JPS60218585A - Control device for deaerated steam system in condenser - Google Patents

Abstract

PURPOSE:To control the function of deaeration in the condenser effectively by a method wherein the optimum amount of deaerated air is obtained by operating it by the pressure signal of the condenser, the temperature signal of a hot well and the flow amount signal of feed water. CONSTITUTION:The signals of a pressure originator 31, detecting the pressure of the condenser, a temperature originator 32, detecting the temperature of hot well for the condensor, and a flow amount originator 33, detecting the flow amount of feed water, and taken into a control unit 34, the necessary amount of steam for deaeration in the condenser is operated and the amount of deaerated steam is controlled by the regulating valve 10 of the condenser deaerated steam system 9 based on the operation and the deaerated steam is supplied into condenser 4. In case of a plant, in which the amount of supplementing water is large, the supplementing water 15 for the condenser is detected by a flow amount originator 16, it is taken into the control unit 34, and the obtained necessary amount of steam for deaeration is controlled by somewhat larger value by adding a correcting factor upon increasing of the supplementing water. In case the amount of supplementing water is too much, a tendency to increase the solving oxygen in the condensed water of the hot well is generated, therefore, the amount of deaerated air is increased due to the increase of supplementing water in order to compensate it.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to countermeasures against supercooling of condensate. , relates to a control device for a condenser deaeration steam system suitable for power plants with a large amount of make-up water.

[Background of the invention]

The condenser deaeration steam system is installed as a countermeasure against overcooling of the condenser, and during partial load when the heat load of the condenser decreases,
When the condensate is cooled beyond the performance of the air extractor (i.e., the condensate becomes supercooled relative to the vacuum of the condenser) and dissolved oxygen in the condensate increases, the supercooled condensate is condensed. Heat to the saturation temperature of the chamber vacuum to reduce dissolved oxygen.

A condenser deaerator steam system is used in plants that have a deaerator installed in the water supply system (for example, thermal power plants and PWR type nuclear power plants) to reduce dissolved oxygen in the water supplied to the boiler. There is no need to install it, so
In conventional plants, only some BWR type nuclear power plants have been installed, which do not have deaerators. but,
BWR type nuclear power plants use high-purity pure water as water supply, so oxygen (0%) is used as a rust prevention measure on the reactor side.
2) is injected into the condensate, so the condenser deaeration steam system described above was rarely used in practice.

However, in a combined power generation plant that does not have a deaerator installed, the condenser deaeration steam system becomes an important system, especially when the plant is operated by starting and stopping the plant every day.

In the recently planned large-capacity combined power generation plant, six to seven gas turbines are installed, each gas turbine is equipped with an exhaust gas boiler, and each is equipped with a steam turbine. In this case, only one gas turbine/steam turbine combined unit is operated during low-load operation at night.・An operation method is adopted in which other units are stopped.For this reason, ・In units that are shut down at night, starting and stopping will be performed practically every day.In plants that do not install a deaerator, the boiler (or exhaust gas boiler) The water supply to the plant is carried out from the water stored in the condenser hotwell, so when the plant starts up,
It is necessary to lower the dissolved oxygen concentration of hot well water to below the specified value. When the system is shut down at night, the vacuum in the condenser is broken, so the pressure inside the condenser becomes atmospheric, and oxygen from the air dissolves into the water stored in the hot well, increasing the dissolved oxygen concentration.
Naturally, it is not allowed to send water to the boiler for this purpose. For this reason, when starting up the plant, the stored water in the hot well is recirculated using the feed water recirculation system, and then through the condenser deaeration steam system.

Supercooled condensate is heated and degassed. First, the condenser deaeration steam system is installed as a countermeasure against supercooling of the condenser, and it reduces dissolved oxygen in the supercooled condensate during partial load. Shi, rather,
This reduction of dissolved oxygen before startup is an important function.

Patent Application No. 58-123363 focused on ``changing the amount of degassed steam using seawater temperature and plant load signals'', but the focus was on ``changing the amount of degassed steam using seawater temperature and plant load signals'', but it was Regarding the operation of steam systems, the control system had not yet achieved sufficient controllability.

10,000 Injecting an excessively large amount of degassed steam into the condenser beyond the required amount will not only result in a waste of steam (waste of heat), but also cause partial supersaturation depending on the structure of the condenser. Hot water flows into the water supply pump side and causes cavitation, so in this sense as well, it is desirable to control the amount of degassed steam in the condenser to an optimal value.

[Purpose of the invention]

The purpose of the present invention is to provide a power generation plant without installing a deaerator,
The amount of degassed steam to be input when the frequency of startup and shutdown is high, the condensate dissolved oxygen standard (allowable capacity) during startup and partial load is strict, and the amount of make-up water is large. The purpose of the present invention is to provide a control device that calculates and controls two optimum fans by calculating the hot well temperature signal and water supply flow rate signal, improves economic efficiency, and optimizes the function of condenser deaeration.

[Summary of the invention]

To calculate the amount of degassed steam, subcool the condensate by subtracting the condenser pressure (
It is necessary to determine the amount of steam necessary to heat the product to the saturation temperature (degree of vacuum).

