JPH06337191A - Method and device for liquefying helium - Google Patents

Abstract

PURPOSE:To provide method and device for liquefying helium, which are capable of utilizing the cold of cryogenic helium gas, discharged after finishing the pressure reducing of a container and/or the filling for shifting liquid helium, effectively and reducing the manufacturing cost of the liquid helium. CONSTITUTION:Low-temperature helium gas in a container 2, stored the liquid helium of high-pressure condition, is expanded directly into a liquid helium reserving tank 5 through an expansion valve 71. The introducing position of the low-temperature helium gas into a helium liquefying machine 1 is changed in accordance with the temperature of the low-temperature helium gas. Further, the helium gas, extracted out of the high-pressure side of the helium liquefying machine 1, is introduced into the container 2, which is filled with liquid helium for shifting, to heat the inside of the container 2 and recover a cryogenic gas in the container 2 by returning it into the low-pressure side of the helium liquefying machine 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a helium liquefaction method and apparatus, and more particularly to a helium liquefaction method and apparatus for efficiently utilizing liquid helium packed and conveyed in a liquid helium container.

[0002]

PRIOR ART AND PROBLEM TO BE SOLVED BY THE INVENTION The demand for helium in Japan has been increasing at an annual rate of 10% or more, and is now double the consumption of five years ago.
It is thought that this is because superconducting magnets that function when cooled to liquid helium temperature are being applied to nuclear fusion, high energy physics, magnetic levitation trains, energy storage, medical equipment, and the like. Further, the ratio of liquid helium to the helium demand is increasing year by year, and has recently exceeded 50%.

On the other hand, in Japan, the entire amount of helium is imported from overseas, and liquid helium is imported in a state of being filled in a liquid helium container. Liquid helium filled in a container at atmospheric pressure by the export source (sales source) arrives in Japan after about 20 days of voyage, but due to heat loss to the container during container transportation, the pressure inside the container is about 3 atm. Rise to. In Japan, liquid helium is subdivided from a container into a small cryogenic container and sold to customers. In order to subdivide liquid helium in a container efficiently, first, the pressure inside the container should be 1.
It is necessary to reduce it to about 3 to 1.5 atm.

For this reason, conventionally, cryogenic helium gas released when the container is stepped down is heated to near room temperature by a warmer and filled in a high-pressure container, which is sold as helium gas, and the container after the stepping down is also carried out. The liquid helium inside was transferred to a small cryogenic container for sale.
The container dispensed with liquid helium in this way is
Although it will be sent back to overseas distributors, in order to effectively use the container, it is preferable to operate the container inside temperature at 20 K or less. On the other hand, since it has been confirmed that the temperature change inside the container during transportation to the overseas distributor is 5 K or less, it is possible to recover the helium gas by heating the temperature inside the container to 15 K. The recovery amount of helium due to this temperature rise is about 4000 liters in terms of liquid helium in the case of a 11,000 gallon container.

Since about 4.5 K of saturated helium gas remains in the container in which the liquid helium is all transferred into the small cryogenic container as described above, the transfer of the liquid helium is conventionally completed. After introducing room temperature helium gas into the container and pressurizing it to about 3 atm and setting the container temperature to about 15K, draw out the helium gas in the container to near the above contracted amount and warm it to room temperature with a warmer. It was heated up to the neighborhood and filled in a high-pressure container and sold as helium gas.

In such a conventional method, the sales ratio of imported helium as liquid helium is such that when liquid helium is directly filled from a container into a small cryogenic container, it is transferred to a small cryogenic container. Considering the transfer loss of liquid helium, it becomes about 40%. Therefore, the demand ratio of liquid helium is about 5 as mentioned above.
Since it is 0%, there will be an imbalance in supply and demand. Although it is possible to liquefy and sell helium gas at room temperature, liquefaction requires a great deal of cost.

Therefore, according to the present invention, the cryogenic helium gas released at the time of depressurization of the container before the liquid helium is transferred to the small cryogenic container and the liquid helium remains in the container after the transfer of the liquid helium is completed. It is an object of the present invention to provide a helium liquefaction method and apparatus that can effectively utilize the cold heat of the cryogenic helium gas that is used and reduce the manufacturing cost of liquid helium.

[0008]

In order to achieve the above object, the helium liquefaction method of the present invention has, as a first configuration, a low temperature helium gas in a container in which liquid helium is stored, which is derived from the low temperature helium gas. Is directly expanded into the liquid helium storage tank through an expansion valve. Further, according to the method of the present invention, low-temperature helium gas in a container storing liquid helium is discharged and introduced into a helium liquefier having a helium compressor, a heat exchanger, an expansion turbine, a JT valve, a liquid helium storage tank, etc. to liquefy. In doing so, the second configuration is characterized in that the introduction position of the low-temperature helium gas into the helium liquefier is changed according to the temperature of the low-temperature helium gas, and the third configuration is that after deriving liquid helium. The helium gas extracted from the high-pressure side of the helium liquefier is introduced into the container to heat the inside of the container, and the low-temperature gas in the container is discharged and returned to the low-pressure side of the helium liquefier for recovery. Is characterized by.

