JP2502411B2 - Heat storage device and anticorrosion method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat storage device for cooling and heating and a method of preventing corrosion thereof, and more particularly to a heat storage device using a heat storage medium mainly composed of a high temperature concentrated halide aqueous solution, and means and method for preventing corrosion of a metal material. Regarding

[0002]

2. Description of the Related Art As a heat storage device, for example, the actual development of Sho 62-346
As disclosed in Japanese Patent Publication No. 69, a concentration difference utilization method utilizing the heat of hydration by concentration and dilution of a concentrated halide aqueous solution,
Since the operating temperature and output temperature can be set arbitrarily, it has become an extremely effective means today. This type of heat storage device uses water as a refrigerant and a concentrated halide aqueous solution as a heat storage medium. Particularly, as the heat storage medium, an aqueous halide solution such as lithium bromide or calcium chloride is used from the viewpoint of economy and heat storage density. Used alone or as a mixture.

These aqueous solutions are strongly corrosive in nature, and their corrosiveness becomes remarkably high at a high temperature (120 ° C.) and concentrated (55 wt%) solution which is a normal operating condition of a heat storage device. Therefore, conventionally, an inorganic chromate in the heat storage medium,
Inhibitors such as nitrates, molybdates, and organic benzotriazole are added to prevent corrosion of the heat storage device.

[0004]

The solubility of these conventional inhibitors in water is not so high originally, and in addition, the heat storage medium is a concentrated halide aqueous solution, so that the solubility is generally low. Moreover, since the temperature of the medium is low in the heat storage device and the concentration of the inhibitor in the entire device is determined by the solubility in the medium tank having a high concentration, there is a problem that the concentration of the added inhibitor is extremely small.

Further, these inhibitors suppress corrosion by forming a compound film that is hardly soluble in a metal material in an organic system and a passive film on the surface of a metal material in an inorganic system. Therefore, the inhibitors in the circulation system are consumed, and the ability to suppress corrosion gradually decreases with the passage of time.
Therefore, it is necessary to manage the inhibitor of the heat storage device, but since the inside of the device is in a depressurized state and has a fully sealed structure,
Sampling cannot be done easily, and the concentration of inhibitor is investigated by chemical analysis etc. with the operation temporarily stopped, but this method temporarily breaks the low pressure state,
Since the progress of corrosion due to the invasion of oxygen occurs, it has been necessary to replenish the inhibitor frequently, and the replenishment method itself has been a problem along with the troublesome sampling.

Further, in the absorption refrigerator, as a method for controlling the inhibitor, a method of measuring the pressure change in the system due to corrosion and detecting the inhibitor concentration to control the inhibitor concentration (Japanese Patent Laid-Open No. 52-37257) and A method of measuring the amount of hydrogen generated by corrosion, detecting the inhibitor concentration based on the amount of hydrogen, and maintaining the inhibitor concentration (JP-A-52-46).
No. 552) is known. However, it is undeniable that the operation is complicated and the accuracy of the inhibitor addition timing is limited.

An object of the present invention is to provide a simple and inexpensive continuous inhibitor supply means capable of eliminating the above-mentioned drawbacks of the prior art and maintaining stable corrosion control for a heat storage device for a long period of time. Is to provide a method.

[0008]

[Means for solving the problems] Normally, in the concentrator, due to the system, high temperature (120 ° C) during concentration and low temperature (30 ° C) during dilution
Repeat the temperature cycle of. Therefore, even if the inhibitor is added in an amount sufficient for anticorrosion at a high temperature, the solubility of the inhibitor becomes insufficient at a low temperature, and an extra inhibitor precipitate is generated. From these points, it is necessary to find out the addition concentration of the inhibitor which has a satisfactory anticorrosive effect even in a high temperature state and a solubility in a low temperature. Also, in general,
In the heat storage device, the amount of inhibitor dissolved in the heat storage medium is determined by the concentration and temperature of the medium. Also,
The inhibitor in the medium in the apparatus forms a film and is consumed to suppress the corrosion of the metal material. It is necessary to continuously replenish this depleted portion and maintain the initial inhibitor concentration.

The present inventors conducted various experiments in order to achieve the above-mentioned objects, and obtained the following findings.
That is, an experiment was conducted by adjusting calcium chloride and lithium bromide as a heat storage medium liquid at a mixing ratio of 1: 1 and a concentration of 55 wt%, and adding benzotriazole as an inhibitor thereto. A carbon steel (SS-41) was subjected to a corrosion test at 120 ° C for 200 hours to investigate the effect of benzotriazole concentration on the corrosion amount of carbon steel. The result is shown in FIG. The corrosion test was performed after deaeration so that the atmosphere (oxygen) was not affected during the test. From the figure, the benzotriazole concentration
It can be seen that the occurrence of pitting corrosion and the amount of corrosion are large when the content is 0.05 wt% or less, and that the addition concentration of benzotriazole greatly affects the corrosion of carbon steel. By adding benzotriazole in an amount of 0.05 wt% or more, the amount of corrosion was 2 mg / dm ² or less, and the effect of suppressing corrosion was remarkable.

