JPS5944506B2 - Geothermal steam turbine control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a geothermal steam turbine, particularly for a geothermal steam turbine having a two-stage steam/water separator.

The most practical method of power generation using geothermal energy is to generate electricity by directly flowing steam emitted from underground into a turbine, but in this case, effective use of geothermal energy is important.

Generally, steam and hot water are ejected from underground, and only the steam is separated and flowed into the turbine, and the remaining hot water is further sent to a steam separator to produce low-pressure steam. Geothermal energy is effectively utilized by extracting the low-pressure steam and flowing it into an intermediate stage of a turbine.

This type of turbine is called a two-stage flash steam turbine.

Incidentally, the two-stage steam/water separator is provided with a pressure control device in order to supply stable steam to the steam turbine.

However, in the past, this pressure control device was an independent control device unrelated to the turbine, and when the pressure fluctuated greatly due to load fluctuations on the turbine side, or when the ratio of geothermal steam and hot water changed, the energy was reduced. In many cases, some of the geothermal energy had to be wasted because it could not be used effectively.

That is, FIG. 1 is a system diagram of a general two-stage flash type geothermal turbine, in which steam and hot water ejected from a geothermal well 1 are separated into steam and condensate in a first-stage steam-water separator 2. The steam is supplied to the turbine 5 via the high pressure main steam stop valve 3 and the high pressure regulating valve 4.

On the other hand, the drain separated by the first-stage steam-water separator 2 is supplied to the second-stage steam-water separator 7 via a drain water level adjustment valve 6.

The pressure of the second-stage steam-water separator 7 is lower than the pressure of the first-stage steam-water separator 2, so that a part of the condensate flowing into the second-stage steam-water separator 7 evaporates there. This becomes low-pressure steam and is supplied to an intermediate stage of the turbine 5 via a low-pressure main steam stop valve 8 and a low-pressure regulator valve 9.

The steam that has expanded and performed work in the turbine 5 is condensed in a condenser 10 and returned to the ground through a ring well 11.

In this case, a part of the condensate is transferred to the condenser 10 by the pump 1.
2 to the cooling tower 13, where the water is cooled and supplied as cooling water.

Further, the drain separated by the second-stage steam-water separator 7 is returned to the ground by the ring source well 13 via the water level adjustment valve 14.

By the way, the steam pressure of the first-stage steam-water separator 2 is determined by adjusting the opening degree of the first relief valve 15 provided in the steam supply conduit from the first-stage steam-water separator 2 by the pressure detection adjustment device 16. By controlling, a part of the steam is released into the atmosphere, or a part of the high pressure steam is combined with the low pressure steam from the second steam separator 7 via the pressure reducing valve 17. be done.

Similarly, the pressure in the second stage steam separator 7 is controlled by opening and closing a second relief valve 18 provided in the steam supply conduit from the steam separator by means of a pressure sensing and regulating device 19. .

The high pressure regulating valve 4 and the low pressure regulating valve 9 of the turbine 5 are controlled by a speed governor 20 to control their rotation speed and load, and as shown in FIG. The valve opening degree is controlled almost linearly and is controlled independently of the pressure control of the steam/water separator.

In other words, the steam pressure in the steam separator is maintained constant even when the amount of steam inflow to the turbine side changes.
and 18, and on the other hand, the turbine is controlled to open and close the regulating valve according to the load request on the premise of steam at a constant pressure.

Therefore, a certain amount of steam is always being released from both relief valves 15 and 18, and that amount of steam energy is wasted and wasted.

In addition, if there is a sudden change in the load such as turbine load cutoff, the pressure control system will operate after the pressure has increased, so the transient change in pressure will be too large and the turbine Very undesirable.

Furthermore, when the ratio of steam and hot water ejected from underground changes, for example when the amount of high-pressure steam increases and the amount of low-pressure steam decreases, the amount of high-pressure steam released should be increased or It is necessary to manually adjust the pressure reducing valve 17 to allow steam to flow through the low pressure line to use the steam as effectively as possible.

Therefore, in the former case, a large amount of steam is wasted, and in the latter case, it is necessary to manually adjust the pressure reducing valve 17 every time the amount of generated steam changes, resulting in inconveniences such as complicated operation.

In view of these points, an object of the present invention is to provide a geothermal turbine control device that combines steam pressure control of a steam-water separator and a turbine control device to effectively utilize geothermal energy and has good controllability. shall be.

An embodiment of the present invention will be described below with reference to FIGS. 3 and 4.

Note that the same parts as in FIG. 1 are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

In FIG. 3, reference numeral 21 is a control circuit, and this control circuit 21 includes a steam pressure control signal 16a from the pressure detection and adjustment device 16 of the first stage steam separator 2, a steam pressure control signal 16a from the pressure detection adjustment device 16 of the first stage steam water separator 2, Steam pressure control signal 1 from pressure detection adjustment device 19 of 7
9a, and a turbine rotational speed load control signal 20a from the speed governor 20 are respectively applied, and the output signal from the control circuit 21 controls the high pressure regulating valve 4, the low pressure regulating valve 9, the pressure reducing valve 17, and the second stage air/water. The relief valve 18 of the separator 7 is controlled.

