Helium liquefier and method of operating a helium liquefier

Abstract

The present invention provides a helium liquefier and its operating method that can remove hydrogen, an impurity in raw helium, even during the first few hours after startup when there is excess processing capacity in the compressor, as well as during the purification and cool-down processes in the internal purification operation. [Solution] The helium liquefier is operated by repeatedly performing the following steps: a compressor 101 that circulates and supplies helium gas from the helium liquefier main body 200, a hydrogen remover 102, and an internal purifier 190 provided in the helium liquefier main body 200. The internal purifier 190 cools the impure helium gas by passing it through a heat exchanger with the low temperature helium gas from the helium liquefier main body, and removes impurities in the impure helium gas by solidifying them on the heat transfer surface of the heat exchanger; a regeneration step melts and removes the impurities solidified on the heat transfer surface with helium gas from the compressor; and a cool-down step cools the internal purifier 190 with the low temperature helium gas from the helium liquefier main body 200.

Description

Technical Field

[0001] The present invention relates to a helium liquefier with an internal purifier and a method for operating a helium liquefier. More specifically, it relates to a helium liquefier and a method for operating a helium liquefier that has a function for removing hydrogen in raw helium gas even outside the internal purification operation.

Background Art

[0002] Conventionally, in many helium liquefiers, a hydrogen remover attached to an internal purifier is provided, and hydrogen, which is an impurity in raw helium gas, is removed by periodically operating the internal purifier (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

[0004] FIG. 2 shows an example of a conventional helium liquefier to which a hydrogen remover described in Patent Document 1 is attached. The helium liquefier 1 is mainly composed of a normal temperature section 100 and a helium liquefier main body section 200. Further, an internal purifier 190 is provided in the helium liquefier main body section 200.

[0005] In the helium liquefier main body section 200 other than the internal purifier 190, heat exchangers HX01, HX02, HX03, HX04, HX05, expansion turbines T1, T2, and a JT (Joule - Thomson) valve 115 are provided. Further, the normal temperature section 100 includes a compressor 101, a buffer tank 103, and an oil separator 104.

[0006] The helium gas is pressurized to a predetermined pressure by the compressor 101 and introduced into the helium liquefier main unit 200 from piping L1. In the helium liquefier main unit 200, according to a well-known configuration, a portion of the raw helium gas is collected as liquid helium, and the remaining helium gas is introduced again into the suction side of the compressor 101 from piping L2.

[0007] Here, the maximum amount that the compressor 101 can process is designed to match the maximum amount that the helium liquefier main unit 200 can process. Therefore, for several hours after the helium liquefier main unit 200 starts up (during pre-cooling) and during internal purification operation, the processing capacity of the helium liquefier main unit 200 is less than the maximum value, resulting in a surplus of discharged gas from the compressor 101. Conventionally, the difference between the processing capacity of the helium liquefier main unit 200 and the processing capacity of the compressor 101 was controlled by introducing the surplus helium gas into the buffer tank 103.

[0008] On the other hand, a helium refrigerator is a device similar to the helium liquefier of the present invention and the conventional device described above. In a helium refrigerator, it is basically necessary to circulate helium as a refrigerant and generate (supply) a constant cold to the outside, and the circulating refrigerant (helium) is operated at a constant rate, and the operation does not involve periodically increasing or decreasing the processing amount. However, even in a helium refrigerator, since helium is used as a refrigerant, the removal of hydrogen from the helium can be a problem. In that case, the processing capacity of the compressor is designed to be slightly (α) larger than the processing capacity of the helium refrigerator, but in order to reduce the cost of the device, α is made as small as possible, and then, for example, a device and control method are known in which hydrogen from the excess helium gas α is introduced into a purifier (gas purifier 14 in Patent Document 2) by the control described in Patent Document 2 to remove the hydrogen. [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] However, unlike helium refrigerators, helium liquefiers generally experience fluctuations in the amount of helium they process (circulate). The objective is to provide a helium liquefier and a method for operating it that can remove hydrogen, an impurity in the raw helium, even during the first few hours after startup (during pre-cooling) when excess helium is generated, and during internal purification operations. [Means for solving the problem]

