JP3113992B2 - Helium liquefaction refrigeration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a helium liquefaction refrigeration system, and more particularly to a helium liquefaction refrigeration system having a system for recovering helium in a system when the pressure in the system abnormally increases.

[0002]

2. Description of the Related Art A member to be cooled such as a superconducting magnet is 4.5.
As a means for cooling to extremely low temperature such as K, a helium liquefaction refrigeration apparatus for generating liquid helium has been conventionally used. This helium liquefaction refrigeration system generally has
As shown in FIGS. 5 to 8, a circulation compressor 1, a heat exchanger group in which a plurality of heat exchangers are combined, a JT valve 3 for expanding and lowering the temperature of the helium gas cooled in the heat exchanger group 2, The JT
The circulating system includes a cooling unit (cryostat) 4 for cooling the cooled object M with liquefied helium generated by expansion of the valve 3. The heat exchanger group 2 is provided with an expansion turbine or a compressor for generating cold for cooling helium gas as required.

In such a helium liquefaction refrigeration system, since the thickness of the pressure receiving portion cannot be increased from the viewpoint of reducing the heat loss of the cryostat 4 and the dimensions, etc., the refrigerated body and the liquefied helium are accommodated. The design pressure of the cryostat 4 cannot be increased.

Therefore, when a large amount of liquefied helium in the cryostat 4 evaporates due to an abnormality in the system, for example, quenching of the magnet, it is necessary to quickly release this gas to prevent the pressure from rising.

For this reason, first, in the helium liquefaction refrigeration apparatus shown in FIG. 5, when the pressure in the system rises abnormally, a helium in the system is recovered and a gas bag or a collection bag for lowering the pressure in the system is recovered. Tank (hereinafter referred to as collection container) 5
Is provided. The recovery container 5 communicates with the cryostat 4 via an emergency release valve 6 that opens when the pressure in the system rises above a predetermined pressure and a heater 7 that heats helium to room temperature. When an abnormal pressure occurs, the emergency release valve 6 is opened to recover helium in the system into the recovery container 5. The helium recovered in the recovery container 5 is subjected to a purification treatment as necessary, and then returned to the circulation system using a compressor or the like.

As a system for recovering helium in the system at the time of the above-mentioned abnormality, as shown in FIG.
In addition to a method in which helium is heated to room temperature and collected in a collection container, a configuration in which helium is collected in a low temperature state is also known.

The helium liquefaction refrigeration system shown in FIG. 6 is provided with a low-temperature recovery container 8 via an emergency release valve 6, a path 9 for supplying low-temperature helium for cooling the low-temperature recovery container 8, and a low-temperature recovery An exhaust path 11 having a low-temperature exhaust pump 10 for exhausting the inside of the container 8 is provided. In this device, the helium recovered in the low-temperature recovery container 8 is returned to the return line 1a of the circulation system by the low-temperature exhaust pump 10.

In the helium liquefaction refrigeration system shown in FIG. 7, the helium recovered in the low-temperature recovery container 8 is supplied to a heater 7.
After returning to normal temperature, the normal temperature vacuum pump 12 removes oil and the like, and then returns to the suction side of the circulating compressor 1.

Further, in the helium liquefaction refrigeration system shown in FIG. 8, the helium recovered in the low-temperature recovery container 8 is transferred to the heat exchanger group 2 by a circulating helium return line 1a of a circulation system.
Separately, a return line 1b is provided so that the cold is recovered by the heat exchanger group 2 and then returned to the suction side of the circulating compressor 1 by the room temperature vacuum pump 12.

In each of the devices shown in FIGS. 6 to 8, the emergency release valve 6 is closed during normal operation, the JT valve 3 and the valve 9a provided in the path 9 and the valve 13 in the path for returning the recovered helium are respectively The operation is performed in an open state, and when an abnormality occurs, only the emergency release valve 6 is opened to recover the liquefied helium in the cryostat 4.

According to each of the above-mentioned structures, it is possible to prevent the pressure of the cryostat 4 from increasing at the time of an abnormality and to recover helium. However, as described above, since the design pressure of the cryostat is low, Recovery must also be performed at low pressure.

[0012]

However, a recovery container for recovering helium at room temperature, such as the recovery container at room temperature and normal pressure shown in FIG. 5, requires not only a very large space but also the contamination of impurities. There are also problems.

