JPS60253769A - Helium 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 Application of the Invention] The present invention relates to a helium refrigerator, and more particularly to a helium refrigerator that is directly connected to an object to be cooled to form a closed cycle.

[Background of the invention]

Helium gas used in helium refrigerators is a limited resource, cannot be easily obtained all the time, and is expensive, so helium gas is recycled and used. Therefore, helium refrigerators collect helium gas and
Comes with purification equipment. This recovery and purification equipment is
It consists of a gas bag, recovery J-compressor, purifier, and our own gas carder.

This method is called an external purification method, but since the gas is passed through a gas bag during gas recovery, the helium gas used in the closed cycle, which is less contaminated, becomes more contaminated than necessary. Therefore, the purifier must have more purification capacity than necessary3.Also, in this external purification method, the helium is liquefied, used in various experiments, etc., and then this gas is recovered and purified. Since it is for the system, the amount of processing is not too large.
It is designed for batch operation, not for long-term continuous operation.

Note that related devices of this type include, for example,
There is one described in JP-A-54-147174.

[Purpose of the invention]

An object of the present invention is to provide a helium refrigerator that can be operated continuously for a long time by making it possible to purify helium gas in parallel with the operation of the helium refrigerator.

[Summary of the invention]

The present invention is characterized in that an absorber having the function of removing impurities in helium gas is installed in a high-pressure gas line in a cold box so that it can be switched between adsorption and regeneration.
This makes it possible to purify helium gas in parallel with the operation of the helium refrigerator.

[Embodiments of the invention]

In a closed cycle system consisting of a helium refrigerator and a cooled object, most of the impurities in the helium gas in the system are air. This air rarely enters from outside during system operation, and the inside of the system is exposed to air during equipment inspections and modifications, so the system must be replaced before operation, but 100% replacement cannot be achieved. The residual air at that time gradually comes out into the helium gas.

In order to remove this impurity air by activated carbon low-temperature adsorption method, an adsorber containing activated carbon is installed in the middle of the high pressure gas line in the cold box, preferably in the middle of the high pressure gas line near the temperature of liquid nitrogen. This eliminates the need for any conventional external equipment.

In addition, as mentioned earlier, considering the source of impurities, they are concentrated after the equipment is started, so a bypass line is provided in the adsorber, and once the removal of impurities has finished, the process gas is passed to the bypass line side. During this time, if regeneration is performed to discharge impurities in the adsorber in preparation for the next changeover, continuous long-term operation is possible.

An embodiment of the present invention will be described below with reference to the drawings.

The helium gas as the process gas is pressurized to a predetermined pressure by the main compression ml, enters the cold box 19, and in the nitrogen cooler 2, the helium gas as the pre-cooling cryogen and the low-temperature gas flowing through the low-pressure return line. , 40-70K (varies depending on the process), and the temperature is below 80K, which is required for activated carbon low-temperature adsorption. This helium gas passes through the adsorber valve 7 provided in the high pressure gas line 21 on the downstream side of the nitrogen precooling heat exchanger 2, and passes through the adsorber valve 7 provided in the high pressure gas line 21 on the downstream side of the adsorber population valve 7. Enter vessel 3,
Impurities such as air are adsorbed and removed by the activated carbon filled in this helium gas, and the purified helium gas passes through the adsorber outlet valve 8 provided in the high pressure gas line 21 on the downstream side of the adsorber 3. After that, some of the gas becomes a turbine flow,
First turbine5. It expands adiabatically in the second turbine 6 and enters the low-pressure return line (9), where it becomes low-temperature return gas. On the other hand, the remaining gas becomes a JT flow and is cooled by the heat exchanger 4, and the JT valve l
O, the transfer ball passes through the transfer tube 11 and enters the cooling target, and the latent heat of liquid helium cools the object, and the evaporated gas passes through the transfer tube 11 and enters the low-pressure return line prisoner, where the heat exchanger 4. Sensible heat is recovered by the nitrogen precooling heat exchanger 2 and returned to the main compressor 1.

After starting the device, impurities in the helium gas in the system are considerably removed within a few days, and the concentration is reduced to a level that does not interfere with the operation of the device. When such a period comes, the adsorber 3 should be regenerated so that it can be used at any time.

Regeneration of the adsorber 3 is carried out by closing the adsorber inlet valve 7 and adsorber outlet valve 8, opening the bypass valve 9, and passing the process gas through the bypass line n.

First, the heated gas population valve 13 is opened, and then the heated gas outlet valve 15 is also opened, and the heated gas, which is a process gas from the main compressor 1, is introduced into the intake pipe 14 in the adsorber 3. Heat gas is passed through to raise the temperature of activated carbon, etc. to room temperature. When the temperature inside the adsorber 3 returns to approximately room temperature, the vacuum valve 56 is turned on and the vacuum pump 17 removes impurities inside the adsorber 3. After that, heating gas population valve 13. The heated gas outlet valve 15 is closed, the pre-cooled cryogen outlet valve is opened, and the LN2 supplied to the nitrogen pre-cooled heat exchanger 2 is guided as a cooling coolant to the convoluted pipe in the adsorber 3. This L inside Z
Activated carbon, etc. is cooled by passing N2 through it. This completes the regeneration of the adsorber 3.

The helium refrigerator as in this embodiment can provide the following effects.

(1) Since helium gas can be purified in parallel with the operation of the helium refrigerator, the helium refrigerator can be operated continuously for a long time.

(2) There is no secondary contamination caused by gas bags, etc.
There is less helium gas contamination and the load on the absorber for adsorbing impurities can be reduced.

〔Effect of the invention〕

As explained above, the present invention provides an adsorption device that has the function of removing impurities in helium gas in a high-pressure gas line in a cold box so that it can be switched between adsorption and regeneration. Since the helium gas can be purified by the method, it is possible to provide a helium refrigerator that can be operated continuously for a long time.

[Brief explanation of drawings]

The drawing is a system diagram showing an embodiment of a helium refrigerator according to the present invention. 3...Adsorber, 19...Cold box, 21...3...1 gain

Claims (1)

[Claims] 1. A helium refrigerator characterized in that an adsorption device having a function of removing impurities in helium is installed in a high-pressure gas line in a cold box so that adsorption and regeneration can be switched.