JPS58148205A - Controller of geothermal steam turbine - Google Patents

Abstract

PURPOSE:To smoothly control operation of a turbine, by correcting a load change at the beginning of supply of low pressure steam after two-stage flushing with an opening of a high pressure steam governing valve in accordance with an opening of a low pressure steam stop valve. CONSTITUTION:Steam jetted from a well 1 is separated to steam and hot water by a drain separator 2, and the steam is supplied to a high pressure stage of a turbine 5 while the hot water is converted into flush steam by a flush tank 6 and supplied to a low pressure stage. An opening of a low pressure steam stop valve 7 is detected by an opening detector 48, in accordance with its opening signal, a valve closing signal by the amount equal to inflow energy to the steam turbine due to leaked steam of a low pressure steam governing valve 8 in accordance with the opening of the valve 7 is applied to an adder 23 through a correction circuit consisting of a demodulator 49 or the like, in accordance with the signal of the adder, a high pressure steam governing valve 4 is controlled in the closing direction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a control device for a geothermal steam turbine in a geothermal power generation plant using 2R flash steam that effectively utilizes geothermal energy.

[Technical Background of the Invention and Points of Interest] Generally, in a geothermal power generation plant, steam ejected from underground is separated into hot water and steam by a drain-k/< rotor, and only the steam is sent to a steam turbine. However, the 0 I am using is
Since a large amount of the above-mentioned hot water is generated, returning the hot water directly to the ground will reduce the efficiency of the power generation plant. In the case of geothermal turbines, however, the water vapor pressure is around 10 to 9/dig. , the flushed vapor pressure is at most 2 to 3 KI/a.
IR ◎ Therefore, 1 In order to construct an economically advantageous power plant, it is necessary to let a large amount of steam flow into the steam turbine. If a spherical steam control valve is used as in conventional thermal power plants, there are limitations in the structure of the valve, and the throttling loss of the valve is large, reducing the efficiency of the plant. To solve this problem, butterfly valves are currently used in most of the steam control valves of geothermal turbines.By the way, there are various types of butterfly valves, but in the case of butterfly valves used in geothermal turbines, h steam temperature is about 170 to 190°C, and it is necessary to take into account elongation due to temperature differences.In other words, if a certain degree of distance is not provided between the valve body and the valve seat, the valve body will elongate due to temperature. The valve body may still not move when it is fully closed. Although this determination varies depending on the materials of the valve body and the valve seat, a gap of about 0.5 to 1.5 fi is normally required between the valve body and the valve seat. Moreover, this gap tends to increase in proportion to the size of the valve aperture.

As the valve diameter increases, the annular area due to the gap increases,
When steam pressure is applied to the primary part of the butterfly valve, the amount of steam leaking from this gap becomes extremely large.Because it is necessary to control the large amount of steam, this butterfly valve is generally used in power generation plants. Since eight butterfly valves are used, the amount of steam leaking from the butterfly valves when the butterfly valves are fully closed reaches 2 to 5 times the amount of steam flowing into the entire steam turbine. Although there is not enough steam to increase the speed of the steam turbine to the rated speed, it is sufficient to increase the speed to a certain speed. A spherical valve with no steam leakage is used as the main steam stop valve.By the way, when a spherical valve is used as the main steam stop valve, when the valve is used to start the turbine, the steam pressure Since the unbalanced force is large, it is necessary to make the drive device very large, and speed increase control at the time of starting the turbine with a diameter of 90 mm poses a problem in controllability. Therefore, the above-mentioned spherical valve has a built-in small valve that can be opened and closed by the same drive device, and the small valve trap controls the speed increase when starting the turbine.On the other hand, in the case of the 21j IL7 Lassie turbine, , as mentioned above, 2 ml of steam having different pressures will flow into the steam turbine. That is, high-pressure steam is supplied to the steam turbine at high pressure [IC] through a high-pressure main steam stop valve and a high-pressure steam control valve, and low-pressure steam is supplied to an intermediate stage of the steam turbine via a low-pressure steam stop valve and a low-pressure steam control valve. 0 Also in this case, butterfly valves are used for both the high pressure steam regulating valve and the partial pressure steam regulating valve for the reasons mentioned above. Since there is a possibility of steam leakage, it is necessary to use a spherical valve for the low pressure steam stop valve as in the case of the one-stage flash. In order to prevent steam leakage from the low-pressure steam control valve from being affected by the turbine rotation speed or output control, the low-pressure steam stop valve also has a valve opening position control valve in its oil cylinder. [Objective of the Invention] The present invention solves these problems. It is an object of the present invention to provide a control device for a geothermal steam turbine that allows easy control without impairing the speed controllability or output controllability of the steam turbine. - [Supplying high-pressure steam to the high-pressure stage of the turbine through the pressure steam stop valve and high-pressure steam control valve, and supplying low-pressure steam to the low-pressure stage through the low-pressure steam stop valve and the low-pressure steam control valve A geothermal steam turbine control device configured to include an opening detection device for detecting the opening of a low-pressure steam stop valve, and an adder for adding a detection signal from the opening detection device to a control signal for the high-pressure steam control valve. to compensate for fluctuations in the turbine rotational speed or load due to leakage steam from the low-pressure steam control valve when the low-pressure steam stop valve is operated in the opening direction.
It is assumed that the detection signal from the detection device is used to correct the valve opening signal of the high pressure steam control valve in the direction of decreasing it.

