JP2872739B2 - Steam turbine start-up method and apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a turbine starting method using a main steam stop valve bypass start, and is particularly suitable for suppressing thermal stress generated in a main steam stop valve while suppressing a decrease in plant efficiency. The present invention relates to a method and an apparatus for starting a steam turbine.

[Conventional technology]

An example of a conventional steam turbine plant is shown in FIG.
Shown in the figure. In FIG. 5, the steam generated in the boiler 1 is heated by a super heater 2a and guided to a high-pressure turbine 5 through a main steam stop valve 3 and a steam control valve 4, and the high-pressure turbine 5 converts heat energy into rotational energy. Is converted.
The steam exiting the high-pressure turbine 5 passes through the check valve 12 and reheats 2b
Through the reheat steam stop valve 10 and the intercept valve 11 to the intermediate-pressure turbine 6 and the low-pressure turbine 7, and the intermediate-pressure turbine 6 and the low-pressure turbine 7 convert heat energy into rotational energy, respectively. . The exhaust gas from the low-pressure turbine is condensed by a condenser 8 and then returned to the boiler 1 by a water supply pump 9.

The starting methods of these steam turbines are roughly classified into the following two. One of them is to fully open the steam control valve 4 from the start-up and acceleration of the turbine to the low load zone and control the steam control valve 4 by a bypass valve provided in the main steam stop valve 3, and to control the main steam stop valve (MSV) in a certain load zone.
The main steam stop valve is a bypass start-up system in which the control is shifted from the bypass valve to the control of the steam control valve 4. It is a method. Further, the latter two types of starting methods by steam control 4 include a full-circulation injection starting method and a sequential opening starting method, and a combined starting method utilizing the advantages of both. The full-circle injection startup method has the advantage of low thermal stress due to steam flowing from the entire circumference of the turbine when the turbine is started, and the disadvantage of reduced efficiency due to throttling during rated load operation. The advantages and disadvantages are opposite to the above-described full-circle injection activation. Therefore, before the combined start-up system was born, a main steam stop valve bypass valve start-up system was adopted in which the turbine was started up and the whole load was sequentially opened from the intermediate load zone to the rated load operation during the rated load operation.

Here, the main steam stop 3 and the steam control valve 4 which have been used in the conventional main steam stop valve bypass valve activation system are different from the main steam stop valves 3a and 3b of a plurality of systems as shown in FIGS. 6 and 7. And a steam control valve 4 having a plurality of valves in one chest. The main steam stop valve 3a is provided with a bypass valve 15 inside the main valve 13a, whereas the main steam stop valve 3b has no bypass valve and has only the main valve 13b. Furthermore, in the main steam stop valves 3a and 3b, when the turbine is started, the steam is drained by the main steam stop valves 3a and 3b and the steam control valve 4 in a cold state. Therefore, drain valves 18a, 18b and 19a for discharging these drains are provided. , 19b are the main steam stop valve upper chambers 16a, 1 respectively.
6b and the lower chambers 17a, 17b.

Next, the operation of the main steam stop valves 3a, 3b and the steam control valve 4 in the process of increasing the speed and increasing the load from the start of the turbine is described in the eighth.
This will be described with reference to the drawings. First, the steam control valve 4 is fully opened from the start of the turbine to the speed increase and the switching load, and the main steam stop valve bypass valve 15 is slightly opened to control the steam flow. Next, in the switching load zone, the steam control valve 4 is narrowed down so that the differential pressure before and after the main steam stop valve 3a is about 15%, and then the main steam stop valve 3a is fully opened and the load of the turbine is controlled by the steam control valve 4. Control. Drain valves 18a, 18b, 1 of one main steam stop valve 3a, 3b
In 9a and 19b, both valves are fully closed at the timing immediately after the initial load is added and immediately after the switching point (timing, ~ ',
').

Related devices of this type include, for example, JP-B-58-33363 and JP-A-57-3805.

[Problems to be solved by the invention]

The above prior art uses a main steam stop valve in consideration of plant efficiency.
The main steam stop valve 3a having the bypass valve 15 when the drain valves 19a, 19b are fully closed before load-in or load switching so as to stop steam flowing out from the drain valves 19a, 19b of the 3a, 3b at an early stage.
The lower chamber 17a is warmed up by the steam flowing from the bypass valve 15 to the steam control valve 4. However, the temperature of the lower chamber 17b of the main steam stop valve 3b without the bypass valve is lowered due to the stoppage of the steam flow due to the full closure of the drain valve 19b. The temperature difference between the chambers 17b increases. In this state, when the main valve 13b of the main steam stop valve 3b without a bypass valve is opened at the time of valve switching, high-temperature steam flows from the upper chamber 16b into the lower chamber 17b, and the lower chamber
In 17b, the temperature changes rapidly and thermal stress is generated.

