JP2016175815A - Method and system for purifying helium gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the recovery rate of helium gas when the helium gas is purified to a high purity by a small-scale facility.SOLUTION: In adsorption columns 2a, 2b, 2c, 2d of a pressure swing adsorption apparatus 1, an adsorption step, a desorption step, and a pressurization step are sequentially performed to adsorb impurity gases contained in raw material helium gas on an adsorbent. A first gas sending-out step of sending out internal gas is performed in the adsorption column after the adsorption step and before the desorption step, and, at the same time, a first gas introduction step of introducing the sent-out gas is performed in the adsorption column after the desorption step and before the pressurization step. A second gas sending-out step of sending out internal gas is performed in the adsorption column after the first gas sending-out step and before the desorption step, and, at the same time, a second gas introduction step of introducing the sent-out gas is performed in the adsorption column after the desorption step and before the first gas introduction step. The inside of the adsorption column in the desorption step is decompressed to a pressure lower than the atmospheric pressure.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method and system for obtaining a high-purity helium gas by purifying a raw material helium gas containing an impurity gas.

  For example, helium used as a cooling liquid for MRI, an atmospheric gas or a cooling gas in the process of forming a porous base material and a drawing process in the production of optical fibers, etc., is a by-product of natural gas produced overseas in the United States and Middle East countries. Only a small amount is produced. In addition, helium demand is expected to increase in the manufacturing industry in emerging countries, particularly in Asia. However, helium prices continue to rise due to concerns about the future stable supply of helium. Thus, since helium is highly valuable and valuable, it is useful to recover helium from the equipment used for reuse. Therefore, it is desired that a diluted helium gas mixed with a large amount of impurity gas such as air is recovered as a raw material helium gas and purified to a high purity.

  Conventionally, as a method for refining raw material helium gas with high purity, a pressure swing adsorption device having a plurality of adsorption towers is used, and pressure swing adsorption method (PSA method) in which impurity gas is adsorbed on an adsorbent to separate it from helium gas. Is known (see Patent Document 1). In the pressure swing adsorption method, the impurity gas contained in the raw material helium gas introduced into the adsorption tower is adsorbed to the adsorbent under pressure, and the purified helium gas that is not adsorbed by the adsorbent is discharged. A purification process cycle in which a desorption process for desorbing the impurity gas and discharging it as off-gas, and a pressurization process for increasing the internal pressure of the adsorption tower are sequentially repeated.

  In the pressure swing adsorption method, the depressurization step for reducing the internal pressure is performed in the adsorption tower that is in the state after the adsorption step and before the desorption step, and at the same time, the adsorption tower that is in the state after the desorption step and before the pressure increase step In addition, it is known to perform a cleaning process in which the internal gas of the adsorption tower in the decompression process is introduced and then discharged as an off-gas. In addition, at the same time as performing the first gas delivery process for delivering the internal gas in any of the adsorption towers after the adsorption process and before the desorption process, the adsorption after the desorption process and before the pressurization process is performed. A first gas introduction step for introducing the internal gas sent in any one of the towers is executed, and further, the internal gas in any of the adsorption towers after the first gas delivery step and before the desorption step. And a second gas introduction step for introducing the internal gas delivered in another of the adsorption towers after the desorption step and before the first gas introduction step It is known to execute (see Patent Document 2). By introducing the internal gas of the adsorption tower in which the gas delivery process is executed into the adsorption tower in which the gas introduction process is executed, the internal pressure difference between the adsorption towers is reduced. That is, reduction of the internal pressure difference of the adsorption tower is executed twice for each purification processing cycle. It is also known to reduce the internal pressure difference of the adsorption tower three or more times for each purification treatment cycle (see Patent Document 3).

  Furthermore, in the desorption process of the pressure swing adsorption method, it is known that the inside of the adsorption tower is depressurized to less than atmospheric pressure by a vacuum pump, that is, the vacuum desorption process is executed.

Japanese Patent No. 5372607 U.S. Pat. No. 3,564,816 Japanese Patent Laid-Open No. 52-59073

Since helium gas is valuable, it is desirable to improve the recovery rate when purifying the raw material helium gas containing the impurity gas. However, according to the pressure swing adsorption method described in Patent Document 1, when the helium gas is purified to a high purity, the helium gas discharged as an off gas increases, and the recovery rate of the helium gas decreases.
Further, when reducing the internal pressure difference of the adsorption tower, helium is introduced into the adsorption tower after the adsorption process and before the desorption process into the adsorption tower after the desorption process and before the pressurization process. The gas recovery rate can be improved. However, as described in Patent Document 2, the recovery rate could not be sufficiently improved even if the internal pressure difference of the adsorption tower was reduced a plurality of times for each purification treatment cycle.
Furthermore, the recovery rate can be improved by recovering the performance of the adsorbent by the vacuum desorption step, but the improvement rate of the recovery rate by the vacuum desorption step is slight.
Therefore, according to the prior art, there is a problem that it is difficult to improve the recovery rate when helium gas is purified to a high purity with a small-scale purification system. An object of the present invention is to provide a purification method and a purification system of helium gas that can solve the problems of the prior art using the pressure swing adsorption method.

The present invention is based on the following findings.
In the pressure swing adsorption method, the improvement rate of the recovery rate by reducing the internal pressure difference of the adsorption tower and the improvement rate of the recovery rate by the vacuum desorption process are slight. For this reason, conventionally, it has been considered that the recovery rate is not significantly improved even if the reduction of the internal pressure difference of the adsorption tower is executed a plurality of times and the vacuum desorption process is combined. Moreover, since the time required for purification becomes longer due to the combination and the purification system becomes complicated, it has been considered that the demerit that the purification cost increases rather than the advantage that the recovery rate is slightly improved. Therefore, in the conventional purification method of helium gas using the pressure swing adsorption method, the reduction of the internal pressure difference of the adsorption tower is not performed a plurality of times and the execution of the vacuum desorption process is not combined.
Under such a conventional technical level, the improvement in the recovery rate when such a combination is performed is the improvement in the recovery rate by reducing the internal pressure difference of the adsorption tower multiple times, and the vacuum desorption. The present inventor found out that the degree of improvement in the recovery rate by the process is larger than the sum of the results and has a synergistic effect, and has led to the present invention.

  According to the method for purifying helium gas according to the present invention, when a raw material helium gas containing an impurity gas is purified using a pressure swing adsorption device having a plurality of adsorption towers, the impurity gas is given priority over the helium gas in each of the adsorption towers. The adsorbent to be adsorbed is stored, the raw material helium gas is sequentially introduced into each of the adsorption towers, and the impurity gas contained in the introduced raw material helium gas is introduced into the adsorbent under pressure in each of the adsorption towers. An adsorption process for discharging purified helium gas that is not adsorbed by the adsorbent, a desorption process for desorbing impurity gas from the adsorbent and discharging it as off-gas, and a pressure increasing process for increasing the internal pressure are sequentially executed. . A first gas delivery step for delivering an internal gas from any of the adsorption towers after the adsorption step and before the desorption step is performed, and at the same time, the delivered internal gas is removed after the desorption step. Then, a first gas introduction step is performed for introducing the gas to any one of the adsorption towers in a state before the pressure increasing step. At the same time as performing the second gas delivery step for delivering the internal gas from any of the adsorption towers after the first gas delivery step and before the desorption step, the delivered internal gas is removed from the desorption step. A second gas introduction step is performed, which is introduced into another of the adsorption towers after and before the first gas introduction step. In the desorption step, the inside of the adsorption tower is depressurized to less than atmospheric pressure by a vacuum pump.

