCR) system with a diverter damper and bypass stack. Using a high-temperature SCR system with a bypass stack has several drawbacks. For example, adding a high-temperature SCR system to a diverter damper and bypass stack is undesirable because its implementation into a gas turbine system is costly due to factors that may include the cost of the high-temperature SCR system itself, the construction cost of implementing the high-temperature SCR system with the diverter damper and bypass stack, and the cost of adding other components to enable the high-temperature SCR system to operate properly. As an example, a large ambient fan is typically added to cool the exhaust from the gas turbine system before it reaches the high-temperature SCR system. To this extent, the fan can prevent unnecessary damage to SCR system components that could result from exhaust temperatures exceeding the SCR system's specified operating temperature limits. Additionally, another drawback of adding a high-temperature SCR system to a diverter damper and bypass stack is that the use of a high-temperature SCR system has a large auxiliary load that reduces the net efficiency of the gas turbine system. Furthermore, deploying high-temperature SCR systems in diverter dampers and bypass stacks significantly increases the overall footprint of the CCPP. Summary of the Invention

[0005] The following presents a simplified summary of the disclosed subject matter in order to provide a basic understanding of some aspects of the various embodiments described herein. This summary is not an extensive overview of the various embodiments. It is not intended to exclusively identify key features or essential features of the claimed subject matter as set forth in the claims, nor is it intended as an aid in determining the scope of the claimed subject matter. Its sole purpose is to present some concepts of the disclosure in a simplified form as a prelude to the more detailed description presented later.

[0006] In light of the drawbacks associated with adding a high temperature SCR system to a diverter damper and bypass stack, another approach is needed that can enable a CCPP to perform simple cycle operation in emissions compliance in addition to having the ability to perform combined cycle operation in emissions compliance.

[0007] Various embodiments provide a solution to the technical problem of enabling a combined cycle power plant to perform both simple and combined cycle operation in emissions compliance, involving the use of a steam flow valve device in the CCPP, the valve device operably coupled to a steam turbine system, a heat pumping generator (HRSG), and a condenser. In one embodiment, during simple cycle operation, the steam flow valve device is configured to direct a flow of steam generated from the HRSG to a condenser, bypassing the steam turbine system. By routing steam from the HRSG around the steam turbine system to the condenser, where condensate from the steam is pumped to the HRSG, water in the heat exchanger tubes of the HRSG is prevented from overheating during simple cycle operation. The steam flow valve is further configured to direct a flow of steam generated in the HRSG to the steam turbine system during combined cycle operation. In each of the steam flow valve device configurations, the HRSG is utilized in both simple and combined cycle operating modes.

[0008] In one embodiment, the steam flow valve device may include a three-way HRSG steam flow valve having an inlet for receiving the steam flow generated from the HRSG, a first outlet for directing the steam flow generated from the HRSG to a condenser, and a second outlet for directing the steam flow generated from the HRSG to a steam turbine system. The opening and closing of the three-way HRSG steam flow valve between the outlets is determined depending on the operating modes of the gas turbine system, the HRSG, and the steam turbine system. For example, in a simple cycle operating mode, the first outlet of the three-way HRSG steam flow valve may be open and the second outlet of the three-way HRSG steam flow valve may be closed, while in a combined cycle operating mode, the first outlet of the three-way HRSG steam flow valve may be closed and the second outlet of the three-way HRSG steam flow valve may be open.

[0009] In one embodiment, the steam flow valve device can include a first isolation HRSG steam flow valve that stops the flow of steam from the HRSG to the steam turbine system and a second isolation HRSG steam flow valve that stops the flow of steam from the HRSG to the condenser. The operation of the first and second isolation HRSG steam flow valves is determined depending on the operating modes of the gas turbine system, the HRSG, and the steam turbine system. For example, in a simple cycle operating mode, the first isolation HRSG steam flow valve can be closed to stop the flow of steam from the HRSG to the steam turbine system and the second isolation HRSG steam flow valve can be opened to allow the flow of steam from the HRSG to the condenser, while in a combined cycle operating mode, the first isolation HRSG steam flow valve can be opened to allow the flow of steam from the HRSG to the steam turbine system and the second isolation valve can be closed to stop the flow of steam from the HRSG to the condenser.

[0010] In one embodiment, the condenser may comprise one or more condensers. For example, the condenser may comprise a single condenser sized to handle the entire steam flow, including the steam flow received from the HRSG in the simple cycle operating mode while the steam turbine system is bypassed and the steam flow from the steam turbine system in the combined cycle operating mode. In another example, the condenser may comprise at least one dedicated steam turbine condenser that receives the steam flow from the steam turbine system in the combined cycle operating mode and one or more additional condensers (i.e., incremental HRSG condensers) that handle incremental steam flow from the HRSG during the simple cycle operating mode.

[0011] In an embodiment in which at least one dedicated steam turbine condenser is used to receive steam flow from the steam turbine system in the combined cycle operating mode and one or more incremental HRSG condensers are used to receive steam flow from the HRSGs during the simple cycle operating mode, a second steam flow valve device can be operably coupled to each of the steam turbine system and the condensers, and the second steam flow valve device can include one of a three-way steam turbine exhaust steam flow valve and an array of isolation steam turbine exhaust flow valves.

[0012] Use of the steam flow valve apparatus of various embodiments eliminates the need for a separate diverter damper and bypass stack typically relied upon to implement a simple cycle operating mode. Furthermore, the steam flow valve apparatus of various embodiments obviates the need to address the aforementioned technical issues by configuring a diverter damper and bypass stack with a high-temperature SCR system to achieve emissions compliance for a gas turbine system for simple cycle operation. By eliminating the need for a separate diverter damper and bypass stack for simple cycle operation, emissions reductions can be managed by the SCR system and stack downstream of the HRSG. To that extent, the SCR system and stack downstream of the HRSG can provide emissions reductions in either gas turbine operating mode, i.e., simple cycle operating mode or combined cycle operating mode. The need to use only one SCR system, typically deployed with an HRSG in a CCPP, to achieve emissions compliance for both simple cycle and combined cycle operation is advantageous over approaches that rely on using a high-temperature SCR system with a diverter damper and bypass stack upstream of the HRSG to achieve emissions compliance in simple cycle mode and require a separate SCR system downstream of the HRSG to provide emissions compliance in combined cycle mode.

[0013] According to one embodiment, a power plant is provided that includes a gas turbine system, a steam turbine system, a heat recovery steam generator (HRSG) that generates steam from an exhaust gas of the gas turbine system, a condenser that condenses steam from one of the steam turbine system and the HRSG, and a first steam flow valve device operably coupled to the steam turbine system, the HRSG, and the condenser, the first steam flow valve device configured to direct a flow of steam generated from the HRSG to the condenser and bypass the steam turbine system during a simple cycle operating mode, and the first steam flow valve device configured to direct a flow of steam generated in the HRSG to the steam turbine system during a combined cycle operating mode.

