JP2718858B2 - 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 / water supply system in a power plant or the like.

[0002]

2. Description of the Related Art In a thermal power plant or the like in Japan, condensate water in a system, water supply, boiler water and steam quality control processing are performed to minimize corrosion in the system, and boiler water pipes / steam pipes and a water supply pump suction. The scale adhesion to the strainer has been prevented. When the boiler type is a once-through type, a volatile substance treatment (hereinafter, referred to as an AVT method) in which volatile chemicals such as ammonia (NH ₃ ) and hydrazine (N ₂ H ₄ ) are injected into the condensate / water supply system, pH value between 9 and 9.5
And deoxygenation.

However, in the above-mentioned AVT method, a high ammonia concentration (pH>
9.4), which is required in the ammonia enrichment section of the plant (for example, in the condenser air cooling section).
Since damage by ammonia (ammonia attack) occurred, anticorrosion measures could not be taken with high-concentration ammonia.

[0004] As a result, iron is eluted from the carbon steel in the plant into the condensate / water supply system by the hydrazine as a reducing agent, and adheres to the boiler water pipe / steam pipe, the feed water pump suction strainer, etc., and its thickness increases over time. Will increase. For this reason, the adhered iron oxide must be removed at an appropriate time, which has been a great obstacle to plant operation planning. Also,
If this removal is not performed, there is a risk that overload operation of the water supply pump and cracking of the boiler tube may be caused.

In order to improve the above-mentioned drawbacks of the conventional AVT method, ammonia (NH ₃ ) and oxygen (O
₂ ) Injection of complex neutral water treatment (hereinafter referred to as CWT method) is being carried out in stages. According to this CWT method, iron oxide is greatly reduced on the boiler water pipe / steam pipe and the feed water pump suction strainer by changing the conventional strong alkali to weak alkali into the condensate / water supply system and injecting oxygen. can do.

[0006] Such a conventional water quality adjusting device will be described with reference to the system diagram of FIG. In FIG. 1, turbine exhaust steam and heater drain (both not shown) collected in a condenser 1 are condensed by heat exchange with circulating water using seawater as cooling water, and then condensed by a condensing pump 2. The water is sent to the water desalination device 3. In this condensate desalination apparatus 3 (hereinafter referred to as condemi), after removing suspended solids such as iron oxide and dissolved solids such as chloride ions in the condensate, the condensate booster pump 4 removes the low-pressure feed water heater 5. And the water is sent to the deaerator 6. The condensed water sent to the deaerator 6 is sent to a water supply pump 7 together with a high-pressure heater drain (not shown), heated by a high-pressure water heater 8, passed through a economizer 9, and sent to a boiler 10.

On the other hand, water quality adjustment (oxygen injection) is installed in each of the condensing system and the water supply system. Condensate system is the oxygen O ₂ is injected from the outlet side of the Kondemi 3, the water supply system is implanting oxygen O ₂ from the outlet side of the deaerator 6.

Next, the control method of the water quality adjustment is shown in FIG.
A description will be given with reference to a diagram of an oxygen injection system to the water supply system. The condensate system inputs the oxygen concentration 13 at the inlet of the economizer 9, the condensate flow rate 21 at the inlet of the deaerator 6, and the oxygen injection amount 22 at the inlet of the condemi 3 to an oxygen injection calculator 23. The opening degree of the injection valve 24 is controlled to keep the oxygen concentration in the condensate system. On the other hand, in the water supply system, the oxygen concentration 13 at the inlet of the economizer 9, the feedwater flow rate 25 at the inlet of the economizer 9, and the oxygen injection amount 26 at the outlet of the deaerator 6 are also supplied to the injection valve 28 via the oxygen injection calculator 27. The opening is controlled to keep the oxygen concentration in the water supply system. When the plant is operated by the CWT method, a deaerator vent valve (not shown) is used to prevent oxygen release in the system.
Is completely closed.

The behavior of the condensate flowing into the deaerator and the oxygen injected and dissolved at the outlet of the condemimeter when the CWT method is used in the above system configuration will be described with reference to FIGS.

In FIG. 8, the condensate containing oxygen under high load is contacted with the heated steam while falling down the distribution tray and the deaeration tray in the deaerator to release oxygen and is stored in the water storage tank. The oxygen released here stays as an uncondensable gas in the upper part of the deaerator and is in a high concentration state. This is affected by the upward flow of steam inside the deaerator and the pressure inside the chamber.

It is generally known that the solubility of oxygen is greatly affected by the temperature, and the solubility increases as the temperature decreases. Therefore, when the pressure in the deaerator decreases due to a subsequent load drop, the high-concentration oxygen that had accumulated at the top of the deaerator spreads to the deaeration tray, and the condensate temperature also decreases. since deaerator vessel is thermally balanced equilibrium state (condensate until the saturation temperature of that load) melt write No in water until, as shown in FIG. 9, the high peak value of the oxygen concentration Will show.

