JPS5981402A - Controller for water level of deaerator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water level control device for a deaerator in a thermal or nuclear power plant.

FIG. 1 schematically shows a power generation plant, in which reference numeral 1 is a deaerator, 2 is a deaerator water storage tank, 3 is a feed pump, 4.5.6.7.8 is a pipe, 9 10 is a deaerator water level detector, 10 is a deaerator water level controller, 11 is a deaerator water level control valve, 12 is a deaerator pressure detector, 13 is a deaerator pressure controller, 14 is a deaerator pressure Control valve, 15, feed water heater, 16
1 is a steam generator, 17 is a steam control valve, 18 is a steam turbine, 19 is a condenser, 20 is a condensate pump, 21 is a generator, 2
2 is a breaker.

The condensate sent to the deaerator 1 through the pipe 4 is fed to the feed water heater 1
5, it is heated by the turbine extraction steam brought in through the pipe 5 and then sent to the deaerator 1. In deaerator 1,
The condensate sent through piping 4 is heated and degassed by turbine oil vapor supplied through piping 6. The heated and degassed condensate is stored in the deaerator water storage tank 2 at any time. The water supply pump 3 sends condensate stored in the deaerator water tank 2 to the steam generator 16 via a pipe 8. steam generator 1
The steam generated at 6 is supplied to a turbine 18 via a turbine steam control valve 17. The steam leaving the turbine is condensed in a condenser 19. Condensate in the condenser 19 is pressurized by a condensate pump 20 and supplied to the deaerator 1 via piping 4. The deaerator water level control valve 11 detects the deaerator water level with the deaerator water level detector 9, and based on this, performs necessary calculations with the deaerator water level controller 10 to keep the deaerator water level constant. It is controlled so that The deaerator pressure detector 12, the deaerator pressure controller 13, and the deaerator pressure control valve 14 constitute a control system that maintains the deaerator pressure at a predetermined value or higher.

In the plant shown in FIG. 1, during normal operation, the deaerator 1 performs the following functions. That is, fa) The feed water supplied to the steam generator 16 is heated and degassed.

Q is the condensate flow rate supplied from pipe 4. , calculate the enthalpy. , measure the flow rate of bleed air brought in from piping 6, and calculate the enthalpy ■. Then, holds true. Rice is Q. , Q8 is the enthalpy of the fluid after being mixed, that is, the enthalpy of the condensate in the deaerator storage tank. In the deaerator 1, the water is heated to the enthalpy of saturated water to remove dissolved oxygen and the like.

(bl Effective suction head of water supply pump ('NPSH)
ensure that

The water supply pump 3 sends the necessary water supply to the steam generator 16,
The water to be delivered is saturated water, and is installed higher than the water supply pump to ensure an effective suction head to prevent pump cavitation. Conceptually, the following formula is satisfied.

P = P + rHa'vplH (21PIN
D T'1 work, <f (PP work N) +31 Here, PP work is the picture book pump inlet lower blade, TP work 1. is the water supply pump inlet temperature, PD is the deaerator internal pressure, H is the height from the water supply pump to the deaerator water level, γ is the specific weight of condensate,
Vp is the flow velocity at the pump inlet, α' is the coefficient, f(PP
PP) is the saturated water temperature for PP.

If the circuit breaker 22 opens for some reason while the plant shown in FIG. 1 is generating power, the turbine 18 will be in a nearly no-load operating state and the steam control valve 17 will quickly close. As a result, the oil gas supplied to the deaerator 1 and the feed water heater 15 via the piping 5.6 rapidly decreases (2J type construction, Q
F, I8 becomes smaller and the ID of condensate in the deaerator water storage tank
The ID of the deaerator 1 is smaller than that of the deaerator 1. That is, the deaerator internal pressure PD becomes unable to maintain the saturation pressure for the deaerator water storage tank. As a result, equation 13) becomes unsatisfied, cavitation occurs in the pump, and the plant cannot continue operating.

An auxiliary heating system is provided to prevent this.

That is, heated steam is directly supplied from the steam generator 16 to the deaerator 1 through the pipe 7. Heating steam is supplied by the deaerator pressure detector 12, deaerator pressure controller 13, and deaerator pressure control valve 14 when the deaerator RYE force falls below a predetermined pressure, but there are restrictions due to equipment. cannot be fully covered by
In some cases, it may become impossible for the plant to continue operating.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to ensure an effective suction head of a water supply pump without changing the conventional control device to a large RL.

According to the present invention, an index for the saturation temperature of the feed water pump inlet fluid is obtained from the deaerator internal pressure, and the actually measured water pump inlet fluid temperature is compared with this index, and the deaerator condensate flow rate is determined as necessary. A deaerator water level control device is provided that has the function of ensuring the effective suction head of the water supply pump by adjusting the .

