Reheat steam temperature turndown control system for heat recovery steam generators.

Abstract

A heat recovery steam generator (HRSG) is disclosed, comprising: a high temperature section including a first reheater coupled in a parallel orientation with at least one high pressure superheater, the first reheater separated from the at least one superheater by at least one partition; an evaporator coupled downstream of the high temperature section, the evaporator configured to extract heat from gas exiting the high temperature section; and a damper system upstream of the evaporator, the damper system configured to bypass gas exiting an outlet of the first reheater and an outlet of the at least one superheater.

Description

[Technical Field]

[0001] The field of the disclosure relates generally to heat recovery steam generators for gas turbine engine exhausts. More particularly, the disclosure relates to a system for achieving steam temperature turndown control in a heat recovery steam generator. [Background technology]

[0002] Heat exchangers are used in various industries to transfer heat from one medium to another. A heat recovery steam generator (HRSG) is an example of a heat exchanger and can be used in combined cycle power plants and similar plants to generate steam and additional power from exhaust gases. The HRSG can use gas turbine engine exhaust to heat a fluid flowing through a heat exchanger within the HRSG, for example, to convert water into steam to feed a steam turbine. In some configurations, the fluid can be steam generated at multiple pressure levels and sent to either the high-pressure, intermediate-pressure, and / or low-pressure sections of the steam turbine. HRSGs typically include a water spray attemperator to reduce the temperature of the high-pressure reheat outlet steam by combining the superheated steam with water so that the steam is cooled as the water evaporates.

[0003] Some combined cycle systems are configured for steam turbine extraction to provide process steam to support industrial, carbon capture, or district heating systems. These steam extractions are typically pressure-controlled to maintain process steam supply pressure over the steam flow or plant load operating range. If the plant load or process steam demand moves outside the allowable operating range for steam extraction from the turbine, they are typically configured to extract steam from a high-pressure steam source and then reduce the pressure and temperature to match the process requirements. This fallback mode is highly inefficient because the process steam does not first expand in the steam turbine to perform work. Operation is most efficient when process steam is obtained from a steam extraction, because the steam performed work while expanding to the (lower) pressure required for the process. The minimum steam turbine load at which process steam extraction is technically feasible is limited because, as the load decreases, the extracted steam temperature gradually increases until the steam turbine components at the extraction point become too hot. This occurs due to the decreasing pressure ratio of steam expansion through the turbine between the steam inlet (where pressure drops with decreasing flow) and the steam extraction (where a valve controls the fixed pressure required to supply process steam users). The ideal location for steam extraction is often downstream of the intermediate pressure (IP) turbine inlet. This necessitates (reheat) steam temperature turndown control at the IP turbine inlet to manage the steam temperature leaving the steam turbine extraction. However, there are limitations to reheat steam temperature control using conventional steam temperature control means. Extending operations with steam extraction enabled is desirable because it is more efficient than switching process steam supply to a higher pressure and temperature source, since such steam no longer has an opportunity to do work by first expanding through the steam turbine.

[0004] Conventional reheat steam temperature control systems, which use water-spray attemperators between reheat sections, are limited by the amount of water that can be safely injected and vaporized within the HRSG. They are also inherently inefficient due to the high levels of energy required to vaporize the spray water within the HRSG. A more efficient approach is to utilize cool steam instead of water to lower the temperature of the steam entering the reheater. However, this approach is also limited by the temperature control authority, which is determined by how much the outlet steam temperature can be lowered.

[0005] Therefore, there is a need in the art for improved reheat steam temperature turndown control in heat recovery steam generator systems. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent No. 9,429,044 Summary of the Invention

[0007] In one embodiment, a heat recovery steam generator is provided that includes a high temperature section including a first reheater coupled in a parallel orientation with at least one high pressure superheater, the first reheater separated from the at least one superheater by at least one partition wall, an evaporator coupled downstream from the high temperature section and configured to extract heat from gases exiting the high temperature section, and a damper system upstream of the evaporator configured to bypass gases exiting an outlet of the first reheater and an outlet of the at least one superheater.

