EP1087195A2

EP1087195A2 - Refrigerator for cryogenic gas separation system

Info

Publication number: EP1087195A2
Application number: EP00120673A
Authority: EP
Inventors: Atsushi Air Water Inc. Miyamoto; Shingo Air Water Inc. Kunitani
Original assignee: Air Water Inc
Current assignee: Air Water Inc
Priority date: 1999-09-24
Filing date: 2000-09-21
Publication date: 2001-03-28
Anticipated expiration: 2020-09-21
Also published as: JP2001091079A; ES2273642T3; ATE346271T1; DE60031931D1; EP1087195B1; KR100647965B1; JP3584186B2; EP1087195A3; TW477891B; KR20010067201A; CN1290845A; CN1158514C; DE60031931T2

Abstract

A cryogenic gas separation system which comprises a refrigerator and utilizes cold produced by the refrigerator as a cold source for separation of a gas. The refrigerator incorporates a rotary valve which comprises a rotary element rotatable about an axis thereof and having a circular cross section perpendicular to the axis, and a housing accommodating the rotary element in a rotatable manner. The rotary element has a plurality of ports provided in an outer peripheral portion thereof, the housing having a plurality of ports provided in a peripheral wall thereof in association with the ports of the rotary element, the rotary valve being operative to be switched between a position where predetermined ones of the ports of the rotary element are aligned with corresponding ones of the ports of the housing for communication therebetween and a position where the predetermined ones of the ports of the rotary element are displaced in non-alignment with the corresponding ones of the ports of the housing for non-communication therebetween by rotation of the rotary element. The valve incorporated in the refrigerator has a smaller size and an extended service, and the cryogenic gas separation system can obtain a sufficient amount of cold with the use of the refrigerator.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates generally to a cryogenic gas separation system which utilizes cold produced by a refrigerator.

Description of Related Art

Cryogenic air separation systems utilizing a compact helium (He) refrigerator are disclosed in Japanese Patent Unexamined Publications No. 10-206009 (1998) and No. 10-206010 (1998) and Japanese Patent No. 3007581. For driving such a compact refrigerator typified by a pulse tube refrigerator for these cryogenic air separation systems, a pressure pulsation source is required and, in some cases, a phase controller is required. The pressure pulsation source and the phase controller each have valves for controlling the flow of an operating gas. Referring to Fig. 24, an active buffer pulse tube refrigerator, for example, includes a pressure pulsation source having a compressor 91 and a pair of valves 93, 94, and a phase controller having two buffer tanks 92a, 92b and a pair of valves 95, 96. In Fig. 24, reference numerals 97 and 98 denote a regenerator and a pulse tube, respectively.
The valves 93 to 96 are each opened and closed in a precisely predefined cycle. The open-close cycle is relatively short, which typically provides pressure pulsation of several hertz to several tens hertz. Therefore, a solenoid valve or a compact flat seal rotary valve as shown in section in Fig. 25 is generally employed for the valves 93 to 96. The flat seal rotary valve includes a rotary element 101 having two ports 102, 103 (which communicate with each other via a communication path 104), and a stationary element 105 having three ports 106 to 108 and kept in area Contact with the rotary element 101. The rotary element 101 is adapted to be rotated with respect to the stationary element 105 by rotation of a motor 109 so that the ports 102, 103 are selectively connected to the ports 106 to 108 (the port connection is switched between a position where the ports 107, 108 of the stationary element 105 communicate with each other as shown in Fig. 25 and a position where the ports 106, 107 of the stationary element 105 communicate with each other as shown in Fig. 26). Thus, the flat seal rotary valve shown in Fig. 25 is capable of switching the flow path of the operating gas in two ways. Therefore, it is merely necessary to provide such rotary valves one for each of the pressure pulsation source and the phase controller. In Figs. 25 and 26, reference numeral 110 denotes a housing which accommodates the rotary element 101 in a rotatable manner.
