WO2019044094A1

WO2019044094A1 - Working medium for absorption refrigerator and absorption refrigerator using same

Info

Publication number: WO2019044094A1
Application number: PCT/JP2018/021412
Authority: WO
Inventors: 勝美馬渕; 聡小田島; 藤居　達郎; 久幸折田; 武田　伸之; 英彦野田; 高橋　晋
Original assignee: 株式会社日立製作所
Priority date: 2017-09-04
Filing date: 2018-06-04
Publication date: 2019-03-07
Also published as: JP7201161B2; JP2019045079A

Abstract

Provided is a working medium for an absorption refrigerator that enables corrosion of a structural member to be greatly suppressed; also provided is an absorption refrigerator using this working medium. The working medium for an absorption refrigerator includes a propanol aqueous solution as a refrigerant and a corrosion inhibitor. The corrosion inhibitor includes one or more of an alkali metal salt, an alkaline earth metal salt, and an oxyacid salt. The alkali metal salt is a hydroxide of an alkali metal, and the alkaline earth metal salt is a hydroxide of an alkaline earth metal.

Description

Working medium for absorption refrigerator and absorption refrigerator using the same

The present invention relates to a working medium for absorption refrigerator and an absorption refrigerator using the same.

The working medium generally used in the conventional absorption refrigerator is a lithium bromide-water system, the refrigerant is water, and the absorbing liquid is lithium bromide. Therefore, since the refrigerant is water, the water which is the refrigerant freezes in the evaporator in the evaporator producing cold heat, and in the absorption refrigerator of the normal specification, the heat medium of the temperature below the freezing point is manufactured It is difficult.

Patent Document 1 discloses a method using a lower alcohol such as methanol, ethanol, propanol or the like, or a mixed solution of the alcohol and water as a refrigerant for generating a temperature below the ice temperature with an absorption refrigerator. .

Patent Document 2 discloses a composition containing an alkali metal hydroxide and an organic acid such as an organic phosphonic acid or a phosphonocarboxylic acid as a corrosion inhibitor of a circulating cooling water system.

Patent No. 2512095 JP 2005-290424 A

Water or lower alcohols alone such as propanol are not as corrosive to structural materials, for example, SS400, but when water is added to form an aqueous solution, the corrosiveness, particularly in the gas phase, is significantly increased. This increase in corrosion is caused by iron ions eluted in water and iron oxides generated by corrosion acting as a catalyst to accelerate corrosion and oxidize alcohol to acidify (in the case of primary alcohol) or aldehyde (secondary alcohol) Is considered to be the case). Therefore, in the case of using a propanol-water mixed refrigerant as the refrigerant to configure the absorption refrigerator, it is essential to establish a technique for preventing corrosion by the mixed refrigerant.

In patent document 1, there is no description regarding a corrosion inhibitor. Patent Document 2 does not describe a refrigerant system containing a lower alcohol.

Therefore, an object of the present invention is to provide a working medium for absorption-type refrigerator capable of highly suppressing the corrosion of a structural material and an absorption-type refrigerator using the same.

In order to achieve the above object, a working medium for an absorption refrigerator according to an aspect of the present invention includes a propanol aqueous solution as a refrigerant and a corrosion inhibitor.

ADVANTAGE OF THE INVENTION According to this invention, the working medium for absorption-type refrigerators which can highly suppress corrosion of a structural material, and the absorption-type refrigerator using the same can be provided.

1 shows a cycle diagram of an absorption refrigerator. The cycle systematic diagram of an absorption-type refrigerator is shown. It is a graph which shows the temperature dependence of the saturation vapor pressure in various organic solvents. It is a graph which shows the temperature dependence of the vapor pressure of 1-propanol aqueous solution and water. It is a graph which shows the concentration dependence of the freezing point of 1-propanol, 2-propanol, 1-butanol, and 2-butanol. It is a graph which shows the LiOH concentration dependence of the freezing point at the time of adding LiOH of each concentration as a corrosion inhibitor to 1-propanol aqueous solution. It is a graph showing the _Li 2 MoO ₄ concentration dependence of the freezing point of the case of adding _Li 2 MoO ₄ of each concentration as a corrosion inhibitor in 1-propanol solution. It is a graph which shows the LiOH concentration dependence of the amount of gas generated by the corrosion test in the water 1-propanol mixed refrigerant which added LiOH. Is a graph showing the _Li 2 MoO ₄ concentration dependence of the generated gas amount of the corrosion test in Li ₂ MoO ₄ water-1-propanol mixed refrigerant was added.