[0008] In yet another embodiment, a power generation system is provided. The power generation system includes a gas turbine configured to generate electric power and to exhaust exhaust gases through an exhaust outlet, and a heat recovery steam generator having a gas inlet in communication with the gas turbine exhaust outlet. The heat recovery steam generator includes a high temperature section including a first reheater coupled in a parallel orientation with at least one high-pressure superheater, the first reheater being separated from the at least one superheater by at least one partition wall, an evaporator coupled downstream of the high temperature section and configured to extract heat from gases exiting the high temperature section, and a damper system upstream of the evaporator configured to bypass gases exiting the first reheater outlet and the at least one superheater outlet. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of a high temperature element of an exemplary prior art power generation system. [Figure 2] 2 is a schematic diagram of an exemplary heat recovery steam generator including a damper system that retrofits the power generation system shown in FIG. 1. [Figure 3A] FIG. 3 is a schematic diagram of the damper system of FIG. 2 in an open state. [Figure 3B] FIG. 3 is a schematic diagram of the damper system of FIG. 2 in a closed state. [Figure 4] FIG. 1 is a schematic diagram of an alternative heat recovery steam generator including a damper system. [Figure 5] FIG. 1 is a schematic diagram of an alternative heat recovery steam generator including a damper system.

[0010] The reference signs used in the drawings and their meanings are listed in summary form in the list of reference signs. As a rule, identical components are provided with the same reference signs in the figures. DETAILED DESCRIPTION OF THE INVENTION

[0011] In the following specification and claims, reference will be made to a number of terms that shall be defined to have the following meanings.

[0012] As used herein, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements. The terms "optional" or "optionally" mean that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not occur.

[0013] Unless otherwise specified, approximating terms such as "generally," "substantially," and "about" used herein indicate that the modified term may apply only to an approximate degree as recognized by one of ordinary skill in the art, rather than to an absolute or complete degree. Thus, values ​​modified by terms such as "approximately," "about," and "substantially" are not limited to the exact value specified. In at least some instances, approximating terms may correspond to the precision of the instrument used to measure the value. Range limits may be specified here and throughout this specification and claims. Such ranges are combinable and / or interchangeable, and include all subranges subsumed within the range, unless the context or language dictates otherwise.

[0014] Furthermore, unless otherwise indicated, terms such as "first," "second," etc. are used herein merely as labels and do not impose any order, position, or hierarchical requirements on the items to which they refer. Further, for example, a reference to a "second" item does not require or exclude the presence of, for example, a "first" or lower-numbered item, or a "third" or higher-numbered item.

[0015] Embodiments of the present disclosure relate to a heat recovery steam generator (HRSG) system that utilizes gas to extend control authority and maintain efficiency of steam temperature control. The system described herein includes an evaporator, a reheater, and a superheater. The system further includes either a damper system or an air diversion system to redirect, reduce, or bypass gas flow to the reheater, thereby facilitating reduction of the reheat steam temperature exiting the HRSG.

[0016] 1 is a block diagram of a high-temperature section of an exemplary power generation system 10 including a gas turbine 20, a HRSG 100, a high-pressure steam turbine 165, and an intermediate-pressure steam turbine 175. Note that the elements shown and labeled on the HRSG 100 are only the forward-most portion of interest in this disclosure. The HRSG 100 includes an inlet section 102 and an outlet interface 104 that directs hot gas 40 to downstream components of the HRSG 100, consisting of economizers, evaporators, and superheaters for HP, IP, and conventional LP steam generation modules (not shown). In some embodiments, the HRSG 100 further includes a downstream emission reduction catalyst (not shown).

[0017] The HRSG 100 receives hot exhaust gas 30 from the gas turbine 20, which flows through a high pressure superheater and reheater section (see high temperature section 110) and an evaporator 150. The HRSG 100 is an indirect heat exchanger, and water or steam may be supplied to the evaporator 150 of the HRSG 100 to extract heat from the hot exhaust gas 30 within the HRSG 100.

[0018] The high-temperature section 110 typically includes a reheater 130 and a high-pressure superheater 120 arranged in series. High-pressure (HP) steam generated in the evaporator 150 is superheated by the exhaust gas 30 as it passes through the HRSG 100, which cools the exhaust gas 30 while providing heat to the steam. The superheater 120 may include a steam outlet 128, and the HP steam exiting the superheater 120 is supplied to an HP steam turbine 165 connected to the steam outlet 128 of the superheater 120. The HP steam turbine expands the steam to intermediate pressure for reheating before entering an intermediate-pressure (IP) steam turbine 175. The reheater 130 includes a steam outlet 138 that supplies the IP steam turbine 175. Additional IP steam 131 may be added to the HP turbine exhaust steam exiting the HP steam turbine 165 and entering the reheater 130. The temperature of the HP steam exiting steam outlet 128 of superheater 120 and the temperature of the IP steam exiting steam outlet 138 of reheater 130 are controlled by injecting water into the steam at desuperheaters (126 or 136), respectively. The steam exiting steam outlet 184 of IP turbine 175 proceeds to a low-pressure turbine and / or process users (not shown).

