JPS6029872B2 - absorption refrigerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an absorption refrigerating machine with a closed circulation system, and more particularly to an absorption refrigerating machine in which a corrosion-resistant protective film is formed on the surface of an iron-based material.

A closed circulation system absorption refrigerator has a restriction in operation that the maximum pressure must be below atmospheric pressure, and generally water is used as the refrigerant and a concentrated lithium bromide aqueous solution is used as the absorption liquid.

The principle system diagram of the absorption refrigerator to which the present invention is applied is shown in FIG. 1.
, an evaporator 4, a condenser 5 and a pump 8, and an absorber 3
, the regenerator 1 and the pump 8 function in the same way as the compressor of a compressor type refrigerator. During operation of the refrigerator, the absorption liquid is pumped as a concentrated absorption liquid 6 to the regenerator 1, heat exchanger 2, and absorber 3, and from the absorber 3 as a dilute absorption liquid via the heat exchanger 2 to the regenerator 1.
sent to and circulated. In general, the higher the concentration of the absorption liquid (the higher the temperature for concentration), the higher the refrigeration efficiency can be obtained. For example, in the regenerator 1, which has the highest temperature, the temperature is 16,000, the lithium bromide concentration is 65%, and the absorber 3, the lowest temperature. So about 40q
o, it will be about 60%.

On the other hand, the corrosivity of lithium bromide solution becomes more severe as the temperature and concentration increase. Therefore, unless a suitable corrosion inhibitor is added to the absorption liquid, the carbon steel and steel alloys that are the constituent materials of the refrigerator will corrode severely. The corrosion inhibitors currently widely used are inorganic corrosion inhibitors, most of which are oxidizing agents.
Passivates the iron surface to suppress corrosion. Typical examples include chromate, molybdate, tungstate,
These include nitrites and nitrates. Chromate is the most commonly used and has great corrosion inhibiting power, but the drawback is that Cr60 is easily reduced by octyl alcohol in the absorption liquid, so the concentration of CrO42 changes greatly and the corrosion inhibiting power is rapidly lost. At the same time, there is a big problem that pitting corrosion is very easy to occur. Tungstates have a low corrosion inhibiting ability, and nitrites and nitrates are easily reduced by hydrogen generated by iron corrosion in high-temperature, high-concentration absorption liquids, which has an adverse effect on toxic gases such as nitrogen oxides and copper alloys. There are disadvantages such as generation of ammonia. Compared to these, molybdate has superior corrosion inhibiting ability,
It has good resistance to localized corrosion such as pitting corrosion and crevice corrosion, and its toxicity is much lower than that of chromates and nitrites. However, molybdate has a low solubility, especially in concentrated lithium bromide solutions such as absorption liquids, making it difficult to obtain a practical concentration. Therefore, it is difficult to obtain a corrosion-resistant coating with sufficient corrosion inhibiting power. It was extremely difficult. The present invention has been made in view of the above-mentioned current situation, and its purpose is to provide an absorption refrigerating machine having a corrosion-resistant coating that can sufficiently prevent corrosion of the absorption refrigerating machine by solving the drawbacks of the conventional technology. .

To give an overview of the present invention, in a closed circulation absorption refrigerator that uses an aqueous lithium bromide solution as an absorption liquid and water as cold soot, molybdate is added to the surface of a component made of an iron-based material that is in contact with the absorption liquid. The present invention relates to an absorption refrigerating machine characterized by forming a corrosion-resistant film composed of an iron oxide film formed by the above method and an adsorption film formed by molybdate and triazole.

Absorption chiller component materials are exposed to a highly corrosive environment in a high-temperature, high-concentration lithium bromide aqueous solution as an absorption liquid, so they generally require the use of a corrosion inhibitor. When molybdate is used from the viewpoint of pollution, etc., the solubility of molybdate is low and it is difficult to obtain the required concentration, as described above.

Furthermore, copper alloys are also used as constituent materials other than iron in absorption refrigerators, but since the corrosion inhibitors mentioned above are strong oxidizing agents, they have weak corrosion inhibiting power against copper, and the melted Cr20 Another drawback was that it deposited on the iron surface, forming local batteries and accelerating the corrosion of the iron. Based on a series of experiments related to corrosion inhibition, the present invention has been found to have excellent high-temperature stability despite being an organic material.
Focusing on penzotriazole, which has a large corrosion inhibiting effect on copper, the idea was created to form a highly corrosion-resistant film by using it in combination with molybdate. That is, according to the present invention, penzotriazole itself has a small corrosion inhibiting effect on iron and has not been used in the past, but even if the concentration of molybdate corrosion inhibitor is below the practical concentration, penzotriazole can be added to the corrosion inhibitor. It was recognized that the following excellent effects were achieved by using Sol in combination. Its typical effects are ■
It forms a corrosion-resistant film that exhibits much better corrosion protection than each corrosion inhibitor alone, greatly improving its ability to prevent pitting corrosion, crevice corrosion, galvanic corrosion, etc. ■Consumption of corrosion inhibitors is significantly lower than when each agent is used alone, making maintenance and management easier. ■No toxic gas is generated due to reductive decomposition, etc. ■ Elution of copper into the absorption liquid is suppressed, allowing the refrigerator to exhibit stable performance. As described above, by employing a mixed corrosion inhibitor, the drawbacks of conventional molybdates can be overcome and a corrosion-resistant film can be formed, which can greatly contribute to improving the performance and lifespan of absorption refrigerators. The lithium bromide aqueous solution used as the absorption liquid for absorption refrigerators generally has a lithium bromide concentration of 55 to 65% and a lithium hydroxide concentration of 0 to 0.5%, and a surfactant for the piping in the absorber. For example, 5 to 50% of n-octyl alcohol may be added. In order to experimentally confirm the above effects, the present inventors found that the concentration of lithium bromide was 62% and the concentration of lithium hydroxide was 0.2%.
% aqueous solution was prepared, and if necessary, n-octyl alcohol was added thereto to prepare an absorbent solution having a composition equivalent to that of an absorbent solution for practical use.