The present invention relates to a working medium for an absorption refrigerator that generates cold energy below the freezing point (ice temperature) of water and an absorption refrigerator using the same, and particularly when a water-alcohol aqueous solution is used as the refrigerant. By adding an alkali metal salt (hydroxide of alkali metal), an alkaline earth metal salt (hydroxide of alkaline earth metal) or an oxy acid salt as a corrosion inhibitor to a lower solidification temperature than the aqueous alcohol solution Further, the present invention relates to a working medium for an absorption type refrigerator excellent in corrosion resistance which highly suppresses corrosion of main components of the refrigerator, and an absorption type refrigerator using the same.

When an aqueous salt solution such as LiBr-water used in a conventional low-temperature absorption refrigerator is used as the mixed refrigerant, as shown in FIG. 1A, only the water component in the refrigerant is evaporated and absorbed in the evaporator. Absorbed into the aqueous LiBr solution. The condensate is water, and the salt concentration in the refrigerant is determined by the balance between the amount of refrigerant evaporation (amount of water vapor) in the evaporator and the amount of liquid returned from the condenser (amount of water).

Therefore, it is essential to monitor and control the solution circulation volume in real time. When the amount of water returning from the condenser is large relative to the amount of evaporation of water in the evaporator, the concentration of salt in the mixed refrigerant decreases, and the freezing point of the mixed refrigerant rises, which may cause freezing. Conversely, when the amount of water returning from the condenser is small relative to the amount of evaporation of water, the concentration of salt in the mixed refrigerant increases and the freezing point of the refrigerant drops, but if this tendency progresses too much, the concentration above the salt solubility As a result, the mixed refrigerant may be crystallized.

However, as shown in FIG. 1 (b), there is a concern in the case of using a salt by using, as the refrigerant, one having the property of evaporating both, such as an alcohol aqueous solution in which alcohol and water are mixed in the refrigerant. It is possible to avoid the risk of refrigerant concentration fluctuation during operation of the refrigerator. Table 1 shows a list of physical properties of alcohol as a candidate.

If the alcohol has 3 or less carbon atoms, it completely dissolves in water. Further, the solidification point of the lower alcohol is about -100 ° C. or less, and even when it is mixed with water to form an aqueous solution, it can be expected that the solidification point will be 0 ° C. or less. In addition, lower alcohols are also highly safe except methanol. However, if the vapor pressure of the alcohol used is higher than the vapor pressure of water and the boiling point is lower than the boiling point of water, the concentration of alcohol will increase on the vapor side. Conversely, if the vapor pressure of alcohol is lower than the vapor pressure of water and the boiling point is higher than the boiling point of water, the concentration of alcohol will be lower on the vapor side. From this, in order to keep the balance with water constant at all times and to stabilize the alcohol concentration of the mixed refrigerant and its vapor, it is necessary that the vapor pressures of water and the corresponding alcohol be close.

In addition, even when the concentration balance of alcohol is broken, if it is dissolved in water in the entire concentration range, problems such as solution separation can be avoided. From this point, it can be said that 1-propanol is most suitable as the refrigerant. Although 2-propanol has a vapor pressure slightly different from that of water (FIG. 3), it can be used as a mixed refrigerant because it dissolves with water in the entire concentration range. Therefore, the main component is preferably 1-propanol or 2-propanol for these reasons, but not only single-use but also alcohols other than propanol, such as ethanol having 2 or less carbon atoms, methanol, and vice versa Four or more alcohols such as butanol, haxanol and octanol may be mixed. Of course, those isomers may be added as well. However, their concentration needs to be lower than the concentration of propanol which is the main component.

However, in the propanol-water mixed refrigerant system, as described above, the corrosiveness is significantly increased in the gas phase. It is unclear whether the conventional corrosion inhibitors show the same effect on propanol-water mixed refrigerant in order to suppress the increase.

In addition, the corrosion inhibitor conventionally used in cooling water is roughly divided based on the mechanism, and is classified into the following types.

(1) Chemical adsorption in adsorption inhibitors:
[M] + RX: → [M]: XR
(2) Formation of hydroxide precipitate in oxidized inhibitors:
^{^{M n + + n: OH -}} → [M n + (: OH -) n]
(3) Formation of complex precipitates in precipitation inhibitors:
^{^{M n + + nRX -: →}} [M n + (: XR -) n]
Here, a [M] and ^{M n +} is a Lewis ^{acid, RX:,: OH -,} RX -: such is the Lewis base.

Therefore, as a result of intensive research, in the propanol-water mixed refrigerant system, alkali metal salts (alkali metal hydroxides), alkaline earth metal salts (water, etc.) are used as substances that inhibit the corrosion of iron-based materials such as SS400. By forming an absorption refrigerator which can exhibit a sufficient corrosion inhibiting effect by adding an alkaline earth metal oxide or an oxy acid salt and which generates a subfreezing heat using a propanol-water mixed refrigerant Is possible. It is also effective to use an alkali metal hydroxide or an alkaline earth metal hydroxide in combination with an oxy acid salt.

