JP2015094305A - Steam turbine system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve conventional problems that it is necessary to exert a flow control over cooling steam depending on a load so as to prevent a sharp temperature change of a rotor that occurs when the cooling steam flows in an intermediate turbine in a case of supplying extracted steam from a high pressure turbine to the intermediate pressure turbine as the cooling steam while an opening is kept constant after rated load operation, which results in flow of the cooling steam equal to or larger than a necessary flow for the rated load and in the waste of steam that is originally to be used for the high pressure turbine.SOLUTION: A steam turbine system including: a high pressure turbine 1; an intermediate pressure turbine 2 separate from the high pressure turbine 1; and a system 3 transforming extracted steam from the high pressure turbine 1 to cooling steam for the intermediate pressure turbine 2, comprises: a control valve 4 provided in the cooling steam system for flow controlling over the cooling steam; and a controller 30 consecutively reducing an opening of the control valve 4 depending on an increase in turbine load.

Description

  The present invention relates to steam turbine equipment, and more particularly to a rotor cooling device for the steam turbine equipment.

  Steam turbine equipment cools the turbine rotor by mixing low-temperature steam (cooling steam) extracted from the high-pressure turbine and medium-pressure turbine in addition to high-temperature steam (reheated steam) discharged from the high-pressure turbine and heated. Some have a rotor cooling device. The purpose of introducing the reheat steam and the cooling steam into the intermediate pressure turbine by the rotor cooling device is that when only the high temperature reheat steam is introduced into the intermediate pressure turbine, the introduction portion of the turbine rotor (for example, the center of the turbine rotor) The elongation ratio of the material in the part of the turbine rotor is larger than other parts of the turbine rotor (for example, bearing parts located at both ends of the turbine rotor), causing the turbine rotor to bend, generating vibration during operation and hindering plant operation. This is to prevent this.

  As background art of this technical field, there is JP-A-55-29004 (Patent Document 1). This publication discloses a technique relating to “a rotor cooling device for a steam turbine that prevents excessive thermal stress from being applied to the material of each part of the turbine when the turbine is started and stopped, and therefore does not shorten the life of the turbine”. In the rotor cooling device of the steam turbine, “the turbine material is obtained by continuously controlling the opening degree of the cooling steam supply valve according to the load of the turbine and detecting the reheat steam temperature and the cooling steam pressure. The cooling steam supply valve opening degree is controlled in accordance with the temperature characteristic of “

  There is also JP-A-1-190903 (Patent Document 2). This publication states that “a steam turbine temperature that can control the cooling steam temperature when the cooling steam flows into the intermediate-pressure turbine at the time of start-up, and that can prevent a rapid temperature change of the rotor that occurs when the cooling steam flows in. The technology related to the “cooling steam temperature control device” is disclosed, and the cooling steam temperature control device for the steam turbine is “a control valve provided in a line for introducing reheated steam in the cooling steam system is activated at an intermediate pressure. In this case, it is described that a means for adjusting and controlling the opening degree is provided so as to control the temperature of the cooling steam in accordance with the load of the generator driven by the steam turbine.

Japanese Patent Laid-Open No. 55-29004 JP-A-1-190903

  In the technologies according to the above two documents, when the steam extracted from the high-pressure turbine is supplied as cooling steam to the intermediate pressure turbine at the “starting and stopping” time of the steam turbine, the cooling steam flow rate provided in the cooling steam system is controlled. By increasing the opening of the control valve (cooling steam supply valve) according to the increase in the turbine load, the rapid temperature change of the rotor that occurs when cooling steam flows in is prevented. However, the opening degree of the control valve is kept constant (maximum) between “from the time when the transition to the rated load operation is completed and before the stop operation is started” of the steam turbine. Therefore, after reaching the rated load, the cooling steam exceeding the required flow rate is extracted from the high-pressure turbine, and the steam that should originally work in the high-pressure turbine is wasted, and improvement in energy efficiency is required.

  An object of the present invention is to provide a steam turbine facility that can improve the energy efficiency after the transition to the rated load operation of the steam turbine and before the start of the stop operation.

  To achieve the above object, the present invention provides a first turbine, a second turbine separated from the first turbine, driven by steam heated from the first turbine, A cooling steam system that supplies the extracted steam from the first turbine as cooling steam for the second turbine, a control valve that is provided in the cooling steam system and controls the flow rate of the cooling steam, and the turbine load reaches a rated load And a control device for controlling the opening of the control valve to be smaller as the turbine load is larger.

  According to the present invention, it is possible to improve the energy efficiency between the transition from the rated load operation of the steam turbine to the start of the stop operation.