A corrosion inhibitor was added to this absorption liquid at a predetermined concentration to prepare a feed liquid. The corrosion experiment was conducted using a glass ampoule containing 10 parts of the supply liquid and a carbon steel plate (SS41) with a surface area of 12 parts, which is the constituent material of the refrigerator.
) and 25 section steel pipes as metal test pieces, each singly or aligned in a vacuum sealed state, and held under the same conditions as in the regenerator 1 of the refrigerator, that is, in an electric furnace at 160 qo for 20 hours. The ampoule was crushed, a test piece was taken out, and the amount of corrosion was determined from the amount of weight loss after scale was removed. Table 1 Corrosion Inhibition Effect of Various Corrosion Inhibitors on Carbon Steel From Table 1 above, it is clear that lithium molybdate exhibits superior corrosion effects compared to other corrosion inhibitors, and also lithium molybdate has a strong tendency to cause local corrosion, whereas lithium molybdate has a strong tendency to cause local corrosion.
The entire surface was covered with a protective film mainly composed of 4, and no tendency for local corrosion was observed.

Solubility of lithium molybdate in the absorption liquid Figure 2 shows the solubility of lithium molybdate in the absorption liquid as a function of temperature (00) and amount of dissolution (yield 9/night). From the cycle shown in Figure 1, it can be seen that the highest temperature regenerator (160oC) has a melting rate of about 9/1000, while the lowest temperature absorber (40oC) has a melting rate of about 100/9/the melt. As a result, in the absorption refrigerator as a whole, since precipitation occurs in the low-temperature section, only about 100 pairs of 9/2 are dissolved and circulated at all times. Relationship between concentration of lithium molybdate and corrosion inhibition effect.

FIG. 3 shows the relationship between the lithium molybdate concentration (9/d difference) and the corrosion amount (9/d deviation). Figure 3 shows the case where no corrosion inhibitor is added (not shown, but 9/d of 750
It is shown that the amount of corrosion decreases almost linearly as the concentration changes from ) to 300 females/event, and after that, even if the concentration is increased, there is no significant change in the effect of reducing the amount of corrosion. Acid lithium salt alone is 300% for corrosion prevention.
A concentration of 9/h or higher is desirable. From both the solubility of lithium molybdate in the absorption liquid shown in Figure 2 and the relationship between the concentration of lithium molybdate and the amount of corrosion shown in Figure 3, it has been found that when the lithium molybdate concentration is 100 skins/night during operation of a practical machine. The desired corrosion inhibition effect must be achieved.

Therefore, penzotriazole was added to absorption liquids with various lithium molybdate concentrations, and its corrosion inhibiting effect was measured. Figure 4 shows the measurement results, where A is the penzotriazole concentration 5/9/2, B is 10/9/2, C is 80/9/2, D is 800/9/2, and E also indicates the case of 8000M/. From Figure 4, 9/or more of penzotriazole 5, lithium molybdate 2
It can be seen that the corrosion inhibitors, lithium molybdate, and benzotriazole used in the past are proportionally more effective when used alone at 9/5/h or higher. Observation of the cross section of the test piece after the test revealed that the lower layer was a dense black film mainly composed of Fe304 produced from lithium molybdate, and the upper layer was an adsorption film formed from molybdate and penzotriazole. It was recognized that there were multiple layers of protection. In the above experiment, we explained the case of lithium salt as molybdate.
The same applies to sodium salts.

From the above experiments, it is clear that an absorption refrigerator in which the above-mentioned double-layer corrosion-resistant film is formed on the surface of a component made of an iron-based material that is in contact with an absorption liquid has corrosion resistance.

Next, the present invention will be described with reference to Examples, but the present invention is not limited thereto in any way.

Example 1 Lithium molybdate 100:9 was added to an aqueous solution with a lithium bromide concentration of 62% and a lithium hydroxide concentration of 0.2%.
An absorption solution was prepared by adding penzotriazole at various concentrations.

The corrosion inhibiting effect of this absorption liquid on carbon steel is shown in FIG.