A preferred embodiment of the present invention illustrated in FIG. 2 will be described in detail below. FIG. 2 shows details of the water level control device of the deaerator 1, and the parts surrounded by the dashed line in the figure are the parts changed according to the present invention.

In FIG. 2, elements that are the same as those in FIG. 1 are designated by the same reference numerals.

In Fig. 2, reference number I is a deaerator, 2 is a deaerator water storage tank, 3 is a water supply pump, 4.5.6.7.8 is a pipe, 9 is a deaerator water level detector, and 101 is a deaerator. Air water level setting device,
102 is a subtractor, 103 is a regulator, 11 is a deaerator water level control valve, 12 is a deaerator pressure detector, 131 is a deaerator pressure setting device, 132 is a subtracter, 133 is a regulator, 14 is a deaerator Air pressure control valve, 23 is a water supply pump inlet water supply temperature detector, 2
4 is a function generator, 25 is an adder, 26 is a bias setter, 27 is a subtracter, 28 is a function generator, and 29 is an adder.

To ensure the effective suction head of the water supply pump 3.

It is sufficient if the above formula (3) is satisfied under various operating conditions.

In the control device shown in FIG. 2, the deaerator internal pressure PD opened by the deaerator pressure detector 12 and the bias setting device 26
Accordingly, the adder 25 adds the bias corresponding to γH−αFvP(N′) in Equation (2) and inputs it to the function generator 24, and the function generator 24 calculates f(PP□9) in Equation (3). is output to the subtracter 27. The water supply pump inlet feed water temperature TPIN in equation (3) is detected by the detector 23 and output to the subtractor 27 . The subtracter 27 obtains TP, -f (PP, 1.), and when this value is positive, the function generator 28 generates a negative signal, which is input to the adder 29. This value input to the adder 29 apparently lowers the setting value of the deaerator water level setter 101, and as a result, the water level control valve 11 is throttled to reduce the condensate flow rate Q supplied to the deaerator 1. Reduce. Therefore, the rate of decrease in the pressure inside the deaerator becomes gradual, and the effective suction head can be secured.

When the breaker 22 opens during normal operation and the steam turbine 18 shifts to a no-load operating state, the heating steam to the deaerator 1 and the feedwater heater 15 rapidly decreases. Conventional deaerator water level control devices keep the water level constant regardless of the deaerator pressure, so the deaerator pressure decreases rapidly, and if left as it is, it will no longer satisfy equation [3], resulting in Leading to water pump tripping.

According to the present invention, in cases such as the above-mentioned no-load operation, the deaerator water level set value is automatically corrected so as to satisfy equation (3), and the condensate flow rate Q supplied to the deaerator 1 is adjusted. It acts to temporarily narrow down the When the equation (3) is satisfied, the water level is controlled to the original water level setting value, and normal control is resumed. In this way, in the present invention, the plant can continue to operate without the water supply pump 3 tripping.

Although the present invention has been described in detail with reference to a preferred embodiment thereof, the present invention is not limited to this particular embodiment, and may be modified in many ways within the spirit of the invention.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing a power generation plant to which the device of the present invention is applied, and FIG. 2 is a diagram illustrating the device according to the present invention. 1... Deaerator, 2... Deaerator water storage tank, 3... Water supply pump, 4, 5, 6, 7, 8... Piping, 9... Deaerator water level detector, 10... Deaeration 11. Deaerator water ridge control valve, 12. Deaerator pressure detector, 13. Deaerator pressure controller, 14. Deaerator pressure control valve, 15.-・
Feed water heater, 16... Steam generator, 17... Steam control valve, 18... Steam turbine, 19... Condenser, 20... Condensate pump, 21... Generator, 22... Breaker, 23・
・Water pump inlet feed water temperature detector, 244 parameters ・Function generator, 25...Adder, 26...Bias setting device, 27.
・Subtractor, 28...Function generator, 29...Adder, io
i... Deaerator water level setting device, 102... Subtractor, 103...
- Regulator, 131... Deaerator pressure setting device, 132... Subtractor, 133... Regulator. -mi

Claims (1)

[Claims] A device that calculates the saturated water temperature of the feed water pump inlet fluid from the pressure inside the deaerator, a device that compares the calculated saturated water temperature and the actually determined feed water pump inlet fluid temperature, and a device that calculates the saturated water temperature of the feed pump inlet fluid from the deaerator internal pressure, and 1. A deaerator water level control device, comprising: a device for correcting a deaerator water level set value.