Next, the relationship between the dissolved concentration of besisotriazole in the heat storage medium and the temperature was investigated. The result is shown in Figure 6.
Shown in As shown in the figure, the dissolved concentration of benzotriazole decreases as the temperature of the medium decreases. 30 ° C
The dissolved concentration of benzotriazole is 0.05 wt%. Therefore, it can be seen from FIGS. 5 and 6 that the benzotriazole which has a good corrosion inhibiting effect on the high temperature side (120 ° C.), which is the operating temperature of the heat storage device, and does not cause excessive precipitation of inhibitors even on the low temperature side (30 ° C.). It can be seen that the added concentration is 0.05 wt%.

Further, changes in the concentration of benzotriazole in the heat storage medium were investigated. FIG. 7 shows the result. Temperature is 1
Tested at 20 ° C. As is clear from the figure, the concentration of benzotriazole was 0.025 wt% after 50 hours, which was about half of the initial concentration and then gradually decreased with the passage of time. By the way, it is the concentrator exposed to the concentrated heat storage medium on the high temperature side of the operating temperature of the system that is most corroded in the heat storage device. Since the medium temperature is low except for the concentrator, the degree of corrosion is significantly reduced. Therefore, prevention of corrosion of the condenser on the high temperature side has the highest priority in this type of heat storage device.

Therefore, a container accommodating the inhibitor is installed between the concentrating tank having the lowest medium temperature and the heat exchanger in the heat storage device, and the container is kept at the low temperature side (30 ° C.) of the operating temperature. As a result, a constant concentration of inhibitor is constantly supplied, and the corrosion inhibitory effect at high temperature of the concentrator or the solubility at low temperature is satisfied, and even if the inhibitor in the medium is exhausted and needs to be replenished with the lapse of operating time, it can be continuously supplied. Since corrosion can be prevented for a long time because it can be replenished to the medium, especially when benzotriazole, which is an organic type inhibitor, is used as the inhibitor, it is about 0.
It was found that addition of 05 wt% satisfies both corrosion inhibition effect and solubility.

Based on these points, it was further found that the solubility of the inhibitor in the medium increases by the amount of the inhibitor consumed in the heat storage device, and based on this, the present invention has been achieved. That is, the present invention, in a heat storage device of a closed circulation system having a heat storage medium tank and a heat exchanger, automatically and continuously supplies an amount of an inhibitor necessary to compensate for the decrease in the inhibitor concentration in the heat storage medium. A method for preventing corrosion in a heat storage device in which a heat inhibitor supply device is arranged in a heat storage medium circulation system, and in a closed circulation system heat storage device having a heat storage medium tank and a heat exchanger, in which the consumption amount of the inhibitor is stored by the consumed amount. Disclosed and provided is an anticorrosion method for a heat storage device, which utilizes the increased solubility of inhibitor in a medium to automatically and continuously replenish and thereby maintain a constant inhibitor concentration necessary for anticorrosion. To do.

It is preferable that the inhibitor replenishing device is provided in a part of the circulation system between the heat storage medium tank and the heat exchanger, and the inhibitor replenishing device is provided with a temperature control mechanism, whereby the inhibitor replenishing device is provided. By controlling the temperature of the heat storage device to the low temperature side of the operating temperature, the more purpose is achieved. As another aspect of the present invention, a plurality of inhibitor replenishing devices are provided in parallel in a part of the circulation system between the heat storage medium tank and the heat exchanger, and detection means for detecting corrosion in the concentrator of the heat storage device. Alternatively, the plurality of inhibitor replenishing devices can be selectively used based on the signal from the detection means. As a result, the inhibitor can be supplied for a longer period of time.

In any case, it is practical for the inhibitor replenishing device to have inside it means for preventing the dissolution of insoluble inhibitors and for removing corrosive solids. Is. Further, the anticorrosion method according to the present invention, by using a mixed aqueous solution of calcium chloride and lithium bromide as a heat storage medium, using benzotriazole as an inhibitor, and carrying out the concentration of the inhibitor at about 0.05 wt%, a more effective effect is obtained. be able to.

Further, it is also extremely effective to control the temperature of the supersaturated solution of the inhibitor in the replenishing device so as to replenish the inhibitor in an amount soluble at that temperature as an inhibitor necessary for corrosion prevention. Incidentally, in the present invention, as an example, benzotriazole was added to a mixed aqueous solution of lithium bromide and calcium chloride, but in addition, a concentrated halide aqueous solution effective as a heat storage medium and other inorganic and organic based highly corrosion-inhibiting effects were used. It does not matter if the inhibitor is used in the heat storage device of the present invention.

