JP3336087B2 - Absorption liquid composition for absorption refrigerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an absorbent composition for use in an absorption refrigerator.

[0002]

2. Description of the Related Art Generally, an aqueous solution of lithium bromide having a high concentration of about 60% is used as an absorption liquid for an absorption refrigerator. A high-concentration aqueous solution of lithium bromide is corrosive to iron and iron alloys, causing corrosion of components of the absorption refrigerator. In particular, corrosion in a high-temperature portion in the process of concentrating the absorbing solution has become a problem.

Various compounds added as corrosion inhibitors to reduce such corrosion have been proposed, for example, inorganic compounds such as lithium molybdate, lithium chromate and lithium nitrate, and heterocyclic compounds such as benzotriazole. .

[0004]

The above-mentioned inorganic compounds are:
An oxide film is formed on the iron surface to suppress corrosion. However, if the formed oxide film has a defect, local corrosion occurs. Furthermore, since it is reduced and consumed itself, a long-term corrosion inhibiting effect cannot be expected. Further, a heterocyclic compound such as benzotriazole is difficult to dissolve in a high-concentration aqueous solution of lithium bromide, does not dissolve enough to exhibit a corrosion inhibiting effect, and its effect is not sufficient.

Even if the inorganic compound and the heterocyclic compound such as benzotriazole are added to mild steel as a corrosion inhibitor, corrosion cannot be completely suppressed. Although its use has been studied, corrosion progresses preferentially from the defective portion of the oxide film formed on the surface of stainless steel, and the occurrence of pitting corrosion is a problem.

[0006] In addition, when a corrosion inhibitor of an oxide film forming type of an inorganic oxidizing agent such as molybdate is used even in mild steel, there is a problem that pitting corrosion occurs from a defective portion of the formed oxide film.

An object of the present invention is to provide an absorption liquid composition for an absorption refrigerator in which corrosion of iron and iron alloys, particularly pitting corrosion, is suppressed.

[0008]

SUMMARY OF THE INVENTION The present invention is an absorbent composition for an absorption refrigerator, comprising adding polyethyleneimine to an aqueous solution containing lithium bromide as a main component.

[0009] The present invention also provides an absorbent composition for an absorption refrigerator, wherein polyethyleneimine and 0.1 to 1 g / l of a molybdate are added to an aqueous solution mainly containing lithium bromide. It is.

Further, the present invention is characterized in that the amount of the polyethyleneimine added is 0.1 to 30 g / l.

The present invention is also characterized in that the polyethyleneimine has an average molecular weight in the range of 300 to 70,000.

[0012]

According to the present invention, a composition obtained by adding polyethyleneimine to an aqueous solution containing lithium bromide as a main component is effective in suppressing the corrosion of iron and iron alloys, particularly pitting corrosion. This is thought to be due to the fact that polyethyleneimine has the effect of increasing the pitting potential, thereby suppressing pitting of iron, particularly stainless steel.

The amount of polyethyleneimine to be added is as follows:
0.1 g to 30 g per liter, preferably 0.5 to
10 g. Addition of 0.1 g or less has no effect,
Even if it is added in an amount of 30 g or more, improvement in corrosion inhibition cannot be expected.
The average molecular weight of the added polyethyleneimine is not particularly limited, but is preferably 300 to 70,000. Those having a low molecular weight of 300 or less have poor thermal stability, and those having a molecular weight of 70,000 or more have poor solubility in a high-concentration lithium bromide aqueous solution.

For stainless steels which originally have an oxide film on the surface, pitting corrosion can be sufficiently prevented only by the addition of polyethyleneimine. Molybdate is added to form the coating. The addition amount of the molybdate is 0.1 to 1 g per liter of the absorbing solution. The amount added is 0.
If the amount is less than 1 g, there is no effect, and if more than 1 g is added, the effect is not improved, and there is a problem in solubility. Although there is no particular problem with adding molybdate to stainless steel, improvement in the pitting corrosion inhibiting effect cannot be expected. The molybdate is not particularly limited, but when an aqueous solution of lithium bromide is used as the absorbing solution, lithium molybdate is preferable.