On the other hand, as shown in FIGS. 6 to 8, if a container maintained at a low temperature is prepared and the inside thereof is constantly kept at a low pressure (atmospheric pressure or less), helium can be easily recovered. However, for this purpose, there is a problem in reliability and efficiency, for example, after heating through a low-temperature exhaust pump or a heat exchanger, exhausting by a normal temperature vacuum pump.

Accordingly, the present invention provides a helium liquefaction system having a helium recovery system capable of efficiently reducing the pressure in a vessel for recovering helium in the event of an abnormality, returning helium to the circulation system after recovery, and preventing contamination of impurities. It is intended to provide a refrigeration device.

[0015]

In order to achieve the above-mentioned object, a helium liquefaction refrigeration system according to the present invention has a first configuration in which circulating helium compressed by a circulating compressor is cooled and cooled.
In a helium liquefaction refrigeration system that expands and liquefies to cool a cooled object, a recovery container is provided to a cooling portion of the cooled object via a valve and a heater that open when the pressure in the cooling portion increases. In addition to the above, an ejector is provided that maintains the inside of the gas container in a reduced pressure state during a normal operation by using a part of the circulating helium as a driving source.

The second configuration is the same as the first configuration,
On the discharge side of the circulating compressor, a branch path for providing a part of the compressed helium gas as a drive source of the ejector is provided, and a path for circulating the helium gas after ejecting the ejector to the suction side of the compressor is provided. A flow control valve for adjusting a branch amount of the compressed helium gas serving as a drive source of the ejector in accordance with a pressure in the collection container is provided.

[0017] In a third configuration, a low-temperature helium recovery container is connected to the cooling part of the cooled object via a valve that opens when the pressure in the cooling part rises, and the cooling part is provided inside the cooling part. Through a valve that closes when the pressure of
An ejector for depressurizing the inside of the low-temperature helium recovery container using the circulating helium as a drive source and a path for supplying a part of the liquefied helium into the low-temperature helium recovery container are provided.

Further, in a fourth configuration, an expansion turbine for expanding helium after cooling so as to have a critical pressure or more, and helium after expansion is further cooled by liquefied helium in a liquefied helium container to form a cooled object. A path for supplying to the cooling unit, a path for supplying a part of the expanded helium into the liquefied helium container via a valve that opens when the pressure in the cooling unit increases, and A path for expanding helium derived from the cooling unit with an ejector via a valve that closes when the pressure in the cooling unit rises and supplying the helium to the liquefied helium container, and opening when the pressure in the cooling unit increases. A helium recovery container connected to the cooling unit via a valve that opens, and a part of the liquefied helium in the liquefied helium container through a valve that closes when the pressure in the cooling unit increases. A path for supplying the helium recovery container and a path for connecting the inside of the helium recovery container and the suction side of the ejector via a valve that closes when the pressure in the cooling unit increases. And

[0019]

[Operation] According to the above configuration, since the pressure in the vessel for recovering helium is reduced by the ejector, there is no possibility of contamination of impurities and the reliability is high. In addition, since circulating helium is used as the drive source of the ejector, energy consumption can be reduced. Especially in the case of an ejector provided in a low-temperature part, the expansion energy that has been wasted by the expansion using the JT valve is recovered. It can be effectively used as energy for reducing the pressure in the container and energy for returning the recovered helium to the circulation system.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the embodiments shown in the drawings.

FIG. 1 shows a first embodiment of the present invention, in which helium is recovered at normal temperature when an abnormality occurs. The helium liquefaction refrigeration apparatus shown in this embodiment is also provided with a circulating compressor 1, a heat exchanger group 2, a JT valve 3, a cryostat 4 for accommodating a cooled object M, and the like, similarly to those shown in the above-described conventional examples. Helium gas compressed to high pressure by the circulation compressor 1 is cooled by exchanging heat with the return gas in the heat exchanger group 2, expanded by the JT valve 3 and expanded into the cryostat 4. It flashes to generate liquefied helium.

The helium gas in the cryostat 4 which has cooled and evaporated the cooled object M is led out to the return line 1a as a low-temperature return gas, passes through the heat exchanger group 2, and cools the compressed helium gas. After the temperature reaches room temperature, it is sucked into the circulating compressor 1 and compressed again to circulate through the path.