[0017]

[Operation] Since the present invention has the above configuration,
The consumed amount of the inhibitor in the heat storage device is automatically and continuously supplied over a long period of time.

[0018]

The heat storage device and its anticorrosion method according to the present invention will now be described in more detail with reference to some embodiments.
FIG. 1 is a system diagram of a heat storage device to which the present invention is applied. As shown in the figure, the heat storage device includes a condenser 1, a diluter 2, a medium tank 3,
A water tank 4, pumps 5 and 6 connecting these, and a heat exchanger 7,
It consists of eight. The heat storage device of this embodiment uses water as a refrigerant and concentrated lithium bromide or a mixed aqueous solution of lithium bromide and calcium chloride as a medium. The medium is circulated through the concentrator 1, the heat exchanger 7 and the medium tank 3 by the pump 5. Furthermore, according to the operating temperature of the system, the concentrator 1
Inside, high temperature (120 ℃) and low temperature (30 ℃) due to concentration and dilution
The temperature cycle of is repeated. In this embodiment, an inhibitor replenisher 9 having the shape shown in FIG. 3 or 4 is installed between the medium tank 3 and the heat exchanger 7, and contains benzotriazole as an inhibitor inside.

This heat storage device operates as follows. By constantly maintaining the inhibitor replenisher 9 at the low temperature side (30 ° C.) of the operation cycle by the heat transfer tube 14, the benzotriazole concentration in the machine is constantly maintained at a constant concentration of about 0.05 wt%. This concentration satisfies both the corrosion inhibition effect at high temperature and the solubility at low temperature for the reasons described above. Further, the inhibitor in the medium is consumed with the lapse of operating time, and even if the concentration of the inhibitor decreases and needs to be replenished, the inhibitor in the inhibitor replenisher 9 can be dissolved at 30 ° C. by keeping it in a supersaturated solution. A certain amount of inhibitor will be constantly replenished, and long-term corrosion will be prevented.

FIG. 2 shows another embodiment of the present invention. In this case, two inhibitor replenishers 9, 10 are provided in parallel in the medium flow path between the medium tank 3 and the heat exchanger 7, and the inflow and outflow portions of each inhibitor replenisher are Valves 12 and 13 are provided. Further, inside the concentrator 1, a corrosion sensor 11 such as a pressure sensor or a hydrogen center is provided.

The operation of this device is as follows. Normally, the valves 12 and 13 of one of the inhibitor replenishers 10 are closed, and the medium is passed through the inhibitor replenisher 9 located in the regular flow path to constantly replenish the inhibitor as in the case of the first embodiment. are doing. When the inhibitor in the inhibitor replenisher 9 is consumed and the pressure sensor or the hydrogen sensor installed in the concentrator 1 detects the pressure change or the generated hydrogen amount in the container caused by the corrosion, manually or by an appropriate automatic means. Thus, the valve of the inhibitor replenisher 9 is closed and the valves 12 and 13 of the other flow path are opened to circulate the medium through the inhibitor replenisher 10. That is, in this embodiment, by providing a plurality of inhibitor replenishing devices in the circulation path, it is possible to replenish the inhibitor continuously and for a long time without suspending the operation of the heat storage device.

Next, the structure of the inhibitor replenisher used in the present invention will be described. FIG. 3 shows a filling type inhibitor replenisher which is one of the inhibitor replenishers. This inhibitor replenisher 9 has a heat transfer tube 14 inside and controls the temperature by heating / cooling the inhibitor supersaturated solution 15, and replenishes only the amount of the inhibitor that can be melted at that temperature into the heat storage medium circulation system passage. It is supposed to do. In addition, the mesh reticulate body 16 is provided in the inhibitor replenisher so as not to generate a differential pressure so that the undissolved inhibitor is not mixed into the system passage.

FIG. 4 shows an impregnated laminated inhibitor replenisher which is another example of the inhibitor replenisher. This inhibitor replenisher 9'has a heat transfer tube 14 inside,
There are impregnated materials 17, 17 such as multiple layers of sponge,
The inhibitor supersaturated solution 15 is impregnated in the impregnating materials 17, 17. The heat storage medium passes through the stack. Even in this case, similarly to the filling type, the temperature of the inhibitor supersaturated solution is controlled by the heat transfer tube 14 to control the concentration of the inhibitor to be replenished.