According to the method of the present invention, the internal gas delivered from the adsorption tower in the first gas delivery process is introduced into the adsorption tower in the first gas introduction process, thereby reducing the internal pressure difference between the adsorption towers. . In addition, the internal gas delivered from the adsorption tower in the second gas delivery process is introduced into the adsorption tower in the second gas introduction process, thereby reducing the internal pressure difference between the adsorption towers. That is, the internal pressure difference of the adsorption tower can be reduced twice for each purification treatment cycle.
By reducing the internal pressure difference of the adsorption tower, the internal gas of the adsorption tower in the first and second gas delivery processes is introduced into the adsorption tower in the first and second gas introduction processes, so that it is included in the internal gas. Thus, the purified helium gas that is not adsorbed by the adsorbent can be recovered. Moreover, a vacuum desorption process can be performed by reducing the inside of an adsorption tower to less than atmospheric pressure with a vacuum pump in a desorption process. The performance of the adsorbent can be recovered by the vacuum desorption process.
That is, by reducing the internal pressure difference of the adsorption tower twice for each purification treatment cycle and recovering the performance of the adsorbent by the vacuum desorption process, the recovery rate of helium gas can be greatly improved by a synergistic effect. .
The difference between the internal pressure of the adsorption tower in the first gas delivery step and the internal pressure of the adsorption tower in the first gas introduction step needs to be eliminated when the first gas delivery step and the first gas introduction step are completed. However, the internal pressure may be equalized by eliminating the difference. Further, the difference between the internal pressure of the adsorption tower in the second gas delivery step and the internal pressure of the adsorption tower in the second gas introduction step is determined when the second gas delivery step and the second gas introduction step are completed. Although it is not necessary to eliminate it, you may eliminate the difference and equalize both internal pressures.

The purification system for helium gas according to the present invention includes a pressure swing adsorption device having a plurality of adsorption towers, and an adsorbent that preferentially adsorbs impurity gas over helium gas is stored in each of the adsorption towers. The pressure swing adsorption device includes a raw material gas introduction flow channel for introducing the raw material helium gas into each of the adsorption towers, a purified gas flow channel for discharging purified helium gas from each of the adsorption towers, and the adsorption tower An off-gas flow path for discharging off-gas from each of them, a communication flow path for communicating any one of the adsorption towers with another, and a separate space between each of the adsorption towers and the raw material gas introduction flow path A source gas introduction path opening / closing valve that opens and closes to each other, a purification gas path opening / closing valve that individually opens and closes between each of the adsorption towers and the purified gas flow path, and a space between each of the adsorption towers and the off gas flow path individually An off-gas path opening / closing valve that opens and closes, and a communication path opening / closing valve that individually opens and closes between each of the adsorption towers and the communication flow path. Each of the opening / closing valves is an automatic valve having an opening / closing actuator so that the opening / closing operation can be performed individually, and is connected to a control device. In each of the adsorption towers, an adsorption step of adsorbing the impurity gas contained in the introduced raw material helium gas to the adsorbent under pressure and discharging purified helium gas that is not adsorbed by the adsorbent, and from the adsorbent Each of the on-off valves is controlled by the control device so that a desorption process for desorbing the impurity gas and discharging it as off-gas, and a boosting process for increasing the internal pressure are sequentially performed. A first gas delivery step for delivering an internal gas from any of the adsorption towers after the adsorption step and before the desorption step is performed, and at the same time, the delivered internal gas is removed after the desorption step. In order to execute the first gas introduction step to be introduced into any one of the adsorption towers in the state before the pressure increasing step, the inside of any of the adsorption towers in the first gas delivery step, and the first Each of the on-off valves is controlled by the control device so as to communicate with any other interior of the adsorption tower in the one gas introduction step. At the same time as performing the second gas delivery step for delivering the internal gas from any of the adsorption towers after the first gas delivery step and before the desorption step, the delivered internal gas is removed from the desorption step. Any of the adsorption towers in the second gas delivery step to perform a second gas introduction step after being introduced into another of the adsorption towers in a state before the first gas introduction step. Each of the on-off valves is controlled by the control device so that the inside of the gas pipe communicates with any other inside of the adsorption tower in the second gas introduction step. A vacuum pump for reducing the inside of the adsorption tower in the desorption step to less than atmospheric pressure;
According to the system of the present invention, the method of the present invention can be carried out.

In the method of the present invention, the amount of gas sent from the adsorption tower in the first gas delivery step and introduced into the adsorption tower in the first gas introduction step is set so that the helium concentration of the raw material helium gas is higher. It is preferable to increase it.
As a result, the higher the helium concentration of the raw material helium gas, the greater the amount of helium gas introduced into the adsorption tower in the first gas introduction step, so that the recovery rate of helium gas can be improved. Therefore, when the helium concentration of the raw material helium gas fluctuates, for example, when helium gas discharged from an optical fiber manufacturing process or the like is used as the raw material helium gas, it is possible to flexibly cope with the fluctuation of the raw material gas concentration.

In this case, the system of the present invention includes a flow rate control valve that adjusts the flow rate of the gas flowing through the communication flow path, and the flow rate control valve is an automatic valve having a flow rate adjusting actuator so that a flow rate adjusting operation can be performed. A predetermined constant execution time of the first gas delivery step and the first gas introduction step, which is connected to the control device and includes a sensor connected to the control device for detecting the helium concentration of the raw material helium gas. Is stored in the control device, and the flow rate of the gas sent from the adsorption tower in the first gas delivery step and introduced into the adsorption tower in the first gas introduction step in the communication channel, and the raw material A predetermined correspondence between the helium concentration of the helium gas is stored in the control device, and is sent from the adsorption tower in the first gas delivery step to The amount of gas introduced into the adsorption tower in the one-gas introduction step increases as the helium concentration detected by the sensor increases, so that the first gas delivery is performed for the execution time stored by the control device. Preferably, the on-off valve is controlled to execute the process and the first gas introduction process, and the opening degree of the communication flow path is changed by the flow rate control valve based on the correspondence.
Alternatively, the system of the present invention includes a sensor that detects a helium concentration of the raw material helium gas and is connected to the control device, and performs an execution time of the first gas delivery step and the first gas introduction step, and the raw material helium. A predetermined correspondence relationship with the helium concentration in the gas is stored in the control device, and is sent from the adsorption tower in the first gas delivery process and introduced into the adsorption tower in the first gas introduction process. The control device changes the execution time of the first gas delivery step and the first gas introduction step based on the correspondence relationship so that the amount of gas to be increased increases as the helium concentration detected by the sensor increases. Preferably it is done.

  In the method of the present invention, in any one of the adsorption towers after the first gas delivery step and before the second gas delivery step, a depressurization step for reducing the internal pressure is performed and at the same time after the desorption step. In any one of the adsorption towers in a state before the second gas introduction process, a cleaning process is performed in which the internal gas of the adsorption tower in the decompression process is introduced and then discharged as an off-gas. preferable.

  In this case, the system according to the present invention executes the pressure reducing step for reducing the internal pressure in any of the adsorption towers after the first gas sending step and before the second gas sending step. A cleaning step of introducing the internal gas of the adsorption tower in the depressurization step and discharging it as an off-gas in any one of the adsorption towers after the desorption step and before the second gas introduction step It is preferable that each of the on-off valves is controlled by the control device so that is executed.

In the method of the present invention, it is preferable that the amount of gas sent from the adsorption tower in the depressurization step and introduced into the adsorption tower in the washing step is reduced as the helium concentration of the raw material helium gas is higher. Furthermore, it is preferable not to execute the cleaning step when the helium concentration of the raw material helium gas is equal to or higher than a predetermined set value.
As a result, the higher the helium concentration of the raw material helium gas, the smaller the amount of helium gas discharged as an off-gas after cleaning the inside of the adsorption tower, so that the recovery rate of helium gas can be improved. Therefore, when the helium concentration of the raw material helium gas fluctuates, for example, when the helium gas discharged from the optical fiber manufacturing process or the like is used as the raw material helium gas, it is possible to flexibly cope with the fluctuation of the raw material gas concentration.

