JPS629171A - He liquefying refrigerator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lid for generating and supplying liquid He used to maintain an object to be cooled at an extremely low temperature.
The present invention relates to a He liquefaction refrigeration system capable of not only maintaining cryogenic temperatures but also producing liquid He for supply and precooling objects to be cooled.

[Prior Art] In equipment that requires keeping objects to be cooled at a cryogenic temperature, such as cryogenic strength testing equipment for materials, He liquefaction refrigeration equipment is used to create a cryogenic environment. That is, in this equipment, the object to be cooled is placed in a cryogenic container, liquid He produced by a He liquefaction refrigerator is supplied to the cryogenic container, and the object to be cooled is immersed in the liquid He to maintain the cryogenic temperature. Achieve your purpose.

By the way, there is no problem if there is no need to take out the object to be cooled from inside the cryogenic container, but in the cryogenic equipment mentioned above, it is often necessary to open the cryogenic container to replace or inspect the object to be cooled, and each time In addition, not only the inside of the cryogenic container but also the He gas flow path opening into the cryogenic container is contaminated by outside air.If air is mixed into the He gas, the flow path will be damaged due to freezing of the mixed air. This may cause problems such as clogging, so once the cryogenic container is opened, it is necessary to clean the entire system of the He liquefaction refrigeration system, which requires a great deal of effort and time.

Therefore, various recondensing type He liquefaction refrigeration equipment have been proposed as a solution to the above problem (Japanese Patent Publication No. 53-22979, Japanese Patent Application Publication No. 52-6257, Japanese Patent Application Publication No. 56-138655).
By using this, contamination of the He gas flow path is prevented. That is, the recondensation type He liquefaction refrigeration system has a recondenser installed in a cryogenic container, forms a closed circuit from the He liquefaction refrigeration system to the recondenser, and flows liquid He into the closed circuit. This condenses the He gas in the cryogenic container and keeps the object to be cooled at a cryogenic temperature.
Since the He in the liquefaction refrigeration equipment flows in a closed circuit in the recondenser, even if the cryogenic container is opened, there is no risk of contact with the outside air and the He can be maintained in a clean state. .

However, in the recondensing He liquefaction refrigeration system described above, liquid He only flows through the recondenser and is not supplied into the cryogenic container. When trying to inject liquid He into the tank, there was a drawback that it was necessary to seek help from another He liquefaction refrigerator. To explain the circumstances during this time in more detail, when replacing the object to be cooled in the cryogenic container, the operation of the He liquefaction refrigeration system is temporarily stopped, the cryogenic container is heated with a heater, etc., and the liquid He in the container is replaced. Vaporize it and store it in a gas bag, etc. outside the system.Next, open the container and take out the object to be cooled, then charge a new object to be cooled.During the first operation, put the object to be cooled into the container. ) and start cryogenic operation.
At the start, liquid N2 and the like are first introduced into the container to pre-cool the container and the object to be cooled, and then liquid N2 and liquid He are replaced. At this time, liquid He is required, but the
Since the liquefaction refrigeration system does not have a liquid He supply function, liquid He must be produced and supplied by another He liquefaction refrigeration machine. The container is thus closed, and the He liquefaction refrigeration system is operated to flow liquefied He into the recondenser, thereby condensing the vaporized He in the container and maintaining the container and the object to be cooled at an extremely low temperature.

As can be understood from the above explanation, in the recondensing He liquefaction refrigerator, it is necessary to operate another He liquefaction refrigerator when starting or restarting operation of the cryogenic equipment, and it is also necessary to pre-cool the container and the objects to be cooled. A separate line had to be prepared for the operation of recovering He from a container or a container, which was a huge waste of equipment.

[Problems to be Solved by the Invention] The present invention has been completed as a result of repeated research focusing on these situations. The present invention aims to provide a recondensing type He liquefaction refrigeration device that can perform all low-temperature maintenance with one device.

