JPH0518506A - Feed water controller - Google Patents

Abstract

PURPOSE:To check an amount of water feed of a trip boiler so that the water feed of other sound boilers is lowered when one boiler trips in a plurality of drum boiler equipment and equipment having a common water feed system. CONSTITUTION:A plurality of gas turbines 1 and exhaust heat recovery boilers 3 are arranged in systems A and B respectively and equipment comprising a water feed system is provided having a water feed pump 8 common to the above parts. A circuit 9 is provided to check a command for opening a water feed flow control valve 6 of boilers when the inputting of heat into one boiler is interrupted (boiler tripping).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to commercial thermal power or industrial thermal power generation equipment.

[0002]

2. Description of the Related Art In a conventional drum boiler facility, the opening of a feed water flow rate control valve of a water feed system is adjusted so as to maintain a drum level and a specified value.

A known example is the thermal power nuclear power generation Vol. 38
NO. 5 As shown in the control system diagram of P509,
The feed water control valve only receives the signal from the drum level.

The normal boiler equipment has one water supply system for one boiler, and it suffices to adjust the water level at the corresponding drum level exclusively.

However, in a facility having a common water supply system for a plurality of boiler facilities, it is necessary to be careful so that when one of the boiler facilities is abnormal, the other normal boiler facility is not disturbed.

In particular, when the heat input to one of the boilers is suddenly cut off, the boiler drum level suddenly drops, and the level control temporarily increases the amount of water supply.

Therefore, there is a possibility that the water supply amount to the other normal boiler equipment may not be sufficiently supplied, and the normal boiler equipment may have to be stopped.

[0008] By the way, conventionally, there has never been a plant facility configuration having a common water supply system for a plurality of boiler facilities, but the common system has been designed to have a sufficient capacity.

However, in a large capacity combined plant,
High-pressure and low-pressure two drums of one boiler equipment, and high pressure,
With a configuration with three drums of medium and low pressure, the disturbance of the water supply system when the heat input to the boiler is cut off has become extremely large.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a water supply control of a plant having a plurality of drum boiler facilities and a common water supply system, particularly a large capacity combined plant having a plurality of drums in one boiler facility. In the case of a boiler equipment trip due to the cutoff of heat input to the equipment, the amount of water supplied to the boiler equipment is temporarily limited so that normal operation of the boiler equipment is not interrupted.

[0011]

In order to achieve the above object, the present invention detects a heat input cutoff of a boiler, that is, a condition of a boiler trip, and according to the condition, an opening command of a feed water flow rate control valve of the boiler, Alternatively, a circuit for suppressing the feed water flow rate command is provided.

[0012]

[Operation] By suppressing the supply flow rate of the tripped boiler installation from becoming excessive, the required supply flow rate of the boiler installation on the normal side is secured.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the system configuration according to the present invention, in which the combination of gas turbine and exhaust heat recovery boiler is A, B.
It consists of two series and a steam turbine and water supply system common to both series.

Exhaust gas from the gas turbine 1A is guided to an exhaust heat recovery boiler 3A via an exhaust duct 2A, heats feed water and steam, and supplies steam to the steam turbine 7.

The water level of the drum 4A, which is a drum type boiler, is normally controlled by the feed water flow rate control valve 6A via the level controller 5A so as to reach a prescribed level set value.

The water supply to the boiler is supplied by the water supply pump 8 of the water supply system common to the A and B series, but due to the facility capacity, there is a margin in the required water supply flow rate during the rated operation of the A and B series boilers. It is designed so that the specified flow rate is the maximum water supply flow rate. For this reason, when two series co-operation is performed, even if an abnormality occurs in one boiler and the supply water flow rate is disturbed, the total water supply flow rate of the two series will not exceed the supply capacity of the common water supply system.
Have to be driven.

In FIG. 2, when the steam turbine system was operating for two gas turbines and two exhaust heat recovery boilers,
The fluctuation characteristics of the drum level and the feed water flow rate of the A and B systems when the A system gas turbine 1A trips at time t = te are shown.

The solid line shows the variation characteristic of the conventional control method.