[0014] According to a second embodiment, a combined cycle power plant is provided. The combined cycle power plant includes a gas turbine system, a steam turbine system, a heat recovery steam generator (HRSG) that generates steam from exhaust gas from the gas turbine system, at least one condenser that condenses steam from one of the steam turbine system and the HRSG, an HRSG steam flow line that supplies steam from the HRSG to the steam turbine system and the at least one condenser, the HRSG steam flow line including a first HRSG steam flow line that supplies steam from the HRSG to the steam turbine system and a second HRSG steam flow line that branches from the first HRSG steam flow line and supplies steam from the HRSG to the at least one condenser, and an HRSG steam flow valve device operably coupled to the HRSG steam flow line, the HRSG steam flow valve device configured to direct a flow of steam generated in the HRSG to the at least one condenser, bypassing the steam turbine system, during a simple cycle operating mode, and the HRSG steam flow valve device configured to direct a flow of steam generated in the HRSG to the steam turbine system during a combined cycle operating mode.

[0015] According to a third embodiment, a method of operating a power plant having a gas turbine system, a steam turbine system, a heat recovery steam generator (HRSG) that generates steam from an exhaust gas of the gas turbine system, and a condenser that condenses the steam is disclosed. The method includes providing a steam flow valve apparatus having at least one valve operably coupled to the steam turbine system, the HRSG, and the condenser, the steam flow valve apparatus being configured to direct a flow of steam generated in the HRSG to the condenser, bypassing the steam turbine system, during a simple cycle operating mode, and the steam flow valve apparatus being configured to direct a flow of steam generated in the HRSG to the steam turbine system during a combined cycle operating mode; specifying a position of the at least one valve in the steam flow valve apparatus to operate in either the simple cycle operating mode or the combined cycle operating mode, the steam flow valve apparatus being configured to completely stop the flow of steam generated in the HRSG from entering the steam turbine system and direct all of the steam flow from the HRSG to the condenser in the simple cycle operating mode, and the steam flow valve apparatus being configured to completely stop the flow of steam generated in the HRSG from going to the condenser and direct all of the steam flow from the HRSG to the steam turbine system in the combined cycle operating mode.

[0016] The technology will be better understood by reading the following description of non-limiting embodiments with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram of a CCPP having a gas turbine system capable of operating in a combined cycle operating mode with an HRSG and steam turbine system, and alternatively operating in a simple cycle operating mode with an HRSG where steam flow from the HRSG to the steam turbine system is bypassed and instead directed to a condenser, with both operating modes maintaining emissions compliance, according to one embodiment of the present disclosure. [Figure 2] 2 is a schematic diagram of a CCPP having a steam flow valve apparatus illustrated in FIG. 1 as a three-way valve according to one embodiment of the present disclosure. [Figure 3] 2 is a schematic diagram of a CCPP having a steam flow valve arrangement illustrated in FIG. 1 as an array of isolation valves, according to one embodiment of the present disclosure. [Figure 4] 1 is a schematic diagram of a CCPP having two or more condensers, a steam flow valve apparatus configured as a three-way valve, and a steam turbine flow valve apparatus configured as a three-way valve that supplies exhaust steam from a steam turbine system to the condensers, according to one embodiment of the present disclosure. [Figure 5] FIG. 5 is a schematic diagram of a CCPP similar to that illustrated in FIG. 4 having an array of isolation valves configured for use as a steam flow valve arrangement and a steam turbine flow valve arrangement, according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0018] Exemplary embodiments of the present disclosure are described more fully below with reference to the accompanying drawings, in which some, but not all, embodiments are shown. Indeed, the present technology may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. To facilitate understanding, like reference numerals may refer to like elements throughout.

[0019] Throughout the following description, it may be necessary to use specific descriptive terminology when referring to and describing the gas turbine system, steam turbine system, and / or associated mechanical components within a combined CCPP. When doing so, common industry terminology is used and employed, whenever possible, in a manner consistent with its accepted meaning. Unless otherwise noted, such terminology should be given a broad interpretation consistent with the context of this application and the appended claims. Those skilled in the art will understand that in many cases, a particular component may be referred to using several different or overlapping terms. What may be described herein as being a single component may include, and be referred to in other contexts as consisting of multiple components. Alternatively, what may be described herein as comprising multiple components may be referred to elsewhere as a single component.

[0020] Additionally, certain descriptive terms may be used regularly herein. These terms and their definitions are as follows, unless otherwise specified. For example, as used herein, "downstream" and "upstream" are terms that indicate a direction relative to the flow of a fluid, such as steam through a fluid flow line, piping, conduit, etc., or the flow of air through, for example, a combustor, or a coolant through one of the component systems of a turbine. For example, the term "downstream" corresponds to the direction of fluid flow, and the term "upstream" refers to the opposite direction of the flow.

[0021] As described above, the present disclosure provides a steam flow valve arrangement that enables a gas turbine system in a CCPP to perform simple cycle operation with an HRSG by bypassing the steam turbine system, such that steam generated in the HRSG flows directly to a condenser, from which condensate from the steam is pumped to the HRSG. In addition, the steam flow valve arrangement enables the gas turbine system to perform combined cycle operation, where steam generated in the HRSG flows to the steam turbine system to generate power and a condenser pumps condensate from the steam to the HRSG. Both simple cycle operation and combined cycle operation can be performed using a steam flow valve arrangement according to any of the various embodiments, and in particular, emissions compliance can be achieved for both operations.

[0022] Referring now to the figures, Figure 1 illustrates a schematic diagram of a CCPP 10 according to one embodiment of the present disclosure. As shown in Figure 1, the CCPP 10 may include a gas turbine system 12 and a steam turbine system 14 fluidly coupled to the gas turbine system 12.

[0023] The gas turbine system 12 includes a compressor 16 and a combustor 18. The gas turbine system 12 may also include a gas turbine 20 (i.e., an expansion turbine) coupled to a common compressor / turbine shaft 22. In one embodiment, the gas turbine system 12 is a 7HA engine commercially available from GE Vernova, Greenville, SC. ​​Embodiments of the present disclosure are not limited to any one particular gas turbine system or gas turbine manufacturer and may be implemented in connection with other engines, including, for example, GE Vernova's 7EA, 7FA, 9FA, or 9HA engine models. During operation, air entering the inlet of the compressor 16 is compressed and then discharged to the combustor 18, where a fuel, such as a gas, e.g., natural gas, or a fluid, e.g., oil, is combusted to provide high-energy combustion gases that drive the gas turbine 20. In the gas turbine 20, energy in the hot gases is converted to work, a portion of which is used to drive the compressor 16 by rotating the shaft 22.

[0024] The steam turbine system 14 may include one or more steam turbine sections or segments 24. While not shown in FIG. 1 or any of the other figures of this disclosure, the steam turbine system 14 may include a high-pressure (HP) section, an intermediate-pressure (IP) section, and a low-pressure (LP) section. Each of the steam turbine sections 24 of the steam turbine system 14 may include a plurality of rotating blades (not shown) mechanically coupled to a shaft 26, which rotates the shaft based on steam flow passing therethrough. For example, a steam cycle circuit may direct steam flow to enter the inlets of the HP section, the IP section, and / or the LP section. The steam is routed to the inlets and imparts force against the blades to rotate the shaft 26. In this manner, steam formed in an upstream steam turbine section may be subsequently used in a downstream steam turbine section. To this extent, the steam drives at least a portion of the steam turbine system 14, where work is extracted to drive the shaft 26.

[0025] The shaft 26 of the steam turbine system may be coupled to the shaft 22 of the gas turbine system 12 to form a common shaft that drives a load, such as a generator 28, to generate electricity. For example, the generator 28 may generate electricity based on common shaft work converted from the thermal energy of the hot gases in the gas turbine 20 in simple cycle operation, or common shaft work converted from both the energy of the hot gases in the gas turbine 20 and the compressed steam in the steam turbine section 24 in combined cycle operation.