[0019] The evaporator 150 is downstream of the high temperature section 110 and extracts heat from the exhaust gas 30 exiting the high temperature section 110. The evaporator 150 includes a series of fluid lines (not shown) that extract heat from the exhaust gas 30 exiting the high temperature section 110. The fluid lines of the evaporator 150 are coupled to an HP feedwater system (not shown) by fluid conduits 152, and the economizing section (not shown) is coupled to a feedwater pump system (not shown) that circulates fluid within the system. As the exhaust gas 30 flows through the evaporator 150 and the downstream HP economizer, IP steam generation circuit, and possibly the LP steam generation circuit, the exhaust gas is further cooled before being discharged to a downstream process, such as a stack or a carbon capture system (CCS).

[0020] 2 is a schematic diagram of an exemplary embodiment of a high temperature section of HRSG 100. In the exemplary embodiment, HRSG 100 includes a high temperature section 110 and an evaporator 150 downstream from high temperature section 110. HRSG 100 has an enclosure wall 106 that defines a heated gas duct through which exhaust gases 30 from gas turbine 20 flow (in the direction indicated by arrow 30).

[0021] In the exemplary embodiment, the high temperature section 110 includes at least two high-pressure superheaters 120 coupled in a parallel orientation with at least one reheater 130. Each of the superheaters 120 includes an inlet 122 and an outlet 124, and the reheaters 130 include an inlet 132 and an outlet 134. As used herein, the term "parallel" configuration refers to an arrangement of the heat transfer sections in which the superheaters 120 and reheaters 130 are adjacent to one another with respect to gas flow therethrough, the inlets (122, 132) are upstream of the outlets (124, 134), and the inlets (122, 132) of the superheaters 120 and reheaters 130 are substantially aligned along a plane P. Each of the superheater 120 and reheater 130 is separated by a dividing wall 108, such that only the exhaust gas 30 can enter and exit the inlets (122, 132) and outlets (124, 134) of the superheater 120 and reheater 130, respectively. The dividing wall 108 separating the superheater 120 and reheater 130 is temperature rated and is selected based on the normal / operating gas temperature of the steam-cooled exhaust gas 30. In some embodiments, the dividing wall 108 is temperature rated between about 900°F and about 1300°F.

[0022] In some embodiments, the high temperature section 110 includes a plurality of high pressure superheaters 120 and a plurality of reheaters 130 coupled in a parallel configuration such that each reheater 130 is located between the plurality of superheaters 120, and the plurality of superheaters 120 are separated from the reheaters 130 by partition walls 108.

[0023] The evaporator 150 is downstream of the high temperature section 110 and extracts additional heat from the exhaust gases 32 (indicated by dashed arrows in FIGS. 3A and 3B) exiting the high temperature section 110. In some embodiments, the evaporator 150 is a once-through high pressure evaporator through which feedwater from a fluid conduit 152 of an HP feedwater system (not shown) is flowed.

[0024] In the exemplary embodiment, damper system 160 is used to control steam temperature. Damper system 160 is downstream of high-temperature section 110 (superheater 120 and reheater 130) such that gases exiting the outlets (124, 134) of superheater 120 and reheater 130 pass through damper system 160. Thus, in the exemplary embodiment, damper system 160 is located between high-temperature section 110 and evaporator 150 and can bypass exhaust gases exiting the outlets (124, 134) of superheater 120 and reheater 130. Furthermore, damper system 160 enables turndown and adjustment of the reheat steam temperature exiting high-temperature section 110, facilitating maintaining the steam turbine bleed temperature at steam outlet 184 within the material limits of components within power generation system 10 with pressure-controlled steam turbine bleed enabled.

