JP3199851B2 - Water quality adjustment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water quality control device for a condensate supply system in a power plant, for example.

[0002]

2. Description of the Related Art In domestic thermal power plants, condensing, supplying water, adjusting and treating the quality of boiler water and steam in a system to minimize corrosion in the system, and at the same time, boiler water pipes, steam pipes and the like. Prevents scale from adhering to feed water pump suction strainer.

Here, when the boiler is of a once-through type, ammonia (NH ₃ ) and hydracine (N ₂ H) are contained in the condensate water supply system.
₄ ) Volatile substance treatment (hereinafter referred to as A)
VT method) is performed, and by this processing, the PH value is controlled to “9 to 9.5” and the oxygen content is controlled to be deoxygenated.

However, in this AVT method, a high ammonia concentration (PH> 9.
However, in this case, ammonia damage (ammonia attack) occurs in the ammonia concentrating unit in the plant, for example, the air cooling unit of the condensate air, and anticorrosion measures using high-concentration ammonia cannot be performed.

[0005] For this reason, the reducing effect of hydracine appears, and iron is eluted from the carbon steel in the plant into the condensate and water supply systems, and this iron adheres to the boiler water pipe, steam pipe, feed water pump suction strainer, etc. The thickness will be increased. Therefore, this iron must be removed at an appropriate time, which is a major obstacle in plant operation planning. If the attached iron is not removed, there is a possibility that the water pump will be overloaded and the boiler tube will be cracked.

However, in order to improve the disadvantages of the AVT method, a combined neutral water treatment (hereinafter, referred to as a CWT method) for injecting ammonia and oxygen (O ₂ ) into a condensate water supply system has been performed in recent years. . This CWT method makes the system weakly alkaline and injects oxygen to deposit iron oxide on the boiler water pipe, steam pipe and feed water pump suction strainer,
This significantly reduces carry-on.

FIG. 4 is a configuration diagram of a water quality adjusting apparatus to which the CWT method is applied. The condenser 1 is supplied with exhaust steam of a turbine in a plant and a heater drain, and the condenser 1 is condensed by exchanging heat between the exhaust steam of the turbine and the like with seawater as a cooling medium. You. This condensate passes through a condensate desalination device 4 and a low-pressure feed water heater 5 by the operation of a condensate pump 2 and a condensate booster pump 3, and a deaerator 6.
Sent to At this time, the condensate desalination apparatus 4 removes suspended solids such as iron oxide and dissolved solids such as chloride ions in the condensate to perform system regeneration.

[0008] The deaerator 6 releases oxygen contained in the condensate by bringing heated steam into contact with the condensate, and sends the deaerated water to a water supply system. Specifically, the deaerator 6 has a configuration shown in FIG. 5, and the deaerator 6 includes a deaeration chamber 6-1 and a water storage tank 6.
-2. The deaeration chamber 6-1 includes a deaeration tray 6-3, a flow pipe 6-4 for heated steam, an injection valve 6-5 for introducing condensate, and a discharge pipe 6-6 for releasing oxygen to the atmosphere.
6 and its vent valve 6-7. With such a configuration, when the condensed water is injected into the deaeration chamber 6-1 by the injection valve 6-5, the condensed water falls down the deaeration tray 6-3 and contacts the heated steam at this time. Oxygen is released.
This oxygen rises and stays in the upper part of the degassing chamber 6-1 and condensate is stored in the water storage tank 6-2 and sent to the water supply system as needed. This water is sent to the economizer 9 through the high-pressure feedwater heater 8 by the operation of the feedwater pump 7, and further sent from this economizer 9 to the boiler 10.

Incidentally, in such a system, the water quality is adjusted by injecting ammonia and oxygen at the outlet side of the condensate demineralizer 4 in the condensate system and at the outlet side of the deaerator 6 in the water supply system. Specifically, a control system for the supply amounts of these ammonia and oxygen will be described. An oxygen concentration meter 11 and a feedwater flowmeter 12 are provided on the inlet side of the economizer 9, and a condensate flowmeter 13 is provided on the inlet side of the deaerator 6. On the other hand, oxygen injection amount detectors 14 and 15 are provided at the outlet sides of the condensate desalination device 4 and the deaerator 6, respectively.

The control system of the condensing system sends the oxygen concentration detected by the oxygen concentration meter 11 and the condensate flow rate detected by the condensate flow meter 13 to the injection calculator 16 as shown in FIG. The injected oxygen amount detected by the injected amount detector 14 is sent to the injection calculator 16. This injection calculator 16
Controls the opening and closing of the injection valve 17 based on the input oxygen concentration, the condensate flow rate, and the injected oxygen amount to adjust the oxygen concentration in the condensate to a predetermined value.

