JP2005083588A - Helium gas liquefying device, and helium gas recovering, refining and liquefying device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To considerably reduce the size and cost of a device producing liquid helium with a small flow rate. <P>SOLUTION: A cooling head of a compact very low temperature refrigerating machine typified by a GM refrigerating machine, is inserted into a vacuum heat insulation tank in a state of being thermally kept into contact with a helium gas flow channel, and the helium gas in the flow channel is cooled to be lower than a liquefying temperature by the compact very low temperature refrigerating machine to produce the liquid helium. Further a plurality of compact very low temperature refrigerating machines may be used to allow the helium gas flow channel to be thermally brought into contact with each of cooling heads successively in stages. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an apparatus for continuously liquefying helium gas to generate liquid helium, and a helium gas recovery / purification / liquefaction apparatus using the apparatus.

  As is well known, helium, particularly liquid helium, is important as a refrigerant for superconducting devices and other various cryogenic devices, and the demand for them is increasing more and more recently. By the way, helium gas is a rare gas that is present only in about 5.2 ppm in the air, and it is difficult to separate and extract from the air on a mass production scale. Therefore, in Japan, in general, liquid helium separated from natural gas and liquefied is imported from abroad, and the price is inevitably expensive. Therefore, when liquid helium is used as a refrigerant or the like in various ultra-low temperature apparatuses, it is strongly desired to recover the evaporated helium gas, purify and liquefy it, and use it again as liquid helium.

  For this purpose, as an apparatus for liquefying helium gas recovered from various ultra-low temperature apparatuses, conventionally, helium gas is compressed to a high pressure of about 2 MPa by a compressor, and the compressed high-pressure helium gas is converted into a liquefier. Introduced into the above, the one that lowers the temperature mainly using adiabatic expansion and liquefies is used. A typical example of this type of liquefaction apparatus is shown in FIG.

  In FIG. 4, reference numeral 1 denotes a compressor, 2 denotes a liquefier main body for liquefying high-pressure helium gas introduced from the compressor 1, and 3 denotes a liquid helium container that stores liquid helium liquefied by the liquefier main body 2. Indicates. The liquefying device main body 2 is fed with high-pressure helium gas from the compressor 1 and finally to the liquid helium container 3, and conversely, helium gas on the liquid surface in the liquid helium container 3 is sent to the compressor 1. A return path 5 is provided. Between the forward path 4 and the return path 5, the heat exchanger 6A is arranged in multiple stages (five stages in the illustrated example) in order to cool the helium gas flowing on the forward path 4 side using helium gas flowing on the return path 5 side as a refrigerant. , 6B, 6C, 6D, 6E, and an expansion turbine for taking out a portion of the high-pressure helium gas from the middle of the forward path 4 and adiabatically expanding it, thereby leading the cooled helium gas to the return path 5 Alternatively, expansion engines 7A and 7B composed of expansion pistons are provided in two stages. Further, a bypass path 10 for the first stage heat exchanger 6A among the heat exchangers 6A to 6E is provided on the inlet side of the forward path 4, and a precooling heat exchanger 6F is inserted in the bypass path 10. The precooling heat exchanger 6F is configured to precool part of the high-pressure helium gas from the compressor 1 by liquid nitrogen introduced from the outside through the liquid nitrogen supply path 8. Further, a JT valve 9 for performing adiabatic free expansion is provided on the most downstream side in the forward path 4, and an outlet side of the JT valve 9 is led to the liquid helium container 3 described above.

  In the conventional apparatus shown in FIG. 4, helium gas compressed to a high pressure of about 2 MPa by the compressor 1 is partially cooled by liquid nitrogen in the precooling heat exchanger 6F and heated in the forward path 4. The heat exchange is performed with the low-temperature helium gas on the return path 5 side by the exchanger 6A, and the temperature is lowered. Further, the heat exchangers 6B to 6E are sequentially heat-exchanged with the low-temperature helium gas on the return path 5 side, and the temperature is gradually lowered. Finally, the adiabatic free expansion is performed by the JT valve 9 to lower the temperature below the liquefaction temperature of helium, and the liquid helium is led to the liquid helium container 3. Then, from the liquid surface of the liquid helium container 3, the evaporated low-temperature helium gas is guided to the return path 5, and is heat-exchanged with the forward path 4 side as described above. Here, a significant portion of the helium gas on the forward path 4 side is adiabatically expanded by the expansion engines 7A and 7B to become a low temperature, and the helium gas having reached the low temperature is led to a position in the middle of the return path 5, As a result, it becomes possible to efficiently cool the forward-side helium gas in the heat exchangers 6A to 6E as described above.