Further, the helium liquefying apparatus of the present invention draws out low-temperature helium gas in a container storing liquid helium, and helium compressor, heat exchanger, expansion turbine, JT.
A device for introducing and liquefying a helium liquefier equipped with a valve and a liquid helium storage tank, wherein a conduit for discharging low temperature helium gas in the container is branched into a plurality of branch pipes, and one of the branch pipes is an expansion valve. Connected to the inlet of the liquid helium storage tank via a plurality of other branch pipes from the liquid helium storage tank to the helium compressor through a heat exchanger and expansion valves respectively at different operating temperatures of the system. It is characterized in that it is provided with a control means for opening and closing each of the expansion valves according to the temperature of the helium gas in the conduit for discharging the low-temperature helium gas in the container, while being connected via the helium liquefier. A path for introducing high-pressure helium gas from the side into the container is provided.

[0010]

[Operation] According to the first configuration of the method of the present invention, since the low temperature helium gas is directly expanded into the liquid helium storage tank through the expansion valve and a part thereof is liquefied, the liquid helium gas does not require power. Is obtained. According to the second configuration of the method of the present invention and the first configuration of the apparatus of the present invention, when the low temperature helium gas in the container is introduced into the helium liquefier,
The helium gas heated by pre-cooling of the pipe can be introduced at a position according to the temperature, so that the helium gas can be used in a stable state without disturbing the operating state of the helium liquefier. The liquefaction machine can be operated. Further, according to the third configuration of the method of the present invention and the second configuration of the device of the present invention, it is possible to recover a predetermined amount without waste while utilizing the cold heat of the cryogenic helium gas remaining in the container. .

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail based on an embodiment shown in FIG. This helium liquefier
Helium compressor 11 and 6 heat exchangers 21, 22, 2
3,24,25,26 and two expansion turbines 31,3
2 and a valve 33 for adjusting the amount of cold generated in the expansion turbines 31, 32, a JT valve 41, and a liquid helium storage tank 51. A helium liquefier 1 is filled with liquid helium. 2 are connected.

Between the helium liquefier 1 and the container 2, a conduit 61 for discharging low-temperature helium gas in the container, and four branch pipes 62, 6 branched from the conduit 61.
3, 64, 65 and expansion valves 71 provided on each branch pipe,
72, 73, 74, a temperature indicating controller 81 and a container 2 as control means for switching and opening and closing the expansion valves.
And a pressure gauge 82 for detecting the completion of the step-down of pressure inside the container 2, and a heating branch pipe branched from the high-pressure side line 12 of the helium liquefaction machine 1 as a system for heating the inside of the container 2. 66 is provided, and a valve 75 for controlling the amount of branch gas to the heating branch pipe 66 is provided.

In the helium liquefier 1, the helium compressor 11 boosts the pressure to several tens of kg / cm ² G and the high pressure side line 12 is used.
The high-pressure helium gas led to each heat exchanger 21-26
And cool it by exchanging heat with the low temperature return gas.
For example, it is JT expanded to 1.2 atm and directly expanded into the liquid helium storage tank 51 to produce liquid helium. The gas phase in the liquid helium storage tank 51 is led out to the return pipe 13 as a low temperature return gas, After the heat is exchanged with the high-pressure helium gas in the exchangers 26 to 21 to raise the temperature, it is sucked into the helium compressor 11 again. Further, a part of the high-pressure helium gas is branched to the expansion turbines 31 and 32 and adiabatically expanded in the expansion turbines 31 and 32 to generate cold,
It joins the low-temperature return gas and becomes a cooling source for high-pressure helium gas. The helium compressor 11 is provided with a buffer tank for pressure adjustment (not shown), and the helium gas at room temperature is received in the tank to continuously produce liquid helium.

When a container 2 filled with liquid helium imported from overseas arrives, the container 2 is connected to the helium liquefaction machine 1 to enter a step-down operation mode for reducing the pressure in the container.

In the step-down operation mode, first, the container 2 and the helium liquefier 1 in operation are connected through a conduit 61 for introducing helium gas, and a helium gas introduction valve (not shown) is opened to open the inside of the container 2. When the introduction of the low-temperature helium gas is started, the temperature indicating controller 81 detects the temperature of the helium gas flowing through the conduit 61, and the temperature from the normal temperature range of the introduction start until the conduit 61 is sufficiently cooled, for example, 80K.
Up to the temperature of 2, the expansion valve 74 of the branch pipe 65 connected to the highest temperature region of the system of low-temperature return gas is opened, and the helium gas in the temperature range is expanded and reduced according to the pressure of the introduction part, It is introduced between the heat exchanger 22 and the first heat exchanger 21.