As a hydroxide of an alkali metal which is an example of an alkali metal salt, any of LiOH, NaOH, KOH, RbOH and CsOH exhibits a corrosion inhibitory effect. Among them, LiOH, NaOH and KOH are preferable from the viewpoint of solubility and corrosion inhibition effect. In particular, since LiBr is used as the absorbing solution, it is particularly preferable to use a hydroxide of Li which is the same alkali metal. A 0.1 M addition of an alkali metal hydroxide provides the anticorrosion effect, but a 0.02 M thinner than that can provide a sufficient corrosion inhibition effect. Even if 0.1 M or more is added, the effect is obtained but it becomes expensive. Further, when it is 0.005 M or less, the action of suppressing the hydroxide corrosion of the alkali metal becomes small, and there is a possibility that the action of suppressing the corrosion may be lost due to exhaustion. From these, the optimum concentration range is 0.02 to 0.15 M.

Further, hydroxides of alkali metal earth metals which are an example of the alkali earth metal salts include Be (OH) ₂ , Mg (OH) ₂ , Ca (OH) ₂ , Sr (OH) ₂ , and Ba (OH) There is OH) ₂ and both show corrosion inhibitory effect. Among them, Ca (OH) ₂ is preferable from the viewpoint of solubility and corrosion inhibitory effect. Alkaline earth metal hydroxides, when added at a concentration of 0.1 M, provide anticorrosion effects, but even thinner than 0.02 M can provide sufficient corrosion control effects. Even if 0.1 M or more is added, the effect is obtained but it becomes expensive. In addition, when it is 0.005 M or less, the corrosion inhibiting action of the hydroxide of the alkaline earth metal becomes small, and there is a possibility that the corrosion inhibiting action may be lost due to exhaustion. From these, the optimum concentration range is 0.02 to 0.15 M. Saturated solutions may be used because Ca (OH) ₂ has low solubility (approximately 0.02 M at 25 ° C.).

As an oxy acid salt, molybdate, tungstate, vanadate, silicate, phosphate, polyphosphate, phosphonate, hypochlorite, chlorite, perchlorate, There are sulfonates and the like. Specifically, lithium molybdate, sodium molybdate, ammonium molybdate, sodium tungstate, ammonium vanadate, sodium orthovanadate, sodium silicate, sodium metasilicate, sodium phosphonate, sodium dihydrogen phosphate, phosphoric acid Ammonium dihydrogen, sodium hydrogen pyrophosphate, sodium metaphosphate, sodium polyphosphate, sodium hypochlorite, sodium chlorite, sodium perchlorate, etc., but if it is the above-mentioned oxy acid salt, there is no particular limitation and corrosion It exhibits a suppressive action.

The oxyacid salt can provide anticorrosion when it is added at a concentration of 0.01M. Even at a smaller thickness of 0.002 M, a sufficient corrosion inhibiting effect can be obtained, but the corrosion inhibiting effect decreases with the decrease in concentration. In addition, when it is 0.002 M or less, the corrosion inhibiting action is reduced, and there is a possibility that the corrosion inhibiting action may be lost due to exhaustion. From these facts, the optimum concentration range is 0.002 to 0.01M. Although the corrosion can be suppressed by adding these alkali metal hydroxides and oxalates, the other effect is that the freezing point is lowered by the addition. The freezing point decreases with increasing concentration of these substances.

Copper (copper alloy) is generally used for heat transfer tubes in absorption type refrigerators. Therefore, a copper corrosion inhibitor may be added together with the above-mentioned corrosion inhibitor in consideration of corrosion prevention of copper. The dissolution inhibitor for copper consists of a compound that forms an insoluble compound with copper and a surfactant. Examples of compounds which form insoluble complexes with copper include triazoles such as benzotriazole, triazol derivatives, quinaldinates, compounds having a heterocyclic ring such as oxine, benzoin oxime, anthranilic acid, salicylaldoxime, nitrosonaphthol, cuperone , Haloacetic acid, and cysteine. The content of these is preferably 0.005 to 0.2 M, and most preferably 0.02 to 0.1 M or so.

Next, the configuration of the absorption refrigerator 10 will be described.

FIG. 2 shows a cycle diagram of the absorption refrigerator 10. As shown in FIG.

The absorption refrigerator 10 includes an evaporator 1, an absorber 2, a high temperature regenerator 3, a low temperature regenerator 4, a condenser 5, a heat exchanger 6, and a drain cooler 7. Among them, the inside of the evaporator 1, the absorber 2 and the condenser 5 is maintained at a vacuum of about several mmHg.