On the other hand, the water supply system sends the oxygen concentration detected by the oxygen concentration meter 11 and the water supply flow rate detected by the water supply flow meter 12 to the injection calculator 18 as shown in FIG. Is sent to the injection calculator 18. The injection calculator 18 controls the opening and closing of the injection valve 19 based on the oxygen concentration, the feedwater flow rate and the injected oxygen amount to adjust the oxygen concentration in the feedwater to a predetermined value.

By the way, when the load of the plant is high, the deaeration chamber 6
The oxygen concentration in the upper part of -1 is high due to the upward flow of steam and the pressure in the vessel. When the load on the plant is reduced in this state, the pressure in the vessel is reduced accordingly, and the oxygen accumulated in the upper part of the degassing chamber 6-1 is diffused, expanded and expanded to the degassing tray 6-3. On the other hand, it is generally known that the solubility of oxygen increases as the temperature decreases.

Therefore, when the load on the plant is reduced and the temperature of the condensed water is lowered, the oxygen spreads to the deaeration tray 6-3 and dissolves in the feed water. As a result, the water supply has a high oxygen concentration as shown in FIG. 7 and shows a peak value of the concentration. This peak value lasts several hours if it is long.

[0014] For this reason, corrosion occurs in the condensed water supply system due to the high oxygen concentration. Therefore,
Each time a high oxygen concentration peak appears, the deaerator 6
The vent valve 6-7 is manually opened to release oxygen in the degassing chamber 6-1 to the atmosphere. And this vent valve 6
The operation of opening -7 is very complicated in the operation where the fluctuation of the plant load is large.

[0015]

As described above, in the apparatus to which the CWT method is applied, when the plant load is reduced and the condensate temperature is lowered, the oxygen concentration of the feedwater is high and shows a peak value of the concentration. The vent valve 6-7 of the deaerator 6 must be manually opened to release oxygen to the atmosphere.

Accordingly, the present invention is to provide a water quality adjusting apparatus which can obtain a stable water quality by suppressing an increase in oxygen concentration in feed water when a plant load is reduced in water quality adjustment to which a CWT method is applied. With the goal.

[0017]

SUMMARY OF THE INVENTION According to the present invention, ammonia and oxygen are injected into a condensate system in a plant and supplied to a deaerator, where the oxygen contained in the condensate is released and supplied to a water supply system. Supply, and thereafter, in a water quality adjustment device by combined neutral water treatment of injecting ammonia and oxygen into the water supply system, an oxygen concentration meter for detecting an oxygen concentration in the water supply system, and a load amount detection means for detecting a plant load amount And a deaerator vent control means for controlling the opening and closing of a vent valve of the deaerator based on the oxygen concentration detected by the oxygen concentration meter and the load detected by the load detection means. It is a water quality adjustment device.

[0018]

By providing such means, the deaerator vent control means based on the oxygen concentration in the water supply system detected by the oximeter and the plant load detected by the load detection means, and the deaerator Of the vent valve is controlled. Thereby, when the plant load is reduced, the oxygen of the deaerator is released into the atmosphere, and the increase in the oxygen concentration in the feedwater is suppressed.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. The same parts as those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 is a configuration diagram of a water quality adjusting device to which the CWT method is applied. An oxygen concentration meter 11 is provided on the inlet side of the economizer 9 in the water supply system, and a condensate thermometer 20 for detecting condensate temperature corresponding to a change in plant load is provided on the inlet side of the deaerator 6. Have been. The oxygen concentration signal output from the oxygen concentration meter 11 is sent to the deaerator vent controller 21, and the condensate temperature signal output from the condensate thermometer 20 is sent to the deaerator vent controller 21. It has become.