The effective concentration range of penzotriazole is wide, approximately 9 in 10
/Shows stable corrosion inhibition effect at concentrations higher than that. It is clear that a corrosion-resistant film consisting of the above-mentioned double layer was formed on the surface of the carbon steel in this example, and that this film suppressed corrosion.

Example 2 Lithium bromide concentration 62%, lithium hydroxide concentration 0.2%
Absorption liquid F was prepared by adding n-octyl alcohol 4/day, 9/day of lithium molybdate, and 800/day of penzotriazole to the aqueous solution.

Absorption liquid G without the addition of lithium molybdate as a control
was prepared. The absorption liquids F and G were maintained in a practical condition, that is, at 16,000, and the time change in the consumption amount due to decomposition of penzotriazole was measured, and the results are shown in FIG.

Compared to absorption liquid G, benzotriazole is hardly consumed in absorption liquid F, extraction with n-octyl alcohol is not observed, and Moo42- is also hardly consumed, which indicates the stability of this absorption liquid. It is clear that the properties are excellent. Example 3 Lithium bromide concentration 62%, lithium hydroxide concentration 0.2%
An absorption liquid was prepared by adding 100 parts of lithium molybdate and 800 parts of benzotriazole to the aqueous solution.

The corrosion inhibition effect was measured using a copper alloy (cupronickel) as a test piece.

As a control, each corrosion inhibitor was added individually and the corrosion inhibition effect was measured in the same manner. In the case of the mixed inhibitor of the present invention, the corrosion amount was 59/d, and in the case of lithium molybdate alone, the corrosion inhibition effect was measured. It was 9/d of 21, and 9/d of 5 in the case of benzotriazole alone. Example 4 An absorption liquid similar to that in Example 3 was prepared.

FIG. 7 is a perspective view of a model of the partial structure of the regenerator 1 of the refrigerator, in which 15 is a cupronickel tube, 16 is a stainless steel bolt, 17 is a carbon steel plate, 18 is a stainless steel nut, and 19 is a Teflon sheet. be.

This model was immersed in an absorption liquid and a corrosion test was conducted. As a control, similar corrosion tests were conducted on absorbents to which each corrosion inhibitor was added alone, and the models were observed. The results are shown in a photograph in FIG. In Figure 8, day is penzotriazole 800 9/〆 alone, 1 is Lj2Moo4
100 kites 9/single, J indicates a combination of both (this example). From FIG. 8, it is clear that in No. 1 and No. 1, severe local corrosion occurs due to gaps and contact between different metals, whereas in No. J, it is clear that the local corrosion suppressing effect is extremely excellent. When this test piece was examined, it was confirmed that a corrosion-resistant film consisting of a double layer was formed on its surface as described above, and the formation of this film made it possible to obtain an absorption refrigerator with good corrosion prevention properties.

From the above results, it is recognized that, according to the present invention, the corrosion-resistant film formed by the mixed corrosion inhibitor has an excellent corrosion-inhibiting effect and stable performance over a long period of time.

In particular, by adding a small amount of penzotriazole, it is possible to use molybdate at a low concentration, and if a corrosion-resistant film is formed due to the synergistic effect, it will greatly contribute to maintenance management and cost reduction of refrigerators.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing the flow of absorption liquid and refrigerant in a closed circulation system absorption refrigerator to which the present invention is applied. FIG. 2 shows the solubility of lithium molybdate in a 62% aqueous lithium bromide solution. FIG. 3 shows the relationship between the concentration of lithium molybdate and the corrosion inhibition effect. FIG. 4 shows the relationship between the concentration of lithium molybdate, the amount of penzotriazole added, and the corrosion inhibiting effect. FIG. 5 shows the relationship between penzotriazole concentration and corrosion inhibition effect. 6th
The figure shows the decomposition of penzotriazole in the absorption liquid and the stabilizing effect of the coexistence of lithium molybdate. FIG. 7 is a perspective view of a model of a partial structure of the absorber 1 of a refrigerator to which the present invention is applied. FIG. 8 is a photograph showing the corrosion inhibiting effect of one specific example of the present invention and a control example using the model shown in FIG. 7 as a sample. Explanation of symbols: In Fig. 1, 1... Regenerator, 2... Heat exchanger, 3... Absorber, 4... Evaporator, 5.
... Condenser, 6 ... Concentrated absorption liquid, 7 ...
・Dilute absorption liquid, 8... pump, 9... line medium,
10...Cooling water, 11...Water vapor, 1
2...Water vapor, 13...Cold water, 14...
...Cooling water, in Figure 7, 15... Cupronickel tube, 16... Stainless steel bolt, 17...
...Carbon steel plate, 18...Stainless steel nut, 1
9...7 front seat. Figure 2, figure O, figure 3, figure 5, figure 4, figure 6, figure 8, figure 8.

Claims (1)

[Claims] 1. In a closed circulation absorption refrigerator that uses an aqueous lithium bromide solution as an absorption liquid and water as a refrigerant, an iron oxide film formed from molybdate and a molybdenum An absorption refrigerating machine characterized by forming a corrosion-resistant film composed of an adsorption film formed of an acid salt and a triazole.