  As described above, in the conventional apparatus, the high pressure helium gas introduced from the compressor 1 to the outward path 4 is not cooled to the liquefaction temperature or less as it is, but a considerable portion is extracted in the outward path by the expansion engines 7A and 7B. It is adiabatically expanded and introduced in the middle of the return path 5. This is because heat exchange with the returned helium gas from the liquid helium container 3 is not sufficient to sufficiently reduce the temperature of the helium gas before reaching the JT valve 9.

  By the way, in the conventional apparatus as described above, practically, about 70% of the high-pressure helium gas introduced from the compressor 1 is adiabatically expanded by the expansion engines 7A and 7B and directly returned to the return path 5 side, It is used to cool the helium gas on the forward path 4 side in the exchangers 6A to 6E. In other words, only about 30% of the high-pressure helium gas introduced from the compressor 1 reaches the JT valve 9. Further, only about 1/5 of that is adiabatically expanded and liquefied by the JT valve 9, and therefore, only about 6% of the total amount of compressed helium gas is actually liquefied. Therefore, as the compressor 1, a large-sized compressor having a large flow rate of about 16 to 17 times the target liquefaction amount is required, and a large-sized one is required as the heat exchangers 6A to 6E. A thermal expansion engine is also needed. Therefore, in the conventional apparatus, there is a problem that the apparatus cost itself is remarkably expensive and requires a large installation space, especially in the case of an apparatus with a small target liquefaction amount, compared with the slight liquefaction amount. In other words, it is necessary to circulate a remarkably large amount (16 to 17 times) of helium gas. For this reason, in the past, at locations where only a small amount of liquid helium is used, the actual situation is that the evaporative gas has been discharged directly into the atmosphere without being recovered. However, this is a serious problem in using rare and expensive helium.

  The present invention was made against the background as described above, and as a helium liquefying device that can be reduced in size and solve the problem of installation space, and has a low device cost, particularly as a device that generates liquid helium at a low flow rate, To provide a helium liquefaction device that can be significantly reduced in size and cost compared to conventional ones, and a helium gas recovery, purification, and liquefaction device that can efficiently recover and purify and liquefy helium gas. It is the purpose.

  Unlike the conventional technique shown in FIG. 4, the helium liquefaction apparatus of the present invention compresses the helium gas to be liquefied and liquefies the helium gas at a low temperature by adiabatic expansion and adiabatic free expansion. It was cooled with a small cryogenic refrigerator represented by Gifford McMahon refrigerator) to condense. In other words, the compressor required for the previous stage of temperature drop by adiabatic expansion and adiabatic free expansion of the recovered helium gas is not required. In addition, small cryogenic refrigerators were provided in multiple stages to cool the helium gas in stages.

  Specifically, the helium gas liquefying apparatus of the invention of claim 1 is small in size so that a flow path of helium gas to be liquefied is provided in the vacuum heat insulating tank and is in thermal contact with the helium gas flow path. A cooling head of a cryogenic refrigerator is inserted into a vacuum heat insulating tank, and helium gas in the flow path is cooled to below the liquefaction temperature by a small cryogenic refrigerator to generate liquid helium. is there.

  A helium gas liquefying apparatus according to a second aspect of the present invention is the helium gas liquefying apparatus according to the first aspect, wherein a plurality of small cryogenic refrigerators are used, and a cooling head of each small cryogenic refrigerator is provided. The helium gas passage is inserted into the vacuum heat insulating tank and is configured to be in thermal contact with each cooling head step by step.

  Further, the inventions of claims 3 to 5 define a helium gas recovery / purification / liquefaction device using the helium gas liquefaction device according to claim 1 or claim 2, and various ultra-low temperature devices (liquid helium). Helium gas is recovered from the equipment used so that it can be purified and liquefied efficiently and stably.

  Specifically, the helium gas recovery / purification / liquefaction device of the invention of claim 3 is a helium gas recovery / purification / liquefaction device using the helium gas liquefaction device of claim 1 or claim 2, In addition to the helium gas liquefying device according to claim 1 or 2, a helium gas primary recovery device for receiving and storing evaporative helium gas from various helium gas using devices, and the primary recovery device A compressor for compressing stored gas, a helium gas secondary recovery device for storing high-pressure helium gas compressed and supplied from the primary recovery device by the compressor, and its secondary recovery A purifier for purifying helium gas supplied from the apparatus, and introducing the high purity helium gas from the purifier into the helium gas liquefying apparatus. It is characterized in that the.

