JPS60118785A - Absorbing solution for absorption refrigerator - Google Patents

Abstract

PURPOSE:The titled absorbing solution, containing lithium bromide as an absorbent and methanol as a refrigerant, capable of suppressing the content of moisture to a minor amount, having a high coefficient of performance, improved handleability, and capable of providing air cooling of absorbers and condensers and generating low temperatures. CONSTITUTION:An absorbing solution containing lithium bromide as an absorbent, methanol as a refrigerant and <=1.5wt%, preferably <=1.0wt% moisture. An organic corrosion inhibitor, e.g. tolyltriazole, benztriazole, etc. having no oxidizing action in 50-5,000ppm concentration is preferably added as a corrosion inhibitor.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an absorption liquid used in an absorption refrigerator, and more particularly to an absorption liquid composition using lithium bromide (Lj-Br) as an absorbent and methanol as a refrigerant.

Absorption refrigerators are used for air temperature control and refrigeration in air-conditioning and heating systems, and use the latent heat of evaporation when a refrigerant liquid evaporates to generate low temperatures. This is to maintain the low temperature.

The structure of the absorption refrigerator is as shown in FIG. 1, and the main equipment includes a regenerator 1, a condenser 2, an absorber 3, an evaporator 4, and a heat exchanger 5. The regenerator 1 heats the absorption liquid using an external heat source (petroleum fuel, city gas, steam, exhaust gas, etc.), evaporates the refrigerant, and concentrates the absorption liquid. Here, the absorption liquid becomes a concentrated liquid. The condenser 2 cools and liquefies the refrigerant vapor separated by evaporation from the stopper 1. In the absorber 3, the concentrated liquid sent from the regenerator 1 absorbs the refrigerant vapor evaporated in the evaporator 4. Here, the absorption liquid becomes a dilute liquid. The absorber 3 is cooled with external cooling water because the temperature rises due to heat of condensation and heat of mixing. In the evaporator 4, the refrigerant sent from the condenser 2 is evaporated, and the refrigerant is evaporated.
It generates a low-temperature cold liquid (heating medium) using latent heat. The heat exchanger 5 exchanges heat between the absorption liquid (liquid A) and the absorption liquid (dilute liquid).

In these components, the regenerator 1 is heated by an external heat source, the absorber 3 and the condenser 2 are usually cooled with cooling water, and a cold liquid is generated in the evaporator 4. On the other hand, the absorption liquid goes in the order of regenerator → absorption stagnation → stopper, the refrigerant goes in the order of regenerator → condenser → evaporator door absorber → stopper, and external cooling water goes in the order of absorber → absorber → stopper. It is then sent to the condenser.

By constantly performing this operation, a continuous refrigeration function is achieved. In the absorption liquid used in such an absorption refrigerator, it is necessary that the solubility of the absorbent is high, the vapor pressure drop is large, and the crystallization temperature of the absorbent is low. Further, it is desired that the refrigerant has a large latent heat of vaporization.

In view of this, absorption liquids conventionally used in absorption refrigerators typically use water as a refrigerant and lithium halide such as Li or Br as an absorbent. Currently, this 1Br-water-based absorption liquid is used in almost all absorption refrigerators for air conditioning such as heating and cooling. This Li
Br-water-based absorption liquid has a large coefficient of performance due to the large latent heat of vaporization of water, a large vapor pressure drop of the absorption liquid, and has low viscosity and relatively low specific gravity, making it easy to handle. It has excellent properties as however,
(1) The absorber and condenser cannot be air-cooled on the refrigeration cycle, (2) The freezing temperature of water is 0°C, so it is 0°C.
There are disadvantages such as the inability to generate lower temperatures, but these are also the reasons why absorption refrigerators are used to increase head circumference. Therefore, in order to adapt absorption refrigerators to new areas, a high-performance absorption liquid other than the Lj-Br-water system is required. On the other hand, as absorption liquids other than L-'1Br-water systems, absorption liquids using ammonia as a refrigerant and water as an absorbent,
There are also known absorption liquids that use a hydrocarbon containing fluorine atoms as a refrigerant and absorb this refrigerant as an absorbent.

However, the toxicity of ammonia-based absorption liquids is a problem in use, and the coefficient of performance of hydrocarbon-based absorption liquids containing fluorine atoms is extremely small, and the performance of both is significantly inferior to that of LiBr-water-based absorption liquids. That is clear. In this way, even if other absorption liquids are included, an absorption liquid that satisfies all the points that overcomes the drawbacks of lithium bromide-water absorption liquid and enables expansion of the application field of absorption refrigerators has not yet been found. Not yet.

