JPS61242683A - Method and device for deaerating feed water - Google Patents

Abstract

PURPOSE:To reduce effectively oxygen dissolved in feed water by effectively warming the feed water to be sent to a daerator with auxiliary steam and evacuating the inside of the deaerator with a deaerator vent system. CONSTITUTION:The lower end part of a feed water communicative pipe 10 for communicating a deaeration chamber 1 with a water storage tank 12 is led below the water surface in the water storage tank 12, (a) a vent pipe 14 provided with an orifice 14a and a stop valve 15 for the vent pipe and (b) a start-up vent pipe 16 furnished with a stop valve 17 for the vent pipe are arranged in parallel between the deaeration chamber 1 and a condenser and a pipe 18 for supplying heated steam to the deaeration chamber 1 is provided. The feed water deaeration device is used for heating the feed water to a boiler. When the boiler is started, the valve 17 is opened and a part of heated steam is introduced into the water storage tank 12. Consequently, time necessary for deaeration and cleanup at startup can be reduced, the amt. of auxiliary steam is saved and the cost of in-plant boiler equipment can be reduced.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to a deaeration technology for removing non-condensable gases such as oxygen dissolved in the water supply in a thermal power plant, and in particular, The present invention relates to a feed water deaeration method and a feed water deaeration device suitable for reducing dissolved oxygen in a short period of time.

[Background of the invention]

Conventionally, in thermal power plants, deaerators have been installed to heat and deaerate feed water supplied to the boiler using turbine extraction air or boiler steam to prevent corrosion of the entire plant and improve thermal efficiency. It is being The latest known technology regarding degassing methods and devices can be found in the US literature [Theoretical Perspectives on Physical Degassing J (Theoreii
ca] aspects of pkysjcal da
-aeratjon) Familiar with Stoke Publishing.

The prior art regarding the degassing method and degassing device will now be described with reference to FIG.

The degassing device is a degassing chamber 1. and a water storage tank 12, the deaeration chamber 1 heats and deaerates the supplied water, and the water storage tank 12
stores the deaerated water supply.

The supplied water is guided to the deaeration chamber 1 by a water supply pipe 6, and is sprayed and atomized by the spray pulp 8 in a part of the deaeration chamber 1-1. Feed water, which has been atomized and has a rapidly increased surface area, exchanges heat with the steam through direct contact while flowing through the steam atmosphere at high speed, rising to the saturation temperature of the deaerator operating pressure. Diffusion degassing (first stage degassing) is performed by heat exchange, and the non-condensable gas of the corresponding star is degassed by this first stage degassing.

Furthermore, the feed water is distributed by the distribution tray 4 to the degassing tray 5'', flows down in a meandering manner, and is mixed with the heated steam rising inside the tray to perform second stage degassing. The supplied water that has passed through the tray and completed deaeration once accumulates in the lower part of the deaeration chamber 1, flows down the water supply communication pipe 10, and is stored in the water storage tank J2.

On the other hand, heated steam flows into the degassing chamber 1 from the steam population 9,
The water goes around the tray chamber to heat the feed water, then flows into the tray chamber through the steam inflow path at the bottom of the tray chamber and rises between the trays. -1- The rising steam removes non-condensable gases from the flowing feed water. The steam that has risen between the trays passes through the side of the distribution box 3 and enters the spray chamber 2, where it exchanges heat with the sprayed atomized feed water, becomes condensate, and flows down together with the feed water. The non-condensable gas that has not become condensed water is discharged from a vent pipe 7 provided at the seat of the spray pulp 8.

When a plant equipped with a boiler equipment is operated regularly, sufficient turbine oil gas or boiler steam can be supplied to the deaerator, so the feed water can be degassed and dissolved acid m
There is no difficulty in installing a separate device to keep the temperature below the specified value.

However, in the cleanup operation when starting up to Plan 1, a large amount of makeup water that has not been degassed is introduced into the system via the condenser.

In this case, the operation of the deaerator and the piping system around it is
The diagram will be explained.