[Means for Solving the Problems] The He liquefaction refrigeration system of the present invention, which achieves the above object, is a He liquefaction refrigeration system equipped with a recondensing type cryogenic container, which is installed in the high-pressure side line of the He liquefaction refrigeration system. A flow path switching mechanism is provided downstream of the Joule-Thompson valve, and the liquefied He supply destination can be switched between the recondenser provided in the cryogenic container and the liquefied He storage section in the cryogenic container. [Operation] In the recondensing type He liquefaction refrigeration system, the He gas that has been precooled in stages as described above is liquefied by passing through the Joule-Thomson valve, and then transferred to a cryogenic container. He gas is sent to a recondensing heat exchanger installed inside the container, and the inside of the cryogenic container is kept at an extremely low temperature by the latent heat of vaporization of the liquid He in the heat exchanger.
is converted to Therefore, the present inventors proposed that if this liquid He could be supplied not only as a refrigerant for the recondenser but also into the cryogenic container, it could be used as a liquid He production device during the start-up or restart period. I thought it might be possible. The present invention takes advantage of this knowledge and makes use of recondensed H
A flow path switching mechanism is provided downstream of the Joule-Thompson valve installed in the high-pressure side line of the e-liquefaction refrigeration system, and the liquid He generated in the Joule-Thompson valve is transferred to the recondensing heat exchanger and the liquid He storage section in the cryogenic container. By adopting the above configuration, it is possible to switch the flow of cold tofu to the desired direction, and during the start-up or preparation of refrigeration operation, liquid He
can be supplied and stored in the liquid He storage section of the cryogenic container. After a predetermined amount of liquid He is injected into the cryogenic container, the flow path νJ switching mechanism is switched to supply liquid He to the recondensing heat exchanger, and operation as a recondensing type He liquefaction refrigeration system is started. In this way, another He liquefaction refrigerator that was previously required is omitted, and only one recondensing type He
With the liquefaction refrigeration system, it has become possible to simultaneously produce liquid He and maintain the cryogenic temperature in cryogenic containers.

[Example] Fig. 1 is a flow explanatory diagram showing an example of a He liquefaction refrigeration system according to the present invention, in which 10 is a main compressor, 7a to 7f are heat exchangers, 8a and 8b are expanders, and 9 is a Joule-Thomson. valve (hereinafter referred to as JT valve), 6 is a flow path switching mechanism (3-way valve), 17 is a cryogenic container, 4 is a recondenser, 18 is an object to be cooled, 12 is a gas bag, and 13 is a recovery compressor. Show each.

In FIG. 1, the He liquefaction refrigeration system S is a recondensing type He
The basic configuration is a liquefaction freezing system Sa, to which a He recovery system sb is attached. The discharge side of the main compressor 10 in the re-shrinking type He liquefaction refrigeration system Sa is connected to the high-pressure side line H of the heat exchangers 7a to 7f via a high-pressure waste pipe line 5a. The high pressure side line H is branched between heat exchangers 7b and 70 and between heat exchangers 7d and 7e, and expanders 8a,
8b, and the discharge sides of expanders 8a and 8b are connected to a low pressure line L between heat exchangers 7c and 7d and between heat exchangers 7e and 7f, respectively. Further, a JT valve 9 is interposed on the high pressure line side between the heat exchanger 7f and the recondenser 4, and a three-way valve 6 is further installed downstream thereof. A liquid N2 supply line 2o for pre-cooling is drawn into the heat exchanger 7a. Such a bookshelf type 1II He liquefaction refrigerator S
A pipe line 3 is branched from the three-way valve 6, and its end is opened facing the liquid He storage section of the cryogenic container 17. On the other hand, in the He recovery system sb, a recovery compressor 13 and a gas purifier 16 are arranged in order downstream of the gas bag 12,
A flow path is branched between the recovery compressor 13 and the gas purifier 16, and a recovery crude gas reservoir 14 is disposed at the branched end. The recovered He pipes 1a and lb drawn out from the gas phase of the cryogenic container 17 are connected to the gas introduction side of the gas bag 12, and the gas discharge side of the gas purifier 16 is connected to the high pressure gas pipe 5a. The above device is equipped with a stop valve 15a as shown in the figure.
, 15b, 15d and a pressure compensating valve 15c are respectively provided in each pipe.