  The helium gas recovery / purification / liquefaction device according to the invention of claim 4 is a helium gas recovery / purification / liquefaction device using the helium gas liquefaction device according to claim 3, wherein the helium gas secondary recovery device is a purification device. A gas supply cylinder for the purifier and at least one source gas supply cylinder, and between the gas supply cylinder for the purifier and the source gas supply cylinder, the gas separation cylinder is separated in a flow path. A separation on-off valve for communication is provided, and further, between the outlet side of the helium gas primary recovery device and the helium gas secondary recovery device, from the helium gas primary recovery device to the inside of the primary recovery device The helium gas is compressed into the gas supply cylinder for the purifier of the secondary recovery device and the compressor for feeding the gas into the source gas supply cylinder, and the gas for the purifier is provided. The supply cylinder is connected to the inlet side of the purifier so as to supply helium gas to the purifier, and the helium gas supply line from the gas supply cylinder for the purifier to the purifier is connected to the purifier. Supply pressure detecting means for detecting the pressure of the supplied helium gas is provided, the outlet side of the purifier is connected to the inlet side of the helium gas liquefying device, and further, the helium gas secondary recovery device A return flow path for returning helium gas from the source gas supply cylinder to the helium gas primary recovery device is provided, and a return on-off valve and a pressure reducing valve for opening and closing the return flow path are inserted in the return flow path. The helium gas in the primary recovery device is compressed by a compressor in a state where the separation on-off valve is opened and the reflux on-off valve is closed, and filled in each cylinder of the secondary recovery device, and Separation Helium gas is supplied to the purifier from the gas supply cylinder for the purifier of the secondary recovery unit with the on-off valve and the reflux on-off valve closed, and the supply helium gas pressure is lowered and supplied. When the pressure detecting means detects, the return on-off valve of the return flow path is opened, and the high pressure gas in the source gas supply cylinder of the secondary recovery device is reduced in pressure by the pressure reducing valve and returned to the primary recovery device. It is characterized by doing so.

  Furthermore, the helium gas recovery / purification / liquefaction device according to the invention of claim 5 is the helium gas recovery / purification / liquefaction device according to claim 4, wherein the helium gas primary recovery device includes the helium gas primary recovery. Gas amount detection means for detecting the amount of helium gas in the apparatus is provided, and the operation / stop of the compressor is controlled by the gas amount detection means.

  The helium gas liquefying apparatus of the present invention is different from the system in which the recovered helium gas to be liquefied is compressed and cooled and liquefied by a small cryogenic refrigerator at atmospheric pressure, unlike the method of cooling and liquefying by adiabatic expansion and adiabatic free expansion Therefore, unlike the conventional apparatus, it is not necessary to compress a helium gas as much as 16 to 17 times the liquefaction amount to a high pressure of about 2 MPa, and therefore a large-sized and high-output compressor is unnecessary, and the liquefaction is not required. It is not necessary to circulate a large amount of helium gas that is about 16 to 17 times as much as the amount to be obtained, and almost all of the introduced helium gas is liquefied. An expansion engine is also unnecessary, so that the apparatus can be greatly reduced in size, installation space can be reduced, and apparatus cost can be significantly reduced.

  Moreover, in the apparatus of the invention of claim 2, since the small cryogenic refrigerators are installed in multiple stages, the helium gas can be cooled step by step, and therefore, an optimum refrigerator according to the temperature is selected, Cost reduction can be achieved, and even when one refrigerator breaks down, the operation state can be continued, or at least a low-temperature state can be maintained and early recovery can be achieved.

  Furthermore, according to the helium gas recovery / purification / liquefaction apparatus of the third to fifth aspects of the invention, it is possible to efficiently purify / liquefy almost the entire amount of helium gas recovered by the helium gas primary recovery apparatus.

  FIG. 1 shows an example of the principle configuration of the helium gas liquefying apparatus of the present invention.

  In FIG. 1, reference numeral 11 denotes an inlet for introducing evaporated helium gas from a superconducting device (not shown) or other various cryogenic devices using liquid helium. From the inlet 11, the inside of the helium gas device main body 12 (described later). A space between the inside of the vacuum heat insulating tank 23 and the helium condensation vessel 13 is connected by a helium gas flow path (pipe) 15. First, a buffer tank 17 is provided on the inlet side of the helium gas flow path 15 so that helium gas introduced from the introduction port 11 is temporarily stored in the buffer tank 17. Further, an opening / closing valve 19 and a flow control device (mass flow controller; MFC) 21 are provided on the outlet side of the buffer tank 17 in the helium gas flow channel 15, and the helium gas flow channel on the outlet side of the flow control device 21. Is inserted into the vacuum heat insulation tank 23 constituting the helium liquefier main body 12.

  A plurality of (three in the illustrated example) GM refrigerators 25A, 25B, and 25C having different refrigeration capacities are installed in the vacuum heat insulating tank 23 as small cryogenic refrigerators. As for each GM refrigerator 25A-25C, the valve motor parts 27A-27C are located in the outer surface side of the vacuum heat insulation tank 23, respectively, and each cooling head (heat-transfer part) 29A-29C was inserted in the vacuum heat insulation tank 23. It is in a state. The compressors 31 </ b> A to 31 </ b> C for compressing the refrigerant of these GM refrigerators 25 </ b> A to 25 </ b> C are individually arranged at locations away from the vacuum heat insulating tank 23. Here, as for GM refrigerator 25A-25C, for example, 1st stage refrigerator 25A has a cooling capacity to 80K, 2nd stage refrigerator 25B has a cooling capacity to 20K, 3rd stage refrigerator 25C Is selected to have a cooling capacity of up to 4K.