At the time of cleanup, the heating steam is still before boiler temperature, so turbine extraction or boiler steam cannot be taken, and auxiliary steam from the boiler or the in-house boiler is introduced into the deaerator through the heating steam pipe 18. 19 is a stop valve.

In addition, regarding the operation of the vent system of the deaerator, in order to effectively exchange heat between the feed water and auxiliary steam, the stop valve 15 of the vent pipe 14 is open, but the stop valve 17 of the start vent pipe 6 is closed. It was.

However, during clean-up operation at plant start-up, there are many cases in which auxiliary steam cannot be sufficiently supplied to the deaerator due to various circumstances (for example, operational problems of the power plant as a whole).

In this case, sufficient heat exchange between the auxiliary steam and the feed water may not take place, or there may be a shortage of auxiliary steam in the degassing chamber 1.
It takes a long time to reduce the dissolved oxygen concentration in the water supply to the specified value.

In addition, recently, the plant has started and stopped frequently due to intermediate load operation.
・WS 5(Week)y 5tart & 5top
), it is necessary to reduce the dissolved oxygen in the deaerator at the time of plant start-up with a small amount of auxiliary steam and in a short time due to the power plant's need to complete cleanup in a short time.

As described above, there are the following problems with the conventional technology for deaeration of feed water, and an immediate solution is desired.

(1) Deaeration/cleanup takes a long time. →Large start-up time/Large start-up loss (2) A large amount of auxiliary steam was required, which increased the capacity of the in-house boiler and increased equipment costs.

[Purpose of the invention]

The present invention has been made to meet the needs mentioned in 1-1 above.
and (ii) providing a deaeration method and a deaeration device that can save the amount of auxiliary steam and reduce equipment costs for an in-house boiler, thereby improving the reliability of the plant by improving the quality of the water supply.

The purpose is to contribute to durability -1-.

[Summary of the invention]

The basic principles of the method of the present invention, which was created to achieve objective 1 of the Book of Yu, are summarized below.

The main point of the present invention is to focus on the fact that the lower the pressure and the higher the temperature, the lower the oxygen solubility in feed water, and to effectively heat the feed water sent to the deaerator with auxiliary steam and desorb the water. The goal is to create a vacuum inside the deaerator using the air vent system and effectively reduce dissolved oxygen in the water supply.

In order to achieve the above-mentioned goal based on the principle of Section 11, the method for deaeration of feed water according to the present invention includes providing a water storage tank below the deaeration chamber and connecting the deaeration chamber and the water storage tank with water supply. The lower end of the water supply connecting pipe shall reach below the water surface in the water storage tank, and between the deaeration chamber and the condenser there shall be an orifice and a vent pipe stop valve. and (b) the starting pen 1 - pipe provided with the starting vent pipe stop valve are connected in parallel, and heating steam is supplied to the degassing chamber. In a method of heating feed water for a boiler using a condensation deaerator equipped with a pipe, when starting the boiler, the starting vent pipe stop valve is opened and a part of the heated steam is stored in water. It is characterized by being introduced into a tank.

In addition, the device of the present invention, which was created so that the above-mentioned method can be easily carried out and fully exhibit its effects, has a water storage tank provided below the deaeration chamber, and a water supply tank that connects the deaeration chamber and the water storage tank. The lower end of the above-mentioned water supply communication pipe shall reach below the water surface in the water storage tank, and the deaeration chamber and condenser shall be connected in u)1 with (a) an orifice and a vent. The pen 1 pipe provided with a pipe stop valve and (b) the starting vent pipe 1 provided with a starting vent pipe stop valve are connected in parallel, and heated steam is supplied to the deaeration chamber. In the feed water deaerator equipped with a heated steam pipe, a steam injection nozzle is provided below the water surface of the deaerator water storage tank, and a part of the heated steam is provided in a pipe line that supplies the steam injection nozzle. Features.

[Embodiments of the invention]

FIG. 1 shows an embodiment in which the feed water deaerator of the present invention is applied and improved to the above-mentioned known feed water deaerator (FIG. 4) in order to carry out the deaeration method of the present invention.