[0026] 1 represents only one possible implementation, as one skilled in the art will appreciate that other design options are possible. For example, a generator can optionally be located between gas turbine system 12 and steam turbine system 14. In this configuration, steam turbine system 14 can be isolated via a clutch.

[0027] The condenser 30 may be operably coupled to an appropriate steam turbine section 24 of the steam turbine system 12. For example, the condenser 30 may be in fluid communication with an aftmost steam turbine section, such as the LP section. Generally, the condenser 30 may cool exhaust steam from the steam turbine section 24, collect the latent heat of the steam, and condense the steam into water.

[0028] The CCPP 10 may also include a steam generation source, such as an HRSG 32, operably connected to the gas turbine system 12 and the steam turbine system 14. As will be appreciated, the exhaust from the gas turbine system 12 may be used by the HRSG 32 to generate a steam flow for use by the steam turbine system 14. The HRSG 32 may include a conventional or once-through HRSG configuration, such as those used in conventional combined cycle power systems, and / or may be embodied as another type of heat exchanger or similar component for generating steam using exhaust energy. For example, the HRSG 32 may include heat transfer tubes, pipes, lines, etc. having water therein, such that the water in the HRSG 32 is indirectly heated by the exhaust from the gas turbine system 14 to generate the steam flow. The HRSG 32 may be fluidly connected to the gas turbine system 12, the steam turbine system 14, and the condenser 30 via fluid flow lines, piping, conduits, etc., and various fluid flow control devices that may control, regulate, or redirect the flow of fluid through the lines. Further details of some of the fluid flow lines and fluid flow control devices that can control, regulate, or redirect fluid flow between the steam turbine system 14, the condenser 30, and the HRSG 32 are described in more detail below.

[0029] 1 , a steam flow valve apparatus 34 may be operatively coupled to the steam turbine system 14, the HRSG 32, and the condenser 30. In one embodiment, the steam flow valve apparatus 34 is configured to direct the flow of steam generated from the HRSG 32 along an HRSG steam flow line 36 to supply the steam from the HRSG to the steam turbine system 14 and the condenser 30. The HRSG steam flow line 36 may include a first HRSG steam flow line that supplies steam from the HRSG 32 to the steam turbine system 14 and a second HRSG steam flow line that branches off from the first HRSG steam flow line at a junction of the two lines that supplies steam from the HRSG to the condenser 30.

[0030] In one embodiment, the steam flow valve arrangement 34 may be configured to direct the flow of steam generated from the HRSG 32 to the condenser 30 and bypass the steam turbine system 14 during a simple cycle operating mode. In a combined cycle operating mode, the steam flow valve arrangement 34 may be configured to direct the flow of steam generated in the HRSG 32 to the steam turbine system 14 via one of the HRSG steam flow lines 36 dedicated to supplying steam flow from the HRSG to the steam turbine.

[0031] Because the steam flow valve device 34 directs steam from the HRSG 32 to bypass the steam turbine system 14 and supply to the condenser 30 in a simple cycle operating mode, it is understood that the steam flow bypass can include a full or partial bypass of the steam turbine. In a full bypass of the steam turbine system 14, the steam flow valve device 34 can completely stop the flow of steam generated in the HRSG 32 from entering the steam turbine and can direct all of the steam flow from the HRSG to the condenser 30. In a partial bypass of the steam turbine system 14, the steam flow valve device 34 can allow a first partial steam flow generated in the HRSG 32 to enter the steam turbine system 14 and a second partial steam flow generated in the HRSG 32 to enter the condenser 30. This capability is advantageous because it allows greater flexibility in the total plant power output that can be achieved for the CCPP 10, since it can accommodate steam turbine part-load operation as an intermediate point between the full combined cycle and full simple cycle operating modes.

[0032] Similarly, instead of the steam flow valve arrangement 34 directing all of the steam flow from the HRSG 32 to the steam turbine system 14 without diverting it to the condenser 30, the steam flow valve arrangement 34 in the combined cycle operating mode may allow a partial steam flow generated in the HRSG 32 to flow toward the condenser 30, so that there is some diverting of steam to the condenser 30. As noted above, this capability is also advantageous because it allows for greater flexibility in total plant output, since it can accommodate steam turbine part load operation as an intermediate point between the full combined cycle and full simple cycle operating modes.

[0033] To this extent, the steam flow valve arrangement 34 can be utilized as part of a method for operating a CCPP having a gas turbine system, a steam turbine system, an HRSG that generates steam from the exhaust of the gas turbine system, and a condenser that condenses steam from one of the steam turbine system and the HRSG. For example, the position of at least one valve in the steam flow valve arrangement can be designated to operate in a simple cycle operating mode or a combined cycle operating mode. For example, the position of the at least one valve can be set to completely stop the flow of steam generated in the HRSG from entering the steam turbine system and to direct all of the steam flow from the HRSG to the condenser in the simple cycle operating mode. The position of the at least one valve can also be set to completely stop the flow of steam generated in the HRSG from proceeding to the condenser and to direct all of the steam flow from the HRSG to the steam turbine system in the combined cycle operating mode. In one embodiment, the position of at least one valve can be set to allow partial steam flow from the HRSG to the condenser and steam turbine when the method of operating the power plant transitions between a full combined cycle operating mode (wherein the entire steam flow generated in the HRSG is directed to the steam turbine system without being diverted to the condenser) and a full simple cycle operating mode (wherein the entire steam flow generated from the HRSG is directed to the condenser completely bypassing the steam turbine system).

[0034] In one embodiment, the condenser 30 may receive steam from either the steam exhaust of the steam turbine system 14 or steam generated by the HRSG 32. In this manner, the condenser 30 may cool the steam from the steam turbine system 14 or the HRSG 32, capture the latent heat of the steam, and condense the steam into water. As shown in FIG. 1 , a condensate pump 38 may pressurize condensed water discharged from the condenser 30 into condensate piping 40 to supply back to the HRSG 32 as feedwater.

[0035] In one embodiment shown in FIG. 1, the flow of flue gas 42 from the HRSG 36 is NO xThis can lead to an emissions control device such as an SCR system 44 to reduce NO emissions (e.g., nitric oxide (NO), nitrogen dioxide (NO), and other nitrogen oxides). Typically, an SCR system 44 reduces NO emissions by injecting ammonia (NH) into the flue gas upstream of a catalyst. x In this respect, the NO 2 in the flue gas 42 can be reduced. x The SCR system 44 is stacked through NO x The reduced flue gas 46 may be reduced to water and nitrogen so that it can be released into the atmosphere.

[0036] Although the emissions control devices of various embodiments are described as SCR systems, it will be understood that the embodiments are suitable for use with any now known or later developed emissions control device.

[0037] In any event, the configuration illustrated in FIG. 1 allows various embodiments to eliminate the need for a separate diverter damper and bypass stack typically relied upon to implement a simple-cycle operating mode implemented upstream of the HRSG 32. Furthermore, the steam flow valve apparatus 34 of various embodiments obviates the need to address the aforementioned technical issues by configuring a diverter damper and bypass stack with a high-temperature SCR system to bring the gas turbine system into emissions compliance for simple-cycle operation. By eliminating the need for a separate diverter damper and bypass stack for simple-cycle operation, emission reductions can be managed by the SCR system 44 and stack downstream of the HRSG 32. To this extent, the SCR system 44 and stack downstream of the HRSG 32 can provide emission reductions in both modes of turbine operation, i.e., simple-cycle and combined-cycle operating modes.