A system for recovering helium in the event of an abnormality includes a helium recovery container 21 communicating with the cryostat 4 through an emergency release valve 6 and a heater 7 similar to the apparatus shown in FIG. The ejector 22 for sucking the gas in the helium recovery container 21 by using the high-pressure helium gas compressed in the drive source as a driving source and depressurizing the inside of the recovery container 21, and adjusting the flow rate of the high-pressure helium gas to the ejector And a pressure indicating controller (PIC) 24 for adjusting the opening degree of the flow control valve 23 for adjusting the capacity of the cryostat 4 and recovering the helium by increasing the pressure of the cryostat 4. And a controller 26 that opens the emergency release valve 6 and closes the flow control valve 23 and the recovery valve 25 on the ejector suction side.

The collection container 21 is different from the case where the above-mentioned collection container is a gas bag or the like.
For example, it is a vacuum container that can be kept at 0.4 atm, and has a sufficient hermeticity.

During normal operation, the emergency release valve 6 is closed,
The recovery valve 25 is open, the flow control valve 23 is adjusted to an appropriate opening by the PIC 24, and the recovery container 2
1 is maintained at a predetermined reduced pressure state.

When the quench occurs and the pressure in the cryostat 4 rises, the controller 26 operates to open the emergency release valve 6, and the flow control valve 23 and the recovery valve 25 on the ejector suction side are opened. Close.

Thus, the helium gas in the cryostat 4 is discharged into the recovery container 21 via the emergency discharge valve 6 and the heater 7, and the inside of the cryostat 4 is prevented from rising above a predetermined pressure.

At this time, the collection pressure is 1.8 atm, the pressure in the collection container 5 before collection is 1.2 atm,
In this embodiment, the pressure in the collection container 21 is 0.4 atm.
And then, if the volume required for the recovery and V _5, V ₂₁ respectively, both the volume ratio _{of, (1.8-1.2) V 5 = (} 1.
From 8-0.4) V _21, about 1: 0.43, the volume of the collection container 21 will be requires only about 43% of the volume of the collection container 5.

Further, the recovery container 21 is a vacuum container having a hermeticity, and the ejector 22 using a part of the circulating helium as a driving source for reducing the pressure in the container 21 is used. There is almost no risk of impurities being mixed into the container, and since a vacuum pump or the like is not used for reducing the pressure in the recovery container 21 and returning the recovered helium, the reliability is high.

FIG. 2 shows a second embodiment of the present invention, in which helium in a liquefied state at a low temperature is recovered similarly to FIGS. 6 to 8 described above.

As described above, the apparatus of this embodiment connects the cryostat 4 and the low-temperature helium recovery container 31, which is a tank having a low-temperature insulation structure, via the emergency discharge valve 6, and expands the cooled high-pressure helium gas. Means
An ejector 32 is used instead of the JT valve.

The low-temperature helium recovery container 31 has a path 33 for supplying a part of the liquefied helium in the cryostat 4 to keep the container 31 at a low temperature, a low-pressure helium recovery container 31 and a suction side of the ejector 32. Are provided, and valves 35 and 36 are provided in the two paths 33 and 34, respectively, to close when the pressure in the cryostat 4 increases. The route 33
Is a flow control valve for adjusting the supply amount of liquefied helium to the low-temperature helium recovery container 31, and a liquid level indicating controller (L) provided for the low-temperature helium recovery container 31.
The opening is controlled by the IC) 37.

The opening and closing of the valve 36 and the emergency release valve 6 are controlled by a controller 38. When the pressure in the cryostat 4 increases, the valve 36 and the valve 39 upstream of the ejector 32 are closed, and the emergency release valve 6 is opened. Being opened,
Valve 35 closes.

The low-temperature helium recovery container 31 is an adiabatic vacuum container having substantially the same volume as the cryostat 4, and is set so that almost all liquefied helium in the cryostat 4 can be recovered in the event of an abnormality.

During normal operation, the cryostat 4
A part of the liquefied helium is supplied into the low-temperature helium recovery container 31 via the path 33, and the helium gas vaporized in the container 31 is sucked by the ejector 32 through the path 34 and returned to the cryostat 4. Helium gas in the cryostat 4 returns to the return line 1a as described above.
And circulates to the circulation compressor 1.