This phenomenon is caused by the fact that in recent thermal power plants, start-stop operations are generally performed daily or weekly, and together with the increase in the number of starts, the casing of the main steam stop valve 3b without a bypass valve as shown in FIG. Cracks 22 are generated in the corners and the like, and if this progresses, the worst case is steam leakage and damage. On the other hand, when the drain valves 19a, 19b of the main steam stop valves 3a, 3b are closed after the valve is switched, the turbine is not converted into rotational energy by the turbine in a load (normally about 15% load) band before the switching, and is used as drain. The efficiency of the plant decreases due to an increase in unnecessary steam discharged. As described above, no consideration was given to the thermal stress generated in the main steam stop valve without the bypass valve at the time of starting the turbine and the reduction in plant efficiency, and there were problems such as the life consumption of the steam valve and the reduction in plant efficiency. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a steam turbine starting method and a steam turbine starting method capable of reducing the life consumption of a steam valve while minimizing a decrease in plant efficiency at the time of starting the turbine.

[Means for solving the problem]

In order to achieve the above object, the steam turbine starting method and apparatus according to the present invention closes the lower chamber drain valve of the main steam stop valve having the bypass valve almost at the time of load consolidation during the bypass control operation, and does not have the bypass valve. The lower chamber drain valve of the main steam stop valve is closed after the switching point to the steam control valve control operation, at a specified load or more, or within a specified temperature difference between the upper chamber and the lower chamber.

In addition, regardless of the control of the opening / closing timing of the bypass valve, the bypass valve is provided so that steam flows into the lower chamber even when the lower chamber drain valve of the main steam stop valve without the bypass valve is closed. A flow path communicating the lower chamber of the main steam stop valve with the lower chamber of the main steam stop valve without the bypass valve is provided.

Also, in order to ensure that the lower chamber drain valve does not close unless the main valve of the main steam stop valve without the bypass valve opens, the lower chamber must be opened on condition that the main valve of the main steam stop valve without the bypass valve is open. The drain valve is closed.

(Operation)

In the above steam turbine starting method and its apparatus, the lower chamber drain valve of the main steam stop valve having the bypass valve and the main steam stop valve without the bypass valve is fully opened from the start of the turbine to the time when the speed is increased and the load is added. In advance, the lower chamber drain valve of the main steam stop valve having the bypass valve is closed at an early stage after the loading of the load, but the lower chamber drain valve of the main steam stop valve without the bypass valve is fully opened. Then, the steam from the bypass valve flows through the steam control valve through the drain valve to warm up the lower chamber of the main steam stop valve without the bypass valve, and then the load is increased to shift from bypass valve control to steam control valve control. The turbine control is switched, and the main valve of the main steam stop valve is fully opened.However, since the lower chamber is sufficiently warmed up by closing the drain valve after this switching point, the thermal stress generated in the casing part Small can be reduced lifetime consumption due to repeated thermal stress caused by the turbine starting. Alternatively, detect the metal temperature of the inner wall of the upper and lower chambers of the main steam stop valve without a bypass valve, close the drain valve within the specified temperature difference that does not cause cracks in the casing, and exceed the specified temperature difference. By opening the drain valve at the same time, it is also possible to eliminate the life consumption due to thermal stress and minimize the decrease in plant efficiency.

Also, regardless of the opening / closing timing of the drain valve, the lower chamber of the main steam stop valve having the bypass valve and the lower chamber of the main steam stop valve without the bypass valve are communicated, so that the steam always flows to the lower chambers of both valves and the upper chamber The occurrence of shear stress can be suppressed by reducing the temperature difference between the lower chamber and the lower chamber, so that the life consumption of the steam valve casing can be reduced without reducing the plant efficiency.

Also, by detecting the open state of the main valve of the main steam stop valve without a bypass valve and closing the lower chamber drain valve under this condition, it is possible to prevent erroneous closing of the drain valve at the time of occurrence of main valve malfunction etc. Thus, the life consumption due to thermal stress can be more reliably eliminated.