In this case, the system according to the present invention executes the pressure reducing step for reducing the internal pressure in any of the adsorption towers after the first gas sending step and before the second gas sending step. A cleaning step of introducing the internal gas of the adsorption tower in the depressurization step and discharging it as an off-gas in any one of the adsorption towers after the desorption step and before the second gas introduction step Each of the on-off valves is controlled by the control device so that the flow rate control valve adjusts the flow rate of the gas flowing through the communication flow path, and the flow rate control valve is configured to perform a flow rate adjustment operation. An automatic valve having an actuator for adjustment and connected to the control device, and detecting a helium concentration of the raw material helium gas and a sensor connected to the control device In addition, the predetermined constant execution time of the cleaning process is stored in the control device, and the communication flow of the gas sent from the adsorption tower in the pressure reduction process and introduced into the adsorption tower in the cleaning process A predetermined correspondence between the flow rate in the channel and the helium concentration of the raw material helium gas is stored in the control device, sent from the adsorption tower in the depressurization step, and the adsorption in the cleaning step The on-off valve is controlled to execute the cleaning step for the execution time stored by the controller so that the amount of gas introduced into the tower decreases as the helium concentration detected by the sensor increases. In addition, the opening degree of the communication channel is preferably changed by the flow rate control valve based on the correspondence relationship.
Alternatively, in any of the adsorption towers after the first gas delivery step and before the second gas delivery step, a depressurization step for reducing the internal pressure is performed, and at the same time after the desorption step In any one of the adsorption towers in the state before the second gas introduction process, a cleaning process is performed in which the internal gas of the adsorption tower in the decompression process is introduced and then discharged as an off-gas. Each of the on-off valves is controlled by the control device to detect the helium concentration of the raw material helium gas and to be connected to the control device, and includes an execution time of the cleaning step and a helium concentration in the raw material helium gas. Is stored in the control device, sent from the adsorption tower in the pressure reduction step, and in the cleaning step Amount of gas introduced into the deposition tower, to be less, the higher the detected helium concentration by the sensor, preferably execution time of the cleaning process based on the correspondence relation by the control device is changed.

  In the method of the present invention, it is preferable that the off gas is led to an introduction flow path of the raw material helium gas to each of the adsorption towers so that the off gas is recycled as the raw material helium gas. Thereby, since helium gas contained in the off gas can be recycled, the recovery rate can be improved. In this case, the system of the present invention preferably includes a recycle channel for connecting the off-gas channel with the source gas introduction channel.

  In the method of the present invention, it is preferable that a helium concentration of the raw material helium gas introduced into each of the adsorption towers is 15 vol% or more. As a result, helium gas with the target purity can be efficiently obtained with less waste of helium gas. When the helium concentration of the raw material helium gas is mixed with the recycled off gas, it is introduced into the pressure swing adsorption device after mixing. Therefore, if it is 15 vol% or more after mixing, the target purity can be efficiently achieved by the method of the present invention. Helium gas can be obtained.

  In the method of the present invention, the repetition interval of the adsorption step in the pressure swing adsorption device so that the helium concentration of the purified helium gas discharged from each of the adsorption towers in the adsorption step becomes a target purity, for example, 99.999 vol% or more. Is preferably set. Further, in order to obtain high-purity helium gas, the adsorption process is repeated in the pressure swing adsorption device so that the helium concentration of the purified helium gas discharged from each of the adsorption towers in the adsorption process is 99.9999 vol% or more. An interval may be set.

  ADVANTAGE OF THE INVENTION According to this invention, when refine | purifying the helium gas containing an impurity with high purity with a small scale equipment, the method and system which can contribute to improving the recovery rate of helium gas can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS Structure explanatory drawing of the refinement | purification system which concerns on embodiment of this invention. The structure explanatory view of the pressure swing adsorption device concerning the embodiment of the present invention. Explanatory drawing of the control apparatus of the refinement | purification system which concerns on embodiment of this invention. The figure which shows the driving | running state (a)-(e) of the pressure swing adsorption | suction apparatus which concerns on embodiment of this invention. The figure which shows the driving | running state (f)-(j) of the pressure swing adsorption | suction apparatus which concerns on embodiment of this invention. The figure which shows the driving | running state (k)-(o) of the pressure swing adsorption | suction apparatus which concerns on embodiment of this invention. The figure which shows the driving | running state (p)-(t) of the pressure swing adsorption | suction apparatus which concerns on embodiment of this invention. The figure which shows the correspondence of the refinement | purification process process in each adsorption tower, and the state of an on-off valve in the operation state (a)-(e) of the pressure swing adsorption apparatus which concerns on embodiment of this invention. The figure which shows the correspondence of the refinement | purification process process in each adsorption tower, and the state of an on-off valve in the operation state (f)-(j) of the pressure swing adsorption apparatus which concerns on embodiment of this invention. The figure which shows the correspondence of the refinement | purification process process in each adsorption tower, and the state of an on-off valve in the operation state (k)-(o) of the pressure swing adsorption apparatus which concerns on embodiment of this invention. The figure which shows the correspondence of the refinement | purification process process in each adsorption tower, and the state of an on-off valve in the operation state (p)-(t) of the pressure swing adsorption apparatus which concerns on embodiment of this invention.

  A helium gas purification system α according to the embodiment of the present invention shown in FIG. 1 includes a pressure swing adsorption device 1 used for purifying a raw material helium gas G1 containing an impurity gas. As shown in FIG. 2, the pressure swing adsorption apparatus 1 has a plurality of adsorption towers 2a, 2b, 2c, and 2d. In the present embodiment, first to fourth adsorption towers 2a, 2b, 2c and 2d are provided, and gas passing ports 2a ', 2b' and 2c are provided at one end and the other end of each adsorption tower 2a, 2b, 2c and 2d. ', 2d', 2a ", 2b", 2c ", 2d" are formed.

  Adsorbents that preferentially adsorb the impurity gas over the helium gas are stored in the adsorption towers 2a, 2b, 2c, and 2d. The adsorbent is not particularly limited as long as it can adsorb the impurity gas preferentially over helium gas. For example, activated carbon, synthetic zeolite, carbon molecular sieve, alumina gel, or the like can be used.

  As shown in FIG. 2, a raw material gas introduction pipe 3, a purified gas pipe 4, and an off-gas pipe 5 are connected to the adsorption towers 2a, 2b, 2c, and 2d, respectively.

  One end of the source gas introduction pipe 3 is connected to a source of source helium gas G1, for example, an optical fiber manufacturing apparatus. The other end of the source gas introduction pipe 3 is branched into four so as to go to the first to fourth adsorption towers 2a, 2b, 2c, and 2d, and the gas passage port 2a 'at one end of each of the adsorption towers 2a, 2b, 2c, and 2d. 2b ', 2c' and 2d 'are connected via first to fourth on-off valves 6a, 6b, 6c and 6d which constitute the raw material gas introduction path on-off valves. Thereby, the raw material gas introduction pipe 3 constitutes a raw material gas introduction channel for introducing the raw material helium gas G1 into the adsorption towers 2a, 2b, 2c, and 2d. Further, the adsorption towers 2a, 2b are individually opened and closed by the first to fourth on-off valves 6a, 6b, 6c, 6d, respectively, between the adsorption towers 2a, 2b, 2c, 2d and the source gas introduction flow path. The raw material helium gas G1 can be individually introduced into each of 2c and 2d through the raw material gas introduction channel.

