JP4698995B2 - How to eliminate overcooling of regenerator - Google Patents

Description

  The present invention relates to a method for eliminating supercooling of a regenerator, and in particular, to a method for eliminating supercooling of a regenerator when a pure alcohol, an alcohol mixture, or a mixture of alcohol and water is used as a regenerator. .

  Alcohol is a substance that is suitable for a cold storage agent in terms of solidification temperature, heat capacity, etc., and is economically inexpensive. Therefore, it is considered to be very effective to use as a cold storage agent.

  However, alcohol has a property that viscosity increases with a decrease in temperature due to cooling and eventually becomes glassy without being crystallized. There is a problem that it is difficult.

  Conventionally, as a technique using alcohol as a regenerator, for example, Patent Document 1 discloses a technique for promoting the growth of microcrystals in the cooling process of an aqueous alcohol solution. Specifically, among the mixtures that generate eutectic substances in a multi-component system, a method of forming a solid-liquid coexisting phase by using a mixture that performs equiaxed crystal growth as a regenerator and cooling the regenerator. Specifically, it is shown that an ethanol aqueous solution or a methanol aqueous solution is specifically used as the cold storage agent.

  However, this technique only examines the promotion of the growth of fine seed crystals of the regenerator, and does not solve the problem of supercooling that easily occurs when alcohol is used as the regenerator.

  In addition, although a medium does not contain alcohol, the following is mentioned as a technique which added the seed crystal to the cool storage agent as a supercooling prevention agent. For example, Patent Document 2 discloses a regenerator composed of water, freon, and fine zeolite, and as a substance that forms the core of clathrate generation in order to prevent overcooling and to quickly generate gas clathrate. The addition of fine zeolite is disclosed.

  Patent Document 3 discloses a cold storage agent that is composed of a guest agent and a host agent and generates a clathrate by cooling, and is added with a Group 2 metal element as a supercooling prevention agent. In addition, Freon R11, Freon R12, and Freon R21 are disclosed as guest agents, water as a host agent, and Group 2, metal elements such as Fe, Zn, and Cu as supercooling inhibitors. However, these techniques do not solve the above problem when alcohol is used as a cold storage agent.

As a method for eliminating supercooling when the alcohol is used as a cold storage agent, it may be possible to apply physical vibration such as stirring, but this is not preferable because it leads to complication of the cold storage device and an increase in manufacturing cost.
JP 2003-14353 A JP-A 61-145274 Japanese Patent Laid-Open No. 1-153785

  The present invention has been made in view of the above circumstances, and its purpose is to make the apparatus more complex when a cold storage agent is used, particularly when pure alcohol, an alcohol mixture, or a mixture of alcohol and water is used as the cold storage agent. Another object of the present invention is to provide a method for preventing overcooling of the regenerator without causing an increase in manufacturing cost.

  The method for eliminating supercooling of a regenerator according to the present invention is to add a powdery solid substance to the regenerator in advance when using pure alcohol, an alcohol mixture, or a mixture of alcohol and water as a regenerator. Has characteristics.

  As the powdery solid substance, it is preferable to use activated carbon. When the activated carbon is added, it is preferable to add 0.001 g or more of activated carbon to 1 g of the regenerator.

  Moreover, the method for eliminating supercooling of the regenerator of the present invention is more effective when the alcohol is ethanol.

  According to the method of the present invention, it is possible to eliminate the overcooling of the regenerator that is disadvantageous in terms of heat efficiency without complicating the structure of the regenerator and without increasing the cost. It can contribute to the generalization of a cold storage agent.

  When the present inventors use, as a regenerator, in particular, a pure alcohol, an alcohol mixture, or a mixture of alcohol and water (hereinafter sometimes collectively referred to as “alcohols”), the regenerator We conducted intensive research to realize a method to prevent overcooling. As a result, the inventors have found that a powdered solid substance may be added to the alcohols in advance, and have arrived at the present invention.

  In this way, by adding a powdery solid substance in advance to the regenerator, the solid substance acts as a seed crystal, that is, the solid substance in the solution serves as a nucleus of crystal growth and promotes crystallization. Cooling is eliminated.

  Examples of the powdery solid substance include sea sand, NaCl, activated carbon, and the like. Among these, addition of activated carbon is preferable because crystallization of the alcohols can be promoted.

  The present invention is not limited to the size of the powdery solid substance, but in order to promote appropriate crystallization of the alcohols by appropriately dispersing in a regenerator, the average particle size is about 10 μm or more. It is preferable to use a solid material of 500 μm or less. In this case, the average particle size can be measured using a laser diffraction method particle size distribution measuring apparatus ["LMS-24", light source: semiconductor laser (wavelength: 670 nm)] manufactured by Seishin Enterprise Co., Ltd. . In the measurement, ethanol or the like can be used as a dispersant.

