JP2000314572A - Absorbing solution for absorption refrigerator and absorption refrigerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress local corrosions and stress corrosion cracks in a metallic material of an absorbing solution by incorporating lithium halide except lithium iodide as an absorbent, and adding an alkali metal hydroxide compound or the like as an additive in the solution containing a refrigerant and the absorbent for absorbing a refrigerant vapor. SOLUTION: When the absorption refrigerator is operated, a low concentration absorbing solution absorbing a vapor refrigerant is heated by a heat source 20 in a high-temperature generator 21, sent to a separator 22, the refrigerant is evaporated in the separator 22, the solution is concentrated to become a highly concentrated absorbing solution. Meanwhile, the vapor refrigerant is sent to a condenser 28, cooled by a cooling tube 25, and arrived at an evaporator 26 as a liquid refrigerant to cool water passing a chilled water tub 29 through evaporation. In this case, as the solution, an absorbing solution obtained by incorporating lithium halide except lithium iodide and adding an alkali metal hydroxide compound, alkali metal iodide compound or the like as an additive is used, and hence local corrosions and stress corrosion cracks of a stainless steel used for the refrigerator are suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an absorption liquid for an absorption refrigerator containing a refrigerant and an absorbent for absorbing the vapor of the refrigerant, and an absorption refrigerator using the same.

[0002]

2. Description of the Related Art In absorption chillers, an aqueous solution of lithium halide, particularly an aqueous solution of lithium bromide, is often used as a solution for absorbing a refrigerant functioning as a cold heat source by an evaporating action, that is, an absorbing solution.

However, an aqueous solution of lithium bromide is corrosive to iron, copper, brass and the like, as is well known. For this reason,
In absorption refrigerators formed of these metallic materials,
It is essential to add a corrosion inhibitor to prevent corrosion. Conventionally, frequently used corrosion inhibitors include chromate,
Molybdate, nitrate and the like. Further, as another corrosion inhibitor, a composition in which an alkali metal hydroxide compound and an antimony compound are contained in an aqueous solution containing a halide salt is known (JP-A-1-174588).

[0004]

The highly oxidizing corrosion inhibitors such as chromates, molybdates and nitrates suppress corrosion by forming a dense protective coating on the surface of the metal material. However, absorption chillers use various metal materials, and it is difficult to prevent corrosion of all of them.

On the other hand, in recent years, air cooling of absorption refrigerators has been progressing,
The concentration of the absorbing solution has been increased, and the temperature inside the refrigerator has been increased. Under such severe conditions, the metal materials constituting the absorption refrigerator have begun to be stainless.
Stainless steel has significantly higher corrosion resistance than mild steel, but on the other hand, sufficient attention must be paid to corrosion such as local corrosion such as pitting and intergranular corrosion and stress corrosion cracking.

[0006] The corrosion inhibitors such as chromates, molybdates, nitrates, etc., described above, under the above-mentioned corrosive conditions for the corrosion prevention of stainless steel, have sufficient local corrosion,
Corrosion such as stress corrosion cracking cannot be suppressed. In addition, the above-described composition containing an alkali metal hydroxide compound and an antimony compound in an aqueous solution containing a halide salt suppresses corrosion of a metal material with respect to a lithium iodide aqueous solution, and causes local corrosion and stress. Not obvious for corrosion cracking.

[0007] It is an object of the present invention to suppress local corrosion and stress corrosion cracking of a metal material in an absorbing solution.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is directed to an alkali metal hydroxide compound, an iodide, and an additive for an absorption liquid for an absorption refrigerator, for example, an aqueous solution of lithium halide such as lithium bromide. That is, adding an alkali metal compound and an antimony compound. However, lithium halide excludes lithium iodide. Here, lithium hydroxide is an example of the alkali metal hydroxide compound. Examples of the alkali metal iodide compound include lithium iodide, sodium iodide, and potassium iodide. Examples of antimony compounds include antimony trioxide and antimony pentoxide.

As described above, by adding the three-component additive of the alkali metal hydroxide compound, the alkali metal iodide compound and the antimony compound to the absorbing solution, the ability to suppress local corrosion and stress corrosion cracking on the metal material, In particular, it suppresses stress corrosion cracking of austenitic stainless steel. The reason for this is that the alkali metal iodide compound and the antimony compound have the effect of increasing the pitting potential of the metal material, and thus suppress the occurrence of pitting of the metal material. Since stress corrosion cracking often occurs starting from the pitting corrosion, the occurrence of pitting corrosion is suppressed, thereby suppressing the occurrence of stress corrosion cracking.