The raw material helium gas G1 is a mixed gas of helium gas and impurity gas. The raw material helium gas G1 introduced into each of the adsorption towers 2a, 2b, 2c and 2d preferably has a helium concentration of 15 vol% or more. In the present embodiment, the raw material helium gas G1 supplied from the supply source varies in concentration and flow rate. For example, the raw material helium gas G1 is a dilute helium gas containing air as an impurity gas. When the helium concentration is 30 vol%, the air concentration is 70 vol%, and the helium concentration varies between 15 and 70 vol%. The gas flow rate varies between 10 and 100 Nm ³ / h.

  One end of the purified gas pipe 4 is branched into four so as to go to the first to fourth adsorption towers 2a, 2b, 2c, and 2d, and gas passage ports 2a "at the other ends of the adsorption towers 2a, 2b, 2c, and 2d, 2b ″, 2c ″ and 2d ″ are connected via fifth to eighth on / off valves 7a, 7b, 7c and 7d constituting the purified gas path on / off valves. The other end of the purified gas pipe 4 is an outlet of the purified helium gas G2. Thus, the purified gas pipe 4 constitutes a purified gas flow path for discharging the purified helium gas G2 from each of the adsorption towers 2a, 2b, 2c, and 2d. Further, the adsorption towers 2a, 2b, 7c, 7d are individually opened and closed between the adsorption towers 2a, 2b, 2c, 2d and the purified gas flow path, thereby allowing the adsorption towers 2a, 2b, Purified helium gas G2 can be individually discharged and recovered from each of 2c and 2d. The use of the recovered purified helium gas G2 is not limited.

  A pressure control valve 26 for adjusting the back pressure is provided at the other end of the purified gas pipe 4, thereby adjusting the internal pressure in each of the adsorption towers 2 a, 2 b, 2 c and 2 d to a predetermined adsorption pressure in the adsorption process. be able to.

  One end of the off-gas pipe 5 is branched into four so as to go to the first to fourth adsorption towers 2a, 2b, 2c, and 2d, and an off-gas path opening / closing valve is provided at the gas passage ports 2a ', 2b', 2c ', and 2d'. The ninth to twelfth on-off valves 8a, 8b, 8c, and 8d are connected. The other end of the off-gas pipe 5 serves as an outlet for off-gas G3 and G3 ′. Thus, the offgas pipe 5 constitutes an offgas flow path for discharging offgas G3 and G3 ′ from the adsorption towers 2a, 2b, 2c and 2d, respectively. Further, the adsorption towers 2a, 2b, 2c are individually opened and closed by the ninth to twelfth on-off valves 8a, 8b, 8c, 8d, respectively, between the adsorption towers 2a, 2b, 2c, 2d and the off-gas flow path. 2d, off-gas G3 and G3 ′ can be discharged individually.

  A third flow rate control valve 18 for adjusting the flow rate is provided in the first recycle pipe 41 connected to the off-gas pipe 5. Thereby, the internal pressure in each of the adsorption towers 2a, 2b, 2c and 2d can be adjusted to the set pressure. In addition, the off-gas G3 can be adjusted to have a predetermined pressure in the pressure desorption process.

  A communication pipe 9 is provided that constitutes a communication channel for communicating any one of the adsorption towers 2a, 2b, 2c, and 2d with another one. The communication pipe 9 includes a first communication part 9a, a second communication part 9b, a third communication part 9c, and a fourth communication part 9d. One end of the first communication portion 9a is branched into four so as to go to the first to fourth adsorption towers 2a, 2b, 2c, and 2d, and the communication passage is opened and closed at the gas passage ports 2a ", 2b", 2c ", and 2d". The valves are connected via thirteenth to sixteenth on-off valves 10a, 10b, 10c, and 10d constituting the valves. One end of the second communication portion 9b is branched into four toward the first to fourth adsorption towers 2a, 2b, 2c, and 2d, and the communication passage is opened and closed at the gas passage ports 2a ", 2b", 2c ", and 2d". The valves are connected via 17th to 20th on-off valves 11a, 11b, 11c, and 11d constituting the valves. One end of the third communication portion 9c is branched into four toward the first to fourth adsorption towers 2a, 2b, 2c, and 2d, and the communication passage is opened and closed at the gas passage ports 2a ", 2b", 2c ", and 2d". It connects via the 21st-24th on-off valve 12a, 12b, 12c, 12d which comprises a valve. The other end of the second communication portion 9b and the other end of the third communication portion 9c constitute a 25th on-off valve 14 that constitutes a communication passage on-off valve, and a flow control valve that regulates the flow rate of gas flowing through the communication passage. 1 are connected to each other via a flow control valve 15. One end of the fourth communication portion 9d is the other end of the first communication portion 9a, the 26th on-off valve 16 constituting the communication passage on-off valve, and the second flow rate control valve for adjusting the gas flow rate flowing through the communication flow path. The flow control valve 17 is connected. The other end of the fourth communication portion 9d is connected to the purified gas pipe 4. Therefore, the thirteenth to twenty-sixth on-off valves 10a, 10b, 10c, 10d, 11a, 11b, 11c, 11d, 12a, 12b, 12c, 12d, 14, and 16 communicate with the adsorption towers 2a, 2b, 2c, and 2d, respectively. By individually opening and closing between the flow paths, the adsorption towers 2a, 2b, 2c, and 2d and either one of the adsorption towers 2a, 2b, 2c, and 2d are opened and communicated with each other. It is possible to switch to a state where there is no communication.

  1st to 26th on-off valves 6a, 6b, 6c, 6d, 7a, 7b, 7c, 7d, 8a, 8b, 8c, 8d, 10a, 10b, 10c, 10d, 11a, 11b, 11c, 11d, 12a, 12b , 12c, 12d, 14, and 16 are each constituted by a known automatic valve and have an opening / closing actuator such as a solenoid or a motor for operating the valve. As shown in FIG. 3, each on-off valve is connected to a control device 20 constituting the purification system α, and can be individually opened and closed by being controlled by the control device 20. The control device 20 can be configured by a computer.

  Each of the first, second, and third flow control valves 15, 17, and 18 is configured by a known automatic valve, and has a flow rate adjusting actuator such as a motor for operating the valve. As shown in FIG. 3, each flow control valve is connected to the control device 20, and can be individually adjusted by being controlled by the control device 20. The pressure control valve 26 is constituted by a known automatic valve, and has a pressure adjustment actuator such as a motor for operating the valve. As shown in FIG. 3, the pressure control valve 26 is connected to the control device 20, and can be individually controlled by being controlled by the control device 20.

  A flow rate sensor 21 for detecting the flow rate of the raw material helium gas G1 supplied from the supply source to the raw material gas introduction pipe 3, a buffer tank 22 for temporarily storing the raw material helium gas G1, and a storage amount measuring sensor 22a for the buffer tank 22 , The compressor 23, the concentration sensor 24 for detecting the helium concentration of the raw material helium gas G1 introduced into the adsorption towers 2a, 2b, 2c and 2d, and the raw material gas introduction pipe 3 are introduced into the adsorption towers 2a, 2b, 2c and 2d. A fourth flow rate control valve 25 for adjusting the flow rate of the raw material helium gas G1 is provided. The inside of the buffer tank 22 is set to a pressure lower than the atmospheric pressure and lower than the inside of the adsorption towers 2a, 2b, 2c, and 2d at the end of the pressure desorption / desorption process and the end of the cleaning process. The compressor 23 sucks the raw material helium gas G1 and raises the pressure to a predetermined pressure, for example, 0.8 to 0.9 MPa (gauge pressure). The temperature of the raw material helium gas G1 introduced into each of the adsorption towers 2a, 2b, 2c, and 2d is, for example, 0 to 40 ° C. The fourth flow control valve 25 is constituted by a known automatic valve, and has a flow rate adjusting actuator such as a motor for operating the valve.

