Patent Application
20220025786
The disclosure relates generally to dual cycle power plants and, more particularly, to a damper system including sets of louvered dampers and an air insertion system for controlling gas turbine exhaust parameters for a heat recovery system.
Dual cycle power plants include a power generation system that creates excess heat that can be used for other purposes. For example, a cogeneration plant creates power and excess heat that can be used for other purposes. Similarly, combined cycle power plants (CCPP) include a gas turbine (GT) system that creates power and excess heat that can be used to create steam for a steam turbine (ST) system that also creates power. In a simple cycle operation of the CCPP, the GT system is operated alone to generate power, and exhaust therefrom is directed via a diverter or bypass damper through a bypass exhaust stack. The bypass exhaust stack may include any variety of environmental exhaust treatment systems that treat the exhaust gas prior to exiting it to the atmosphere. In the combined cycle operation of the CCPP, the hot exhaust from the GT system is directed by the bypass damper to a heat recovery system, e.g., a heat recovery steam generator, to create steam for the ST system, prior to it being exhausted to the atmosphere. In the combined cycle, both the GT system and the ST system generate power.
An ST system startup ideally includes gradually increasing temperature of the system to prevent damage to the system. The ST system temperature is increased through, among other things, controlling the amount of steam created by the heat recovery system and applied to the ST system. The bypass damper used to re-direct GT system exhaust from the exhaust stack to the heat recovery system may include a single or double blade closure or a flap valve. The blade(s) either swing open or closed on an end pivot point or slide open/closed (the latter may be referred to as a guillotine damper). The bypass damper is typically designed to be in an open or a closed position.
In operation, the GT system creates hot exhaust and, when the ST system is ready to start, the bypass damper is opened, exposing the heat recovery system to the hot exhaust to create steam for the ST system. This all-or-nothing approach makes a gradual, controlled startup of the ST system challenging and exposes the components upstream of the heat recovery system and in the heat recovery system to potentially severe thermal stress during rapid heating. The severe stresses can reduce the usable lifetime of these components.
In order to address these challenges, in one approach, exhaust temperature control is provided by controlling the output of the GT system, but this approach may disadvantageously reduce plant output and power availability. In another approach, the bypass damper is used to attempt to control, among other aspects, the mass flow of the exhaust to the heat recovery system by positioning the bypass damper in a partially open position, e.g., 10%, 20%, etc. This method and structure pose a number of shortcomings. Notably, the blade bypass damper does not provide sufficient control of the exhaust flow because it includes no more than one or two blades that are only really capable of either an open or closed position. In any of the partially open positions, the one or two blades lack sufficient control of the application of back pressure in the GT system, which is advantageous during fast start or cycling operation. In addition, in between the closed and opened settings, current bypass dampers can cause, among other issues, reverse flow or turbulence in the exhaust, creating uneven heat transfer in the heat recovery system. The inability to control the rate of heating of the heat recovery system caused by the current bypass damper thus presents difficult challenges to controlling the temperature of an ST system, e.g., during startup.
Another shortcoming of current bypass dampers is the minimal mass flow control for the exhaust entering the heat recovery system. The lack of better mass flow control can also lead to difficulty controlling the heating of the heat recovery system and volume of steam it generates.
An aspect of the disclosure provides an exhaust control damper system for a combined cycle power plant, the damper system comprising: a frame configured to be fluidly coupled in an exhaust flow path from a gas turbine (GT) system to a heat recovery system; at least two sets of louvered dampers in the frame and collectively covering the exhaust flow path, each set of louvered dampers including a plurality of blades collectively angularly positionable in one of: a fully open position, a fully closed position, and a partially open position; and an air insertion system operatively coupled to the frame and configured to insert an airflow into the exhaust flow path.
Another aspect of the disclosure provides a power plant, comprising: a gas turbine (GT) system; a steam turbine (ST) system; a heat recovery steam generator operatively coupled to the GT system and the ST system; an exhaust control damper system, including: a frame configured to be fluidly coupled in an exhaust flow path from the GT system to the heat recovery steam generator; at least two sets of louvered dampers in the frame and collectively covering the exhaust flow path, each set of louvered dampers including a plurality of blades collectively angularly positionable in one of: a fully open position, a fully closed position, and a partially open position; and an air insertion system operatively coupled to the frame and configured to insert an airflow into the exhaust flow path.
