SYSTEM AND PROCESS FOR ACTIVE REGULATION OF POWER PLANT DRAWING

Abstract

The invention relates to a combined cycle power plant (CCPP) (10) comprising a turbomachine (12, 12') and a heat recovery steam generator (HRSG) (14, 14') that is shut down (or offline), and a second turbomachine (12, 12') and a heat recovery steam generator (HRSG) (14, 14') that is online. The HRSG-fed duct registers can supply sealing air within them to ensure that there is no backflow from the online turbomachine to the turbomachine shut down at the plant. However, since cooling flow is desired, a regulated flow can be implemented to allow cooling flow to the turbomachine shut down. This solution is advantageous for cooling CCPP configurations with multiple (e.g.,2) HRSGs discharge into a common exhaust stack without individual ducts dedicated to each HRSG, regardless of the turbomachine configuration. Figure for the abbreviation: Fig 1.

Description

Title of the invention: SYSTEM AND PROCESS FOR ACTIVE REGULATION OF POWER PLANT DRAWING technical field

[0001] The disclosure relates generally to a process and system for providing active draft control. In particular, the disclosure relates to a process and system for controlling a naturally induced airflow through combined cycle power plant (CCPP) equipment during a shutdown. BACKGROUND

[0002] Combined cycle power plants equipped with turbomachinery and heat recovery steam generators (HRSGs) are often connected to power grids that require flexible operation to meet varying energy demands. Some power grid cycles require turbomachinery to stop operating during periods of low demand and restart shortly thereafter to meet grid power demands. During operation, the various components of the turbomachinery and HRSGs expand and contract. For example, thermal expansion can occur due to the relatively high temperatures associated with turbine operation, and mechanical expansion can occur due to centripetal forces associated with the rotation of internal components.

[0003] Turbomachine components expand and contract at different and variable rates. These variable rates can result from differences in components in terms of material, geometry, location, and purpose. These differences are generally accounted for in the cooling profiles of the turbomachine components, which are considered in their restart criteria. To further accommodate any divergence in the rates of expansion and contraction, clearance may be provided in the turbomachine between the blade tips and their corresponding casing shrouds, typically referred to as "tip clearance." The tip clearance reduces the risk of turbine damage by allowing the blades to expand without contacting the shroud.

[0004] However, the clearance at the tip significantly reduces the turbine's efficiency during operation by allowing some of the heated gases to escape beyond the blades without performing any useful work, thus wasting energy that would otherwise be available. A similar clearance may be provided in a compressor between the compressor blades and the compressor housing, which may allow air to escape. beyond the compressor blades.

[0005] During shutdown, ambient air may naturally infiltrate through the compressor and the hot exhaust passage of a turbomachine. This ambient air infiltration may be induced, for example, by at least one of the following: natural convection of the hot exhaust gases within the turbomachine, the HRSG and / or the exhaust stacks, and pressure differences caused by wind speed and direction at the turbomachine inlet. Such ambient air infiltration can cool the turbomachine and the HRSG, which may be detrimental to a rapid restart due to functional temperature constraints imposed by the turbomachine and the HRSG. If the HRSG and / or the exhaust are not considered in a cooling profile for a restart, problems may arise in restarting the turbomachine without undesirable friction.

[0006] Undesirable friction can occur due to expansion and an attempted restart when the turbomachine components are still in an "expanded" state, but the stator housing has cooled and contracted until the clearance is no longer adequate for the rotation of the turbomachine components. Problems such as friction and contraction / expansion can result from, for example, the retrofitting of a high-flow storage system (HRSG) and / or turbomachine exhaust, where the design and functional aspects of the retrofitted HRSG are not taken into account in a turbomachine cooling scheme.

[0007] Thus, in order to allow the turbomachine and HRSG to restart as quickly as possible, the induced draft through the turbomachine and HRSG can be actively regulated. Conventionally, to counteract the induced draft, variable inlet guide vanes of the turbomachine compressor (i.e., the vanes at the compressor inlet that regulate the airflow through the turbomachine) are closed and / or inlet dampers and flaps (located, for example, in the inlet section upstream of the compressor) and / or stack dampers (located, for example, at the exhaust stack) are closed. The conventional approach reduces the natural draft through the turbomachine and possibly the HRSG, but due to leaks, a significant amount of induced natural draft may still remain. BRIEF DESCRIPTION

[0008] All aspects, examples and features mentioned below can be combined in any technically possible way.

[0009] One aspect of the disclosure relates to a method for actively regulating draft in a system, the system comprising an operating turbomachine including a turbine and a heat recovery steam generator (HRSG) and a stationary turbomachine including a turbine and an HRSG, the method comprising: the measurement of a turbine speed of the stationary turbomachine; measurement of an exhaust pressure of the stationary turbomachine; measurement of a stationary turbomachine stop time; and on the basis of at least one of the measured speed of rotation, the measured exhaust pressure, and the measured station time, the increase of an exhaust gas temperature of the operating turbomachine to increase a draft flow from the HRSG of the operating turbomachine so that it is equal to a pressure drop at the turbine of the stationary turbomachine.