[0038] The need to use only one SCR system, typically deployed with the HRSG in a CCPP, to achieve emissions compliance for both simple and combined cycle operation is advantageous over approaches that rely on using a high-temperature SCR system with a diverter damper and bypass stack upstream of the HRSG to achieve emissions compliance in simple cycle mode and another SCR system downstream of the HRSG to provide emissions compliance in combined cycle mode, resulting in significant savings in capital investment and operation and maintenance costs over the life of the CCPP.

[0039] It will be understood that for clarity in describing various embodiments of the present disclosure, only certain aspects of the CCPP 10 are shown and described in detail, such as the gas turbine system 12, the steam turbine system 14, the HRSG 32, the condenser 30, and the steam flow valving arrangement 34. Those skilled in the art will appreciate that the CCPP 10, including the gas turbine system 12, the steam turbine system 14, the HRSG 32, the condenser 30, and the steam flow valving arrangement 34, can include additional components that enable the plant to operate in emissions compliance in both simple and combined cycle modes of operation.

[0040] For example, it is understood that a desuperheater is deployed to attenuate the superheated steam generated by the HRSG 32. Generally, the superheated steam generated in the HRSG 32 is at a temperature higher than the saturation temperature for the steam pressure. This excess heat results in steam that is higher than the saturation temperature, contains more energy than saturated steam, and has a larger specific volume than saturated steam. Desuperheaters (also called attemperators) are deployed to operate in conjunction with the superheaters and reheaters to control the temperature of the steam to meet specific steam turbine inlet requirements in the steam turbine system 14 and prevent thermal damage to the superheater and reheater tubes, which may form part of the HRSG design. In this manner, the desuperheater can return the superheated steam to its saturated state or reduce the temperature of the superheated steam. For example, when the desuperheater is operating, a measured amount of water is added to the superheated steam via a mixing device within the desuperheater. Upon entering the desuperheater, the cooling water evaporates by absorbing heat from the superheated steam. As a result, the temperature of the steam decreases.

[0041] A deaerator, which can help reduce the gas content in the feedwater supplied from the condenser 30 to the HRSG 32, is another component commonly utilized in the CCPP 10. Generally, a deaerator may include an inventory or storage tank of water obtained from the condensate system via a condensate pump and condensate piping, an auxiliary steam source or other heating source to heat the inventory tank, and a feedwater piping or line that supplies the deaerated, heated feedwater to the HRSG 32. During operation, the deaerator uses steam from the auxiliary steam source to heat the water to a full saturation temperature corresponding to the steam pressure within the deaerator, scrubbing dissolved gases from the feedwater that is to be directed to the HRSG 32. In this way, the deaerator can reduce the concentration of dissolved oxygen and carbon dioxide to a level where the impact of corrosive gases is minimized.

[0042] The desuperheaters and deaerators represent only a few of the components not shown in Figure 1 and other figures of this disclosure. Those skilled in the art will understand that CCPP 10, gas turbine system 12, steam turbine system 14, and HRSG 32 may include several other well-known components that make up the gas turbine system, steam turbine system, and HRSG 32 and enable these elements to operate as part of CCPP 10.

[0043] Additionally, although CCPP 10 is shown in FIG. 1 and other figures as a single-shaft CCPP having a single generator coupled to both the gas turbine system and the steam turbine system via a common shaft, it is understood that other configurations are suitable for use with the embodiments described herein. For example, each of the gas turbine system and the steam turbine system can be mechanically coupled by a shaft to its own corresponding generator to generate electrical energy to achieve a CCPP having a multi-shaft configuration. It is understood that the number of generators and shafts for a CCPP can be of any size or type known in the art and can vary depending on their application or the system to which they are connected.

[0044] 2 shows a schematic diagram of the CCPP 10 illustrated with the steam flow valving apparatus 34, illustrated as a three-way valve 48, in accordance with one embodiment of the present disclosure. In FIG. 2, the three-way valve 48 forms an HRSG steam flow valving apparatus operatively coupled with the HRSG steam flow line 36. In this regard, as described above, the HRSG steam flow valving apparatus formed from the three-way valve 48 is configured to direct the flow of steam generated in the HRSG 32 to the condenser 30, bypassing the steam turbine system 14, during a simple cycle operating mode. Additionally, the HRSG steam flow valving apparatus formed from the three-way valve 48 is configured to direct the flow of steam generated in the HRSG 32 to the steam turbine system 14 during a combined cycle operating mode.

[0045] In one embodiment, the three-way valve 48 may include an inlet for receiving the steam flow generated from the HRSG 32, a flow path, a first outlet for directing the steam flow generated from the HRSG 32 to the condenser 30 through the flow path and the first outlet, and a second outlet for directing the steam flow generated from the HRSG 32 to the steam turbine system 14 through the flow path and the second outlet. The opening and closing of the three-way HRSG steam flow valve 48 is determined depending on the operating modes of the gas turbine system 12, the HRSG 32, and the steam turbine system 14. For example, in a simple cycle operating mode, the first outlet of the three-way HRSG steam flow valve 48 may be open and the second outlet of the three-way HRSG steam flow valve 48 may be closed. In a combined cycle operating mode, the first outlet of the three-way HRSG steam flow valve 48 may be closed and the second outlet of the three-way HRSG steam flow valve 48 may be open. Opening the second outlet of the three-way HRSG steam flow valve 48 and closing the first outlet of the HRSG steam valve 48 bypasses steam flow around the steam turbine system 14 via one of the HRSG steam flow lines 36.

[0046] 3 shows a schematic diagram of the CCPP 10 illustrated with a steam flow valve arrangement 34, which is illustrated as an array of isolation valves 50, according to one embodiment of the present disclosure. In FIG. 3 , the array of isolation valves 50, which may include isolation valves, on-off valves, stop valves, etc., may form the HRSG steam flow valve arrangement 34 operably coupled to the HRSG steam flow line 36. In one embodiment, the array of isolation valves may include a first isolation HRSG steam flow valve 50 (e.g., a valve upstream of the inlet to the steam turbine section 24) operably coupled to the first HRSG steam flow line 36 (e.g., a portion of the flow line that is in fluid communication with the inlet of the steam turbine system 14) to stop the flow of steam from the HRSG 32 to the steam turbine system 14, and a second isolation HRSG steam flow valve 50 (e.g., a valve in the portion of the flow line 36 that branches off from the main line and is in fluid communication with the condenser 30) operably coupled to the second HRSG steam flow line 36 to stop the flow of steam from the HRSG 32 to the condenser 30.

[0047] The operation of the first and second isolation HRSG steam flow valves 50 is determined depending on the operating modes of the gas turbine system 12, the HRSG 32, and the steam turbine system 14. In one embodiment, in a simple cycle operating mode, the first isolation HRSG steam flow valve 50 can be closed to stop the flow of steam from the HRSG 32 to the steam turbine system 14, and the second isolation HRSG steam flow valve 50 can be opened to allow the flow of steam from the HRSG 32 to the condenser 30. In the simple cycle operating mode, the respective positions of the first and second isolation HRSG steam flow valves 50 bypass the steam flow around the steam turbine system 14. In a combined cycle operating mode, the first isolation HRSG steam flow valve 50 can be opened to allow the flow of steam from the HRSG 32 to the steam turbine system 14, and the second isolation valve 50 can be closed to stop the flow of steam from the HRSG 32 to the condenser 30.