[0010] The antimony compound in the present invention is adsorbed on the surface of the metal material which becomes high temperature inside the absorption refrigerator to form a film of the antimony compound. This film serves as an anticorrosion film to protect the metal material. In this case, if the absorption liquid is alkaline, the solubility of the antimony compound as a corrosion inhibitor increases, so that it is desirable to add an alkali metal hydroxide compound and use it in a highly alkaline state.

The addition amount of the alkali metal hydroxide compound is as follows:
It is preferable that 0.05 to 0.5% by weight, the addition amount of the alkali metal iodide compound is 0.03 to 0.5% by weight, and the addition amount of the antimony compound is 0.005 to 0.1% by weight. 0.05 alkali metal hydroxide compound
When the content is less than 10% by weight, the alkalinity of the absorbing solution is weak as described above, the ability to suppress the occurrence of pitting corrosion of the metal material is small, and the solubility of the antimony compound as a corrosion inhibitor does not increase. On the contrary, the content of the alkali metal hydroxide compound is 0.
If it is added in excess of 5% by weight, the alkalinity of the absorbing solution is too strong, and there is a possibility that corrosion by alkali may occur. When the amount of the antimony compound is less than 0.005% by weight, the anticorrosion ability cannot be expected, and the amount of the antimony compound is 0.1% by weight
If it exceeds, it will not dissolve and precipitates, and the excess added amount will not work effectively.

When the amount of the alkali metal iodide compound is less than 0.03% by weight, the effect of suppressing local corrosion and stress corrosion cracking cannot be expected. When the amount of the alkali metal iodide compound exceeds 0.5% by weight, conversely. In addition to releasing iodine ions to cause corrosion, it affects the physical properties of the absorbing solution.

Further, devices such as a generator, a condenser, an evaporator, an absorber and a solution heat exchanger are connected by a refrigerant connection path and a solution connection path, and a refrigerant and an absorbent for absorbing the vapor of the refrigerant are connected. In an absorption refrigerator that circulates an absorption liquid containing solution by a solution circulation means such as a solution pump, by using the absorption liquid for the absorption refrigerator described above, local corrosion and stress corrosion cracking of a metal material used in the absorption refrigerator are reduced. Suppress.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of an absorption liquid for an absorption refrigerator and an absorption refrigerator using the same according to the present invention will be described in detail.

The absorption liquid for the absorption refrigerator of the present embodiment contains, for example, lithium bromide as an absorbent and a water refrigerant. Further, an alkali metal hydroxide compound, an alkali metal iodide compound and an antimony compound are added as additives. However, the performance of suppressing the local corrosion and stress corrosion cracking of stainless steel forming the absorption refrigerator, particularly the suppression of stress corrosion cracking of austenitic stainless steel, is not limited to only lithium bromide as described above as an absorbent. Also, the present invention can be applied to an absorbing liquid such as lithium halide or lithium nitrate other than lithium iodide such as lithium chloride.

In this case, as described above, the absorbing solution containing lithium halide may cause corrosion if the content of the alkali metal iodide exceeds 0.5% by weight. An alkali metal hydroxide compound, an alkali metal iodide compound and an antimony compound are added as additives to an absorbing solution containing lithium halide. Further, in this case, the alkali metal hydroxide compound is 0.05 to 0.5% by weight, the alkali metal iodide compound is 0.03 to 0.5% by weight, and the antimony compound is 0.005 to 0.1% by weight. Add each. The use of such an absorbent solution composition suppresses local corrosion and stress corrosion cracking of stainless steel forming the absorption refrigerator, and particularly suppresses stress corrosion cracking of austenitic stainless steel.

Since the alkali metal iodide compound and the antimony compound have the effect of increasing the pitting potential of stainless steel, they are considered to suppress the occurrence of pitting in stainless steel. Since the stress corrosion cracking occurs at the base point of the pitting corrosion, it is considered that the occurrence of the pitting corrosion is suppressed by suppressing the occurrence of the pitting corrosion.