Next, the range until the temperature of the helium gas in the conduit 61 becomes 80 K or lower, for example, 30 K, is as follows:
The expansion valve 74 is closed, the expansion valve 73 of the branch pipe 64 connected between the fifth heat exchanger 25 and the fourth heat exchanger 24 is opened, and helium gas is introduced into the path therebetween. Furthermore, the temperature of helium gas drops below 30K,
For example, up to 6K, the expansion valve 73 is closed and
The expansion valve 72 of the branch pipe 63 connected to the inlet of the sixth heat exchanger 26 in the lowest temperature region is opened, and low temperature helium gas is introduced into this portion. And from the container 2 to the conduit 6
When the temperature of the low temperature helium gas introduced via 1 becomes 6 K or less, the expansion valve 72 is closed, and the expansion valve 71 of the branch pipe 62 connected to the secondary side of the JT valve 41 is opened. The low temperature helium gas expanded in 71 is directly expanded in the liquid helium storage tank 51. This allows the container 2
A part of the low temperature helium gas derived from can be directly liquefied and stored in the liquid helium storage tank 51.

The low-temperature helium gas that has not been liquefied during the direct expansion is led to the return pipe 13 together with the helium gas in the liquid helium storage tank 51, and is sucked into the helium compressor 11 via the heat exchangers 26 to 21. The direct expansion operation of this low temperature helium gas into the liquid helium storage tank 51 is
The process is repeated until the pressure gauge 82 detects that the pressure of the low temperature helium gas, that is, the pressure inside the container 2 has dropped to a predetermined pressure, for example, 1.3 atm.

As described above, by directly expanding the low temperature helium gas in the container 2 and introducing it into the liquid helium storage tank 51, the cold contained in the low temperature helium gas in the container 2 can be effectively utilized, and the normal temperature can be utilized. A liquefaction amount of about 3.4 times is obtained as compared with the case of liquefying the helium gas, and an average value from the start to the end of the pressure reduction operation is about 2.2 times the liquefaction amount.

When entering the step-down operation mode, the pipe (conduit 6) connecting the container 2 and the helium liquefier 1 is connected.
Since 1) and the like are at room temperature, when the low temperature helium gas in the container 2 is introduced into the liquid helium storage tank 51 in this state, the helium gas heated to room temperature in the pipe portion is introduced into the liquid helium storage tank 51. Therefore, the introduced helium gas near room temperature causes the liquid helium in the storage tank 51 to rapidly evaporate, and due to the sudden evaporation of the liquid helium, a sudden pressure change occurs in the system of the helium liquefier 1. The helium liquefier 1 cannot be operated normally.

Therefore, before introducing the low-temperature helium from the container 2 into the liquid helium storage tank 51, it is necessary to precool the pipe connecting the container 2 and the helium liquefier 1. At the beginning of the operation mode,
By changing the introduction position to the helium liquefier 1 according to the temperature of the introduced helium gas, the operation can be continued in a stable state without disturbing the temperature balance in the helium liquefier 1, and The cold heat of the low temperature helium gas in the container 2 can be effectively used.

The liquid helium in the container 2 and the liquid helium in the liquid helium storage tank 51, which have been depressurized in this way, are transferred to a small cryogenic container and sold to consumers in the same manner as in the conventional case.

The introduction position of the helium gas in the initial stage of the step-down operation mode may be set appropriately in consideration of the configuration of the helium liquefier, the temperature range allowed in each heat exchanger block, the flow rate range, and the like. It is possible and the number of branch pipes can be set arbitrarily. Further, in the above embodiment, the low temperature helium gas in the container was introduced into the liquid helium storage tank provided in the helium liquefier, but without using the helium liquefier, for example, the gas at the time of precooling is the same as the conventional one. It is also possible to fill the high-pressure container as helium gas and directly introduce the low-temperature helium gas after completion of precooling into the liquid helium storage tank. Further, the first heat exchanger may be provided with a liquid nitrogen vaporization passage to supply liquid nitrogen to increase the production of liquid helium.

After performing the above-mentioned step-down operation and transferring the liquid helium in the container 2 into the small cryogenic container in the same manner as in the conventional case, the saturated helium gas of about 4.5 K is stored in the container 2 as described above. Since it remains, it is desirable to collect it to the extent permitted by the contract and make maximum use of the imported liquid helium to reduce costs. Therefore, in the present invention, the helium gas remaining in the container 2 is recovered, and liquid helium is produced by utilizing the cooling of the helium gas.