  One end of the first recycle pipe 41 is connected to the off-gas pipe 5, and the other end of the first recycle pipe 41 is connected to the first switching valve 42. The first switching valve 42 selectively connects the first recycle pipe 41 to one end of the second recycle pipe 43 and one end of the first discharge pipe 44. The other end of the first discharge pipe 44 communicates with a normal pressure space under atmospheric pressure. The other end of the second recycle pipe 43 is connected to the second switching valve 45. The second switching valve 45 selectively connects the second recycle pipe 43 to one end of the third recycle pipe 46 and one end of the fourth recycle pipe 47. The other end of the third recycle pipe 46 is connected to the buffer tank 22. The other end of the fourth recycling pipe 47 is connected to the third switching valve 48. The third switching valve 48 selectively connects the fourth recycle pipe 47 to one end of the fifth recycle pipe 49 and one end of the second discharge pipe 44 '. The other end of the fifth recycle pipe 49 is connected to the buffer tank 22, and the other end of the second discharge pipe 44 'communicates with a normal pressure space under atmospheric pressure. A vacuum pump 50 is provided in the middle of the fourth recycling pipe 47. As a result, the off-gas flow path is communicated to the buffer tank 22 without using the vacuum pump 50 using the first to third switching valves 42, 45, and 48, and is communicated to the buffer tank 22 via the vacuum pump 50. And a state communicating with the normal pressure space via the first discharge pipe 44 and a state communicating with the normal pressure space via the second discharge pipe 44 '. The first to third switching valves 42, 45, and 48 may be automatic valves connected to the control device 20, and the operation may be controlled by the control device 20. Further, the vacuum pump 50 may be connected to the control device 20 and the operation may be controlled by the control device 20.

  The first to fifth recycle pipes 41, 43, 46, 47, and 49 constitute a recycle flow path for connecting the off gas flow path to the source gas introduction flow path via the buffer tank 22. Thereby, off-gas G3, G3 'can be guide | induced to the introduction flow path of raw material helium gas G1 to each adsorption tower 2a, 2b, 2c, 2d, and off-gas G3, G3' can be mixed in raw material helium gas G1. That is, the offgas G3 and G3 ′ can be recycled as the raw material helium gas G1. The off-gas G3 and G3 ′ may be released to the atmospheric pressure space.

  As shown in FIG. 3, a flow rate sensor 21, a storage amount measurement sensor 22 a, a concentration sensor 24, and a fourth flow rate control valve 25 are connected to the control device 20. Also connected to the control device 20 are pressure sensors 27a, 27b, 27c, 27d that detect the internal pressures of the adsorption towers 2a, 2b, 2c, 2d, an input device 28 such as a keyboard, and an output device 29 such as a monitor. .

  By temporarily storing the raw material helium gas G1 in the buffer tank 22, the composition fluctuation and flow rate fluctuation of the raw material helium gas G1 can be reduced. The buffer tank 22 is preferably composed of a balloon that is deformed in accordance with the amount of stored gas so that the capacity is variable. Further, the flow rate of the raw material helium gas G1 introduced into each of the adsorption towers 2a, 2b, 2c, and 2d is adjusted by controlling the fourth flow rate control valve 25 by a signal from the control device 20 and performing the flow rate adjustment operation. The Thereby, the flow rate of the raw material helium gas G1 introduced into the adsorption towers 2a, 2b, 2c, and 2d is controlled so as to coincide with the detected flow rate of the flow rate sensor 21 in normal times. When the amount of stored gas in the buffer tank 22 detected by the sensor 22a exceeds the upper limit set value, the raw material helium gas G1 introduced into each adsorption tower 2a, 2b, 2c, 2d is reduced so that the amount of stored gas decreases. The flow rate is assumed to be larger than the detection flow rate of the flow rate sensor 21. When the amount of stored gas in the buffer tank 22 detected by the sensor 22a is less than the lower limit set value, the raw material helium gas G1 introduced into each adsorption tower 2a, 2b, 2c, 2d is increased so that the amount of stored gas increases. The flow rate is assumed to be smaller than the detection flow rate of the flow rate sensor 21.

  In order to purify the raw material helium gas G1 using the pressure swing adsorption device 1, the raw material helium gas G1 is sequentially introduced into each of the adsorption towers 2a, 2b, 2c, and 2d. In each of the adsorption towers 2a, 2b, 2c, and 2d, a purification process cycle that sequentially executes a plurality of purification process steps is repeated.

  In the present embodiment, as a plurality of purification treatment steps constituting one purification treatment cycle in the pressure swing adsorption device 1, an adsorption step, a first gas delivery step, a pressure reduction step, a second gas delivery step, a desorption step, and a washing The process, the second gas introduction process, the first gas introduction process, and the pressure increasing process are sequentially executed. Although the desorption process of this embodiment performs a pressure desorption process and a vacuum desorption process, it may execute only a vacuum desorption process. In this embodiment, a standby state is provided between the second gas introduction step and the first gas introduction step, but the standby state may not be provided depending on the time required for each step. The execution time of each purification treatment step may be determined in advance through experiments according to the required purity and recovery rate of the purified helium gas G2. The execution timings of the purification process steps in the adsorption towers 2a, 2b, 2c, and 2d are different from each other. Thereby, in the pressure swing adsorption apparatus 1, as shown in FIGS. 4A to 4D, operation states (a) to (t) in which the purification treatment steps in the adsorption towers 2a, 2b, 2c, and 2d are different from each other are sequentially realized. The purified helium gas G2 is continuously discharged. The arrows in FIGS. 4A to 4D indicate the direction of gas flow.

  In order to sequentially perform the purification process steps in the pressure swing adsorption device 1, the control device 20 controls the first to 26th on-off valves 6a, 6b, 6c, 6d, 7a, 7b, 7c, 7d, 8a, 8b, 8c, 8d, 10a, 10b, 10c, 10d, 11a, 11b, 11c, 11d, 12a, 12b, 12c, 12d, 14, 16, and the first and second flow control valves 15 and 17 are respectively controlled. FIGS. 5A to 5D show the purification processing steps executed in the adsorption towers 2a, 2b, 2c, and 2d in the operating states (a) to (i) of the pressure swing adsorption device 1, and the first to 26th on-off valves, respectively. Correspondences with the respective states are shown, ◯ indicates the open state of the on-off valve, and x indicates the closed state of the on-off valve.

  In the operating state (a), the first, fifth, eleventh, eighteenth, twenty-fourth, and twenty-fifth open / close valves 6a, 7a, 8c, 11b, 12d, and 14 are opened, and the remaining open / close valves are closed. The adsorption process is executed in the first adsorption tower 2a by opening the first and fifth on-off valves 6a and 7a. By opening the 11th, 24th, and 25th on-off valves 11b, 12d, and 14, the first gas introduction step is executed in the second adsorption tower 2b, and the first gas delivery step is executed in the fourth adsorption tower 2d. The The desorption process is performed in the third adsorption tower 2c by opening the eighteenth on-off valve 8c. Here, the 3rd adsorption tower 2c leads to the vacuum pump 50, and the desorption process in the 3rd adsorption tower 2c is a vacuum desorption process.

