JPH08193284A - Method for preventing corrosion of water circulating line and device therefor - Google Patents

Abstract

PURPOSE: To decrease the amt. of dissolved oxygen to a specified level with a relatively small amt. of gaseous nitrogen in a short time by circulating the water in the water tank of a water circulating line with a nitrogen replacing pump, supplying gaseous nitrogen and replacing the dissolved oxygen in the water with the nitrogen under agitation and pressurization. CONSTITUTION: A heating-medium use circulating water 2 stored in a water tank 1 is circulated to a heat-source device 6 through pipelines 3 and 4 and a pump 5 on the heat-source side, cooled or heated. The water 2 is circulated to an air conditioner 10 through pipelines 7 and 8 and a pump 9 on the utilization side, heat-exchanged and supplied on the load side of a building. At this time, a nitrogen replacing device 11 is connected to the tank 1, the water 2 is circulated by a nitrogen replacing pump 14 through pipelines 12 and 13, gaseous nitrogen is supplied to the suction side of the pump through a cylinder 16 and a pressure reducing valve 15, the dissolved oxygen is replaced with the nitrogen under pressurization and agitation, and the dissolved oxygen content is lowered. Consequently, the amt. of dissolved oxygen is decreased at a low cost to a level where corrosion is not caused.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corrosion prevention method for preventing corrosion of metal pipes, equipment, etc. in a water circulation system in which water in a water tank open to the atmosphere is circulated again to the water tank. And equipment.

[0002]

2. Description of the Related Art Conventionally, in a water circulation system, there is a problem that metal pipes, pumps, and other equipment are corroded by oxygen dissolved in water. Methods such as anticorrosion are used. However, in the method of adding a rust preventive agent, the rust preventive agent does not have a high rust preventive effect for all metals, so in a water circulation system composed of various metal pipes and equipment, It is difficult to select, and it is difficult to control the concentration due to the consumption of the rust preventive, and the effect is small despite the high running cost. In addition, the method based on cathodic protection requires a large number of electrodes to be installed in a distributed manner in order to effectively cover the entire water circulation system, resulting in an extremely high initial cost.
In order to always obtain a high effect in the entire water circulation system, it is necessary to maintain and manage the electrodes dispersedly installed in the pipes and the equipment, and as a result, there is a problem that the running cost is high.

Therefore, there is known a technique for preventing corrosion by a method of removing dissolved oxygen by a vacuum degassing method or a method of replacing dissolved oxygen with nitrogen when circulating water is supplied into the pipe ( Air conditioning and sanitary engineering, Vol. 67, No. 10
No. 773 to 781 "Applying degassing and corrosion protection method to equipment piping".

[0004]

However, in the above vacuum degassing method, the apparatus cost increases and
There is a problem that the vacuum pump always needs to be operated during the water supply operation, and the nitrogen replacement method has a problem that a large amount of nitrogen gas is required, resulting in an increase in cost. Furthermore, in any case, in a water circulation system in which the water tank is opened to the atmosphere and the water surface is always wavy, like a heat storage type air conditioner that stores the water in the water tank and circulates the stored water for cooling and heating. Since water after deaeration or replacement acts to dissolve oxygen in the atmosphere, even if a low dissolved oxygen saturation is obtained by deaeration or replacement, it is extremely difficult to maintain this. There is.

The present invention is to solve the above-mentioned conventional problems, and is a simple method and apparatus in a water circulation system of a type in which water in a water tank open to the atmosphere is circulated to the water tank again through piping. It is an object of the present invention to provide a corrosion prevention method and apparatus capable of reducing the amount of dissolved oxygen to a level at which the influence of corrosion is eliminated at low cost.

[0006]

Therefore, a method for preventing corrosion of a water circulation system according to the present invention is a water circulation system in which water in a water tank open to the atmosphere is circulated again to the water tank through a pipe. While circulating water with a nitrogen displacement pump, supply nitrogen gas to the suction side of the pump,
Dissolved oxygen in the water is replaced with nitrogen gas by stirring and pressurizing with the pump, and the corrosion inhibitor for a water circulation system of the present invention is a water tank that is open to the atmosphere and is again passed through a pipe to the water tank. In a water circulation system of a system of circulating the water in the water tank, a nitrogen substitution pump for circulating the water in the water tank, a nitrogen gas supply device supplied to the suction side of the pump, and a large number of floating so as to cover the water surface of the water tank. It is characterized by having a floating ball with a collar.