The illustrative aspects of the present disclosure are designed to solve the problems herein described and/or other problems not discussed.
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 that depict various embodiments of the disclosure, in which:
It is noted that the drawings of the disclosure are not necessarily to scale. The drawings are intended to depict only typical aspects of the disclosure and therefore should not be considered as limiting the scope of the disclosure. In the drawings, like numbering represents like elements between the drawings.
As an initial matter, in order to clearly describe the subject matter of the current disclosure, it will become necessary to select certain terminology when referring to and describing relevant machine components within a power plant. To the extent possible, common industry terminology will be used and employed in a manner consistent with its accepted meaning. Unless otherwise stated, such terminology should be given a broad interpretation consistent with the context of the present application and the scope of the appended claims. Those of ordinary skill in the art will appreciate that often a particular component may be referred to using several different or overlapping terms. What may be described herein as being a single part may include and be referenced in another context as consisting of multiple components. Alternatively, what may be described herein as including multiple components may be referred to elsewhere as a single part.
In addition, several descriptive terms may be used regularly herein, and it should prove helpful to define these terms at the onset of this section. These terms and their definitions, unless stated otherwise, are as follows. As used herein, “downstream” and “upstream” are terms that indicate a direction relative to the flow of a fluid, such as the exhaust from a gas turbine or, for example, the flow of exhaust from a damper system towards a heat exchanger. The term “downstream” corresponds to the direction of flow of the fluid, and the term “upstream” refers to the direction opposite to the flow (i.e., the direction from which the flow originates). The terms “forward” and “aft,” without any further specificity, refer to directions, with “forward” referring to the front or compressor end of the engine, and “aft” referring to the rearward section of the turbomachine.
It is often required to describe parts that are disposed at differing radial positions with regard to a center axis. The term “radial” refers to movement or position perpendicular to an axis. For example, if a first component resides closer to the axis than a second component, it will be stated herein that the first component is “radially inward” or “inboard” of the second component. If, on the other hand, the first component resides further from the axis than the second component, it may be stated herein that the first component is “radially outward” or “outboard” of the second component. The term “axial” refers to movement or position parallel to an axis. Finally, the term “circumferential” refers to movement or position around an axis. It will be appreciated that such terms may be applied in relation to the center axis of the turbine.
In addition, several descriptive terms may be used regularly herein, as described below. The terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur or that the subsequently describe component or element may or may not be present, and that the description includes instances where the event occurs or the component is present and instances where it does not or is not present.
Where an element or layer is referred to as being “on,” “engaged to,” “connected to” or “coupled to” another element or layer, it may be directly on, engaged to, connected to, or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
Embodiments of the disclosure provide an exhaust control damper system for a power plant, such as a cogeneration plant or a combine cycle power plant (CCPP). The damper system includes a frame configured to be fluidly coupled in an exhaust flow path from a gas turbine (GT) system to a heat recovery system. The damper system includes at least two sets of louvered dampers in the frame, which collectively cover the exhaust flow path. Each set of louvered dampers includes a plurality of blades collectively angularly positionable in one of a fully open position, a fully closed position, and a partially open position. The sets of louvered dampers can be modulated to control gas flow distribution to a heat recovery system, such as a heat recovery steam generator. The damper system also provides improved mass flow control of exhaust to the heat recovery system by controlling the position of the different sets of louvered dampers. The damper system can be added to a conventional bypass system or can replace a conventional bypass system in a retrofit setting.
An air insertion system is operatively coupled to the frame and configured to insert an airflow into the exhaust flow path. The air insertion system may mix air with the exhaust flow to the heat recovery system to control the exhaust temperature entering the heat recovery system. The air insertion system allows reduction of thermal stresses on components and provides controlled temperature startup of the ST system without degrading efficiency of the GT system. Hence, the GT system can be started in simple cycle mode, and later the heat recovery system can be started with controlled gas temperature and mass flow according to the heat recovery system and the ST system requirements (gradually higher temperatures, lower thermal stress, etc.).