  Further, the present invention does not prescribe the addition amount of the powdery solid substance to pure alcohol, an alcohol mixture, or a mixture of alcohol and water, and the addition amount can be appropriately determined. In the case of using activated carbon as the solid substance, it is preferable to add 0.001 g or more with respect to 1 g of the regenerator because the overcooling can be reliably eliminated. More preferably, it is 0.005 g or more. On the other hand, there is no problem in eliminating supercooling even if the amount of activated carbon added to the cold storage agent is large, but considering the heat storage capacity per volume, it is preferable to make it 0.3 g or less with respect to 1 g of the cold storage agent.

  In the present invention, pure alcohol, an alcohol mixture, or a mixture of alcohol and water is used as a medium for the regenerator, but is not limited to the type of the alcohol, and examples thereof include ethanol, methanol, and 1-propanol. Pure alcohol can be commercially available, and examples of the alcohol mixture include ethanol and methanol, ethanol and 1-propanol, and methanol and 1-propanol. The ratio of various alcohols in the alcohol mixture and the ratio of alcohol to water are not limited.

  In addition, while acting sufficiently as a regenerator, the effect of the present invention appears remarkably when ethanol is used as alcohol, when pure ethanol is used, or when ethanol (50% by volume or more) and methanol are used. When using a mixture (less than 50% by volume), or when using a mixture of ethanol with a slight addition of 1-propanol, or using a mixture of ethanol (50% by volume or more) and water (less than 50% by volume) The case where it uses is mentioned.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. It is also possible to implement, and they are all included in the technical scope of the present invention.

  In this example, a solidification experiment was performed using an apparatus as schematically shown in FIG. In this example, commercially available pure ethanol satisfying the following requirements (a) to (e) was used as the cold storage agent. The pure ethanol is a special grade reagent manufactured by Wako Pure Chemical Industries, Ltd., and was used as it was in this example without purification. The properties and purity of this pure ethanol are shown below.

<Conditions for selecting regenerator>
(A) The latent heat due to solidification can be used in the range of the freezing point in the range of -145 to -120 ° C.
(B) The heat capacity (density x latent heat of solidification) is large.
(C) The boiling point is 20 ° C. or higher.
(D) It must be safe with low explosiveness and flammability.
(E) Be inexpensive.

<Characteristics and purity of pure ethanol>
Substance amount: 46.07 g / mol
Liquid density: 795 kg / m ³
Freezing point: -117.3 ° C
Solidification latent heat: 109 kJ / kg
Heat capacity: 86594 kJ / m ³
Purity: 99.5 v / v% or more

The experiment was specifically performed according to the following procedure.
(I) Put 1.00 g of the sample (powdered solid substance shown in Table 1) 2 in a test tube (PIREX glass container) 1, insert the thermocouple 3, and then plug. The thermocouple 3 is installed approximately at the center of the liquid phase of the sample 2.
(Ii) Liquid nitrogen 6 is put into the Dewar bottle 5.
(Iii) The test tube 1 is placed in a beaker 8 filled with expanded polystyrene 7, and the beaker 8 is further placed in the Dewar 5 to cool the sample 1. At this time, stirring is not performed.
(Iv) When near the freezing point, the sample is cooled at a cooling rate of 1 to 2 ° C./min.
(V) Record the measured sample temperature in the data logger 9 (sampling rate: 2 points / s).

  As a comparative example, a similar experiment was performed when no powdered solid substance was added to the cold storage agent. Such an experiment was repeated three times, and when the regenerator became glassy during cooling, it was judged that supercooling was not eliminated, and when solid crystals were formed by cooling, it was judged that supercooling was eliminated. . The results are shown in Table 1.

  In addition, the following activated carbon, sea sand, or NaCl was used for the powdery solid substance added as a seed crystal.

<Activated carbon>
Manufacturer: Kuraray Chemical Co., Ltd. Product name: Kuraray Coal Activated Carbon 4GS (pellet form)
Shape and particle size: 4-6 mesh size in pellet form (3.00-4.75mm)
Particle size (4-6 mesh): 95% or more Packing density: 0.40-0.45 g / mL
Loss on drying: 5% or less Benzene adsorption power: 36% or more In this example, the pelletized activated carbon was pulverized for 10 minutes using a mortar.

<Sea sand>
Manufacturer: Wako Pure Chemical Industries, Ltd. Sea sand (methanol washed product) Wako Pure Chemical Industries, Ltd. Product No .: 197-11655
Particle size: 425-850 μm (20-35 mesh)
In this example, a product washed with ethanol and dried was used.