[0007]

It has been conventionally known that when a large amount of fine nitrogen gas bubbles are blown into water, a part of oxygen dissolved in the water is replaced with nitrogen. However, it was not possible to reduce the amount of the effect of corrosion due to dissolved oxygen to 0.5 ppm or less even after blowing for a long time. In the present invention, the dissolved oxygen in water is replaced with nitrogen gas by stirring and pressurizing with a pump, and the amount of dissolved oxygen can be reduced to a level where the influence of corrosion is eliminated in a short time with a relatively small amount of nitrogen gas.

Further, due to the action of the floating float with a collar itself and the excess nitrogen gas accumulated on the lower surface of the floating float with a collar, the water surface of the water tank is shielded from the atmosphere, so that the dissolution of oxygen can be prevented.
The amount of dissolved oxygen can be maintained at a low level.

Further, when the present invention is applied to a heat storage type air conditioner, due to the action of the floating float with a collar and the surplus nitrogen gas accumulated on the lower surface of the floating float with a collar, the heat insulation performance of the circulating water in the water tank is improved. Is improved.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram showing one embodiment of a method and apparatus for preventing corrosion of a water circulation system of the present invention. In addition, although the present embodiment applies the present invention to a heat storage type air conditioner, the present invention is not limited to this, and the water in the water tank opened to the atmosphere is returned to the water tank through the pipe. The circulation method can be applied to all water circulation systems.

In FIG. 1, a water tank 1 forming a heat storage tank
Is constructed in the basement of the building, for example, and the circulating water 2 for the heat medium is stored inside. The circulating water 2 in the aquarium 1 is pipes 3, 4
And the heat source side pump 5 circulates the heat source device 6.
The heat source device 6 is a known heat pump device or a device that combines a refrigerator and a boiler, and cools or heats the circulating water 2. The cooled or heated circulating water 2 is circulated to the air conditioner 10 by the pipes 7 and 8 and the use side pump 9. The air conditioner 10 is a heat exchanger, and is configured to supply cold / hot water that has exchanged heat with the circulating water 2 to the load side of the building.

A nitrogen replacement device 11 is connected to the water tank 1. The nitrogen replacement device 11 is a nitrogen gas supply device including a nitrogen replacement pump 14 connected through pipes 12 and 13, a pressure reducing valve 15 for supplying nitrogen gas to the suction side of the nitrogen replacement pump 14, and a nitrogen gas cylinder 16. It consists of and. The nitrogen filled in the nitrogen gas cylinder 16 does not need to be pure nitrogen, and may be nitrogen gas manufactured by a nitrogen gas separation filter.

The operation will be described. When the nitrogen displacement pump 14 is operated and the circulating water 2 is circulated, if nitrogen gas is supplied to the pump suction side from the nitrogen gas supply devices 16 and 15 to such an extent that the operation of the pump is not significantly impaired, the water is agitated by the pump. Is applied and is pressurized by the wings of the pump, it acts on the side that increases the amount of gas saturation,
When the surroundings are filled with fine nitrogen gas particles, oxygen is replaced by nitrogen due to this pressure stirring action. Although not shown, a venturi tube may be provided at the pump suction port to atomize the sucked nitrogen gas so that the pump sucks the gas in order to enhance the effect. In this way, the circulating water 2 in the water tank 1 gradually becomes a state in which oxygen is replaced by nitrogen and the proportion of dissolved oxygen is reduced. The degassed oxygen and excess nitrogen gas are released from the water surface of the water tank 1 into the atmosphere.

However, since water has a characteristic that oxygen is more likely to be dissolved than nitrogen, water that is weakly substituted with nitrogen acts such that dissolved nitrogen is replaced with oxygen again when it comes into contact with the atmosphere. Therefore, in order to prevent the replacement of oxygen in the atmosphere and to keep the surplus nitrogen gas under nitrogen substitution under the water surface, in the present invention, a large number of water is circulated on the water surface of the circulating water 2 in the water tank 1. A structure is adopted in which the floating ball 17 with a collar is floated so as to cover the water surface without a gap and to shield the atmosphere.