[0010] Another aspect of the disclosure includes any one of the preceding aspects, and in which, based on at least one of the measured rotational speed, the measured exhaust pressure, and the measured stop time, the adjustment of a draft flow temperature of the operating turbomachine to add subatmospheric pressure at the turbine of the stopped turbomachine.

[0011] Another aspect of the disclosure includes any of the preceding aspects, and in which the increase in the exhaust gas temperature of the operating turbomachine and the adjustment of the draft flow temperature of the operating turbomachine are determined by: comparing the measured rotational speed of the turbine of the stationary turbomachine with a first threshold value; comparing the measured exhaust pressure of the stationary turbomachine with a second threshold value; and comparing the measured stationary time of the stationary turbomachine with a third threshold.

[0012] Another aspect of the disclosure includes any of the preceding aspects, and in which, the first threshold is about 150 revolutions per minute; the second threshold is about -0.1 barg or -0.1105 Pa above ambient or atmospheric pressure; and the third threshold is about 60 minutes.

[0013] Another aspect of the disclosure provides a system, comprising: a stationary turbomachine including a turbine and a heat recovery steam generator (HRSG); an operating turbomachine including a turbine and an HRSG; a common exhaust stack shared by the HRSG of the stationary turbomachine and the HRSG of the operating turbomachine; and a control system configured to raise the exhaust gas temperature of the operating turbomachine to increase the draft flow from the HRSG of the operating turbomachine so that it is equal to a pressure drop at the turbine of the stationary turbomachine, based on at least one of the following: a rotational speed of the turbine of the stationary turbomachine, an exhaust pressure of the stationary turbomachine, and a stationary time of the stationary turbomachine.

[0014] Another aspect of disclosure includes any one of the preceding aspects, and in which the regulatory system is further configured to adjust a operating turbomachine draft flow temperature to add sub-atmospheric pressure at the turbine of the stopped turbomachine, based on at least one of the measured rotational speed, measured exhaust pressure, and measured stop time.

[0015] Another aspect of the disclosure includes any of the preceding aspects, and in which, the system further includes: a sensor for measuring the rotational speed of the turbine of the turbomachine when stopped; a sensor for measuring the exhaust pressure of the turbomachine when stopped; and a timer for measuring the stopping time of the turbomachine when stopped.

[0016] Another aspect of the disclosure includes any of the preceding aspects, and in which the control system is further configured to increase the exhaust gas temperature of the operating turbomachine and adjust the draft flow temperature of the operating turbomachine by: comparing the measured rotational speed of the turbine of the stationary turbomachine with a first threshold value; comparing the measured exhaust pressure of the stationary turbomachine with a second threshold value; and comparing the measured stationary time of the stationary turbomachine with a third threshold.

[0017] Another aspect of the disclosure includes any of the preceding aspects, and in which the control system is configured to increase the exhaust gas temperature of the operating turbomachine and adjust the draft flow temperature of the operating turbomachine when: the rotational speed of the turbine of the stationary turbomachine is less than the first threshold value; the exhaust pressure of the stationary turbomachine is greater than the second threshold; and the stationary time of the stationary turbomachine is greater than the third threshold.

[0018] Another aspect of the disclosure includes any of the preceding aspects, and wherein: the first threshold is about 150 revolutions per minute; the second threshold is about -0.1 barg or -0.1105 Pa above ambient or atmospheric pressure; and the third threshold is about 60 minutes.

[0019] Another aspect of the disclosure includes any of the preceding aspects, and in which the system further includes a first exhaust duct for connecting the HRSG of the operating turbomachine to the common exhaust stack; and a second exhaust duct for connecting the HRSG of the stopped turbomachine to the common exhaust stack.

[0020] Another aspect of the disclosure includes any one of the preceding aspects, and in which at least one of the first exhaust duct and the second exhaust duct are directly connected to the exhaust duct common.

[0021] Another aspect of the disclosure includes any of the preceding aspects, and in which at least one of the first exhaust duct and the second exhaust duct includes a register.

[0022] A further aspect of the disclosure comprises a computer-readable medium including computer-executable instructions which, upon execution, perform a method of actively regulating draft through a system, the system comprising an operating turbomachine including a turbine and a heat recovery steam generator (HRSG) and a stationary turbomachine including a turbine and an HRSG, the method comprising: measuring the rotational speed of the turbine of the stationary turbomachine; measuring the exhaust pressure of the stationary turbomachine; measuring the stationary time of the stationary turbomachine;and based on at least one of the measured rotational speed, the measured exhaust pressure, and the measured stop time, the increase in the exhaust gas temperature of the operating turbomachine to increase the draft flow from the HRSG of the operating turbomachine so that it is equal to a pressure drop at the turbine of the turbomachine when stopped.

