JPS6249544B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a closed circulation type absorption refrigerator which uses a lithium bromide aqueous solution as an absorption liquid and performs cooling by repeatedly concentrating the liquid, diluting the refrigerant, and exchanging heat. Closed circulation absorption refrigerators use water as the refrigerant and a concentrated aqueous solution of lithium bromide as the absorption liquid. As shown in the principle diagram in Fig. 1, this refrigerator has a regenerator 1, a condenser 2, an evaporator 3, an absorber 4, and circulates absorption liquid 6, 6a, 6b and refrigerant 7 between them. Pumps 8 and heat exchanger 5
Each part operates as follows. (A) Evaporator 3 Cold water 12 flows through the tubes of the evaporator tube bundle of the evaporator 3, and refrigerant 7 is spread outside the tubes, and the latent heat of evaporation removes heat from the cold water. (B) Absorber 4 Lithium bromide aqueous solution has significantly lower vapor pressure than water at the same temperature, and can absorb water vapor generated at considerably lower temperatures. In the absorber 4, the refrigerant evaporated in the evaporator 3 is absorbed by a lithium bromide aqueous solution (absorbing liquid) 6 sprinkled on the outer surface of the tube bundle of the absorber, and the absorbed heat generated at this time is cooled by cooling water 13 passing through the tubes. be done. (C) Regenerators 1a, 1b The concentration of the dilute solution 6b that has absorbed the refrigerant in the absorber 4 decreases, and its absorption capacity becomes weaker. A part of the solution is sent to the high-temperature regenerator 1a by the solution circulation pump 8, heated by high-temperature steam 11, etc., the refrigerant vapor 10 is evaporated and separated, the solution is concentrated, and the concentrated solution 6a is returned to the absorber 4. Further, a part of the dilute solution 6b discharged from the absorber 4 is sent to the low temperature regenerator 1b by the solution circulation pump 8, and the refrigerant vapor 10 generated in the high temperature regenerator 1a is
The concentrated solution 6a is concentrated by heating and returned to the absorber 4. (D) Condenser 2 The refrigerant vapor 10 separated in the regenerator 1 is transferred to the condenser 2.
It is cooled by the cooling water 9 flowing through the pipe, condenses and liquefies, and returns to the evaporator 3. (E) Heat exchanger 5 The low-temperature dilute solution 6b heading from the absorber 4 to the regenerator 1 is preheated by the high-temperature concentrated solution 6 heading from the regenerator 1 to the absorber 4, thereby reducing the regenerator heating amount. (F) Pump 8 The pump 8 circulates the concentrated solution 6a, dilute solution 6b, and refrigerant 7. The absorber 4, the regenerator 1 and the pump 8 have the same function as the compressor of a compression refrigerator. Absorption liquid 6, 6a
and 6b circulate between the regenerator 1 and the absorber 4 via the heat exchanger 5 during refrigerator operation. Generally, the higher the concentration of the absorption liquid, the higher the refrigeration efficiency, so the regenerator 1 needs to be maintained at a higher temperature in order to concentrate the absorption liquid. On the other hand, the higher the temperature and concentration of the lithium bromide aqueous solution, the more corrosive it becomes to steel and copper, which are the constituent materials of the refrigerator. Therefore, it is essential to add an inhibitor to the absorption liquid to prevent corrosion. By the way, most of the inhibitors that have been put into practical use so far have been chromate salts, and although there have been some examples of the use of molybdate salts, their use is limited to only a few due to their poor solubility at low temperatures. . All of the above inhibitors are oxidizing agents and suppress corrosion by forming a dense protective film on the iron surface. However, it has been difficult to provide complete corrosion protection for all of the several types of refrigerator constituent materials. That is, the above-mentioned inhibitors not only have no anticorrosive effect on copper-based materials, but also sometimes even promote corrosion. Another drawback was that the copper ions eluted at that time precipitated on the surface of the iron, making the iron more susceptible to corrosion due to the potential difference between the two metals. In addition, organic inhibitors that have a corrosion-preventing effect on copper-based materials not only cause stability problems in regenerators, etc., which are exposed to high temperatures of 160°C or higher during refrigeration operation, but also cause problems with the corrosion of the most severely corroded iron in the regenerator. The drawback was that it had a poor anticorrosive effect on other types of materials. An object of the present invention is to provide a closed circulation absorption refrigerator that has excellent corrosion resistance against aqueous lithium bromide solutions. Another object of the present invention is to provide a closed circulation absorption refrigerator which has excellent corrosion resistance and high cooling efficiency. In order to achieve such an objective, the present invention
Refrigeration is obtained by repeatedly condensing a lithium bromide aqueous solution, diluting the refrigerant, and exchanging heat sealed in a closed circulation system consisting of a regenerator, condenser, evaporator, absorber, and heat exchanger. In the closed circulation type absorption refrigerator, the lithium bromide aqueous solution contains a sufficient amount of ruthenium chloride to substantially function as an inhibitor. In the present invention, ruthenium chloride hydrolyzes a member made of iron or an iron alloy in an absorption liquid, and the hydrolysis product forms a film, which is thought to suppress corrosion. Although the present invention is effective for single-effect closed circulation absorption refrigerators, it is particularly effective for double-effect closed circulation absorption refrigerators. This is because the inhibitor has superior solubility compared to molybdate inhibitors and the like, so there is no fear of precipitation or precipitation even when the absorbing liquid is at a low temperature. The amount of ruthenium chloride in the present invention, namely:
The concentration should be sufficient to prevent corrosion of the constituent materials, but practically it is sufficient if it is 2×10 ⁻⁴ mol/l or more. However, if the concentration becomes too high, the amount of precipitates in the liquid will increase, so it is preferably within the range of 2×10 ⁻⁴ mol/l to 5×10 ⁻² mol/l. In the present invention, it is preferable to use an alkaline agent such as LiOH, NaOH, or KOH as a pH adjuster in the absorption liquid in combination, thereby making the effect of ruthenium chloride even more pronounced. Also, a surfactant such as octyl alcohol can be added to the absorption liquid to increase the thermal efficiency of the absorber, without any loss in the anticorrosion effect of ruthenium chloride. Although the types and proportions of the constituent materials of the present invention differ slightly depending on the type of heat source such as combustion gas or steam such as gas, kerosene, and heavy oil, the present invention exerts its effects on all such models. Furthermore, the absorbent liquid of the present invention has no pollution concerns compared to absorbent liquids using chromate or the like. Next, examples will be described in detail. [Example 1] 62% by weight of lithium bromide and 0.2% of lithium hydroxide were added to an aqueous solution in which a predetermined amount of ruthenium chloride was dissolved.
An absorption liquid was prepared by adding % by weight. Using this absorption liquid, a corrosion test was conducted on carbon steel (SS-41) at 160°C for 200 hours. The corrosion test was conducted after the absorbent was degassed. Figure 2 shows the amount of corrosion at that time. As a comparative example, the amount of corrosion in carbon steel was 500 mg/dm ² as a result of a test using an absorbing liquid containing a lithium chromate inhibitor, which has been conventionally used.
In the conventional example, sharp and deep pitting corrosion occurs and the amount of corrosion varies, so the average value of 10 specimens was used. On the other hand, in the example, the test piece was covered with a uniform thin black film. As is clear from FIG. 2, the amount of corrosion in the example was 20 to 30 mg/dm ² , which was significantly reduced compared to the conventional example, and the effect was remarkable. [Example 2] 62% by weight of lithium bromide and 0.2% by weight of lithium hydroxide were added to an aqueous solution in which ruthenium chloride was dissolved at 8×10 ^-4 mol/l, and further n
- The absorption liquid was prepared by adding 25 mol/l of octyl alcohol. Using this absorption liquid, carbon steel (SS-41), oxygen-free copper (OFCuP), 70/30 Cypronickel (copper 70
%, Nickel 30% alloy) (CNTF-3) were subjected to corrosion tests at 160°C for 0 to 1000 hours. Figure 3 shows the amount of corrosion at that time. In FIG. 3, reference numeral 14 indicates the amount of corrosion of mild steel, 15 indicates the amount of corrosion of oxygen-free copper, and 16 indicates the amount of corrosion of 70/30 Cypronickel. The amount of corrosion tends to reach saturation over time for all materials, and
It is clear that the change over time is extremely small and that it exhibits a stable anticorrosive effect. The corrosion pattern of mild steel, oxygen-free copper, and 70/30 cupronite after the test was a general corrosion type, and no abnormal corrosion such as pitting corrosion, which is seen with conventional inhibitors (chromate), was observed. As is clear from the above examples, according to the present invention, the constituent materials of an absorption chiller can be extremely effectively protected from corrosion, and moreover, stable corrosion protection performance can be maintained for a long period of time, and the cooling effect can be improved. It can be seen that excellent effects can be obtained.