A mixed refrigerant of water-1-propanol (hereinafter, also simply referred to as "mixed refrigerant") is used as a refrigerant in the evaporator 1, and the molar fraction of water is 0.85 at the time of sealing. To this refrigerant, 0.3% LiOH is added as a corrosion inhibitor in order to alleviate the high corrosiveness of the water-1-propanol mixed refrigerant. As the absorption liquid of the absorber 2, a concentrated LiBr solution having a very small water vapor pressure is used. The high temperature regenerator 3 and the low temperature regenerator 4 are also collectively referred to as a "regenerator".

At a lower part of the evaporator 1, a pump 8 for dispersing the mixed refrigerant staying at the bottom of the evaporator 1 from the upper part of the evaporator 1 is installed. In addition, a pump 9 for dispersing the absorbent remaining in the bottom of the absorber 2 from the top of the absorber 2 is installed at the lower part of the absorber 2.

At the time of supply of the low temperature medium, the water 1-propanol mixed refrigerant generated in the condenser 5 from the top of the evaporator 1 and the water 1-propanol mixed refrigerant staying at the bottom in the evaporator 1 are dispersed to The mixed refrigerant is vacuum evaporated on the outer surface of the cooling pipe installed in The refrigerant in the cooling pipe is cooled by the heat of vaporization to obtain a low temperature medium of -10.degree.

However, when the vacuum evaporation is continued, the degree of vacuum is lowered by the mixed refrigerant vapor generated and the cooling efficiency is lowered. Therefore, in order to continue vacuum evaporation efficiently, it is necessary to remove the mixed refrigerant vapor generated in the evaporator 1 and maintain a vacuum. For this reason, the mixed refrigerant vapor generated in the evaporator 1 is absorbed by the absorber 2 in the concentrated LiBr solution. The absorbent (diluted solution) diluted by the absorption of the mixed refrigerant vapor is heated by the heat exchanger 6 and then sent to the high temperature regenerator 3 and the low temperature regenerator 4.

In the high temperature regenerator 3, the absorbing liquid is heated and concentrated by steam or the like supplied from the outside as a heat source. The mixed refrigerant vapor generated thereby is condensed by heating the low temperature regenerator 4 to become a mixed refrigerant, and is dispersed in the condenser 5. The steam or the like of the heat source which has passed through the high temperature regenerator 3 becomes condensed water, is used for heating the dilute solution by the drain cooler 7, is further cooled, and is discharged as a drain.

The mixed refrigerant vapor generated by heating the absorbing liquid in the low temperature regenerator 4 is condensed by cooling water in the condenser 5 and then sent to the evaporator 1. The warmed cooling water is cooled by heat radiation to the atmosphere by a cooling tower or the like.

It is known that the relationship between the vapor pressure of each organic solvent and the temperature can be well approximated by an empirical equation called Antoine equation of equation (1). In Formula (1), A, B, and C indicate ant-one constants determined by the substance, T indicates an absolute temperature, and p indicates a saturation vapor pressure [Pa].
(1)
logp = A- (B / (T + C)) (1)
The Antoine constant of each organic solvent used in Table 2 is shown (see, for example, Maruzen "Chemical Engineering Handbook" edited by the Chemical Engineering Society, Rev. 6 edition (1999)).

FIG. 3 is a graph showing the calculated temperature dependence of saturated vapor pressure in various organic solvents. 1-Propanol and 2-Butanol exhibit similar vapor pressure characteristics to water in the operating temperature range of the absorption refrigerator. However, since the actual refrigerant is not an alcohol alone but an aqueous solution, the results in FIG. 3 can be used as reference for selecting an organic solvent as a refrigerant, but the vapor pressure as an alcohol aqueous solution is actually measured at each aqueous solution concentration There is a need.

FIG. 4 is a graph showing the temperature dependence of the vapor pressure of 1-propanol aqueous solution (water molar fraction: X) and water. The water molar fraction X is a value represented by X1 / (X1 + X2), where X1 is the molar concentration of water and X2 is the molar concentration of 1-propanol. Since the vapor pressures of 1-propanol aqueous solution (water molar fraction: X) and water are close to each other, it can be understood that 1-propanol aqueous solution has excellent characteristics as a refrigerant from the viewpoint of stability of alcohol concentration of mixed refrigerant .

Table 3 shows the alcohol concentration in the condenser 5 when the concentration and type of the alcohol in the mixed refrigerant sealed in the absorption refrigerator 10 shown in FIG. 2 after initial and after 1000 hours of operation (cycle) are changed There is.

When methanol aqueous solution or ethanol aqueous solution is used as a mixed refrigerant, the vapor pressure of those substances is higher than that of water as shown in FIG. 3, and therefore the alcohol component in evaporator 1, high temperature regenerator 3 and low temperature regenerator 4 Is mainly evaporated. Further, since the alcohol component is mainly evaporated in the high temperature regenerator 3 and the low temperature regenerator 4, the alcohol concentration of the condensate in the condenser 5 becomes high. Therefore, when the cycle is assembled, if the balance of the evaporation amount in the evaporator 1 and the condensation amount in the condenser 5 is broken, not only the balance of the liquid amount but also the alcohol concentration balance of the whole system is broken. Cycle operation can not be continued.