Gas turbine 108 may be coupled to compressor 104 and/or a generator 114 through one or more shafts 116. During operation, compressor 104 may receive air via an inlet filter 118, compress the air, and supply compressed air to combustor 106. In combustor 106, fuel such as natural gas may be introduced and burned to generate hot combustion gases. The combustion gases may be discharged to gas turbine 108 that is rotationally driven due to the expansion of the combustion gases. The rotation of gas turbine 108 may be used to rotate generator 114 through shaft 116 to generate power.
Gas turbine 108 may be coupled to exhaust bypass stack 110 and heat recovery system 112 via an exhaust duct 120. Exhaust duct 120 may include an inlet coupled to the exhaust outlet of gas turbine 108 to receive the high temperature exhaust gas from gas turbine 108. Exhaust duct 120 may include a first outlet coupled to exhaust bypass stack 110 and a second outlet coupled to heat recovery system 112. Exhaust bypass stack 110 may receive the high temperature exhaust gas and direct it outside of power plant 100, e.g., through any now known or later developed cleaning systems.
Heat recovery system 112 may receive the high temperature exhaust gas (hereinafter “exhaust”), recover heat from the exhaust, heat water, and produce steam. Heat recovery system may also be referred to as a heat recovery steam generator (HRSG), where appropriate. Heat recovery system 112 may include a boiler 122 to generate the steam. In one embodiment, heat recovery system 112 may include a supplementary fire duct burner 124 in boiler 122. The steam may be directed to a ST system 134 configured to rotate due to the steam. The rotation of a steam turbine 126 of ST system 134 may rotate a generator 128 through shaft 130 to generate additional power. In other embodiments, the steam from heat recovery system 112 may be used for other applications (e.g., heating or desalination).
As illustrated in
While a flat type bypass damper 132 is illustrated in
Power plant 100 may include one or more sensors 138 to monitor the operation of the power plant. Sensors 138 may monitor the temperature, moisture, flow speed, and/or exhaust composition. Controller 136 of power plant 100 may receive data from sensors 138, analyze the data to determine the operating state of the power plant, and generate controls for the power plant based on the received data from sensors 138.
Power plant 100 may further include an exhaust control damper system 140 (hereinafter “damper system 140”) to provide additional control over exhaust prior to its introduction to heat recovery system 112.
Damper system 140 includes a frame 142 configured to be fluidly coupled in an exhaust flow path from GT system 108 (
As shown in
Frame 142 may be coupled to a new power plant 100 or may be retrofitted to an existing power plant 100. To this end, frame 142 may have an adjustment member(s) 146 configured to allow adjustment of a size of the frame. Adjustment member(s) 146 may include any now known or later developed structure for allowing frame 142 to have different sizes to accommodate different sized exhaust ducts 120 and/or heat recovery systems 112. In one non-limiting example, adjustment member 146 may include a selection from a variety of different length plate members.
Damper system 140 also includes at least two sets of louvered dampers 150 in frame 142, which collectively cover the exhaust flow path. Each set of louvered dampers 150 includes a plurality of blades or vanes 152 collectively angularly positionable in one of: a fully open position (shown in outer two in
Each set of louvered dampers 150 may also include an actuator 156 configured to control operation of position transmission 154 to position the respective set of louvered dampers 150 in the one of: the fully open position, the fully closed position, and the partially open position. Controller 136 may control each actuator 156 to control, among other things, the mass flow of exhaust through frame 142. Actuator(s) 156 may include any appropriate motorized actuator, e.g., electric, hydraulic, pneumatic, etc., capable of moving the position transmission 154. For example, actuator(s) 156 may be rotational actuators (shown in
While four sets of louvered dampers 150 are shown in each of
In the example shown, blades 152 are vertically spaced and rotate about a horizontal axis. It is readily understood that the blades 152 could also be horizontally spaced and rotate about a vertical axis, i.e., with actuators 156 on the side of frame 142. As shown for example in
Damper system 140 also includes an air insertion system 160 (
In
As shown in
During operation, power plant 100 may be controlled to operate in a simple cycle to generate energy only from the operation of gas turbine 108 or in a combined cycle to generate energy from the operation of gas turbine 108 and heat recovery system 112. In the simple cycle, bypass damper 132 may be controlled to be in the first position (vertical) to shut off the flow of exhaust to heat recovery system 112. In the simple cycle, the exhaust from gas turbine 108 may flow to exhaust bypass stack 110 via exhaust duct 120.