[0010] To achieve the above objective, the helium liquefier of the present invention comprises a compressor that compresses helium gas from the helium liquefier main body and circulates it back to the helium liquefier main body; a hydrogen remover provided in the piping connecting the discharge side and the suction side of the compressor; and an internal purifier provided in the helium liquefier main body. The internal purifier is characterized by repeatedly performing the following steps: a purification step in which impurity helium gas is cooled by passing it through a heat exchanger with the low-temperature helium gas from the helium liquefier main body, thereby solidifying and removing impurities in the impurity helium gas onto the heat transfer surface of the heat exchanger; a regeneration step in which the impurities solidified on the heat transfer surface are melted and removed with helium gas from the compressor; and a cool-down step in which the internal purifier is cooled by the low-temperature helium gas from the helium liquefier main body.

[0011] Furthermore, the configuration of the helium liquefier operating method of the present invention comprises a compressor that compresses helium gas from the helium liquefier main body and circulates it back to the helium liquefier main body, a hydrogen remover provided in the piping connecting the discharge side and the suction side of the compressor, and an internal purifier provided in the helium liquefier main body, wherein the internal purifier is configured to repeat a purification step in which impurity helium gas is cooled by passing it through a heat exchanger with the low-temperature helium gas from the helium liquefier main body and impurities in the impurity helium gas are solidified and removed from the heat exchanger's heat transfer surface, a regeneration step in which the impurities solidified on the heat transfer surface are melted and removed with helium gas from the compressor, and a cool-down step in which the internal purifier is cooled by the low-temperature helium gas from the helium liquefier main body, wherein at least a portion of the helium gas from the compressor is introduced into the hydrogen remover during the purification step or the cool-down step. Furthermore, the system is characterized by introducing at least a portion of the helium gas from the compressor into the hydrogen remover when the helium liquefaction unit is started.

[0012] Furthermore, the operating method of the helium liquefier of the present invention also involves operating the compressor while the helium liquefier main unit is stopped, and introducing at least a portion of the helium gas compressed by the compressor into the hydrogen remover. [Effects of the Invention]

[0013] According to the present invention, hydrogen, an impurity in the raw helium, can be removed even during the first few hours after startup (during pre-cooling) when there is excess processing capacity in the compressor relative to the processing capacity of the helium liquefier body, as well as during the purification and cool-down processes in the internal purification operation. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic diagram showing an example of the room-temperature section of the helium liquefaction apparatus of the present invention. [Figure 2] This is a schematic diagram showing an example of a conventional helium liquefier. [Figure 3]This graph shows the change in the excess airflow of the compressor during startup and steady-state operation of a helium liquefier. [Modes for carrying out the invention]

[0015] An example of one embodiment of the helium liquefier of the present invention will be explained using Figures 1 and 2. Figure 1 is a schematic diagram showing an example of the room-temperature section of a helium liquefier, and Figure 2 is a diagram showing an example of a conventional helium liquefier. A and B in Figure 1 correspond to A and B in Figure 2, and in this example of the helium liquefier of the present invention, everything except the room-temperature section is the same as the conventional device.

[0016] First, the common operation and configuration of the helium liquefier of the present invention and the conventional helium liquefier 1 will be described in detail with reference to Figure 2. The helium gas, pressurized to approximately 950 kPaG by the compressor 101, is introduced into the piping L3 within the helium liquefier main body 200 via the oil separator 104 and piping L1. The introduced helium gas is cooled in the heat exchanger HX01 by liquid nitrogen supplied from the outside to piping L4 as auxiliary cooling, and by the return helium gas passing through piping L5, which will be described later. It is also possible to introduce a portion of the helium gas from the oil separator 104 into piping L6 and then into the compressor 101 via the buffer tank 103.

[0017] The helium gas cooled in heat exchanger HX01 is introduced into heat exchanger HX02 for further cooling. A portion of the helium gas is branched off from the middle of heat exchanger HX02 into piping L7 and introduced into expansion turbines T1 and T2, where isentropic expansion generates the necessary cold in the helium liquefier main body 200.