The control circuit 21 is constructed as shown in FIG.

In other words, the turbine rotation speed load control signal 20a, which is a control valve opening request signal that amplifies the difference between the turbine rotation speed and the rotation speed setting value and adds the load setting signal after joining the system, is the first The steam pressure control signal 16a is applied to the low value priority circuit 22, and the steam pressure control signal 16a is applied to the first low value priority circuit 22, and the low value signal of both signals is output as a control signal to the high pressure regulating valve 4. Ru.

The output signal from the first low value priority circuit 22 is also applied to a second low value priority circuit 24 via a function 23, and the second low value priority circuit 24 is further supplied with the second stage air water. A sum signal of a steam pressure control signal 19a of the separation device and an output signal of a subtracter 25, which will be described later, is applied, and the low value signal of both signals is outputted as a control signal to the low pressure regulating valve 9.

Further, the steam pressure control signal 16a and the output signal of the first low value priority circuit 22 are combined in a subtracter 25, and the value of the steam pressure control signal 16a is converted to the output signal of the first low value priority circuit 22.
The pressure reducing valve 17 is controlled by a signal obtained by subtracting the value of the output signal from.

Therefore, when the steam pressure control signal 16a is smaller than the rotation speed load control signal 20a, the output of the first low value priority circuit 22 becomes the steam pressure control signal 16a, and the high pressure regulating valve 4 is controlled by the steam pressure control signal. be done.

That is, when the pressure of the fourth stage steam/water separator 2 becomes high, the high pressure regulating valve 4 opens and pressure control is performed.

On the other hand, since both input signals to the subtractor 25 at this time become the steam pressure control signal 16a, the output from the subtractor 25 is 0, and the pressure reducing valve 17 is controlled to be fully closed.

Further, the rotation speed load control signal 20a is the steam pressure control signal 1.
When it is smaller than 6a, the rotation speed load control signal 20a from the first low value priority circuit 22 is output, and the high pressure regulating valve 4 is controlled by this signal, while the subtractor 25 is output by the difference between both signals.
The output increases, the pressure reducing valve 17 is opened by this amount, and the pressure of the first stage steam separator 2 is controlled.

Similarly, the steam pressure control signal 1 of the second stage steam separator 7
9a and the output signal from the subtractor 25, and a signal with a lower force among the signals passed through the function from the rotational speed load control signal 20a, the low pressure regulating valve 9 is controlled. The output signal from the circuit 24 and the sum signal of the steam pressure control signal 19a and the output signal from the subtracter 25 are subtracted by the subtracter 26, and the difference signal is used to control the second relief of the second stage steam/water separator 7. Control of valve 18 is performed.

In this way, since the output signal from the subtracter 25 is added to the steam pressure control signal 19a by the adder 27, when the pressure reducing valve 17 opens, the output signal from the steam line of the first stage steam separator 2 to the second The steam flow rate flowing into the steam line of the stage steam/water separator 7 is added in advance as a control signal to the steam pressure control signal of the second stage steam/water separator, thereby improving the transient characteristics.

Since the present invention is configured as described above, first, before starting the turbine, the rotation speed load control signal 20a is 0, so that both the high pressure regulating valve 4 and the low pressure regulating valve 9 are fully open.

Further, the pressure reducing valve 17 is opened by the steam pressure control signal 16a of the first stage steam water separator 2, and pressure control is performed by releasing steam to the second stage steam water separator line. The steam generated in the steam separator 7 and the steam flowing in through the pressure reducing valve 17 are released from the second relief valve 18, and the steam pressure in the second stage steam separator 7 is controlled.

From this state, the turbine is started, and in the process of increasing the rotation speed and taking on the load, the rotation speed load control signal 20a gradually increases, and the first low value priority circuit 22 and the second low value priority circuit 24 An opening signal is applied to the high pressure regulating valve 4 and the low pressure regulating valve 9, respectively, and both regulating valves 4 and 9 are opened.

At this point, the two low value priority circuits are prioritized by the signal from the rotational speed load control signal 20a, and when this signal opens the high pressure regulating valve 4 and the low pressure regulating valve 9 as described above,
The flow rate of steam flowing from the steam line of the first-stage steam-water separator 2 to the steam line of the second-stage steam-water separator or from the second-stage steam-water separator to the atmosphere can be reduced. When the outflow flow rate increases and the pressure of the solid-gas/water separator decreases, the opening degrees of the pressure reducing valve 17 and the second relief valve 18 are operated in the closing direction only by the steam pressure control signal. , 9 are applied to the subtractors 25 and 26, the output signals from both subtractors 25 and 26 cause the pressure reducing valve 1 to
7 and the second relief valve 18 are controlled in the closing direction, ie both valves are controlled by the speed load control signal 20a prior to pressure control, so that the occurrence of transient deviations is kept to a minimum.

For pressure control of the second-stage steam-water separator 7, in addition to steam flowing into the turbine from the low-pressure regulating valve 9, steam flowing from the steam line of the first-stage steam-water separator via the pressure-reducing valve 1γ is used. The upcoming change in the amount of steam also becomes a disturbance factor, but this signal is also
7 as a preliminary control signal, transient deviations caused by this are also prevented.