[0048] Figure 4 shows a schematic diagram of a CCPP 52 similar to CCPP 10 shown in Figure 2, but CCPP 52 is comprised of two or more condensers 30. Instead of a single condenser sized to handle the entire steam flow, including the steam flow received from HRSG 32 in a simple cycle operating mode while the steam turbine system is bypassed and the steam flow from steam turbine system 14 in a combined cycle operating mode, as shown in Figures 1-3, the embodiment shown in Figures 4 and 5 shows at least one dedicated condenser to handle the steam flow for the combined cycle mode and at least one additional condenser (i.e., an incremental HRSG condenser) to handle incremental steam flow for the simple cycle mode.

[0049] In the multiple condensers 30 illustrated in the embodiments of FIGS. 4 and 5 , the figures focus on a steam turbine exhaust line 54 that can supply exhaust steam from the steam turbine system 14 to the condensers 30 and can receive steam diverted from the HRSG steam flow line 36. As shown in the figures, the steam turbine exhaust line 54 can include a first exhaust steam flow line that supplies exhaust steam from the steam turbine system 14 to at least one dedicated steam turbine condenser 30 (e.g., a portion of the main exhaust line in fluid communication with the condenser 30 on the left side of the figure). In addition, the steam turbine exhaust line 54 can include a second exhaust steam flow line that branches off from the HRSG steam flow line 36 and receives a flow of HRSG steam from the HRSG 32 that is directed toward one or more incremental HRSG condensers 30 (e.g., the condenser on the right side of the figure). To this extent, HRSG steam can be diverted from the HRSG steam flow line 36 to the second exhaust steam flow line during a simple cycle operating mode to supply at least one dedicated steam turbine condenser 30 via a steam turbine flow valve device 60. In this manner, the HRSG steam flow may be directed to at least one dedicated steam turbine condenser in addition to the HRSG steam flow provided to the incremental HRSG condensers via HRSG steam flow line 36 .

[0050] 4 and 5 , a steam turbine flow valve apparatus 60 may be operably coupled to the steam turbine exhaust line 54 to supply exhaust steam from the steam turbine system 14 to the condenser 30. The steam turbine flow valve apparatus 60 may include a three-way steam turbine exhaust steam flow valve 56 ( FIG. 4 ) or an array of isolated steam turbine exhaust flow valves 58 ( FIG. 5 ). To this extent, both the three-way steam turbine exhaust steam flow valve 56 and the array of isolated steam turbine exhaust flow valves 58 may be operably coupled to the first exhaust steam flow line and the second exhaust steam flow line of the steam turbine exhaust line 54.

[0051] 4 illustrates the second steam flow valve apparatus 60 as a three-way steam turbine exhaust flow valve 56. In one embodiment, the three-way steam turbine exhaust flow valve 56 of the second steam flow valve apparatus 60 may include a first inlet that receives exhaust steam from the steam turbine system 14, a second inlet that receives a diverted flow of HRSG steam from the HRSG steam flow line 36 that is directed from the HRSG 32 to the HRSG incremental condenser 30 (i.e., the condenser on the right side of the figure), and an outlet that directs the exhaust steam flow from the steam turbine system 14 or the diverted flow of HRSG steam to at least one dedicated steam turbine condenser 30 (i.e., the condenser on the left side of the figure) during a simple cycle operating mode.

[0052] 5 illustrates the second steam flow valve apparatus 60 as an array of isolation valves 58. In one embodiment, the array of isolation valves 58 of the second steam flow valve apparatus of this embodiment can include a first isolated steam turbine exhaust flow valve 58 (e.g., a valve in a main portion of a line in fluid communication with the condenser on the left side of the illustration) that stops the flow of exhaust steam from the steam turbine system 14 to at least one dedicated steam turbine condenser 30, and a second isolated steam turbine exhaust flow valve 58 (e.g., a valve in a portion of a line 54 that branches off from the main line and is in fluid communication with the condenser on the right side of the illustration) that stops the flow of exhaust steam from the steam turbine system 14 to one or more incremental HRSG condensers. In one embodiment, during simple cycle mode operation, the second isolated steam turbine exhaust flow valve 58 can be configured to allow a diversion of HRSG steam from the HRSG steam flow line 36 that is directed to the HRSG incremental condenser 30 to also be supplied to the at least one dedicated steam turbine condenser 30.

[0053] It is apparent that in various embodiments described herein, the steam flow valve arrangements 34, 60 enable the gas turbine system 12 in the embodiment CCPPs 10, 52 to operate in both simple and combined cycle operating modes. Furthermore, the embodiments provide a solution to the technical problem of having a CCPP perform both simple and combined cycle operating modes in emissions compliance due to the configuration of the gas turbine system, steam turbine system, HRSG, condenser, and steam flow valve arrangement.

[0054] Additionally, embodiments provide several advantages over current approaches and any modifications to these approaches that can facilitate both modes of operation in emissions compliance. For example, use of the steam flow valve apparatus of various embodiments eliminates the need for separate diverter dampers and bypass stacks typically relied upon to implement a simple cycle mode of operation in a CCPP. Furthermore, the steam flow valve apparatus of various embodiments obviates the need to address the aforementioned technical issues by configuring a diverter damper and bypass stack in a high-temperature SCR system to make the gas turbine system emissions compliant for simple cycle operation. By eliminating the need for a separate diverter damper and bypass stack for simple cycle operation, emission reductions for both operations can be managed by a common (i.e., single) SCR system and stack downstream of the HRSG. To this extent, the SCR system and stack downstream of the HRSG can provide emission reductions in either turbine mode of operation, i.e., both simple cycle and combined cycle modes of operation. The need to use only one SCR system, typically deployed with the HRSG in a CCPP, to obtain emissions compliance for both simple and combined cycle operation is advantageous over approaches that rely on using a high-temperature SCR system with a diverter damper and bypass stack upstream of the HRSG to obtain emissions compliance in simple cycle mode, and require another SCR system in place downstream of the HRSG to provide emissions compliance in combined cycle mode.

[0055] The above description of illustrated embodiments of the subject disclosure, including what is set forth in the Abstract, is not intended to be exhaustive or to limit the disclosed embodiments to the precise forms disclosed. While specific embodiments and examples have been described herein for illustrative purposes, various modifications are possible that are contemplated within the scope of such embodiments and examples, as will be recognized by those skilled in the relevant art. For example, parts, components, steps, and aspects from different embodiments may be combined or adapted for use in other embodiments, even if not described or illustrated in the figures herein. Thus, because certain changes can be made to the above-described systems without departing from the spirit and scope of the improvements contained herein, it is intended that all of the subject matter of the above description, as shown in the accompanying drawings, should be interpreted solely as examples illustrating the inventive concepts herein, and not as limiting the present disclosure.