[0025] The damper system 160 includes independently controlled dampers that are selectively movable at the outlets (124, 134) of the superheater 120 and the reheater 130. In other words, the superheater 120 is upstream of the superheater damper 162, and the reheater 130 is upstream of the reheater damper 163. The dampers (162, 163) can be independently selectively moved to a fully open position / condition (as shown in FIG. 3A ), a fully closed position / condition (as shown in FIG. 3B ), or can be positioned in an intermediate state between the fully open and fully closed positions (hereinafter referred to as a “partially open position”). Adjustment of the reheater damper 163 between the fully open and fully closed positions provides closed-loop temperature control of the reheat steam entering the IP steam turbine 175 over a very wide operating range, since in the fully closed position, no gas flows through the reheater 130, as shown in FIG. 3B . In a similar manner, HP steam temperature may be controlled by adjusting a portion of the superheater damper 162 and / or in conjunction with additional HP steam temperature control equipment (not shown).

[0026] As an example, in FIG. 3A , all dampers (162, 163) are in the fully open position, and gas (indicated by vectors showing the airflow pattern) flows uninterrupted through the superheater 120 and the reheater 130. In some embodiments, the dampers (162, 163) are louvers. In other embodiments, the dampers (162, 163) are flap diverters. In other embodiments, the dampers (162, 163) are diverter dampers. In some embodiments, the dampers (162, 163) are tandem diverters. In some embodiments, the dampers (162, 163) are butterfly dampers. In alternative embodiments, any other type of damper may be used that enables the damper system 160 to function as described herein.

[0027] As shown in FIG. 3B , the reheater damper 163 is in a fully closed position, while the superheater damper 162 is in a fully open position. In this configuration, the reheater damper 163 diverts gas (represented by vectors showing the airflow pattern) toward the superheater 120. In some embodiments, the reheater damper 163 is moved to a partially open position while the superheater damper 162 is in a fully open position, resulting in a gas-side pressure differential between the reheater 130 and the superheater 120, reducing gas flow to the reheater 130. This pressure differential results in an increased velocity of the gas directed toward the superheater 120 as the gas is diverted from the reheater 130, thereby promoting improved heat transfer in the superheater 120. In some embodiments, the damper system 160 includes only the reheater damper 163.

[0028] FIG. 4 illustrates a damper system 260 that is an alternative embodiment to the damper system 160 (shown in FIG. 2 ). In the exemplary embodiment of FIG. 4 , the damper system 260 includes a single reheater damper 263 upstream of the inlet 132 of the reheater 130. The reheater damper 263 can be moved to a fully open position, a fully closed position, or any intermediate position between the fully open and fully closed positions (hereinafter referred to as a “partially open position”). Similar to the damper system 160 of FIG. 2 , the reheater damper 263 selectively reduces exhaust flow to the reheater 130, and the reheater damper 263 diverts gas (as indicated by vectors representing the gas pattern) toward the superheater 120 by selectively moving the reheater damper 263 to one of the fully open, fully closed, or partially open positions.

[0029] In some embodiments, the partition wall 108 separating the reheater 130 from the superheater 120 may be porous to allow gas to partially enter the reheater 130. In some embodiments, one or both of the partition walls 108 have a gap (not shown) formed therein to allow partial gas entry into the reheater 130. The gap may extend along the entire length of one or both of the partition walls 108, or may extend only partially along the length of the partition wall 108 toward the outlets (124, 134) of the reheater 130 and superheater 120. A partial or porous partition wall 108 can limit the maximum authority of reheat steam temperature control and can also smooth the gas temperature profile entering the downstream evaporator 150. As an example, one end 264 of the partition wall 208 is a distance D from the outlets (124, 134) such that gas is partially bypassed from the superheater 120 adjacent to the partition wall 208. Bulkhead 208 is fabricated from a material selected to be rated for and withstand an isothermal temperature differential. Damper system 260 allows for reheat steam temperature turndown and adjustment to maintain steam turbine bleed temperature within the material limits of the components of power generation system 10 with pressure-controlled steam turbine bleed enabled.

[0030] Figure 5 shows a schematic diagram of an alternative embodiment of the HRSG 100 and damper system 160 (shown in Figure 2). In the exemplary embodiment of Figure 5, the HRSG 300 includes a high temperature section 310 having a first reheater 330 and a second reheater 340 in a series configuration and a superheater 320 disposed in a parallel configuration with the first reheater 330 and the second reheater 340, similar to that shown in Figure 1. As used herein, the term series configuration refers to a reheater (330, 340) arrangement such that the outlet 334 of the first reheater 330 is aligned with and upstream of the inlet 342 of the adjacent second reheater 340.