1 is a schematic configuration diagram of a steam turbine facility according to a first embodiment of the present invention. The relationship figure of the turbine load and target opening which are set with the setting device of the 1st Embodiment of this invention. The schematic block diagram of the steam turbine equipment which concerns on the 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The “turbine load” in this paper refers to a load that acts on all turbines mechanically connected to the generator when a certain generator is driven. FIG. 4 shows loads acting on three turbines (high-pressure turbine 1, intermediate-pressure turbine 2, and low-pressure turbine 21) mechanically connected to the generator 7. Moreover, in each figure, the same code | symbol may be attached | subjected to the same part and description may be abbreviate | omitted.

<First Embodiment>
In the present embodiment, a rotor cooling device 100 that continuously adjusts the flow rate of cooling steam according to the turbine load after reaching the rated load will be described. FIG. 1 is a schematic configuration diagram of a steam turbine facility according to a first embodiment of the present invention.

  The steam turbine equipment (steam turbine power plant) shown in this figure includes a boiler (not shown) that generates steam, a high-pressure turbine 1 (first turbine) that is driven by the steam generated in the boiler, and a high-pressure turbine 1. An intermediate pressure turbine 2 (second turbine) driven by steam discharged from the high pressure turbine 1, a low pressure turbine 21 driven by steam discharged from the intermediate pressure turbine 2, and a low pressure A water supply system (not shown) including a condenser (not shown) for reducing and condensing the pressure of steam discharged from the turbine 21 and a feed water pump for transferring the condensed water condensed in the condenser to the boiler. A generator 7 mechanically connected to the turbine shafts of the high-pressure turbine 1, the intermediate-pressure turbine 2, and the low-pressure turbine 21, and extracted steam ( And a rotor cooling device 100 for cooling the rotor is introduced into the intermediate pressure turbine 2-ring steam).

  In the present embodiment, one or a plurality of reheaters (not shown) are installed in the middle of a path for supplying steam discharged from the high pressure turbine 1 to the intermediate pressure turbine 2, and are discharged from the high pressure turbine 1. After being heated by the reheater, the steam is guided to the intermediate pressure turbine 2 to drive the intermediate pressure turbine 2 to rotate. In addition, a configuration in which a reheater is installed in the middle of a path for guiding the steam discharged from the intermediate pressure turbine 2 to the low pressure turbine 21 and the steam heated by the reheater is introduced into the low pressure turbine 21 may be adopted. good.

  The rotor cooling device 100 includes a load detector 8 that detects a turbine load based on the output of the generator 7, and a steam supply pipe (cooling) for supplying extracted steam from the high-pressure turbine 1 as cooling steam of the intermediate-pressure turbine 2. Steam system) 3, cooling steam flow control valve (flow control valve) 4 provided on the steam supply pipe 3, orifice 5, cooling steam inlet valve 6, and control for controlling the opening degree of the flow control valve 4. The apparatus 30 (the arithmetic unit 9, the setting device 10, and the oscillator 11) is provided.

  The flow rate control valve 4, the orifice 5 and the inlet valve 6 are arranged in the introduction pipe 3 in this order from upstream to downstream in the steam flow direction. The inlet valve 6 is an open / close valve, and is opened / closed based on whether cooling steam is introduced into the intermediate pressure turbine 2. The flow rate control valve 4 is an electric valve, and the opening degree is adjusted based on a control signal oscillated from the control device 30, and the flow rate control of the cooling steam is performed.

  The control device 30 sets the opening degree of the flow control valve 4 based on the magnitude of the turbine load before the steam turbine 1, 2, 21 completes the transition to the rated load operation and before starting the stop operation. It is an apparatus that executes a process to be controlled.

  An output indicating the turbine load is input from the load detector 8 to the control device 30. Based on the output, the control device 30 determines whether the steam turbines 1, 2, and 21 have completed the transition to the rated load operation. It is determined whether or not. When the output confirms that the turbine load has reached 100% load and determines that the transition to the rated load operation has been completed, the control device 30 determines the flow rate from the time when it is determined that the rated load has been reached. Execution of the opening degree control process of the control valve 4 is started. If the turbine load reaches the rated load after the turbine is started, the control device 30 is configured to continue the opening degree control process of the flow control valve 4 even if the turbine load subsequently decreases.

  Further, the control device 30 is configured to receive an output (start command and stop command) from an input device (not shown) for an operator to instruct start / stop of the steam turbine. The control device 30 determines whether or not a stop operation of the steam turbine has been started based on a stop command output from the input device in response to an operator stop instruction. When the input of the stop command is confirmed and it is determined that the stop operation of the steam turbine has been started, the control device 30 stops executing the opening degree control process started when the rated load is reached.