<NaCl>
Manufacturer: Kanto Chemical Co., Ltd. Product name: sodium chloride
Product number: 37144
Grade: Special reagent grade Concentration: (Min) 99.9%
In this example, the commercially available NaCl was used as it was.

  The results of Table 1 are considered below. No. As shown in Fig. 1, the viscosity increases when the liquid ethanol is cooled by using the cold heat of liquid nitrogen, but it reaches the supercooled state without solidifying even after the solidification temperature, resulting in a colorless and transparent glass. . No. In No. 1, no crystallization occurred even when cooled to about -150 ° C.

  No. Nos. 2 to 5 are examples in which a powdery solid substance was previously added as a seed crystal. In No. 2, activated carbon, no. 3 is sea sand, no. In 4 and 5, NaCl was added.

  No. In No. 2, 0.10 g of powdered activated carbon was added in advance to 1 g of ethanol to conduct a solidification experiment. As a result, a supercooled state did not appear, white solid crystals were formed, and the temperature at the time of solidification almost coincided with the value shown in the literature (“14303 Chemical Products” (2003) Chemical Industry Daily). It was also found that solid crystals were formed in all three experiments and the reproducibility was good.

  No. For No. 3, 0.50 g of powdery sea sand was added in advance to 1 g of ethanol to conduct a solidification experiment. As a result, twice of the three experiments, no supercooled state appeared, white solid crystals formed, and the solidification temperature almost agreed with the literature value. However, one out of three times could not prevent overcooling and became a glassy solid.

  No. No. 4 is an example in which 0.05 g of powdered NaCl is added to 1 g of ethanol. 5 is an example in which 0.10 g of powdered NaCl is added to 1 g of ethanol. In these examples, a supercooled state does not appear once in three experiments, and a white solid crystal is formed. did. However, 2 times out of 3 times could not prevent overcooling and became a glassy solid.

  These No. From the results of 2 to 5, it can be seen that when activated carbon is added in advance as a powdery solid substance, the supercooling of the regenerator can be surely eliminated.

  Next, the amount of the activated carbon added was changed, and the influence of the added amount on the supercooling of the regenerator was examined. In the experiment, the coagulation experiment was performed by changing the amount of activated carbon added to 0.050 g, 0.010 g, 0.0050 g, 0.0010 g, and 0.0005 g with respect to 1 g of ethanol. As a result, when 0.050 g, 0.010 g, 0.0050 g, and 0.0010 g of activated carbon were added to 1 g of ethanol, a supercooled state did not appear and white solid crystals were generated. The reproducibility was also good, and overcooling could be prevented in all three experiments or two out of three experiments (Nos. 6 to 9 in Table 1).

  On the other hand, when 0.0005 g of powdered activated carbon was added to 1 g of ethanol and a solidification experiment was conducted (No. 10), supercooling could not be prevented in all three experiments, and colorless. It became a transparent glassy solid.

  From these experimental results, in particular, by adding 0.001 g or more (more preferably 0.005 g or more) of powdered activated carbon to 1 g of ethanol, the supercooling can be surely eliminated, and crystallization can be achieved. It turns out that it is promoted.

  In addition, as a graph which shows the temperature change at the time of cooling, the thing at the time of adding 0.005g of activated carbon to ethanol is shown in FIG. As shown in FIG. 2, it can be seen that the regenerator reaches a solid-liquid equilibrium state at −116.6 ° C. after passing through the supercooling temperature. When the temperature was further decreased from −116.6 ° C. to about −120 ° C., the sample was visually observed, and confirmed to be solidified in a slightly white crystal state. From this result, it is understood that the ethanol overcooling can be eliminated by adding 0.005 g of activated carbon.

It is sectional drawing which showed typically the cooling experiment apparatus used in the Example. It is a graph which shows a temperature change when (ethanol + activated carbon 0.005g) is cooled.

Explanation of symbols

1 Test tube 2 Sample (powdered solid substance)
3 Thermocouple 4 Stopper 5 Dewar Bottle 6 Liquid Nitrogen 7 Styrofoam 8 Beaker 9 Data Logger

Claims (2)

A mixture of ethanol and methanol in which ethanol is 50% by volume or more, a mixture of ethanol and water in which ethanol is 50% by volume or more, or when using pure ethanol as a regenerator A method for eliminating supercooling of a regenerator , wherein 0.005 g or more of powdered activated carbon is added in advance to 1 g of the agent.   The method for eliminating supercooling of a cold storage agent according to claim 1, wherein the freezing point of the cold storage agent is -145 ° C to -120 ° C.

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