  In the vacuum heat insulating tank 23, the helium gas flow path 15 is in thermal contact with the cooling heads 29A to 29C of the GM refrigerators 25A to 25C. Specifically, for example, in the vacuum heat insulating tank 23, the flow path 15 is first wound around the cooling head 29A of the first stage GM refrigerator 25A in a coil shape (first stage cooling unit 15A), and then the second stage. The coil is wound around the cooling head 29B of the second GM refrigerator 25B (second stage cooling unit 15B), and further wound around the cooling head 29C of the third stage GM refrigerator 25C (third stage). Cooling part 15C).

  Further, the flow path 15 is led to the upper part of the helium condensation container 13 from the outlet side of the third stage cooling unit 15C corresponding to the third stage cooling head 29C. A liquid helium discharge conduit 33 extends from the lower portion of the helium condensation vessel 13 and is guided to the outside of the vacuum heat insulation tank 23 to finally contain liquid helium. The liquid helium container 35 is guided.

  In the apparatus shown in FIG. 1 as described above, evaporative helium gas from various ultra-low temperature apparatuses (uses of liquid helium) (not shown) is introduced into the buffer tank 17 from the introduction port 11, and the on-off valve 19 and the flow control device. 21 is led to the first stage cooling section 15A in contact with the first stage GM refrigerator cooling head 29A in the vacuum heat insulation tank 23 in the helium liquefier main body 12 by the helium gas flow path 15 and cooled to, for example, about 80K. . Next, the helium gas is guided to the second stage cooling unit 15B in contact with the second stage GM refrigerator cooling head 29B, cooled to, for example, about 20K, and further, the third stage cooling unit in contact with the third stage GM refrigerator cooling head 29C. It is led to 15C and cooled to about 4K, that is, below the liquefaction temperature at normal pressure of helium, and condensation and liquefaction are started, and it is led into the helium condensation vessel 13 and completely liquefied. Then, liquid helium is led from the helium gas condensing container 13 through the discharge pipe 33 into the external liquid helium container 35 by gravity and stored.

  Thus, in the apparatus of FIG. 1, helium gas is cooled in steps. Here, a small cryogenic refrigerator represented by a GM refrigerator has a higher cooling capacity as the temperature is higher, so it is possible to efficiently cool and liquefy by selecting a refrigerator according to the temperature drop process of the helium gas. Can be made. That is, when helium gas near room temperature is directly cooled to 4K by one refrigerator, the cooling capacity becomes small and it becomes difficult to efficiently cool and liquefy. By cooling from near to 80K, from 80K to 20K, and from 20K to 4K step by step with different refrigerators, the cooling capacity of each refrigerator can be increased and the efficiency of cooling and liquefaction can be improved.

  In the example of FIG. 1, for example, even when one of the first-stage GM refrigerator 25A or the second-stage GM refrigerator 25B fails and the operation is stopped, the other refrigerators are operating. Therefore, although the efficiency deteriorates, the operation can be continued, and even if it becomes difficult to cool down to the liquefaction temperature, the low temperature state in the system can be maintained to some extent. Driving can be recovered early. Further, for example, when the third stage GM refrigerator 25C fails, if the remaining GM refrigerators 25A and 25B are normal, the low temperature state can be maintained to some extent as described above, so that early recovery is possible.

  In addition, since the GM refrigerators 25A to 25C are provided in multiple stages, and the compressors 31A to 31C are individually provided for each refrigerator, the compressors 31A to 31C may be small-sized, and these Distributing the weight can be achieved by installing them individually.

  Note that the compressors 31A to 31C of the GM refrigerators 25A to 25C used in the example of FIG. 1 are much smaller than the compressor 1 of the apparatus of FIG. 4 shown as the prior art. That is, in the case of the example of FIG. 4, as already described, a large amount of helium gas that is about 16 to 17 times the amount of helium gas to be liquefied must be compressed at a high compression ratio, whereas This is because the compressors 31 </ b> A to 31 </ b> C are refrigerant compressors for refrigerators until they get tired, and there is no such thing as described above.

  In the example of FIG. 1 as described above, an open system (open cycle) device in which liquefied helium is simply injected into the liquid helium container 35 is shown, but the present invention can also be applied to a circulation system (closed cycle) device. Of course. FIG. 2 shows a principle example in that case. 2 that are the same as those in the example shown in FIG. 1 are given the same reference numerals, and descriptions thereof are omitted.