Further, the antimony compound is adsorbed on the surface of stainless steel, which becomes high temperature inside the absorption refrigerator, to form a film of the antimony compound. This film serves as an anticorrosion film and serves to protect the stainless steel surface. At this time, if the absorbing solution is alkaline, the solubility of the antimony compound as a corrosion inhibitor increases, so that it is desirable to add an alkali metal hydroxide compound and use it in a highly alkaline state.

When the content of the alkali metal hydroxide compound is less than 0.05% by weight, the alkalinity of the absorbing solution is weak, the ability to suppress pitting corrosion of stainless steel is small, and the solubility of the antimony compound as a corrosion inhibitor is low. Does not rise. Conversely, if the alkali metal hydroxide compound is added in excess of 0.5% by weight, the alkalinity of the absorbing solution is too strong, and there is a possibility that corrosion due to alkali may occur. When the amount of the antimony compound is less than 0.005% by weight, the anticorrosive effect cannot be expected. When the amount of the antimony compound exceeds 0.1% by weight, the antimony compound does not completely dissolve and precipitates. When the content of the alkali metal iodide is less than 0.03% by weight, corrosion inhibiting power cannot be expected. When the content of the alkali metal iodide exceeds 0.5% by weight, iodine ions are liberated to cause corrosion. In addition, it affects the physical properties of the absorbent.

Table 1 shows the results of the stress corrosion cracking test of Examples 1 to 5 of the absorbent for an absorption refrigerator according to the present invention and Comparative Examples 6 to 9 in comparison with the examples. Corrosion inhibitors LiI in Examples 1-5, were added instead of 5 levels of 0.03 to 0.5 wt%, 1 of Sb ₂ O30.03 wt% added to each level
Level, one level of addition of 0.15% by weight of LiOH. Comparative Example 6 has no additive, and Comparative Example 7 has LiOH
Only 0.15% by weight was added. Comparative Example 8 was Li ₂ M
oO ₄ 0.13 wt%, which was added LiOH0.15 wt%, Comparative Example 9 Li ₂ CrO ₄ 0.13 wt%, Li
0.15% by weight of OH was added.

The test conditions for stress corrosion cracking are as follows.

A) The test method was based on the WU vent test.

B) The test piece is 15 mm wide and 75 m long
The SUS316L plate having a thickness of 1 mm and a thickness of 1 mm was bent in a U-shape at R8 (radius 8 mm, the same applies hereinafter) and R9 in the longitudinal direction, and the two ends were fastened and fixed with Ti bolts and nuts at both ends. used.

C) The absorbing solution is a 60% aqueous solution of lithium bromide.
It was used.

D) The absorbing solution to which the corrosion inhibitor of each of Examples and Comparative Examples shown in Table 1 was added and the test piece were put in a pressure vessel and sealed, and the inside of the vessel was evacuated.

E) The pressure vessel of item d) is
After heating for hr, the test piece was taken out of the pressure vessel and observed.

As shown in Table 1, crevice corrosion was observed in Examples 1 and 2, but stress corrosion cracking was observed in Examples 1 to 5.
Neither has occurred. On the other hand, Comparative Examples 6 to 9
In each case, stress corrosion cracking and crevice corrosion occurred.
Therefore, when austenitic stainless steel is used as a constituent material of the absorption refrigerator, the use of the corrosion inhibitor according to the present embodiment can significantly reduce stress corrosion cracking as compared with the conventional corrosion inhibitor, and can reduce the stress. It is possible to omit a process in a manufacturing stage such as removal.

[0028]

[Table 1]

Table 2 shows the results of the non-condensable gas generation amount measurement test for the aqueous solutions of Examples 1 to 5 and Comparative Examples 6 to 9 shown in Table 1.

The test conditions for measuring the amount of non-condensable gas generated are as follows.

A) The surface of the test piece was water-resistant abrasive paper # 400.
40mm, length 110mm, thickness 1mm
Of SUS316L plate material of 6 pieces, the bolt made of Teflon,
The one fixed with a nut was used.

B) The absorbing solution is a 60% aqueous solution of lithium bromide.
It was used.

C) The absorbing solution containing the corrosion inhibitor of each of Examples and Comparative Examples shown in Table 2 and the test piece were placed in a pressure vessel and sealed, and the inside of the vessel was evacuated.

