JP3672587B2 - Auxiliary steam supply system for combined cycle power plant - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an auxiliary steam supply device for a combined cycle power plant in which a plurality of power generation shafts in which gas turbines, exhaust heat recovery boilers, and steam turbines are combined are installed.
[0002]
[Prior art]
At the start of the combined cycle power plant, degassing steam and ground seal steam for the steam turbine are required. Before sufficient steam is supplied from the exhaust heat recovery boiler, auxiliary steam for this purpose must be added. It is necessary to supply from the facility.
[0003]
When any shaft of a multi-shaft combined cycle power plant is operating, the auxiliary steam required when starting the other shaft is supplied from the operating shaft.
FIG. 5 shows an example of such a conventional auxiliary steam supply method, and shows a case of a four-shaft combined cycle power plant for the sake of simplicity.
[0004]
In FIG. 5, the A-axis 1 of the combined cycle power plant is started as follows. That is, an auxiliary boiler 3 is connected to the auxiliary steam pipe 2, and at the time of start-up, the inflow valve 4A is opened to supply auxiliary steam from the auxiliary boiler 3, and this is degassed steam and the ground of the steam turbine 9 The gas turbine 5 is activated using steam.
[0005]
The exhaust gas from the gas turbine 5 enters the exhaust heat recovery boiler 6 and heats the feed water sent from the condenser 7 by the feed water pump 8 to generate steam, which drives the high-pressure steam turbine 9. The exhaust steam from the high-pressure steam turbine 9 (which is called low-temperature reheated steam) enters the exhaust heat recovery boiler 6 and is reheated, and then drives the low-pressure steam turbine 10. The generator 11 is driven by a gas turbine 5, a high pressure steam turbine 9, and a low pressure steam turbine 10 to generate electric power.
[0006]
When the output of the gas turbine 5 increases, the amount of generated steam also increases, and auxiliary steam is no longer necessary, so the inflow valve 4A is closed. As the amount of generated steam further increases, the pressure of the low-temperature reheated steam increases and the pressure at the inlet of the outflow valve 12A increases. The detector 14A detects the pressure here, and when it reaches a predetermined pressure, determines that steam supply to the other shaft is possible (this state is called supply steam possible), and opens the outflow valve 12A. The check valve 13A is also opened by the pressure to supply auxiliary steam (hereinafter referred to as supply steam) to the auxiliary steam pipe 2. The shaft providing the supply steam is called the supply shaft.
[0007]
In this way, when one shaft of the combined cycle power plant is operated and starts to supply steam, the auxiliary boiler 3 is stopped.
When starting the B-axis 15, C-axis 16, and D-axis 17 of the combined cycle power plant, start using the supply steam from the A-axis 1, and the other shafts will similarly turn on the inflow valve 4 as the output increases. After the closing operation, supply steam is provided through the outflow valve 12 and the check valve 13 to serve as a supply shaft. A communication pipe 18 is connected to the auxiliary steam pipe 2, and steam is supplied to the utility equipment 19. For this reason, it is necessary to provide supply steam to the auxiliary steam pipe 2 even when all the inflow valves 4 are closed (that is, even when there is no combined cycle power plant that consumes auxiliary steam).
[0008]
Thereafter, when the A shaft 1 is stopped, the outflow valve 12A is closed and the inflow valve 4A is opened to secure auxiliary steam using steam supplied from another shaft during operation of the combined cycle power plant, and then the gas turbine. Bin 5, high-pressure steam turbine bin 9 and low-pressure steam turbine bin 10 are stopped.
[0009]
[Problems to be solved by the invention]
However, the conventional auxiliary steam method has the disadvantage that the check valve 13 is constantly opened and closed, the auxiliary steam pressure becomes unstable, and the check valve is damaged. More specifically, when the pressure in the auxiliary steam pipe 2 becomes higher than the exhaust steam pressure in the high-pressure steam turbine 9, the check valve 13 is closed, so that the steam in the auxiliary steam pipe 2 passes through the outflow valve 12. The backflow phenomenon that flows into the A-axis 1 is prevented. However, adjacent shafts such as the A-axis 1 outflow valve 12A and the B-axis 14 outflow valve 12B are easily affected by the pressure on the other side. For example, the outlet pressure of the A-axis 1 outflow valve 12A is unstable and hunting occurs. If this occurs, the effect appears at the outlet of the check valve 13B of the B-shaft 14, so that the check valve 13B repeats opening and closing.