[0023] Another aspect of the disclosure includes any one of the preceding aspects, and in which, based on at least one of the measured rotational speed, the measured exhaust pressure, and the measured stop time, the adjustment of a draft flow temperature of the operating turbomachine to add subatmospheric pressure at the turbine of the stopped turbomachine.

[0024] Another aspect of the disclosure includes any of the preceding aspects, and in which the increase in the exhaust gas temperature of the operating turbomachine and the adjustment of the draft flow temperature of the operating turbomachine are determined by comparing the measured rotational speed of the turbine of the stationary turbomachine with a first threshold value; comparing the measured exhaust pressure of the stationary turbomachine with a second threshold value; and comparing the measured stationary time of the stationary turbomachine with a third threshold.

[0025] Another aspect of the disclosure includes any of the preceding aspects, and in which the increase in the exhaust gas temperature of the operating turbomachine and the adjustment of the draft flow temperature of the operating turbomachine are achieved when: the rotational speed of the turbine of the stationary turbomachine is less than the first threshold value; the exhaust pressure of the stationary turbomachine is greater than the second threshold; and the stationary time of the stationary turbomachine is greater than the third threshold.

[0026] Another aspect of disclosure includes any one of the preceding aspects, and in which, the first threshold is about 150 revolutions per minute; the second threshold is about -0.1 barg or 0.1 x 10⁵ Pa above ambient or atmospheric pressure; and the third threshold is about 60 minutes.

[0027] Two or more aspects described in this disclosure, including those described in this summary section, can be combined to form implementations that are not specifically described herein.

[0028] Details of one or more implementations are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will become apparent from the description, drawings, and claims. Brief description of the drawings

[0029] These and other features of this disclosure will be more readily understood from the following detailed description of the various aspects of the disclosure taken in conjunction with the accompanying drawings which illustrate various embodiments of the disclosure, in which:

[0030] [Fig.1]

[0031] is a diagram of a combined cycle power plant (CCPP) comprising two gas turbomachines, each equipped with a heat recovery steam generator (HRSG) sharing a common exhaust stack, and an active draft control system according to disclosure embodiments;

[0032] [Fig.2]

[0033] is a diagram of a CCPP comprising two gas turbomachines, each equipped with an HRSG sharing a common exhaust stack, and an active draft control system according to other disclosure embodiments;

[0034] [Fig.3]

[0035] is an organizational chart of an active draw regulation process through a CCPP according to disclosure embodiments. DETAILED DESCRIPTION

[0036] Combined cycle power plant (CCPP) cooling schemes, which involve the use of a blower / fan (hereinafter "blower") followed by natural cooling, generally rely on periodic openings of exhaust stack dampers. CCPP cooling schemes may also generally rely on thermal draft, for example at subatmospheric pressure levels, at the inlet of an exhaust stack of a heat recovery steam generator (HRSG).

[0037] As incorporated by the disclosure, CCPP cooling schemes typically allow blower flow to continue for several hours (e.g., 4 hours) after shutdown. The blower flow may Induce a natural cooling flow once the blower flow is shut off. During basic load operation of a gas turbomachine / HRSG, the pressure at the inlet of an HRSG exhaust stack may be slightly above atmospheric pressure due, for example, to friction losses in the exhaust stack exceeding thrust gains. In some embodiments of the disclosure, the pressure may be approximately 0.34 mbar, i.e., 0.34 x 10² Pa, or approximately 0.14 inch of H₂O, i.e., 248.082 Pa.

[0038] As incorporated by the disclosure, in a CCPP where one turbomachine / HRSG is stopped (or offline) and a second turbomachine / HRSG is in line, HRSG-fed duct registers may supply sealing air within them to ensure that there is no backflow from the in-line turbomachine / HRSG to the CCPP's stopped turbomachine / HRSG.However, since a cooling flow is desired, a regulated flow can be implemented to allow cooling flow to the turbomachine when it is stopped. This solution is attractive for cooling CCPP configurations with multiple (e.g., 2) HRSGs discharging into a common exhaust stack without individual ducts dedicated to each HRSG, regardless of the turbomachine configuration.

[0039] In the present disclosure, systems and methods for regulating the naturally induced airflow draft through power plant equipment (e.g., a turbomachine) during a shutdown are disclosed. Advantageously, by regulating the naturally induced airflow, heat loss through the stator casing of a turbomachine and the external casing of a high-flow storage generator (HRSG) during a shutdown cycle is reduced. The draft can be induced through the turbomachine either in a downstream direction (normal flow direction) or in an upstream direction (reverse or opposite flow direction), depending on operating and environmental conditions.By reducing heat loss during shutdown, the systems and methods disclosed herein can increase the clearances between the blade tips and the stator housing during a hot restart cycle, thereby preventing tip friction during a hot restart. In other words, by reducing heat loss from the stator housing during the shutdown cycle, larger clearances can be achieved during the hot restart cycle, which can allow for a tightening of the clearances during the steady-state cycle to increase efficiency.