[0056] In this regard, while the disclosed subject matter has been described in connection with various embodiments and corresponding figures, it should be understood that, where applicable, other similar embodiments can be used, or modifications and additions can be made to the described embodiments, to perform the same, similar, alternative, or substitute functions of the disclosed subject matter without departing from the disclosed subject matter. Accordingly, the disclosed subject matter should not be limited to any single embodiment described herein, but rather should be broadly construed in accordance with the following appended claims. For example, references to "one embodiment" in the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Included within the scope of the present disclosure are the embodiments, examples, and embodiments resulting from combining the features thereof in any order and number as disclosed herein and in the claims.

[0057] In the appended claims, the terms "including" and "in which" are used as the plain English equivalents of the terms "comprising" and "wherein," respectively. Furthermore, in the following claims, the terms "first," "second," "third," "upper," "lower," "bottom," "top," and the like are used merely as guides and are not intended to impose numerical or positional requirements on their objects. The terms "substantially," "generally," and "about" indicate conditions within reasonably achievable manufacturing and assembly tolerances relative to ideal desired conditions suitable for achieving the functional purpose of a component or assembly. Furthermore, the limitations of the following claims are not written in, and are not intended to be construed as, means-plus-function style, unless such claim limitations expressly use the phrase "means for" in combination with a description of function devoid of further structure. Furthermore, the articles "a" and "an" as used in this specification and the accompanying drawings should generally be construed to mean "one or more" unless otherwise specified or unless it is clear from the context that the singular form is intended.

[0058] The foregoing includes examples of systems and methods that illustrate the disclosed subject matter. Of course, it is not possible to describe herein every combination of components or methodologies. Those skilled in the art will recognize that many further combinations and permutations of the claimed subject matter are possible. Furthermore, to the extent that terms such as "includes," "has," and "possesses" are used in the detailed description, claims, appendices, and drawings, such terms are intended to be inclusive in the same manner as "comprising," as the term "comprising" is interpreted when used as a transitional term in the claims. That is, unless expressly stated to the contrary, an embodiment that "comprising," "including," or "having" an element or elements having a particular property may further include such elements that do not have that property.

[0059] Examples are used herein to disclose some embodiments of the invention, including the best mode, and to enable any person skilled in the art to practice the embodiments of 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 that do not differ substantially from the literal language of the claims.

[0060] Further aspects of the present invention are provided by the subject matter of the following clauses.

[0061] 1. A power plant comprising: a gas turbine system; a steam turbine system; a heat recovery steam generator (HRSG) that generates steam from an exhaust gas of the gas turbine system; a condenser that condenses steam from one of the steam turbine system and the HRSG; and a first steam flow valve device operably coupled to the steam turbine system, the HRSG, and the condenser, the first steam flow valve device configured to direct a flow of steam generated from the HRSG to the condenser, bypassing the steam turbine system, during a simple cycle operating mode, and the first steam flow valve device configured to direct the flow of steam generated in the HRSG to the steam turbine system during a combined cycle operating mode.

[0062] 10. The power plant of claim 9, wherein the first steam flow valve device comprises a three-way HRSG steam flow valve having an inlet for receiving the steam flow generated from the HRSG, a first outlet for directing the steam flow generated from the HRSG to the condenser, and a second outlet for directing the steam flow generated from the HRSG to the steam turbine system.

[0063] The power plant of any of the preceding clauses, wherein the opening and closing of the three-way HRSG steam flow valve is determined according to the operating modes of the gas turbine system, the HRSG, and the steam turbine system, and wherein in the simple cycle operating mode, the first outlet of the three-way HRSG steam flow valve is opened and the second outlet of the three-way HRSG steam flow valve is closed, and in the combined cycle operating mode, the first outlet of the three-way HRSG steam flow valve is closed and the second outlet of the three-way HRSG steam flow valve is opened.

[0064] 10. The power plant of claim 9, wherein the first steam flow valve device comprises a first isolation HRSG steam flow valve that stops the flow of the steam from the HRSG to the steam turbine system, and a second isolation HRSG steam flow valve that stops the flow of the steam from the HRSG to the condenser.

[0065] 10. The power plant of claim 9, wherein operation of the first isolation HRSG steam flow valve and the second isolation HRSG steam flow valve is determined according to the operating modes of the gas turbine system, the HRSG, and the steam turbine system, wherein in the simple cycle operating mode, the first isolation HRSG steam flow valve is closed to stop the flow of the steam from the HRSG to the steam turbine system and the second isolation HRSG steam flow valve is opened to allow the flow of the steam from the HRSG to the condenser, and in the combined cycle operating mode, the first isolation HRSG steam flow valve is opened to allow the flow of the steam from the HRSG to the steam turbine system and the second isolation valve is closed to stop the flow of the steam from the HRSG to the condenser.

[0066] 10. The power plant of claim 9, further comprising: a first HRSG steam flow line that supplies the steam from the HRSG to the steam turbine system; and a second HRSG steam flow line that branches off from the first HRSG steam flow line and supplies the steam from the HRSG to the condenser, wherein the first isolation HRSG steam flow valve is operably coupled to the first HRSG steam flow line and the second isolation HRSG steam flow valve is operably coupled to the second HRSG steam flow line.

[0067] 10. The power plant of claim 1, wherein the condenser comprises a single condenser sized to handle all steam flows including steam flows received from the HRSG in the simple cycle operating mode while the steam turbine system is bypassed and steam flows from the steam turbine system in the combined cycle operating mode.

[0068] 10. The power plant of claim 1, wherein the condenser comprises at least one dedicated steam turbine condenser that receives a steam flow from the steam turbine system in the combined cycle operating mode, and one or more incremental HRSG condensers that receive an additional steam flow from the HRSG during the simple cycle operating mode.

[0069] 10. The power plant of claim 9, further comprising: a second steam flow valve device operatively coupled to each of the steam turbine system and the condenser, the second steam flow valve device comprising a three-way steam turbine exhaust flow valve having a first inlet that receives exhaust steam from the steam turbine system, a second inlet that receives a branch flow of HRSG steam from the HRSG that is directed to the one or more HRSG incremental condensers, and an outlet that directs the flow of exhaust steam from the steam turbine system to the at least one dedicated steam turbine condenser or directs the branch flow of HRSG steam to the at least one dedicated steam turbine condenser.

[0070] 10. The power plant of claim 9, further comprising: a second steam flow valve device operatively coupled to each of the steam turbine system and the condenser, the second steam flow valve device comprising: a first isolation steam turbine exhaust flow valve configured to stop the flow of the exhaust steam from the steam turbine system to the at least one dedicated steam turbine condenser; and a second isolation steam turbine exhaust flow valve configured to stop the flow of the exhaust steam from the steam turbine system to the one or more incremental HRSG condensers, the second isolation steam turbine exhaust flow valve further configured to allow a diversion of HRSG steam from the HRSG to the one or more incremental HRSG condensers to be directed to the at least one dedicated steam turbine condenser.

[0071] 10. The power plant of claim 9, further comprising: a first exhaust steam flow line that supplies the exhaust steam from the steam turbine system to the at least one dedicated steam turbine condenser; and a second exhaust steam flow line in fluid communication with the first exhaust steam flow line, branching from an HRSG steam flow line that supplies the HRSG steam flow from the HRSG toward the one or more incremental HRSG condensers and receiving the diverted stream of the HRSG steam for supplying the at least one dedicated steam turbine condenser, wherein the first isolation steam turbine exhaust flow valve is operably coupled to the first exhaust steam flow line, and the second isolation steam turbine exhaust flow valve is operably coupled to the second exhaust steam flow line and the HRSG steam flow line.