[0031] The first reheater 330 and the second reheater 340 are separated by a series damper 360 to facilitate control of gas flow between the first reheater 330 and the second reheater 340. In an exemplary embodiment, the damper 360 may be, but is not limited to, a louver, a flap diverter, and / or a butterfly damper. Alternatively, any other type of damper that enables the damper system to function as described herein may be used. Similar to the damper system 260 (shown in FIG. 4), the damper 360 may be selectively moved to a fully open position, a fully closed position, or any intermediate position between the fully open and fully closed positions (hereinafter referred to as a "partially open position"). The damper 360 selectively reduces gas flow between the first reheater 330 and the second reheater 340, diverting gas (illustrated by vectors representing the airflow pattern) toward the superheater 320 due to the pressure difference between the parallel-arranged second reheater 340 and the superheater 320. The partition 308 separating the superheater 320 and the second reheater 340 is temperature rated and selected based on the maximum temperature of the steam-cooled exhaust gas 30 observed at the location of the damper 360. The damper 360 allows for turndown and adjustment of the reheat steam temperature exiting the hot section 310, facilitating maintaining the steam turbine bleed temperature within the material limits of the components in the power generation system 10 with pressure-controlled steam turbine bleed enabled.

[0032] The system described herein facilitates reducing or diverting gas flow to the reheater or directly controlling the gas temperature entering the reheater, thereby controlling the reheat steam temperature exiting the hot section of the HRSG. In particular, the damper system regulates the hot and cold gases exiting the hot section so that the evaporator receives gases of approximately the same average temperature, while controlling the steam temperature exiting the reheater. Furthermore, the damper system facilitates increased operational flexibility and improved control of the superheater and reheater loads by diverting gases through selectively opened and closed dampers, rather than relying on desuperheaters to mix spray water or steam intermediate the reheater and superheater. Neither spray water mixing nor steam mixing for steam temperature control has the control authority necessary to significantly extend steam extraction to low-load process operations with pressure-controlled steam turbine extraction in effect.

[0033] The methods, systems, and compositions disclosed herein are not limited to the specific embodiments described herein; rather, method steps, system elements, and / or composition elements can be utilized independently and separately from other steps and / or elements described herein. For example, the methods, systems, and compositions are not limited to practice with only rotating machines as described herein. Rather, the methods, systems, and compositions can be implemented and utilized in connection with many other applications.

[0034] Although specific features of various embodiments may be shown in some drawings and not in others, this is for convenience only. Moreover, references to "one embodiment" in the above description are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. In accordance with the principles of the present disclosure, any feature of a drawing may be referenced and / or claimed in combination with any feature of any other drawing.

[0035] This specification uses some examples, including the best mode, to enable any person skilled in the art to practice the disclosure, including making and using any devices or systems and performing any related methods. The patentable scope of the disclosure 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.

[0036] While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.

[0037] Further aspects of the invention are provided by the subject matter of the following clauses.

[0038] 1. A heat recovery steam generator comprising: a high temperature section including a first reheater coupled in a parallel orientation with at least one high pressure superheater, the first reheater being separated from the at least one superheater by at least one partition; an evaporator coupled downstream of the high temperature section, the evaporator configured to extract heat from gas exiting the high temperature section; and a damper system upstream of the evaporator, the damper system configured to bypass gas exiting an outlet of the first reheater and an outlet of the at least one superheater.

[0039] 10. The heat recovery steam generator of claim 1, wherein the damper system includes a superheater damper coupled to an outlet of the at least one superheater and a reheater damper coupled to an outlet of the first reheater.

[0040] 10. The heat recovery steam generator of claim 9, wherein the superheater damper and the reheater damper are each selectively movable from a fully open position to a fully closed position and to any position between the fully open and fully closed positions.

[0041] 10. The heat recovery steam generator of claim 1, wherein when moved to the fully open position, gas flows uninterrupted through at least one superheater and the first reheater.

[0042] 10. The heat recovery steam generator of any preceding clause, wherein the reheater damper is in a closed position to divert exhaust gases toward the superheater.

[0043] 10. The heat recovery steam generator of claim 1, wherein placing the reheater damper in a partially open position creates a pressure differential between the first reheater and the at least one superheater such that gas flow through the first reheater is reduced.

[0044] 10. The heat recovery steam generator of any preceding clause, wherein the reheater damper and the superheater damper are each at least one of a louver, a flap diverter damper, a tandem damper, and a butterfly damper.