  The control device 30 includes a calculator 9, a setter 10 and an oscillator 11 as a circuit for realizing the opening degree control of the flow control valve 4. The computing unit 9 calculates the turbine load at that time based on the output of the load detector 8. The setter 10 calculates the opening degree (target opening degree) of the flow rate control valve 4 to be targeted based on the turbine load calculated by the calculator 9. The oscillator 11 oscillates with respect to the flow control valve 4 a control signal for controlling the opening of the flow control valve 4 to the target opening calculated by the setting device 10.

  FIG. 2 is a graph showing the relationship between the turbine load and the target opening set by the setting device 10 of the present embodiment. As shown in this figure, the target opening degree of the flow control valve 4 is set so as to continuously decrease as the load on the turbine increases, and the graph in FIG. .

  The relationship between the linear turbine load and the target opening shown in FIG. 2 is merely an example, and if the valve opening is set so as to monotonously decrease as the turbine load increases, the curve Other graphs may be used. The “monotonic decrease” here includes not only (1) “monotonic decrease in a narrow sense” in which the target opening always decreases as the turbine load increases, but also (2) target opening even when the turbine load increases. Even when the degree is held constant, “broad monotonic decrease” which is regarded as a monotonic decrease is also included. The latter includes a case where the target opening increases stepwise (discretely) as the turbine load increases. (Note that “monotonic decrease in a broad sense” is sometimes referred to as “monotonic non-increase” because the target opening degree decreases without increasing as the gas turbine load increases.)

  Note that, instead of the above three circuits (the arithmetic unit 9, the setting unit 10, and the oscillator 11), the control device 30 is configured by a computer, and a control signal is generated by a predetermined program based on the output of the load detector 8 in the computer. And the opening degree control may be performed by outputting the control signal to the flow control valve 4. Further, if the opening degree can be controlled, the opening degree may be controlled manually by an operator.

  In the steam turbine equipment configured as described above, when the operator gives an instruction to start the steam turbine and the turbine load increases and reaches the rated load, the control device 30 starts the opening degree control process of the flow control valve 4. Specifically, the control device 30 calculates the turbine load based on the output from the load detector 8, sets the target opening of the control valve 4 based on the turbine load and the table shown in FIG. A series of processes for oscillating a control signal based on the target opening to the control valve 4 is started. By this process, the opening degree of the control valve 4 is controlled so as to decrease as the turbine load increases.

  By the way, the flow rate of the cooling steam supplied to the intermediate pressure turbine 2 via the steam supply pipe 3 is determined so that the opening area (opening) of the control valve 4 and the opening thereof are fixed if the opening of the orifice 5 and the inlet valve 6 is constant. Proportional to differential pressure before and after. For example, when the turbine load changes from the rated load to a low load less than the rated load, the main steam pressure is also lower than that at the rated load, and the differential pressure across the control valve 4 is also reduced. In this situation, when cooling steam having the same flow rate is supplied to the intermediate pressure turbine 2 before and after the change of the turbine load, the opening degree of the control valve 4 is set to be lower than that before the load reduction (at the rated load) after the turbine load is reduced. Just make it bigger. Therefore, in the present embodiment, the opening degree of the cooling steam flow rate control valve 4 is controlled to be continuously reduced as the turbine load increases.

  According to the present embodiment configured as described above, only the cooling steam (extracted steam) having a flow rate suitable for the turbine load in each case is obtained by the opening degree control of the flow rate control valve 4 based on the turbine load by the rotor cooling device 100. Can be taken out from the high-pressure turbine 1, so that it is possible to prevent excessive cooling steam from occurring as in the conventional constant opening degree control. Therefore, according to the present embodiment, it is possible to improve the energy efficiency between the transition from the rated load operation of the steam turbine to the start of the stop operation.

  In the above description, the case where the cooling steam flow rate is controlled to be constant before and after the change of the turbine load has been described for the sake of simplicity. However, the flow rate control valve 4 is configured so that the cooling steam flow rate increases as the turbine load increases. The opening degree may be controlled. In this case, since the steam flow rate suitable for the turbine load can be selected, the energy efficiency can be further improved.

<Second Embodiment>
In the second embodiment of the present invention, not only continuously adjusting the flow rate of the cooling steam according to the turbine load, but also when the required flow rate of the cooling steam changes from the start of turbine use due to the aging of the turbine. Also, an example of the rotor cooling device 200 that can easily follow the change will be described.