[Example of invention of koji]

FIG. 1 is a system diagram of a geothermal steam turbine control system according to the present invention. Steam ejected from a well 1 is separated into steam and hot water by a drain separator 2, and the steam is transferred to a high-pressure steam stop valve 3t? Then, the amount of steam f flowing into the steam turbine is supplied to the high pressure stage of the steam turbine 5 through a high pressure steam control valve 4 consisting of a butterfly valve t which adjusts and controls the output and rotational speed of the turbine. . The hot water separated by the drain separator 2 is led to the flash tank 6, where the generated steam passes through the low-pressure steam stop valve 7 and the low-pressure steam control valve 8, which is the butterfly valve, to the turbine 5. Supplied to the low pressure stage. The steam supplied to the steam turbine 5 performs work therein and drives the generator 9, and the exhaust gas from the steam turbine 5 flows into condensate @ 101c where it is condensed.

On the other hand, a gear 12 is directly connected to the rotor shaft 11 of the steam turbine 5, and a non-contact electromagnetic pickup 13 is disposed opposite to the gear 12. This allows nine frequency signals to be detected.

The t signal detected by the pickup 13 is converted into an analog quantity proportional to the turbine rotation speed by a frequency-voltage converter 144C, and is converted into an analog quantity by an adder 15 and a differentiator 16.
are applied to each.

In the adder 15, the rotational speed signal from the frequency-voltage converter 14 is compared with the setting signal from the speed setter 17, and the error signal is added to the low value priority circuit 18.

- the t speed signal applied to the machine divider 16 is applied to the differentiator 16;
The acceleration signal is differentiated by and becomes an acceleration signal, and this acceleration signal is compared with the setting signal from the acceleration setting device 19 by an adder.
The error signal is integrated by an integrator to form a speed error signal and is applied to the low value priority circuit 18.

The speed error signal, which is the output of the low value priority circuit 18, is turned into a nine-speed control signal that matches the speed adjustment rate by the speed adjustment rate circuit η, and is compared with the setting signal from the load setting device by the adder. The valve once command signal from the adder 1623 is applied to the arithmetic circuit δ and the low value priority circuit 26, respectively.The output signals of the 0 arithmetic circuit 25t, etc. are compared with the bias signal from the pipe setting #lI28 in the adder, and the power amplifier After the power is amplified in step 4, it is input to the electro-hydraulic converter Zenmi, where it is converted into an arm-like deviation proportional to the input current, and the deviation drives the hydraulic servo motor 31 of the high-pressure steam stop valve 3. The hydraulic servo motor 31 controls the opening and closing of the high pressure steam stop valve 3.