D) The pressure vessel of item c) is
After hr heating, the non-condensable gas extracted by a vacuum pump was collected by displacement on water, and the amount was measured.

As shown in Table 2, in Examples 1 to 5, the amount of noncondensable gas was 297 to 300 cc / m ² .
On the other hand, the non-condensable gases of Comparative Examples 6 to 9 were 400 to 6
It was 48 cc / m ² . The aqueous solution of the present example generates a very small amount of non-condensable gas as compared with the aqueous solution of the comparative example.
This is considered to be due to the antimony compound in the aqueous solution adsorbing to the stainless steel surface and acting as an anticorrosion film, thereby significantly reducing the non-condensable gas, which is a major enemy for absorption refrigerators compared to conventional corrosion inhibitors. . As a result, the maintenance interval (maintenance inspection period) of the absorption refrigerator can be lengthened.

[0036]

[Table 2]

FIG. 1 is a schematic view showing an embodiment of an absorption refrigerator using the absorption liquid for an absorption refrigerator according to the present invention. The operation of the absorption refrigerator will be briefly described. The low-concentration absorbing liquid that has absorbed the vapor refrigerant is heated by the heating source 20 in the high-temperature generator 21 and sent to the separator 22, where the refrigerant evaporates and the absorbing liquid is concentrated to become a high-concentration absorbing liquid. The high-concentration absorbent is sent to the heat exchanger 23, exchanges heat with the low-concentration absorbent sent from the low-temperature absorber 24, is cooled, and is cooled.
4 is introduced.

The low-temperature high-concentration absorbing liquid is dispersed in the absorber 24 and cooled by the cooling pipe 25, and absorbs the vapor refrigerant from the evaporator 26 to become a low-concentration absorbing liquid. Further, the low-concentration absorbent is sent to the high-temperature generator 21 via the heat exchanger 23 by the circulation pump 27 and is recycled.

On the other hand, the high-temperature vapor refrigerant evaporated from the separator 22 is introduced into the condenser 28, cooled by the cooling pipe 25, and condensed into a liquid refrigerant. The liquid refrigerant is supplied to the evaporator 26 to be evaporated, lowered to a low temperature and evaporated, and the water passing through the cold water pipe 29 is cooled by the latent heat of evaporation into cold water. This vapor refrigerant is absorbed by the high-concentration absorbent in the absorber 24. Cold water is used for indoor cooling.

The absorption refrigerating machine of the above embodiment uses the absorbing solution of the above Examples 1 to 5 to cause local corrosion and stress corrosion cracking of the stainless steel used for the absorption refrigerating machine, especially austenitic stainless steel. Suppress stress corrosion cracking on steel.

[0041]

According to the present invention, it is possible to suppress local corrosion and stress corrosion cracking of a metal material in an absorbing solution.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of an absorption refrigerator using an absorption liquid for an absorption refrigerator according to the present invention.

[Explanation of symbols]

 Reference Signs List 20 heating source 21 high temperature generator 22 separator 23 heat exchanger 24 absorber 25 cooling pipe 26 evaporator 27 circulation pump 28 condenser 29 chilled water pipe

Claims (3)

[Claims] 1. An absorption liquid for an absorption refrigerator including a refrigerant and an absorbent for absorbing a vapor of the refrigerant, the absorption liquid containing lithium halide other than lithium iodide, and an alkali metal hydroxide compound as an additive; An absorption liquid for an absorption refrigerator comprising an alkali metal iodide compound and an antimony compound. 2. The method according to claim 1, wherein the addition amount of the alkali metal hydroxide compound is 0.05 to 0.5% by weight, the addition amount of the alkali metal iodide compound is 0.03 to 0.5% by weight, The amount of antimony compound added is 0.0
An absorption liquid for an absorption refrigerator, which is contained in an amount of from 0.05 to 0.1% by weight. 3. An absorption device comprising a generator, a condenser, an evaporator, an absorber, and a solution heat exchanger, wherein these devices are connected by a refrigerant connection path and a solution connection path to absorb the refrigerant and the vapor of the refrigerant. An absorption chiller that circulates an absorbent containing an agent by a solution circulating means, wherein the absorption chiller according to claim 1 or 2 is used.