Pc: Condenser pressure (ata) Tsc: Pc' Saturation temperature for VC ('C)
T, ,: Condensate temperature before heating of condenser hotwell ('C
) Enthalpy of condensate (kc at/
' to 9) 1w2: Condensate temperature after heating of condenser hotwell ("C) 1 g 2 a T v Enthalpy of condensate at 2 o'clock ("C)
kca, 4/4) GW: Condensate flow rate - (water supply flow rate) (K
7/H) (value after heating) is e enthalpy of condenser deaeration steam (kca)l
Kq) G8: The required amount of steam for condenser deaeration [K9/H], the required amount of steam for condenser deaeration Gs depends on the heat balance before and after heating. Since the condensate temperature before and after heating in a water heater hotwell is generally about 5 to 40'C, numerically, its enthalpy is equal to y. wl! ;Twl
......Old...Old... (2+
1.2-Tw□・・・・・・・・・・・・・・・・・・
...Mark +31 Also, for the purpose of degassing the condenser, the condensate temperature Tw2 after heating is heated to the saturation temperature '1' s c with respect to the condenser pressure Pc1C, Tw2=Tsc...・・・・・・・・・・・・・・・
(4) Note: Since the saturation temperature 'I'sc cannot be measured directly, the pressure PC of the condenser is measured and calculated. If we express the function as fl(X), Tsc"= fr (Pc)...
...Old... (5) According to the relationship between equations (2) and (5), equation (1) is, as can be seen from equation (6),
The required amount of steam for degassing the condenser Gq is the condenser pressure Pc
The calculated saturation temperature (Tsc = f s (Pc)
), hot well temperature (before heating) T-1, and water supply flow rate G
Billed by w.

It is assumed that the enthalpy 18 of the steam for degassing the condenser is supplied from the auxiliary steam system, and its value is a known value.

The present invention (6) calculates the amount of degassed steam in the condenser,
The aim is to optimally control the amount of heating steam.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
The diagram shows a cast turbine 1, an exhaust gas boiler 2, and a steam turbine 3.
・The schematic system of a combined plant consisting of a condenser 4, a generator 5, and a water supply pump 6 is shown.

In this combined plant, the exhaust gas I of the cast turbine 1 is
A is sent to exhaust gas boiler 2, heat exchanged with feed water 8, and steam 7
The waste residue 2A after heat exchange is released into the atmosphere. After the steam 7 does work in the steam turbine 3, it condenses in the condenser 4 and becomes condensate.The pressure is increased by the water supply pump 6 and the water supply 8.
This constitutes a closed cycle in which waste gas is supplied to the waste boiler 2.

Although FIG. 1 shows one combined unit, in large-capacity combined plants, six to seven units are often combined and operated as one plant.

in this case,? Auxiliary steam header 23 as shown in PJ1 diagram
is often installed common to each unit. The auxiliary steam supply system 21 from each unit is connected to a common auxiliary steam header 23, and the required steam amount is controlled and supplied by a total adjustment valve 22. In FIG. 1, in order to reduce dissolved oxygen in the condensate, the condenser deaeration steam system 9 is taken out from the auxiliary steam header 23 and led to the condenser 4.

The present invention installs a regulating valve 10 in the condenser deaeration steam system 9, and a signal from a pressure transmitter 31 that outputs the pressure of the condenser and a temperature transmitter that detects the temperature of the condenser hot well. 32 and the signal from the flow rate transmitter 33 that detects the feed water flow rate are input to the control device 34, the amount of steam necessary for degassing the condenser is calculated, and then the amount of degassing steam is adjusted by the regulating valve 10. and supplies it to the condenser 4.

According to this embodiment, in order to reduce the dissolved oxygen concentration in the water stored in the hot well of the plant start-up water condenser, the feed water recirculation system 24 is used to circulate the stored water and the flow rate of the feed water recirculation is directed to the recirculation system 24. Even when heating and degassing operation is performed by the condenser degassing steam system 9 (controlled by the installed regulating valve 25), the optimum (minimum required) amount of degassing steam can always be supplied. If the condenser pressure (degree of vacuum), potwell condensate temperature, or water supply flow rate changes during deaeration operation.

As mentioned above, it is always necessary to control the amount of degassed steam to the optimum amount.

The control device 34 in FIG. 1 calculates a valve opening signal 'lt corresponding to the required amount of steam and performs feedforward control.The details are shown in the second diagram. The pressure signal Pc detected by the pressure generation signal 31 is converted into a signal of the saturation temperature Tsc by a function calculator 34.1 (which may be replaced by polygonal line approximation or linear approximation). In addition to the Tsc signal, the temperature signal T- detected by the temperature transmitter 32 (which is composed of a temperature element and a signal converter) is
+ to obtain a signal of (Tsc - T-+).

On the other hand, the subtractor 34.4 subtracts the T911 signal from the degassed steam enthalpy signal (Is) 34.3.