It, the valve opening command signal from the adder WI is compared with the limit signal from the load limiter 6 in the low value priority circuit, and its output is input to the adder Saa and compared with the bias signal from the bias setter 28. be done. The bias setting-4 is operated by the operation circuit word and generates a predetermined bias setting signal for controlling full-circle injection/partial injection retraction, and during full-circle injection operation, 6C is When performing a partial injection operation in which a bias signal is applied to the adder to fully open the high pressure steam control valve 4t, and the bias signal to the other adder becomes zero, the bias signal to the adder should be The bias signal is zero, and a bias signal that causes the high pressure steam stop valve 3 to be fully opened is added to the adder 27.

After the output signal from the adder Okara is amplified by the power amplifier, it is converted into a mechanical deviation amount by an electro-hydraulic converter%, and the predominant amount is used to control the hydraulic pressure of the high-pressure steam control valve 4. The servo motor is operated, thereby opening and closing the -pressure steam control valve 4, controlling the amount of steam flowing into the steam turbine, and controlling the rotational speed of the steam turbine.

That is, when performing full-circle injection operation such as when starting a turbine, the bias signal to the adder 4 is zero, and the valve opening command signal from the adder passes through the calculation circuit δ, etc. The command signal is transmitted to the high pressure steam stop valve 3, and the opening degree of the high pressure steam stop valve 3 is controlled by the command signal. On the other hand, at this time, since a bias signal for fully opening the high pressure steam control valve 4 is added to the addition Ig signal, the high pressure steam control valve 4 is fully open.

In addition, when performing partial injection operation such as during overcurrent operation of the turbine, the bias setting unit is switched, so contrary to the above, the high pressure steam stop valve 3 is fully opened and the high pressure steam control valve is closed once. The opening is controlled by the command signal.The output from the low value priority circuit 3 is also applied between the adders, where it is compared with the bias signal from the bias setting @39, and the power is amplified by the power amplifier Kiku. Electricity
The current is input to the hydraulic converter 41 and converted into a pressure proportional to the input current, and the opening degree of the low pressure steam control valve 8 is controlled via the hydraulic servo motor 42. That is, in the two-stage flash turbine, as mentioned above, the 1st stage 7 Lassie steam with high steam pressure flows into the high pressure stage of the steam turbine, and the 21! I-flushier steam is mixed in from the middle stage of the steam turbine. When starting a steam turbine, it is not necessary to use the two types of steam mentioned above, and the steam turbine can be started using only high-pressure steam. Therefore, depending on the bias signal from the bias setting device 39, the low pressure steam control valve 8 does not start opening at the same time as the full-circle injection operation 4, but opens after the high pressure steam control valve 4 has opened to a certain extent.

On the other hand, the output signal from the low value priority circuit is detected by a signal detector, and this detection signal is transmitted to a solenoid valve 45 via a relay circuit 44, and a pilot valve 46 is actuated via this solenoid valve 45. and its pilot valve 4
6, the hydraulic servo motor 47 of the low pressure steam stop valve 7 is operated to open the low pressure steam stop valve 7. Also, the hydraulic servo motor 47 is equipped with an opening detection device for the low pressure steam stop valve 7. The detection signal from the opening detection device 48 is converted into an analog tK proportional to the valve opening by a demodulator 49, and then by a converter 50,
The signal closes the high-pressure steam control valve 4 by an amount equal to the energy flowing into the steam turbine 5 due to the leakage steam of the low-pressure steam control valve 8, which corresponds to the opening degree of the low-pressure steam stop valve. The output signal is applied to adder δ.

As mentioned above, the high-pressure steam stop valve 3 begins to open when the turbine 5 is started and fully opens when the full-circumference injection mode shifts to partial injection operation, but the low-pressure steam stop valve 7 is operated by the hydraulic servo motor 47. It's fully closed and
When the operating state is stabilized after shifting from full-circle injection operation to partial injection operation and reaches the t state, it first receives an output signal from the low value priority circuit.

The low pressure steam stop valve 7 is opened via a signal detector L, a relay, etc., and then, depending on the setting value of the bias setting device, the low pressure steam is controlled with a delay of L after the opening operation of the low pressure steam stop valve 7. The valve 8 begins to open. Therefore, even when the low pressure steam control valve 8 is fully closed, the low pressure steam stop valve 7 is fully opened.However, as mentioned above, the Kt pressure steam control valve 8 (70 Lie valve is used, and due to its structure, there is a certain amount of steam leakage even when it is fully closed. Therefore, when the low pressure steam stop valve 7 starts to open, the leakage increases almost in proportion to the degree of opening.) - Turbine output tends to increase due to air.