For realization of a larger-scale and higher-efficiency refrigerator, a larger volume of the operating gas, a higher operating frequency and a complicated phase controller are required. In consideration of the marketability of such a refrigerator, it is desirable to employ a selector valve having a compact size and a long service life for the refrigerator and to satisfy the aforesaid requirements. However, conventional selector valves typified by the solenoid valve and the flat seal rotary valve shown in Fig. 25 cannot satisfy the aforesaid requirements, making it impossible to realize a larger-scale and higher-efficiency refrigerator.
More specifically, where a solenoid valve is employed as the selector valve, the valve tends to have a complicated construction and an increased size in an attempt to increase the volume of the operating gas, so that high speed operation of the valve is difficult. If the valve is frequently operated at a higher speed, the service life of the valve will drastically be reduced. Where a phase controller is incorporated in the refrigerator, the number of valves should be increased for the complicated construction of the phase controller, so that the overall size of the refrigerator is increased.
Where a flat seal rotary valve is employed as the selector valve, it is necessary to increase the diameters of the rotary element 101 and the stationary element 105 in an attempt to increase the port diameter for passage of a larger volume of the operating gas or to increase the number of ports for the complicated construction of the phase controller. Therefore, the contact areas of the rotary element 101 and the stationary element 105 are increased. Since a pressure exerted on the rotary element 101 is increased correspondingly to the increase in the contact area of the rotary element 101 and the stationary element 105, a motor capable of providing a greater torque should be employed as the motor 109. This increases the overall size of the valve. For this reason, only a smaller-scale refrigerator, having a cryogenic capacity on the order of several watts, has hitherto been developed.
Therefore, in an air separation unit employing a conventional smaller-scale refrigerator, the amount of cold produced is insufficient, so that an expansion turbine or the like should be employed as an auxiliary cold source. This results in a cost increase.
In view of the foregoing, it is an object of the present invention to provide a cryogenic gas separation system supplied with a sufficient amount of cold by employing a refrigerator incorporating a compact and longer-life selector valve.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention to achieve the aforesaid object, there is provided a cryogenic gas separation system which comprises a refrigerator and utilizes cold produced by the refrigerator as a cold source for separation of a gas, the refrigerator incorporating a rotary valve which comprises a rotary element rotatable about an axis thereof and having a circular cross section perpendicular to the axis, and a housing accommodating the rotary element in a rotatable manner, the rotary element having a plurality of ports provided in an outer peripheral portion thereof, the housing having a plurality of ports provided in a peripheral wall thereof in association with the ports of the rotary element, the rotary valve being operative to be switched between a position where predetermined ones of the ports of the rotary element are aligned with corresponding ones of the ports of the housing for communication therebetween and a position where the predetermined ones of the ports of the rotary element are displaced in non-alignment with the corresponding ones of the ports of the housing for non-communication therebetween by rotation of the rotary element.
In accordance with a second aspect of the present invention, there is provided a cryogenic gas separation system which comprises a refrigerator and utilizes cold produced by the refrigerator as a cold source for separation of a gas, the refrigerator incorporating a rotary valve which comprises a rotary element rotatable about an axis thereof and having a circular cross section perpendicular to the axis, and a housing accommodating the rotary element in a rotatable manner, the rotary element having a recess provided in an outer peripheral portion thereof, the housing having a plurality of ports provided in a peripheral wall thereof in association with the recess, the rotary valve being operative to be switched between a position where the recess is aligned with the ports for communication therebetween and a position where the recess is displaced in non-alignment with the ports for non-communication therebetween by rotation of the rotary element.