The difference from the known device (FIG. 4) is as follows.

Deaeration chamber 1. and a water supply connecting pipe 10 that connects the water storage tank 12.
The water surface in the water storage tank 12 is divided on one side. In addition, a starting heating steam pipe 20 is branched from the heating steam pipe 18 to the deaeration chamber 1, and is introduced into the lower part of the water storage tank 12 (below the distribution pipe 3) through the stop valve 21, and is blown out in the direction. A spray nozzle 22 is installed near the bottom of the water storage tank 12.

When carrying out the degassing method of the present invention using the device of this embodiment (Fig. 1), when introducing heating steam for startup, the deaerator installed in the pipe 14 to the pen 1 which is the system from the deaerator vent 1 to It is operated by opening the stop valve 15 and the stop valve 17 installed in the startup vent pipe 16.

Next, the operation and deaeration effect will be explained.

When starting Plan 1, the stop valve 15 of the vent pipe 14 and the stop valve 17 of the starting pen 1 to pipe J6 are fully opened when heating steam is introduced into the deaerator. The effect of fully opening the stop valve 17 is as follows.

Since the vent pipe 14 is provided with an orifice 14a, the degree of vacuum in the deaeration chamber 1 will not reach the vacuum degree of the condenser just by fully opening the stop valve 15, but the starting vent with a large pipe diameter By fully opening the stop valve 17 of the pipe 16, the degassing chamber 1
The degree of vacuum inside the condenser is made approximately equal to the degree of vacuum of the condenser, thereby making it possible to achieve a vacuum deaeration effect of dissolved oxygen in the feed water and to reduce the amount of heating steam (this principle will be described later).

In the above state, heated steam is introduced from the starting heating steam pipe 20 and is blown out from the spray nozzle 22 toward the upper distribution pipe 13 side. The blown steam becomes bubbles and reaches the water surface while directly exchanging heat with the water supplied in the water storage tank 12 and increasing the temperature. The pressure on the water surface is a vacuum, and the specific volume of the steam bubbles is significantly increased, and the steam bubbles flow in one direction at high speed, ascending the pressure equalization pipe 11 and the water supply pipe 10, and are introduced into the degassing chamber 1. Ru. Here, the effect of dividing the water supply pipe 10 in the water storage tank 12 is that the steam flowing in one direction on the water surface of the water storage tank 12 can be uniformly introduced into the deaeration chamber 1, and the It is possible to prevent the water supply in the water storage tank 12 from flowing back to the degassing chamber 1 side through the water supply connection pipe 10 due to the pressure difference with the tank 12 (note that the backflow prevention 1F- indicated in - is not operated normally). FC
A similar effect can be obtained at time B or when the load is reduced).

The steam uniformly introduced into the degassing chamber 1 exchanges heat with the atomized feed water flowing down while ascending the degassing tray 4, which is arranged in 52 sections, to precipitate non-condensable gas in the feed water. The water is deaerated, and it becomes condensate and flows down with the water supply. The non-condensed gas that did not become condensed water is stored in the vent pipe 1.
4 and the starting vent pipe 16 to the condenser.

Next, an example of the relationship between the amount of dissolved oxygen in the water supply and the degree of vacuum and temperature, which is the basic principle of the present invention, will be explained with reference to FIG.

From this figure, it can be seen that the amount of dissolved oxygen in the water supply decreases as the degree of vacuum and temperature increase.

For example, in the vacuum degassing state shown in FIG.
Since the stop valve 17 of No. 6 is closed, the internal pressure of the deaerator becomes higher than the internal pressure of the condenser due to the orifice action. In this state, the amount of dissolved oxygen is approximately 10 ppm (point ■) at the feed water temperature of 15°C and atmospheric pressure in Figure 2, and the deaerator internal pressure is 700 H.
At gVac, the state is at point 2, but at this stage the amount of dissolved oxygen is 500 ppm or more. Furthermore, by introducing heated steam to the deaerator, the temperature of the feed water was increased from 15℃ to 40℃ (
At ΔT=25°C), the system reaches a zero point state, and the amount of dissolved oxygen also reaches 50 ppb or less, which is the specified value at startup.

