JP4009566B2 - Dissolved oxygen reduction device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a dissolved oxygen reduction device used to prevent corrosion of metal pipes and equipment in a water circulation system that circulates and uses water in a normal pressure water tank, and in particular, heat storage that circulates and uses water as a heat storage medium. The present invention relates to a technology effective when applied to an air conditioning system.
[0002]
[Prior art]
Usually, oxygen in the atmosphere is dissolved in water at a constant rate according to its partial pressure. This dissolved oxygen causes corrosion of metal pipes and equipment. Therefore, in an air conditioning system or the like that circulates and uses water as a heat storage medium, for example, as disclosed in Patent Document 1, in order to prevent corrosion of the water circulation and use system, the dissolved oxygen in the circulating water is replaced with nitrogen, which is an inert gas, and reduced. Processing is performed.
[0003]
In patent document 1, in the water circulation utilization system which supplies the water in a water tank to the utilization side, and circulates to a water tank again, the circulation process which returns the water in the said water tank by carrying out a nitrogen substitution process separately from the water utilization circulation system. Set up the system. This circulation processing system is provided with a nitrogen injection part, a circulation pump, and a dissolution promoting tank.
[0004]
Water in the water tank is circulated by a pump, and nitrogen (nitrogen gas, hereinafter the same) is injected on the suction side of the pump. Circulating water into which nitrogen has been injected contains a large amount of nitrogen that cannot be dissolved in the form of bubbles. The bubble nitrogen is finely agitated by a circulation pump and then fed into a dissolution promoting tank to promote dissolution.
[0005]
The technique of Patent Document 1 is characterized by the installation of a dissolution accelerating tank. This dissolution accelerating tank has a function as a dissolution buffer tank (buffer tank). It takes time for nitrogen to dissolve in water. Therefore, dissolution of nitrogen is promoted by exposing the circulating water to a high static pressure in the tank for a long time. That is, it is used as a dissolution buffer tank. Thereby, even if it is a flat type water tank installed under the floor, for example, the dissolved oxygen of the water in the water tank can be reduced by nitrogen substitution.
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-342583
[Problems to be solved by the invention]
The conventional apparatus described above has been found to cause the following problems.
That is, as described above, the nitrogen injected into the circulating water is accelerated in the dissolution promoting tank disposed in the circulation processing system, and almost no dissolution can be expected in other places. The nitrogen injected on the suction side of the circulation pump is agitated by the rotor blade of the circulation pump, but a negative pressure is generated on the suction side of the circulation pump. Even if nitrogen is stirred in this negative pressure generating portion, dissolution is not promoted there, and most of it is sent to the dissolution promotion tank in the form of bubbles.
[0008]
In order to efficiently dissolve nitrogen in the dissolution accelerating tank, it is desirable to subdivide nitrogen bubbles as much as possible by sufficiently stirring them beforehand. In order to sufficiently stir the bubbles, it is necessary to rotate the rotating blade responsible for the stirring at high speed. However, when the rotor blades are rotated at a high speed, a cavitation phenomenon occurs, and a contradiction occurs that bubbles are generated.
[0009]
Eventually, the portion where the injected nitrogen is dissolved is substantially only in the above-described dissolution promoting tank (dissolution buffer tank). Circulating water fed together with nitrogen into the dissolution accelerating tank can dissolve nitrogen by being exposed to a high static pressure in the tank for a long time. In order to secure this dissolution time, the circulating water passing through the dissolution promotion tank is exposed to the dissolution tank for a long time. In other words, the circulating water may pass through the dissolution promoting tank with sufficient time.
[0010]
However, for that purpose, it is necessary to sufficiently increase the volume of the dissolution promoting tank or reduce the flow rate of the circulating water. In the former case, the apparatus becomes large and expensive, and in the latter case, there arises a problem that the processing capacity is lowered.
[0011]
The present invention has been made in view of the above problems, and an object of the present invention is to perform a nitrogen replacement treatment for preventing corrosion in a water circulation system that circulates and uses water in an atmospheric water tank. An object of the present invention is to provide a dissolved oxygen reducing device that can be made highly efficient with a low cost configuration.