[0072] 10. The power plant of any of the preceding clauses, further comprising a single selective catalytic reduction (SCR) system downstream of the HRSG.

[0073] a gas turbine system; a steam turbine system; a heat recovery steam generator (HRSG) that generates steam from exhaust gas from the gas turbine system; at least one condenser that condenses steam from one of the steam turbine system and the HRSG; and an HRSG steam flow line that supplies the steam from the HRSG to the steam turbine system and the at least one condenser, the HRSG steam flow line including a first HRSG steam flow line that supplies the steam from the HRSG to the steam turbine system, and a second HRSG steam flow line that branches off from the first HRSG steam flow line and supplies the steam from the HRSG to the at least one condenser. and a second HRSG steam flow line supplying at least one condenser; and an HRSG steam flow valve apparatus operatively coupled to the HRSG steam flow line, the HRSG steam flow valve apparatus configured to direct a flow of steam generated in the HRSG to the at least one condenser, bypassing the steam turbine system, during a simple cycle operating mode, and the HRSG steam flow valve apparatus configured to direct the flow of steam generated in the HRSG to the steam turbine system during a combined cycle operating mode.

[0074] 10. The combined cycle power plant of claim 1, wherein the HRSG steam flow valve arrangement comprises an array of three-way HRSG steam flow or isolation valves operably coupled to the HRSG steam flow lines.

[0075] 10. The combined cycle power plant of claim 9, wherein the three-way HRSG steam flow valve of the HRSG steam flow valve device includes an inlet for receiving the steam flow generated from the HRSG, a first outlet for directing the steam flow generated from the HRSG to the at least one condenser, and a second outlet for directing the steam flow generated from the HRSG to the steam turbine system, wherein opening and closing of the three-way HRSG steam flow valve is determined according to the operating modes of the gas turbine system, the HRSG, and the steam turbine system, wherein in the simple cycle operating mode, the first outlet of the three-way HRSG steam flow valve is opened and the second outlet of the three-way HRSG steam flow valve is closed, and in the combined cycle operating mode, the first outlet of the three-way HRSG steam flow valve is closed and the second outlet of the three-way HRSG steam flow valve is opened.

[0076] 10. The combined cycle power plant of claim 9, wherein the array of isolation valves of the HRSG steam flow valve apparatus comprises: a first isolation HRSG steam flow valve operably coupled to the first HRSG steam flow line to stop the flow of the steam from the HRSG to the steam turbine system; and a second isolation HRSG steam flow valve operably coupled to the second HRSG steam flow line to stop the flow of the steam from the HRSG to the at least one condenser.

[0077] the at least one condenser comprises at least one dedicated steam turbine condenser and one or more incremental HRSG condensers; a steam turbine exhaust line supplying exhaust steam from the steam turbine system to the at least one condenser, the steam turbine exhaust line including a first exhaust steam flow line supplying the exhaust steam from the steam turbine system to the at least one dedicated steam turbine condenser; and a second exhaust steam flow line in fluid communication with the first exhaust steam flow line branching from the HRSG steam flow line and receiving a diverted stream of HRSG steam for supplying the at least one dedicated steam turbine condenser. 10. The combined cycle power plant of claim 9, further comprising: a steam turbine exhaust line comprising a first exhaust steam flow line and a second exhaust steam flow line; and a steam turbine flow valve apparatus operatively coupled to the steam turbine exhaust line and supplying the exhaust steam from the steam turbine system to the at least one condenser, the steam turbine flow valve apparatus comprising an array of three-way steam turbine exhaust steam flow valves or isolation steam turbine exhaust flow valves, and both the three-way steam turbine exhaust steam flow valves and the array of isolation steam turbine exhaust flow valves further comprising steam turbine flow valve apparatus operatively coupled to the first exhaust steam flow line and the second exhaust steam flow line.

[0078] 10. The combined cycle power plant of claim 1, wherein the second exhaust steam flow line is fluidly coupled to a second HRSG steam flow line, and the one or more incremental HRSG condensers are configured to receive HRSG steam from the second HRSG steam flow line during a simple cycle operating mode and to receive exhaust steam from the steam turbine system during a combined cycle operating mode.

[0079] 1. A method of operating a power plant having a gas turbine system, a steam turbine system, a heat recovery steam generator (HRSG) that generates steam from an exhaust gas of the gas turbine system, and a condenser that condenses steam selectively provided from one of the steam turbine system and the HRSG, comprising providing a steam flow valve apparatus having at least one valve operatively coupled to the steam turbine system, the HRSG, and the condenser, the steam flow valve apparatus being configured to direct a flow of steam generated by the HRSG to bypass the steam turbine system and to the condenser during a simple cycle operating mode, and the steam flow valve apparatus being configured to direct the flow of steam generated by the HRSG to bypass the steam turbine system and to bypass the condenser during a combined cycle operating mode. and designating a position of the at least one valve in the steam flow valve arrangement to operate in the simple cycle operating mode or the combined cycle operating mode, wherein the steam flow valve arrangement is configured to completely stop the flow of steam generated in the HRSG from entering the steam turbine system and to direct all of the steam flow from the HRSG to the condenser in the simple cycle operating mode, and wherein the steam flow valve arrangement is configured to completely stop the flow of steam generated in the HRSG from proceeding to the condenser and to direct all of the steam flow from the HRSG to the steam turbine system in the combined cycle operating mode.

[0080] 10. The method of claim 9, further comprising: specifying the position of the at least one valve in the steam flow valve arrangement to allow a first partial steam flow from the HRSG to the condenser and a second partial steam flow from the HRSG to the steam turbine system when the power plant transitions between a full combined cycle operating mode in which a total steam flow generated in the HRSG is directed to the steam turbine system without being diverted to the condenser and a full simple cycle operating mode in which the total steam flow generated from the HRSG is directed to the condenser, bypassing the steam turbine system. [Explanation of symbols]

[0081] 10 Combined Cycle Power Plant (CCPP) 12 Gas Turbine System 14 Steam Turbine System 16 Compressor 18 Combustor 20 Gas Turbine 22 Compressor / Turbine Shaft 24 Steam turbine sections, segments 26 shaft 28 Generator 30 Condenser, HRSG incremental condenser, dedicated steam turbine condenser 32 Heat Recovery Steam Generator (HRSG) 34 Steam flow valve device, first steam flow valve device 36 HRSG steam flow line 38 Condensate Pump 40 Condensate piping 42 Flue gas 44 Selective Catalytic Reduction (SCR) System 46 NO x Reduced flue gas 48 Three-way HRSG steam flow valve 50 First isolation HRSG steam flow valve, second isolation HRSG steam flow valve 52 CCPP 54 Steam turbine exhaust line, steam flow valve device 56 Three-way steam turbine exhaust steam flow valve 58 First isolation steam turbine exhaust flow valve, second isolation steam turbine exhaust flow valve 60 Steam turbine flow valve device, second steam flow valve device

Claims

1. a gas turbine system (12); a steam turbine system (14); a heat recovery steam generator (HRSG, 32) for generating steam from the exhaust of the gas turbine system (12); a condenser (30) for condensing steam from one of the steam turbine system (14) and the HRSG (32); a first steam flow valve device (34) operably coupled to the steam turbine system (14), the HRSG (32), and the condenser (30), the first steam flow valve device (34) configured to direct a flow of steam generated from the HRSG (32) to the condenser (30), bypassing the steam turbine system (14), during a simple cycle operating mode, and the first steam flow valve device (34) configured to direct the flow of steam generated in the HRSG (32) to the steam turbine system (14) during a combined cycle operating mode; A power plant (10) comprising:

2. 2. The power plant of claim 1, wherein the first steam flow valve device comprises a three-way HRSG steam flow valve having an inlet that receives the steam flow produced from the HRSG, a first outlet that directs the steam flow produced from the HRSG to the condenser, and a second outlet that directs the steam flow produced from the HRSG to the steam turbine system.

