JP3534587B2 - Cold storage agent, cold storage body containing the cold storage agent, cold storage device using the cold storage body, cold storage method, and BOG reliquefaction method - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to liquefied natural gas (L
Regenerator used to store cold heat of extremely low temperature substances such as NG), regenerator filled with regenerant in pressure vessel, regenerator is filled in the regenerator, and fluid is circulated in the regenerator. The present invention relates to a cold storage device, a cold storage method, and a reliquefaction method for boil-off gas (abbreviated as BOG) using the same.

[0002]

2. Description of the Related Art There is known a technique of storing cold heat such as LNG and utilizing it when necessary. JP-A-60-9830
No. 0 and Japanese Patent Laid-Open No. 63-203997 disclose a technique in which isopentane, isobutane or isobutane having a low freezing point and a high boiling point is used as a regenerator, and the regenerator is circulated through a heat exchanger for use. There is. However, with these regenerators, the regenerator does not solidify even when heat is exchanged with LNG, so only the sensible heat can be used by the regenerator, and a large regenerator is required to store a large amount of LNG cold. Also, n-
Some of them, like pentane, can use sensible heat and latent heat by solidifying, but the heat transfer between the cooling pipe and the solidified n-pentane is poor, and there is no problem because the solidified n-pentane layer is thin in the initial stage. However, there is a problem that heat transfer becomes worse as the solid phase grows. JP-A-3-236588 discloses that
A eutectic mixture of ethanol / water is used as a regenerator, and it is installed inside the regenerator tank filled with this regenerator so that the pipe passes through it. A method of liquefying is disclosed. By using the eutectic mixture as the regenerator, the regenerator can utilize not only sensible heat but also latent heat during crystallization of the eutectic mixture for regenerator. However, the freezing point of the ethanol / water mixture is high (-114.2 ° C for pure ethanol), and -1
It is not suitable as a regenerator used to store the cold heat of a substance at an extremely low temperature of 20 ° C or lower. Further, the heat transfer efficiency of the above regenerator becomes extremely poor when water adheres to the surface of the cooling pipe as ice.

[0003]

SUMMARY OF THE INVENTION The object of the present invention is -1.
A cold storage agent having a large amount of cold storage per unit mass and high heat transfer performance, which can be used to store cold heat of a substance having an extremely low temperature of 00 ° C. or lower, preferably −120 ° C. or lower, a cold storage body using the same, a cold storage body A cold storage device for filling and using the same, and a cold storage method thereof.

[0004]

As a result of intensive studies, the present inventors have found that HFC-134a, HFC-23, and HFC-
A mixture of 32, ethane, etc. solidifies at -100 ° C or below.
Due to the phase change of melting, it is possible to efficiently store a large amount of cold and the heat transfer efficiency does not significantly decrease,
In addition, the cold storage agent has almost no corrosiveness with respect to metals and can be used for a long period of time by enclosing it in a metal pressure container, and by using the pressure container as a pellet, it can be used by filling it into a tank. The present invention has been completed and the present invention has been completed.

That is, the first aspect of the present invention is HFC-134.
a and a mixture of HFC-23 and HFC-134
a / HFC-23 mole fraction 0.8-0.4 / 0.2
Is about 0.6, and the mixture forms a eutectic and relates to a cold storage agent capable of storing cold by a phase change at -100 ° C or lower.
A second aspect of the present invention comprises a mixture of HFC-134a and HFC-32, wherein the HFC-134a / HFC-32 mole fraction is 0.8 to 0.5 / 0.2 to 0.5, and the mixture is Relates to a cold storage agent which forms a eutectic and can store cold by a phase change at -100 ° C or lower. The third aspect of the present invention is HF.
The present invention relates to a cold storage agent which is composed of a mixture of C-134a, HFC-23 and HFC-32, the mixture forms a eutectic, and can store cold by a phase change at -100 ° C or lower. With these, a cold storage agent that can be used at -100 ° C or lower and that utilizes a phase change between liquid and solid to provide a large amount of cold storage per unit mass and high heat transfer performance is provided.

A fourth aspect of the present invention relates to a regenerator characterized in that any of the regenerator agents according to any one of the first to third aspects of the present invention is enclosed in a pressure resistant container. With these, the regenerator can be used in a shape corresponding to the pellets, and thus the pellets can be filled and used.