[0040] Referring now to the drawings, in which identical numbers refer to identical components, [Fig. 1] illustrates a combined cycle power plant (CCPP) 10 comprising first and second gas turbomachines 12, 12'. The first gas turbomachine 12 comprises a gas turbine 20, a generator of The first gas turbomachine 12' includes a heat recovery steam generator (HRSG) 14 and an exhaust system 28. The second gas turbomachine 12' also includes a gas turbine 20', an HRSG 14', and an exhaust system 28'. The two gas turbomachines 12, 12' are substantially similar. As incorporated by the disclosure, the two gas turbomachines 12, 12' share a common HRSG exhaust stack 36, as described below.

[0041] The first gas turbomachine 12 further comprises a compressor 16 and a combustion chamber 18. Similarly, the second gas turbomachine 12' further comprises a compressor 16' and a combustion chamber 18'. The gas turbine 20 and / or the gas turbine 20' can be connected to one or more electric generators 22, 22', which are in turn electrically connected to an electrical network (now shown). In other applications, the gas turbine 20 and / or the gas turbine 20' can be connected to other machines as required and as per the design.

[0042] Upstream of the compressor 16, the first turbomachine 12 has an inlet section 24 for ambient air 40 which feeds the compressor 16. In addition, the compressor 16 can typically be equipped with variable inlet guide vanes 26 to regulate the quantity of ambient air 40 that feeds the compressor 16. Similarly, upstream of the compressor 16', the second turbomachine 12' has an inlet section 24' for ambient air 40' which feeds the compressor 16'. In addition, the compressor 16' can also be equipped with variable inlet guide vanes 26' to regulate the quantity of ambient air 40' that feeds the compressor 16'.

[0043] An exhaust system 28 is provided downstream of the gas turbine 20. The exhaust system 28 can be connected to a bypass stack 30 and / or to the HRSG 14. A damper 32 can be provided to selectively connect the exhaust system 28 to the bypass stack 30. An exhaust damper 34 can be provided to selectively connect the exhaust system 28 to the HRSG 14. An exhaust system 28' can also be provided downstream of the gas turbine 20' and can be connected to a bypass stack 30' and / or to the HRSG 14'. A damper 32' and an exhaust damper 34' can also be provided to selectively connect the exhaust system 28' to the bypass stack 30' and to the HRSG 14', respectively.

[0044] As incorporated by the disclosure, a common HRSG exhaust stack 36 can be provided downstream of each HRSG 14, 14' to direct the exhaust to the atmosphere from each HRSG 14, 14'. An exhaust duct 38 connects HRSG 14 directly to the common HRSG exhaust stack 36. Similarly, an exhaust duct 38' connects HRSG 14' directly to the common HRSG exhaust stack 36.

[0045] Figure 2 illustrates an additional configuration of the CCPP 10. In Figure 2, the HRSG 14 has an exhaust duct 42 that leads directly into the common exhaust stack 36. The HRSG 14' has an exhaust duct 44 that connects to the exhaust duct 42 so that a flow from the exhaust duct 44 can be directed to the exhaust stack of the common HRSG 36 via the exhaust duct 42. Thus, as incorporated by the disclosure, an exhaust from the HRSG 14, 14' can flow to the exhaust stack of the common HRSG 36 either directly via exhaust ducts 38, 38' (Figure 1) and an exhaust duct 42 (Figure 2) or indirectly from one of the HRSG 14' via exhaust ducts 42 and 44. ([Fig.2]). While the [Fig.[2] illustrates the HRSG 14 which is directly connected to the common HRSG exhaust stack 36 by the exhaust duct 42, aspects of the disclosure include the direct connection of either the HRSG 14 or the HRSG 14' via its respective exhaust duct 42 or 44 to the common HRSG exhaust stack 36 via the other exhaust duct 44 or 42, respectively.

[0046] With reference to [Fig. 1], in certain aspects of the disclosure, HRSG 46, 46' stack dampers may be provided to close and regulate the flow of exhaust gases from HRSG 14, 14' to the common HRSG exhaust stack 36. The HRSG 46, 46' stack dampers may be provided at the connection of HRSG 14, 14' to the exhaust ducts 38, 38', as illustrated in [Fig. 1]. Another aspect of the disclosure involves positioning HRSG 46, 46' stack dampers at any point along the exhaust ducts 38, 38'.