[0012]
[Means for Solving the Problems]
The means of the present invention is attached to a water circulation utilization system that circulates and uses the water in the atmospheric water tank. In order to prevent corrosion of the water circulation utilization system, the amount of dissolved oxygen in the water tank is reduced by nitrogen replacement treatment. A dissolved oxygen reduction device, which is provided with a circulation treatment system for introducing water in the water tank to a water circulation path different from the utilization system and performing nitrogen replacement treatment by injection and stirring and dissolution of gaseous nitrogen, and Among the circulation processing system, the entire circulation path including at least the location of injection and stirring of the gaseous nitrogen is placed in a pressurized state at a predetermined level or higher with respect to the inside of the water tank. A circulation processing system for performing the nitrogen replacement treatment by sequentially passing through a nitrogen injecting section, a rotary blade type bubble stirring section, a dissolution buffer tank, and a degassing tank, and the entire inside of the circulation processing system The above water Pressure holding means for placing the pressure in a predetermined pressure or higher with respect to the inside, and providing a rotary vane pump in the conduit between the dissolution buffer tank and the degassing tank to increase the pressure on the degassing tank side, By providing a second nitrogen injecting portion on the suction side of the pump, bubble stirring is performed by the rotor blade of the pump, and nitrogen dissolution is promoted in the circulation path after the pump.
[0013]
By the above means, in the water circulation utilization system that circulates and uses the water in the atmospheric water tank, the nitrogen replacement treatment for preventing corrosion can be performed with high efficiency with a relatively small and low-cost configuration.
[0014]
In addition, it has a circulation processing system for performing the nitrogen replacement treatment by sequentially passing the water in the water tank through a nitrogen injection section, a rotary blade type bubble stirring section, a dissolution buffer tank, and a degassing tank and returning it to the water tank. Since the pressure holding means for placing the entire inside of the circulation processing system in a pressurized state higher than a predetermined level with respect to the inside of the water tank is provided , it is possible to promote nitrogen dissolution in both the dissolution buffer tank and the deaeration tank.
Also, by providing a rotary blade pump in the pipeline between the dissolution buffer tank and the degassing tank to increase the pressure on the degassing tank side, and by providing a second nitrogen injection part on the suction side of the pump, Air bubbles are agitated by the rotor blades of the pump and nitrogen dissolution is promoted by a circulation path after the pump. Thereby, a nitrogen substitution process can be efficiently performed in the whole circulation path.
[0015]
A pump device that pressurizes and feeds the water in the water tank of the means to the circulation processing system and a pressure-operated valve interposed at the end of the circulation processing system, the entire inside of the circulation processing system with respect to the water tank. And put it in a pressurized state higher than the specified pressure. Thereby, it is possible to place the entire circulation processing system in a predetermined pressure state with a simple and reliable configuration.
[0016]
The bubble agitation unit can be constituted by a rotary blade pump that pumps circulating water through a conduit of a circulation processing system .
[0018]
The deaeration tank is composed of a vertical cylindrical tank. By circulating the circulating water introduced from the lower side of the tank along the inner circumference of the tank, the bubbles gathered by being centrifuged near the tank axis. Is exhausted from the top. Thereby, excess gas can be efficiently separated and removed.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a schematic configuration of a dissolved oxygen reducing apparatus according to an embodiment of the present invention. The apparatus 20 shown in the figure is used by being attached to a regenerative air conditioning system that circulates and uses the water 11 of a flat normal pressure water tank 10 installed under the floor as a heat storage medium. The dissolved oxygen reducing device 20 is configured by using a second closed water circulation path 21 independent of the air conditioning system. The water circulation path 21 includes a submersible pump 22, a first nitrogen injection unit 23, a line pump 24, a dissolution buffer tank 25, a second nitrogen injection unit 26, a self-contained pump 27, a deaeration tank 28, and a primary pressure adjustment valve. 29 and the like are sequentially connected. Thereby, the circulation processing system which substitutes nitrogen, circulating the water 11 in the water tank 10 is comprised. Indicated flow meters 31 and 32 are disposed on the discharge side of the submersible pump 22 and the inflow side of the primary pressure regulating valve 29, respectively, so that the amount of circulating water (treated water) in the circulation processing system can be monitored. Yes.
[0020]
In FIG. 1, the water 11 in the water tank 10 is pumped up and pressurized by a submersible pump 22 installed in the water tank 10, and sent to the first nitrogen injecting unit 23. As shown in FIG. 2, the first nitrogen injection part 23 is configured by using a T-joint in which a thin branch pipe part 23b is connected to a straight pipe part 23a forming a flow path of circulating water at a right angle. Nitrogen is injected under pressure from the end of the portion 23b. The branch pipe portion 23b is connected to a nitrogen generation source (not shown) via a pressure-resistant connector and a pressure-resistant tube. As the nitrogen generation source, a nitrogen generation apparatus that supplies nitrogen gas separately from the atmosphere is preferably used, but a nitrogen cylinder may be used.