  In FIG. 2, a cryostat 37 constituting various ultra-low temperature devices is provided in place of the liquid helium vessel 35 shown in FIG. 1, and a heat exchanger for cooling an object by heat exchange in the cryostat 37. 39 is disposed. The liquid helium discharge pipe 33 is connected to the inlet side of the heat exchanger 39. One end side of the return channel 41 is connected to the outlet side of the heat exchanger 39. The other end side of the return channel 41 is connected to a location 43 on the outlet side of the buffer tank 17 in the helium gas channel 15 described above. An opening / closing valve 45 is inserted in the middle of the return flow path 41. A circulation blower 47 is interposed between the connection point 43 in the helium gas flow path 15 and the on-off valve 19.

  In such an example shown in FIG. 2, liquid helium is guided to the heat exchanger 39 in the cryostat 37 to indirectly cool the object. Then, the helium gas which has been vaporized due to the temperature rise in the heat exchanger 39 is drawn into the helium gas flow path 15 by the back pressure by the circulation blower 47 through the return flow path 41 and the on-off valve 45, and is similar to that already described. To cool and liquefy. Therefore, in this case, the entire amount of helium can be circulated and reused.

  By the way, as a helium gas liquefaction system for actual use in the field, it is also important how to efficiently reuse the evaporated helium gas recovered from various cryogenic devices, and the recovered evaporated helium gas is liquefied. In this case, it is also important to purify helium gas in advance, that is, to increase the purity of helium. FIG. 3 shows a specific example in which the whole is systemized in consideration of these points, that is, an example of a helium gas recovery / purification / liquefaction apparatus. 3 is a system in which the entire helium gas recovery / expansion / liquefaction apparatus is systemized using the same helium gas liquefier main body 12 shown in FIG. 1, and is the same as the example of FIG. Elements are denoted by the same reference numerals and description thereof is omitted.

  First, the basic configuration of the helium gas recovery / purification / liquefaction apparatus shown in FIG. 3 will be described. This helium gas recovery / purification / liquefaction apparatus includes, in addition to the helium gas liquefaction apparatus main body 12 shown in FIG. A gas bag 49 as a helium gas primary recovery device for receiving and storing the evaporated helium gas from the helium gas use device as it is at a low pressure (usually almost atmospheric pressure), and the primary recovery device (gas bag 49) A compressor 71 for compressing and increasing the pressure of the gas stored therein, and a high-pressure helium gas compressed and supplied by the compressor 71 from the primary recovery device (gas bag 49). Crude helium gas manifold 75 as a secondary helium gas recovery device and the secondary recovery device (crude helium gas manifold 75). Helium gas has a purifier 89 for highly purified, and is configured to introduce the high purity helium gas from the purifier 89 to the helium gas liquefaction apparatus body 12.

  Further, FIG. 3 will be described in detail. Helium gas from various cryogenic devices that generate liquid vapor using liquid helium is primarily recovered and accommodated in a gas bag 49 as a primary helium gas recovery device. It is like that. Specifically, for example, helium gas from the liquid helium container 51 in various ultra-low temperature devices is collected in a recovery balloon 53 and guided to a gas bag 49 by a vacuum pump 54. The helium gas from the cryostat 55 is directly guided to the gas bag 49. Further, the helium gas evaporated in the liquid helium container 35 is also introduced into the gas bag 49 through the check valve 57 and the like when the pressure is excessively high.

  Here, the gas bag 49 as the helium gas primary recovery device is provided with a level meter 59 as gas amount detection means for detecting the amount of gas recovered in the gas bag 49. The upper limit level H and the lower limit level L of the gas bag 49 that expands and contracts in the height direction according to the amount of helium gas introduced into the gas is detected (thus detecting the upper and lower limits of the amount of helium gas introduced into the gas bag 49). be able to.

  The outlet 49A of the gas bag 49 is led to a crude helium gas manifold 75 as a helium gas secondary recovery device via a compressor 71, a flow path 73, and an on-off valve 74. Here, the crude helium gas manifold 75 includes a plurality (six in the illustrated example) of gas cylinders 77A to 77F, and the cylinder closest to the compressor 71 is the gas supply cylinder 77A for the purifier. The remaining ones are the source gas supply cylinders 77B to 77F, and the gas supply cylinder 77A for the purifier and the source gas supply cylinders 77B to 77F are separated in a flow path. / A separation on-off valve 79 for communication is inserted. Further, a pressure detector 81 as a supply pressure detecting means for detecting the pressure of the helium gas supplied to the purifier 89 is provided in a portion that directly communicates with the gas supply cylinder 77A for the purifier. The supply cylinders 77B to 77F are connected to the inlet side of the compressor 71 by a return flow path 83, and a level meter 59 as the gas bag gas amount detection means is provided in the middle of the return flow path 83. A recirculation on-off valve 85 and a pressure-reducing valve 87, which are electromagnetic control valves that are opened and closed by, are inserted.