[0018] Also, the remaining part of the helium cooled by the heat exchanger HX02 is introduced into the heat exchanger HX03 through the pipe L3 and cooled together with the helium passing through the pipe L7 introduced into the expansion turbine T1 described above. The helium gas passing through the pipe L3 is further cooled by the heat exchanger HX04 and introduced into the adsorber 112. The adsorber 112 is a so-called 20K adsorber that adsorbs with activated carbon cooled to 20K or less, and adsorbs and removes hydrogen gas contained as an impurity in helium. The helium gas from which hydrogen gas has been adsorbed and removed by the adsorber 112 is branched into a pipe L8 that becomes liquid helium and a pipe L9 that cools the internal purifier 190.

[0019] The helium gas introduced into the pipe L8 is further cooled by the heat exchanger HX05, becomes a gas-liquid mixed phase state by isenthalpic expansion with the expansion valve 115, and is introduced into the liquid helium storage tank 117. The helium that has undergone isenthalpic expansion with the expansion valve 115 can be introduced into the liquid helium storage tank from the inner pipe of the triple pipe 116. The triple pipe 116 has a vacuum chamber as the outer pipe, and a middle pipe is formed between the outer pipe and the inner pipe. The liquid helium in the liquid helium storage tank 117 is assumed to be pumped out by the user into a portable container and transported, for example, to the laboratory where the user belongs for use.

[0020] The gas phase part in the liquid helium storage tank 117 returns to the pipe L5 through the middle pipe of the triple pipe 116 and is introduced as helium gas. The return helium gas in the pipe L5 is heated by the heat exchanger HX05, then merges with the helium gas in the pipe L7 that has passed through the expansion turbines T1 and T2 described above, and is sequentially introduced into the heat exchangers HX04, HX03, HX02, and HX01, cools the helium gas flowing through the pipe L3, and is heated to room temperature itself. It is introduced from the pipe L5 into the pipe L2 of the room temperature section 100, merges with the helium gas from the buffer tank 103 passing through the pipe L10, and is introduced into the compressor 101.

[0021] Generally, when a user uses liquid helium, impurities such as air are mixed into the helium (hereinafter, the helium gas containing impurities may be referred to as impure helium gas). Since helium is a precious resource, the impure helium gas mixed with impurities is recovered in the gas bag 130, purified, and reused. In the following description, the impurities of the helium gas are described as air, but in the present invention, the impurities are not limited to air.

[0022] The impure helium gas temporarily stored in the gas bag 130 is purified by removing impurities such as air in the internal purifier 190. The internal purifier 190 is a device that improves the purity of the helium gas by solidifying and adhering the air, which is an impurity, to the heat transfer surface of the heat exchanger. The internal purifier 190 sequentially repeats the process of solidifying and adhering the impure air to the heat transfer surface of the heat exchanger (hereinafter referred to as the purification process), the process of excluding the solidified air from the heat transfer surface of the heat exchanger by heating (hereinafter referred to as the regeneration process), and the process of cooling the internal purifier 190 (hereinafter referred to as the cool-down process).

[0023] The impure helium gas from the gas bag 130 is pressurized to a predetermined pressure by the recovered helium gas compressor 131 and introduced into the internal purifier 190 from the pipe L11. In addition, if necessary, the impure helium gas from the impure helium gas candle 135 may be added to the impure helium gas pressurized to a predetermined pressure by the recovered helium gas compressor 131 and introduced into the internal purifier 190. Hereinafter, the purification process, the regeneration process, and the cool-down process will be described in detail.

[0024] (Purification process) The impure helium gas in piping L11, pressurized to a predetermined pressure, is introduced into heat exchangers HX06, HX07, and HX08, where it is cooled by the helium gas flowing through piping L9. This cooling also cools the air in the impure helium gas, causing the air components to liquefy and solidify on the heat transfer surface of heat exchanger HX08. The helium gas, whose purity has been reduced to at least 99.95% by the solidification of the air components, flows through piping L12 and is introduced into heat exchangers HX09, HX08, HX07, and HX06, where it cools the impure helium gas flowing through piping L11 and is heated to room temperature. Subsequently, it merges with piping L3 from piping L13 and is introduced into heat exchanger HX01 together with the helium gas in piping L3. At this time, any excess helium gas exceeding the processing capacity of the helium liquefier main unit 200 is stored in buffer tank 103 via piping L1 and L6.