The first cryogenic gas separation system according to the present invention utilizes the cold produced by the refrigerator as the cold source for gas separation, and the refrigerator employs the rotary valve which has the plurality of ports provided in the outer peripheral portion of the rotary element (rotatable about the axis thereof and having the circular cross section perpendicular to the axis), and the plurality of ports provided in the peripheral wall of the housing (accommodating the rotary element in a rotatable manner). Since the plurality of ports of the rotary valve incorporated in the refrigerator are axially independently provided, an increase in the diameter of the rotary element is minimized, even if the diameter and number of the ports are increased. This allows the rotary valve to have a reduced size and an extended service life. As a result, the diameter and number of the ports can more easily be increased in the rotary valve than in the conventional solenoid valve and flat seal rotary valve, so that the refrigerator is allowed to have a larger scale, a greater capacity and a higher efficiency. For example, the refrigerator can be embodied as a larger-scale refrigerator having a wattage of not smaller than several hundreds watts. Of course, the refrigerator may be embodied as a smaller-scale refrigerator having a wattage of several watts as in the prior art. The larger-scale, greater-capacity and higher-efficiency refrigerator makes it possible to operate the first cryogenic gas separation system without the use of any auxiliary means such as an auxiliary cold source, thereby allowing for a cost reduction. In the second cryogenic gas separation system, the refrigerator has the same features and effects as the refrigerator employed in the first cryogenic gas separation system. Therefore, the second cryogenic gas separation system also can achieve a cost reduction like the first cryogenic gas separation system. The refrigerators to be employed in the first and second cryogenic gas separation systems may be of pulse tube type, G-M (Gifford-McMahon) type, or Solvay type, but are not limited thereto. The refrigerators may be embodied as any type of refrigerator, as long as the refrigerator is designed so that flow paths of an operating gas are switched by switching a valve. In the present invention, the rotary element has a circular cross-section perpendicular (or normal) to the rotary axis of the element. In other words, the horizontal cross section of the rotary element is circular when the rotary element is placed vertically upright and the vertical cross section of the rotary element is circular when the same rotary element is laid horizontally.
The foregoing and other objects, features and effects of the present invention will become more apparent from the following description with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a diagram illustrating the construction of a rotary valve employed in a cryogenic gas separation system according to the present invention;
Figs. 2 and 3 are diagrams showing the operation of the rotary valve of Fig. 1;
Fig. 4 is a diagram showing a pulse tube refrigerator employing a rotary valve;
Fig. 5 is a diagram illustrating the cryogenic gas separation system;
Fig. 6 is a diagram illustrating a refrigerator employed in the cryogenic gas separation system in accordance with one embodiment of the present invention;
Fig. 7 is a perspective view of a rotary element employed for a rotary valve;
Figs. 8 and 9 are diagrams showing the operation of the rotary valve employing the rotary element of Fig. 7;
Fig. 10 is a perspective view illustrating a modification of the rotary element of Fig. 7;
Fig. 11 is a diagram illustrating the construction of a rotary valve employing the rotary element of Fig. 10;
Fig. 12 is a diagram illustrating a refrigerator employed in the cryogenic gas separation system in accordance with another embodiment of the present invention;
Fig. 13 is a perspective view illustrating a rotary element employed for a rotary valve;
Figs. 14 and 15 are diagrams showing the operation of the rotary valve employing the rotary element of Fig. 13;
Fig. 16 is a perspective view illustrating a modification of the rotary element of Fig. 13;
Figs. 17 and 18 are diagrams illustrating the construction of a rotary valve employing the rotary element of Fig. 16;
Fig. 19 is a diagram illustrating a refrigerator employed in the cryogenic gas separation system in accordance with further another embodiment of the present invention;
Fig. 20 is a sectional view illustrating a rotary valve to be employed for the refrigerator of Fig. 19;
Figs. 21 through 23 are diagrams showing the operation of the rotary valve of Fig. 20;
Fig. 24 is a diagram illustrating a conventional pulse tube refrigerator;
Fig. 25 is a diagram illustrating a conventional flat seal rotary valve; and
Fig. 26 is a diagram showing the operation of the flat seal rotary valve of Fig. 25.