  Further, a purifier gas supply path 91 for guiding helium gas to the purifier 89 is connected to the flow path 73 between the compressor 71 and the on-off valve 74. In the gas supply path 91 for the purifier, an open / close valve 92, a high pressure pressure reducing valve 93, and a high pressure dryer 95 are inserted in this order.

  The purifier 89 has a configuration in which an inner tank 99 cooled by liquid nitrogen is disposed in a vacuum heat insulating tank 97, and a cooling heat exchanger 101, a condenser 103, and an adsorption cylinder 105 are arranged in the inner tank 99. A heat exchanger 107 for exchanging heat between the introduction-side helium gas and the generated helium gas is disposed inside the vacuum heat insulation tank 97 and outside the inner tank 99. The inner tank 99 includes a nitrogen supply pipe 109 for supplying liquid nitrogen as a refrigerant into the inner tank 99, a liquid air drain pipe 111 for discharging separated and removed liquid air, and an evaporated nitrogen gas discharge pipe. 113 is connected.

  The outlet side of the purifier 89 is led to the first stage cooling unit 15 </ b> A in the vacuum heat insulating tank 23 of the helium gas liquefier main body 12 by the purified gas supply pipe 115. Therefore, the supply line 115 corresponds to the helium gas flow path 15 in the example of FIG. A pressure holding valve 117, a pressure reducing valve 119, an on-off valve 19, and a flow rate control device (mass flow controller) 21 are inserted in the supply pipe line 115.

  The configuration of the helium liquefier main body 12 is the same as that shown in FIG. Further, a pressure detector 121 is provided in the gas discharge line 43 of the liquid helium container 35 that stores the liquefied helium, and the flow rate control device 21 is controlled by the pressure detector 121. .

  Next, the overall operation and operating status of the apparatus shown in FIG. 3 will be described.

  First, the recovery operation will be described. Helium is recovered in a gas bag 49 as a primary recovery device of helium gas from various cryogenic devices such as a cryostat 55, a liquid helium small container 51, and the like, and the helium gas is stored in the gas bag 49. When the amount of gas accumulated reaches the level H of the level meter 59 as the gas amount detecting means, the compressor 71 starts operation, and the helium gas in the gas bag 49 is coarsely processed as the helium gas secondary recovery device. The gas cylinders 77A to 77F of the helium manifold 75 are sent (filled). In this state, the on-off valve 79 is open.

  When the gas in the gas bag 49 is sent out in this way and the gas amount in the gas bag 49 is lowered to the level L of the level meter 59, the operation of the compressor 71 is stopped and the helium gas is sent out from the gas bag 49. (Gas filling into the cylinders 77A to 77F) is stopped. Thereafter, when new gas is collected in the gas bag 49 and reaches the level H of the level meter 59, the above-described delivery and filling operation is performed again. When the filling is repeated in this manner and the pressure of each of the cylinders 77A to 77F in the crude helium gas manifold 75 becomes equal to or higher than a predetermined pressure (pressure corresponding to the amount of gas sufficient for continuous liquefaction), the refining / liquefaction operation is performed. Is switched to.

  In performing the purification / liquefaction operation, the separation on-off valve 79 is closed, and each of the cylinders 77A to 77F in the crude helium gas manifold 75 as the secondary recovery device is replaced with a gas supply cylinder 77A for the purifier and a raw material gas. Separated into supply cylinders 77B to 77F, helium gas can be supplied exclusively from the gas supply cylinder 77A for the purifier to the purifier 89. Then, by opening the on-off valve 92, helium gas is actually supplied to the purifier 89 from the purifier gas cylinder 77A.

  Here, if the helium gas supply pressure from the gas supply cylinder 77A for the purifier to the purifier 89 falls to, for example, 12 MPa or less, the supply pressure detector 81 detects this, and the compressor 71 resumes operation. As a result, the helium gas in the gas bag 49 is compressed (compressed) toward the purifier gas supply cylinder 77A, and the pressure of the cylinder 77A (therefore, the pressure of the gas supplied to the purifier 89). ) Is increased to the maximum pressure (for example, 15 MPa), the operation of the compressor 71 is stopped. During this time, the amount of gas in the gas bag 49 decreases, but when the level gauge 59 of the gas bag 49 drops to level L, the return on-off valve (electromagnetic valve) 85 of the return flow path 83 opens. The high-pressure gas in the source gas supply cylinders 77B to 77F is sent into the gas bag 49 at a low pressure while being reduced in pressure by the pressure reducing valve 87, and the amount of gas in the gas bag 49 increases again. If this is detected by the level meter 59 (at level H), the compressor 71 restarts operation again, and helium gas is again supplied to the gas supply cylinder 77A for the purifier of the crude helium gas manifold 75 at a high pressure. It will be in the state of filling. Next, when the pressure detected by the supply pressure detector 81 reaches a sufficient supply pressure, helium gas is supplied to the purifier 89 from the gas cylinder 77A for gas supply for the purifier. Thereafter, when the supply pressure from the gas supply cylinder 77A for the purifier decreases again, the compressor 71 is operated again as described above, and the gas supply cylinder 77A for the purifier in the crude helium gas manifold 75 is operated at a high pressure. When helium gas is filled and the pressure becomes sufficiently high, helium gas is supplied again to the purifier 89 from the gas supply cylinder 77A for the purifier. By repeating such a process, almost all of the helium gas filled and recovered in the cylinders 77A to 77F of the crude helium gas manifold 75 by the initial recovery operation is supplied to the purifier 89.

