JPS6313081B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a feed water circulation flow rate control device for a energy saver, and more particularly to a feed water circulation flow rate control device for a energy saver in a waste heat recovery boiler in a gas turbine and steam turbine multiple plant.

This type of combined plant is mainly used as an intermediate-load power generation plant, and therefore the boiler is frequently started and stopped. Therefore, when the boiler is stopped for a relatively short period of time (for example, about 12 hours) and then restarted (hot start), the water in the economizer has risen to near the saturation temperature during the previous startup, so the waste heat recovery boiler When the gas flow starts, a steaming phenomenon occurs inside the economizer, causing various troubles.

Therefore, in the past, an operator manually operated a controller to control the circulating flow rate of water to the economizer while monitoring the water supply temperature at the economizer outlet to prevent it from reaching the steaming range. It adjusts in response to changes in feed water temperature, and switches to automatic control when the gas turbine load increases to a certain extent.

If the water supply circulation flow rate controller is set to automatic control from the beginning, the water in the economizer will rise to near the saturation temperature at the time of hot start as mentioned above, and will reach the saturation range immediately after gas flow. This is not desirable from the viewpoint of control stability, as the water circulation flow rate of the energy saver increases rapidly and the temperature drops immediately thereafter, causing a hunting phenomenon in which the water supply circulation flow rate rapidly decreases. do not have.

As mentioned above, in the conventional control system, the operator must manually operate the controller at the time of hot start, and if monitoring is neglected, a steaming phenomenon occurs within the economizer.

The purpose of the present invention is to eliminate the drawbacks of the prior art as described above, to automatically control the water supply circulation flow rate to the economizer from the point of gas passing through the waste heat recovery boiler, and to provide a stable water supply that does not cause the hunting phenomenon. An object of the present invention is to provide a water supply circulation flow rate control device for an energy saver in which circulation is performed.

In order to achieve this object, the present invention provides: a feed water temperature detection means for detecting the feed water temperature at the outlet of the economizer; a feed water circulation flow rate adjustment means for adjusting the amount of water circulation in the economizer; and a drum when the boiler banking is stopped. a drum pressure detector for detecting pressure; a calculation means for setting a preceding water circulation flow rate corresponding to the drum pressure based on a detection signal from the drum pressure detector; Preliminary water supply circulation means that controls the flow rate adjustment means and supplies water corresponding to the preceding water circulation flow rate to the economizer from the start of gas flow to the economizer; and after the water supply circulation by the preceding water circulation means. The present invention is characterized by comprising a control switching means for switching the control of the feed water circulation flow rate by the feed water circulation flow rate adjusting means based on the detection signal from the feed water temperature detection means.

In this way, by temporarily circulating water in the economizer in advance during a hot start, it is possible to detect a feed water temperature close to the true value, which stabilizes the control of the feed water circulation flow rate. Automatic control is possible from the point of gas passing.

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a waste heat recovery boiler in a combined plant of a gas turbine and a steam turbine.

Exhaust gas 1 from a gas turbine (not shown) is
Superheater 2, evaporator 3, energy saver 4 of waste heat recovery boiler
The retained heat is recovered by passing through the superheater 2 sequentially, and the steam generated in the superheater 2 is supplied to a steam turbine (not shown) through a turbine control valve 5.

On the other hand, the condensate 6 discharged from the steam turbine passes through a deaerator 7, a deaerator tank 8, a feed water pump 9, a feed water heater 10, and a feed water flow rate adjustment valve 11 into an energy saver 4.
The water sent to the drum 12 and heated by the economizer 4 is
supplied to

The water circulation flow rate of the economizer 4 is adjusted by a economizer circulation flow rate adjustment valve 13 connected to the water supply pipe between the economizer 4 and the drum 12, and a circulation flow meter 14 is attached to it. ing. 15 is a water supply temperature detector attached to the outlet side of the economizer 4, 16 is a drum pressure detector, 17 is a drum water level detector, and 18 is a can water blow regulating valve.