[0012]

In the CWT method, as described above, when the load drops, the high-concentration oxygen that has accumulated in the upper part of the deaerator diffuses, expands in volume, and recovers inflow due to a decrease in the internal pressure. As the water temperature decreases, it dissolves in the feed water, shows a high peak value, and lasts several hours if it is long. This increases the oxygen concentration in a stagnant portion in the water supply system, and causes corrosion to occur in that portion. For this reason, when the oxygen concentration shows a high peak value, it is necessary to manually open the deaerator vent valve each time to release oxygen to the atmosphere, which is very complicated in plant operation where daily load changes are severe. Problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to prevent high-concentration oxygen from diffusing and dissolving into feedwater in a deaerator, which is generated when a load on a plant changes, to achieve a stable operation. An object of the present invention is to provide a water quality adjusting device capable of adjusting water quality.

[0014]

To achieve the above object, according to the Invention The claim 1 of the present invention is a water conditioning apparatus condensate-water supply system in a power plant or the like, the condensate was injected oxygen flows de Which is attached to the porcelain and stays in this deaerator
An automatic control valve for discharging high-concentration oxygen, a pressure detector for detecting the pressure in the deaerator, and a time change rate of the pressure.
, A temperature detector for detecting the temperature of the condensate flowing into the deaerator , a condensate temperature corresponding to the load of the plant, and a condensate temperature when the load changes.
Output the open temperature value of the automatic control valve from the delay characteristics of the change
Set value calculator, the set value calculator and the pressure change
Receiving a signal from the rate calculator to send an open / close signal to the automatic control valve.
And a switching arithmetic and logic unit for outputting . Departure
A second aspect of the invention is a condensate and water supply system in a power plant or the like.
Condensate flows into the water quality control device
High concentration that is attached to the deaerator
An automatic control valve for discharging oxygen, and the pressure inside the deaerator
Calculate the pressure detector to be detected and the time rate of change of this pressure.
Pressure change rate calculator, and the temperature of the condensate flowing into the deaerator.
Temperature detector that detects the temperature and the rate of change of this temperature over time.
Calculating the temperature change rate calculator, and the pressure change rate calculator.
Receives a signal from the temperature change rate calculator and sends it to the automatic control valve.
A switching operation unit for outputting a switching signal.
I do.

[0015]

[Action] The pressure in the deaerator decreases as the load decreases, and the rate of pressure decrease due to the volume expansion of oxygen remaining in the deaerator is detected. Open the automatic control valve of the ventilator vent valve to release the high-concentration oxygen remaining in the upper part of the deaerator into the atmosphere, reduce its dissolution into the water supply system, and maintain the oxygen concentration in the water supply properly. . Further, when the temperature becomes equal to or higher than the condensate temperature plus the bias temperature corresponding to the load, the automatic control valve of the deaerator vent valve is opened to maintain the oxygen concentration in the supply water properly.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram of a water quality adjusting device of a condensate / water supply system in a power plant according to one embodiment of the present invention. The same parts as those in FIG. 6 described above are denoted by the same reference numerals, and description thereof will be omitted.

In FIG. 1, the detection signal of a condensate temperature detector 12 for detecting the temperature of the condensate flowing into the deaerator 6 and the detection signal of a pressure detector 13 for detecting the pressure of the deaerator 6 change. It is input to the open / close calculator 17 via the rate calculator 14. In the opening / closing operation unit 17, a signal for opening and closing the control valve 11 for discharging the oxygen filled in the deaerator 6 based on the signals α and β from the setting value operation unit 15 that calculates the signals of the setting values α and β based on the load signal 16. Is output.

FIG. 2 shows a detailed block diagram of the set value calculator 15. In the figure, a reset signal β is output from the heat balance graph 20 of the condensate temperature corresponding to the load flowing into the deaerator previously determined by the heat balance by the load signal 16. Further, a bias value in consideration of the condensate temperature delay by the load is input to the bias graph 21 by the load signal 16, and the bias signal and the β signal are added by the adder 22 to obtain the set temperature signal α for valve opening operation. Output.

FIG. 3 shows a detailed block diagram of the switching operation unit 17. In the figure, when the temperature signal T of the condensate temperature detector 12 becomes equal to or higher than the set temperature value α ° C. in consideration of the bias value, the control valve 11 is opened while using the self-holding circuit. Thereafter, as the load stabilizes, the condensate temperature signal T becomes lower than the set temperature value β ° C. of the heat balance base.
The open state of 1 is continued, and oxygen filled in the deaerator 6 is discharged before dissolving in the water supply.

