JP2008113893A - Operation method of superconducting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an operation method of a superconducting apparatus capable of surely cooling a superconducting member even to a cooling temperature range which liquid nitrogen cannot create. <P>SOLUTION: This operation method is for the superconducting apparatus (MRI 1) using the superconducting member (a superconducting magnet 11). Oxygen is used as a refrigerant for cooling the superconducting member 11; liquid oxygen liquified by cooling the oxygen to a range of the boiling point or more of nitrogen and less than the boiling point of oxygen, or a range higher than the temperature of the freezing point of oxygen and the freezing point or less of the nitrogen, is supplied to the superconducting apparatus 1 and to operate the superconducting apparatus 1 while cooling the superconducting member 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for operating a superconducting device. In particular, the present invention relates to a method of operating a superconducting device while cooling a superconducting member used in the superconducting device to a cryogenic temperature.

  Superconducting devices such as MRI and superconducting motors equipped with superconducting magnets use liquid nitrogen (freezing point of about 63K) and liquid helium (λ point of about 2.18K) to cool the superconducting member. In addition, liquid air (freezing point of about 57k) and a mixed liquid refrigerant of liquid nitrogen and liquid oxygen are used as cooling refrigerants for superconducting members because they have a lower freezing point than liquid nitrogen (for example, (See Patent Document 1).

JP 2001-174114 A

  It is known that the superconducting member has higher current density and lower critical current characteristics as the cooling temperature is lower. In addition, some superconducting members can obtain a desired current density even when used in a relatively high-temperature atmosphere. With such a high-temperature superconducting member, a heat insulating structure as a cooling structure can be simplified and the cost can be reduced. Can be achieved.

  However, since liquid nitrogen has a high freezing point of about 63K, the current density may not be sufficiently increased. Also, since liquid nitrogen has a boiling point as low as about 77K, when it is desired to cool the superconducting member at a temperature higher than the boiling point of liquid nitrogen, the liquid nitrogen is vaporized, the cooling capacity is lowered, and the predetermined cooling temperature is ensured. There are also problems that cannot be maintained. Further, when nitrogen becomes a solid refrigerant, the refrigerant does not enter a small gap in the device, so that cooling cannot be performed sufficiently.

  Liquid helium can cool a superconducting member to a considerably low temperature, but there are problems such as an increase in system size and cost for cooling to that temperature. In addition, helium has a fairly low boiling point of about 4K, so when it is cooled at a high temperature, it becomes a cooling with a gas and the cooling capacity is lowered.

  Liquid air or a mixed liquid refrigerant of liquid oxygen and liquid nitrogen can lower the cooling temperature compared to liquid nitrogen, but the liquid nitrogen evaporates first, resulting in a higher liquid oxygen concentration, which is safer. In view of this, there are problems such as difficulty in managing the liquid oxygen concentration.

  Liquid oxygen has a freezing point of about 54K, which is considerably lower than the freezing point of liquid nitrogen, and its boiling point is about 90K, which is higher than the boiling point of liquid nitrogen. In addition, the high-temperature superconducting member may obtain a desired current density while being cooled at a relatively high temperature, or may be used by raising the current density by considerably reducing the cooling temperature. Therefore, the liquid oxygen can be used for the purpose of cooling the superconducting member. However, when the superconducting member is cooled only by the liquid oxygen, it has not been put into practical use because of the risk of explosion.

  However, in recent years, liquid oxygen has been stored in a liquid oxygen tank for use in inhaling oxygen to patients in hospitals, and is stored in hospitals or lives in a sealed space such as a submarine for a long time. As a necessary oxygen, a liquid oxygen tank is installed and stored in a ship, and the safety of these liquid oxygen tank and liquid oxygen supply piping equipment has been ensured.

  Further, in hospitals, devices equipped with superconducting members such as MRI and a small accelerator for heavy ion irradiation are used. These superconducting devices usually cool the superconducting member with liquid helium. However, in order to hold the liquid helium in a liquid state, a cooling system that maintains a predetermined temperature is required. This cooling system is considerably increased in size because the heat insulation structure is complicated.

  In addition, in order to supply electric power to the ship, it has been attempted to generate power using a superconducting generator that can be downsized but have a large output, and to use a superconducting motor as a propulsion motor. However, this superconducting generator or the like is usually configured to cool with liquid nitrogen or liquid hydrogen, and stores a large amount of the above-described liquid refrigerant in a limited space such as a submarine, or a large circulation refrigeration system There are restrictions on the provision of the heat and cooling costs.