A fifth aspect of the present invention relates to a regenerator which is filled with the regenerator according to the fourth aspect of the invention and which comprises a regenerator having a port for allowing a fluid to flow therethrough. The sixth aspect of the present invention is
A cold storage tank having any one of the cold storage agents according to 1 to 3 of the present invention or the cold storage element according to 4 of the present invention and having a circulation port for circulating a fluid, the cold storage agent or the cold storage element and a fluid. The present invention relates to a cool storage device characterized in that and exchange heat via a partition wall. Thereby, the regenerator can be used in a form filled with the regenerator or the regenerator.

A seventh aspect of the present invention is to cool the cold storage tank according to the fifth or sixth aspect of the present invention by causing a fluid having a temperature lower than the freezing point of the cold storage agent filled in the cold storage tank to flow therethrough. The present invention relates to a cold storage method characterized by: An eighth aspect of the present invention is the cool storage method according to the seventh aspect of the present invention,
In a cold storage tank that uses LNG for low temperature fluid,
The present invention relates to a method for reliquefying BOG, which comprises liquefying BOG by circulating OG. With this, a large amount of cold heat can be stored in the cold storage tank by circulating a fluid cooled to a low temperature such as LNG in the cold storage tank, and a high temperature fluid such as BOG is circulated from the outside. Can be cooled. In the present invention, the fluid includes liquid and gas.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The cold storage agent of the present invention is a cold storage agent capable of cold storage at −100 ° C. or lower, and preferably suitable for use at −120 ° C. or lower. The freezing point of the regenerator is −100 ° C. or lower, and it is a medium that stores cold heat as sensible heat and latent heat of solidification of the regenerator, and when it is used by being enclosed inside a pressure vessel, it exceeds −100 ° C. to room temperature. It is in a liquid state at temperature and has high heat transfer performance even during solidification. By storing cold heat in the form of latent heat as heat of fusion at the freezing point rather than using only sensible heat of liquid or solid, the amount of cold storage per unit weight of the cold storage agent can be increased. Therefore, for example, -16
If you want to maximize the amount of cold storage at 0 ℃, the freezing point is -1
Choose a regenerator that gives a temperature of 60 ° C, and therefore -1
In the temperature range over 60 ° C., the regenerator stores liquid in a liquid state, solidifies at −160 ° C., and stores as latent heat.
Storing heat by sensible heat in a solid state at a temperature lower than ℃.

As such a low temperature regenerator, HFC-
134a (CH ₂ FCF ₃ ), HFC-23 (CH
_{F 3), HFC-32 (} CH 2 F 2), was found to meet ethane, propane, butane and one or more of the mixture necessary condition pentane. In particular, HFC-134a
/ HFC-23 mixture with a molar fraction of 0.8-
The mixture of 0.4 / 0.2 to 0.6 contains a eutectic point and thus exhibits a melting point drop, and most of the regenerator can maintain a liquid state up to about -160 ° C. HFC-134a /
It is a mixture of HFC-32 and the molar fraction of each component is 0.8-
The same applies to a mixture having a ratio of 0.5 / 0.2 to 0.5, and most of the cool storage agents can maintain a liquid state up to about -160 ° C. Similarly, HFC-134a to HFC-2
Those containing 3 and HFC-32 also contained a eutectic point, exhibited a melting point decrease, and can be used as a regenerator. Ethane, propane, butane, pentane and mixtures thereof have a high solubility in HFC-134a and are in a liquid state at a temperature of more than -100 ° C to room temperature.
Form a solid solution at -180 ° C. Therefore, the cold storage agent of the present invention is -100 ° C or lower, preferably -120 ° C to -20 ° C.
It can be used at about 0 ° C.

The regenerator of the present invention is a single component, preferably a mixture. In the case of the mixture, the vapor pressure and the flammability can be lowered as compared with the case where each component is a pure substance. It is possible to make them non-flammable. Further, the regenerator of the present invention has almost no corrosiveness to metals and can be used for a long period of time by enclosing it in a pressure container made of metal. In addition, the cold storage agent of the present invention has low ozone depletion properties and high safety even if it leaks to the outside.