On the other hand, 1-propanol and 2-butanol, as shown in Table 1 and Fig. 3, have a boiling point and vapor pressure close to that of water, so the alcohol concentration balance is almost the same as in the initial state of encapsulation even after 1000 hours of operation It is. Even if the balance of the liquid volume is broken, the alcohol concentration balance is maintained. In such a case, stable operation is possible.

FIG. 5 is a graph showing concentration dependence of freezing points of 1-propanol, 2-propanol, 1-butanol and 2-butanol. 1-Butanol and 2-butanol slightly lower their freezing point as their concentration increases, but they do not decrease when the water mole fraction is 0.9 or less. This is because butanol does not dissolve in water, and it is difficult to obtain the target temperature of -5 ° C or less. In contrast, when 1-propanol and 2-propanol are used, the freezing point decreases with increasing concentration. Propanol dissolves completely with water. In order to achieve the target of -5.degree. C., it can be achieved by setting the concentration to 0.95 or less in water mole fraction. Thereby, the working refrigerant below freezing point can be provided. In order to completely dissolve it with water, problems such as solution separation can be avoided even if the concentration balance of alcohol is broken.

FIG. 6 is a graph showing the LiOH concentration dependency of the freezing point when LiOH of each concentration is added as a corrosion inhibitor to a 1-propanol aqueous solution. The addition of LiOH lowers the freezing point, and the degree increases with the increase of LiOH concentration. For example, when it is desired to obtain a low temperature of -15.degree. C., the propanol concentration must be a water molar fraction as high as 0.6 or less without adding LiOH. On the other hand, when 0.7 wt% of LiOH is added, the propanol concentration may be about 0.85 in water mole fraction, and the target temperature can be achieved with low concentration of 1-propanol.

FIG. 7 is a graph showing the Li ₂ MoO ₄ concentration dependency of the freezing point when Li ₂ MoO ₄ of each concentration is added as a corrosion inhibitor to 1-propanol aqueous solution. The addition of Li ₂ MoO ₄ lowers the freezing point, and the degree increases with the increase of the Li ₂ MoO ₄ concentration. However, the degree is not as low as that of LiOH, and it is overshot at about 0.3 wt%, and the freezing point is not lowered by more than that.

In order to confirm the effect of the present invention, a corrosion test of the structural member SS400 was carried out in a solution in which various alkalis were added to the mixed refrigerant, and the amount of gas generated by the corrosion was measured. The anodic reaction of corrosion is a dissolution reaction of iron shown in the following reaction formula (1). The cathode reaction paired with that is a hydrogen gas generation reaction shown by the following reaction formula (2) because it is under degassing conditions. As described above, since the amount of generated hydrogen gas is in proportion to the amount of corrosion, the magnitude of the corrosion can be determined from the amount of generated hydrogen gas.
^{^{Fe → Fe 2+ + 2e - ···}} (1)
^{^{_{2H + + 2e - → H 2}}} ··· (2)

The corrosion test and the measurement of the gas generation amount were performed as follows. For the corrosion test, a sealed tube (glass ampoule) made of Pyrex (registered trademark) glass was used. Connect a bottomed glass tube containing a test piece (length 10 x width 4 x thickness 0.5 mm, SS400) and 20 ml of mixed refrigerant as a test solution to a vacuum pump and apply ultrasonic waves to the tube under a reduced pressure of 2 mmHg at 298 K After degassing for 15 minutes while applying vibration, the mouth of the tube was sealed to produce a sealed tube. The sealed tube was held in a thermostat kept at 90 ° C. for 500 hours.

After the corrosion test, the glass ampoule was placed in a glass ampoule grinding container connected to a mercury manometer, and the pressure in the grinding container was reduced to 2 mmHg or less. After crushing the glass ampoule, the amount of gas generation was determined from the change of the value of the mercury maometer. As a test piece, all the examples described below used SS400. In this specification, SS400 is used as a representative example of carbon steel, but the steel used as a structural material of the absorption refrigerator is not limited to this, and other carbon steels and various low alloy steels Also, stainless steel etc. can be used. In addition, water-1-propanol was used as a mixed refrigerant. Even when water 2-propanol is used as the mixed refrigerant, the corrosion can be suppressed substantially in the same manner as the test results described below. Also, although hydroxides of alkali metals and alkaline earth metals are used as an example of alkali metal salts and alkaline earth metal salts, the same corrosion is possible even if other alkali metal salts and alkaline earth metal salts are used. Can be suppressed.