  Also, in steelworks, oxygen is generally refined by injecting it into a converter, and an oxygen production apparatus is provided near the converter. Examples of the oxygen production apparatus include a liquid air separation apparatus that takes out liquid oxygen from liquid air and gasifies the liquid oxygen. And the oxygen gas obtained with the oxygen production apparatus is supplied into the converter. In the oxygen production apparatus, motors are used for the compressors, and by using these motors as superconducting motors, there is an advantage that they can be miniaturized, have high efficiency, and can have a large electric capacity.

  An object of the present invention is to provide a method of operating a superconducting device that can reliably cool a superconducting member even in a cooling temperature range that cannot be handled by liquid nitrogen. In addition, as another object, using existing liquid oxygen equipment, the liquid oxygen stored in this equipment is used for cooling the superconducting member, while reducing the cost while cooling the superconducting member according to the purpose. The operation method of the superconducting equipment which performs is provided.

  The operation method of the superconducting equipment using the superconducting member of the present invention uses liquid oxygen cooled to a range not less than the boiling point of nitrogen and less than the boiling point of oxygen as a refrigerant for cooling the superconducting member, and the superconducting member is cooled with this liquid oxygen. And operating a superconducting device.

  Further, another operation method of superconducting equipment using the superconducting member of the present invention uses liquid oxygen cooled to a temperature higher than the freezing point of oxygen and below the freezing point of nitrogen as a refrigerant for cooling the superconducting member. The superconducting member is cooled with liquid oxygen and the superconducting device is operated.

  That is, the present invention does not use a refrigerant in which a plurality of components are mixed, but cools the superconducting member with liquid oxygen alone, and by setting the temperature of the liquid oxygen within the above range, the current density of the superconducting member is reduced. When it is desired to increase the temperature, the superconducting member is cooled in the temperature range on the low temperature side, and when the superconducting member can be cooled at a relatively high temperature, the superconducting member is cooled in the temperature range on the high temperature side.

  Liquid oxygen can be obtained, for example, by removing nitrogen, argon and other impurities from liquid air, or it can be obtained by decomposing water and then liquefying oxygen. The method of obtaining liquid oxygen is not limited to these.

  Liquid oxygen has a wide temperature range in liquid and can cool the superconducting member at a low temperature below the freezing point of liquid nitrogen. Moreover, since liquid oxygen has a larger latent heat of vaporization and a limit heat flux of nucleate boiling than liquid nitrogen, the cooling capacity is superior to liquid nitrogen also in this respect. Furthermore, oxygen is paramagnetic, has a high magnetic susceptibility, and is attracted to a high magnetic field region. Therefore, when cooling a superconducting member, liquid oxygen can be concentrated and cooled in a high magnetic field region where heat generation is large. As a result, partial cooling effect can be obtained.

  As liquid oxygen used in the operation method of the present invention, liquid oxygen used in existing facilities excluding superconducting equipment can be used. The liquid oxygen is preferably stored in a liquid oxygen tank, and liquid oxygen is preferably supplied from the liquid oxygen tank to the superconducting device.

  Liquid oxygen used in existing facilities means, for example, liquid oxygen that is used in hospitals to liquefy oxygen used for treatment of patients in hospital rooms and stored in the liquid oxygen tank, or liquid oxygen tanks installed in submarines And liquid oxygen stored in the water.

  Liquid oxygen stored in a liquid oxygen tank installed in a hospital is used as a gas when it is used for treatment of patients in a hospital room, etc., so the liquid oxygen is gasified by cooling the superconducting member for treatment, etc. Can be used. Further, since liquid oxygen in the liquid oxygen tank mounted on the submarine is also gasified and supplied to the ship, the superconducting member can be cooled with liquid oxygen to gasify the liquid oxygen.

  In this way, by using the existing liquid oxygen to cool the superconducting member, the cooling cost of the superconducting equipment can be reduced.

  Furthermore, the operation method of the superconducting equipment using the superconducting member of the present invention uses a mixture of oxygen and argon as a refrigerant for cooling the superconducting member, cools the mixture of oxygen and argon, and uses a liquefied mixture of oxygen and argon. It is also possible to operate the superconducting equipment by cooling the superconducting member.