[0047] As illustrated in [Fig. 2], the HRSG 14 is directly connected via the exhaust duct 42 to the common HRSG exhaust stack 36. In addition, the HRSG 14' is connected to the exhaust duct 44, which is connected to the exhaust duct 42, which in turn is connected to the common HRSG exhaust stack 36. In this sense, HRSG stack registers 48, 48' can be positioned at any point along the exhaust ducts 42, 44, respectively, to regulate the flow of exhaust gases from the HRSG 14, 14' to the common HRSG exhaust stack 36. Furthermore, one aspect of the disclosure involves positioning another HRSG stack register 50 at the intersection of the exhaust duct 42 and the exhaust duct 44 to regulate the exhaust flow between them.

[0048] As incorporated by the disclosure, the use of a common HRSG exhaust stack (e.g., common HRSG exhaust stack 36) coupled to two HRSGs (e.g., HRSGs 14, 14') may prevent cooling The normal pressure of a gas turbine (e.g., gas turbine 20) after a shutdown occurs when the other gas turbine and the other HRSG (e.g., gas turbine 20' and HRSG 14') remain in operation. In some aspects of the embodiments, with the operating gas turbine (e.g., gas turbine 20') running at a high load, the pressure drop at the common HRSG exhaust stack 36 may still exceed the available draft of the common HRSG exhaust stack 36. This pressure differential may result in back pressure to the stationary gas turbine (e.g., gas turbine 20). As incorporated by the disclosure, a control system 60 can be used to provide subatmospheric pressure via active draft control to the stationary gas turbine (e.g., gas turbine 20) with minimal material change and limited power generation loss.

[0049] Figure 3 is a flowchart of a method for actively regulating draft by means of a CCPP (such as the CCPP 10 illustrated in Figures 1 and 2) comprising multiple HRSGs coupled to a common HRSG exhaust stack, according to embodiments of the invention. In the following discussion, the CCPP comprises at least a first gas turbomachine and a second gas turbomachine. The first gas turbomachine comprises a gas turbine, an HRSG, and an exhaust system, and the second gas turbomachine comprises a gas turbine, an HRSG, and an exhaust system. The method can, for example, be implemented by / using a control system such as the control system 60 illustrated in Figures 1 and 2. The control system 60 can be part of the overall control system of the CCPP 10 or be an addition to the overall control system.A single control system 60 may be provided, or each gas turbomachine 12, 12' may have its own control systems which cooperate to provide the functionality of the control system 60 described herein.

[0050] In process P1, a determination is made as to whether one of the gas turbines of the first gas turbomachine or the gas turbine of the second gas turbomachine has stopped and the other of the gas turbine of the first gas turbomachine or the gas turbine of the second gas turbomachine is running. The determination concerning the stoppage can be provided, for example, automatically by the control system 60 or via an operator input to the control system 60. In process P2, the rotational speed of the turbine of the stopped gas turbomachine is measured. For example, as illustrated in Figures 1 and 2, speed sensors 62, 62', coupled to the turbines 20, 20' of the turbomachines 12, 12', can be used to determine the speed of the turbines 20, 20'. In process P3, the exhaust pressure of the stopped gas turbomachine is measured.Exhaust pressure can be measured, for example, as illustrated in Figures 1 and 2. by pressure sensors 64, 64' coupled to the exhaust systems 28, 28' of the turbomachines 12, 12'. In process P4, the time during which the gas turbine has been shut down (e.g., provided by shutdown timers 66, 66') is measured by the control system 60. The turbine speed of the gas turbomachine at standstill and the exhaust pressure of the gas turbomachine at standstill are provided to the control system 60.

[0051] In process P5, the control system 60 compares the turbine speed of the stationary gas turbomachine with a threshold value of X revolutions per minute (rpm). For example, the threshold value of X rpm could be approximately 50 rpm to approximately 300 rpm. In process P6, the control system 60 compares the exhaust pressure of the stationary gas turbomachine with a threshold value of Y (e.g., in bars or in Pascals above ambient or atmospheric pressure (barg)). For example, the threshold value of Y barg could be approximately -0.3 barg, or -0.3 x 10⁵ Pa above ambient or atmospheric pressure, to approximately -0.1 barg, or -0.1 x 10⁵ Pa above ambient or atmospheric pressure. For example, the threshold value of Y (second threshold) can be equal to approximately -0.03 barg or -0.03.105 Pa above ambient or atmospheric pressure to approximately -0.1 barg or -0.1.105 Pa above ambient or atmospheric pressure.

[0052] In process P7, the control system 60 compares the shutdown time of the turbomachine assembly with a threshold value of Z. For example, the threshold value of Z can be equal to about 30 minutes to about 90 minutes.

[0053] The method further includes monitoring the state of a cooling process of the turbomachine when stopped.