The regenerator of the present invention is a regenerator containing the above-mentioned regenerator inside a pressure vessel. Withstand pressure at 40 ° C, for example, 10 kgf / cm ² or more, 30 kgf / cm ² or more, 50 kgf / cm ²
It is possible to make various things such as the above, and a cool storage agent having a composition suitable for this can be selected. The pressure vessel has a disk-like shape, a spherical shape, a columnar shape, an annular shape, a circular tube shape, a cubic shape, a rectangular parallelepiped shape, a plate shape, or the like, and can be used by filling it into a cold storage tank as pellets. The size of the pressure-resistant container can be selected depending on the usage condition. For example, in the case of a disc, a sphere, a cylinder, or a cylinder, the diameter is 1 to 10
cm-shaped, disk-shaped, thin annular, cubic or rectangular parallelepiped-shaped, and plate-shaped, those with a thickness of 0.5-10 cm are cylindrical, long cylindrical, plate-shaped, long 1 to 1
An example is a 200 cm one. The regenerator of the present invention is a spherical one that is easy to perform a filling operation, a disc-like one can easily take a large porosity, a fluid easily flows around the regenerator, and a rectangular solid has a filling density of high,
The tubular shape can be characterized by a large non-surface area and a low flow resistance.

The material and wall thickness of the pressure-resistant container are selected according to the usage conditions. However, it is repeatedly cooled and heated between a low temperature such as −100 ° C. or lower and a normal temperature, and it can be used for a long period of time, preferably several years or more.
Further, from the viewpoint of cold storage and reuse of the cold heat stored, it is preferable that the thermal conductivity is good. As the material, for example, aluminum, aluminum alloy, copper, copper-nickel alloy,
Chrome-nickel alloy, nickel, iron, stainless steel,
Examples include austenitic stainless steel, titanium, and titanium alloys. The surface of the pressure-resistant container may be coated with glass, ceramic, graphite or the like in order to increase corrosion resistance. Further, the pressure-resistant container may have a pattern of irregularities or the like on its surface, may be magnetized, or may be provided with an oxide film, if necessary. The cool storage agent is enclosed in the pressure resistant container. The cold storage agent may be cooled to be in a liquid state and sealed, or the pressure resistant container may be cooled and sealed with gas. The amount of the cool storage agent enclosed in the pressure container is determined based on the expansion rate of the cool storage agent. If the coefficient of expansion during solidification is large, a safety factor of 80% of the capacity of the container may be expected. The mouth when the cold storage agent is enclosed in the pressure resistant container can be closed by welding, screwing with a sealing mechanism, or the like. With such a structure, the regenerator of the present invention can be manufactured in a small size to a large size. Further, the regenerator of the present invention can be used in combination with other filling materials.

Next, the regenerator used in the present invention is not particularly limited because it is used by filling the regenerator with the regenerator. For example, various types such as a box, a tower, a pipe, and a sphere can be used. Formats can be used. The method of filling the regenerator is also not particularly limited, but the regenerators may be arranged and filled, or may be simply charged and used. Further, the regenerator may be partitioned by a shelf or the like and used in several stages. It is also possible to provide a pressing plate, a dispersion plate, a straightening plate, etc. at the fluid inlet or in the middle of the cold storage tank,
A support plate or the like for preventing the regenerator from falling may be provided at the bottom of the regenerator. There is no particular limitation on the size and shape of the cold storage tank. The regenerator can be used in combination of various shapes, sizes and different regenerators. For example, the fluid inlet of the cold storage tank may be filled with a material having a low freezing point or a material having a high freezing point. Furthermore, the filling section may be a fixed bed or a moving bed.

The cold storage tank may be a pressure resistant container.
The pressure when used as a pressure resistant container is reduced pressure, normal pressure, and several tens of degrees, as long as the regenerator body containing the regenerator has pressure resistance strength.
It may be one that can be used under a pressure of kgf / cm ² . The cold storage tank may be capable of stirring operation. The cold storage tank may have a heat insulating structure or may be capable of cooling and heating.

Further, the cold storage tank is a pressure resistant container, and the cold storage tank can be filled with a cold storage agent for use. The cool storage tank
For example, in a shell-and-tube heat exchanger, the shell side is filled with a regenerator, the tube side is circulated with a cold heat source such as LNG to store cold, and then a high heat source such as BOG is circulated through the BOG. Can also be liquefied.

In the present invention, heat exchange through a partition means that the regenerator or regenerator is LNG or N which is a fluid.
G or BOG means that heat exchange is performed by heat conduction across the partition wall.

The cold storage tank has circulation ports for passing a cold heat source such as LNG and a high heat source such as BOG.
If necessary, a port for charging and discharging the regenerator may be further provided.