DETAILED DESCRIPTION OF THE INVENTION

With reference to Fig. 1, a detailed explanation will be given to the construction, operation and effects of a rotary valve incorporated in a refrigerator to be employed in a cryogenic gas separation system according to the present invention. The rotary valve, which is designated by a reference character A in its entirety, includes a cylindrical rotary element 1 rotatable about an axis thereof, a hollow cylindrical housing 2 accommodating the rotary element 1 in a rotatable manner, a pair of bearings 3, 3 rotatably supporting the rotary element 1, and a motor 4 for rotating the rotary element 1 in one direction. The rotary element 1 has four pairs of ports 5 to 12 in a circumferential wall thereof (a pair of ports 5, 6, a pair of ports 7, 8, a pair of ports 9, 10, and a pair of ports 11, 12, the ports of each pair communicating with each other via communication paths 13, 14, 15 and 16, respectively). The housing 2 has six ports 17 to 22 formed in a circumferential wall thereof in association with the four pairs of ports 5 to 12 (the port 17 associates with the port 5; the port 18 associates with the ports 6, 9; the port 19 associates with the port 10; the port 20 associates with the port 7; the port 21 associates with the port 11; and the port 22 associates with the ports 8, 12). In a position as shown in Fig. 1, the ports 5, 6, 7 and 8 of the rotary element 1 communicate with the ports 17, 18, 20 and 22 of the housing 2, respectively, while the other ports 9 to 12, 19 and 21 are out of communication. When the rotary element 1 is rotated into the position as shown in Fig. 2, the ports 9, 10, 11 and 12 of the rotary element 1 communicate with the ports 18, 19, 21 and 22 of the housing 2, respectively, while the other ports 5 to 8, 17 and 20 are out of communication. When the rotary element 1 is rotated into the position as shown in Fig. 3, all the ports 17 to 22 are out of communication.
The rotary element 1 may have either a hollow cylindrical shape or a solid cylindrical shape. The rotation of the rotary element 1 may be achieved by any of various means other than the motor 4. A recess (see Fig. 7) may be formed instead of each of the four pairs of the ports 5 to 12. Further, the pairs of ports 5 to 12 are not necessarily required to be located adjacent each other. The ports 17 to 22 are not necessarily required to be located on the same side of the housing 2. Although the bearings 3, 3 are located at opposite ends of the rotary element 1, a single bearing may be provided at one of the opposite ends of the rotary element 1. Usable as the bearings 3, 3 are rolling bearings and common bearings such as slide bearings. The motor 4 may be of reversibly rotatable type. The motor 4 may be adapted to be rotated either constantly or in an intermittent variable manner.
A pulse tube refrigerator 121 as shown in Fig. 4 is different from the pulse tube refrigerator shown in Fig. 24 in that a single rotary valve B (having substantially the same construction as the rotary valve A shown in Fig. 1) is employed instead of the four valves 93 to 96. However, the configuration, number and the like of the ports 5 to 12 and 17 to 22 of the rotary valve B are different from those of the rotary valve A because the rotary valve B should perform the same function as the valves 93 to 96 of a conventional refrigerator such as shown in Fig. 24.
Since the rotary element 1 of the rotary valves A, B has a smaller diameter and hence a smaller cross section, the influence of a pressure load exerted on the rotary element 1 can be minimized. Where a seal (not shown in Figs. 1 to 3) is provided between the rotary element 1 and the housing 2, torque generated by friction of the seal can be reduced, because the circumferential speed of the outer diameter of the rotary element 1 is reduced. The reduction in the pressure load and the torque generated by the friction of the seal reduces the power required for the rotation of the motor 4. As a result, a compact and high-speed motor can be employed as the motor 4. Further, the reduction in the circumferential speed of the rotary element 1 makes it possible to extend the service life of the seal (which is provided between the rotary element 1 and the housing 2) and to increase the rotational speed of the rotary element 1.
Since loads axially and radially exerted on the rotary element 1 are received by the bearings 3, the load exerted on the motor 4 is reduced, whereby the power required for the rotation of the motor 4 can be minimized. The pressure load exerted on the rotary element 1 is further reduced by the bearings which support the rotary element 1. This allows for size reduction of the rotary element 1 and the motor 4, so that the overall sizes of the rotary valves A and B can be reduced.
Owing to these structural advantages, the diameter of the ports of the rotary valve to be employed in the cryogenic gas separation system of the present invention can be easily increased. Thus, the volume of an operating gas and the operating frequency of the valve can be easily increased, whereby a larger-scale refrigerator can be provided by employing the valve. The number of ports of the rotary valve to be employed in the cryogenic gas separation system of the present invention can be easily increased, so that a complicated phase controller can be easily provided. Thus, a higher-efficiency refrigerator can be provided by employing the phase controller. With the larger-scale refrigerator, a cryogenic gas separation system such as an air separation unit can be operated without the use of any auxiliary means.
