JP2557930B2 - Circulating water pump blade opening control device for steam turbine exhaust cooling - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a circulating water pump blade opening control device for cooling a steam turbine exhaust, which is applied to a thermal power plant, a nuclear power plant or the like.

(Prior art) In a thermal power plant or a nuclear power plant, a circulating water system using natural water such as seawater, river water, and lake water is adopted as a means for cooling turbine exhaust flowing from a steam turbine to a condenser. It is well known to be done.

Conventionally, a fixed vane type circulating water pump with a constant blade opening was used in such a circulating water system, but in recent years, from the viewpoint of energy saving, an amount of circulating water commensurate with the steam turbine load (output) can be supplied. Movable vane type circulating water pumps have been applied. This movable vane type circulating water pump has a structure in which the opening of the pump vane is variable. The blade opening is controlled to be the same.

(Problems to be Solved by the Invention) However, the blade opening control up to this point is to simply increase or decrease the circulating water amount, that is, the pump blade opening in accordance with the turbine load. is there.

The temperature of natural water such as seawater, river water, and lake water varies depending on the season. For example, when the water temperature rises in the summer, the cooling capacity decreases, and the degree of vacuum of the condenser decreases accordingly.
Note that the vacuum degree of the condenser also decreases in the same manner as described above even when the inside of the condenser tube becomes dirty and the cleanliness of the condenser decreases.

If the condenser is operated with the vacuum level lowered, the turbine load will be reduced accordingly, so if the steam turbine load needs to be maintained at a constant value, the steam supply to the steam turbine should be increased. There must be. However, when the amount of steam supplied to the steam turbine increases, the amount of heat exchange in the condenser also increases, and the circulating water temperature (outlet temperature) at the condenser outlet exceeds the limit value (for example, 7 ° C). There is a possibility that it will be driven.

The present invention has been made in view of such circumstances, and even when the circulating water temperature rises, a predetermined turbine load operation can be performed by maintaining the inlet / outlet temperature difference within the limit value, and the movable blade circulating water pump is effective. It is an object of the present invention to provide a circulating water pump blade opening control device for cooling a steam turbine exhaust gas, which can be operated as described above.

[Structure of Invention]

(Means for Solving the Problems) The present invention relates to a turbine load detector for detecting a steam turbine load, in a system for controlling a blade opening of a circulating water pump used for a circulating water system for cooling a steam turbine exhaust of a power plant. , A pump blade opening detector that detects the circulating water pump blade opening and the detection signals of these detectors are input, and the pump blade set opening and pump blade opening detection signal that are obtained based on the turbine load detection signal The first comparison calculation means for calculating the required pump blade opening by comparing the actual pump blade opening based on the above, and outputting the pump blade opening command signal based on the calculated value, and the circulating water system. An inlet temperature detector that detects the inlet temperature, an outlet temperature detector that detects the circulating water system outlet temperature, and a temperature detection signal from both of these temperature detectors are input to determine the inlet and outlet temperature difference of the circulating water. Second comparison operation means for outputting an opening increase command signal for increasing the pump blade opening when the temperature difference exceeds a certain limit value, and instructions from the first and second comparison operation means Input the signal,
When the inlet / outlet temperature difference of the circulating water is less than or equal to the limit value, a pump blade opening command signal based on the first comparison calculation means is output, and when the inlet / outlet temperature difference of the circulating water exceeds the limit value, the first comparison is performed. Pump blade opening setting switching means for switching and outputting the added pump blade opening command signal obtained by adding the pump blade opening command signals based on the pump blade opening command signal output from the calculating means at a predetermined ratio, and the pump blade opening setting switching means. And a pump blade opening adjustment device for adjusting the blade opening of the circulating water pump by inputting a pump blade opening command signal output from the degree setting switching means.

(Operation) When the inlet / outlet temperature difference is within the limit value such as when the circulating water temperature is below a certain level, the pump blade opening command signal output from the first comparison calculation means, that is, the steam turbine load is dealt with. Normal operation is performed based on the pump blade opening command signal.

On the other hand, when the circulating water temperature rises or the condenser cleanliness decreases, such as in summer, when the condenser vacuum decreases and the inlet / outlet temperature difference exceeds the limit value, the pump blades open. The opening degree command signal in which the pump blade opening degree is added is output by the degree setting switching means, whereby the circulating water amount increases.

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

FIG. 1 shows the configuration of a steam turbine steam system and a turbine exhaust cooling system of a thermal power plant.

A steam turbine 4 is connected to a main steam pipe 2 derived from a steam generator 1 such as a boiler via a main steam stop valve / control valve 3, and a generator 5 is connected to the steam turbine 4.

A condenser 6 is connected to the steam turbine 4, and the condenser 6 is provided with a turbine exhaust cooling system 7. The turbine exhaust cooling system 7 uses seawater as cooling circulating water, and includes a movable vane type circulating water pump 8 for pumping seawater and a pump outlet valve 9
And a circulating water pipe 11 for water supply having a condenser inlet valve 10. Further, a circulating water pipe 13 for drainage having a condenser outlet valve 12 is provided, and this circulating water pipe 13 is guided to a discharge channel 14.