Next, a method of operating the He liquefaction refrigeration system S configured as described above will be explained. The operation is divided into four steps: pre-cooling of the cryogenic container and the object to be cooled, storage of liquid He in the cryogenic container, recondensation freezing operation (maintaining cryogenic temperatures), and recovery of He, so each step will be explained below. do.

(+) First, pre-cool the 8i low-temperature container and the objects to be cooled.
Start the liquefaction operation of the e-liquefaction refrigeration system using the following procedure. Stop-2 stop valves 15a, 15b.

15d and the JT valve 9 are both closed, and liquid nitrogen is supplied from the liquid nitrogen pipe 20 to pre-cool the heat exchanger 7a. Next, the compressor 10 is started, and the pressurized high-pressure He gas is supplied to the heat exchangers 7a to 7f through the high-pressure gas pipe 5a. The high pressure He gas that has entered the heat exchangers 7a to 7f is sent to an expander 8a.

8b, where it expands isentropically and generates refrigeration, while the expanded He gas cools the high pressure He gas flowing through the high pressure gas pipe 5a in the process of passing through the low pressure gas pipe 2a and the heat exchangers 7e to 7a. After that, return to compressed alO.

By continuing this operation for a while, the vacuum container 1
Equipment such as heat exchangers 7a to 7e in 9 is cooled.

When the temperature on the outlet side of the low-temperature side expander 8b falls below a predetermined temperature, the JT valve 9 is opened to expand a portion of the low-temperature high-pressure He gas to atmospheric pressure, and the He gas whose temperature has further decreased due to expansion is returned to the low-pressure It is sent to the three-way valve 6 from the He gas pipe 5b.

At this time, the three-way valve 6 is open on the side of the pipe 3 that faces the liquid He storage part of the cryogenic container 17 (of course, liquid He is not stored at this point), and the pipe 3 side is opened so that the liquid He is fed through the pipe 3. The cryogenic container 17 and the object to be cooled 18 are precooled by the low-temperature He gas. Prior to this pre-cooling, the stop valves 15a and 15d are opened, and the recovery compression fi1
3 is also activated, and the He gas that has been pre-cooled in the cryogenic container 17 is sucked from the He recovery pipe 1a through the stop valve 15a and the gas bag 12 toward the recovery compressor 13.
It is compressed by the compressor 13. After impurities are further removed by the gas purifier 16, the purified high-pressure He gas is returned to the high-pressure He gas pipe 5a from the stop valve 15d.

When the temperature inside the cryogenic container 17 reaches a predetermined temperature (for example, 70 to 8
0K) or less, close the stop valve 15a, open the stop valve 15b and the compensating valve 15b, and close the heat exchanger 7f.
The cold is recovered by flowing the recovered He gas through the He recovery pipe l circle passing through 7a, and the temperature inside the cryogenic container 17 is further lowered.

(2) Liquid He storage in cryogenic container Continuing the above operations as a whole and circulating H.

The gas temperature is gradually decreasing. When the JTTe3 inlet temperature drops to a predetermined temperature (about 7K),
Liquid He begins to be generated on the outlet side, and liquid He begins to accumulate inside the cryogenic container 17. The unliquefied gas content is H
e After passing through the heat exchangers 7f to 7a from the recovery pipe 1b, the gas passes through the recovery compressor 13 and the gas purification device 16, and returns to the suction side of the compressor 10 for circulation. Compressor 1 with partial liquefaction of circulating gas
If the gas in the 0 system is insufficient, it is replenished from the impure gas reservoir 14 as appropriate.