[0025] Here, the helium gas in piping L9 is introduced into heat exchangers HX09, HX08, HX07, and HX06, and after being used to cool the impure helium gas as described above, it is heated to room temperature and merges with the helium gas in piping L5 that is led out from heat exchanger HX01, and is introduced into compressor 101 via L2.

[0026] (Regeneration process) If impure helium gas solidifies inside heat exchanger HX08, there is a risk of blockage of the heat exchanger's flow path. Therefore, after a certain period of purification, a regeneration process is performed. In this regeneration process, valve 152 in piping L9 is closed, and the low-temperature helium gas flowing through piping L9 is not introduced into the internal purifier 190. In addition, a portion of the helium gas introduced into heat exchanger HX01 via piping L3 branches off into piping L13 and is introduced into heat exchangers HX06, HX07, HX08, and HX09 in the reverse flow of the purification process. Furthermore, the air components solidified on the heat transfer surface of heat exchanger HX08 are melted, and these air components are carried along with the helium gas inside piping L11. A portion of the helium gas discharged from heat exchanger HX08 branches off into piping L14 and is discharged to the outside. The remaining helium gas discharged from heat exchanger HX08 flows through piping L11 and is sequentially introduced into heat exchangers HX07 and HX06, where it is heated. Afterward, it branches off from piping L11 to piping L16, where hydrogen is removed from the helium gas by a hydrogen remover 155 before being introduced into the gas bag 130. In other words, in conventional equipment, the hydrogen content in the helium gas present in the helium liquefier 1 is removed during this regeneration process.

[0027] (Cool-down process) After the regeneration process removes the air components from the internal purifier 190, the valve 152 in piping L9 opens, and low-temperature helium gas is introduced into the internal purifier 190, cooling it down. After the inside of the internal purifier 190 has cooled to a predetermined temperature, impure helium gas is introduced from piping L11, and the internal purifier 190 returns to the purification process described above.

[0028] Up to this point, we have described the common operation and configuration of the helium liquefier of the present invention and the conventional helium liquefier 1. Now, we will describe the configuration of the room temperature section 100' of the helium liquefier of the present invention based on Figure 1. Components identical to those of the room temperature section 100 in Figure 2 are denoted by the same reference numerals, and detailed explanations are omitted.

[0029] The ambient temperature section 100' is equipped with a compressor 101 for circulating and supplying high-pressure helium gas, which is drawn in from the helium liquefier main unit 200 and compressed, to the helium liquefier main unit 200, via a pipe L20 connecting pipe L1 (discharge side path) and pipe L2 (suction side path), and an oil separator 104 provided on the discharge side of the compressor 101. It also includes a pipe L6 connecting pipe L1 to the buffer tank 103, a pipe L10 connecting pipe L2 to the buffer tank 103, and a bypass pipe L21 connecting pipe L1 and pipe L2. Furthermore, a hydrogen remover 102 is provided in pipe L22, which is installed in parallel with pipes L20 and L21. Valves V1, V2, V3, V4, V5, V6, and V7 are provided in each of the pipes.

[0030] The basic process is the same as in the conventional apparatus shown in Figure 2. The internal purifier 190 sequentially repeats the purification process, regeneration process, and cool-down process. During the regeneration process, the valve 152 of piping L9 is closed, so the cold temperature of the helium gas discharged from the adsorber 112 passes through piping L5 and is used in the helium liquefaction unit 200 to liquefy the raw helium gas passing through piping L3.

[0031] On the other hand, during the purification and cool-down processes, valve 152 is open, so some of the cold helium gas discharged from the adsorber 112 is introduced into the internal purifier 190 from piping L9 and used to remove air components from the impure helium gas. Therefore, during the purification and cool-down processes, the processing capacity of the helium liquefaction unit is temporarily reduced (the helium liquefaction unit body 200 is in a state where it cannot take in the helium gas from piping L3).