  A mixture of liquid oxygen and liquid argon also has a freezing point similar to that of liquid oxygen when the concentration of argon is low. Also, liquid oxygen and liquid argon are close to the boiling point (oxygen about 90K, argon about 87K) and have a small density difference, so they are difficult to separate and easy to use as a mixed liquid refrigerant.

  The mixing ratio of the mixture of liquid oxygen and liquid argon is preferably such that the concentration of liquid oxygen is 80 mol% or more and the concentration of liquid argon is 20 mol% or less. When the concentration of liquid argon exceeds 20 mol%, the freezing point increases.

  A mixture of liquid oxygen and liquid argon can be produced by separating nitrogen and impurities from liquid air obtained by liquefying air. After producing liquid air by liquefying air, a mixture of liquid oxygen and liquid argon can be easily produced by removing impurities and gasifying and separating liquid nitrogen. In this case, since air is 78.10% by volume of nitrogen, 20.9% by volume of oxygen, and 0.94% by volume of argon, the mixing ratio of the mixture of liquid oxygen and liquid argon is that the concentration of liquid oxygen is 95.7 mol% and the concentration of liquid argon is 4.3 mol%. The freezing point of this mixed liquid refrigerant is about the same as that of liquid oxygen, and a freezing point similar to that of liquid oxygen can be obtained without removing argon. Therefore, the current density of the superconducting member can be increased while reducing the manufacturing cost. be able to.

  In addition, as a superconducting apparatus using a superconducting member, an MRI equipped with a superconducting magnet, a linear motor, a superconducting generator, a transformer, a current limiter, an ion accelerator, and the like can be given.

  The operation method of the superconducting equipment using the superconducting member of the present invention uses liquid oxygen cooled to a range not less than the boiling point of nitrogen and less than the boiling point of oxygen as a refrigerant for cooling the superconducting member, and the superconducting member is cooled with this liquid oxygen. Therefore, when the high-temperature superconducting member is used in a superconducting device, the superconducting member can be cooled at a relatively high temperature that could not be cooled with liquid nitrogen. As a result, by cooling the superconducting member in the above high temperature range, the heat insulating structure as a cooling structure can be simplified, and the cost of the cooling system can be reduced.

  Further, another operation method of superconducting equipment using the superconducting member of the present invention uses liquid oxygen cooled to a temperature higher than the freezing point of oxygen and below the freezing point of nitrogen as a refrigerant for cooling the superconducting member. Since the superconducting member is cooled with liquid oxygen, the superconducting member can be cooled at a considerably low temperature. Therefore, the current density of the superconducting member can be increased.

  Hereinafter, an embodiment of a method for operating a superconducting device of the present invention will be described.

<First Embodiment>
FIG. 1 is a schematic configuration diagram of a superconducting device according to a first embodiment of a method of operating a superconducting device of the present invention.

The superconducting device according to the present embodiment is an MRI (magnetic
resonance imaging) 1, MRI1 has a superconducting magnet 11 inside, and MRI1 communicates with liquid oxygen tank 13 through supply pipe 12, while oxygen gas is supplied to the outside hospital room through discharge pipe 14 It is supposed to be.

  In the liquid oxygen tank 13, liquid oxygen used for supplying to the patient is stored. The supply pipe 12 communicates with the superconducting magnet 11 of the MRI 1 and the liquid oxygen tank 13, and a pump 15 is provided in the middle of the supply pipe 12.

  In the present embodiment, by driving the pump 15, liquid oxygen is supplied from the liquid oxygen tank 13 to the superconducting magnet 11 via the supply pipe 12, and the superconducting magnet 11 is cooled with this liquid oxygen. Then, while this superconducting magnet 11 is cooled, liquid oxygen is gasified and oxygen gas is sent from the discharge pipe 14 to the hospital room.

  In the present embodiment, the liquid oxygen is cooled in a range that cannot be cooled in a liquid state with liquid nitrogen, that is, in a range that is higher than the boiling point of nitrogen and lower than the boiling point of oxygen, or higher than the temperature of the freezing point of oxygen. Cool to the range below the freezing point.

  In this embodiment, liquid oxygen is used for cooling the superconducting magnet 11 of MRI1, and oxygen gasified by this cooling is used for treatment of a patient. In this embodiment, since the superconducting magnet 11 of MRI1 can be cooled using liquid oxygen stored in a hospital, the cooling cost can be reduced.

<Second Embodiment>
FIG. 2 is a schematic configuration diagram of the superconducting device according to the second embodiment of the method of operating the superconducting device of the present invention.