The circulating water pump 8 is provided with a pump blade opening degree adjusting device 15 for controlling the blade opening degree of the pump 8 and a pump blade opening degree detector 16 for detecting the opening degree. In the circulating water pipes 11 and 13, a condenser inlet seawater temperature detector 17 as an inlet temperature detector,
A condenser outlet temperature detector 18 as an outlet temperature detector is provided, and a load detector 19 is provided on the generator 5.

During operation, the steam generated by the steam generator 1 is sent by the main steam pipe 2 to the steam turbine 4 through the main steam stop valve / regulator valve 3 and is used for work (driving the generator) and then condensed. Sent to container 6.

The turbine exhaust sent to the condenser 6 is the circulating water pump 8
The seawater that has been heat-exchanged with the seawater supplied by the above and is condensed, and the temperature of which rises is discharged to the discharge channel 14. The circulating water supply amount to the condenser 6 is determined by controlling the blade opening of the circulating water pump 8 by the pump blade opening adjustment device 15.

FIG. 2 shows a system configuration of a circulating water pump blade opening control device for driving the blade opening adjustment device 15. As input signals, a turbine load detection signal 101 output from a load detector 19 provided in the generator 5 and a pump blade opening detection signal 102 output from a pump blade opening detector 16 provided in the circulating water pump 8. , The inlet seawater temperature detection signal 103 and the outlet seawater temperature detection signal 1 output from the condenser outlet seawater temperature detector 17 and the condenser outlet seawater temperature detector 18 provided in the circulating water pipes 11 and 12, respectively.
Use 04.

The turbine load detection signal 101 and the pump blade opening detection signal 102 are input to the first comparison calculation means 20. This first
In the comparison calculation means 20 of, the pump blade setting opening set in advance corresponding to the turbine load detection signal 101 and the actual pump blade opening based on the pump blade opening detection signal 102 are compared, The pump blade opening degree is calculated, and the pump blade opening degree instruction signal 105 is output based on the calculated value.

Here, the pump blade set opening degree will be described with reference to FIGS. FIG. 3 shows the pump characteristics for each blade opening of the circulating water pump. Loads A, B, C, D on the steam turbine 4
When the blade openings corresponding to (A <B <C <D) are a, b, c, d, the circulation pump opening for each opening is represented by the characteristic curve shown in FIG. For each blade opening, the vacuum degree of the condenser 6 is the rated vacuum degree (normally 722 mmHgVAC), and the condenser inlet / outlet temperature difference is, for example, 6.8 ° C (limit of 7 ° C with 0.2 ° C margin).
The required circulating water amount is obtained as the intersection with the system head curve H of the circulating water system.

FIG. 4 is a blade opening of the circulating water pump 8 shown in FIG.
The relationship between a, b, c, d and turbine loads A, B, C, D is shown. The blade opening gradually increases according to the turbine load. The correspondence shown in FIG. 4 corresponds to the first comparison operation means 20.
Is programmed into the turbine load detection signal 10
When 1 is input, the pump blade set opening corresponding to this is obtained.

FIG. 5 shows an example of setting the blade opening. That is, when the turbine load L is less than A (L <A), the blade opening is a
%, B% when A or more and less than B (A ≦ L <B), c% when B or more and less than C (B ≦ L <C), and C or more and less than D (C ≦
When L <D), it is d%.

In the above-described first comparison calculation means 20, these blade opening values are compared with the actual pump blade opening based on the pump blade opening detection signal 102, and the required pump blade opening command signal 105 Is output to the pump blade opening adjustment device 21.

The pump blade opening command signal 105 passes through the pump blade opening setting switching means 22. The pump blade opening setting switching means 22 has an adding means 23 and a circuit switching switch 24, and the circuit switching switch 24 is controlled by the second comparison calculation means 25.

The inlet seawater temperature detection signal 103 and the outlet seawater temperature detection signal 104 are input to the second comparison calculation means 25.
Then, the inlet / outlet temperature difference (Δt) is obtained by the second comparison calculation means 25, and when the temperature difference (Δt) exceeds a certain limit value, an opening for increasing the pump blade opening is performed. The degree increase command signal 106 is output to the circuit changeover switch 24.

The circuit changeover switch 24 sends a pump blade opening instruction signal 105 output from the first comparison calculation means 20 to the pump blade opening adjusting device 21 immediately after the opening increase instruction signal 106 is not input. The configuration. Also, a second comparison calculation means
When the opening increase command signal 106 from 25 is input, the addition pump blade opening command signal 10 is obtained by temporarily adding the pump blade opening command signal 105 from the first comparison calculation means 20 by the adding means 23.
The circuit is switched to send 7 to the pump blade opening adjustment device 21.

FIG. 6 shows an addition program incorporated in the addition means 23. That is, the vertical axis shows the increase amount (%) of the circulation pump blade opening, and the horizontal shaft shows the turbine load (%). As shown in FIG. 6, each turbine load A, B, C, D
On the other hand, a program is provided for increasing the pump blade opening degree by a fixed rate (x%), and in response to this, the adding pump blade opening command signal 107 is sent from the adding means 23 to the pump blade opening adjusting device 2
Output to 1.