[0054] In process P8, the control system 60 receives a required pull signal 70 (Figures 1 and 2) from the stationary gas turbomachine regarding the cooling status of the stationary gas turbomachine. If the stationary gas turbomachine has completed the cooling process (NO in process P8), the operating gas turbomachine returns to nominal operating conditions in process P9. If the stationary gas turbomachine has not completed the cooling process (YES in process P8), the flow proceeds to process P10.

[0055] If the control system 60 has determined that the turbine speed of the gas turbomachine at standstill is less than the threshold value of X rpm (YES in process P5), that the exhaust pressure of the gas turbomachine at standstill is greater than the threshold value of Y (YES in process P6), that the standstill time of the gas turbomachine at standstill is greater than a threshold value of Z (YES in process P7), and that the gas turbomachine at standstill has not completed the cooling process (YES in process P8), then in process P10, the control system 60 provides appropriate control signals (e.g., control signals 68, 68' (Figures 1 and 2)) to The gas turbomachine is in operation. In some embodiments, the control signals: instruct the operating gas turbomachine to increase its exhaust gas temperature to increase the draft flow from the HRSG of the operating gas turbomachine so that it equals the pressure drop at the gas turbine of the gas turbomachine when it is stopped; and instruct the operating gas turbomachine to adjust the draft flow temperature from the HRSG of the operating gas turbomachine to adjust the subatmospheric pressure at the gas turbine of the gas turbomachine when it is stopped. The draft flow from the HRSG of the operating gas turbomachine can be adjusted, for example, by increasing the stack temperature or decreasing the total mass flow.The total mass flow can be reduced, for example, by unloading the operating gas turbomachine. The stack temperature can be increased, for example, by increasing the exhaust temperature of the operating gas turbomachine or by diverting water from the HRSG around economizers (e.g., tube heat exchangers), reducing the efficiency of the HRSG's Rankine cycle.

[0056] According to additional embodiments, the control system 60 can further receive a draft adjustment signal 72 (Figures 1 and 2) from the stationary gas turbomachine requiring more / less draft flow in response to adjustments made to process P10. In response, the control system 60 provides appropriate instructions to the operating gas turbomachine to increase / decrease the draft flow.

[0057] As a person skilled in the art will understand, this disclosure may be incorporated in the form of a system, a method, or controls that may utilize a computer program product. Accordingly, this disclosure may include hardware embodiments, software embodiments (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware aspects, all of which may generally be referred to herein as a "circuit," "module," or "system." Furthermore, this disclosure may take the form of a computer program-enabled control incorporated in any tangible expression medium having computer-usable program code embedded in the medium.

[0058] Any combination of one or more computer-usable or computer-readable media may be used. The computer-usable or computer-readable media may be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor propagation system, apparatus, device, or medium. More specific examples (a non-exhaustive list) of computer-readable media would include the following: a An electrical connection with one or more wires, a laptop diskette, a hard drive, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc with read-only memory (CD-ROM), an optical storage device, a transmission medium such as those supporting the Internet or an intranet, or a magnetic storage device. It should be noted that the computer-usable or computer-readable medium could even be paper or another suitable medium on which the program is printed, since the program can be electronically captured, for example, via optical scanning of the paper or other medium, then compiled, interpreted, or otherwise processed in a suitable manner, if necessary, and subsequently stored in computer memory.In the context of this document, a computer-usable or computer-readable medium can be any medium that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction-executing system, apparatus, or device. The computer-usable medium may include a data signal propagated with the computer-usable program code embedded therein, either in baseband or as part of a carrier wave. The computer-usable program code may be transmitted using any suitable medium, including but not limited to wireless, wired, fiber-optic, RF, etc.

[0059] The computer program code for implementing operations of this disclosure may be written in any combination of one or more programming languages, including an object-oriented programming language such as Java (registered trademark), Smalltalk, C++, or similar, and traditional procedural programming languages ​​such as the C programming language or similar programming languages. The program code may run entirely on the user's computer, partially on the user's computer, partially on the user's computer and partially on a remote computer, or entirely on the remote computer or server.In the latter scenario, the remote computer can be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection can be established with an external computer (e.g., via the Internet using an Internet service provider).

[0060] This disclosure is described herein with reference to flowchart illustrations and / or functional diagrams of processes, devices (systems), and computer program products according to embodiments of the disclosure. It shall be understood that each block in the flowchart illustrations and / or functional diagrams, and combinations of blocks in the illustrations The flowchart and / or functional diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device to produce a machine, such that the instructions, which execute via the computer processor or other programmable data processing device, create means for implementing the functions / actions specified in the flowchart and / or the functional diagram block or blocks.

[0061] These computer program instructions can also be stored in a computer-readable medium that can instruct a computer or other programmable data processing device to operate in a particular way, so that the instructions stored in the computer-readable medium produce a manufactured article comprising instruction means that implement the function / action specified in the flowchart and / or the block or blocks of the functional diagram.