Further, in this embodiment, the function of discharging oxygen is also provided by pressure, and when the output signal P of the pressure change rate calculator 14 of the deaerator 6 reaches a predetermined pressure change rate γ ₁ or more once. , Ru regulation valve 11 similar to the temperature signal of the to opening operation. Further, the rate of pressure change causes the closing operation When turned gamma ₂ or less.

By the opening and closing operation of the control valve 11, the oxygen whose volume expands with the load drop is caught by the pressure drop rate due to the load drop and is discharged to the atmosphere, and as the temperature drops, the oxygen dissolves into the water supply. High oxygen can be exhausted before the pressure increases.

FIG. 4 is a system diagram of another embodiment of the present invention. In this embodiment, the configuration different from the embodiment of FIG. The configuration is such that the temperature signal is input to the opening / closing calculator 17a via the temperature change rate calculator 18. Since other configurations are the same, the same portions are denoted by the same reference numerals and description thereof will be omitted.

FIG. 5 is a block diagram of the switching operator 17a of FIG. In the figure, once the temperature signal T of the temperature change rate calculator 18 reaches a predetermined temperature change rate δ ₁ or more, the control valve 11 is opened, and when the temperature change rate becomes δ ₂ or less, the control valve 11 is closed.

Further, oxygen is also imparted by the pressure the function of discharging, the pressure signal P of the pressure change rate arithmetic unit 14 of the deaerator 6 reaches once _one or more predetermined pressure change rate gamma, the temperature signal Similarly, the control valve 11 is opened, and when the pressure change rate becomes γ ₂ or less, the control valve 11 is closed.

By the above-mentioned opening and closing operation of the control valve 11, oxygen whose volume expands with the load drop is detected by the pressure drop rate due to the load drop and discharged to the atmosphere, and as the temperature drops, the oxygen dissolves into the water supply. It is possible to discharge high-concentration oxygen before the pressure increases, and the effect is the same as that of the embodiment of FIG.

[0026]

As described above, according to the present invention,
High-concentration oxygen in the deaerator, which causes an increase in the oxygen concentration at the inlet of the economizer, which occurs when the load on the condensate and water supply system is adjusted in the power plant by changing the load on the plant due to combined neutral water treatment By preventing the diffusion and penetration of water, stable water quality adjustment becomes possible.

[Brief description of the drawings]

FIG. 1 is a system diagram of an embodiment of the present invention.

FIG. 2 is a functional block diagram of a set value calculator of FIG. 1;

FIG. 3 is a functional block diagram of the open / close arithmetic unit of FIG. 1;

FIG. 4 is a system diagram of another embodiment of the present invention.

FIG. 5 is a functional block diagram of the opening / closing arithmetic unit in FIG. 4;

FIG. 6 is a system diagram of a conventional condensate / water supply system.

FIG. 7 is a diagram of an oxygen injection system to the condensate / water supply system of FIG. 6;

8 is an internal configuration diagram of the deaerator of FIG.

FIG. 9 is a view showing an oxygen behavior graph of FIG. 6;

[Explanation of symbols]

1. Condenser, 2. Condensate pump, 3. Condensate desalination unit, 4.
Condensing pressure booster pump, 5 ... Low pressure feed water heater, 6 ... Deaerator, 7
... water feed pump, 8 ... high pressure feed water heater, 9 ... coal saving device, 10
... boiler, 11 ... control valve, 12 ... condensate temperature detector, 13
... pressure detector, 14 ... pressure change rate calculator, 15 ... set value calculator, 16 ... load signal, 17, 17a ... switching calculator,
18: Temperature change rate calculator.

Claims (2)

(57) [Claims] 1. A condensate in which oxygen is injected flows into a water quality control device of a condensate / water supply system in a power plant or the like.
The high-concentration gas attached to the deaerator
An automatic control valve for discharging oxygen, a pressure detector for detecting the pressure in the deaerator, and calculating a time change rate of the pressure
A pressure change rate arithmetic unit, wherein a temperature detector for detecting the temperature of the condensate flowing into the deaerator condensate load equivalent of the plant
Slow change in condensate temperature when water temperature and load change
Set value for outputting the open temperature value of the automatic control valve from the characteristics
A computing unit, the set value computing unit and the pressure change rate computing unit.
Output the open / close signal to the automatic control valve in response to the
A water quality adjustment device comprising a closed computing unit . 2. A condensate and water supply system for a power plant or the like.
Condensate infused with oxygen flows into the water quality control device
The high-concentration gas attached to the deaerator
Automatic control valve for discharging oxygen and pressure inside the deaerator
Calculate the pressure detector that emits and the time rate of change of this pressure
A pressure change rate calculator and a temperature of the condensate flowing into the deaerator.
Detects temperature and calculates the rate of change of this temperature over time
Temperature change rate calculator, the pressure change rate calculator,
Receives a signal from the temperature change rate calculator and opens the automatic control valve.
A switching operation unit for outputting a closing signal.
Water quality control device.