[0010]
In addition, when all the inflow valves 4 are fully closed and only the utility equipment 19 consumes auxiliary steam, the amount of steam consumed by the utility equipment 19 is very small. When supplied, the relatively small amount is further divided into four parts, the amount of steam flowing through the check valve 13 is reduced, the differential pressure at the inlet and outlet of the check valve 13 is reduced, and the check valve 13 opens and closes. It will be repeated. All of these disadvantages are caused by the fact that multiple shafts provide the supply steam.
[0011]
[Means for Solving the Problems]
The present invention is a plurality of auxiliary steam supply devices that comprehensively determine the opening / closing of the outflow valve of each shaft and perform control , and each of which includes a gas turbine, a steam turbine, a generator, and an exhaust heat recovery boiler as main components. The low-temperature reheat steam of each steam turbine of the combined cycle power plant consisting of multiple power generation shafts is connected to the common auxiliary steam mother pipe through the respective outflow valve and check valve, and the auxiliary steam mother pipe is connected between the respective power generation shafts. In the auxiliary steam supply device of the combined cycle power plant that supplies auxiliary steam through, a determination means is provided for determining whether or not the power generation shaft can supply auxiliary steam using the pressure of the low-temperature reheated steam. An auxiliary steam supply device is provided.
[0012]
[Action]
In this auxiliary steam supply device, as a preferred example, the first shaft that has reached the state where supply steam can be supplied is selected as the supply shaft among the shafts that can supply steam, and only the outlet valve and the check valve of the shaft are selected. It is possible to set it to open. In addition, when it is detected that the power generation shaft selected as the auxiliary steam supply shaft is in an emergency stop due to an accident or the like and the supply steam capacity is lost, the supply shaft that promptly selects the other shaft as the supply shaft is switched. It is conceivable to set to
As described above, in the present invention, since only one shaft is selected as the supply shaft, unstable operation of the check valve due to pressure mutual interference between the shafts and excessive auxiliary steam consumption is avoided and stable. Auxiliary steam can be supplied. Even when the supply axis stops due to an emergency accident, the auxiliary steam source is not lost because the other axis is switched quickly as the supply axis.
[0013]
【Example】
An embodiment of the present invention is shown in FIG. In FIG. 1, the auxiliary steam supply device 20 opens and closes the outflow valve 12 of each shaft. A signal from the detector 14A and a signal from the detector 21A for detecting the fully opened state of the outflow valve 12A are input to the auxiliary steam supply device 20. Although not shown in FIG. 1, similar signals are input to the B-axis 15, the C-axis 16, and the D-axis 17.
[0014]
An example of a control circuit configured inside the auxiliary steam supply device 20 is shown in FIGS. This control circuit operates so as to select the shaft that first reaches a state where steam can be supplied from among the shafts capable of supplying steam as the supply shaft, and to open the outflow valve 12 thereof. When the supply axis is in an emergency stop, the A axis is selected as the highest priority among the axes capable of supplying steam. When the A axis is not in a state where supply steam is possible, the B axis, C axis, and D axis are sequentially selected. In this order, only one supply shaft is selected, the outflow valve 12 of that shaft is opened, and the outflow valve of the emergency stop shaft is closed.
[0015]
In FIG. 2, the judgment circuit 22 is supplied with the inlet pressure of the outflow valve 12 from the detectors 14A, 14B, 14C, 14D, and the comparator 23A has a pressure signal of the detector 14A exceeding a predetermined value. At this time, the A-axis supply enable signal 1a is output. The comparators 23B, 23C and 23D work in the same way.
[0016]
The A-axis supply enable signal 1a output from the determination circuit 22 is input to the first-arrival priority circuit 24. When the B-axis selection signal 3b, the C-axis selection signal 3c, and the D-axis selection signal 3d are not selected, the A-axis first arrival signal. First-come-first-served selection for outputting 2a is performed. The same applies to the B-axis, C-axis, and D-axis, and the B-axis first signal 2b, the C-axis first signal 2c, and the D-axis first signal 2d are output. These signals are input to a single axis selection circuit 25, where priority selection is performed in the order of A axis, B axis, C axis, and D axis. As a result, A axis selection signal 3a, B axis selection signal 3b, C axis selection signal 3c, Only one of the D-axis selection signals 3d is output.