In both the filling type and the impregnated laminated type inhibitor replenisher, the mesh or the impregnating material has the effect of removing corrosive solid substances at the same time. The anticorrosion property can be improved. The amount of inhibitor supply required by a normal heat storage device is extremely smaller than the inhibitor capacity in the inhibitor replenisher, and periodic replenishment is sufficient once every two years. For example, when the amount of heat storage medium is 1 kl and benzotriazole (BTA) is used as an inhibitor, the amount that can be dissolved at 30 ° C is 0.5 g, and 200 h
After that, the consumption of the inhibitor is about 1/2, so the annual usage is 0.5x2x (8800 / 200h) = 44 g, and about benzotriazole is stored in the inhibitor supply device.
It can be seen that there is no need to replenish for 2 years if 100g is supersaturated.

[0025]

EFFECTS OF THE INVENTION According to the present invention, various disadvantages such as the frequent analysis of a heat storage medium and the complexity of replenishing an inhibitor and the deterioration of heat storage performance can be solved, and it is inexpensive, simple, automatic and continuous. In addition, since a certain amount of inhibitor necessary for suppressing corrosion can be replenished, the performance of the heat storage device can be stably maintained without any corrosion trouble, and the reliability of the maintenance-free heat storage device can be remarkably improved.

[Brief description of drawings]

FIG. 1 is a system diagram of a heat storage device showing an embodiment of the present invention.

FIG. 2 is a system diagram of a heat storage device showing another embodiment of the present invention.

FIG. 3 is a schematic sectional view of an inhibitor supply device according to the present invention.

FIG. 4 is a schematic sectional view of another inhibitor supply device according to the present invention.

FIG. 5 is a diagram showing the relationship between the benzotriazole concentration and the amount of corrosion.

FIG. 6 is a graph showing the relationship between temperature and benzotriazole dissolved concentration.

FIG. 7 is a graph showing the relationship between time and benzotriazole concentration. 1 ... Concentrator, 2 ... Diluter, 3 ... Medium tank, 4 ... Water tank, 5, 6 ... Pump, 7, 8 ... Heat exchanger, 9, 10 ...
..Inhibitor replenisher, 11 ... Corrosion detector, 12,13 ..
Valve, 14 ... Heat transfer tube

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yasuo Ozeki 4026 Kujimachi, Hitachi City, Ibaraki Hitachi, Ltd., Hitachi Research Laboratory (72) Inventor Akihiro Tani 603, Kintatemachi, Tsuchiura City, Ibaraki Hitachi, Ltd. Tsuchiura Plant (56) Reference JP-A-4-28889 (JP, A) JP-A-56-110888 (JP, A)

Claims (6)

(57) [Claims] 1. In a heat storage device of a closed circulation system having a heat storage medium tank and a heat exchanger, an inhibitor capable of automatically and continuously supplying an amount of an inhibitor necessary to compensate for a decrease in the inhibitor concentration in the heat storage medium. A replenishing device is installed in a part of the circulation system between the heat storage medium tank and the heat exchanger in the heat storage medium circulation system, and the inhibitor replenishing device includes a temperature control mechanism, and the inhibitor replenishing device is provided by the temperature control mechanism. Is controlled to a low temperature side of the operating temperature of the heat storage device. 2. A plurality of inhibitor replenishing devices are provided in parallel in a part of the circulation system between the heat storage medium tank and the heat exchanger,
Furthermore, a detecting means for detecting corrosion is provided in the concentrator of the heat storage device, and based on the signal of the detecting means,
The heat storage device according to claim 1, wherein the heat storage device is configured so that the plurality of inhibitor supply devices can be selectively used. 3. The inhibitor replenishing device has a means for preventing the insoluble inhibitor from being eluted and for removing corrosive solid matter, inside thereof. The heat storage device according to 2. 4. A heat storage medium tank and a heat exchanger, wherein the inhibitor replenishing device is installed in a part of a circulation system between the heat storage medium tank and the heat exchanger, and the inhibitor replenishing device is provided with a temperature control mechanism. A method for preventing corrosion in a heat storage device of a closed circulation system, wherein the inhibitor replenishing device is controlled to a low temperature of an operating temperature of a heat storage device by the temperature control mechanism, wherein an amount of consumption of the inhibitor is the amount of consumption of the inhibitor to the heat storage medium. The method for preventing corrosion of a heat storage device is characterized in that it is possible to maintain the constant inhibitor concentration necessary for corrosion protection by automatically and continuously replenishing it by utilizing the increase in the solubility of. 5. The anticorrosion method for a heat storage device according to claim 4, wherein the heat storage medium is a mixed aqueous solution of calcium chloride and lithium bromide, the inhibitor is benzotriazole, and the inhibitor concentration is 0.05 wt%. . 6. The heat storage device according to claim 4, wherein the supersaturated solution of the inhibitor in the replenishing device is temperature-controlled, and an amount of the inhibitor soluble at that temperature is replenished as an inhibitor necessary for corrosion prevention. Anticorrosion method.