  In the operating state (b), the first, fifth, eleventh, fourteenth, nineteenth, twenty-fourth, twenty-fifth, and twenty-sixth on-off valves 6a, 7a, 8c, 10b, 11c, 12d, 14, and 16 are opened. The remaining on-off valve is closed. By opening the first, fifth, fourteenth, and twenty-sixth on-off valves 6a, 7a, 10b, and 16, the first adsorption tower 2a performs the adsorption step following the operation state (a), and the second adsorption tower In 2b, the boosting process is executed. The eleventh, nineteenth, twenty-fourth, and twenty-fifth open / close valves 8c, 11c, 12d, and 14 are opened, whereby the cleaning step is performed in the third adsorption tower 2c, and the depressurization step is performed in the fourth adsorption tower 2d. . Here, the third adsorption tower 2c communicates with the vacuum pump 50, and the offgas G3 'discharged in the cleaning process is sucked by the vacuum pump 50.

  In the operating state (c), the first, fifth, fourteenth, nineteenth, twenty-fourth, twenty-fifth, twenty-sixth opening / closing valves 6a, 7a, 10b, 11c, 12d, 14, 16 are opened and the remaining opening / closing is performed. The valve is closed. By opening the first, fifth, fourteenth, and twenty-sixth on-off valves 6a, 7a, 10b, and 16, the first adsorption tower 2a performs the adsorption step following the operation state (b), and the second adsorption tower In 2b, the pressure increasing step is executed following the operation state (b). The 19th, 24th, and 25th on-off valves 11c, 12d, and 14 are opened, whereby the second gas introduction step is executed in the third adsorption tower 2c, and the second gas delivery step is executed in the fourth adsorption tower 2d. The Here, the vacuum pump 50 is unnecessary and may be stopped.

  In the operation state (d), the first, fifth, twelfth, fourteenth and twenty-sixth on-off valves 6a, 7a, 8d, 10b and 16 are opened, and the remaining on-off valves are closed. By opening the first, fifth, fourteenth, and twenty-sixth on-off valves 6a, 7a, 10b, and 16, the first adsorption tower 2a performs the adsorption step following the operation state (c), and the second adsorption tower In step 2b, the boosting step is executed following the operation state (c). The third adsorption tower 2c is in a standby state in which no purification process is performed. The desorption process is executed in the fourth adsorption tower 2d by opening the twelfth on-off valve 8d. The fourth adsorption tower 2d does not communicate with the vacuum pump 50, and the desorption process in the fourth adsorption tower 2d is a pressure desorption process. Here, the vacuum pump 50 is unnecessary and may be stopped.

  In the operation state (e), the open / close state of the on-off valve is the same as the operation state (d). As a result, the first adsorption tower 2a performs the adsorption process subsequent to the operation state (d), the second adsorption tower 2b performs the pressure increase process subsequent to the operation state (d), and the third adsorption tower 2c is on standby. State. Unlike the operation state (d), in the operation state (e), the fourth adsorption tower 2d is connected to the vacuum pump 50, and the desorption process in the fourth adsorption tower 2d is a vacuum desorption process.

  In the operating state (f), the second, sixth, twelfth, nineteenth, twenty-first, twenty-fifth on-off valves 6b, 7b, 8d, 11c, 12a, and 14 are opened, and the remaining on-off valves are closed. By opening the second and sixth on-off valves 6b and 7b, the adsorption step is executed in the second adsorption tower 2b. When the nineteenth, twenty-first and twenty-fifth on-off valves 11c, 12a and 14 are opened, the first gas delivery step is executed in the first adsorption tower 2a, and the first gas introduction step is executed in the third adsorption tower 2c. The The desorption process is executed in the fourth adsorption tower 2d by opening the twelfth on-off valve 8d. Here, following the operation state (e), the desorption process in the fourth adsorption tower 2d is a vacuum desorption process.

  In the operating state (g), the second, sixth, twelfth, fifteenth, twentieth, twenty-first, twenty-fifth, twenty-sixth on-off valves 6b, 7b, 8d, 10c, 11d, 12a, 14, 16 are opened. The remaining on-off valve is closed. When the second, sixth, fifteenth, and twenty-sixth on-off valves 6b, 7b, 10c, and 16 are opened, the second adsorption tower 2b performs the adsorption step following the operation state (f), and the third adsorption tower In 2c, the boosting process is executed. When the twelfth, twentieth, twenty-first, twenty-fifth open / close valves 8d, 11d, 12a, and 14 are opened, the depressurization step is executed in the first adsorption tower 2a, and the cleaning step is executed in the fourth adsorption tower 2d. . Here, the fourth adsorption tower 2d is connected to the vacuum pump 50, and the offgas G3 'discharged in the cleaning process is sucked by the vacuum pump 50.

  In the operating state (h), the second, sixth, fifteenth, twentieth, twenty-first, twenty-fifth, twenty-sixth on-off valves 6b, 7b, 10c, 11d, 12a, 14, 16 are opened and the remaining on-off The valve is closed. When the second, sixth, fifteenth, and twenty-sixth on-off valves 6b, 7b, 10c, and 16 are opened, the second adsorption tower 2b performs the adsorption step subsequent to the operation state (g), and the third adsorption tower In 2c, the pressure increasing step is executed following the operation state (g). By opening the twentieth, twenty-first, and twenty-fifth on-off valves 11d, 12a, and 14, the second gas delivery step is executed in the first adsorption tower 2a, and the second gas introduction step is executed in the fourth adsorption tower 2d. The Here, the vacuum pump 50 is unnecessary and may be stopped.

  In the operating state (i), the second, sixth, ninth, fifteenth, and twenty-sixth on-off valves 6b, 7b, 8a, 10c, and 16 are opened, and the remaining on-off valves are closed. When the second, sixth, fifteenth, and twenty-sixth on-off valves 6b, 7b, 10c, and 16 are opened, the second adsorption tower 2b performs the adsorption step following the operation state (h), and the third adsorption tower In step 2c, the pressure increasing step is executed following the operation state (h). By opening the ninth on-off valve 8a, the desorption process is executed in the first adsorption tower 2a. The first adsorption tower 2a is not connected to the vacuum pump 50, and the desorption process in the first adsorption tower 2a is a pressure desorption process. Here, the vacuum pump 50 is unnecessary and may be stopped. The fourth adsorption tower 2d is set in a standby state.

  In the operating state (j), the open / close state of the on-off valve is the same as the operating state (h). As a result, the second adsorption tower 2b performs the adsorption process subsequent to the operation state (h), the third adsorption tower 2c performs the pressure increase process subsequent to the operation state (h), and the fourth adsorption tower 2d waits. State. Unlike the operation state (h), in the operation state (j), the first adsorption tower 2a communicates with the vacuum pump 50, and the desorption process in the first adsorption tower 2a is the vacuum desorption process.

  In the operation state (k), the third, seventh, ninth, twentieth, twenty-second and twenty-fifth open / close valves 6c, 7c, 8a, 11d, 12b and 14 are opened, and the remaining on-off valves are closed. By opening the third and seventh on-off valves 6c and 7c, the adsorption step is executed in the third adsorption tower 2c. When the twentieth, twenty-second, and twenty-fifth open / close valves 11d, 12b, and 14 are opened, the first gas delivery step is executed in the second adsorption tower 2b, and the first gas introduction step is executed in the fourth adsorption tower 2d. The By opening the ninth on-off valve 8a, the desorption process is executed in the first adsorption tower 2a. Here, following the operation state (j), the desorption process in the first adsorption tower 2a is a vacuum desorption process.

  In the operating state (l), the third, seventh, ninth, sixteenth, seventeenth, twenty-second, twenty-fifth, twenty-sixth open / close valves 6c, 7c, 8a, 10d, 11a, 12b, 14, 16 are opened. The remaining on-off valve is closed. When the third, seventh, sixteenth, and twenty-sixth on-off valves 6c, 7c, 10d, and 16 are opened, the adsorption step is executed in the third adsorption tower 2c after the operation state (k), and the fourth adsorption tower The boosting process is executed in 2d. By opening the ninth, seventeenth, twenty-second, twenty-fifth open / close valves 8a, 11a, 12b, and 14, the washing process is executed in the first adsorption tower 2a, and the depressurization process is executed in the second adsorption tower 2d. . Here, the first adsorption tower 2a communicates with the vacuum pump 50, and the offgas G3 'discharged in the cleaning process is sucked by the vacuum pump 50.