3. 3. The power plant (10) of claim 2, wherein the opening and closing of the three-way HRSG steam flow valve (48) is determined according to the operating modes of the gas turbine system (12), the HRSG (32), and the steam turbine system (14), wherein in the simple cycle operating mode, the first outlet of the three-way HRSG steam flow valve (48) is opened and the second outlet of the three-way HRSG steam flow valve (48) is closed, and in the combined cycle operating mode, the first outlet of the three-way HRSG steam flow valve (48) is closed and the second outlet of the three-way HRSG steam flow valve (48) is opened.

4. 2. The power plant of claim 1, wherein the first steam flow valve device comprises a first isolation HRSG steam flow valve that stops the flow of the steam from the HRSG to the steam turbine system, and a second isolation HRSG steam flow valve that stops the flow of the steam from the HRSG to the condenser.

5. Operation of the first isolation HRSG steam flow valve (50) and the second isolation HRSG steam flow valve (50) is determined in response to the operating modes of the gas turbine system (12), the HRSG (32), and the steam turbine system (14), such that in the simple cycle operating mode, the first isolation HRSG steam flow valve (50) is closed to stop the flow of the steam from the HRSG (32) to the steam turbine system (14), and the second isolation HRSG steam flow valve (50) is 5. The power plant (10) of claim 4, wherein in the combined cycle operating mode, the first isolation HRSG steam flow valve (50) is opened to allow the flow of the steam from the HRSG (32) to the steam turbine system (14), and the second isolation HRSG steam flow valve (50) is closed to stop the flow of the steam from the HRSG (32) to the condenser (30).

6. 5. The power plant of claim 4, further comprising: a first HRSG steam flow line that supplies the steam from the HRSG to the steam turbine system; and a second HRSG steam flow line that branches off from the first HRSG steam flow line and supplies the steam from the HRSG to the condenser, wherein the first isolation HRSG steam flow valve is operably coupled to the first HRSG steam flow line and the second isolation HRSG steam flow valve is operably coupled to the second HRSG steam flow line.

7. 2. The power plant (10) of claim 1, wherein the condenser (30) comprises a single condenser sized to handle all steam flows, including steam flows received from the HRSG (32) in the simple cycle operating mode while the steam turbine system (14) is bypassed, and steam flows from the steam turbine system (14) in the combined cycle operating mode.

8. 2. The power plant (10) of claim 1, wherein the condenser (30) comprises at least one dedicated steam turbine condenser (30) that receives steam flow from the steam turbine system (14) in the combined cycle operating mode, and one or more incremental HRSG condensers (30) that receive additional steam flow from the HRSG (32) during the simple cycle operating mode.

9. 10. The power plant of claim 8, further comprising: a second steam flow valve device operatively coupled with each of the steam turbine system and the condenser, the second steam flow valve device comprising a three-way steam turbine exhaust flow valve having a first inlet that receives exhaust steam from the steam turbine system, a second inlet that receives a diverted flow of HRSG steam from the HRSG that is directed to the one or more HRSG incremental condensers, and an outlet that directs the flow of exhaust steam from the steam turbine system to the at least one dedicated steam turbine condenser or directs the diverted flow of HRSG steam to the at least one dedicated steam turbine condenser.

10. 9. The power plant of claim 8, further comprising: a second steam flow valve device operatively coupled with each of the steam turbine system and the condenser, the second steam flow valve device comprising: a first isolated steam turbine exhaust flow valve configured to stop the flow of the exhaust steam from the steam turbine system to the at least one dedicated steam turbine condenser; and a second isolated steam turbine exhaust flow valve configured to stop the flow of the exhaust steam from the steam turbine system to the one or more incremental HRSG condensers, the second isolated steam turbine exhaust flow valve further configured to allow a diversion of HRSG steam from the HRSG to the one or more incremental HRSG condensers to be directed to the at least one dedicated steam turbine condenser.

11. 11. The power plant of claim 10, further comprising: a first exhaust steam flow line supplying the exhaust steam from the steam turbine system to the at least one dedicated steam turbine condenser; and a second exhaust steam flow line branching from an HRSG steam flow line supplying the HRSG steam flow from the HRSG toward the one or more incremental HRSG condensers, the second exhaust steam flow line in fluid communication with the first exhaust steam flow line, the second exhaust steam flow line receiving the diverted flow of the HRSG steam for supplying the at least one dedicated steam turbine condenser, wherein the first isolation steam turbine exhaust flow valve is operably coupled to the first exhaust steam flow line and the second isolation steam turbine exhaust flow valve is operably coupled to the second exhaust steam flow line and the HRSG steam flow line.

12. The power plant (10) of claim 1, further comprising a single selective catalytic reduction (SCR) system (44) downstream of the HRSG (32).

13. 1. A method of operating a power plant (10) having a gas turbine system (12), a steam turbine system (14), a heat recovery steam generator (HRSG, 32) that generates steam from an exhaust of the gas turbine system (12), and a condenser (30) that condenses steam selectively supplied from one of the steam turbine system (14) and the HRSG (32), comprising: providing a steam flow valve arrangement (34) having at least one valve (48, 50) operably coupled to the steam turbine system (14), the HRSG (32), and the condenser (30), the steam flow valve arrangement (34) configured to direct a flow of steam generated by the HRSG (32) to the condenser (30), bypassing the steam turbine system (14), during a simple cycle operating mode, and the steam flow valve arrangement (34) configured to direct the flow of steam generated by the HRSG (32) to the steam turbine system (14) during a combined cycle operating mode; specifying a position of the at least one valve (48, 50) in the steam flow valve device (34) to operate in the simple cycle operating mode or the combined cycle operating mode, the steam flow valve device (34) being configured to completely stop the flow of steam generated in the HRSG (32) from entering the steam turbine system (14) and direct all of the flow of steam from the HRSG (32) to the condenser (30) in the simple cycle operating mode, and the steam flow valve device (34) being configured to completely stop the flow of steam generated in the HRSG (32) from proceeding to the condenser (30) and direct all of the flow of steam from the HRSG (32) to the steam turbine system (14) in the combined cycle operating mode; A method comprising:

14. 14. The method of claim 13, further comprising: specifying the position of the at least one valve in the steam flow valve arrangement to allow a first partial steam flow from the HRSG to the condenser and a second partial steam flow from the HRSG to the steam turbine system when the power plant transitions between a full combined cycle operating mode in which an entire steam flow generated in the HRSG is directed to the steam turbine system without being diverted to the condenser and a full simple cycle operating mode in which the entire steam flow generated from the HRSG is directed to the condenser, bypassing the steam turbine system.

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