The above-mentioned addition amount is the weight per liter of the absorption liquid to be filled in one set of absorption refrigerator.
Since the absorption liquid has a different concentration of lithium bromide and the like in each part of the absorption refrigerator, it is considered that the concentrations of the polyethyleneimine and molybdate of the present invention are naturally different.

As the absorbing solution, an aqueous solution of lithium bromide having a high concentration of 50 to 70% is usually used. However, an inorganic compound or an organic compound which does not impair the corrosion inhibiting performance of polyethyleneimine may be contained. In addition, it is generally effective to make the absorbing solution alkaline with lithium hydroxide or the like and use it for anticorrosion.

[0017]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.

Examples 1 to 5 SUS444 (19Cr, 2Mo) 25 × 25 × 1
(Mm) test piece was polished to # 400 with sandpaper. Next, the polyethyleneimine and molybdic acid of the present invention shown in Table 1 were added to a solution corresponding to an absorption solution in which a 55% aqueous solution of lithium bromide was adjusted to pH 12 with lithium hydroxide to prepare a test solution. The sample was placed in a Teflon container having a stainless steel casing of 30 ml, immersed in the test piece, degassed while adding nitrogen gas, and then sealed tightly.
For 300 hours. Table 1 shows the test results.

Comparative Examples 1 to 3 The same test pieces as in Examples 1 to 5 were replaced with lithium molybdate or chromium as shown in Table 1 in place of the test solution without the additive of the present invention or the additive of the present invention. Lithium oxide was immersed in a test solution to which 0.5 g / l was added, and tested in the same manner as in Examples 1 to 5. Table 1 shows the test results.

[0020]

[Table 1]

Examples 6-9 Except that mild steel (cold rolled steel plate: SPCC) was used for the test piece,
Tested in the same manner as in Examples 1-5. However, the additive of the present invention used polyethyleneimine and lithium molybdate in combination. Table 2 shows the test results.

Comparative Examples 4 to 6 Tests were conducted in the same manner as in Comparative Examples 1 to 3, except that the same mild steel as in Examples 6 to 9 was used for the test pieces. Table 2 shows the test results.

[0023]

[Table 2]

From the test results in Tables 1 and 2, the weight loss of the test piece before and after the test was determined for the corrosion weight loss, and this was calculated as mdd (mg
/ Dm ² / day), and the presence or absence of pitting is indicated by visual observation after the test.

In Examples 1 to 5, the test piece SUS444 was used.
Was used, but other stainless steels such as SUS430
The same effect was confirmed even when used for such purposes.

[0026]

As described above, according to the present invention, corrosion of iron and iron alloys, which are constituent materials of an absorption refrigerator, is caused by a high-concentration aqueous solution of lithium bromide, such as an absorption liquid of the absorption refrigerator. Pitting corrosion can be significantly suppressed. This solves the problem caused by corrosion of the absorption refrigerator and enables stable operation for a long period of time.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C23F 11/14 C09K 5/08 C23F 11/18 F25B 15/00

Claims (4)

(57) [Claims] 1. An absorbent composition for an absorption refrigerator, wherein polyethyleneimine is added to an aqueous solution mainly containing lithium bromide. 2. An absorption liquid composition for an absorption refrigerator, wherein polyethyleneimine and 0.1 to 1 g / l of a molybdate are added to an aqueous solution containing lithium bromide as a main component. 3. The method according to claim 1, wherein the amount of the polyethyleneimine added is 0.
The absorption liquid composition for an absorption refrigerator according to claim 1 or 2, wherein the absorption liquid composition is 1 to 30 g / l. 4. The absorption liquid composition for an absorption refrigerator according to claim 1, wherein the average molecular weight of the polyethyleneimine is in a range of 300 to 70,000.