The present invention was discovered by the present inventors in view of the above, and consists of using LiBr as an absorbent and methanol as a refrigerant, and reducing the water content in a solution in which both are mixed to 1.5 wt%.
Hereinafter, by using an absorbing liquid whose content is desirably 1.0 wt% or less, a large coefficient of performance and good handling properties can be obtained, and the absorber and coagulation R? 1- Make it possible to air-cool the J unit and generate low temperatures below 0°C, TJ:L
The object of the present invention is to provide an absorption liquid for an absorption refrigerator that can be applied to a new field of absorption refrigerators, where it is difficult to use a Br-water-based absorption liquid.

Hereinafter, the configuration of the present invention will be explained in detail. Methanol has a large latent heat of vaporization and has a large coefficient of performance when used as a refrigerant for absorption liquid. In addition, since the solubility of Lj-Br is high and the vapor pressure drop F is also large, the Lj-Br-methanol absorption liquid has the following excellent characteristics, which are advantages that the LiBr-water-based absorption liquid does not have. This makes it possible to apply absorption refrigerators to new fields.

(1) It is possible to air-cool the absorber and condenser in the refrigeration cycle. (No water cooling equipment such as a cooling hoe is required, simplifying the installation time.) (2) 0°C
It is possible to generate the following low temperatures: (It can also be applied to the cooling field.) (3) Since the vapor pressure of the refrigerant is high, it is possible to make the absorber and evaporator more compact. (The heat transfer surface in the absorber and evaporator can be made smaller.) However, conventional L I
B r-methanol absorption liquid is about 35 to 5 Q of absorption liquid.
Crystallization in the low concentration range of wt%, ie, the presence of crystallization lines near the refrigeration cycle in the Duehring diagram of the Li-Br-methanol absorption liquid, has been a major problem.

This is because the absorption liquid crystallizes at a relatively high temperature of 20 to 30°C, which makes temperature control during operation of the absorption refrigerator and measures to prevent crystallization when the operation is stopped extremely complicated.

It is known that adding a large amount of water (for example, 1Qwt% or more) to Naoto's LiBr-methanol absorption solution prevents crystallization in the low concentration range.
The vapor pressure decreases due to the addition of a large amount of water.
Since the advantages of the Br-methanol absorption liquid are significantly reduced, it cannot be said to be an appropriate improvement method.

As a result of intensive research on LiBr-methanol absorption liquid, the present inventors found that the crystallized substance in the low concentration range is not a crystal of T'l-1 buttock, but a methanolated product of Lj-Br, and that LiBr-methanol The amount of water in the absorption liquid is 1.5
It was revealed that crystallization does not occur in the low concentration range if the concentration is below wt%. That is, the water content in the absorption liquid is 1.5
It is important to keep it below wt% to prevent crystallization in the low concentration range.
It has been discovered that the absorption liquid can fully utilize the advantages of the j-Br-methanol absorption liquid.

Figure 2 shows LiB in the Lj-Br-methanol absorption liquid.
The crystalline folding line of the methanol compound of r is shown. The amount of water in the absorption liquid is 1. The crystallization temperature of the absorption liquid increases as gw't increases from 1.5wt% to 2.0wt%, and especially at 2.0wt%, the absorption liquid concentration is 38 to 45 wt%.
The crystallization temperature is about 28 to 80'C, and crystallization occurs at normal room temperature when the operation is stopped. On the other hand, it has been found that when the water content in the absorption liquid is 1.0 wt % or less, crystallization of the absorption liquid in a low concentration range does not occur at a temperature of 0'C or higher.

Furthermore, although the corrosiveness of the L I B r-methanol absorption liquid is originally extremely low, it may cause extremely small needles (for example, Q, lWl.

%) of moisture may be present in the absorption liquid, and the corrosivity of the equipment material due to this small amount also becomes a problem when long-term maintenance-free operation is required.

Conventionally, inorganic inhibitors such as lithium molybdate, lithium chromate, and lithium nitrate have been used as corrosion inhibitors in LiBr-aqueous absorption liquids, but these all have strong oxidizing effects and cause methanol to oxidize and decompose, resulting in L
Cannot be used for 1Br-methanol absorption. For this reason, in the present invention, organic anticorrosives such as tolyltriazole and benzotriazole, which do not have oxidizing effects, are added at 50 to 50%
By adding it to the absorbing liquid at a concentration of 0.00 ppm, corrosion caused by moisture can be suppressed.

Next, Examples and comparative examples will be described. 1. Examples and comparative examples relating to the cold liquid generation function are based on the following conditions.

Refrigeration cycle single effect Evaporator cooling temperature for air conditioning: 5°C Knee 5°C for freezing Absorption liquid concentration difference: 5-7wt% (Difference in concentration between concentrated and dilute solutions) Absorber and condenser temperatures are shown in Table 1.

Basal area coefficient Based on theoretical calculations based on physical property values regarding vapor pressure, latent heat, specific heat, and heat of mixing of the absorption liquid. The heat loss is 10% and the heat exchange rate is 70%.