The deaerator vent controller 21 controls the vent valve 6 of the deaerator 6 based on the oxygen concentration signal and the condensate temperature signal.
7, which has a function of performing opening / closing control of FIG. That is, the oxygen concentration signal from the oximeter 11 is sent to the comparison calculator 22 and the change rate calculator 23. Among them, the comparison calculator 22 has a function of setting a target setting signal S for the oxygen concentration, obtaining a deviation between the target setting signal S and the oxygen concentration signal, and sending the deviation to the PI calculator 24. The PI calculator 24 has a function of executing a PI (proportional integration) calculation for setting the oxygen concentration to a target set value with respect to the input deviation signal, and sending the calculation result to the adder 25. The condensate temperature signal from the condensate thermometer 20 is input to the change rate calculator 23 together with the oxygen concentration signal, and the change rate calculator 23 calculates the oxygen concentration and condensate generated with a change in the plant load. It has a function of calculating and calculating the rate of change in temperature and calculating and determining the degree of opening and closing of the vent valve 6-7 according to the rate of change. The adder 25 has a function of adding the PI calculation result and the degree of opening / closing of the vent valve 6-7 and sending the result to the vent valve 6-7 as an opening / closing operation signal. Next, the operation of the apparatus configured as described above will be described.

When the load of the plant is high, the oxygen concentration in the upper part of the degassing chamber 6-1 is high due to the upward flow of steam and the internal pressure. When the load on the plant is reduced in this state, the pressure in the vessel is reduced, and the oxygen retained in the upper part of the degassing chamber 6-1 is diffused, expanded, and expanded.
-3. At the same time, when the plant load is reduced and the temperature of the condensed water is lowered, the oxygen spreads to the deaeration tray 6-3 and dissolves in the feed water, and the feed water has a high oxygen concentration and exhibits a peak value of the concentration. As a result, the oxygen concentration of the feedwater at the inlet side of the economizer 9 increases, and the oximeter 11 detects the oxygen concentration in the feedwater and outputs an oxygen concentration signal. At this time, the condensate thermometer 20 detects the condensate temperature at the inlet side of the deaerator 6 and outputs the condensate temperature signal.

The oxygen concentration signal output from the oximeter 11 is sent to a comparison calculator 22 and a change rate calculator 23. Among them, the comparison calculator 22 calculates a deviation between the oxygen concentration target setting signal S and the oxygen concentration signal. Is sent to the PI calculator 24. The PI calculator 24 executes a PI calculation for setting the oxygen concentration to the target set value for the input deviation signal, and sends the calculation result to the adder 25.

The change rate calculator 23 receives the oxygen concentration signal and the condensate temperature signal from the condensate thermometer 20, and calculates the change rate of the oxygen concentration and the condensate temperature generated with the change of the plant load. Vent valve 6-
7 is calculated and obtained. Then, the adder 25 outputs PI
The calculation result and the degree of opening / closing of the vent valve 6-7 are added and sent to the vent valve 6-7 as an opening / closing operation signal. As a result, the vent valve 6-7 opens, and the oxygen remaining in the degassing chamber 6-1 is released to the atmosphere through the discharge pipe 6-6. Thereby, the oxygen concentration of the feedwater sent to the economizer 9 is adjusted to a predetermined value.

As described above, in the first embodiment, the deaerator vent controller 21 based on the oxygen concentration in the water supply system detected by the oxygen concentration meter 11 and the condensate temperature detected by the condensate thermometer 20. The vent valve 6 of the deaerator 6
Since the opening / closing control of −7 is performed, when the load on the plant is reduced, oxygen in the deaerator 6 can be released into the atmosphere to suppress an increase in the oxygen concentration in the feed water. The target oxygen concentration can be adjusted to an appropriate value. As a result, corrosion does not occur even in the stagnant state in the condensate supply system, and the complicated operation of manually opening the vent valve 6-7 every time the plant load changes is eliminated.

Next, a second embodiment of the present invention will be described. In this embodiment, the deaerator vent controller 21 is changed to a deaerator vent controller 30 having the configuration shown in FIG. That is, the condensate temperature signal is input to the change rate calculator 31 together with the oxygen concentration signal. The change rate calculator 31 calculates the rising change rate of the oxygen concentration and calculates the decreasing change rate of the condensate temperature. It has a function of obtaining an oxygen concentration set value according to the rate of change. The oxygen concentration set value is sent to the adder 32, and the adder 32 adds the steady-state oxygen concentration set value to the oxygen concentration set value, and sends this to the comparison calculator 33 as a target setting signal. This comparison operator 33
Has a function of calculating the deviation between the target setting signal and the oxygen concentration signal from the oximeter 11 and sending the deviation to the PI calculator 34. The PI calculator 34 has a function of executing a PI calculation for setting the oxygen concentration to a target set value with respect to the deviation signal and transmitting the calculation result as an operation signal to the vent valve 6-7.