2 and 3 show an embodiment of a floating ball with a collar according to the present invention. FIG. 2 (A) is a sectional view of the floating ball with a collar and FIG. 2 (B) is a plan view of the floating ball with a collar. 2 (C) and FIG. 2 (D) are sectional views for explaining the action when the floating ball with a collar is put on the water surface, and FIG. 3 is a state in which the water surface of the water tank is covered with a plurality of floating balls with a collar. FIG.

2 (A) and 2 (B), the collar-attached floating ball 17 is provided on the disk-shaped thin plate 20 and above and below the thin plate 20, and has a smaller diameter than the thin plate 20 and a hollow interior. And an upper hemisphere 21 and a lower hemisphere 22, a flange portion 23 formed on the outer periphery of the thin plate 17, a weight 24 movably incorporated in the lower hemisphere 22 side of the thin plate 20, and a bottom portion of the lower hemisphere 22. It is composed of a water injection hole 25 and an air vent hole 26 formed in the upper part of the lower hemisphere 22. The shapes of the thin plate 20, the upper hemisphere 21, and the lower hemisphere 22 are not limited to circles and spheres, respectively, and various shapes similar thereto can be adopted.

Laminate 20, upper hemisphere 21 and lower hemisphere 2
2 is manufactured from a resin having an oxygen barrier property. As a preferred embodiment of the collar-attached floating sphere 17, a PET (polyethylene terephthalate) plate is used as the thin plate 20, PET foamed resin is used as the upper hemisphere 21 and the lower hemisphere 22, and the upper hemisphere 21 and the lower hemisphere 22 are thin plates. Two
It is manufactured by heat welding to 0. Since the specific gravity of the thin plate 20 made of a PET plate is larger than 1, the upper hemisphere 21 and the lower hemisphere 2
The specific gravity of 2 is smaller than 1, and the specific gravity of the weight 24 is smaller than 1, so that the thin plate 20 that is submerged in a single body is adjusted to float on the water surface.

The floating ball 17 with a collar having an oxygen barrier property is
It can be produced by using a resin having an oxygen barrier property as exemplified below, or when another resin is used, it can be produced by laminating the above resin having an oxygen barrier property. . Examples of the resin having an oxygen barrier property include polyethylene terephthalate, polybutylene terephthalate, polyester, polyvinylidene chloride, polyacrylonitrile, modified polyamide, vinyl alcohol and the like, but particularly polyethylene terephthalate, polybutylene from the viewpoint of toughness and durability. Terephthalate is preferred.

Further, as the material for forming the floating ball with a collar, in addition to the above-mentioned resin having an oxygen barrier property, a material obtained by foaming these, polystyrene, polypropylene,
By laminating the above-mentioned oxygen barrier resin on polyethylene or these foamed products, and combining them, a disk-shaped thin plate, and an upper hemisphere and a lower part with a hollow inside formed above and below the thin plate As the flange portion formed on the outer periphery of the hemisphere or the thin plate, the specific gravity can be arbitrarily adjusted and used.

The collar-attached floating ball 17 is introduced from a manhole (not shown) after circulating water is poured into the heat storage tank 1. At this time, it is important that the lower hemisphere 22 is on the lower side and the circulating water 2 is immersed in the lower hemisphere 22 so that the thin plate 20 is horizontal. A gap is created between the floating balls 17 with the collars to prevent the shielding performance from deteriorating. Therefore, the weight 24 is provided with a floating ball 17 with a collar.
It plays the function of ensuring that the up and down position is correct. That is, as shown in FIG. 2C, the lower hemisphere 22
When it falls to the surface of the water with the upper part of the upper part of the lower part, the weight 24 rolls and moves in the lower hemisphere 22, so that the lower hemisphere 22 is rotated so as to be positioned on the lower side as shown by the arrow in the figure, and then the As shown in FIG. 2 (D), in the lower hemisphere 22,
The circulating water 2 is flooded by the action of the water injection hole 25 and the air vent hole 26.