A cryogenic gas separation system as shown in Fig. 5 is constructed such that the pulse tube refrigerator 121 shown in Fig. 4 is incorporated in an air separation unit (nitrogen gas production unit of single column type), and the pulse tube refrigerator 121 is used for cooling of feed air. More specifically, the feed air which is compressed up to a predetermined pressure at an increased temperature by a feed air compressor 122 is cooled close to an ordinary temperature (about 25°C) by a water-cooled heat exchanger 123. After H₂O and CO₂ are almost completely removed from the feed air by an H₂O/CO₂ removal unit 124 or the like, the resulting feed air is supplied into a cold box 125. In the cold box 125, the feed air flows through a main heat exchanger 126 and is cooled to a liquefying temperature thereof, and then flows through a cold extracting portion 127 of the pulse tube refrigerator 121 so that the amount of liquefied feed air is increased. The resulting feed air is supplied to a lower portion of a rectification column 128. The cooling capacity of the pulse tube refrigerator 121 is equivalent to the sum of the amount of heat introduced from ambient temperature to the cold box 125, the heat transfer loss of the main heat exchanger 126, and the liquefaction energy required for extraction of a liquefied product.
A gaseous air portion of the feed air supplied into the lower portion of the rectification column 128 flows upward through the rectification column 128. A liquid air portion of the feed air is accumulated in the bottom of the rectification column 128 and then is supplied as a coolant into a condenser 129 located above the rectification column 128. In the condenser 129, the coolant liquefies N₂ gas in an upper portion of the rectification column 128 and then is returned as a reflux liquid into the upper portion of the rectification column 128. The feed air is rectified by the reflux liquid and the ascending gas, and the N₂ gas is separated from the air and extracted from the upper portion of the rectification column 128. After cold is recovered by the main heat exchanger 126, a product N₂ gas is taken out. In Fig. 5, reference numerals 130 and 131 denote an expansion valve and an exhaust gas outlet path, respectively.
In the air separation system, the pulse tube refrigerator 121 shown in Fig. 4 is used for the cooling of the feed air (all or part of the feed air output from the main heat exchanger 126 is cooled by the pulse tube refrigerator 121), but as objects to be cooled are not limited thereto. For example, the product nitrogen gas, the exhaust gas, the gas within the rectification column 128, the liquefied air or the like may be cooled by the pulse tube refrigerator 121. Alternatively, the pulse tube refrigerator 121 may cool and liquefy the feed air at an inlet of the main heat exchanger 126 or the product nitrogen gas or the exhaust gas at outlets of the main heat exchanger 126, and the liquefied gas may be supplied to a cryogenic portion of the cold box 125. Where the amount of cold produced by the pulse tube refrigerator 121 is insufficient, liquid nitrogen, liquid oxygen or the like may be supplied into the cold box to make up for any insufficient cold supply.
In the cryogenic gas separation system shown in Fig. 5, the air separation unit is embodied as a nitrogen gas production unit of a single column type, but also may be embodied as a common nitrogen gas production unit of a dual column type. The cryogenic gas separation system shown in Fig. 5 is constructed such that the pulse tube refrigerator 121 shown in Fig. 4 is incorporated in the air separation unit, but may be utilized for separation of various gas mixtures as long as the gas mixture separation is achieved through a cryogenic gas separation process.
Embodiments of the present invention will be described in greater detail with reference to the attached drawings.
Fig. 6 illustrates a pulse tube refrigerator to be employed in the cryogenic gas separation system in accordance with one embodiment of the present invention. In this embodiment, rotary valves C are respectively employed as the valves of the pulse tube refrigerator shown in Fig. 24. The pulse tube refrigerator of Fig. 6 has substantially the same construction as the pulse tube refrigerator of Fig. 24 except for the aforesaid valves, so that like components are denoted by like reference numerals.