  The superconducting device according to this embodiment is a superconducting motor 2 for propulsion arranged inside a submarine, the superconducting motor 2 includes a superconducting magnetic field coil 21, and the superconducting motor 2 is connected to a liquid oxygen tank via a supply pipe 22. While communicating with 23, it is supplied to the ship through the discharge pipe 24.

  In the liquid oxygen tank 23, oxygen necessary for respiration of workers working on the ship is liquefied and stored. The supply pipe 22 communicates the superconducting magnetic field coil 21 of the superconducting motor 2 and the liquid oxygen tank 23, and a pump 25 is provided in the middle of the supply pipe 22.

  Also in this embodiment, by driving the pump 25, liquid oxygen is supplied from the liquid oxygen tank 23 to the superconducting magnetic field coil 21 via the supply pipe 22, and the superconducting magnetic field coil 21 is cooled with this liquid oxygen. Then, while the superconducting magnetic field coil 21 is cooled, liquid oxygen is gasified, and oxygen gas is discharged from the discharge pipe 14 into the submarine.

  Also in this embodiment, liquid oxygen is cooled in a range that cannot be cooled in a liquid state with liquid nitrogen, in a range higher than the boiling point of nitrogen and lower than the boiling point of oxygen, or higher than the temperature of the freezing point of oxygen, Cool to the range below the freezing point.

  In the present embodiment, liquid oxygen is used to cool the superconducting magnetic field coil 21 of the superconducting motor 2, and oxygen gasified by this cooling is supplied into the ship. In this embodiment, the superconducting magnet 11 of the MRI 1 can be cooled using liquid oxygen stored in the submarine, so that the cooling cost can be reduced.

  In addition, the superconducting motor 2 of the present embodiment can obtain a large output while being small. The superconducting motor includes, for example, a rotating body connected to the rotating shaft of the blade, an armature coil disposed around the rotating body, and a magnetic shield disposed on the outer periphery of the armature coil. A cooling chamber in which a liquid refrigerant is filled in the center of the body and a superconducting field coil is arranged around the outer periphery of the cooling chamber.

<Third Embodiment>
FIG. 3 is a schematic configuration diagram of the superconducting device according to the third embodiment of the method of operating the superconducting device of the present invention.

  The superconducting device according to the present embodiment is a superconducting motor 41a of a compressor 41 provided in the liquid air separation device 3 installed in, for example, a steel mill, and the superconducting motor 41a is not shown, but includes a superconducting magnetic field coil. Prepare. In the present embodiment, the superconducting motor 41a is cooled using liquid oxygen produced by the liquid air separation device 3 or a mixed liquid refrigerant of liquid oxygen and liquid argon.

  The liquid air separation device 3 includes an air supply unit 42 that supplies air (gas), a compressor 41 that compresses the air to liquefy, a liquid air storage unit 43 that stores liquefied liquid air, and liquid air A mixed liquid refrigerant storage unit 44 that stores a mixed liquid refrigerant of liquid oxygen and liquid argon separated from liquid nitrogen, and a liquid oxygen storage unit 45 that further separates liquid argon from the mixed liquid refrigerant and stores liquid oxygen Is provided.

  The liquid air stored in the liquid air storage unit 43 is heated to generate nitrogen gas first to separate the liquid nitrogen, thereby producing a mixed liquid refrigerant of liquid oxygen and liquid argon. Then, the mixed liquid refrigerant is stored in the mixed liquid refrigerant storage unit 44, and further, the mixed liquid refrigerant is heated to gasify only liquid argon to obtain liquid oxygen. This liquid oxygen is stored in the liquid oxygen storage unit 45.

  The mixed liquid refrigerant or liquid oxygen is used to cool the superconducting motor 41a of the compressor 41. The superconducting motor 41a communicates with the liquid oxygen reservoir 45 via the first supply pipe 51 and with the mixed liquid refrigerant reservoir 44 of liquid oxygen and liquid argon via the second supply pipe 52. A pump 55 is provided in the middle of the first supply pipe 51 and the second supply pipe 52. The superconducting motor 41a communicates with the oxygen gas reservoir 46 through the first exhaust pipe 53 and with the mixed gas refrigerant reservoir 47 of oxygen gas and argon gas through the second exhaust pipe 54.

  Then, the oxygen gas or the mixed gas refrigerant of oxygen gas and argon gas after cooling the superconducting motor 41a is supplied again to the air supply unit 42 to be liquefied.