Table 4 shows the amount of gas (hydrogen) generated in the corrosion test in the mixed refrigerant to which various alkalis are added. Here, the molar fraction of water in the mixed refrigerant is 0.85.

The following can be understood from this table.

Comparative Example 1 is the result of examining the amount of gas generated by the corrosion test in the mixed refrigerant to which the corrosion inhibitor is not added. The amount of gas generation is 150 ml / dm ² .

As shown in Example 1, the amount of gas generation when 0.3 wt% of LiOH is added as a corrosion inhibitor is 0.48 ml / dm ² , and the amount of gas generation is about 1 as compared with Comparative Example 1. It is reduced to / 300, and the corrosion is significantly suppressed. As shown in FIG. 6, the freezing point can be lowered by 3 ° C. by adding a corrosion inhibitor.

Example 2 shows the case where the LiOH concentration is reduced to 0.048 wt%. Even if the concentration is reduced, the gas generation amount is 0.25 ml / dm ² , and even if the concentration is reduced, the corrosion amount can be maintained at a low level.

Examples 3 and 4 show the case where the type of cation is changed from Li to Ca and Na. Even if the type of cation is changed, the amount of gas generation is 0.29 and 0.157 ml / dm ² , and even if the concentration is reduced, the amount of corrosion can be kept low. Even if the cation is changed, the freezing point is lowered by the addition of the corrosion inhibitor as in FIG. Comparative Examples 2 and 3 show the case where NH ₃ is added to the mixed refrigerant. The concentrations were 1.0 M and 0.1 M. In all cases, the amount of gas generation is 120 ml / dm ² and 110 ml / dm ² , and the level is the same as in the case of no addition shown in Comparative Example 1, so that corrosion is not suppressed. The pH of these solutions is about 11, which is the same as in the case of Examples 1-4. It is thought that corrosion is not suppressed from this because it is alkali. Comparative Example 4 is the case where Na ₂ CO ₃ was added. The pH is the same as in Examples 1 to 4 (pH 11.5), but the gas generation amount is 90 ml / dm ² and the corrosion is not suppressed as in the case of NH ₃ .

Table 5 shows the amount of gas (hydrogen) generated in the corrosion test in the mixed refrigerant to which various alkalis are added. Here, the molar fraction of water in the mixed refrigerant is 0.95.

The following can be understood from this table.

The comparative example 5 is the result of having examined the gas quantity generate | occur | produced by the corrosion test in the mixed refrigerant which has not added the corrosion inhibitor. The amount of gas generation is 90 ml / dm ² .

Examples 5 and 6 are cases where LiOH was added as a corrosion inhibitor. As in the case where the water mole fraction shown in Table 4 is 0.85, by adding the hydroxide of an alkali metal, the gas generation amount is extremely reduced and the corrosion is suppressed.

Example 7 is the case where Ca (OH) ₂ is added as a corrosion inhibitor. As in the case where the water mole fraction shown in Table 4 is 0.85, the amount of gas generation is extremely reduced and corrosion is suppressed.

Example 8 is the case where NaOH is added as a corrosion inhibitor. As in the case where the water mole fraction shown in Table 4 is 0.85, the amount of gas generation is extremely reduced and corrosion is suppressed.

On the other hand, when using NH ₃ shown in Comparative Examples 6 and 7 and Na ₂ CO ₃ shown in Comparative Example 8 even with the same degree of alkali, the corrosion inhibiting action is carried out as in the case of the water mole fraction of 0.85. Not shown.

From this, it is considered that corrosion is not suppressed because it is alkali.

Table 6 shows the amount of gas (hydrogen) generated in the corrosion test in the mixed refrigerant to which various alkalis are added. Here, the molar fraction of water in the mixed refrigerant is 0.85. Note that Comparative Example 1 is also shown in the table.

The following can be understood from this table.

Example 9 is the case where Li ₂ MoO ₄ is added as a corrosion inhibitor. Compared with the case where the corrosion inhibitor shown in Comparative Example 1 is not contained, the gas generation amount is extremely reduced and the corrosion is suppressed.

Example 10 is the case where sodium orthovanadate (Na ₃ VO ₄ ) is added as a corrosion inhibitor. Compared with the case where the corrosion inhibitor shown in Comparative Example 1 is not contained, the gas generation amount is extremely reduced and the corrosion is suppressed.

Example 11 is the case where sodium metasilicate (Na ₂ SiO ₃ ) is added as a corrosion inhibitor. Compared with the case where the corrosion inhibitor shown in Comparative Example 1 is not contained, the gas generation amount is extremely reduced and the corrosion is suppressed.