The rotary valves C are each different from the rotary valve A in that a cylindrical rotary element 1 has a single recess 25 (see Fig. 7) formed in an outer peripheral portion thereof and a hollow cylindrical housing 2 has a pair of ports 26, 27 (see Fig. 8) which are formed in a circumferential wall thereof on one side thereof (on the left-hand side in Fig. 8) and adapted to be brought into communication with the recess 25. When the rotary element 1 is rotated into the position as shown in Fig. 8, the pair of ports 26, 27 communicate with the recess 25 to permit the operating gas to flow therethrough. When the rotary element 1 is rotated from this position into the position as shown in Fig. 9, the pair of ports 26, 27 are brought out of communication with the recess 25, so that the operating gas is prevented from flowing therethrough. Although all the valves of the pulse tube refrigerator are the rotary valves C in this embodiment of Fig. 6, the arrangement of the valves is not limited thereto. For example, only one of the valves may be the rotary valve C.
Even if the axial length of the recess 25 and the number of recesses to be provided in the rotary element 1 of the rotary valve C are increased, an increase in the diameter of the rotary element 1 is minimized, so that the rotary valve C has a reduced size and an extended service life. Thus, the refrigerator has a larger scale, a greater capacity and a higher efficiency.
Fig. 10 illustrates a modification of the rotary element 1 to be employed for the rotary valve C. In this modification, a pair of ports 28, 29 are provided in an outer peripheral portion of the rotary element 1 in association with the pair of ports 26, 27 of the housing 2, and communicate with each other via a communication path 30 (see Fig. 11). In this modification, the same features and effects are provided as in the embodiment described above.
Fig. 12 illustrates a pulse tube refrigerator to be employed in the cryogenic gas separation system in accordance with another embodiment of the present invention. The pulse tube refrigerator according to this embodiment has substantially the same construction as the pulse tube refrigerator shown in Fig. 24, except that rotary valves D as shown in Figs. 12, 14 and 15 are respectively employed instead of the pair of valves 93, 94 and the pair of valves 95, 96. Since the other components of the pulse tube refrigerator of Fig. 12 are the same as those of the pulse tube refrigerator of Fig. 24, like components are denoted by like reference numerals.
The rotary valves D are each different from the rotary valve A in that the rotary element 1 has recesses 32 and 33 respectively formed in an outer peripheral portion thereof on opposite sides thereof (on the left-hand side and the right-hand side thereof in Fig. 13). The housing 2 has three ports 34 to 36 formed in a circumferential wall thereof on one side thereof (on the left-hand side in Fig. 14), the ports 34, 35 being adapted to be brought into communication with the recess 32, the ports 35, 36 being adapted to be brought into communication with the recess 33. When the rotary element 1 is rotated into the position as shown in Fig. 14, the ports 34, 35 communicate with the recess 32 to permit an operating gas to flow therethrough. At this time, the ports 35, 36 do not communicate with the recess 33, so that the operating gas is prevented from flowing therethrough. When the rotary element 1 is rotated from this position into a position as shown in Fig. 15, the ports 35, 36 are brought into communication with the recess 33 to permit the operating gas to flow therethrough. At this time, the ports 34, 35 do not communicate with the recess 32, so that the operating gas is prevented from flowing therethrough. Although two rotary valves D are employed in this embodiment, the arrangement of the rotary valves is not limited thereto. For example, only one rotary valve D may be employed instead of the pair of valves 93, 94 or the pair of valves 95, 96. In this embodiment, the rotary valves D have the same features and effects as the rotary valve A.
Fig. 16 illustrates a rotary element 1 to be employed for a rotary valve E. The rotary element 1 of the rotary valve E has recesses 38 and 39 respectively formed in an outer peripheral portion thereof on opposite sides thereof (on the left-hand side and the right-hand side thereof in Fig. 16). In the rotary valve E, a housing 2 has two pairs of ports 40 to 43 formed in a circumferential wall thereof on one side thereof (on the left-hand side in Figs. 17 and 18), the pair of ports 40, 41 being adapted to be brought into communication with the recess 38 (see Fig. 17), the pair of ports 42, 43 being adapted to be brought into communication with the recess 39 (see Fig. 18). The rotary valve E has the same features and effects as the rotary valve D.