However, the opening degree of the low-pressure steam stop valve 7 is detected by the opening control device 4sK, and in response to the opening degree signal, the opening degree of the low-pressure steam stop valve 7 is determined through a correction circuit including a demodulator 49 and the like. Since a valve closing amount corresponding to the amount of energy flowing into the steam turbine due to leakage steam from the low-pressure steam control valve is applied to the adder, the high-pressure steam control valve 4 is closed in response to that signal. It is controlled in the closing direction, and an increase in turbine output due to the leaked steam is prevented.

Figure 2 shows the movement of each valve during the startup process of this control device.
show. ! In FIG. I2, before starting the turbine, the high pressure steam control valve 4 and the low pressure steam control valve 8 are set to the fully open state by the bias setting device in order to perform full-circumference injection start-up. On the other hand, the low pressure steam stop valve 7 is fully closed by the valve opening signal of the low pressure steam control valve. Therefore, when the main steam stop valve 3 starts full-circle injection starting b, the turbine rotational speed E increases in response to the opening Wlvc of the valve. At point b, the turbine rotational speed reaches the rated rotational speed, and the high-pressure steam control valve 4 and low-pressure steam control valve 8 are closed by the bias setting device, and at point C, the high-pressure steam stop valve 3 is fully opened and partial injection operation begins. can be switched to At this point, the high pressure steam control valve 4 is open to some extent for speed control, but the low pressure steam control valve 8 is fully closed. At point d, the turbine is synchronously connected to the power system, and the high-pressure steam control valve 4 begins to increase the output F of the turbine. When the high-pressure steam control valve 4 opens to a certain degree, the forced closure of the low-pressure steam stop valve 70 is released, and the low-pressure steam stop valve is fully opened. A correction circuit operates, and the high-pressure steam control valve 4 is closed to some extent. In this way, when the low pressure steam stop valve 7 is fully opened, the low pressure steam control valve 8 is opened in conjunction with the high pressure steam control valve 4, and the output is increased.

〔Effect of the invention〕

As explained above, according to Honjitsu IIK, the load fluctuation that occurs when starting to supply low-pressure steam that has been flashed in two stages to the geothermal steam turbine changes the opening of the high-pressure steam control valve in response to the opening degree of the low-pressure steam stop valve. Since it is corrected based on the opening degree, smooth operation control of the turbine can be performed without causing load fluctuations when the low pressure steam stop valve is opened. Furthermore, there is no need to provide a complicated position control mechanism for the low-pressure steam stop valve, and good control functions can be achieved using the same operating method as the conventional one-stage seven-laser turbine. .

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a control device for a geothermal steam turbine according to the present invention, and FIG. 2 is a line diagram showing the movement of six valves at the time of turbine startup. High pressure steam control valve, 5
...Steam turbine, 7...Low pressure steam stop valve, 8...
・Low pressure steam control valve, field, 27.33-...adder, 5
...Arithmetic circuit, addition...unbalanced priority circuit, 28.39.
...Bias setting device, 31, 37.42.47...Hydraulic servo motor, Support...Load limiter, Side...Opening degree detection device. Applicant's agent Kiyoshi Inomata Figure 1 Figure 2 Figure 2

Claims (1)

[Claims] Geothermal steam that supplies high-pressure steam to the high-pressure stage of the turbine through a high-pressure steam stop valve and a high-pressure steam control valve, and supplies low-pressure steam to the low-pressure stage through a low-pressure steam stop valve and a low-pressure steam control valve. In the turbine control device, the opening detection device detects the opening of the low-pressure steam stop valve, and corrects fluctuations in turbine rotation speed or load due to leakage steam from the low-pressure steam control valve when the low-pressure steam stop valve is operated in the opening direction. A control device for a geothermal steam turbine, comprising a correction circuit that corrects a valve opening signal of a high-pressure steam control valve in a direction of decreasing it in accordance with a detection signal from the detection device.