[0032] Therefore, during the refining and cooling processes, valves V3, V4, V5, and V6 are opened, and valve V2 is closed. Any helium gas compressed by the compressor 101 that exceeds the processing capacity of the helium liquefier main unit 200 is introduced from piping L1 to piping L22, where hydrogen, an impurity in the raw helium gas, can be removed by the hydrogen remover 102. Valve V3 is controlled by the suction (inlet) pressure of the compressor 101 and opens when there is excess airflow in the compressor 101. Valve V3 can also be controlled by the opening degree of valve V7 in piping L21. Furthermore, a portion of the helium gas exceeding the processing capacity of the helium liquefier main unit 200 can be temporarily introduced into the buffer tank 103.

[0033] On the other hand, in the regeneration process, the internal purifier 190 is difficult to use because most of the helium gas compressed by the compressor 101 is introduced into the helium liquefier main unit 200, making it difficult to introduce some of the helium gas compressed by the compressor 101 into the hydrogen remover 102. During the regeneration process, valves V2, V3, V4, V5, and V6 are open, and valve V1 is closed. Furthermore, by setting the pressure P in the buffer tank 103 to be such that the discharge pressure of the compressor 101 >> P >> the suction pressure of the compressor 101, it is possible to supply helium gas from the buffer tank 103 via valve V2 when the discharge pressure of the compressor 101 decreases, and to recover gas from the buffer tank 103 via valve V1 when the discharge pressure becomes too high.

[0034] In other words, during the operation of the internal purifier 190, the processing capacity of the helium liquefaction unit temporarily decreases during the purification and cool-down processes. This timing can be used to remove hydrogen, an impurity in the helium gas, using the hydrogen remover 102. This hydrogen removal at room temperature also leads to a reduction in the load on the adsorber 112.

[0035] In the design of a typical helium liquefier, the processing capacity of the compressor 101 is generally set to have a margin of safety slightly greater than the liquefaction performance of the helium liquefier. This margin of safety is addressed by introducing the excess helium gas into a buffer tank 103 for temporary storage or by operating the compressor 101 at a reduced rate. However, in the present invention, the difference between the processing capacity of the compressor 101 and the liquefaction performance (processing capacity) of the helium liquefier, which arises from the operating timing of the internal purifier 190, is utilized. This difference is introduced into the hydrogen remover 102, and hydrogen is removed at room temperature through purification, thus eliminating the need to ensure a margin of safety in the processing capacity of the compressor 101.

[0036] Furthermore, while the use of the hydrogen remover 102 during steady-state operation of the helium liquefier has been described so far, it is also difficult to accept raw helium when starting the helium liquefier from room temperature. The present invention can also be applied during such startup. Figure 3 shows the difference (excess airflow) between the processing volume of the compressor 101 and the liquefaction performance (processing capacity) of the helium liquefier when the helium liquefier is started at room temperature and transitions to steady-state operation.

[0037] The helium flow when the helium liquefier is started will be explained using Figure 2. The basic helium gas flow is the same as described above, but the helium gas compressed by the compressor 101 is cooled in the heat exchangers HX01, HX02, HX03, and HX04, and impurities are removed in the adsorber 112. Then it is introduced into pipe L18, which branches off from pipe L8, and further into pipe L5 via valve 119. In addition, a portion of the helium gas compressed by the compressor 101 branches off into pipe L7 from near the middle of heat exchanger HX02, is introduced into expansion turbines T1 and T2, and then into pipe L5. At this time, the expansion valve 115 and the storage tank return valve 118 are closed. The helium gas introduced into pipe L5 is heated in the heat exchangers HX05, HX04, HX03, HX02, and HX01, and then introduced into the compressor 101 via pipe L2.

[0038] In the helium liquefier startup process shown in Figure 3, the compressor 101 first reaches its rated capacity, and the total airflow from the compressor becomes excess airflow until the helium liquefier begins to cool. Subsequently, as the helium liquefier cools, the density of the gas inside the liquefier increases, and the processing capacity of the helium liquefier increases, so the excess airflow gradually decreases. At startup, the helium liquefier is at room temperature, and the processing capacity of the compressor 101 far exceeds the processing capacity of the helium liquefier, so a large amount of helium gas is introduced into the hydrogen remover 102, and hydrogen can be removed from the helium gas even during startup.

