JPH0138165B2 - - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a geothermal turbine protection device, and more particularly to a geothermal turbine protection device suitable for protecting turbine blades from damage from water droplets and impurities.

[Technical background of the invention]

Geothermal power plants use steam extracted from underground to rotate turbines and generate electricity, and in recent years many have been constructed from the standpoint of energy conservation. In geothermal areas, volcanic activity creates pools of magma deep underground that heat the surrounding rocks, and groundwater seeps into these pools and becomes heated hot water, which is stored in reservoirs. We drill into this reservoir and extract it to the ground as fumarole steam.
Geothermal power generation is used for power generation.

An example of the configuration of such a geothermal power plant will be explained using the system diagram shown in FIG. Hot water, steam, and gas (hereinafter referred to as hot water) taken out from the production well 1 are led to a separator 2 and separated into steam, gas, and hot water. The separated steam becomes primary main steam and is sent to the turbine 3, and the hot water is led to the flasher 4. In the flasher 4, hot water is injected into the vessel to vaporize it and separate it into steam and hot water. The steam separated by the flasher 4 becomes secondary main steam, which is guided to the turbine 3, rotates the turbine 3 together with the primary main steam, rotates the generator 5, and generates electricity. The hot water separated by the flasher 4 is returned underground by the reinjection well 6. This configuration is called a two-stage flush system because steam and hot water are separated twice, but in addition to this system, one-stage flash systems and the like are also known.

In such a system configuration, the internal pressures of the separator 2 and the flasher 4 are determined by the balance between the flow rate of hot water etc. from the production well 1, enthalpy, and the flow rate into the turbine. Therefore, if a situation occurs in which this balance is disrupted, the internal pressures of both chambers will fluctuate. For example, when the turbine 3 trips due to some abnormality and the steam valves 7 and 8 are fully closed, the pressures in the flasher 4, separator 2, and steam pipes 9 and 10 increase. In order to protect the flasher 4, separator 2, and steam pipes 9, 10 from such accidents, steam relief valves 11, 12 are generally provided.

Conversely, when the steam valves 7 and 8 of the turbine are suddenly opened, the pressure drops. Further, in many cases, a plurality of separators 2 and flashers 4 are provided due to capacity, and some of the separators 2 and flashers 4 are connected to the steam source valve 13 or the steam source valve 13.
Even when the steam is cut off by fully closing the steam valve 4, a pressure drop occurs due to insufficient steam supply. When such a pressure drop occurs, the amount of steam generated within the separator 2 and flasher 4 increases,
The flow rate inside the vessel also becomes faster.

Incidentally, FIG. 2 is a characteristic diagram showing the relationship between the internal pressure and the flow rate, which changes according to the solid line b when the flow rate is small and the solid line c when the flow rate is large.

By the way, it is known that when the flow velocity in the vessel increases and exceeds a certain point, impurities such as water and mud contained in the steam sent to the turbine rapidly increase. Generally, this flow velocity is called the critical flow velocity, and forms the boundary shown by the broken line a in FIG.

[Problems with background technology]

Here, we will discuss the effect when the flow velocity inside the separator 2 or the flasher 4 exceeds the critical flow velocity and wet steam containing water and impurities flow into the turbine 3. Geothermal turbines are originally driven by saturated steam, so they are designed with some degree of wet steam in mind. However, if a large amount of water droplets and impurities flow in, they will hit the blades of the turbine 3, and not only will they themselves damage the turbine, but there is a high possibility that the blades will cause abnormal vibrations, leading to damage.

Traditionally, turbine protection devices have been known to monitor the turbine inlet pressure and throttle the steam valve to prevent a pressure drop when the pressure drops. is not determined solely by steam pressure, and it is insufficient to deal with the pressure drop alone. Furthermore, when the turbine 3 is operating at a small flow rate, the steam pressure that reaches the critical flow velocity is low, and it is not a good idea to simply close the steam valve at a constant pressure.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, the object of the present invention is to provide a geothermal turbine protection system that eliminates the problems of the prior art, prevents the separator or flasher from reaching its critical flow velocity, and protects the turbine blades from scratches and damage. The goal is to provide equipment.