As shown in FIG. 3, the collar-attached floating balls 17 have the collar portions 20 of equal size and overlap each other to cover the surface of the water without any gap, and the bottom surface of the collar-attached floating balls 17 has an excess. Since nitrogen gas is retained, it is possible to reliably shield the atmosphere from the atmosphere, prevent the oxygen from being replaced again, and maintain the dissolved oxygen at a low level. However, the floating ball with a collar 17
Between the wall of the water tank 1 and the pipes 3 and 4, and the floating ball with a collar 1
There is a slight gap between 7 and 7. In order to further fill this slight gap and further improve the shielding performance from the atmosphere, the floating tip 18 is floated in another embodiment of the present invention. The floating tip 18 is made of a resin having an oxygen barrier property, preferably a resin obtained by foaming the PET.

FIGS. 4A to 4E show a floating chip 1
8 shows various shapes, and the upper figure shows a plan view and the lower figure shows a side view. Various shapes such as a plate shape, a spherical shape, and a square shape are adopted, but in the case of a plate shape, the chips 18 are made spherical so that they do not adhere to the chips 18 or the thin plate 20 of the flanged floating ball 17 due to the surface tension of water. The shape is adopted.

When the present invention is applied to a heat storage type air conditioner, surplus nitrogen gas is used as a reinforcement to suppress and maintain the mixed oxygen, which is expected to be mixed with makeup water after nitrogen replacement, below a control value. It is preferable to carry out during the heat storage time zone where excess nitrogen can be stored in the lower part of the thin plate 20 of the flanged floating ball 17 so as not to flow into the inside and obstruct the flow velocity in the pipe.

Next, the effect of nitrogen substitution according to the present invention will be described with reference to FIGS. 5 and 6 show an experiment according to a comparative example, FIG. 5A is a schematic diagram of an experimental apparatus, and FIG. 6B is a diagram showing experimental results.

The experiment in the comparative example of FIG.
m, width 1800 m, height 600 mm water tank 31,
An air curtain that circulates the water in the water tank 31 from the distributor 33 by the circulation pump 32, and installs a total of five air curtain members 34 on the bottom surface of the water tank 31 and in the distributor 33 so as to discharge nitrogen bubbles from the air curtain member 34. The system was adopted, and no floating ball with a collar was thrown in. The initial water temperature was 25.6 ° C, the amount of dissolved oxygen was 6.6 ppm, and the nitrogen gas release condition was 20 liters / mi.
n, 0.5 kgf / cm ² (gauge pressure). According to this method, the amount of dissolved oxygen decreased only to 2.5 ppm. The supply of nitrogen gas is stopped at point X.

In the experiment in the comparative example of FIG. 6, a submersible pump 35 is separately installed in the water tank 31, a venturi pipe 36 is attached to the discharge side of the submersible pump 35, and nitrogen gas is supplied to the venturi pipe portion to generate fine bubbles. The discharging method and the air curtain method by the distributor 33 were used together, and a floating ball with a collar was put in. The initial water temperature was 25.0 ° C., the amount of dissolved oxygen was 5.8 ppm, the nitrogen gas releasing conditions were 10 liter / min, and 0.8 kgf / cm ² (gauge pressure). According to this method, it was possible to reduce the amount of dissolved oxygen as compared with the comparative example of FIG.
It could not be reduced to 0.5 ppm or less where the influence of corrosion is eliminated. At the point X, the supply of nitrogen gas is stopped, and Y
At that point, the supply of nitrogen gas is restarted.

FIG. 7 shows an experiment in the present invention.
FIG. 7A is a schematic diagram of an experimental device, and FIG. 7B is a diagram showing experimental results. In this experiment, only a nitrogen forced pressurization stirring system in which nitrogen gas is supplied to the suction side of the circulation pump 32 is adopted, and a floating ball with a collar is introduced. The initial water temperature is 20.7 ° C,
The dissolved oxygen amount was 6.0 ppm, the nitrogen gas releasing conditions were 5 liter / min, and 0.2 kgf / cm ² (gauge pressure). As shown in FIG. 7B, the amount of dissolved oxygen could be reduced to 0.5 ppm or less at which the influence of corrosion was eliminated, in a short time of 5 hours with a relatively small amount of nitrogen gas. Also, at the point X (after 6 hours), the dissolved oxygen amount becomes 0.0 ppm 48 hours after the supply of the nitrogen gas is stopped, and then 140
It was possible to maintain the level of 0.5 ppm or less until the time elapsed, which means that it is not necessary to constantly perform the nitrogen replacement operation, and it is possible to maintain the level at which the influence of corrosion is eliminated in the intermittent operation. .