A water supply circulation flow rate control system for the economizer 4 in the waste heat recovery boiler having such a schematic configuration will be described with reference to the control system diagram in FIG. 2.

As mentioned above, the purpose of controlling the water supply circulation flow rate of the economizer 4 is to prevent the economizer 4 from steaming. For this control, a gas turbine load detector 19 monitors the load state of the gas turbine.
, an atmospheric temperature detector 20 that detects the suction temperature of the gas turbine, a drum pressure detector 16, and a feed water temperature detector 15 that detects the feed water temperature at the outlet of the economizer.
and a circulation flow meter 1 that detects the circulation flow rate of the economizer 4.
Five detection means of 4 are provided.

Based on the detection signal from the gas turbine load detector 19, an arithmetic relay 21 generates a circulating flow rate of feed water for the economizer corresponding to the load of the gas turbine. Third
The figure is a characteristic diagram showing the relationship between the gas turbine load and the economizer feed water circulation flow rate used for this calculation. Since the amount of gas turbine exhaust gas changes depending on the atmospheric temperature, the preceding signal value is corrected by multiplying it by a temperature coefficient in the multiplier 22 upon receiving the detection signal from the atmospheric temperature detector 20, so that the signal does not change suddenly. is inputted to the adder 24 through the change rate limiter 23 .

Based on the detection signal from the drum pressure detector 16, the calculator 25 operates the economizer 4 according to the drum pressure.
The water supply circulation flow rate is calculated, and the result is input to the high value selector 26. The water circulation in this economizer 4 is for temperature detection, and the relationship between the drum pressure and the opening degree of the circulation flow rate adjustment valve (water supply circulation flow rate) is
It looks like the picture.

Further, the detection signal of the drum pressure detector 16 is input to the calculator 27, and it is determined whether or not the steaming region has been reached based on the relationship between pressure and temperature shown in FIG. 5, and the calculation result is used as the set value. It is input to comparator 28. The actual measured value from the feed water temperature detector 15 is input to the comparator 28 and compared with the set value. The comparison result is the switching relay 29, the comparator 28
The deviation amount outputted from the calculation relay 21 is inputted to the adder 24 through a proportional integrator 30 for proportionally integrating the deviation amount to stabilize the control, and the calculation result of the calculation relay 21 is added thereto. This added value becomes the circulation flow rate setting value, and is input to the comparator 32 via the manual/automatic controller 31.

The actual measurement signal from the circulation flowmeter 14 is sent to the square root calculator 3.
3. After passing through a multiplier 34 for temperature correction of the flow rate, it is input to a comparator 32 and compared with the circulating flow rate set value. Note that the measured signal output from the multiplier 34 is also sent to a control system (not shown) of the water supply flow rate regulating valve 11 (see FIG. 1). The deviation amount output from the comparator 32 is proportionally integrated by a proportional integrator 35 in order to stabilize the control, and then the changeover relay 3
6 is output.

The signal generator 37 detects when the boiler banking is stopped and outputs a full close signal that fully closes the economizer circulation flow control valve 13. The full close signal is sent to the signal switching relay 38 and the rate of change. It is input to the switching relay 36 via a change rate limiter 39 for limiting the rate of change. The signal outputted by the switching in the switching relay 36 is given to the economizer circulation flow rate adjustment valve 13 via the automatic/manual operation device 40, and the water supply circulation flow rate is controlled by adjusting the opening degree of the valve. It is becoming more and more like this.

In such a control system, the drum pressure when the boiler banking is stopped is detected by the drum pressure detector 16, and based on the detection signal, the arithmetic unit 25 sets the water circulation flow rate of the economizer 4 corresponding to the drum pressure. be done. Switching relay 3 after gas turbine ignition
8, the water supply circulation flow rate setting signal is sent to the energy saver circulation flow rate adjustment valve 13, and the adjustment valve 13 is adjusted to a predetermined opening degree based on the setting signal, thereby saving the set amount of water. It passes through the charcoal container 4.