  Here, the purifier 89 will be described. The purifier 89 liquefies and removes impurities (such as air) in the recovered helium gas by reducing the pressure to a liquid nitrogen temperature (−196 ° C.) at high pressure (in the case of air). After removing the impurity amount to 1% at 10 MPa), high purity helium gas is obtained using an adsorbent such as activated carbon. Therefore, as a gas supplied to the purifier 89, a high-pressure gas must always be supplied. Therefore, in the example of FIG. 3, the gas derived from the gas supply cylinder 77A for the purifier is maintained at a high pressure (for example, 15 to 12 MPa or more), and high pressure (for example, 11 MPa) helium gas is supplied via the high pressure reducing valve 93. This is supplied to the purifier 89. That is, a pressure-holding valve (flowing when the pressure becomes 10 MPa or more, for example) 117 is provided on the outlet side of the purifier 89 so that the pressure of the gas supplied to the purifier 89 can always be kept high.

  On the other hand, the gas exiting the purifier 89 is reduced in pressure (for example, reduced to 0.15 MPa) by the pressure reducing valve 119 through the pressure holding valve 117, and a certain amount to be liquefied is supplied to the liquefier main body 12 by the flow rate control device 21. However, it will flow through the purifier 89 by that amount. In this way, the gas can be supplied to the liquefier main body 12 after being purified by an amount that can be continuously liquefied.

  Immediately before the helium gas introduced into the purifier 89, moisture and the like are removed by the high-pressure dryer 95, and the moisture and the like are prevented from freezing at a low temperature and blocking the piping.

  The normal temperature helium gas introduced into the purifier 89 is cooled by heat exchange in the heat exchanger 107 with the purified and cooled high purity and low temperature helium gas. As a result, the consumption amount of liquid nitrogen that is a cold source of the purifier 89 can be reduced.

  Further, when helium gas is introduced into the inner tank 99 of the purifier 89, the helium gas is sufficiently heat exchanged with liquid nitrogen by the cooling heat exchanger 101, and air or the like as impurities in the introduced gas is liquefied by the condenser 103. Then, liquefaction separation and removal (in the case of air, removal of impurities up to 1% at 10 MPa) increases the purity of the introduced gas. In addition, when supplying directly to an adsorption | suction cylinder without using a capacitor | condenser, a large amount of adsorption agents for adsorb | sucking an impurity are needed, and a refiner | purifier will also be enlarged in connection with it.

  The helium gas exiting the capacitor 103 is adsorbed and removed by the adsorbent in the adsorption cylinder 105, and becomes high-purity helium gas. As described above, the high purity helium gas purified and cooled at a low temperature is heat-exchanged with the normal temperature helium gas introduced into the purifier 89 in the heat exchanger 107 and supplied to the liquefier main body. .

  Next, the state of liquefaction will be described. The high-pressure helium gas generated by the purifier 89 is reduced to a low pressure (for example, 0.15 MPa) by the pressure reducing valve 119, and a certain amount to be liquefied is liquefied by the flow controller 21. To be supplied. The operation of the liquefying device main body 12 is the same as that already described with reference to FIG. 1, and is cooled stepwise by the three-stage GM refrigerators 25A, 25B, and 25C, liquefied, and stored in the condensing container 13, and the head The liquid helium container 35 is introduced by gravity due to the difference.

  Here, if the cooling capacity of the refrigerator has a margin and the pressure in the liquid helium container 35 storing the liquefied helium gas becomes negative, the supply gas is increased by the control operation of the flow rate control device 21, and the liquefaction is increased. Corresponding control can be performed by increasing the amount. Conversely, when the amount of helium evaporation in the liquid helium container 35 increases and the pressure in the container 35 increases, helium gas is recovered in the gas bag 49 through a check valve (cracking pressure is about 10 kPa) 57. can do.