With such a configuration, when the plant load is reduced from a high load, the water supply becomes high in oxygen concentration as described above, and exhibits a peak value of the concentration. In this state, the change rate calculator 31 receives the oxygen concentration signal and the condensate temperature signal, calculates the increase rate of the oxygen concentration, calculates the decrease rate of the condensate temperature, and calculates the oxygen concentration signal according to these change rates. Find the set value. This oxygen concentration set value is calculated by adder 3
The adder 32 adds the steady-state oxygen concentration set value to the oxygen concentration set value, and sends the result to the comparison calculator 33 as a target setting signal. The comparison calculator 33 calculates a deviation between the target setting signal and the oxygen concentration signal from the oximeter 11 and sends the deviation to the PI calculator 34. This PI calculator 34
Performs a PI calculation for setting the oxygen concentration to a target set value for the deviation signal, and uses the calculation result as an operation signal as a vent valve 6.
Send to -7. As a result, the vent valve 6-7 opens and the oxygen remaining in the degassing chamber 6-1 is released to the atmosphere through the discharge pipe 6-6. Thereby, the oxygen concentration of the feedwater sent to the economizer 9 is adjusted to a predetermined value. Thus, the second
In the embodiment, the same effects as in the first embodiment can be obtained.

The present invention is not limited to the above embodiments, but may be modified within the scope of the invention. For example, a signal representing the plant load may be input instead of the condensate temperature input to the change rate calculators 23 and 31. Further, the oxygen concentration clock 11 provided on the inlet side of the economizer 9 may be provided on the outlet side of the deaerator 6 or on the water storage tank 6-2 of the deaerator 6.

[0029]

As described above in detail, according to the present invention, C
In the water quality adjustment to which the WT method is applied, it is possible to provide a water quality adjustment device capable of obtaining a stable water quality by suppressing an increase in the oxygen concentration in the feed water when the plant load is reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a water quality adjusting device according to the present invention.

FIG. 2 is a specific configuration diagram of a deaerator vent controller in the same device.

FIG. 3 is a specific configuration diagram of a deaerator vent controller in a second embodiment of the water quality adjustment device according to the present invention.

FIG. 4 is a configuration diagram of a conventional device.

FIG. 5 is a specific configuration diagram of a deaerator in the apparatus.

FIG. 6 is a configuration diagram of a control system for water quality adjustment in the apparatus.

FIG. 7 is a diagram showing a behavior of oxygen concentration with respect to a change in plant load.

[Explanation of symbols]

1. Condenser, 2. Condenser pump, 3. Condenser booster pump, 4.
... condensate desalination equipment, 5 ... low-pressure feed water heater, 6 ... deaerator, 6
-1: deaeration chamber, 6-2: water storage tank, 6-7: vent valve, 7: water supply pump, 8: high-pressure water heater, 9: economizer, 10: boiler, 11: oxygen concentration meter, 20 ... condensate thermometer, 21 ... deaerator vent controller, 22, 33 ... comparison calculator, 23, 31 ... change rate calculator, 24, 34 ... PI calculator, 25, 32 ... adder.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C23F 14/00 C23F 14/00 15/00 15/00 (72) Inventor Tsunobu Kato 10-1 Kitahamacho, Chita City, Aichi Prefecture Chubu Electric Power Co., Ltd.Chita Daini Thermal Power Station (72) Inventor Shigeo Kobitsu 10-1 Kitahama-cho, Chita City, Aichi Prefecture Chubu Electric Power Co., Inc. 1 Chubu Electric Power Co., Inc. Chita Daini Thermal Power Station (72) Inventor Akira Takahashi 2-4-4 Suehirocho, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Toshiba Keihin Works Co., Ltd. (72) Inventor Hide Amemiya Tsurumi-ku, Yokohama-shi, Kanagawa 2-4 Suehirocho Inside Toshiba Keihin Works Co., Ltd. (56) References JP-A-59-89778 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C02F 1/20 B01D 19/00 C02F 5/00 C02F 1/00 C23F 14/00 C23F 15/00 G21D 1/00-9/00 F22D 11/00 F28B 9/00

Claims (1)

(57) [Claims] 1. Injection of ammonia and oxygen into a condensate system in a plant to supply them to a deaerator, in which oxygen contained in the condensate is released and supplied to a water supply system. In the water quality adjustment device by combined neutral water treatment of injecting ammonia and oxygen to the oxygen concentration meter for detecting the oxygen concentration in the water supply system, load detection means for detecting the plant load, and the oxygen concentration meter A water quality control device comprising: deaerator vent control means for controlling opening and closing of a vent valve of the deaerator based on the detected oxygen concentration and the load detected by the load detection means.