Then, during operation, the first comparison calculation means 20 compares the turbine load detection signal 101 detected by the turbine load detector 19 and the pump blade opening signal 102 detected by the pump blade opening detector 16 with each other. The calculation is performed to calculate the circulating water pump blade opening corresponding to the steam turbine load (output). Then, the pump blade opening instruction signal 105 is sent to the pump blade opening adjusting device 15 via the pump blade opening switching device 22, and the blade opening of the pump is set.

Further, when the condenser vacuum degree is lowered, the steam supply amount to the steam turbine 4 is increased, and the seawater inlet / outlet temperature difference (Δt) to the condenser 6 exceeds the limit value, Temperature detection signal for the inlet seawater detected by the water inlet temperature detector 17
And the outlet seawater temperature detection signal 104 detected by the condenser outlet seawater temperature detector 18 are used for comparison calculation by the second comparison calculation means 25, and the inlet / outlet temperature difference of the seawater to the condenser (Δ
The value of t) is calculated. When Δt is equal to or larger than the limit value, the addition pump 23 via the addition means 23 is operated by the pump blade opening increase command signal 106 from the second comparison calculation means 25 in the pump blade opening setting switching means 22. The blade opening command signal 107 is sent to the pump blade opening adjusting device 21 to set the blade opening. In addition, when the condenser seawater inlet / outlet temperature difference (Δt) decreases below a certain value below the limit value, the second comparison calculation means
The signal from 25 is no longer output, and the pump blade opening setting switching means 22 receives only the signal 105 from the first comparison calculation means 20 and does not pass through the second adder. The opening will be operated at the blade opening of the normal pattern. Therefore, according to the embodiment, even if the condenser seawater inlet / outlet temperature difference exceeds the limit value itself,
The opening degree of the circulating water pump blade increases, and the circulating water is operated at a temperature difference of the circulating water that is less than or equal to the limit value.

〔The invention's effect〕

As described above, according to the present invention, during normal operation, the circulating water pump blade opening is set to match the steam turbine load (output), while the limit value of the condenser circulating water inlet / outlet temperature difference is exceeded. In this case, the blade opening of the circulating water pump is automatically increased, and the temperature difference can be maintained below the limit value. In addition, when the condenser vacuum level is restored, the circulating water pump blade opening of the normal operation pattern is maintained, so that the condenser seawater inlet / outlet temperature difference due to the condenser vacuum level change Even if exceeds the limit value, an instruction to increase the opening degree of the circulating water pump blade is immediately issued, and within the above limit value, the circulating water pump can be operated.

[Brief description of drawings]

FIG. 1 is a schematic system diagram showing an embodiment of the present invention, FIG. 2 is a system configuration diagram of a control unit for controlling the system of FIG. 1,
FIG. 3 is a diagram showing pump characteristics, FIG. 4 is a diagram showing a relationship between turbine load and pump blade opening, FIG. 5 is a diagram showing a setting example of pump blade opening, and FIG. 6 is an increase in blade opening. It is a figure which shows a state. 4 ... Steam turbine, 5 ... Generator, 8 ... Circulating water pump, 11, 13 ... Circulating water pipe, 16 ... Pump blade opening detector, 17 ... Inlet temperature detector, 18 ... Outlet temperature Detection device, 19 ... Turbine load detector, 20 ... First comparison calculation means, 21 ... Pump blade opening adjustment device, 22 ... Blade opening setting switching device, 23 ... Adder, 25 ... Second comparison calculation means.

Claims (1)

(57) [Claims] 1. A turbine load detector for detecting a steam turbine load and a circulating water pump blade opening for controlling a blade opening of a circulating water pump used in a circulating water system for cooling a steam turbine exhaust of a power plant. Pump blade opening detector to be detected and the detection signals of both detectors are input, and the actual pump blade opening based on the pump blade set opening and the pump blade opening detection signal obtained based on the turbine load detection signal And a first comparison calculation means for calculating a required pump blade opening and outputting a pump blade opening command signal based on the calculated value, and an inlet temperature detection for detecting a system inlet temperature of circulating water. , An outlet temperature detector that detects the outlet temperature of the circulating water, and a temperature detection signal from both of these temperature detectors to obtain the inlet / outlet temperature difference of the circulating water, and the temperature difference is set to a constant limit value. Beyond A second comparison operation means for outputting an opening degree increase command signal for increasing the pump vane opening when the command signal from the first, second comparison operation means inputs,
When the inlet / outlet temperature difference of the circulating water is less than or equal to the limit value, a pump blade opening command signal based on the first comparison calculation means is output, and when the inlet / outlet temperature difference of the circulating water exceeds the limit value, the first comparison is performed. Pump blade opening setting switching means for switching and outputting the added pump blade opening command signal obtained by adding the pump blade opening command signals based on the pump blade opening command signal output from the calculating means at a predetermined ratio, and the pump blade opening setting switching means. And a pump blade opening adjustment device for adjusting the blade opening of the circulating water pump by inputting a pump blade opening command signal output from the degree setting switching means. Pump blade opening control device.