  In the helium gas recovery / purification / liquefaction apparatus shown in FIG. 3, the helium gas liquefaction apparatus (main body) 12 shown in FIG. 1 is applied and the liquefaction apparatus main body 12 is an open system. Of course, it can be applied to the cryostat 37 to form a circulatory system.

It is a schematic diagram which shows an example of the fundamental structure of the helium gas liquefying apparatus of this invention. It is an approximate solution figure showing other examples of the fundamental composition of the helium gas liquefying device of this invention. It is a schematic diagram showing an example of a helium gas recovery / purification / liquefaction device using the helium gas liquefaction device of the present invention. It is an approximate solution figure showing an example of the conventional helium gas liquefying device.

Explanation of symbols

12 Helium gas liquefier main body 15 Helium gas flow path 23 Vacuum insulation tank 25A, 25B, 25C GM refrigerator 29A, 29B, 29C as small cryogenic refrigerator Refrigeration head 49 Gas bag as helium gas primary recovery device 59 Gas Level meter as quantity detection means 71 Compressor 75 Crude helium gas manifold as helium gas secondary recovery device 77A Gas supply cylinder for purifier 77B to 77F Source gas supply cylinder 79 Separation on-off valve 81 Supply pressure detection means Pressure sensor 89 Purifier

Claims (5)

  A helium gas flow path to be liquefied is provided in the vacuum heat insulation tank, and a cooling head of a small cryogenic refrigerator is inserted into the vacuum heat insulation tank so as to be in thermal contact with the helium gas flow path. A helium gas liquefying apparatus, wherein helium gas in a flow path is cooled to a liquefaction temperature or lower by a small cryogenic refrigerator to generate liquid helium.   The helium gas liquefying apparatus according to claim 1, wherein a plurality of small cryogenic refrigerators are used, and a cooling head of each small cryogenic refrigerator is inserted in a vacuum heat insulating tank, A helium gas liquefying apparatus, wherein the flow path is configured to be in thermal contact with each cooling head step by step. A helium gas recovery / purification / liquefaction device using the helium gas liquefaction device according to claim 1 or 2;
In addition to the helium gas liquefying device according to claim 1 or 2, a helium gas primary recovery device for receiving and storing evaporative helium gas from various helium gas using devices, and the primary recovery device A compressor for compressing stored gas, a helium gas secondary recovery device for storing high-pressure helium gas compressed and supplied from the primary recovery device by the compressor, and its secondary recovery A purifier for purifying the helium gas supplied from the apparatus, and the high purity helium gas from the purifier is introduced into the helium gas liquefier. Helium gas recovery / purification / liquefaction equipment. In the helium gas recovery / purification / liquefaction apparatus using the helium gas liquefaction apparatus according to claim 3,
The secondary recovery apparatus for helium gas includes a gas supply cylinder for a purifier and at least one source gas supply cylinder, and is disposed between the gas supply cylinder for the purifier and the source gas supply cylinder. A separation on-off valve is provided for separating / communication between them in a flow path. Further, a helium gas 1 is provided between the outlet side of the helium gas primary recovery device and the helium gas secondary recovery device. There is provided the compressor for compressing and feeding the helium gas in the primary recovery device from the secondary recovery device to the gas supply cylinder for the purifier of the secondary recovery device and the source gas supply cylinder. The gas supply cylinder is connected to the inlet side of the purifier so as to supply helium gas to the purifier, and the helium gas from the gas supply cylinder for the purifier to the purifier The supply system is provided with supply pressure detection means for detecting the pressure of helium gas supplied to the purifier, and the outlet side of the purifier is connected to the inlet side of the helium gas liquefier, Furthermore, a return flow path for returning helium gas from the source gas supply cylinder of the helium gas secondary recovery apparatus to the helium gas primary recovery apparatus is provided, and the return flow path is used for opening and closing the return flow path. On-off valve and pressure reducing valve are inserted;
With the separation on-off valve opened and the reflux on-off valve closed, the helium gas in the primary recovery device is compressed by a compressor and filled in each cylinder of the secondary recovery device, and the separation on-off valve The helium gas is supplied to the purifier from the gas supply cylinder for the purifier of the secondary recovery device with the reflux on-off valve closed, and the pressure of the supplied helium gas is lowered to detect the supply pressure. When the means detects, the return on-off valve of the return flow path is opened, and the high pressure gas in the source gas supply cylinder of the secondary recovery device is reduced by the pressure reducing valve and returned to the primary recovery device. A helium gas recovery, purification, and liquefaction device. The helium gas recovery / purification / liquefaction apparatus according to claim 4,
The primary recovery device for helium gas is provided with gas amount detection means for detecting the amount of helium gas in the primary recovery device for helium gas, and the compressor is operated and stopped by this gas amount detection means. A helium gas recovery / purification / liquefaction device, characterized in that it is configured to control the gas.

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