However, in the vacuum degassing state of FIG. 19, which is the present invention,
In contrast to the prior art, by opening the stop valve 7 of the startup vent pipe 16, the deaerator internal pressure is bypassed through the orifice, so it decreases and becomes approximately equal to the condenser internal pressure, increasing the specific volume. Deaeration efficiency is also improved. The amount of dissolved oxygen in this state is
Feed water temperature 15℃ Deaerator internal pressure 730 un'F (g V
In a c, the point becomes 0 from point ■ in FIG. 2, and the amount of dissolved oxygen is reduced to about 220 ppb at this stage. The range of temperature increase necessary to further heat the feed water from this stage @ point using heated steam to reach the specified dissolved oxygen concentration of 50 ppb is:
(From the point of view of design, up to 101 points, that is, a water supply temperature of approximately 11°C from 15°C to 26°C is sufficient.

Furthermore, in cold regions, when the seawater temperature is low and there is no turbine heat load at startup, the deaerator internal pressure drops even further to 740 m
n Hg V a c, so the vacuum rises to about 00 ppb (point ■), and the -1-rise in temperature required to achieve the specified dissolved oxygen amount of 50 ppb by introducing heated steam to the deaerator is 0 from point ■). In other words, by increasing the temperature from the feed water temperature of 15° C. to about 18° C. (!1 TJ-3° C.), the prescribed value of the dissolved oxygen concentration can be ensured, and the amount of auxiliary steam can be further reduced.

Here, the required auxiliary steam amount Ga (T/H) is as follows (
1) It is determined by the formula.

However, G, = Water supply amount (500T/H) H1 = Auxiliary steam enthalpy (700Kcafl/H) H2 = Deaerator outlet water supply enthalpy H3 = Deaerator inlet water supply enthalpy Next, 600MW class power generation Regarding the boiler equipment in the plant, the amount of auxiliary steam required to raise the temperature from point ■ to point C in Figure 2 (conventional example) is: 18T/H. The pressure inside the air chamber is 1
゜5at;a, assuming that the storage water temperature is maintained at 111℃, then the temperature required to raise the temperature from point [Yes] to point (L) in the embodiment of the present invention is The amount of auxiliary steam is medium 8T/H Similarly, ('\r) in the embodiment of the present invention (cold region)
(For temperature increase from point to point ((71 point, cow 2 T
/ H As shown above, the amount of auxiliary steam required for degassing feed water is approximately 18 T/H for conventional vacuum degassing and approximately 70 T/H for conventional pressurized degassing. Approximately 8 T/H1 at high temperatures, and approximately 2 T in cold region plants.
/ I (This makes it possible to significantly reduce the amount of auxiliary steam.

In this way, in this embodiment, it is possible to increase the vacuum of the deaerator during (a) deaeration operation with the deaerator at startup, so it is possible to increase the vacuum of the deaerator by more than 50% compared to the conventional required amount of auxiliary steam. It is possible to save 600 yen and reduce the in-house boiler capacity.
Conventionally, approximately 18 T/H of auxiliary steam was required during vacuum degassing with a MW class bran 1-, but this can be reduced to 2 to 8 T/H with the present invention.

(b) According to the present invention, efficient feed steam operation is possible, so the conventional preboiler cleanup at the initial stage is
The cleanup time used to take approximately 1-0 days, but the cleanup time has been shortened by 3 to 4 days, and the startup time and startup loss can now be reduced.

(c) Regarding items 1 and 2 above, since the amount of dissolved oxygen in the water supply could be efficiently reduced, the reliability of the plant could be ensured by improving the water quality.

This had a practical effect.

FIG. 5 shows a partial application of the degassing method according to the invention.