Example 12 is the case where sodium phosphonate (HNa ₂ O ₃ P (disodium hydrogen phosphite)) is added as a corrosion inhibitor. Compared with the case where the corrosion inhibitor shown in Comparative Example 1 is not contained, the gas generation amount is extremely reduced and the corrosion is suppressed.

Example 13 is the case where sodium benzenesulfonate (C ₆ H ₅ NaO ₃ S) is added as a corrosion inhibitor. Compared with the case where the corrosion inhibitor shown in Comparative Example 1 is not contained, the gas generation amount is extremely reduced and the corrosion is suppressed.

Example 14 is the case where sodium perchlorate (NaClO ₄ ) is added as a corrosion inhibitor. It shows in Comparative Example 1. Compared with the case where the corrosion inhibitor is not contained, the gas generation amount is extremely reduced and the corrosion is suppressed.

The corrosion inhibitors of Examples 9-14 are collectively referred to herein as "oxygen acid salts." As shown in these examples, the addition of various low concentrations of oxyacid salts shows a remarkable corrosion inhibiting action as in the case of adding an alkali, even if the pH hardly changes.

Table 7 shows the amount of gas (hydrogen) generated in the corrosion test by adding various adsorption type corrosion inhibitors used in general cooling water to a water-1-propanol mixed refrigerant as a test solution. There is. The mole fraction of water in the mixed refrigerant is 0.85. The test temperature is 90 ° C. Note that Comparative Example 1 is also shown in the table.

The following can be understood from this table.

Comparative Example 9 is the case where hexamethylenetetramine used as a corrosion inhibitor in cooling water is added. Even when hexamethylenetetramine, which has a corrosion inhibiting effect in cooling water, is added, it does not exhibit a corrosion inhibiting effect in a water-1-propanol mixed refrigerant.

Comparative Example 10 is the case where thiourea used as a corrosion inhibitor in cooling water is added. Even if thiourea having a corrosion inhibiting effect is added to the cooling water, it does not exhibit the corrosion inhibiting effect in the water-1-propanol mixed refrigerant.

Comparative Example 11 is the case of sorbitan monooleate used as a corrosion inhibitor in cooling water. Even if sorbitan monooleate, which has a corrosion inhibiting effect in cooling water, is added, it does not exhibit a corrosion inhibiting effect in a water-1-propanol mixed refrigerant.

Comparative Example 12 is the case where aminotrimethylene phosphonic acid used as a corrosion inhibitor in cooling water is added. Even when aminotrimethylene phosphonic acid having a corrosion inhibiting action is added in cooling water, it does not exhibit a corrosion inhibiting action in a water-1-propanol mixed refrigerant.

Table 8 shows the amount of gas (hydrogen) generated in the corrosion test by adding various oxidation type corrosion inhibitors used in general cooling water to a water-1-propanol mixed refrigerant to make a test solution. There is. The molar fraction of water in the mixed refrigerant was 0.85. The test temperature is 90 ° C.

The following can be understood from this table.

Comparative Example 13 is the case where hydrogen peroxide, which is an oxidizing agent, is added. Even if hydrogen peroxide is added, it does not show a corrosion inhibitory effect in the water-1-propanol mixed refrigerant.

The comparative example 14 is a case where nitrate ion (potassium nitrate) is added. The addition of nitrate ion, which is used as a corrosion inhibitor in cooling water, does not exhibit a corrosion inhibiting action in a water-1-propanol mixed refrigerant.

Comparative Example 15 is the case where nitrite ion (sodium nitrite) is added. The addition of nitrate ion, which is used as a corrosion inhibitor in cooling water, does not exhibit a corrosion inhibiting action in a water-1-propanol mixed refrigerant.

Comparative Example 16 is the case where nitrate ion (cerium ammonium nitrate) is added. The addition of nitrate ion, which is used as a corrosion inhibitor in cooling water, does not exhibit a corrosion inhibiting action in a water-1-propanol mixed refrigerant.

Table 9 shows the amount of gas (hydrogen) generated in the corrosion test by adding various precipitation-type corrosion inhibitors used in general cooling water to a water-1-propanol mixed refrigerant as a test solution. There is. The molar fraction of water in the mixed refrigerant was 0.85. The test temperature is 90 ° C. Note that Comparative Example 1 is also described in this table.

The following can be understood from this table.

Comparative Example 17 is the case where cerium nitrate is added. Even if cerium nitrate is added to the cooling water, it does not show a corrosion suppressing action in the water-1-propanol mixed refrigerant.

Comparative Example 18 is the case where 8-quinolinol is added. Even if 8-quinolinol is added to cooling water, it does not exhibit corrosion inhibition in a water-1-propanol mixed refrigerant.

Comparative Example 19 is the case where sodium octyl propionate was added. Even if sodium octyl propionate is added to cooling water, it does not exhibit corrosion inhibition in a water-1-propanol mixed refrigerant.