[0039] Furthermore, when the helium liquefier is started, the storage tank return valve 118 is closed, but as the helium liquefier cools, the storage tank return valve 118 opens slightly (storage tank return valve open in Figure 3). When the storage tank return valve 118 opens slightly, helium gas in the liquid helium storage tank 117 is introduced into L5, slightly increasing the excess airflow of the compressor. As the helium liquefier cools further, the storage tank return valve 118 and expansion valve 115 are automatically operated to the open direction, and valve 119 is operated to the closed direction, and when cooling is complete, valve 119 is fully closed. When the expansion valve 115 opens, helium gas is introduced into piping L8. The helium gas introduced into piping L8 is further cooled by the heat exchanger HX05 and expands isenthalpically in the expansion valve 115, becoming a gas-liquid mixed phase, which is then introduced into the liquid helium storage tank 117.

[0040] In a helium liquefier, hydrogen in the helium gas is basically removed by the adsorbent 112. However, when the helium liquefier is started up, the adsorbent 112 has not yet cooled to a predetermined temperature, so hydrogen removal by the adsorbent 112 is insufficient. However, as in this embodiment, by providing a hydrogen remover 102, it becomes possible to remove hydrogen from the helium from the start of the helium liquefier's startup process.

[0041] In particular, after the helium liquefier has finished operation, its internal temperature gradually rises due to natural heating. Consequently, the hydrogen components adsorbed and removed by the adsorbent 112 are desorbed, and the hydrogen concentration in the helium in the piping L1, L6, L2 and the heat exchangers HX01 to HX05 increases. Therefore, the hydrogen concentration in the helium inside the helium liquefier is highest at startup. If there were no hydrogen remover 102, it would be necessary to evacuate the system to remove hydrogen, and if the system is not regularly evacuated, hydrogen would accumulate inside the system. However, by providing a hydrogen remover 102 as in this example, it is possible to remove the hydrogen contained in the helium gas during the cooling process at startup of the helium liquefier without evacuating the system.

[0042] Furthermore, during steady-state operation of the helium liquefier, the internal purifier 190 repeats the purification process, regeneration process, and cool-down (CD) process, as described above. During the regeneration process, the valve 152 of the piping L9 is closed, so the cooling of the low-temperature helium gas discharged from the adsorber 112 is used to liquefy the raw helium gas passing through piping L3.

[0043] On the other hand, during the purification process and the cool-down process, the processing capacity of the helium liquefaction machine temporarily decreases, but it is possible to remove hydrogen from the helium gas by utilizing this timing. Generally, in a helium liquefaction machine that does not have an internal purification unit 190 and is equipped with a hydrogen remover 102, the processing capacity of the compressor has a small margin (+α) relative to the processing capacity of the helium liquefaction machine. In other words, unless the processing capacity of the compressor is increased to some extent, it becomes difficult to introduce a portion of the helium gas from the compressor into the hydrogen adsorbent. However, in the case of a helium liquefaction machine that has an internal purification unit 190, there is a process in which the processing capacity of the helium liquefaction machine temporarily decreases, so there are periodically times when the processing capacity of the compressor has a small margin (+α) relative to the processing capacity of the liquefaction machine. The present invention utilizes this timing. Therefore, even if the processing capacity of the compressor is designed to be equal to the processing capacity of the helium liquefaction machine without providing a margin, hydrogen removal from the helium gas by the hydrogen remover 102 is possible with the present invention.

[0044] Furthermore, the helium liquefier and the method of operating the helium liquefier of the present invention are not limited to the embodiments described above. Since a hydrogen remover 102 is provided, a hydrogen remover 155 does not need to be provided. In addition, by introducing helium gas temporarily stored in the buffer tank 103 into the hydrogen remover 102 and then into the suction side of the compressor 101, hydrogen can be removed even during the regeneration process.

[0045] As described above, when the helium liquefier is turned off, the temperature inside the helium liquefier main unit 200 gradually rises due to natural heating. As a result, the temperature of the adsorber 112 also rises, and the hydrogen gas adsorbed on the adsorber 112 diffuses into the helium gas in the piping and heat exchanger inside the helium liquefier main unit 200.