The regenerator of the present invention fills the regenerator with the regenerator, and causes a fluid for heat exchange with the regenerator to flow through a space other than the regenerator in the regenerator. The cool storage tank is filled with a cool storage body, and a supply port is provided at one end and a discharge port is provided at the other end inside the cool storage tank, a fluid for heat exchange with the cool storage body is supplied from the supply port, and the heat-exchanged fluid is discharged from the tank. What was made possible, or by providing a serpentine or spiral pipe that passes through the cold storage tank, let the fluid that exchanges heat with the cold storage body flow through the pipe, and fill the space inside the cold storage tank outside the pipe with the cold storage body You may do it. Alternatively, the pipe may be filled with a regenerator and a fluid may be circulated to exchange heat with the outside of the pipe. The direction in which the fluid to be heat-exchanged is passed is not particularly limited, but when circulating in the upward direction, a holding plate or the like may be placed on the upper portion.

Further, the regenerator of the present invention is provided with a supply port at one end and a discharge port at the other end in the regenerator, supplies a fluid for heat exchange with the regenerator from the supply port, and exchanges the heat-exchanged fluid from the cistern. It can be discharged, and has a feature that a large amount of cold storage per unit volume can be taken and the cold storage operation is easy.

In the present invention, the fluid that is circulated in the cold storage tank may be gas, liquid, slurry, or solid such as powder. For example, L
Liquefied gases such as NG and LPG, liquefied air, low-temperature liquids such as liquefied nitrogen or their vaporized low-temperature gases, or other refrigerants such as CFC. The fluid that is circulated in the cold storage tank may be the cold heat source itself or a working fluid that has exchanged heat with the cold heat source. Generally, the fluid or working fluid that is circulated in the cold storage tank is preferably a liquid having a lower freezing point than the cold storage agent.

BOG is used as a high heat source in the cold storage tank in which the cold is stored.
BOG can be reliquefied and returned to LNG by circulating. In this way, the cold heat when LNG is paid out is stored, and the BO accumulated when LNG is not paid out
It can be used to liquefy G.

The working fluid is ethane (freezing point -18
3 ° C), hydrocarbons having 1 to 5 carbon atoms such as propane (freezing point-188 ° C) and HCFC-124 (freezing point-1
Fluorocarbons such as HCFC-22 (freezing point −160 ° C.) and the like can also be used. However, in an emergency or the like, hot water or outside air can be distributed.

In the cold accumulating agent of the present invention, the freezing point of the mixed cold accumulating agent is as shown in FIGS. 3 to 6, and effective utilization of sensible heat and latent heat during solidification for cold accumulating at −100 ° C. or lower. You can Further, in general, using a phase change at a freezing point that progresses at a constant temperature is more stable, and the amount of cold storage per unit weight of refrigerant is larger than that of sensible heat storage in a certain temperature range. Therefore, there is an advantage that a compact device is enough.

As an example of the present invention, a method for storing cold will be described below with reference to FIGS. FIG. 1 shows various regenerators in which the regenerator 1 of the present invention is enclosed in a pressure vessel 10 of various shapes. (A) is a disc-shaped regenerator. (B) is a spherical regenerator. (C) is a cylindrical regenerator. (D) is a tubular regenerator. (E) is a plate-shaped regenerator.

FIG. 2 shows a regenerator of the present invention. Regenerator 2
Is previously filled in the cold storage tank 3. A fluid having cold heat is supplied from the fluid supply port 4, exchanges heat with the regenerator 2 and is discharged from the fluid discharge port 5. Regenerator 2 filled in regenerator 3
Can be taken out from the regenerator outlet 9 if necessary. If desired, the cold storage tank 3 can be provided with a pressing plate 6, a fluid distribution plate 7, a support plate 8 and the like.

[0027]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited thereto. (Example 1) A pressure-resistant container of the example (C) of FIG. 1 was used, and a mixed liquid of HFC-134a / propane (molar fraction 0.3 / 0.7) was sealed inside to form a cylindrical shape. I made a regenerator. The dimensions are a pressure-resistant container having an outer diameter of 50 mmΦ × a length of 200 mmL and a wall thickness of 4 mmt, and the material is SUS-316.
About 70% of the internal space was filled with a mixed solution of the regenerator and hermetically sealed.
The regenerator was filled in a regenerator and was able to be used efficiently in the range from -80 ° C to a low temperature of several tens of degrees, particularly in the range of -100 ° C to the freezing point. Also, the cool storage body is 3
Even if it is used for about half a year by decreasing and increasing the temperature once a day between 0 ° C and the freezing point (about -140 ° C), the amount of cold storage decreases, the cold storage agent leaks, and the surface of the cold storage body corrodes. No cracks or the like occurred.