[0062] The flowchart and functional diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of computer program systems, processes, and products according to various embodiments of this disclosure. In this regard, each block in the flowchart or functional diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some implementation variants, the functions inscribed in the block may occur in the order shown in the Figures. For example, two blocks shown successively may, in fact, be executed substantially simultaneously, or the blocks may sometimes be executed in reverse order, depending on the functionality involved.It should also be noted that each block in the functional diagrams and / or flowchart illustration, and combinations of blocks in the functional diagrams and / or flowchart illustration, can be implemented by systems based on special-purpose hardware that perform the specified functions or actions, or combinations of special-purpose hardware and computer instructions.

[0063] As discussed herein, various systems and components are described as "determining" or "obtaining" data. It is understood that the corresponding data can be obtained using any solution. For example, the corresponding system / component can generate and / or be used to generate data, retrieve data from one or more data stores (e.g., a database), receive data from another system / component, and / or similar. When the data is not generated by the particular system / component, it is understood that another system / component may be implemented separately from the represented system / component, which generates the data and provides it to the system / component and / or stores the data for access by the system / component.

[0064] The approximation language, as used throughout the specification and claims, can be applied to modify any quantitative representation that might vary permissively without altering the basic function to which it relates. Accordingly, a value modified by one or more terms, such as "about," "approximately," and "substantially," need not be limited to the precise value specified. In at least some cases, the approximation language may correspond to the precision of an instrument for measuring the value. Here and throughout the description and claims, range boundaries may be combined and / or interchanged; these ranges are identified and include all subranges they contain, unless the context or language indicates otherwise."Approximately" or "about", as applied to a particular value in a range, applies to both extreme values ​​and, unless otherwise stated depending on the accuracy of the instrument measuring the value, may indicate + / - 10% of the value(s) stated.

Claims

1.

2.

3. Demands Method for actively regulating draft by means of a system, the system comprising an operating turbomachine (12, 12') including a turbine (20, 20') and a heat recovery steam generator (HRSG) (14, 14') and a stationary turbomachine (12, 12') including a turbine (20, 20') and an HRSG, the method comprising: - measuring the rotational speed of the turbomachine turbine when stationary; - the measurement of the exhaust pressure of the turbomachine when stopped; - the measurement of the turbomachine's standstill time; and - based on at least one of the measured rotational speed, the measured exhaust pressure, and the measured downtime, the increase in the temperature of the exhaust gases of the operating turbomachine to increase a draft flow from the HRSG of the operating turbomachine so that it is equal to a pressure drop at the turbine of the stopped turbomachine. Method according to claim 1, further comprising, based on at least one of the measured rotational speed, the measured exhaust pressure, and the measured stop time, adjusting a draft flow temperature of the operating turbomachine to add a subatmospheric pressure at the turbine of the stopped turbomachine (12, 12'). A method according to claim 2, wherein the increase in the exhaust gas temperature of the operating turbomachine (12, 12') and the adjustment of the draft flow temperature of the operating turbomachine are determined by: - the comparison of the measured rotational speed of the turbine of the turbomachine at rest (12, 12') with a first threshold value; - the comparison of the measured exhaust pressure of the turbomachine at rest with a second threshold value; and - the comparison of the measured downtime of the turbomachine to stopping with a third threshold.

4. A method according to claim 3, wherein the increase in the exhaust gas temperature of the operating turbomachine (12, 12') and the adjustment of the draft flow temperature of the operating turbomachine are achieved when: - the rotational speed of the turbine of the stationary turbomachine (12, 12') is less than the first threshold value; - the exhaust pressure of the stationary turbomachine is greater than the second threshold; and - the stationary time of the stationary turbomachine is greater than the third threshold.

5. A method according to claim 4, further comprising: - monitoring the state of a cooling process of the turbomachine when stopped (12, 12'); and - returning the turbomachine (12, 12') to nominal operating conditions if the turbomachine when stopped has completed the cooling process.

6. Method according to claim 1, wherein the HRSG of the first turbomachine (12) and the HRSG of the second turbomachine (12') share a common exhaust stack.

7. System (10), comprising: - a stationary turbomachine (12, 12') including a turbine (20, 20') and a heat recovery steam generator (HRSG) (14, 14'); - an operating turbomachine (12, 12') including a turbine (20, 20') and an HRSG (14, 14'); - a common exhaust stack (36) shared by the HRSG of the stationary turbomachine and the HRSG of the operating turbomachine; and - a control system (60) configured to increase the exhaust gas temperature of the operating turbomachine to increase the draft flow from the HRSG of the operating turbomachine so that it is equal to a pressure drop at the turbine of the turbomachine when stopped, based on at least one of a rotational speed of the turbine of the turbomachine when stopped, an exhaust pressure of the turbomachine when stopped, and a stopping time of the turbomachine when stopped.