[0045] 10. A heat recovery steam generator as described in any preceding clause, wherein the damper system includes a reheater damper coupled to an inlet of the first reheater, the reheater damper being selectively movable from a fully open position to a fully closed position and to any intermediate position between the fully open and fully closed positions.

[0046] The heat recovery steam generator of any preceding clause, wherein the reheater damper selectively reduces gas flow to the first reheater, and the reheater damper selectively diverts exhaust gas toward at least one superheater by selectively moving the reheater damper to any position from a fully open position to a fully closed position.

[0047] 10. The heat recovery steam generator of claim 1, wherein the at least one partition wall is disposed between the first reheater and the at least one superheater and is porous to allow gas to partially enter the first reheater from the at least one superheater.

[0048] 10. The heat recovery steam generator of claim 9, wherein the at least one partition wall is disposed between the first reheater and the at least one superheater and includes an opening that allows gas to partially enter the first reheater from the at least one superheater.

[0049] 10. The heat recovery steam generator of claim 1, wherein the at least one partition wall is disposed between the first reheater and the at least one superheater and extends a distance from an outlet of the first reheater to allow gas to partially enter the first reheater from the at least one superheater.

[0050] 10. The heat recovery steam generator of claim 1, wherein the high temperature section includes a second reheater in series with the first reheater and a partition between the second reheater and the adjacent superheater(s).

[0051] 10. The heat recovery steam generator of claim 9, wherein the first reheater and the second reheater are separated by a series damper positioned to control gas flow between the first reheater and the second reheater.

[0052] 10. The heat recovery steam generator of claim 9, wherein the series damper selectively reduces gas flow to the second reheater, and the series damper selectively diverts exhaust gas toward the at least one superheater such that a pressure differential is created between the at least one superheater and the second reheater arranged in parallel with the series damper in a partially closed position.

[0053] 10. The heat recovery steam generator of claim 1, wherein the series damper is at least one of a louver, a flap diverter, a tandem damper, and a butterfly damper.

[0054] 1. A power generation system comprising: a gas turbine configured to generate electric power and exhausting exhaust gases through an exhaust port; a heat recovery steam generator having a gas inlet in communication with the gas turbine exhaust port; a high temperature section including a first reheater coupled in a parallel orientation with at least one high pressure superheater, the first reheater being separated from the at least one superheater by at least one partition; an evaporator coupled downstream of the high temperature section, the evaporator configured to extract heat from gases exiting the high temperature section; and a damper system upstream of the evaporator, the damper system configured to bypass gases exiting an outlet of the first reheater and an outlet of the at least one superheater.

[0055] 10. The power generation system of claim 1, wherein the damper system includes a reheater damper coupled to an inlet of the first reheater, the reheater damper being selectively movable from a fully open position to a fully closed position and to any intermediate position between the fully open and fully closed positions.

[0056] 10. The power generation system of claim 9, wherein the high temperature section includes a second reheater in series with the first reheater, the first reheater and the second reheater being separated by a series damper arranged to control airflow between the first reheater and the second reheater. [Explanation of symbols]

[0057] 10 Power Generation System 20 Gas Turbine 30 High-temperature exhaust gas 32 Exhaust gas (from hot parts) 40 Hot Gas 100 Heat Recovery Steam Generator (HRSG) 102 Entrance 104 Exit Interface 106 Enclosure Wall 108 Bulkhead 110 High temperature section 120 High-pressure superheater 122 Inlet (superheater) 124 Outlet (superheater) 126 Overheat prevention device (superheater) 128 Steam outlet (superheater) 130 Reheater 131 IP Steam 132 Inlet (Reheater) 134 Outlet (Reheater) 136 Overheating prevention device (reheater) 138 Steam outlet (reheater) 150 Evaporator 152 Fluid conduit 160 Damper System 162 Superheater damper 163 Reheater damper 165 High-pressure steam turbine 175 Medium-pressure steam turbine 184 Steam outlet (IP turbine) 208 Bulkhead 260 Damper System 263 Reheater damper 264 End (bulkhead) 300 HRSG 308 Bulkhead 310 High temperature section 320 Superheater 330 First Reheater 334 Outlet (1st reheater) 340 Second Reheater 342 Inlet (second reheater) 360 Series Damper