Table 10 shows the amount of gas (hydrogen) generated by the corrosion of SS400 immersed in a water-1-propanol mixed refrigerant to which an oxyacid salt and an alkali metal hydroxide are added. Note that Comparative Example 1 is also described in this table.

The following can be understood from this table.

Example 15 is the case where lithium hydroxide and lithium molybdate were added as a corrosion inhibitor. Compared with the case where the corrosion inhibitor shown in Comparative Example 1 is not contained, the gas generation amount is extremely reduced and the corrosion is suppressed.

Example 16 is the case where lithium hydroxide and sodium benzenesulfonate were added as a corrosion inhibitor. Compared with the case where the corrosion inhibitor shown in Comparative Example 1 is not contained, the gas generation amount is extremely reduced and the corrosion is suppressed.

Example 17 is the case where calcium hydroxide and sodium orthovanadate are added as corrosion inhibitors. Compared with the case where the corrosion inhibitor shown in Comparative Example 1 is not contained, the gas generation amount is extremely reduced and the corrosion is suppressed.

Example 18 is the case where sodium hydroxide and sodium phosphonate are added as corrosion inhibitors. Compared with the case where the corrosion inhibitor shown in Comparative Example 1 is not contained, the gas generation amount is extremely reduced and the corrosion is suppressed.

FIG. 8 is a gram showing the LiOH concentration dependency of the amount of gas generated in the corrosion test in a water-1-propanol mixed refrigerant added with LiOH. As a test piece, SS400 is used.

As shown in FIG. 8, when 0.005 M of LiOH is added, the amount of gas generation decreases sharply to about 1/80, so it can be seen that the corrosion can be sufficiently suppressed by adding at least 0.005 M. When LiOH is added to 0.02 M, the gas generation amount decreases with the addition amount, but if 0.02 M or more, the degree of reduction of the gas generation amount decreases.

Figure 9 _is a graph showing the _Li 2 MoO ₄ concentration dependence of the generated gas amount of the corrosion test in water-1-propanol mixed refrigerant with the addition of Li 2 MoO _4. As a test piece, SS400 is used.

As shown in FIG. 9, as the concentration of Li ₂ MoO _{4 to be} added increases, the gas generation amount decreases linearly in logarithm. It can be seen that when 0.002 M is added, the amount of gas generation decreases to about 1/10 as compared with the case where it is not added and corrosion can be sufficiently suppressed.

The present invention is not limited to the embodiments described above. Those skilled in the art can make various additions and modifications within the scope of the present invention.

1: Evaporator, 2: Absorber, 3: High temperature regenerator, 4: Low temperature regenerator, 5: Condenser, 6: Heat exchanger, 7: Drain cooler, 8, 9: Pump, 10: Absorption refrigerator

Claims

A working medium for an absorption refrigerator, comprising a propanol aqueous solution as a refrigerant and a corrosion inhibitor.
The working fluid for an absorption refrigerator according to claim 1, wherein the corrosion inhibitor exhibits freezing point depression by addition.
The working medium for an absorption refrigerator according to claim 1 or 2, wherein the corrosion inhibitor contains any one or more of an alkali metal salt, an alkaline earth metal salt, and an oxyacid salt.
The operation according to claim 3, wherein the alkali metal salt is a hydroxide of an alkali metal, and the alkaline earth metal salt is a hydroxide of an alkaline earth metal. Medium.
The oxyacid salts include molybdate, tungstate, vanadate, silicate, phosphate, polyphosphate, phosphonate, hypochlorite, chlorite, perchlorate, It is a sulfonate, The working medium for absorption-type refrigerators of Claim 3 or 4 characterized by the above-mentioned.
The said propanol aqueous solution is an alcohol aqueous solution which consists of 1-propanol or 2-propanol, The working medium for absorption-type refrigerators as described in any one of the Claims 1-5 characterized by the above-mentioned.
The working medium for an absorption refrigerator according to any one of claims 1 to 6, wherein the propanol aqueous solution containing the corrosion inhibitor contains an alcohol other than propanol.
The working fluid for an absorption refrigerator according to claim 7, wherein the alcohol other than propanol is butanol.
The working fluid for an absorption refrigerator according to claim 7 or 8, wherein in the aqueous propanol solution, the concentration of alcohol other than propanol is lower than the concentration of propanol.
The working fluid for an absorption refrigerator according to any one of claims 1 to 9, wherein the propanol aqueous solution containing the corrosion inhibitor has a freezing point of -5 ° C or less.
Equipped with an evaporator, an absorber, a regenerator, and a condenser,
The absorption refrigerator characterized by using the working medium for absorption-type refrigerators as described in any one of Claims 1-10 as a working medium which circulates the said evaporator and the said condenser.