This state continues until just before the gas turbine is installed, and at the same time the switching relay 36 operates, the output from the comparator 32 side is sent to the circulation flow rate adjustment valve 13, which prevents steaming from the original energy saving device. Switch to control. and adder 24 as described above.
The comparator 32 compares and calculates the set value outputted from the circulating flow meter 14 with the actual measured value from the circulating flow meter 14, and the opening degree of the circulating flow rate regulating valve 13 is adjusted so as to approach the set value.

Therefore, in the case of this embodiment, the main body of the advance water supply circulation control system is the drum pressure detector 1 in FIG.
6, arithmetic unit 25, high value selector 26, signal switching relay 38, rate of change limiter 39, replacement relay 3
6, automatic/manual operating device 40, energy saving circulation flow rate adjustment valve 13, etc.

Furthermore, the timing of the ignition of the gas turbine and the water supply circulation control of the economizer are almost the same as the timing of the gas turbine ignition and the time of starting gas passage to the economizer (the time of starting the advance water circulation control). moreover,
The time when the gas turbine is installed and the time when the advance water supply circulation flow rate control is switched to the normal water supply circulation flow rate control are almost the same.

Note that when the economizer 4 reaches the steaming region between the gas turbine ignition and the gas turbine joining, this signal is selected preferentially by the high value selector 26, and the circulation flow rate regulating valve 13 is activated by this signal. The opening degree is adjusted.

In the above embodiment, by setting the economizer feed water circulation flow rate within the amount of water held in the deaerator, it is possible to prevent an increase in the amount of dissolved oxygen due to condensate make-up to the deaerator, and also to reduce the amount of water supplied to the deaerator. Pump power can be saved.

The present invention has the above-mentioned configuration, and the water supply circulation flow rate in the economizer is automatically controlled from the time of gas flow, and the hunting phenomenon due to repeated rapid and sudden decreases in the circulation flow rate does not occur, and control is possible. The system is stable.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of a waste heat recovery boiler according to an embodiment of the present invention, Fig. 2 is a diagram of a feed water circulation flow rate control system of the economizer in the boiler, and Fig. 3 is a load setting of a gas turbine. A characteristic diagram showing the relationship between the feed water circulation flow rate, Figure 4 is a characteristic diagram showing the relationship between the drum pressure of the waste heat recovery boiler and the opening degree of the energy saver feed water circulation flow rate regulating valve, and Figure 5 is a characteristic diagram showing the relationship between drum pressure and temperature. FIG. 4... Energy saver, 11... Water supply flow rate adjustment valve, 13
... Economizer circulation flow rate adjustment valve, 14 ... Circulation flow meter, 15 ... Feed water temperature detector, 16 ... Drum pressure detector, 19 ... Gas turbine load detector, 2
0...Atmospheric temperature detector, 36, 38...Switching relay.

Claims (1)

[Scope of Claims] 1. Feed water temperature detection means for detecting the feed water temperature at the outlet of the economizer; Feed water circulation flow rate adjustment means for adjusting the amount of water circulation in the economizer; and detecting drum pressure when boiler banking is stopped. a drum pressure detector; a calculation means for setting a preceding water circulation flow rate corresponding to the drum pressure based on a detection signal from the drum pressure detector; and a water supply circulation flow rate adjustment means based on a setting signal from the calculation means. an advance water supply circulation means which supplies water corresponding to the preceding water circulation flow rate to the energy saver from the start of gas flow to the economizer; and after the water supply circulation by the advance water circulation means; A water economizer feed water circulation flow rate control device comprising: control switching means for switching the control of the feed water circulation flow rate by the feed water circulation flow rate adjustment means based on a detection signal from the feed water temperature detection means.