  FIG. 3 is a schematic configuration diagram of a steam turbine facility according to the second embodiment of the present invention. The steam turbine equipment shown in this figure includes a manual flow rate adjusting valve 15 instead of the orifice 5 in the first embodiment.

  In the steam turbine equipment configured as described above, when the required steam flow rate of the cooling steam is changed from the start of use due to the aging of the turbine, the opening of the manual flow rate adjustment valve 15 is changed, whereby the control device 30 Secular change of the required amount of cooling steam without changing the setting of the opening degree control of the cooling steam flow control valve 4 (that is, the relationship between the turbine load and the target opening degree shown in FIG. 2) from the first embodiment. The flow rate can be controlled according to the For example, when the required flow rate of the cooling steam increases due to aging of the turbine, the opening amount of the manual flow rate adjustment valve 15 is increased until the increased amount can be absorbed while the setting in the setting device 10 is maintained. It is possible to cope with the required steam volume change due to the aging of the turbine. Needless to say, the reverse operation may be performed when the required flow rate decreases.

  By the way, in each said embodiment, although the case where there were three turbines was demonstrated, other turbines driven with the reheat steam of one turbine like the high pressure turbine 1 and the intermediate pressure turbine 2 which were demonstrated above. The present invention can be applied to the turbine included in the steam turbine equipment, as long as the steam extracted from the one turbine is used as cooling steam for the other turbine. The number is not limited to three.

  In addition, this invention is not limited to said embodiment, The various modifications within the range which does not deviate from the summary are included. For example, the present invention is not limited to the one having all the configurations described in the above embodiment, and includes a configuration in which a part of the configuration is deleted. In addition, part of the configuration according to one embodiment can be added to or replaced with the configuration according to another embodiment.

  In addition, each configuration related to the control device 30 and functions and execution processing of each configuration are realized by hardware (for example, logic for executing each function is designed by an integrated circuit). You may do it. Further, the configuration related to the control device 30 may be a program (software) that realizes each function related to the configuration of the control device by being read and executed by an arithmetic processing device (for example, a CPU). Information related to the program can be stored in, for example, a semiconductor memory (flash memory, SSD, etc.), a magnetic storage device (hard disk drive, etc.), a recording medium (magnetic disk, optical disc, etc.), and the like.

  In the above description of each embodiment, the control line and the information line are shown to be understood as necessary for the description of the embodiment, but all the control lines and information lines related to the product are not necessarily included. It does not always indicate. In practice, it can be considered that almost all the components are connected to each other.

    DESCRIPTION OF SYMBOLS 1 ... High pressure turbine (1st turbine), 2 ... Medium pressure turbine (2nd turbine), 3 ... Steam supply pipe (steam supply system), 4 ... Cooling steam flow control valve (control valve), 5 ... Orifice, 6 ... Cooling steam inlet valve, 7 ... generator, 8 ... load detector, 9 ... calculator, 10 ... setting device, 11 ... oscillator, 15 ... manual flow control valve, 21 ... low pressure turbine, 30 ... control device, 100,200 ... Rotor cooling device

Claims (4)

A first turbine;
A second turbine that is separate from the first turbine and is driven by steam that is discharged from the first turbine and heated;
A cooling steam system for supplying extracted steam from the first turbine as cooling steam for the second turbine;
A control valve provided in the cooling steam system for controlling a flow rate of the cooling steam;
A steam turbine equipment comprising: a control device that controls the opening degree of the control valve to be smaller as the turbine load increases after the turbine load reaches the rated load. The steam turbine equipment according to claim 1,
The cooling steam system is further provided with a manual adjustment valve for controlling the flow rate of the cooling steam,
The opening degree of the manual adjustment valve is adjusted according to a change in the required amount of the cooling steam resulting from the aging of at least one of the first turbine and the second turbine. Facility. The steam turbine equipment according to claim 1,
The control device controls the opening degree of the control valve to be smaller as the differential pressure across the control valve increases as the turbine load increases after the turbine load reaches the rated load,
Accordingly, the flow rate of the cooling steam is controlled to increase as the turbine load increases. A first turbine, a second turbine driven by steam discharged from the first turbine and heated, a cooling steam system for supplying extracted steam from the first turbine as cooling steam for the second turbine, In a control method for steam turbine equipment, provided in a cooling steam system, comprising a control valve for controlling the flow rate of the cooling steam,
A method for controlling steam turbine equipment, comprising: a step of continuously reducing the opening of the control valve in accordance with an increase in turbine load after the turbine load reaches a rated load.

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