By the way, as the turbine load increases, the amount of steam flowing into the turbine increases, and the pressure reducing valve 17 and the second relief valve 1
8 decreases, and eventually the pressure reducing valve 17 and the second relief valve 18 are fully closed, and all the steam generated in the solid-air water separator begins to flow into the turbine.

At this time, the steam pressure control signals 16a and 19a have lower values than the rotational speed/negative MIJ control signal 20a, and both the steam pressure control signals have passed through the first low value priority circuit 22 and the second low value priority circuit 24. Both the high pressure and low pressure regulating valves 4 and 9 are respectively controlled by the above.

In this way, the system is controlled in this state during normal operation, and geothermal steam is effectively utilized.

- If the ratio of geothermally generated steam and hot water changes significantly during this normal operation, for example, the amount of steam increases and the steam in the first stage steam water separator 2 increases, and the second stage steam water separator 7 When the steam in The control valve 4 is controlled by the rotation speed/load control signal.

On the other hand, the pressure reducing valve 17 is controlled in the opening direction by the output signal from the subtractor 25, the pressure of the first stage steam separator 2 is controlled, and the steam passing through the pressure reducing valve 17 is transferred to the second stage steam water separator 2. Together with the steam from the separator 7, it flows into the turbine via the low pressure regulating valve 9.

In this case, the pressure in the second stage steam separator 7 is also affected by the steam flowing through the pressure reducing valve 17, but since the pressure reducing valve opening signal is added to the steam pressure control signal 19a as a preceding signal, the pressure reducing valve The low pressure regulating valve 9 and the second relief valve 18 are controlled together with the opening operation, thereby preventing excessive deviation from occurring.

Conversely, the proportion of hot water increases, the steam in the second stage steam-water separator 7 increases, and the request signal of the steam pressure control signal 19a changes to the function 2.
3, the low pressure regulating valve 9 is controlled by the rotation speed/load control signal, and the second relief valve 18 is opened by the steam pressure control signal 19a passed through the subtractor 26. and unnecessary steam is released.

Furthermore, if a situation occurs during normal operation in which the rotational speed abnormally increases due to turbine load cutoff or large load fluctuation, both the control valves 4 and 9 are controlled in the closing direction by the rotational speed/load control signal 20a. At the same time, the signal opens the pressure reducing valve 17 and the second relief valve 18 to perform pressure control.

As explained above, in the present invention, the first stage steam separator outputs the high pressure regulating valve control signal based on the low value signal of the pressure control signal of the first stage steam/water separator and the turbine speed/load control signal.
a low value priority circuit, a pressure reducing valve control device that controls a pressure reducing valve based on the difference between the pressure control signal of the first stage steam water separator and the output signal from the low value priority circuit, and a second stage steam water separator. a second low value priority circuit that outputs a low pressure regulating valve control signal based on a low value signal of the pressure control signal of the container and a low pressure regulating valve opening request signal from the first low value priority circuit; A relief valve opening control device is provided to control the relief valve of the second stage steam/water separator based on the difference between the pressure control signal of the separator and the output from the second low value priority circuit. Effectively combined with pressure control, even when the ratio of steam and hot water ejected from underground changes or when load is cut off, the pressure reducing valve can be manually adjusted each time, or a large amount of steam can be wasted. Geothermal steam can be used effectively without being released into the atmosphere, and stable control can always be performed without excessive control deviations.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a conventional geothermal steam turbine control device, Fig. 2 is a relationship diagram between the opening degree of the control valve and the rotation speed/load control signal, and Fig. 3 is a geothermal steam turbine control device of the present invention. FIG. 4 is a detailed system diagram of the control circuit. 1... Geothermal well, 2... First stage steam water separator, 4... High pressure regulating valve, 5... Turbine, 7...・・Second stage steam separator, 9・・・・
・Low pressure regulating valve, 15...First relief valve, 16.
... Pressure detection adjustment device, 17 ... Pressure reducing valve, 18 ... Second relief valve, 21 ... Control circuit, 22 ... first low value priority circuit, 24.
...Second low value priority circuit.

Claims (1)

[Scope of Claims] 1. A first low-value priority circuit that outputs a high-pressure regulating valve control signal based on a low-value signal of the pressure control signal of the first stage steam-water separator and the turbine speed/load control signal; A pressure reducing valve control device that controls a pressure reducing valve based on the difference between the pressure control signal of the first stage steam water separator and the output signal from the low value priority circuit; A second low value priority circuit outputs a low pressure regulating valve control signal based on a low value signal that is combined with a low pressure regulating valve opening request signal from the value priority circuit; A geothermal steam turbine control device comprising: a relief valve opening control device that controls a relief valve of a second stage steam/water separator based on a difference between the output signal and the output signal from the low value priority circuit. 2. The geothermal steam turbine control device according to claim 1, wherein a relief valve control signal is added as a preliminary control signal to the pressure control signal of the second stage steam/water separator.