[0017]
In FIG. 3, the outflow valve opening / closing circuit 26 receives the A axis selection signal 3a, the B axis selection signal 3b, the C axis selection signal 3c, and the D axis selection signal 3d from the single axis selection circuit 25, and the A axis selection signal 3a If established, an outflow valve 12A opening command 4a for opening the outflow valve 12A is output. The outflow valve opening / closing circuit 26 receives the signals of the detectors 21A, 21B, 21C and 21D, and generates the respective outflow valve fully open signals 5a, 5b, 5c and 5d. When the A-axis selection signal 3a is not established, it is confirmed that any of the outflow valve full-open signals 5b, 5c, 5d of the other shafts other than the A-axis is established, and then the outflow valve 12A close command 6a is output. . The B-axis, C-axis, and D-axis have the same circuit as the A-axis. First, it will be described in detail how the first-come-first-served function in which the first shaft that has reached the state where the supply steam can be supplied is selected as the supply shaft is realized by the determination circuit 22, the first-priority priority circuit 24, and the one-axis selection circuit 25.
[0018]
When the C-axis is first activated as the preceding axis and the low-temperature reheat steam pressure reaches a predetermined value, the determination circuit 22 determines that the C-axis can be supplied with the comparator 23C and supplies the C-axis. The enable signal 1c is output.
[0019]
The C-axis supply enable signal 1c is input to the first priority circuit 24. Since the axes other than the C axis are not yet ready for supply steam, the A axis supply enable signal 1a, the B axis supply enable signal 1b, and the D axis supply enable signal 1d are not established. The A-axis selection signal 3a, the B-axis selection signal 3b, and the D-axis selection signal 3d are not established. Therefore, in the first priority circuit 24, the C-axis first signal 2c is established, and the other A-axis first signal 2a, B-axis first signal 2b, and D-axis first signal 2d are not established. The C-axis first arrival signal 2c is input to the one-axis selection circuit 25. In the one-axis selection circuit 25, the A-axis and B-axis input signals having priority over the C-axis, that is, the A-axis first arrival signal 2a and the B-axis first arrival signal 2b are not established, and therefore the C-axis selection signal 3c is established.
[0020]
Since the C-axis selection signal 3c is established in the first-arrival priority circuit 24, the A-axis first-arrival signal 3a, the B-axis first-arrival signal 3b, and the D-axis first-arrival signal 3d are, for example, the A-axis supply enable signal 1a and the B-axis supply enable signal. Even if the 1b, D-axis supply enable signal 1d is established later, it is not established.
[0021]
In other words, after the C-axis is allowed to supply steam, the first priority circuit 24 that eliminates the supply-steam can be supplied even if the succeeding axis becomes possible to supply steam. There is no inconvenience that the supply axis is switched.
[0022]
Next, when the supply shaft is brought to an emergency stop and the supply steam capacity is lost, one of the remaining three axes is selected and the one-axis selection function to become the next supply axis is performed by the determination circuit 22 and the first priority circuit 24. How it is realized with the single axis selection circuit 25 will be described in detail.
[0023]
After the C-axis selection signal 3c is established, the supply of the A-axis, B-axis, and D-axis becomes possible, and the A-axis supply enable signal 1a, the B-axis supply enable signal 1b, and the D-axis supply enable signal 1d are established. To do. When the C-axis emergency stop from this state, the low temperature reheat steam disappears, so the detector 14C detects the loss of pressure, and the comparator 23C in the judgment circuit 22 outputs the C-axis supply enable signal 1c. Not established. When the C-axis supplyable 1c is not established, the C-axis first arrival 2c that is the output of the first-priority priority circuit 24 is not established, and as a result, the C-axis selection signal 3c that is the output of the one-axis selection circuit 25 is also not established. In the instantaneous first-arrival priority circuit 24, an A-axis first-arrival signal 2a, a B-axis first-arrival signal 2b, and a D-axis first-arrival signal 2d are established and are input to the one-axis selection circuit 25, respectively.
[0024]
In the single axis selection circuit 25, priority selection works in the order of the A axis, B axis, and D axis, so only the A axis selection signal 3a is established, and the B axis selection signal 3b and D axis selection signal 3d are not established. It is. As described above, when the supply shaft is stopped urgently, it is possible to realize a single axis selection function for quickly selecting the next supply shaft from a plurality of supply steam capable shafts.
[0025]
Next, the operation of the outflow valve opening / closing circuit 26 will be described. If the C-axis is urgently stopped in the above process, the C-axis selection signal 3c is not established and the A-axis selection signal 3a is established and input to the outflow valve opening / closing circuit 26. When the A-axis selection signal 3a is established, an A-axis outflow valve 12A open command 4a is output, the outflow valve 12A is opened, the check valve 13A is also opened by the pressure, and the A-axis becomes the supply shaft. Since the C-axis selection signal 3c is not established, the C-axis outflow valve 12C operates so that the outflow valve 12C close command 6c is output.