[Summary of the invention]

In order to achieve the above object, the present invention includes a flow rate detection means for detecting the amount of steam sent out from a steam generation means that generates steam from underground hot water and supplies it to a turbine, and a steam valve at the turbine inlet. A pressure detection means for detecting the pressure on the upstream side, a calculation means for calculating the opening degree of the steam valve based on each output signal of the pressure detection means and the flow rate detection means, and a means for generating a final load signal for the steam valve. A geothermal turbine, comprising: a control means for selecting a signal satisfying turbine permissible conditions from among the output signal of the calculation means and the final load signal, and controlling a steam valve based on this signal. It provides a protective device.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a block diagram of a geothermal turbine protection device according to an embodiment of the present invention. In the configuration shown in the figure, the rotation speed of the turbine 3 is detected by a speed detector 15. The detected speed signal is compared with a set speed signal set by the speed setter 16 in a comparison section 17, and the amount of deviation is transmitted to an adjustment rate calculation section 18. The adjustment rate calculation unit 18 multiplies the deviation amount by a gain corresponding to a preset speed adjustment rate and sends the result to the addition unit 19 . In the adder 19, the load setter 2
Add the signal set at 0 to create a load signal. The load signal is compared with the load limit value set by the load limiter 21 in the low value priority circuit 22, and the lower signal becomes the final load signal.

On the other hand, regarding the primary steam, the primary steam pressure detector 28 detects its pressure, and the primary steam flow rate detector 29 detects its flow rate. Each detector 28,
The output of 29 is input to a calculator 30, and when the steam condition deteriorates, a signal is calculated to close the primary steam valve 7 according to the amount of deterioration and is sent to a low value priority circuit 31. Incidentally, the final load signal from the low value priority circuit 22 is also input to the low value priority circuit 31. The output signal of the low value priority circuit 31 controls the valve position of the primary steam valve 7 as a flow rate signal. That is, this flow rate signal is compared with the valve position feedback signal in the comparison section 23, and the deviation signal is converted into a valve drive signal by the adjustment control section 24, and the primary steam valve 7 is adjusted by the valve drive unit 25. Incidentally, the movement of the primary steam valve 7 is detected by the position detector 26, and is fed back to the comparison section 23 via the position conversion section 27, and is used for valve position control.

On the other hand, regarding secondary steam, a secondary steam pressure detector 32 detects its pressure, and a secondary steam flow rate detector 33 detects its flow rate. Each detector 32,
The output of 33 is input to a calculator 34, and when the steam condition deteriorates, a signal is calculated to close the secondary steam valve 8 according to the amount of deterioration, and is sent to a low value priority circuit 35. Incidentally, the final load signal from the low value priority circuit 22 is also input to the low value priority circuit 35. The output signal of the low value priority circuit 35 controls the valve position of the secondary steam valve 8 as a flow rate signal. That is, this flow rate signal is compared with the valve position feedback signal in the comparison section 43, and the deviation signal is converted into a valve drive signal by the adjustment control section 44, and the secondary steam valve 8 is adjusted by the valve drive unit 45. Incidentally, the movement of the secondary steam valve 8 is detected by the position detector 46, and is fed back to the comparison section 43 via the position conversion section 47, and is used for valve position control.

The operation of this configuration will be explained next. The operation of the control circuit for the primary steam valve and the control circuit for the secondary steam valve is exactly the same, so the operation of the control circuit for the primary steam valve will be described here.

The calculator 30 receives the signals from the primary steam pressure detector 28 and the primary steam flow rate detector 29, and sends a signal to close the primary steam valve 7 according to the amount of deterioration when the steam condition deteriorates to a low value priority circuit 31. tell. The low value priority circuit 31 compares the valve position signal based on the final load signal from the low value priority circuit 22 with the signal from the arithmetic unit 30, and selects the lower one of the two. That is, when the output signal of the computing unit 30 is low, the primary steam valve 7 is throttled to protect the turbine, and when it is high, the opening degree of the primary steam valve 7 is determined by the final load signal. . Note that the valve control is based on the output signal of the low value priority circuit 31, and is controlled by the comparison section 23, the adjustment control section 24, the valve drive unit 25, and the position detector 2.
6. Executed by the closed loop control system of the position conversion unit 27.

