JPS6228642Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field of the Invention The present invention relates to an exhaust chamber temperature control device for a steam turbine.

Technical Background of the Invention FIG. 1 shows a schematic system diagram of an exhaust chamber temperature control device common to the conventional system and an embodiment of the present invention. Steam turbines are generally divided into a high-intermediate pressure section and a low-pressure section. The steam that has done work in the high and intermediate pressure section (not shown) passes through the connecting pipe 1 and is guided to the turbine low pressure section 2. In the turbine low pressure section 2, the steam that has done the work of rotating the rotating shaft of the generator together with the rotating shaft 3 of the turbine high and intermediate pressure section becomes an exhaust flow 5 and is led to the condenser 6, where it condenses and becomes condensed water. The water is discharged by the pump 7, and most of it enters the feed water heater (not shown) via the condensate line 15, where it is circulated again to become steam. A spray water supply line 8 branched from the condensate line 15 passes through a pressure regulating valve 9, a spray valve (on-off valve) 10, a spray water supply line 13, and a spray nozzle 14 installed in a low-pressure exhaust chamber. Connected. Also spray valve 1
0 is the operation signal 12 from the spray control device 11
is opened and closed.

The temperature of the exhaust flow 5 of the turbine low pressure section 2 changes depending on the turbine load, and this is expressed as follows.
FIGS. 2 and 3. Turbine exhaust stream 5 temperature depends primarily on exhaust pressure and reheat steam temperature. Figure 2 shows the case where the reheat steam temperature is constant, but when the turbine load becomes low, the steam in the exhaust flow exceeds the saturation temperature curve a of the exhaust pressure and enters the superheating castle, so the temperature suddenly increases. growing. When the exhaust pressure is high, the exhaust temperature becomes even higher as shown in curves b and c. On the other hand, Figure 3 shows the case where the exhaust pressure is constant and the reheat steam temperature changes.As the reheat steam temperature is increased with the turbine load being low, the exhaust temperature curve changes from a'→b'→c' become higher as in

Problems with the Background Art Now, in recent years, steam turbines that use fossil fuels are increasingly being operated at the minimum load. In addition, the minimum load itself is gradually being lowered, and even if in the past the minimum operation was 25% load, continuous operation at 10 to 15% load is now required. When operating such a steam turbine, the rate at which the low-pressure exhaust chamber is overheated increases at low loads. Unfavorable phenomena occur in turbine operation, such as shaft vibration caused by changes in alignment. When the temperature rises, condensate is sprayed into the low-pressure exhaust chamber to lower the temperature, but when the spray is activated, the exhaust chamber is cooled all at once to the condensate temperature, that is, the saturation temperature corresponding to the exhaust pressure.
If you repeat this spray opening/closing control, for example, 60℃
This results in repeated large temperature changes in short cycles such as →30℃→60℃→30℃, which also causes large bearing vibrations due to casing deformation and changes in bearing alignment, making stable minimum load operation impossible.

Purpose of the present invention The present invention aims to maintain the reduced exhaust chamber temperature for a while by spraying, and perform operations to obtain the optimum exhaust chamber temperature during that time, such as changes in exhaust pressure, changes in reheat steam temperature, changes in load, etc. The purpose of the present invention is to provide an exhaust chamber temperature control device that allows stable minimum load operation by giving operators the time necessary to respond to the conditions.

Summary of the invention As shown in Fig. 4, the invention consists of a spray valve 10
When the temperature of the exhaust chamber exceeds the upper limit set value, the opening operation is performed through the OR circuit 29, and on the other hand, when the temperature of the exhaust chamber falls below the lower limit set value, the AND circuit 2 is activated.
In the exhaust chamber temperature control device, the exhaust chamber temperature control device is configured to cause a closing operation through the gates 7 and 7, and is provided with a delay circuit 30 that outputs an input signal exceeding the upper limit set value as an input signal to the AND circuit 27 after a certain period of time has elapsed. This gives the operator the time necessary to obtain the optimal value for the exhaust chamber temperature depending on the steam usage conditions, and enables stable minimum load operation.

Embodiment of the Invention Hereinafter, an embodiment of the invention will be described with reference to FIG. 4 showing the exhaust chamber temperature control device 11 shown in FIG. 1 in detail.