This application example was carried out using the conventional deaerator shown in Fig. 4, and when the start-up operation is performed, the stop valve 1 of the start-up vent pipe ] 6
Open 7. This reduces the pressure inside the deaerator 1 and increases the specific volume of steam, thereby improving steam efficiency and reducing the amount of auxiliary steam required.

FIG. 6 shows a different embodiment of the apparatus from FIG.

The principle is the same as the embodiment shown in FIG. 1, but no opening is provided in the water supply pipe 10'. Starting Hen 1-Pipe 16
By opening the stop valve 17 and introducing auxiliary steam into the lower part of the water storage tank 12, the temperature of the stored water can be effectively raised by -1-, and the deaeration time can be shortened by the deaeration effect.

The amount of auxiliary steam can be reduced.

FIG. 7 shows a further different embodiment of the apparatus. This example differs from FIG. 1 in that in addition to the steam nozzle 22 below the water surface, a steam nozzle 22' above the water surface is also provided. This configuration has the effect of easily responding to fluctuations in the water level within the water storage tank 12.

〔Effect of the invention〕

As described above, according to the deaeration method of the present invention, (i) reduction of deaeration and cleanup time at startup;
and (ii) it is possible to save the amount of auxiliary steam and reduce the equipment cost of the in-house boiler, which greatly contributes to improving the reliability and durability of the plant by improving the quality of the water supply.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of one embodiment of the present invention, Fig. 2 is a chart showing the relationship between the amount of dissolved oxygen and the degree of vacuum, and temperature, and Fig. 3 is a diagram showing the structure of the deaerator and the degassing action. FIG. 4 is an explanatory diagram of a conventional degassing state at startup, and FIG. 5 is a detailed explanatory diagram of the present invention. FIGS. 6 and 7 are explanatory diagrams of embodiments different from those described above, respectively. 1... Deaeration chamber, 2... Spray room, 3... Distribution box, 4... Distribution tray, 5... Deaeration tray, 6...
Water supply inlet pipe, 7... Vent pipe, 8... Spray pulp, 9... Steam inlet, 10.10'... Water supply connecting pipe, 11... Equalizing pressure connecting pipe, 12... Water storage tank, 13
...Distribution pipe, 14...Vent pipe, 1.4 a...
Orifice, 15... Vent pipe stop valve, 16... Starting vent pipe, 17... Starting vent pipe stop valve, 18...
・Heating steam pipe, 19... Stop valve, 20... Heating steam pipe for starting, 21.21'... Stop valve, 22° 22'...
steam nozzle.

Claims (1)

[Claims] 1. A water storage tank is provided below the deaeration chamber, and the deaeration chamber and the water storage tank communicate with each other through a water supply connection pipe, and the lower end of the water supply connection pipe is connected to the water level in the water storage tank. (a) a vent pipe provided with an orifice and a vent stop valve;
b) For a boiler using a feed water deaerator equipped with a starting vent pipe equipped with a starting vent pipe stop valve connected in parallel and a heating steam pipe that supplies heated steam to the deaeration chamber. In the method for heating feed water, when starting the boiler, the start-up vent pipe stop valve is opened and a part of the heated steam is introduced into a water storage tank. Method. 2. A water storage tank is provided below the deaeration chamber, and the deaeration chamber and the water storage tank are connected through a water supply connection pipe, and the lower end of the water supply connection pipe reaches below the water surface in the water storage tank, and , between the degassing chamber and the condenser, (a) a vent pipe provided with an orifice and a vent pipe stop valve; and (b)
) In a feed water deaerator, in which a starting vent pipe provided with a starting vent pipe stop valve is interposed and connected in parallel, and a heating steam pipe for supplying heated steam to the deaeration chamber is provided, A water supply deaerator characterized in that a steam injection nozzle is provided below the water surface of a water storage tank, and a pipe line is provided for supplying a portion of the heated steam to the steam injection nozzle. 3. The water supply deaerator according to claim 2, wherein the water supply communication pipe is provided with an opening that communicates with a space above the water surface in the water storage tank.