That is, since the heat input to the A-system exhaust heat recovery boiler 3A rapidly decreases at the special time t = te, the level of the A-system drum 4A tends to rapidly decrease as shown by L _Aα . On the other hand, the level control device 5A of the drum 4A rapidly opens the water supply flow rate control valve 6A of the A system, and the water supply flow rate to the A system drum sends a large amount of water to the drum 4A as indicated by Q _Aα. , Suppress the decrease in level. Due to the movement of the A system, the feed water flow rate Q _Bα of the B system decreases, and the B system drum 4
The level of B also decreases as shown by L _Bα .

Since the heat input to the A-type boiler is drastically reduced, there is no danger of overheating and burning even if the drum level is lowered, and there is no problem even if water supply is generally suppressed.

On the other hand, the B system must be able to continue operation, and in that sense, fluctuations in the drum level should be suppressed to a minimum.

The broken line in FIG. 2 shows a countermeasure for the above problem. In other words, at time t = te, the heat input of the exhaust heat recovery boiler 3A is sharply reduced, and even if the level of the drum 4A is reduced and the required amount of water supply is increased, it is possible to prevent the supply water flow rate of the tripped boiler from increasing more than necessary. Control like Q _Aβ . As a result, the level fluctuation of the B system drum 5B is Q
It can be suppressed like _Bβ .

FIG. 3 is an example of a control circuit showing this measure, in which a feed water flow rate control valve opening suppressing circuit 9 is provided on the output side of a conventional level controller 5.

Gas turbine or boiler trip signal 1
When 4 is turned on, the suppression opening signal 13 is selected, and the low value selection circuit 10 suppresses the valve opening signal.

FIG. 4 shows another example of measures for suppressing the opening of the feed water flow rate control valve. That is, in the control circuit that calculates the deviation between the feed water flow rate command signal which is the output signal of the level controller 5 and the actual feed water flow rate signal 19 by the controller 18 and adjusts the opening degree of the control valve 4, the feed water flow rate command signal suppression circuit 15 is used. It is provided.

Similar to FIG. 3, the signal switching unit 20 selects the suppression flow rate signal 22 at which the trip signal 14 of the gas turbine or the boiler is turned on, and the low value selection circuit 16 suppresses the flow rate command signal.

In FIG. 1, an example of one drum for one boiler is shown for simplification of description. However, there is a recent large capacity combined plant having one or two boilers in one boiler facility. In such a plant, when the heat input to the boiler is cut off, the opening of the feed water flow rate control valve of each of the two or three drums is suppressed.

[0028]

According to the present invention, when an abnormality such as heat input interruption of one boiler occurs, a large disturbance is not given to the water supply system of the other boiler, and the expansion of the accident can be prevented.

[Brief description of drawings]

FIG. 1 is a system diagram of equipment having a plurality of drum boiler equipments and a common water supply system.

FIG. 2 is an explanatory diagram showing a comparison between a case where the present invention is not adopted and a case where the present invention is adopted, regarding the response characteristics of the drum level and the feed water flow rate of two boilers.

FIG. 3 is a circuit diagram of a feed water flow rate control valve opening degree suppression circuit of the drum level control device.

FIG. 4 is a circuit diagram of a water supply flow rate command suppression circuit of a drum level control device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Gas turbine, 2 ... Exhaust gas system, 3 ... Exhaust heat recovery boiler, 4 ... Drum, 5 ... Drum level controller, 6 ... Water supply flow rate control valve, 7 ... Steam turbine, 8 ... Water supply pump, 9 ...
Supply water flow control valve opening control circuit.

Claims (2)

[Claims] Claim: What is claimed is: 1. A boiler facility having a drum and a water supply control valve provided upstream of the drum, comprising a plurality of units and a facility for supplying water as a common system to the plurality of boilers. A water supply characterized by having a circuit that suppresses the opening of the feed water flow rate control valve of the boiler in which an abnormality has occurred by a signal that detects that the heat input gas of the boiler has been cut off due to an abnormality in equipment related to the boiler equipment. Control device. 2. The water supply control device according to claim 1, wherein a circuit for suppressing a water supply flow rate command signal is provided as means for suppressing the opening degree of the water supply flow adjustment valve of the boiler.