[0021]
The injected nitrogen is bubbled and mixed into the circulating water. The nitrogen bubbles are pressurized and agitated by the rotary blades (rotary blades) of the line pump 24 and subdivided, and then fed into the dissolution buffer tank 25 together with the circulating water further pressurized by the pump 24. The pump 24 is of a rotary blade type (rotary blade type), and the rotary blade is originally for carrying and driving (pumping) water, but here also serves as a bubble stirring unit.
[0022]
The dissolution buffer tank 25 is configured using a vertical tank. The inside of the tank can store only circulating water in a substantially full state by an automatic air vent valve 25a provided in the upper part of the tank. The circulating water into which nitrogen has been injected is introduced into the dissolution buffer tank 25 so as to stay once, and then passes through a predetermined dissolution acceleration time.
[0023]
The circulating water that has passed through the dissolution buffer tank 25 is re-injected with nitrogen by the second nitrogen injecting section 26 and then fed into the deaeration tank 28 by the self-contained pump 27. The second nitrogen injecting section 26 is installed on the suction side of the self-contained pump 27 as shown in FIG. Nitrogen is pressurized and injected into the suction side of the pump 27 through the flow meter 26a. The injected nitrogen is bubbled and mixed into the circulating water. The nitrogen gas newly mixed here is pressurized and agitated by the rotary blades of the self-contained pump 27 and then subdivided, and then fed into the deaeration tank 28 together with the circulating water. Also in this case, the pump 27 is a rotary blade type (rotary blade type), and the rotary blade also serves as a bubble stirring unit.
[0024]
As with the buffer tank 25, the deaeration tank 28 is configured using a vertical cylindrical tank. Circulating water is introduced in the circumferential direction from below the tank. By circulating the circulating water introduced into the tank along the inner circumference of the tank, bubbles are collected by being centrifuged near the central axis of the tank. The bubbles separated here are surplus gas left by dissolution saturation, and this surplus gas is exhausted from the automatic air vent valve 28a at the upper part of the tank.
[0025]
In the tank, in order to generate the swirling flow, the circulating water is introduced so as to flow along the inner peripheral surface of the tank. Circulating water from which bubbles are separated and removed gathers near the inner peripheral surface of the tank. The degassed circulating water reaches the primary pressure regulating valve 29 through the pipe line 33 and the indicator flow meter 32.
[0026]
An automatic air vent valve 33a is installed at the top of the pipe line 33, where final air venting is performed. The primary pressure regulating valve 29 is a pressure operating valve that holds a predetermined pressure, and is also called a back pressure valve. The primary pressure regulating valve (back pressure valve) 29 allows the circulating water to pass through in a state where the pressure on the inflow side is maintained at a predetermined pressure. As a result, a predetermined pressure state is generated in the entire circulation processing system. The circulating water that has passed through the primary pressure regulating valve 29 is returned to the water tank 10.
Excess nitrogen exhausted from the air vent valves 25 a, 28 a, 33 a is led to an exhaust pipe and collected, and sent into the water tank 10.
[0027]
FIG. 4 shows a pressure distribution state in the circulation processing system described above. In the above-described circulation processing system, the entire circulation path 21 from the discharge side of the submersible pump 22 to the primary pressure adjustment valve 29 is maintained in a pressurized state of a predetermined level or more by the primary pressure adjustment valve 29. Further, the pressure in the circulation path 21 is increased stepwise by the line pump 24 and the self-contained pump 27 in the circulation direction.
[0028]
In the specific example shown in the figure, the water (heat storage medium) 11 stored in the atmospheric water tank 10 under atmospheric pressure (0.0 kg / cm ² ) is 2.0 kg / cm ² on the discharge side of the submersible pump 22. It is pressurized to the position. A first nitrogen injection is performed at this pressure portion. Thereafter, the circulating water is pressurized to around 4.0 kg / cm ² by the line pump 24 and fed into the dissolution buffer tank 25. The circulating water in the dissolution buffer tank 25 gradually decreases in pressure due to the presence of bubbles and piping frictional resistance. However, after passing through the dissolution buffer tank 25, it is pressurized to about 5-6 kg / cm ² by the self-contained pump 27 and fed into the deaeration tank 28. Some pressure gradually decreases due to piping frictional resistance between the deaeration tank 28 and the primary pressure regulating valve (back pressure valve) 29, but the primary pressure regulating valve 29 maintained a pressure (back pressure) of 5 kg / cm ² or more. It is supposed to be. Thus, the water 11 drawn up from the water tank 10 is returned to the water tank 10 through the circulation path 21 in a state where the water 11 is kept in a pressurized state of at least 2 kg / cm ² or more.