FIG. 4 shows an example in which the turbine exhaust flows in two streams, including a first exhaust chamber A and a second exhaust chamber B. Each exhaust chamber A, B is provided with a temperature detector consisting of a thermocouple (not shown), which detects when the upper limit predetermined temperature T ₁ ℃ or higher, and sends upper limit temperature excess signals 20, 21.
is input to the first AND circuit 23 via the first OR circuit 22. Furthermore, the temperature sensor allows
This is detected when the temperature is below the lower limit predetermined temperature T ₂ °C, and the below-lower-limit temperature signals 24 and 25 are input to the third AND circuit 27 via the second AND circuit 26 . Further, the exhaust chamber temperature control device 11 is provided with a device (not shown) that outputs an automatic exhaust chamber temperature use signal when it is in the automatic use state, and the output signal 28 is sent to the first and third AND circuits 23 and 27. Branch and input. The output signal of the first AND circuit 23 is input to the second OR circuit 29 and branched to the delay circuit 3.
0 to the third AND circuit 27. The setting time of the delay circuit 30 is 10 to 30 minutes. The output of the second OR circuit 29 is partially fed back to the OR circuit 29 itself and sends a spray valve opening control signal ₁₂₁ to the spray valve 10. The output of the third AND circuit 27 is the spray valve closing control signal 12 ₂
is sent to the spray valve 10.

Next, the effect will be explained.

The exhaust chamber temperature control automatic use signal 28 is output,
When any of the turbine exhaust chambers, for example A, becomes T ₁ °C or higher, a spray valve opening control signal 12 ₁ is issued,
The low pressure vent chamber spray is initiated and the delay circuit 30 is activated so that the spray is maintained for at least 10 to 30 minutes. During this time, the operator can take necessary measures in response to, for example, changes in exhaust pressure, temperature of reheated steam, changes in load, etc., and can lower the temperature of the low-pressure exhaust chamber to an optimum value. Note that while the delay circuit 30 is working, even if both turbine exhaust chambers A and B
Even if the temperatures of both are below T ₂ and the signal output passes through the second AND circuit 26 and is inputted to the third AND circuit 27, the signal from the delay circuit 30 will not pass through the third AND circuit 27. Since the spray valve close control signal ₁₂₂ is not output until the spray valve is opened, the spray valve 10 remains open, and the spray valve 10 does not open or close suddenly for a short period of time, which is the case in the past, and the spray valve 10 is stable. Minimum load operation is possible.

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, but can of course be implemented with various modifications without changing the gist thereof.

Effects of the invention By simply adding a delay circuit to the conventional control circuit, this invention provides time for the steam turbine to operate safely at its lowest load, thereby improving the exhaust gas flow, which contributes to stable operation of the turbine and a stable supply of electric power. A room temperature control device is obtained.

[Brief explanation of the drawing]

FIG. 1 is a system diagram schematically showing an exhaust chamber temperature control device common to the conventional system and an embodiment of the present invention;
The figure is a curve diagram showing the relationship between load and exhaust temperature when reheating steam is constant, Figure 3 is a curve diagram showing the relationship between load and exhaust temperature when exhaust pressure is constant, and Figure 4 is a curve diagram showing the relationship between load and exhaust temperature when the exhaust pressure is constant.
FIG. 2 is a block diagram showing a control system of the exhaust chamber temperature control device in one embodiment of the present invention shown in the figure. 8, 13... Spray water supply line, 10...
Spray valve, 11...Exhaust chamber temperature control device, 12
...Operation signal, 12 ₁ ...Open control signal, 12 ₂ ...
...Close control signal, 14...Spray nozzle, 15...
...Condensate line, 30...Delay circuit.

Claims (1)

[Scope of utility model registration request] An automatic exhaust chamber temperature control use signal is output to the spray valve, and when any of the temperatures in the multiple turbine exhaust chambers exceeds the upper limit set value, the upper limit set value excess signal and the upper limit set value exceeds signal are output. A part of the signal that controls the opening of the spray valve is fed back from the spray valve to cause an opening operation through an OR circuit, and when the temperature of the exhaust chamber falls below the lower limit set value, a closing operation is generated through an AND circuit. An exhaust chamber temperature control device comprising: a delay circuit that outputs an input signal exceeding the upper limit set value as an input signal of the AND circuit after a certain period of time has elapsed.