Fig. 19 illustrates a pulse tube refrigerator to be employed in the cryogenic gas separation system in accordance with further another embodiment of the present invention. In this embodiment, a single rotary valve F is employed instead of the four valves 93 to 96 in the pulse tube refrigerator shown in Fig. 24 (i.e., the pulse tube refrigerator of this embodiment has substantially the same construction as the pulse tube refrigerator of Fig. 4). Referring to Fig. 19, the pulse tube refrigerator includes a compressor 51, a regenerator 52, a pulse tube 53, a high pressure buffer tank 54, and a low pressure buffer tank 55. The pulse tube refrigerator further includes a pipe 56 for communication between a low pressure side of the compressor 51 and a port 75 of the rotary valve F, a pipe 57 for communication between a high pressure side of the compressor 51 and a port 77 of the rotary valve F, a pipe 58 for communication between the high pressure buffer tank 54 and a port 78 of the rotary valve F, and a pipe 59 for communication between the low pressure buffer tank 55 and a port 80 of the rotary valve F.
As shown in Fig. 20, the rotary valve F includes a rotary element (valve body) 61 to be rotated in one direction by a motor (not shown), and a housing 62 accommodating the rotary element 61 in a rotatable manner. In Fig. 20, a coupling shaft portion 61a of the rotary element 61 projects through one end (a right-hand end in Fig. 20) of the housing 62 to be coupled to the motor. Bearings 63 rotatably support the rotary element 61. A reference numeral 64 denotes O-rings, and reference numerals 65, 66 denote end covers.
The rotary element 61 has four recesses 71 to 74 formed in an outer peripheral portion thereof. The housing 62 has six ports 75 to 80 formed in a circumferential wall thereof and aligned longitudinally thereof on an outer circumference thereof. The ports 75 to 80 are provided in association with the recesses 71 to 74 of the rotary element 61. More specifically, the recess 71 of the rotary element 61 is associated with the ports 76, 77 of the housing 62, and the recess 72 is associated with the ports 75, 76. The recess 73 is associated with the ports 78, 79, and the recess 74 is associated with the ports 79, 80. The port 76 of the housing 62 communicates with the regenerator 52, and the port 79 communicates with the pulse tube 53.
Next, the operation of the pulse tube refrigerator of Fig. 19 will be briefly explained. By the rotation of the motor, the ports 75 to 77 of the housing 62 are brought out of communication with each other, and the ports 79, 80 are brought out of communication with each other. At this time, the inside pressure of the pulse tube 53 is equal to the pressure at the low pressure side of the compressor 51. When the ports 78, 79 are brought into communication with each other via the recess 73 of the rotary element 61 (see Fig. 21), a high pressure coolant gas in the high pressure buffer tank 54 flows into a hot end of the pulse tube 53, so that the gas pressure within the pulse tube 53 increases almost to the inside pressure of the high pressure buffer tank 54.
When the ports 76, 77 are brought into communication with each other via the recess 71 of the rotary element 61 (see Fig. 20), the high pressure coolant gas is supplied from the high pressure side of the compressor 51 into a cold end of the pulse tube 53. At this time, the inlet pressure of the high pressure coolant gas (the pressure at the high pressure side of the compressor 51) is set at a slightly higher level than the inside pressure of the high pressure buffer tank 54, so that the high pressure coolant gas introduced into the hot end of the pulse tube 53 is immediately returned into the high pressure buffer tank 54.
After the communication between the ports 76 and 77 and between the ports 78 and 79 is interrupted, the ports 79, 80 are brought into communication with each other via the recess 74 of the rotary element 61 (see Fig. 22). Since the coolant gas flows back into the low pressure buffer tank 55 from the hot end of the pulse tube 53, the inside pressure of the pulse tube 53 is reduced to a level equivalent to the inside pressure of the low pressure buffer tank 55. More specifically, the high pressure coolant gas within the pulse tube 53 is expanded to a reduced pressure which is equivalent to the inside pressure of the low pressure buffer tank 55. Therefore, the temperature of the gas is lowered, so that the cold end of the pulse tube 53 is cooled.
When the ports 75, 76 are brought into communication with each other via the recess 72 of the rotary element 61 (see Fig. 23), the coolant gas expanded in the pulse tube 53 is discharged to the low pressure side of the compressor 51, and the lower pressure coolant gas flows into the pulse tube 53 from the low pressure buffer tank 55.
Thus, one cycle is completed, and then the next cycle is started. The coolant gas is thus circulated, whereby the high pressure coolant gas is continuously expanded to a reduced pressure.