[0046] In conventional helium liquefiers, the helium gas in which hydrogen has been diffused is not introduced into the internal purification unit 190. Therefore, when the helium liquefier is restarted, the hydrogen diffused into the helium gas is again adsorbed by the adsorber 112, causing it to accumulate in the helium liquefier with each operation. For this reason, it was necessary to periodically perform vacuum replacement inside the helium liquefier to remove the hydrogen gas from the system. Vacuum replacement here refers to the process of repeatedly evacuating the helium liquefier and introducing high-purity helium gas into the helium liquefier.

[0047] Therefore, in the helium liquefier covered by the present invention, it is possible to operate the compressor 101 while the helium liquefier main body 200 is stopped, and introduce at least a portion of the compressed helium gas into the hydrogen remover 102 to remove hydrogen from the helium gas in the helium liquefier. In this case, if necessary, a portion of the helium gas compressed by the compressor 101 may also be introduced into the valve V7 and the buffer tank 103. This operation eliminates the need for periodic vacuum replacement in the helium liquefier, and the need for a vacuum pump and the preparation of high-purity helium gas. [Explanation of Symbols]

[0048] 1...Helium liquefier, 100, 100'...Room temperature section, 101...Compressor, 102...Hydrogen remover, 103...Buffer tank, 104...Oil separator, 112...Adsorber, 115...Expansion valve, 116...Mitsusumi pipe, 117...Liquid helium storage tank, 118...Storage tank return valve, 119...Valve, 130...Gas bag, 131...Recovered helium gas compressor, 152...Valve, 155...Hydrogen remover, 190...Internal purifier, 200...Helium liquefier main body, V1, V2, V3, V4, V5, V6, V7...Valve, HX01~HX08...Heat exchanger, T1, T2...Expansion turbine, L1~L14, L16, L18, L20~L22... Piping

Claims

1. A compressor that compresses helium gas from the helium liquefier main body and circulates it back to the helium liquefier main body, A hydrogen remover is provided in the piping connecting the discharge side and the suction side of the compressor, The helium liquefier includes an internal purification unit provided in the main body of the helium liquefier, The aforementioned internal purifier is The purification process involves using the low-temperature helium gas in the main body of the helium liquefaction unit to cool the impure helium gas by passing it through a heat exchanger, thereby solidifying and removing impurities in the impure helium gas onto the heat transfer surface of the heat exchanger. A regeneration process in which impurities solidified on the heat transfer surface are melted and removed with helium gas from the compressor, The process involves repeatedly performing a cool-down step in which the internal purification unit is cooled by the low-temperature helium gas in the main body of the helium liquefaction unit. A helium liquefaction device characterized by the following features.

2. A compressor that compresses helium gas from the helium liquefier main body and circulates it back to the helium liquefier main body, A hydrogen remover is provided in the piping connecting the discharge side and the suction side of the compressor, The helium liquefier includes an internal purification unit provided in the main body of the helium liquefier, The aforementioned internal purifier is The purification process involves using the low-temperature helium gas in the main body of the helium liquefaction unit to cool the impure helium gas by passing it through a heat exchanger, thereby solidifying and removing impurities in the impure helium gas onto the heat transfer surface of the heat exchanger. A regeneration process in which impurities solidified on the heat transfer surface are melted and removed with helium gas from the compressor, A cool-down process is performed in which the internal purifier is cooled by the low-temperature helium gas in the main body of the helium liquefaction unit. In a helium liquefaction operation method that involves repeated operation, A method for operating a helium liquefaction apparatus, characterized in that at least a portion of the helium gas from the compressor is introduced into the hydrogen remover during the purification step or the cool-down step.

3. The method for operating a helium liquefier according to claim 2, characterized in that at least a portion of the helium gas from the compressor is introduced into the hydrogen remover when the helium liquefier is started.

4. A method for operating a helium liquefier according to claim 1, characterized in that the compressor is operated while the helium liquefier main body is stopped, and at least a portion of the helium gas from the compressor is introduced into the hydrogen remover.

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