〔Example〕

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

FIG. 1 is a characteristic diagram showing one embodiment of a steam turbine starting method and an apparatus therefor according to the present invention. In FIG. 1, an embodiment in which the steam turbine starting method of the present invention is applied to the configuration system of the steam turbine plant shown in FIG. 5 and the system of the main steam stop valve and the steam control valve shown in FIG. 6 and FIG. The characteristics of the example are shown.

From the start of the turbine in FIG. 1 to the time of acceleration and load addition, the drain valves 19 of the lower chambers 17a and 17b of the main steam stop valve 3a having the bypass valve 15 and the main steam stop valve 3b having no bypass valve are provided.
a, 19b fully open and bypass valve 1
The drain valve 19a of the lower chamber 17a of the main steam stop valve 3a having 5 is closed (timing). In this case, the drain valve 19b of the lower chamber 17b of the main steam stop valve 3b without the bypass valve is fully opened, so that the steam from the bypass valve 15 of the main steam stop valve 3a having the bypass valve 15 is steamed from the lower chamber 17a. Control valve 4
And the lower chamber 17b of the main steam stop valve 3b without a bypass valve
And flows out from the drain valve 19b, and the lower chamber 17 of the main steam stop valve 3b without the bypass valve is warmed up by the steam.

Then, the load is increased, the turbine control is switched from the control of the bypass valve 15 of the main steam stop valve 3a to the control of the steam control valve 4, and the main valve 13b of the main steam stop valve 3b without the bypass valve is fully opened. At this time, the valve stem of the main steam stop valve 3b without a bypass valve
The opening operation of 14b or the differential pressure or load before and after the main steam stop valve 3b is detected and compared with each specified value at the switching point to judge that the switching has been performed, so that the main steam stop without the bypass valve is performed. The drain valve 19b of the valve 3b is closed (timing).

Since the lower chamber 17b of the main steam stop valve 3b without the bypass valve is sufficiently warmed in this way, the thermal stress generated in the casing is small, so that the crack 22 as shown in FIG. 9 does not occur. In addition, the life consumption due to the repeated thermal stress accompanying the start of the turbine can be reduced.

FIG. 2 is a system diagram of a main steam stop valve and a steam control valve showing an embodiment of the steam turbine starting device according to the present invention. In FIG. 2, the temperature detectors 24, 25 provided by the present invention measure the inner wall metal temperatures of the upper chamber 16b and the lower chamber 17b of the main steam stop valve 3b without a bypass valve having the same system as that shown in FIG. The temperature difference between the temperature detectors 24 and 25 is compared with a specified temperature difference that does not cause cracks or the like in the casing of the lower chamber 17b by the temperature comparator 26. 19b to drain valve drive 27
Closes with the drain valve 19
b is opened by the device 27. As a result, life consumption due to thermal stress of the main steam stop valve 3b and the like can be reduced, and a decrease in plant efficiency can be minimized.

FIG. 3 is a system diagram of a main steam stop valve and a steam control valve showing another embodiment of the steam turbine starting device according to the present invention. In FIG. 3, according to the present invention, between the lower chambers 17a and 17b of the main steam stop valve 3a having the bypass valve 15 having the same system as that shown in FIG. 6 and the main steam stop valve 3b having no bypass valve. A communication pipe 23 is provided as a flow path communicating the lower chambers 17a and 17b. As a result, the lower chambers 17a, 1 of the two main steam stop valves 3a, 3b are
Steam is always flowed simultaneously to 7b to reduce the temperature difference between the upper chamber 16b and the lower chamber 17b of the main steam stop valve 3b without a bypass valve,
Since the generation of thermal stress in the lower chamber 17b can be suppressed regardless of the opening / closing timing control of the drain valves 19a and 19b shown in FIG. 1, similarly, the life consumption of the steam valve casing can be reduced without lowering the plant efficiency. .

FIG. 4 is a system diagram of a main steam stop valve and a steam control valve showing still another embodiment of the steam turbine starting device according to the present invention. In FIG. 4, a valve opening for detecting the opening of the main valve 13b according to the present invention is provided to the valve rod 14b of the main steam stop valve 3b or the drive system thereof without the bypass valve having the same system as that shown in FIG. A detector 28 is provided, and the controller 29 detects that the main valve 13b is not fully closed by the output of the detector 28 and closes the drain valve 19b, so that the drain valve 19b is not closed unless the main valve 13b is opened. As a result, it is possible to prevent the drain valve 19b from being erroneously closed when the main valve 13b malfunctions or the like, and it is possible to more reliably eliminate the life consumption due to the thermal stress.