8. System according to claim 7, wherein the control system (60) is further configured to adjust a turbomachine's operating draft flow temperature to add a subatmospheric pressure at the turbine of the turbomachine at standstill (12, 12'), based on at least one of the measured rotational speed, the measured exhaust pressure, and the measured standstill time.

9. System according to claim 8, further comprising: - a sensor (62, 62') for measuring the rotational speed of the turbine of the turbomachine when stopped (12, 12'); - a sensor (64, 64') for measuring the exhaust pressure of the turbomachine when stopped (12, 12'); and - a timer (66, 66') for measuring the stopping time of the turbomachine when stopped.

10. System according to claim 8, wherein the control system (60) is further configured to increase the exhaust gas temperature of the operating turbomachine (12, 12') and adjust the draft flow temperature of the operating turbomachine (12, 12') by: - ​​comparing the measured rotational speed of the turbine of the stationary turbomachine with a first threshold value; - comparing the measured exhaust pressure of the stationary turbomachine with a second threshold value; and - comparing the measured stationary time of the stationary turbomachine with a third threshold.

11. System according to claim 10, wherein the control system (60) is configured to increase the temperature of the gas of the exhaust of the operating turbomachine (12, 12') and adjust the operating turbomachine draft flow temperature when: - the rotational speed of the turbine of the stationary turbomachine is less than the first threshold value; - the exhaust pressure of the stationary turbomachine is greater than the second threshold; and - the stationary time of the stationary turbomachine is greater than the third threshold.

12. System according to claim 11, wherein - the first threshold is from about 50 revolutions per minute to about 300 revolutions per minute; - the second threshold is from about -0.03 to about -0.1 barg, i.e., from about -0.03 x 10⁵ Pa to about -0.1 x 10⁵ Pa above ambient or atmospheric pressure; and - the third threshold is from about 30 minutes to about 90 minutes.

13. System according to claim 7, further comprising: - a first exhaust duct (38, 38') for connecting the HRSG of the operating turbomachine (12, 12') to the common exhaust stack; and - a second exhaust duct (38, 38') for connecting the HRSG of the stationary turbomachine (12, 12') to the common exhaust stack.

14. System according to claim 13, wherein at least one of the first exhaust duct and the second exhaust duct (38, 38') is directly connected to the common exhaust duct (36).

15. System according to claim 14, wherein at least one of the first exhaust duct and the second exhaust duct (38, 38') comprises a register (46, 46').

16. A computer-readable medium comprising computer-executable instructions which, upon execution, carry out a re- active draft control by means of a system (10), the system comprising an operating turbomachine (12, 12') including a turbine (20, 20') and a heat recovery steam generator (HRSG) (14, 14') and a stationary turbomachine (12, 12') including a turbine (20, 20') and an HRSG (14, 14'), the method comprising: - measuring the rotational speed of the turbomachine turbine when stationary; - the measurement of the exhaust pressure of the turbomachine when stopped; - the measurement of the turbomachine's stopping time; and based on at least one of the measured rotational speed, measured exhaust pressure, and measured stop time, the increase in the exhaust gas temperature of the operating turbomachine to increase a draft flow from the HRSG of the operating turbomachine so that it is equal to a pressure drop at the turbine of the stopped turbomachine.

17. Computer-readable support according to claim 16, wherein the method further comprises, based on at least one of the measured rotational speed, the measured exhaust pressure, and the measured stop time, adjusting a draft flow temperature of the operating turbomachine (12, 12') to add subatmospheric pressure at the turbine (20, 20') of the stopped turbomachine (12, 12').

18. A computer-readable support according to claim 17, wherein the increase in the exhaust gas temperature of the operating turbomachine (12, 12') and the adjustment of the draft flow temperature of the operating turbomachine are determined by: - the comparison of the measured rotational speed of the turbomachine turbine at rest (12, 12') with a first threshold value - the comparison of the measured exhaust pressure of the turbomachine at rest with a second threshold value; and - the comparison of the measured downtime of the turbomachine to stopping with a third threshold.

19. A computer-readable support according to claim 18, wherein the increase in the exhaust gas temperature of the operating turbomachine (12, 12') and the adjustment of the draft flow temperature of the operating turbomachine (12, 12') are achieved when: - the rotational speed of the turbomachine turbine when stopped is less than the first threshold value; - the exhaust pressure of the turbomachine at rest is above the second threshold; and - the turbomachine's standstill time is greater than the third threshold.

20. A computer-readable medium according to claim 19, wherein the method further comprises: - monitoring the state of a turbomachine cooling process when stopped (12, 12'); and - the return of the operating turbomachine (12, 12') to nominal operating conditions if the stopped turbomachine has completed the cooling process.

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