The helium gas in the container 2 is recovered by introducing helium gas at an appropriate temperature into the container 2 to heat the inside of the container 2, and then introducing the helium gas and expanding the container 2 due to the temperature increase. It is performed in a heating operation mode in which the low-temperature helium gas is discharged and introduced into the helium liquefier 1 described above.

When the warming operation mode is entered, the valve 75 of the warming branch pipe 66 is opened, and, for example, helium gas at a temperature of 25K (hereinafter referred to as warming gas) is warmed from the high pressure side line 12 for warming. It is introduced into the lower part of the container 2 through the branch pipe 66. This warmed gas is mixed with the low temperature helium gas in the container 2 and initially becomes a gas of about 4.5 K, which is led out from the conduit 61, and an expansion valve at a position corresponding to the temperature of the gas, that is, It is introduced from the expansion valve 72 of the branch pipe 63 connected to the inlet of the sixth heat exchanger 26 in the lowest temperature region into the return pipe 13 on the low pressure side of the liquefier. Thereby, the cold of the gas is effectively recovered in each of the heat exchangers 26 to 21.

Since the temperature of the helium gas recovered from the conduit 61 gradually rises with the progress of the heating operation by introducing the heating gas, the temperature of the helium gas is about 11
When it becomes K, the introduction position to the return pipe 13 is changed to the branch pipe 6.
The expansion valve 73 of No. 4 is changed to. The temperature of the recovered helium gas, that is, the temperature inside the container 2 is 15
When it reaches K, the recovery operation is terminated.

By recovering the residual helium gas in the container 2 to the low pressure side of the helium liquefier 1 in this way,
At the start of the heating operation mode, a liquefaction amount of about 3.4 times is obtained, and an average value of about twice the liquefaction amount is obtained.

The operation in the pre-cooling stage at the time of starting the heating operation mode is carried out until the expansion valve 72 is opened in the same procedure as in the pressure reducing operation mode, and then the above-mentioned heating operation mode is started. .

[0029]

As described above, according to the present invention,
Cryogenic helium gas released when the pressure of the container is lowered before the liquid helium in the container is transferred to the small cryogenic container, or cryogenic helium gas remaining in the container after the transfer of the liquid helium is completed. It is possible to effectively use the cold energy of the product without waste, and it is possible to efficiently produce liquid helium with high demand and high added value.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Helium liquefier, 2 ... Container, 11 ... Helium compressor, 21, 22, 23, 24, 25, 26 ... Heat exchanger, 31, 32 ... Expansion turbine, 41 ... JT valve, 51 ...
Liquid helium storage tank, 61 ... Conduit, 62, 63, 64, 6
5 ... Branch pipe, 66 ... Warming branch pipe, 71, 72, 73,
74 ... Expansion valve, 81 ... Temperature indicator controller, 82 ... Pressure gauge

Claims (5)

[Claims] 1. A method for liquefying helium, wherein low-temperature helium gas in a container storing liquid helium is led out and the low-temperature helium gas is directly expanded into a liquid helium storage tank through an expansion valve. 2. A low-temperature helium gas in a container storing liquid helium is discharged, and a helium compressor, a heat exchanger,
In introducing and liquefying a helium liquefier having an expansion turbine, a JT valve, a liquid helium storage tank, etc., the introduction position of the low-temperature helium gas to the helium liquefier is changed according to the temperature of the low-temperature helium gas. And a helium liquefaction method. 3. The low-temperature helium gas remaining in the container after the liquid helium is discharged is discharged and introduced into a helium liquefier having a helium compressor, a heat exchanger, an expansion turbine, a JT valve, a liquid helium storage tank, and the like. When liquefying, helium gas extracted from the high pressure side of the helium liquefier is introduced into the container to heat the inside of the container, and low-temperature helium gas in the container is discharged to depressurize the helium liquefier. A method for liquefying helium, which comprises recovering the helium by recovering it. 4. A low temperature helium gas in a container storing liquid helium is discharged, and a helium compressor, a heat exchanger,
A device for introducing and liquefying a helium liquefier equipped with an expansion turbine, a JT valve, and a liquid helium storage tank, wherein a conduit for discharging low-temperature helium gas in the container is branched into a plurality of branch pipes, and one of the branch pipes is branched. One is connected to the inlet of the liquid helium storage tank via an expansion valve, and the other plurality of branch pipes are connected to different portions of the operating temperature of the system that are sucked into the helium compressor from the liquid helium storage tank through the heat exchanger. A helium liquefaction device, characterized in that the helium liquefaction device is provided with a control means that is connected through expansion valves and that opens and closes each of the expansion valves according to the temperature of the helium gas in a conduit for introducing low temperature helium gas in the container. 5. The helium liquefaction device according to claim 4, wherein a path for introducing high-pressure helium gas into the container from the high-pressure side of the helium liquefaction machine is provided.