As described above, the supply of liquefied helium for cooling the low-temperature helium recovery vessel 31 and the energy for decompressing the inside of the vessel 31 are performed by expanding the high-pressure helium gas in the ejector 32 driven by circulating helium. By obtaining with energy, reliability and efficiency are improved without the need for a conventional mechanical vacuum pump. Further, since the process gas itself is used as the high-pressure gas for driving the ejector 32, there is no need to control the pressure in the low-temperature helium recovery container 31, that is, the exhaust pressure.

Further, the low-temperature helium recovered in the low-temperature helium recovery container 31 is sucked by the ejector 32 and returned to the circulation system when the operation of the apparatus is restarted, so that a compressor is unnecessary and impurities may be mixed. Absent.

The supply of liquefied helium into the low-temperature helium recovery container 31 is performed by branching a part of the low-temperature high-pressure helium gas on the upstream side of the ejector 32, expanding the gas with a JT valve, and flushing the gas into the container 31. Alternatively, the liquid may be supplied from a liquefied helium storage tank provided in parallel with the cryostat 4. In addition, the supply amount is
It can be controlled by temperature instead of the liquid level inside.

FIG. 3 shows a third embodiment of the present invention, in which the present invention is applied to a process using a supercritical expansion turbine.

In the present embodiment, the helium gas compressed to a high pressure by the circulating compressor 1 is cooled by the heat exchanger group 2 and expanded by the expansion turbine 41, and then the immersion heat provided in the liquefied helium container 42. The supercooled helium obtained is further cooled by the exchanger 43 and supplied to the cooling coil 44 to cool the object to be cooled.

The helium gas led out of the cooling coil 44 is expanded in the ejector 45 and then flashed in the liquefied helium container 42 to partially liquefy. The helium gas in the liquefied helium container 42 is circulated to the circulating compressor 1 through the return line 1a as described above.

A system for recovering helium in the event of an abnormality includes a helium recovery container 46 communicating with the cooling coil 44 via the emergency release valve 6 similar to the above, and a liquefied helium container for cooling liquefied helium for cooling the container 46. A system 47 supplied from the helium recovery container 46 and an ejector 45
And a path 48 for connecting the suction side to the suction side. The two paths 47 and 48 are provided with valves 49 and 50, respectively, which close when the pressure in the system increases.

In the path on the outlet side of the expansion turbine 41, switching valves 51 and 52 for switching the flow of helium when an abnormality occurs, and a pressure indicating controller (PIC) for controlling the switching between the two valves. 53 are provided. Further, flow control valves 54 and 55 are provided on the inlet side of the expansion turbine 41 and the drive gas introduction side of the ejector 45, respectively.

During normal operation, the emergency release valve 6 is fully closed,
Except for the switching valve 52 being slightly opened, the other valves are opened to an appropriate opening degree to circulate helium, and the object to be cooled is cooled by the cooling coil 44.

When an abnormality occurs and the pressure in the system rises, the emergency discharge valve 6 and the switching valve 52 are opened and the other valves are closed, and the supply of helium to the cooling coil 44 is stopped. Helium in the cooling coil 44 is collected in the helium collection container 46.

Further, by switching the switching valves 51 and 52, the operation of the expansion turbine 41 can be stably performed even when an abnormality occurs, and the switching valve 52 on the bypass side is slightly opened even in normal times. Thereby, the switching can be performed smoothly.

As described above, when the ejector 45 is installed in the low temperature part and the inside of the helium recovery container 46 is evacuated, the flow rate of the driving high-pressure gas may be too large for the ejector 45. What is necessary is just to install the bypass valve 56 which bypasses 45 and the flow control valve 55, and to adjust a flow.

When a plurality of cooling coils are installed to cool a plurality of objects to be cooled, each of the coils is connected to one helium recovery container 46 via the emergency release valve 6, and the helium recovery container 46 is shared. It is also possible.

FIG. 4 shows a modification of the above embodiment, in which a path 47 for supplying liquefied helium to a helium recovery container 46 is connected immediately after the emergency release valve 6.
The same elements as those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof will be omitted.

With such a configuration, the discharge line below the emergency release valve 6 can be pre-cooled, so that the helium to be recovered can be cooled to a lower temperature, which is effective. This configuration can be similarly applied to the path 33 in FIG.

The present invention can be applied to various types of helium liquefaction refrigeration apparatuses, and the configuration of the refrigeration apparatus main body can be an appropriate configuration.