[Brief explanation of the drawing]

Figure 1 is a diagram of the principle of a closed circulation absorption refrigerator according to an embodiment of the present invention, Figure 2 is a graph showing the relationship between the concentration of ruthenium chloride and the amount of corrosion, and Figure 3 is a diagram of mild steel and oxygen-free copper. It is a graph showing the relationship between time and corrosion amount for 70/30 Cypronickel. 1a...High temperature regenerator, 1b...Low temperature regenerator, 2...Condenser, 3...Evaporator, 4...Absorber, 5...Heat exchanger.

Claims (1)

[Claims] 1. Condensation of an aqueous lithium bromide solution, refrigerant dilution, and heat exchange sealed in a closed circulation system configured by sequentially combining a regenerator, a condenser, an evaporator, an absorber, and a heat exchanger. A closed circulation type absorption refrigerating machine that repeatedly obtains cold air, wherein the lithium bromide aqueous solution contains a sufficient amount of ruthenium chloride to substantially function as an inhibitor. . 2 The concentration of ruthenium chloride is 1×10 ^-4 mol/l ~
5×10 ^-2 mol/l. The closed circulation absorption refrigerator according to claim 1. 3. The closed circulation absorption refrigerator according to claim 1, wherein the lithium bromide aqueous solution contains ruthenium chloride, an alkali metal hydroxide, and octyl alcohol.