Claims

1. A heat recovery steam generator (100), comprising: a high temperature section (110) including a first reheater (130) coupled in a parallel orientation with at least one high pressure superheater (120), said first reheater (130) being separated from said at least one superheater (120) by at least one partition wall (108); an evaporator (150) coupled downstream of the high temperature section (110), the evaporator (150) configured to extract heat from gas exiting the high temperature section (110); a damper system (160) upstream of the evaporator (150), the damper system (160) configured to bypass gas exiting the outlet (134) of the first reheater (130) and the outlet (124) of the at least one superheater (120); A heat recovery steam generator (100) comprising:

2. 2. The heat recovery steam generator (100) of claim 1, wherein the damper system (160) includes a superheater damper (162) coupled to an outlet (124) of the at least one superheater (120) and a reheater damper (163) coupled to an outlet (134) of the first reheater (130).

3. 3. The heat recovery steam generator of claim 2, wherein the superheater damper and the reheater damper are each selectively movable from a fully open position to a fully closed position and to any position between the fully open and fully closed positions.

4. 2. The heat recovery steam generator of claim 1, wherein the damper system includes a reheater damper coupled to an inlet of the first reheater, the reheater damper being selectively movable from a fully open position to a fully closed position and to any intermediate position between the fully open and fully closed positions.

5. 5. The heat recovery steam generator (100) of claim 4, wherein the reheater damper (263) selectively reduces gas flow to the first reheater (130), and the reheater damper (263) selectively diverts exhaust gas toward the at least one superheater (120) by selectively moving the reheater damper (263) to any position from the fully open position to the fully closed position.

6. 5. The heat recovery steam generator (100) of claim 4, wherein at least one partition wall (208) is disposed between the first reheater (130) and the at least one superheater (120) and is porous to allow gas to partially enter the first reheater (130) from the at least one superheater (120).

7. 5. The heat recovery steam generator (100) of claim 4, wherein the at least one partition wall (208) is disposed between the first reheater (130) and the at least one superheater (120) and includes an opening that allows gas to partially enter the first reheater (130) from the at least one superheater (120).

8. 5. The heat recovery steam generator (100) of claim 4, wherein the at least one partition wall (208) is disposed between the first reheater (130) and the at least one superheater (120) and extends a distance from the outlet (134) of the first reheater (130) to allow gas to partially enter the first reheater (130) from the at least one superheater (120).

9. The heat recovery steam generator (100) of any preceding claim, wherein the high temperature section (310) includes a second reheater (340) in series with the first reheater (330).

10. 10. The heat recovery steam generator (100) of claim 9, wherein the first reheater (330) and the second reheater (340) are separated by a series damper (360) positioned to control gas flow between the first reheater (330) and the second reheater (340).

11. 11. The heat recovery steam generator of claim 10, wherein the series damper selectively reduces gas flow to the second reheater, and the series damper selectively diverts exhaust gas toward the at least one superheater such that a pressure differential is created between the at least one superheater and the second reheater arranged in parallel with the series damper in the partially closed position.

12. The heat recovery steam generator (100) of claim 10, wherein the series damper (360) is at least one of a louver, a flap diverter, a tandem damper, and a butterfly damper.

13. A power generation system (10), comprising: a gas turbine (20) configured to generate electrical power and to exhaust exhaust gases through an exhaust port; A heat recovery steam generator (100) having a gas inlet in communication with the exhaust of the gas turbine (20), a high temperature section (110) including a first reheater (130) coupled in a parallel orientation with at least one high pressure superheater (120), said first reheater (130) being separated from said at least one superheater (120) by at least one partition wall (108); an evaporator (150) coupled downstream of the high temperature section (110), the evaporator (150) configured to extract heat from gas exiting the high temperature section (110); a damper system (160) upstream of the evaporator (150), the damper system (160) configured to bypass gas exiting the outlet (134) of the first reheater (130) and the outlet (124) of the at least one superheater (120); a heat recovery steam generator (100) comprising: A power generation system (10) comprising:

14. 14. The power generation system of claim 13, wherein the damper system includes a reheater damper coupled to an inlet of the first reheater, the reheater damper being selectively movable from a fully open position to a fully closed position and to any intermediate position between the fully open and fully closed positions.

15. 14. The power generation system (10) of claim 13, wherein the high temperature section (310) includes a second reheater (340) in series with the first reheater (330), and the first reheater (330) and the second reheater (340) are separated by a series damper (360) arranged to control airflow between the first reheater (330) and the second reheater (340).

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