(Embodiment 2) Using the regenerator of FIG. 2, the regenerator obtained in Embodiment 1 has a diameter of 400 mmΦ and an effective height of 20.
It was filled in a cold storage tank having a volume of 0.25 m ³ and a volume of 0.25 m ³ , and liquefied natural gas (LNG) was circulated to the cold storage to store the cold. The results are shown in Table 1. The transfer of heat from the liquefied gas to the regenerator was good.

[0029]

[Table 1]

Example 3 Boil-off gas (BOG) of liquefied natural gas was circulated through the regenerator that had been regenerated in Example 2 to liquefy BOG to recover cold heat. That is, from the state where cold heat is transferred from the liquefied natural gas to the regenerator to store the cold heat, the temperature is -1 at a pressure of 30 kgf / cm ^2.
BOG at the level of 00 ℃ is continuously about 3 at 25 kg / hr.
By supplying to the cold storage tank for a time and passing through the layer of the cold storage body, it was possible to liquefy the entire amount of BOG by receiving cold heat from the cold storage body. According to the present invention, the cold heat of the liquefied natural gas can be stored in the regenerator and the BOG of the liquefied natural gas can be reliquefied by using the cold heat.

[0031]

INDUSTRIAL APPLICABILITY According to the present invention, cold heat of a substance at an extremely low temperature of −100 ° C. or lower, preferably −120 ° C. or lower can be stored as sensible heat and latent heat, and a large amount of cold storage per unit mass, heat transfer A high-performance regenerator, a regenerator using the regenerator, a regenerator capable of filling and using the regenerator, and a regenerator method thereof were obtained.

[Brief description of drawings]

1 shows various forms of regenerators of the present invention. (A): Disk-shaped regenerator. (B): Spherical regenerator. (C): Cylindrical regenerator. (D): Tubular regenerator. (E): Plate-shaped regenerator.

FIG. 2 shows a regenerator of the present invention.

[Fig. 3] Regenerator HFC-134a / HFC- of the present invention
23 shows a freezing point diagram of No. 23.

FIG. 4 is a regenerator HFC-134a / HFC- of the present invention.
32 shows a freezing point diagram of 32.

FIG. 5 shows a freezing point diagram of the cold storage agent HFC-134a / ethane of the present invention.

FIG. 6 shows a freezing point diagram of the cold storage agent HFC-134a / propane of the present invention.

[Explanation of symbols]

1: Cold storage agent 2: Regenerator 3: Cold storage tank 4: Fluid supply port 5: Fluid outlet 6: Press plate 7: Fluid dispersion plate 8: Support plate 9: Regenerator outlet 10: Pressure resistant container

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Haruma Asakawa 2-5-1, Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Heavy Industries, Ltd. (56) References JP-A-9-60799 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F25D 1/00-9/00

Claims (8)

(57) [Claims] 1. A mixture of HFC-134a and HFC-23, wherein the molar fraction of HFC-134a / HFC-23 is 0.8-0.4 / 0.2-0.6, and the mixture is A cold storage agent that forms crystals and can store cold by phase change at -100 ° C or lower. 2. A mixture of HFC-134a and HFC-32, wherein the HFC-134a / HFC-32 mole fraction is 0.8-0.5 / 0.2-0.5, and the mixture is A cold storage agent that forms crystals and can store cold by phase change at -100 ° C or lower. 3. HFC-134a, HFC-23 and H
Consisting of a mixture of FC-32, the mixture forming a eutectic,
Cooling agent that can store cold by phase change below 100 ℃. 4. A regenerator, comprising the pressure-resistant container filled with the regenerator according to any one of claims 1 to 3. 5. A cool storage device comprising a cool storage tank filled with the cool storage body according to claim 4 and having a port for allowing a fluid to flow therethrough. 6. A regenerator in any one of claims 1 to 3 or the regenerator according to claim 4 is filled in a regenerator having a circulation port for circulating a fluid. Alternatively, a regenerator characterized in that the regenerator and the regenerator exchange heat with a fluid via a partition wall. 7. A cold storage characterized in that the cold storage tank according to claim 5 or 6 stores a cold fluid in the cold storage tank by circulating a fluid having a temperature lower than a freezing point of the cold storage agent filled in the cold storage tank. Method. 8. The cold storage method according to claim 7 , wherein LOG is used as a low temperature fluid to cool the cold storage tank.
A method of reliquefying BOG, characterized in that the BOG is liquefied by circulating the above.