The pulse tube refrigerator to be used in the embodiments described above may be either a closed system or an open system. Further, the pulse tube refrigerator may have or may not have a cold accumulating material. The pulse tube refrigerator may be of indirect cooling type or of direct cooling type.
As described above, the first cryogenic gas separation system according to the present invention utilizes the cold produced by the refrigerator as the cold source for the gas separation, and the refrigerator employs the rotary valve which has the plurality of ports provided in the outer peripheral portion of the rotary element (rotatable about the axis thereof and having the circular cross section perpendicular to the axis), and the plurality of ports provided in the peripheral wall of the housing (accommodating the rotary element in a rotatable manner). Since the plurality of ports of the rotary valve for the refrigerator are axially independently provided, an increase in the diameter of the rotary element is minimized even if the diameter and number of the ports are increased. This allows the rotary valve to have a reduced size and an extended service life. As a result, the diameter and number of the ports can be easily increased in the rotary valve as compared to a conventional solenoid valve and flat seal rotary valve, so that the refrigerator can have a larger scale, a greater capacity and a higher efficiency. For example, the refrigerator can be embodied as a larger-scale refrigerator having a wattage of not smaller than several hundreds watts. Of course, the refrigerator may be embodied as a smaller-scale refrigerator having a wattage of several watts as in the prior art. The larger-scale, greater-capacity and higher-efficiency refrigerator makes it possible to operate the first cryogenic gas separation system without the use or any auxiliary means, thereby providing a cost reduction. In the second cryogenic gas separation system according to the present invention, the refrigerator has the same features and effects as the refrigerator employed in the first cryogenic gas separation system. Therefore, the second cryogenic gas separation system can achieve a cost reduction like the first cryogenic gas separation system.
While the present invention has been described in detail by way of the embodiments thereof, it should be understood that the foregoing disclosure is merely illustrative of the technical principles of the present invention but not limitative of the same. The spirit and scope of the present invention are to be limited only by the appended claims.
The features disclosed in the foregoing description, in the claims and/or in the accompanying drawings may, both separately and in any combination thereof, be material for realising the invention in diverse forms thereof.

Claims

A cryogenic gas separation system which comprises a refrigerator and utilizes cold produced by the refrigerator as a cold source for separation of a gas, the refrigerator incorporating a rotary valve which comprises a rotary element rotatable about an axis thereof and having a circular cross section perpendicular to the axis, and a housing accommodating the rotary element in a rotatable manner, the rotary element having a plurality of ports provided in an outer peripheral portion thereof, the housing having a plurality of ports provided in a peripheral wall thereof in association with the ports of the rotary element, the rotary valve being operative to be switched between a position where predetermined ones of the ports of the rotary element are aligned with corresponding ones of the ports of the housing for communication therebetween and a position where the predetermined ones of the ports of the rotary element are displaced in non-alignment with the corresponding ones of the ports of the housing for non-communication therebetween by rotation of the rotary element.
A cryogenic gas separation system which comprises a refrigerator and utilizes cold produced by the refrigerator as a cold source for separation of a gas, the refrigerator incorporating a rotary valve which comprises a rotary element rotatable about an axis thereof and having a circular cross section perpendicular to the axis, and a housing accommodating the rotary element in a rotatable manner, the rotary element having a recess provided in an outer peripheral portion thereof, the housing having a plurality of ports provided in a peripheral wall thereof in association with the recess, the rotary valve being operative to be switched between a position where the recess is aligned with the ports for communication therebetween and a position where the recess is displaced in non-alignment with the ports for non-communication therebetween by rotation of the rotary element.
A cryogenic gas separation system as set forth in claim 1 or 2, wherein the gas is air.
A cryogenic gas separation system as recited in any of claims 1 to 3, wherein the refrigerator is a helium refrigerator.
A cryogenic gas separation system as set forth in claim 4, wherein the helium refrigerator is a pulse tube refrigerator.
A cryogenic gas separation system as set forth in claim 4, wherein the helium refrigerator is a Gifford-McMahon refrigerator.
A cryogenic gas separation system as set forth in claim 4, wherein the helium refrigerator is a Solvay refrigerator.