[0052]

As described above, in the helium liquefaction refrigeration system of the present invention, since the inside of the recovery container is depressurized by using the ejector, the volume of the container required for recovering helium can be reduced. , The ejector,
Since there is no mechanical operation part, maintenance is unnecessary, no impurities are generated, and reliability can be greatly improved.

Further, when a part of the discharge gas of the circulating compressor is used as the driving gas for the ejector, the amount of the driving gas is adjusted according to the pressure in the recovery container, so that the compressed gas is not consumed wastefully. Can be prevented.

Further, when an ejector is provided in place of the conventional JT valve, the energy at the time of expansion, which has been wasted until now, is used to reduce the pressure inside the recovery container, so that the efficiency is improved. Can be achieved.

[Brief description of the drawings]

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

FIG. 2 is a system diagram showing a second embodiment of the present invention.

FIG. 3 is a system diagram showing a third embodiment of the present invention.

FIG. 4 is a system diagram showing another embodiment of the present invention.

FIG. 5 is a system diagram of a conventional helium liquefaction refrigeration apparatus.

FIG. 6 is a system diagram of another conventional helium liquefaction refrigeration apparatus.

FIG. 7 is a system diagram of another helium liquefaction refrigeration apparatus.

FIG. 8 is a system diagram of another helium liquefaction refrigeration apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Circulating compressor 1a ... Return line 2 ... Heat exchanger group 4 ... Cryostat 6 ... Emergency discharge valve 21,4
6 Helium recovery container 22, 32, 45 Ejector 23 Flow control valve 24, 53 Pressure indicating controller 25 Recovery valve
26 ... Controller 31 ... Low temperature helium recovery container 37 ... Liquid level indicator controller 41 ... Expansion turbine 42 ... Liquefied helium container 43 ... Immersion heat exchanger 4
4: Cooling coil

Claims (4)

(57) [Claims] 1. A helium liquefaction refrigeration system for cooling, expanding, and liquefying circulating helium compressed by a circulating compressor to cool an object to be cooled, wherein a pressure in the cooling unit is applied to a cooling part of the object to be cooled. A helium recovery container is connected via a valve and a heater that opens when the ascent rises, and a part of the circulating helium is used as a drive source to maintain the inside of the helium recovery container during normal operation in a reduced pressure state. A helium liquefaction refrigeration system comprising an ejector. 2. The helium liquefaction refrigeration apparatus according to claim 1, wherein a branch path for providing a part of the compressed helium gas as a drive source of the ejector is provided on the discharge side of the circulating compressor, and the branch path is provided after the ejector is led out. A path for circulating the helium gas to the suction side of the compressor is provided, and a flow control valve for adjusting a branch amount of the compressed helium gas serving as a drive source of the ejector according to the pressure in the helium recovery container is provided. Helium liquefaction refrigeration equipment. 3. A helium liquefaction refrigeration system that cools, cools, expands and liquefies circulating helium compressed by a circulating compressor to cool the object to be cooled. The low-temperature helium recovery container is connected via a valve that opens when the temperature rises, and the low-temperature helium recovery is performed using the circulating helium as a drive source through a valve that closes when the pressure in the cooling unit increases. A helium liquefaction refrigeration apparatus, comprising: an ejector for reducing the pressure in a vessel; and a path for supplying a part of the liquefied helium to the low-temperature helium recovery vessel. 4. A helium liquefaction refrigeration system for cooling, expanding, and liquefying circulating helium compressed by a circulating compressor to cool an object to be cooled, in which helium after cooling is expanded so as to have a critical pressure or higher. A turbine, a path for further cooling the expanded helium by liquefied helium in the liquefied helium container and supplying the cooled helium to the cooling unit of the cooled object, and when the pressure in the cooling unit increases a part of the expanded helium in the cooling unit. A path for supplying liquefied helium into the liquefied helium container via a valve that opens to the helium that has been led out of the cooling section of the object to be cooled is expanded by an ejector via a valve that closes when the pressure in the cooling section increases. A helium collection container connected to the cooling unit via a valve that opens when the pressure in the cooling unit rises, and a pressure in the cooling unit. A path for supplying a portion of the liquefied helium in the liquefied helium container into the helium recovery container via a valve that closes when the force increases, and a valve that closes when the pressure in the cooling unit increases A helium liquefaction refrigeration apparatus, wherein a path connecting the inside of the helium recovery container and the suction side of the ejector is provided through