[0029]
As described above, the dissolved oxygen reducing device 20 of this embodiment passes the water in the water tank 10 through the nitrogen injection part, the rotary blade type bubble agitation part, the dissolution buffer tank, and the deaeration tank in order into the water tank 10. In addition to having a circulating treatment system to be returned, and equipped with pressure holding means for placing the entire inside of the circulating treatment system in a pressurized state at a predetermined level or higher with respect to the water tank 10, the dissolution of nitrogen is promoted by the dissolution buffer tank 25. It is performed not only in the inside but in almost the entire circulation processing system.
[0030]
Here, if it is attempted to accelerate dissolution only in the dissolution buffer tank 25, the time required for nitrogen dissolution must be secured only by the passage time in the dissolution buffer tank. It is necessary to sufficiently increase the tank volume or reduce the flow rate of the circulating water. In the former case, the apparatus becomes large and expensive, and in the latter case, the processing capacity decreases.
[0031]
On the other hand, in the above embodiment, since the dissolution of nitrogen is promoted almost entirely in the circulation processing system, even if the dissolution time in the dissolution buffer tank 25 is not necessarily sufficient, a sufficient dissolution time in the entire circulation processing system. Can be secured. Thereby, the process of reducing dissolved oxygen by nitrogen substitution can be performed with high efficiency by a relatively small and low-cost configuration.
[0032]
According to the knowledge of the present inventor, the dissolution of nitrogen in the circulating water approaches the saturation state after a predetermined time. Therefore, it was found that the nitrogen dissolution promotion time should be secured for the predetermined time or more. This dissolution accelerating time is a time sufficient to dissolve gaseous nitrogen, and is preferably determined in consideration of the initial cost, running cost, and the like. For example, by the breakdown voltage standards required by JIS withstand voltage test and less than 7 kg / cm ^2, as compared with the case where the withstand voltage reference was 7 kg / cm ² or more, piping, flanges, joints, etc. The thickness, the driving The power can be reduced by one rank and the cost can be reduced. In this case, the cost can be reduced by setting the dissolution promotion time to 2 to 6 minutes, preferably about 4 minutes. However, it was possible to sufficiently dissolve gaseous nitrogen. If the dissolution accelerating time is shorter than 2 minutes, the dissolution is insufficient, and if it is longer than 6 minutes, the amount of retained water must be increased.
[0033]
Note that, if it is attempted to secure this dissolution acceleration time only with the dissolution buffer tank, as described above, the apparatus is increased in size and cost, or the processing capacity is lowered. If it is made to share with the air tank 28 (for example, every 2 minutes), as above-mentioned, size reduction of an apparatus, cost reduction, and a processing capability improvement can be achieved.
[0034]
In the above embodiment, the rotary blade pump 27 is provided in the conduit between the dissolution buffer tank 25 and the deaeration tank 28 to increase the pressure on the deaeration tank 28 side, and the second side is connected to the suction side of the pump 27. By providing the nitrogen injecting section 26, the bubble agitation by the rotor blades of the pump 27 and the nitrogen dissolution promotion are performed in the circulation path after the pump 27, respectively. Thereby, after the circulating water passes through the dissolution buffer tank 25, more nitrogen is dissolved, and dissolved oxygen is reduced accordingly.
[0035]
Nitrogen bubbles injected into the circulating water are stirred and subdivided by the rotor blades of the pumps 24 and 27 in order to promote their dissolution, but in the above embodiment, the stirring is performed under pressurized conditions. The cavitation phenomenon due to the rotation of the rotor blade is less likely to occur. Thereby, rotation of a rotary blade can be sped up and the melt | dissolution promotion effect by stirring of a bubble can be heightened.
[0036]
FIG. 5 shows a detailed configuration example of the dissolution buffer tank 25. The dissolution buffer tank 25 is configured by using a vertical cylindrical tank, and an inlet 25b for circulating water is provided at the center of the bottom surface of the tank, and an outlet 25d is provided at the lower part of the side surface. The inflow port 25b communicates with an intubation tube 25c that rises vertically from the bottom at the center of the tank. The circulating water introduced from the inflow port 25b is guided to the tank upper part from the inner side of the inner intubation tube 25c, and then circulates to the outer side of the inner intubation tube 25c and is guided to the outlet port 25d. By such a detour route, the time required for dissolution promotion is uniformly given to the whole circulating water. Reference numeral 25e denotes a pressure gauge mounting pipe, and 25f denotes an automatic air vent valve mounting pipe.