(3) Recondensation refrigeration operation After liquid He is stored in the cryogenic container 17 until the object to be cooled 18 is sufficiently immersed, the three-way valve 6 is switched to
The He gas evaporated in the recondenser 4 is supplied to the recondenser 4, thereby recondensing the evaporated He gas in the cryogenic container 17 and keeping the level of liquid He constant. passes through the heat exchangers 7f to 7a sequentially from the low-pressure He pipe 2a,
While cooling the high-pressure He gas, it is heated to a pressure of 111 m
10 is returned to the suction side.

s[ato, pipes 5a, 5b, heat exchangers 7a to 7f, recondenser 4. Since the He flowing through the pipes 2a and 2b circulates in a closed circuit, there is no fear that He gas containing impurities in the cryogenic container 17 will enter the circulation system, and stable operation can be continued for a long period of time. With this kind of closed circuit rotation, there will be no shortage of refrigerant gas in the system, so there will be no stall or
The compensating valve 15d is closed, and the compensating valve 15c closes some of the He when the pressure inside the cryogenic container 17 exceeds a predetermined value.
The valve 15b serves to send gas to the recovery system through the valve 15b to prevent abnormal pressure rise in the circulation system, and is closed when the pressure is lower than a predetermined pressure.

(4) He recovery operation When stopping the refrigeration operation, recovery of He is performed by stopping the compressor lO, opening the stop valve 15a, closing the stop valve 15b, and using the heater installed in the cryogenic container 17. (not shown), the liquid He is heated and evaporated, and the He gas is recovered from the He recovery pipe 1a to the gas bag 12 via the stop/pipe 4p15a. In this case, it is also effective to provide a heater at a suitable location in the He recovery pipe 1a to help raise the temperature of the He gas.

It should be noted that the gas bag 12, He recovery compressor 13. Impure gas reservoir 14. A gas recovery system such as the gas purifier 16 does not necessarily have to be provided for each He liquefaction refrigeration device, and may of course be used in combination with other devices.

The present invention is configured as described above, and each step of pre-cooling equipment at the start of He freezing operation, storage of liquid He in a cryogenic container, and dyeable type 1II He freezing operation is performed by one device. It can be carried out continuously, the accessory equipment for pre-cooling can be omitted, all the conventional difficulties associated with nitrogen pre-cooling can be solved, and other equipment required for injection of liquid He can also be omitted. Became.

[Effects of the Invention] The present invention is configured as described above, and its effects can be summarized as follows.

(1) The structure is such that the supply destination of liquefied He can be switched between the recondenser installed in the ultra-low a container and the liquefied He storage section in the cryogenic container, so one device can be used at extremely low temperatures. Pre-cooling of the container and objects to be cooled, production of liquefied H8, and freezing operation can be performed, and the equipment is significantly simplified. Moreover, since these operations can be performed continuously, operability is good and full automation is easy.

(2) Since the flow path switching mechanism is provided on the downstream side of the JT valve, pressure fluctuations caused by switching are small and troubles such as He leakage are less likely to occur.

(3) Since only He is used as a refrigerant for pre-cooling and freezing operations, there are no problems encountered with conventional devices that use nitrogen for pre-cooling.

(4) Since all the He gas generated during the pre-cooling and freezing operation steps can be recovered and recycled, there is almost no loss of He.

(5) For example, even if the liquid He in the cryogenic container decreases due to a sudden heat load during slow freezing, liquid He can be replenished into the container by switching the wave path switching mechanism as necessary. .

[Brief explanation of drawings]

FIG. 1 is a schematic flow diagram illustrating an embodiment of the present invention. la, lb...He recovery pipe 3...branch pipe 4...recondenser 6...3
Direction valve (flow path switching mechanism) 7a to 7f... Heat exchanger 8a, 8b... Expander 9... JT valve 10... Compressor 12...
Gas bag 13... He recovery compressor IG...
He purifier 17...Cryogenic container 18...Object to be cooled

Claims (1)

[Claims] In a He liquefaction refrigeration system equipped with a recondensing type cryogenic container, a flow path switching mechanism is provided downstream of a Joule-Thomson valve installed in the high-pressure side line of the He liquefaction refrigeration system, and the liquefied He is supplied to the cryogenic vessel. 1. A He liquefaction refrigeration system, characterized in that it is configured to be able to switch between a recondenser provided in the cryogenic container and a liquefied He storage section in the cryogenic container.