I's Twr) signal. T w 1 compared to is
is sufficiently small, so we omit the subtractor 34.4 and simply write 18
The signal 34.3 may also be used. A divider 34.5 divides the signal from the subtracter 34.2 by the signal B from the subtracter 34.4. obtained by this. Since the signal from the flow rate transmitter 33 is detected as the differential pressure signal ΔP at the flow rate orifice, the square root calculator 34.6
A square root calculation is performed on 1C to obtain a signal G, "k" corresponding to the water supply flow rate.

A multiplier 34.7 multiplies the output signal of the divider 34.5 and the output signal of the square root calculator 34.6 to obtain a signal Gs' corresponding to the required steam amount of the condenser deaerated steam. That is, 34.1~
34.7 calculation units (total sound 34') calculate
) is used to calculate the required amount of steam for deaeration. The function calculator 34.8 obtains a valve control signal (valve opening degree signal) for the regulating valve 10 necessary to flow the required steam latch.

Other embodiments of the present invention are shown in FIGS. 3 and 4. FIG. 3 shows the flow of makeup water 15 to the condenser shown in FIG. The system detects this and inputs it into the control device 34, and when the required amount of steam for sharp air and make-up water determined in FIG. Condenser deaeration is originally
The increase in dissolved oxygen due to supercooling in the condenser is reheated and degassed, but when there is a large amount of make-up water, the amount of dissolved oxygen in the make-up water is large, so the condensate in the hot well section of the condenser is Since dissolved oxygen tends to increase, in order to fully compensate for this, the amount of deaeration steam is increased due to the increase in make-up water, as described above.In Figure 3, the control device fl-35 is used.・This is the control device shown in FIG. 2 with 35.1 to 35.3 added. The differential pressure signal ΔPM of the flow rate transmitter 16 is subjected to square root calculation by the square root calculator 35.11C to obtain a signal GM''k corresponding to the make-up water rate.This GM' and a signal Gy corresponding to the feed water flow rate are obtained.
' into the divider 35.2, and the make-up water rate equivalent signal R
('=GM'/G-') 34', which is the same circuit as in FIG. Then, obtain the device-corrected required steam amount equivalent signal GSR'.

GsR' = Gs' The value of 1 is often set to obtain a certain amount of steam.Gsn
' is input to the function calculator 34.8 to calculate the required valve opening and output a control signal for the regulating valve 10 in the same manner as in FIG.

Figures 2 and 3 are examples of feedforward control, but Figure 4 is an example of full feedback control, in which the amount of steam for deaeration is detected in the condenser deaeration steam system 9. A flow rate transmitter 36 is installed for controlling the flow rate, and the signal is inputted to a control device 37 having the function of a cascade type controller.
The control valve 10 is controlled by the control operation (1). Flow rate transmitter 3
The differential pressure signal ΔPgv of 6 is subjected to a square root calculation using a square root calculator 37.1 to obtain a signal Gsv' corresponding to the amount of steam for deaeration. Similarly to FIG. .

This is multiplied by 2 by the correction coefficient using the proportional calculator 37.2.

Required steam amount equivalent signal G corrected to the signal level of Gsv'
ss"iff is obtained. This is given as a set value to the controller (a combination of 37.3 and 37.4). The subtracter 37.3 calculates the deviation of the input signal Gsv' with respect to the set value Gs4', and thereby the PI The calculation unit (proportional/integral calculation 6) 37.4 performs control calculations, and this is applied to the regulating valve 10 via the manual/automatic switch 37.5 to control the flow rate to be equal to the set flow rate. If applied: Ladder 23 to the auxiliary steam in Figure 1
This has the advantage of being able to input the necessary amount of steam for degassing the condenser even if the pressure fluctuates. Although FIG. 4 shows an example in which the control method shown in FIG. 2 is changed to feedback control, it is obvious that the control method shown in FIG. 3 can be changed to full feedback control.

〔Effect of the invention〕

According to the present invention, even when the feed water flow rate (condensate flow rate) and the degree of supercooling of the condenser real well section change.

The optimum amount of steam for deaeration can be input at all times, and the effect is noticeable during deaeration of hot well stored water at plant start-up.

[Brief explanation of the drawing]

FIG. 1 is a schematic system diagram of a caster turbine/steam turbine combined plant according to an embodiment of the present invention. FIG. 2 is a control system diagram of a condenser deaeration steam system according to the present invention. FIGS. 3 and 4 are control system diagrams of other embodiments of the present invention. 31...Pressure transmitter, 32...Temperature transmitter・16.
33...Flow rate transmitter, 34, 35.37...Control device. Agent Patent Attorney Akio Kachihashi Daisan Kasumi

Claims (1)

[Claims] 1. In a steam turbine power plant equipped with a deaeration steam system for a condenser to reduce dissolved oxygen in water supplied to a boiler, the pressure signal of the condenser and the hot well A condenser deaeration steam system characterized by comprising means for calculating the amount of steam required for deaeration of the condenser based on a temperature signal and a feed water flow rate signal, and a means for controlling the amount of deaeration steam based on the calculation means. System control device. 2. In claim 1, there is provided means for correcting the required steam t=li= based on the makeup water flow rate signal and controlling the required steam amount to increase when the makeup water increases. A control device for a condenser deaeration steam system characterized by: