JPH01276302A - Water supply controller - Google Patents

Abstract

PURPOSE:To ensure the stable control of water supply even in case the temperature of the exhaust gas supplied to an exhaust heat collecting heat exchanger is suddenly changed by cutting off the rotational frequency signal produced based on three elements and supplied to a driving device and supplying newly the rotational frequency signal obtained based on the temperature change rate. CONSTITUTION:A water supply pump 13 contains a driving device 14 and the rotational frequency of the pump 13 is controlled by the control signal produced based on three elements during a normal operation. In case the temperature of the exhaust gas flowing to an exhaust heat collecting heat exchanger 1 rises up and this temperature change rate exceeds a prescribed level, the supply of the rotational frequency signal is cut to the device 14. Then the device 14 is controlled by a new rotational frequency signal obtained through a prescribed arithmetic operation carried out based on the temperature change rate of the exhaust gas. As a result, the rotational frequency of the pump 13 increases and the water supply pressure is increased to a fuel economizer 2. Thus the supplied water never evaporates at a place near the outlet of the economizer 2.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a combined cycle power generation plant or a combined heat generation β-type plant, and more specifically, to a combined cycle power generation plant or a combined heat generation β type plant, and more specifically, to The present invention relates to a water supply control device used to maintain high pressure of water supply and stabilize water supply control under transient operating conditions.

(Prior art) In combined cycle power plants and combined heat and power generation plants, exhaust heat recovery heat exchangers are used that use exhaust gas from gas turbines, etc., as a heat source to generate driving steam for steam turbines and steam or hot water for processes. . As a typical example of this exhaust heat recovery heat exchanger, one applied to a combined cycle power plant will be taken up, and the conventional technology will be explained with reference to the drawings.

That is, in FIG. 2, the exhaust heat recovery heat exchanger 1 has a heat exchange section consisting of a economizer 2, an evaporator 3, and a superheater 4 in order to efficiently exchange heat with the exhaust gas. At this time, the supplied water flows in the order of the economizer 2, the evaporator 3, and the superheater 4, during which it absorbs heat from the exhaust gas and undergoes a phase change from saturated steam to superheated steam.

On the other hand, the temperature of the exhaust gas decreases while flowing from the superheater 4 to the economizer 2, and is discharged into the atmosphere through an exhaust gas tact (not shown).

In addition, the exhaust heat recovery heat exchanger 1 is provided with a steam drum 5, in which feed water heated by the energy saver 2 is stored, and canned water (saving water) is provided between the evaporator 3 and the steam drum 5. Charcoal maker 2
The water (supplied water that has been heated to become saturated water) is circulated.

On the other hand, steam generated in the superheater 4 is led to a steam turbine 7 via a live steam pipe 6, where it expands and performs work. At this time, the generator 8 is turned and electrical output is taken out. Further, the exhaust gas of the steam turbine 7 is discharged to a condenser 9, where it is cooled by cooling water and becomes condensed water. Thereafter, condensate is extracted from the condenser 9 by a water supply pump 10 and supplied to the energy saver 2 as water supply. Note that the reference numeral 1] in the figure represents a control valve for adjusting the flow rate of water supply, and the reference numeral 12 represents a gas turbine.

(Problems to be Solved by the Invention) By the way, the above-described water supply control system of the exhaust heat recovery heat exchanger is based on three-element control of the water level of the steam drum 5, the water supply flow rate, and the steam flow rate.

That is, the control deviation between these detected values and the target water level and flow rate is determined by the controller, the opening degree of the control valve 11 is changed by the control signal output from the controller, and the water supply amount is adjusted. adjusted. However, the heat source of the exhaust heat recovery heat exchanger is the exhaust gas of the gas turbine 12,
This method may not be effective due to sudden changes in exhaust gas temperature. For example, when the temperature of the exhaust gas rises rapidly, part of the feed water flowing into the steam drum 5 evaporates because the feed water that has reached the vicinity of the outlet of the economizer 2 has been heated close to its pressure saturation temperature. The water level in the steam drum temporarily rises. The water level gauge works to respond to this rise in water level.
The opening degree of the control valve 11 is reduced in the direction of decreasing the amount of water supplied, but this increases the evaporation action within the steam drum 5, which is the opposite of the control operation that should increase the amount of water supplied. Correspondingly, water supply control becomes temporarily unstable.

Furthermore, when a portion of the feed water evaporates near the outlet of the energy saver 2 due to the temperature change of the exhaust gas mentioned above, a large amount of air bubbles will be included in the feed water, making the flow of the feed water extremely unstable. . In this case, if the water supply pressure increases while the air bubbles are not removed from the water supply, a water hammer phenomenon will occur in a wide area from the economizer 2 to the steam drum 2, causing damage to the equipment. There is a possibility that you will receive it.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a water supply control device that can maintain stable water supply control even when the temperature of exhaust gas supplied to an exhaust heat recovery heat exchanger fluctuates rapidly.

[Structure of the Invention] (Means for Solving the Problems) The water supply control device according to the present invention includes a variable speed drive device attached to a water supply pump that pressurizes and sends water supply to the economizer of the exhaust heat recovery heat exchanger. , a control valve that adjusts the flow rate of water supplied to the economizer by changing the valve opening, the detected steam drum water level of the exhaust heat recovery heat exchanger, the flow rate of water supply supplied to the economizer, and the exhaust heat. A device that calculates a control deviation based on three elements of the steam flow rate flowing from the recovery heat exchanger to the steam turbine and generates a rotation speed signal for the feed water pump drive device and an opening degree signal for the control valve, and an exhaust heat recovery heat exchanger. A predetermined calculation is performed based on the temperature change rate of the exhaust gas flowing through the
A device that generates a rotation speed signal for the drive device, and a device that provides a rotation speed signal based on three elements to the drive device when the rate of temperature change of the exhaust gas flowing into the exhaust heat recovery heat exchanger is less than a predetermined value. , a device that cuts off the rotational speed signal based on the three elements to the drive device when the temperature change rate of the exhaust gas exceeds a predetermined value, and provides a rotational speed signal based on the temperature change rate. It is something.

(Function) The water supply pump is provided with a variable speed drive device, and during normal operation, the rotation speed of the water pump is controlled by control signals generated based on the conventional three elements. When the temperature of the exhaust gas flowing into the exhaust heat recovery heat exchanger rises and the temperature change rate exceeds a predetermined value, the above rotation speed signal to the drive device is cut off, and a predetermined calculation is performed from the temperature change rate of the exhaust gas. The control is switched to the rotational speed signal obtained by performing the following steps. As a result, the rotation speed of the water supply pump increases, the pressure of the water supply entering the economizer is increased, and the water supply is prevented from evaporating near the outlet of the economizer.

(Example) An example of the present invention will be described with reference to FIG. In addition,
In the figure, the same components as those shown in FIG. 2 are denoted by the same reference numerals, and the explanation thereof will be omitted.

In FIG. 1, numeral 13 indicates a water supply pump,
This water supply pump] 3 is equipped with a variable speed drive device, for example, a variable speed electric motor 14, so that its speed (rotation speed) can be changed arbitrarily.

The following two control signals are guided to the variable speed electric motor 14. That is, the first control signal is a signal output from the conventionally used controller 15, and is a signal output from the steam drum 5.
A water level signal given from [water level transmitter] 6,
A control signal is generated based on three elements: a flow rate signal derived from a flow rate transmitter 17 provided in the main steam pipe 6 and a flow rate signal given from a flow rate transmitter 18 provided on the discharge side of the water supply pump 13. It is designed to be guided through. Further, the second control signal is a signal newly added in this invention, and is based on the temperature signal given from the temperature transmitter 20 provided in the exhaust gas duct that guides the exhaust gas of the gas turbine 12, and is sent to the computing unit 21. The rate of temperature change is determined, further converted into a pump rotation speed by a function generator 22, and provided via a contact 23.

Further, the output of the calculator 21 is led to a comparator 24 where it is compared with a rate of change setting signal. When the temperature change rate from the computing unit 2 exceeds the change rate setting signal, a control signal for switching from the contact 19 side to the contact 23 side is output to the signal switch 25.

On the other hand, No. 71 26 indicates a full-open setting device that keeps the opening degree of the control valve 11 fully open, and a control signal from this full-open setting device 26 is guided to the drive section of the control valve 1 via a contact 27.

In addition, a control signal from a controller 15 configured in the same manner as in the prior art is applied to the drive section of the control valve 11 via a contact 28. And a rotation speed transmitter 2 provided in the water supply pump 13
9, a control signal 141 is applied to the signal switch 30 to switch from the contact 28 side to the contact 27 side when the rotation speed exceeds a certain value.

Next, the operation of the water supply control device configured as described above will be explained.

During normal operation, the exhaust gas temperature of the gas turbine 12 is constant, and the temperature change rate calculated by the calculator 21 is smaller than the setting signal given to the comparator 24, and at this time, the signal switch 25 switches the contact 19 to close. are doing. Therefore, the variable speed electric motor 14 is controlled by control signals based on three elements given from the controller 15. At this time, the rotational speed of the water supply pump 13 is approximately constant, and the opening degree of the control valve 11 is also constant.

On the other hand, if the exhaust gas temperature of the gas turbine 12 changes suddenly due to, for example, an increase in fuel added to the combustor (not shown), the rate of temperature change output from the calculator 2 to the comparator 24 changes suddenly. . When this exceeds the set signal of the comparator 24, a control signal is output to the signal switch 25, and at the same time as the contact 19 is opened, the contact 23 is closed.

For this purpose, a function generator 22 that outputs a rotation speed signal according to the rate of temperature change determined by the calculator 21 and the variable speed electric motor 4 are connected via a contact 23, and the rotation speed signal is proportional to the rate of temperature change, for example. An increasing rotational speed signal is output to the variable speed electric motor 14, which causes the water supply pressure to be higher than before. This increase in water supply pressure suppresses the evaporation of the feed water at the outlet of the energy saver 2, lowers the temperature of the feed water conveyed to the steam drum 5, and as a result, the evaporation of canned water is also suppressed, and the water level of the steam drum 5 can also be controlled. It remains stable.

Further, a rotation speed signal is output to the variable speed electric motor 14, and when the rotation speed of the water supply pump 13 increases and exceeds a certain rotation speed, a control signal is output from the rotation speed transmitter 29 to the signal switch 30, and the contact 28 is opened and at the same time contact 27 is closed. Therefore, the control signal that was being output from the controller 15 to the control valve 11 is cut off, and as an alternative control signal, a control signal to keep the control valve 11 fully open by the full open setting device 26 is sent to the contact 27. given through. That is, in the three-element control, when the temperature of the exhaust gas changes rapidly, there is a risk that the control operation will be reversed in order to maintain stable water supply control, so the control signal is rejected for a certain period of time. When this method is not used, that is, when the rotational speed of the water supply pump 13 is not used, a timer is used to provide a time period in which the three-element control is moved away, and during that time, the opening degree of the control valve 11 is kept fully open. Good too.

It should be noted that the larger the above-mentioned increase in water supply pressure is, the more effective it is, but if it is exceeded, the efficiency of the plant decreases because it relies on internal power. Therefore, the pressure rise is approximately 10 kg/more than the saturation pressure of the feed water temperature at the exit of the economizer 2 at that time.
The upper limit is set to a value about cd higher.

Further, since the temperature change of exhaust gas differs from the rate of change during the startup and shutdown processes from that during normal operation, different consideration is required. For example, an output to the signal switch 25 may be generated only when the output of the comparator 24 continues for a certain period of time.

Further, although the above embodiment is an example in which the variable speed electric motor 14 is applied, a fluid coupling, an automatic transmission device, etc. combined with the prime mover can be applied to control the rotation speed of the water supply pump 13.

[Effects of the Invention] As explained above, in the present invention, even when the temperature of the exhaust gas fluctuates rapidly, the rotation speed of the water supply pump is increased by the rotation speed signal generated based on the rate of change in temperature of the exhaust gas.
Therefore, it is possible to increase the pressure of the water supply entering the economizer, and it is possible to prevent the water supply from evaporating near the outlet of the economizer.

Therefore, according to the present invention, the water supply control in the exhaust heat recovery heat exchanger can be stably maintained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a water supply control device according to the present invention, and FIG. 2 is a system block diagram showing a water supply system of an exhaust heat recovery heat exchanger according to the prior art. 1...Exhaust heat recovery heat exchanger 2...
... Economizer 3 ... Evaporator 4 ... Superheater 5 ... Steam drum 11 ... ...Control valve 13...Water pump 14...Variable speed electric motor 15...Controller 20... Temperature transmitter 21... Arithmetic unit 22... Function generator 24... Comparator 25.30... Signal switch 26.・・・・・・Full open setting device 29・・・・・・Rotation speed transmitter

Claims (1)

[Claims] A variable speed drive device attached to a water supply pump that pressurizes and sends water to the economizer of the exhaust heat recovery heat exchanger, and an adjustment that adjusts the flow rate of the water supply sent to the economizer by changing the opening degree of the valve. valve and
A control deviation is determined based on three elements: the detected steam drum water level of the exhaust heat recovery heat exchanger, the flow rate of water supplied to the economizer, and the flow rate of steam flowing from the exhaust heat recovery heat exchanger to the steam turbine. , a device that generates a rotation speed signal for the drive device of the water supply pump and an opening signal for the control valve, and a device that performs a predetermined calculation based on the rate of temperature change of the exhaust gas flowing into the exhaust heat recovery heat exchanger, a device that generates a rotation speed signal for the device; and a device that provides a rotation speed signal based on three elements to the drive device when a temperature change rate of the exhaust gas flowing into the exhaust heat recovery heat exchanger is less than a predetermined value; On the other hand, it is characterized by comprising a device that cuts off the rotation speed signal based on the three elements to the drive device when the temperature change rate of exhaust gas exceeds a predetermined value, and provides a rotation speed signal based on the temperature change rate. water supply control device.