  In the operating state (m), the third, seventh, sixteenth, seventeenth, twenty-second, twenty-fifth, twenty-sixth on-off valves 6c, 7c, 10d, 11a, 12b, 14, 16 are opened and the remaining on-off The valve is closed. When the third, seventh, sixteenth, and twenty-sixth on-off valves 6c, 7c, 10d, and 16 are opened, the adsorption step is executed in the third adsorption tower 2c following the operation state (l). In 2c, the pressure increasing step is executed following the operation state (l). By opening the 17th, 22nd, and 25th on-off valves 11a, 12b, and 14, the second gas introduction process is executed in the first adsorption tower 2a, and the second gas delivery process is executed in the second adsorption tower 2b. The Here, the vacuum pump 50 is unnecessary and may be stopped.

  In the operation state (n), the third, seventh, tenth, sixteenth and twenty-sixth on-off valves 6c, 7c, 8b, 10d, 16 are opened, and the remaining on-off valves are closed. When the third, seventh, sixteenth, and twenty-sixth on-off valves 6c, 7c, 10d, and 16 are opened, an adsorption step is executed in the third adsorption tower 2c following the operation state (m). In step 2d, the pressure increasing step is executed following the operation state (m). The desorption process is performed in the second adsorption tower 2b by opening the tenth on-off valve 8b. The second adsorption tower 2b does not communicate with the vacuum pump 50, and the desorption process in the second adsorption tower 2b is a pressure desorption process. Here, the vacuum pump 50 is unnecessary and may be stopped. The first adsorption tower 2d is in a standby state.

  In the operating state (o), the open / close state of the on-off valve is the same as the operating state (n). As a result, in the third adsorption tower 2c, the adsorption process is executed subsequent to the operation state (n), and in the fourth adsorption tower 2d, the pressure increase process is executed following the operation state (n), and the first adsorption tower 2a is in the standby state. State. Unlike the operation state (n), in the operation state (o), the second adsorption tower 2b communicates with the vacuum pump 50, and the desorption process in the second adsorption tower 2b is a vacuum desorption process.

  In the operating state (p), the fourth, eighth, tenth, seventeenth, twenty-third, and twenty-fifth on-off valves 6d, 7d, 8b, 11a, 12c, and 14 are opened, and the remaining on-off valves are closed. By opening the fourth and eighth on-off valves 6d and 7d, the adsorption step is executed in the fourth adsorption tower 2d. By opening the 17th, 23rd, and 25th on-off valves 11a, 12c, and 14, the first gas introduction step is executed in the first adsorption tower 2a, and the first gas delivery step is executed in the third adsorption tower 2c. The The desorption process is performed in the second adsorption tower 2a by opening the tenth on-off valve 8b. Here, following the operation state (o), the desorption process in the second adsorption tower 2b is a vacuum desorption process.

  In the operating state (q), the fourth, eighth, tenth, thirteenth, eighteenth, twenty-third, twenty-fifth, twenty-sixth on-off valves 6d, 7d, 8b, 10a, 11b, 12c, 14, 16 are opened. The remaining on-off valve is closed. The fourth, eighth, thirteenth, and twenty-sixth on-off valves 6d, 7d, 10a, and 16 are opened, whereby the pressure increasing step is executed in the first adsorption tower 2a, and in the fourth adsorption tower 2d, the operation state (p) is set. Subsequently, an adsorption process is performed. When the tenth, eighteenth, twenty-third, and twenty-fifth open / close valves 8b, 11b, 12c, and 14 are opened, the cleaning process is performed in the second adsorption tower 2b, and the depressurization process is performed in the third adsorption tower 2c. . Here, the second adsorption tower 2b communicates with the vacuum pump 50, and the offgas G3 'discharged in the cleaning process is sucked by the vacuum pump 50.

  In the operating state (r), the fourth, eighth, thirteenth, eighteenth, twenty-third, twenty-fifth, twenty-sixth on-off valves 6d, 7d, 10a, 11b, 12c, 14, 16 are opened and the remaining on-off The valve is closed. By opening the fourth, eighth, thirteenth, and twenty-sixth on-off valves 6d, 7d, 10a, and 16, the first adsorption tower 2a executes the pressure increasing step following the operation state (q), and the fourth adsorption tower In 2d, the adsorption step is executed following the operation state (q). By opening the 18th, 23rd, and 25th on-off valves 11b, 12c, and 14, the second gas introduction process is executed in the second adsorption tower 2b, and the second gas delivery process is executed in the third adsorption tower 2c. The Here, the vacuum pump 50 is unnecessary and may be stopped.

  In the operating state (s), the fourth, eighth, eleventh, thirteenth, and twenty-sixth on-off valves 6d, 7d, 8c, 10a, and 16 are opened, and the remaining on-off valves are closed. By opening the fourth, eighth, eleventh, and twenty-sixth on-off valves 6d, 7d, 10a, and 16, the first adsorption tower 2a performs the pressure increasing step following the operation state (r), and the fourth adsorption tower In 2d, the adsorption step is executed following the operation state (r). The desorption process is executed in the third adsorption tower 2c by opening the eleventh on-off valve 8c. The third adsorption tower 2c does not communicate with the vacuum pump 50, and the desorption process in the third adsorption tower 2c is a pressure desorption process. Here, the vacuum pump 50 is unnecessary and may be stopped. The second adsorption tower 2b is in a standby state.

  In the operating state (t), the open / close state of the on-off valve is the same as the operating state (s). As a result, the pressure increasing step is executed following the operation state (s) in the first adsorption tower 2a, the adsorption step is executed following the operation state (s) in the fourth adsorption tower 2d, and the second adsorption tower 2b is on standby. State. Unlike the operation state (s), in the operation state (t), the third adsorption tower 2c is connected to the vacuum pump 50, and the desorption process in the third adsorption tower 2c is a vacuum desorption process.

  In operating states (a), (b), (e), (f), (g), (j), (k), (l), (o), (p), (q), (t) The first recycling pipe 41 and the second recycling pipe 43 are connected via the first switching valve 42, and the second recycling pipe 43 and the fourth recycling pipe 47 are connected via the second switching valve 45, The fourth recycle pipe 47 is connected to the fifth recycle pipe 49 or the second discharge pipe 44 ′ via the third switching valve 48. Thereby, the off-gas G3 and G3 ′ in the vacuum desorption process and the cleaning process can be led to the buffer tank 22 or the normal pressure space via the vacuum pump 50. In the operating states (c), (d), (h), (i), (m), (n), (r), (s), the first recycle pipe 41 is connected via the first switching valve 42. The second recycle pipe 43 or the first discharge pipe 44 is connected, and the second recycle pipe 43 and the third recycle pipe 46 are connected via the second switching valve 45. Thereby, the off gas G3 in the pressure desorption process can be led to the buffer tank 22 or the normal pressure space without passing through the vacuum pump 50.