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing one embodiment of a water circulation system corrosion prevention method and apparatus of the present invention.

FIG. 2 shows an embodiment of a floating ball with a collar according to the present invention, FIG. 2 (A) is a sectional view of the floating ball with a collar, FIG. 2 (B) is a plan view of the floating ball with a collar, and FIG. 2 (C). And FIG. 2D is a cross-sectional view for explaining the action when the collar-attached floating ball is thrown into the water surface.

FIG. 3 is a plan view showing a state in which the water surface of the water tank is covered with a plurality of collared floating balls.

FIG. 4 (A) to FIG. 4 (E) show various shapes of the floating chip in the embodiment of the present invention, wherein the upper diagram shows a plan view and the lower diagram shows a side view.

FIG. 5 shows an experiment according to a comparative example, FIG. 5 (A) is a schematic diagram of an experimental apparatus, and FIG. 5 (B) is a diagram showing experimental results.

FIG. 6 shows an experiment in a comparative example, FIG. 5 (A) is a schematic diagram of an experimental apparatus, and FIG. 5 (B) is a diagram showing experimental results.

FIG. 7 shows an experiment in the present invention, FIG. 7 (A) is a schematic diagram of an experimental apparatus, and FIG. 7 (B) is a diagram showing experimental results.

[Explanation of Codes] 1 ... Water tank, 2 ... Circulating water, 3, 4, 7, 8, 12, 13, ...
Piping 5 ... Heat source side pump, 6 ... Heat source device, 9 ... Utilization side pump,
10 ... Air conditioner 11 ... Nitrogen replacement device, 12 ... Nitrogen replacement pump, 15 ...
Pressure reducing valve 16 ... Nitrogen gas cylinder, 17 ... Collar floating ball, 18 ... Floating tip 20 ... Thin plate, 21 ... Upper hemisphere, 22 ... Lower hemisphere, 23 ...
Collar part, 24 ... Weight 25 ... Water injection hole, 26 ... Air vent hole

Claims (5)

[Claims] 1. A water circulation system of a type in which water in a water tank open to the atmosphere is circulated again in the water tank via a pipe, and the water in the water tank is circulated by a nitrogen displacement pump, and nitrogen is supplied to a suction side of the pump. A method for preventing corrosion of a water circulation system, which comprises supplying gas and substituting nitrogen gas for dissolved oxygen in water by stirring and pressurizing with the pump. 2. In a water circulation system of a type in which water in a water tank open to the atmosphere is circulated again in the water tank via a pipe, a nitrogen substitution pump for circulating water in the water tank and a suction side of the pump are supplied. An apparatus for preventing corrosion of a water circulation system, comprising: a nitrogen gas supply device for supplying water; and a plurality of floating balls with collars suspended so as to cover the water surface of the water tank. 3. The flanged floating ball is a disk-shaped thin plate made of a resin having an oxygen barrier property, an upper hemisphere and a lower hemisphere provided above and below the thin plate and having a hollow interior, and the thin plate. A flange portion formed on the outer circumference of the lower hemisphere, a weight movably incorporated in the lower hemisphere side, a water injection hole formed in the bottom portion of the lower hemisphere, and an air vent hole formed in the upper portion of the lower hemisphere. The corrosion prevention device for a water circulation system according to claim 2, further comprising: 4. The corrosion prevention device for a water circulation system according to claim 2, wherein a large number of floating chips having an oxygen barrier property are floated on the water surface of the water tank. 5. The heat storage type air conditioner according to claim 2, wherein the water circulation system is a heat storage type air conditioner of a system that stores water in a water tank and circulates the stored heat for cooling and heating. Corrosion prevention device for water circulation system described.