[0037]
As mentioned above, although this invention was demonstrated based on the typical Example, this invention can have various aspects other than having mentioned above. For example, the first and second nitrogen injecting portions 23 and 26 may have either the configuration shown in FIG. 2 or FIG.
[0038]
【The invention's effect】
According to the present invention, in a water circulation utilization system that circulates and uses water in an atmospheric water tank, nitrogen replacement treatment for corrosion prevention can be performed with a relatively small and low cost configuration with high efficiency. A small, low-cost, high-efficiency dissolved oxygen reduction device is realized.
[Brief description of the drawings]
FIG. 1 is a piping system diagram showing a schematic configuration of a dissolved oxygen reducing apparatus according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a configuration example of a main part of a first nitrogen implantation part.
FIG. 3 is a cross-sectional view showing a configuration example of a main part of a second nitrogen implantation part.
4 is a schematic diagram showing a relationship between a pressure distribution state and a circulation path in the circulation processing system shown in FIG. 1. FIG.
FIG. 5 is a side sectional view showing a detailed configuration example of a main part of a dissolution buffer tank.
[Explanation of symbols]
10 Water tank 11 Water (heat storage medium)
20 Dissolved oxygen reduction device 21 Water circulation path 22 Submersible pump 23 First nitrogen injection part 23a Straight pipe part 23b Branch pipe part 23c Flow meter 24 Line pump 25 Dissolution buffer tank 25a Automatic air vent valve 25b Inlet 25c Inner pipe 25d Outlet 25e Pressure gauge mounting pipe 25f Automatic air vent valve mounting pipe 26 Second nitrogen injection part 26a Flow meter 27 Self-contained pump 28 Deaeration tank 28a Automatic air vent valve 29 Primary pressure regulating valve 31, 32 Indicating flow meter 33 Pipe line 33a Automatic air vent valve

Claims (4)

This is a dissolved oxygen reduction device attached to a water circulation system that circulates and uses the water in the atmospheric tank, and reduces the amount of dissolved oxygen in the water tank by nitrogen replacement treatment to prevent corrosion of this water circulation system. And
In addition to installing a circulation processing system for guiding the water in the water tank to a water circulation path different from the utilization system and performing nitrogen replacement treatment by injection and stirring and dissolution of gaseous nitrogen, at least the above-mentioned circulation treatment system The entire circulation path including the place of injection and stirring of gaseous nitrogen is placed in a pressurized state above a predetermined level with respect to the inside of the water tank ,
The water in the water tank has a circulation treatment system for performing the nitrogen replacement treatment by sequentially passing the water in the water tank through a nitrogen injecting section, a rotating blade type bubble stirring section, a dissolution buffer tank, and a degassing tank and returning the water into the water tank. Pressure holding means for placing the entire circulation processing system in a pressurized state above a predetermined level relative to the inside of the water tank,
A rotary blade pump is provided in a pipe line between the dissolution buffer tank and the deaeration tank to increase the pressure on the deaeration tank side, and a second nitrogen injecting portion is provided on the suction side of the pump. The dissolved oxygen reduction device is characterized in that air bubbles are stirred by the rotor blades and nitrogen dissolution is promoted in the circulation path after the pump. 2. The entire inside of the circulation processing system according to claim 1, wherein the entire inside of the circulation processing system is contained in the water tank by a pump device that pressurizes and feeds water in the water tank to the circulation processing system, and a pressure operating valve that is interposed at a terminal portion of the circulation processing system. The dissolved oxygen reducing device is characterized in that it is placed in a pressurized state at a predetermined level or higher. 3. The dissolved oxygen reducing apparatus according to claim 1, wherein the bubble agitating unit is constituted by a rotary blade pump that pumps circulating water through a conduit of a circulation processing system.   The deaeration tank according to any one of claims 1 to 3, wherein the deaeration tank is constituted by a vertical cylindrical tank, and the tank shaft is formed by swirling the circulating water introduced from the lower side of the tank along the inner periphery of the tank. Dissolved oxygen reduction device characterized in that bubbles collected by centrifugation near the heart are exhausted from above.

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