Next, the calculation contents of the calculator 30 are shown in FIGS. 4 and 5.
This will be explained using the characteristic diagram shown in the figure. Incidentally, Fig. 4 shows the limit curve d, the rated operating point e, and the computing unit, in which the dashed line a of the limit flow rate between the internal pressure and flow velocity of the separator 2 or the flasher 4 explained in Fig. 2 is replaced with steam pressure and steam flow rate. 30 shows a limit curve f under which the output of No. 30 falls below the rated opening degree of the primary steam valve 7, and a condition g under which the primary steam valve 7 is fully closed. On the other hand, FIG. 5 shows the relationship between the steam conditions and the output of the calculator 30, that is, the valve opening of the primary steam valve 7, and the limit curves f and g and the rated operating point e shown in FIG. It is shown.

When the turbine 3 is operated with steam better than the steam condition shown by the limit curve f, the calculator 30
The output of is more than the rated valve opening of the primary steam valve 7,
The final load signal is conveyed to the primary steam valve 7 due to the effect of the low value priority circuit 31 described above. If the steam conditions become worse than the conditions shown by the limit curve f,
As shown in FIG. 5, a signal is output from the computing unit 30 to reduce the valve opening depending on the degree of deterioration. By reducing the opening degree of the primary steam valve in this way, the amount of steam ejected from the separator 2 or the flasher 4 is reduced, and the pressure is further restored to prevent the separator 2 or the flasher 4 from reaching the critical flow velocity point. Can be done. If the steam condition does not recover even after closing the primary steam valve 7, set the fully closed condition g.
At the position shown in , the primary steam valve 7 is fully closed and the turbine can be completely protected.

Of course, the secondary steam valve is also controlled in exactly the same way.

By controlling as described above, it can be expected to protect the turbine from deterioration of driving steam conditions and restore the functions of the separator and flasher, but if the purpose is limited to protecting the turbine, the limit shown in Figure 4 will be reached. A sufficient effect can be obtained simply by issuing an alarm under the steam condition shown by curve f and tripping the turbine under steam condition g in the figure.

〔Effect of the invention〕

As described above, according to the present invention, the geothermal turbine can be protected from scratches and damage caused by the inflow of water droplets and impurities with a relatively simple configuration, and the geothermal turbine can be efficiently operated. It is possible to obtain equipment.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a conventional geothermal power plant, FIG. 2 is a characteristic diagram showing the relationship between internal pressure and flow velocity, and FIG. 3 is a block diagram of a geothermal turbine protection device according to an embodiment of the present invention. FIG. 4 is a characteristic diagram showing the relationship between steam pressure and steam flow rate, and FIG. 5 is a characteristic diagram showing the relationship between steam conditions and steam valve opening. 2...Separator, 3...Turbine, 4...Flushier, 7...Primary steam valve, 8...Secondary steam valve, 15...Speed detector, 18...Adjustment rate calculation unit, 22, 31, 35...Low value priority circuit, 28...
...Primary steam pressure detector, 29...Primary steam flow rate detector, 30, 34...Arithmetic unit, 32...Secondary steam pressure detector, 33...Secondary steam flow rate detector.

Claims (1)

[Scope of Claims] 1. Flow rate detection means for detecting the amount of steam sent out from the steam generation means that generates steam from underground hot water and supplies it to the turbine, and a pressure detecting means for detecting; a calculating means for calculating the opening degree of the steam valve based on each output signal of the pressure detecting means and the flow rate detecting means; a means for generating a final load signal for the steam valve; A geothermal turbine comprising: a control means for selecting a signal that satisfies permissible conditions for the turbine from among the output signal of the calculation means and the final load signal, and controlling the steam valve based on this signal. Protective device. 2. According to claim 1, the control means includes a circuit that outputs a signal for controlling the steam valve to the closing side with priority among the output signal of the calculation means and the final load signal. geothermal turbine protection equipment. 3. The geothermal turbine protection device according to claim 1, wherein the control means includes means for detecting deterioration of steam conditions based on the output signal of the calculation means and generating an alarm. 4. The geothermal turbine protection device according to claim 1, wherein the control means includes means for detecting deterioration of steam conditions based on the output signal of the calculation means and stopping operation of the turbine.