In the combined cycle, bypass damper 132 may be controlled to be in the second position (horizontal) to shut off the flow of exhaust to exhaust bypass stack 110. In the combined cycle, the exhaust from gas turbine 108 may flow to damper system 140, and eventually to heat recovery system 112 via exhaust duct 120, to recover additional energy from the exhaust gas. Damper system 140 controller 136 is configured to control the position of sets of louvered dampers 150 and the operation of air insertion system 160 to control at least one of: an exhaust flow temperature downstream of frame 142; an exhaust mass flow rate downstream of frame 142; and a back pressure upstream of frame 142, i.e., on GT system 108. Controller 136 may be part of power plant 100 control system or a separate controller.
When starting up power plant 100, the power plant may be set in simple cycle or combined cycle. For startup in the simple cycle, bypass damper 132 may be set in the first position (vertical) to shut off the flow of exhaust to heat recovery system 112 and to allow the generated exhaust to flow to exhaust bypass stack 110. After the start-up of gas turbine 108, the exhaust is introduced into exhaust duct 120 and all of the exhaust flows outside of power plant 100 via exhaust bypass stack 110. After predetermined conditions are satisfied (e.g., predetermined time period, temperature, composition of the exhaust gas), bypass damper 132 may be controlled to transition to a second position (horizontal) to allow the exhaust to flow to heat recovery system 112 and to block the exhaust from flowing to exhaust bypass stack 110.
During the transition from the first position to the second position, a portion of the exhaust may flow to heat recovery system 112 and a portion of the exhaust may flow to exhaust bypass stack 100. By controlling the speed of the transition, the amount of exhaust introduced into heat recovery system 112 may be controlled in a limited manner by bypass damper 132 to reduce stress on the components of heat recovery system 112 due to a drastic temperature change. In accordance with embodiments of the disclosure, damper system 140 may be operated to provide further control of the exhaust flow to reduce stress on components of heat recovery system 112, both during the transition and after the transition. Thus, damper system 140 may reduce hazards to heat recovery system 112 of power plant 100, created by the lack of fine-tuned control of bypass damper 132.
For example, damper system 140 can guard against over-pressure or under-pressure in exhaust duct 120. Damper system 140 can also remove turbulence and better control mass flow of exhaust to heat recovery system 112. Air insertion system 160 allows control of exhaust temperature, providing further protection against thermal stress to heat recovery system 112 or upstream components. Damper system 140 may also be controlled with bypass damper 132 and stack damper 172 of heat recovery system 112, e.g., to reduce the possibility of overpressure in exhaust duct 120.
In another embodiment, shown in
Embodiments of the disclosure provide an exhaust control damper system 140 that can provide additional exhaust control for heat recovery system 112. Damper system 140 can provide better back pressure control in GT system 102 than a bypass damper 132, even those bypass dampers 132 using multiple gates. For example, the system provides less back-pressure in GT system 102 during fast-start or cycling operation. Hence, the system allows fast startup of the GT system 102 while reducing any potential thermal stress on heat recovery system 112. Damper system 140 is also more reliable than single blade bypass dampers that may create turbulence or flow reversal at partial opening. Damper system 140 further provides improved control of exhaust mass flow to heat recovery system 112, providing more control of ST system 134 startup. Damper system 150 is flexible, adjustable, and easy to install in any configuration or power plant framework either as a new build or as a retrofit.
Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about,” “approximately” and “substantially,” are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged; such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. “Approximately,” as applied to a particular value of a range applies to both end values and, unless otherwise dependent on the precision of the instrument measuring the value, may indicate +/−10% of the stated value(s).
The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description but is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The embodiment was chosen and described in order to best explain the principles of the disclosure and the practical application and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.