  In the third embodiment, liquid oxygen obtained by the liquid air separation device 3 or the mixed liquid refrigerant is used for cooling the superconducting motor 41a. Further, the liquid oxygen or the mixed liquid refrigerant can be used other than the cooling of the superconducting motor 41a as in the first embodiment and the second embodiment described above.

  Further, the oxygen gas and the mixed gas refrigerant gasified after cooling the superconducting motor 41a can be liquefied again and used for cooling the superconducting motor 41a and other applications. Also, oxygen gas and mixed gas refrigerant can be used for other applications.

  In the present embodiment, the superconducting motor 41a is cooled using the liquid oxygen produced by the liquid air separation device 3 or the liquid refrigerant of liquid oxygen and liquid argon, so the cost of the system for cooling the superconducting motor 41a is reduced. Can be planned.

  And since the freezing point of the mixed liquid refrigerant is about the same as that of liquid oxygen, it is possible to obtain a freezing point similar to liquid oxygen without removing argon, so when using the mixed liquid refrigerant for cooling the superconducting motor 41a. The current density of the superconducting member can be increased while the manufacturing cost of the refrigerant can be reduced.

  In the present embodiment, since the motor of the compressor 41 provided in the liquid air separation device 3 is the superconducting motor 41a, it is possible to obtain a desired compression capacity while being lightweight and downsized. In addition, although not shown, a generator that supplies power to each device provided in the liquid air separation device 3 is a superconducting generator, and the superconducting magnetic coil of this generator is separated by the liquid air separation device 3. It can also be cooled with oxygen or a mixed liquid refrigerant. By using a superconducting generator, the power generation efficiency is greatly improved.

  The method for operating a superconducting device of the present invention is suitable when a superconducting device is used near an existing facility using liquid oxygen.

FIG. 2 is an explanatory diagram showing an outline of a configuration in which an MRI is used as a superconducting device and a superconducting member of the MRI is cooled in the first embodiment relating to the operation method of the superconducting device of the present invention. In 2nd Embodiment which concerns on the operating method of the superconducting apparatus of this invention, it is explanatory drawing which shows the outline of the structure which uses a superconducting motor as a superconducting apparatus and cools the superconducting member of this superconducting motor. It is explanatory drawing which shows the outline of a structure of the liquid air separation apparatus which has the superconducting motor which is 3rd Embodiment which concerns on the operating method of the superconducting apparatus of this invention.

Explanation of symbols

1 MRI 11 Superconducting magnet 12 Supply piping
13 Liquid oxygen tank 14 Discharge piping 15 Pump
2 Superconducting motor 21 Superconducting magnetic field coil 22 Supply piping
23 Liquid oxygen tank 24 Discharge piping 25 Pump
3 Liquid air separator
41 Compressor 41a Superconducting motor
42 Air supply section 43 Liquid air storage section 44 Mixed liquid refrigerant storage section
45 Liquid oxygen reservoir 46 Oxygen gas reservoir 47 Mixed gas refrigerant reservoir
51 First supply pipe 52 Second supply pipe
53 First discharge pipe 54 Second discharge pipe
55 Pump

Claims (5)

A method of operating a superconducting device using a superconducting member,
The superconducting device is characterized in that as a refrigerant for cooling the superconducting member, liquid oxygen cooled to a range not lower than the boiling point of nitrogen and lower than the boiling point of oxygen is used, and the superconducting member is operated by cooling the superconducting member with this liquid oxygen. how to drive. A method of operating a superconducting device using a superconducting member,
As the refrigerant for cooling the superconducting member, liquid oxygen that is cooled to a temperature higher than the freezing point of oxygen and below the freezing point of nitrogen is used, and the superconducting member is cooled with this liquid oxygen to operate the superconducting device. How to operate superconducting equipment.   The method for operating a superconducting device according to claim 1 or 2, wherein liquid oxygen used in existing facilities excluding the superconducting device is used. A method of operating a superconducting device using a superconducting member,
As a refrigerant for cooling the superconducting member, a mixture of oxygen and argon is used,
A method of operating a superconducting device, wherein a superconducting device is operated by cooling a mixture of oxygen and argon, cooling a superconducting member with a liquefied mixture of oxygen and argon.   The method of operating a superconducting device according to claim 4, wherein the mixture of liquid oxygen and liquid argon is produced by separating nitrogen and impurities from liquid air obtained by liquefying air.

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