〔The invention's effect〕

According to the present invention, the temperature difference between the upper chamber and the lower chamber of the main steam stop valve at the time of starting the turbine can be reduced, and a rapid temperature change at the time of opening the main valve can be prevented. In addition, there is an effect capable of suppressing life consumption. In addition, since the amount of steam flowing out of the drain valve of the main steam stop valve at the time of starting the turbine can be reduced, a reduction in plant efficiency can be suppressed.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram of one embodiment of the present invention, FIG. 2 is a system diagram of one embodiment of the present invention, FIG. 3 is a system diagram of another embodiment of the present invention, and FIG. System diagram of still another embodiment, FIG.
The figure is a system diagram of a conventional steam turbine plant, FIG. 6 is a system diagram of a conventional example, FIG. 7 is an external view of a main steam stop valve and a steam control valve of a conventional example, and FIG. 8 is a characteristic diagram of the conventional example. FIG. 9 is a sectional view of a conventional main steam stop valve. 1 ... boiler, 2a ... super heater, 2b ... reheater,
3,3a, 3b …… Main steam stop valve, 4 …… Steam control valve, 5,6,7…
... Steam turbine, 8 ... Condenser, 9 ... Feed pump, 10
... Reheat steam stop valve, 11 ... Intercept valve, 12 ... Check valve, 13a, 13b ... Main valve, 14a, 14b ... Valve stem, 15 ... Bypass valve, 16a, 16b ... Main steam Stop valve upper chamber, 17a, 17b ……
Main steam stop valve lower chamber, 18a, 18b …… Main steam stop valve upper chamber drain valve, 19a, 19b …… Main steam stop valve lower chamber drain valve, 2
0… Valve seat, 21… Insulation section, 22… Crack, 23… Connecting pipe, 24,25… Temperature detector, 26 …… Temperature comparator, 27…
... Drain valve drive, 28 ... Valve opening detector, 29 ... Control device.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F01D 19/00 F01D 25/10 F01D 17/10

Claims (5)

(57) [Claims] A main steam stop valve having a bypass valve for controlling a steam flow among a plurality of main steam stop valves; a main steam stop valve having no bypass valve for controlling a steam flow; A steam control valve for controlling the steam flow rate provided downstream of the stop valve, and a drain valve provided on the downstream side separated by a valve body and a valve seat of a casing of the plurality of main steam stop valves. When starting the steam turbine, first control the steam flow rate by the bypass valve of the main steam stop valve having the bypass valve,
After that, in the steam turbine starting method of the main steam stop valve bypass valve starting method in which the steam flow is controlled by the steam control valve, the main steam stop valve having the bypass valve is operated by the main steam stop valve bypass valve control operation when the steam turbine is started. A method for starting a steam turbine, comprising closing the drain valve of a main steam stop valve without a bypass valve substantially after a switching point during the steam control valve control operation. 2. The steam turbine starting method according to claim 1, wherein the drain valve of the main steam stop valve without the bypass valve is closed when a difference in steam pressure before and after the main steam stop valve is within a specified differential pressure. 3. The steam turbine starting method according to claim 1, wherein the drain valve of the main steam stop valve having no bypass valve is closed at a specified load or more. 4. A main steam stop valve having a bypass valve for controlling a steam flow among a plurality of main steam stop valves, a main steam stop valve having no bypass valve for controlling a steam flow, and the plurality of main steam stops. A steam control valve for controlling the steam flow rate provided downstream of the valve, and a drain valve provided on the downstream side separated by a valve body and a valve seat of a casing of the plurality of main steam stop valves, In a steam turbine starting device of a main steam stop valve start-up type in which a steam flow is controlled by a bypass valve of a main steam stop valve having a bypass valve first and then a steam flow rate is controlled by a steam control valve at the start of the steam turbine, When the turbine is started, the drain valve of the main steam stop valve having the bypass valve is closed almost when the load is applied during the main steam stop valve bypass valve control operation, and then the drain of the main steam stop valve without the bypass valve is operated. Steam turbine starting device being characterized in that the arrangement for controlling the valve substantially switching point after closing state of the steam control valve control during the operation. 5. The drain valve of a main steam stop valve without a bypass valve is controlled so that a temperature difference measured by a temperature detector of an inner wall or an outer wall metal of an upper chamber and a lower chamber of the main steam stop valve is within a specified value. 5. The configuration according to claim 4, wherein
The steam turbine starting device according to any one of the preceding claims.