[0026]
However, the opening operation of the outflow valve 12A takes time, and the operation of closing the C-axis outflow valve 12C is permitted, that is, the outflow valve 12C close command 6c so that the steam does not run out until the outflow valve 12A is fully opened. Is output after the fully open signal 5a of the A-axis outflow valve 12A is established. During this time, steam is supplied until the A-axis outflow valve 12A is fully opened using the residual steam retained in the C-axis piping.
[0027]
In this way, an auxiliary steam control device is provided in which only one shaft provides supply steam at all times so that the supply steam is not interrupted even when the supply shaft is switched.
As described above, according to this embodiment, since the determination circuit 22 is provided, it is possible to accurately determine a situation in which the supply capability is lost due to an emergency accident stop or the like, and to switch the supply axis. In addition, since the first-priority priority circuit 24 is provided, only the axis that is activated first is the supply axis, and the outflow valve 12 and the check valve 13 are opened, so that each time the subsequent axis can be supplied, the supply axis Therefore, the auxiliary steam can be supplied stably.
[0028]
Furthermore, since the single axis selection circuit 25 is provided, the next supply axis can be selected promptly even if the supply axis stops in an emergency, so the supply axis can be switched without losing the supply steam source. It is. In addition, an outflow valve opening / closing circuit 26 is provided to open and close the outflow valve. The closing operation is performed after confirming the fully open condition of the outflow valve of the other shaft. It is possible to avoid running out of supply steam.
[0029]
Another embodiment according to the present invention is shown in FIG. In this embodiment, an A-axis exclusion switch 27A is provided in the supply enable detection circuit 22, and the A-axis supply enable signal 1a is manually disabled by operating this switch. Similarly, supply exclusion switches 27B, 27C, and 27D are provided for the B, C, and D axes.
[0030]
In this way, when it is known that the operation of the A axis is to be stopped in advance, the A axis can be stopped after the supply axis is switched by operating the A axis exclusion switch 27A.
[0031]
As an advantage of this embodiment, since the switching is performed in a state where the A-axis can be supplied, it is possible to reliably supply auxiliary steam with less possibility of steam breakage at the time of switching.
[0032]
【The invention's effect】
As described above, according to the present invention, only one shaft is selected as the auxiliary steam supply shaft by the auxiliary steam supply device, so there is no inconvenience such as pressure interference with the other shaft.
[0033]
Further, even when the auxiliary steam supply shaft is urgently stopped, the next auxiliary steam supply shaft is selected quickly, so that the auxiliary steam supply is not lost and stable supply of the auxiliary steam can be achieved.
[Brief description of the drawings]
FIG. 1 is a configuration diagram in which an auxiliary steam supply device of the present invention is applied to a combined cycle power plant. FIG. 2 is a block configuration diagram showing an embodiment of the present invention. FIG. 4 is a block diagram showing another embodiment of the present invention. FIG. 5 is a block diagram showing a conventional example.
20 Auxiliary steam supply device
21 Detector
22 Judgment circuit
23 Comparator
24 First priority circuit
25 Single axis selection circuit
26 Outflow valve switching circuit
27 Exclusion switch

Claims (5)

The low-temperature reheat steam of each steam turbine of a combined cycle power plant consisting of a plurality of power generation shafts each consisting mainly of a gas turbine, a steam turbine, a generator, and an exhaust heat recovery boiler passes through respective outflow valves and check valves. Whether or not the power generation shaft can supply auxiliary steam in an auxiliary steam supply device of a combined cycle power plant that is connected to a common auxiliary steam mother pipe and supplies auxiliary steam through the auxiliary steam mother pipe between the power generation shafts. The auxiliary steam supply device is provided with a determination means for determining the temperature using the pressure of the low-temperature reheated steam.   A first-priority priority circuit is provided to select only the power generation shaft for which auxiliary steam can be supplied at the very beginning. The auxiliary steam supply device according to claim 1, wherein the valve and the check valve cannot be opened. When the determination means detects that the supply of auxiliary steam on the operating power generation shaft is no longer possible, closes the outflow valve and check valve of the power generation shaft and selects only one of the other power generation shafts. auxiliary steam supply device according to claim 1, characterized in that a single selection circuit for selecting as opening the outlet valve and the check valve of the power shaft Te. According to claim 3, characterized in that a detecting means for detecting that one of the outlet valve of said selected signal as that closes the outlet valve from the uniaxial selection circuit and another power shaft is open auxiliary steam supply device. The judgment unit may, auxiliary steam supply device according to any one of claims 1, characterized in that a switch circuit for switching the power shaft for supplying auxiliary steam 4.

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