Comparative Example] This example is a typical example applied to air conditioning such as heating and cooling.
Experiments were conducted using a lithium bromide-water absorption liquid under the conditions shown in Table 2. The evaporator temperature is 5°C, which means 15
Cold air for air conditioning at °C was obtained.

The base area coefficient was 0.675. The air conditioning cycle was as shown by A-B-C-D in FIG.

Comparative Example 2 An experiment was conducted under the conditions shown in Table 2 using a lithium bromide-water absorption liquid. Since the absorber temperature is as high as 50'' due to air cooling, the freezing cycle Δ'-B'-C'-
A crystallization line of lithium bromide was present in D', and the freezing cycle could not be achieved. 1 Example 1 This example is an example applied to air conditioning such as air conditioning and heating, and experiments were conducted under the conditions shown in Table 2 using a lithium bromide-methanol absorption liquid. Note that the moisture content was Q, 5wi·%. Evaporator? i1? The L degree was 5°C, and a cold air of 15"G for air conditioning was obtained.The base area coefficient was 0.610, which was comparable to that of Comparative Example 1.The air conditioning cycle was 2
It was as shown by A'-B'-C'-1)' in the figure.

Example 2 This example is applied to air conditioning such as heating and cooling, and experiments were conducted under the conditions shown in Table 2 using a lithium bromide-methanol absorption liquid. Note that the water content was Q, 5 wt%.

The evaporator temperature was 5°C as in Comparative Example 1 and Example 1, and cold air of 15°C was obtained for air conditioning. The coefficient of performance is 0.651, and Comparative Examples 1 and 1, which are representative examples of the conventional type,
It was comparable in bite. The air conditioning cycle was as shown by A-B-C-D in FIG.

Example 3 This example is applied to refrigeration that requires a low temperature of 0'C or less, and experiments were conducted under the conditions shown in Table 2 using a lithium bromide-methanol absorption liquid. In addition, moisture content is 0.5%
Met. The temperature in the evaporator 81 is -5°C, dust, 0 to -2
°C plines were obtained. The coefficient of performance was 0.623, which was comparable to Comparative Example 1. The refrigeration cycle was as shown in Table 2 by A"-B"-C"-D". Note that by increasing the concentration of the absorption liquid (concentrated liquid, diluted liquid), it is possible to generate a lower temperature.

(Left below) Next, we will show an example of an experiment related to the anticorrosive effect of an organic anticorrosive agent.

Experimental Example Approximately 2000 ) Ir in methanol lithium bromide solution
.

A corrosion test was conducted using a corrosion test piece of 5s41 common steel in a vacuum at 150°C. The results are shown in Table 3, and compared to the case without anticorrosion agent, the corrosion rate was 10 to 2
We confirmed that it was reduced to 0%.

However, formaldehyde was detected in the lithium molybdate additive solution, so although the corrosion prevention effect was recognized, the absorption solution for absorption water coolers and heaters was
It was confirmed that it is not suitable as an additive.

As explained in 1-1 below, in an absorption liquid in which Lj-13r is used as an absorbent and methanol is used as a refrigerant, and the water content in the absorption liquid is 1,5 wt% or less, LiBr-methanol has been conventionally used. The problem of crystallization in the low concentration range of the absorption liquid, which was a problem with absorption liquid, has been eliminated, and by taking advantage of the characteristics of using methanol as a refrigerant, the absorber and condenser are air-cooled, eliminating the need for water cooling equipment such as a cooling tower. Technology that contributes to a significant expansion of the range of application of absorption refrigerators, such as generation of low temperatures below 0°C, and miniaturization of the transmission surface in absorbers and condensers due to the large refrigerant vapor. It is extremely useful as a

In addition, absorption chiller/heaters are required to be maintenance-free for long periods of time, and corrosion within the system is extremely undesirable as it can lead to a decrease in refrigeration capacity due to the accumulation of hydrogen gas and leakage of liquid from piping. It is a phenomenon. Therefore, in order to realize a water chiller/heater that takes advantage of the characteristics of methanol refrigerant, it is extremely beneficial to use the LiBr-methanol absorption liquid containing the organic anticorrosive agent shown in the present invention.

[Brief explanation of drawings]

Figure 1 is a basic configuration diagram of an absorption refrigerator, Figure 2 is a LiB
The Dueling diagram of r-methanol absorption af, and FIG. 3 is the Dueling diagram of the LiBr-water absorption liquid. l... Regenerator, 2... Condenser, 3... Absorber, 4...
・Evaporator, 5 ・Heat exchanger Applicant: Kawasaki Heavy Industries, Ltd.

Claims (1)

[Claims] l An absorption liquid for an absorption refrigerator comprising lithium bromide, methanol, and 1.5 wt% or less of water. 2. An absorption liquid for an absorption refrigerator consisting of lithium bromide, methanol, 1.5 wt% or less of water, and an organic anticorrosive agent of 50 to 5000 pI)m.