  When the adsorption step is executed in any of the adsorption towers 2a, 2b, 2c, and 2d, the raw material helium gas G1 is introduced into the adsorption tower through the raw material gas introduction channel. The inside of the adsorption tower is pressurized to the adsorption pressure by the pressure of the raw material helium gas G1. The adsorption pressure can be adjusted by the pressure control valve 26. Thereby, the impurity gas contained in the introduced raw material helium gas G1 is adsorbed to the adsorbent under pressure. Further, the gas that is not adsorbed by the adsorbent is discharged as purified helium gas G2 from the inside of the adsorption tower through the purified gas channel. It is preferable to set the repetition interval of the adsorption process in the pressure swing adsorption device 1 so that the helium concentration of the purified helium gas G2 becomes the target concentration. The helium concentration of the purified helium gas G2 is preferably 99.999 vol% or more, and more preferably 99.9999 vol% or more. For example, the relationship between the concentration of the raw material helium gas G1 detected by the concentration sensor 24, the flow rate adjusted by the fourth flow control valve 25, the target concentration of the purified helium gas G2, and the repetition interval of the adsorption process is expressed as follows. What is necessary is just to set the repetition interval of the adsorption | suction process corresponding to detection density | concentration, adjustment flow volume, and target density | concentration based on the relationship previously calculated | required. The repetition interval of the adsorption process in the pressure swing adsorption device 1 can be set by determining the time of one cycle of the purification process cycle, and the setting change is performed by executing the adsorption process time and the desorption process in one cycle of the purification process cycle. Change the time.

  When the depressurization step is executed in any of the adsorption towers 2a, 2b, 2c, and 2d after the first gas delivery process and before the second gas delivery process, the interior of the adsorption tower is a communication channel, By leading to the inside of the adsorption tower in the washing step and the off-gas flow path, the pressure gradually decreases. Since the internal gas G4 ′ of the adsorption tower in the depressurization process is introduced into the adsorption tower in the cleaning process, the amount of decrease in the internal pressure of the adsorption tower in the depressurization process is the amount of gas introduced into the adsorption tower in the cleaning process. Corresponding to

  When the pressure desorption process is performed in any of the adsorption towers 2a, 2b, 2c, and 2d, the inside of the adsorption tower leads to an off-gas flow path, and the vacuum pump 50 is turned on by the first and second switching valves 42 and 45. It is switched between a state communicating with the buffer tank 22 without being interposed and a state communicating with the normal pressure space via the first discharge pipe 44. The internal pressure of the adsorption tower is reduced to the pressure adjusted by the third flow rate control valve 18, and the impurity gas is desorbed from the adsorbent. The desorbed impurity gas is discharged as an off gas G3 from the inside of the adsorption tower through the off gas flow path. The pressure inside the adsorption tower at the end of the pressure desorption process is such that off-gas G3 flows through the recycle channel by its own pressure in the desorption process and reaches the buffer tank 22 or from the first discharge pipe 44 to the atmospheric pressure space. The pressure is slightly higher than atmospheric pressure so as to be released.

  When the vacuum desorption process is executed in any of the adsorption towers 2a, 2b, 2c, and 2d, the inside of the adsorption tower is connected to the off-gas flow path, and further, the first to third switching valves 42, 45, and 48 are used for vacuuming. The state is switched between a state communicating with the buffer tank 22 via the pump 50 and a state communicating with the normal pressure space via the second discharge pipe 44 '. Thereby, the internal pressure of the adsorption tower is reduced to less than atmospheric pressure by the vacuum pump 50, and the impurity gas is desorbed from the adsorbent. The desorbed impurity gas is sucked by the vacuum pump 50 and is discharged from the inside of the adsorption tower as an off gas G3 through the off gas flow path. The off-gas G3 flows through the recycle channel and reaches the buffer tank 22 or is discharged from the second discharge pipe 44 'to the normal pressure space.

  When the pressure increasing step is executed in any of the adsorption towers 2a, 2b, 2c, and 2d, the inside of the adsorption tower communicates with the inside of the adsorption tower in the adsorption process via the communication channel. At this time, a part of the purified helium gas G2 discharged from the adsorption tower in the adsorption process is introduced into the adsorption tower in the pressure increasing process. As a result, the inside of the adsorption tower in the pressure increasing step is pressurized and the pressure rises to the adsorption pressure or near the adsorption pressure.

  In each purification processing cycle, the first gas delivery step for delivering the internal gas from any of the adsorption towers 2a, 2b, 2c, 2d after the adsorption step and before the desorption step is performed, A first gas introduction step is performed in which the sent internal gas is introduced into any one of the adsorption towers 2a, 2b, 2c, and 2d after the desorption step and before the pressure increasing step. The inside of the adsorption tower in the first gas delivery step and the inside of the adsorption tower in the first gas introduction step communicate with each other, so that the internal pressure of the adsorption tower in the first gas delivery step and the first gas introduction step are present. The difference with the internal pressure of the adsorption tower is reduced. In other words, the internal gas sent from the adsorption tower in the first gas delivery process is introduced into the adsorption tower in the first gas introduction process, thereby reducing the internal pressure of the adsorption tower in the first gas delivery process. Then, the internal pressure of the adsorption tower in the first gas introduction process increases. In this embodiment, the difference between the internal pressure of the adsorption tower in the first gas delivery process and the internal pressure of the adsorption tower in the first gas introduction process remains at the completion of the first gas delivery process and the first gas introduction process. However, both internal pressures may be equalized.

  In each purification processing cycle, when the second gas delivery step for delivering the internal gas from any of the adsorption towers 2a, 2b, 2c, and 2d after the first gas delivery step and before the desorption step is executed. At the same time, a second gas introduction step is performed for introducing the delivered internal gas into any one of the adsorption towers 2a, 2b, 2c, and 2d after the desorption step and before the first gas delivery step. The The inside of the adsorption tower in the second gas delivery step and the inside of the adsorption tower in the second gas introduction step communicate with each other, so that the internal pressure of the adsorption tower in the second gas delivery step and the second gas introduction step are present. The difference with the internal pressure of the adsorption tower is reduced. In other words, the internal gas delivered from the adsorption tower in the second gas delivery process is introduced into the adsorption tower in the second gas introduction process, thereby reducing the internal pressure of the adsorption tower in the second gas delivery process. Then, the internal pressure of the adsorption tower in the second gas introduction process increases. In the present embodiment, the difference between the internal pressure of the adsorption tower in the second gas delivery step and the internal pressure of the adsorption tower in the second gas introduction step is not present when the second gas delivery step and the second gas introduction step are completed. Both internal pressures are equalized, but a difference between both internal pressures may be left.

  Thereby, the difference in the internal pressure of the adsorption tower is reduced between the adsorption step and the decompression step and between the decompression step and the desorption step. By reducing the difference in the internal pressure of the adsorption tower, the internal gas of the adsorption tower in the first and second gas delivery processes is used to increase the internal pressure of the adsorption tower in the first and second gas introduction processes. Thus, the impurity gas contained in the internal gas is adsorbed by the adsorbent, and the purified helium gas that is not adsorbed by the adsorbent can be recovered.

  In order to introduce the internal gas of the adsorption tower in the first gas delivery process into the adsorption tower in the first gas introduction process, one of the open / close valves of the communication channel is opened. Therefore, the amount of gas introduced into the adsorption tower in the first gas introduction step corresponds to the product of the execution time of the first gas delivery step or the first gas introduction step and the gas flow rate flowing through the communication channel. The execution times of the first gas delivery step and the first gas introduction step of the present embodiment are set to a predetermined time, and this constant execution time is stored in the control device 20.

  In the present embodiment, the amount of gas introduced into the adsorption tower in the first gas introduction step is changed by adjusting the flow rate of the gas flowing through the communication flow path using the first flow rate control valve 15. For this reason, the flow rate between the flow path of the gas G4 sent from the adsorption tower in the first gas delivery step and introduced into the adsorption tower in the first gas introduction step and the helium concentration of the raw material helium gas G1 are preliminarily determined. The determined correspondence relationship is stored in the control device 20.

  The higher the helium concentration of the raw material helium gas G1 detected by the concentration sensor 24, the more gas is sent from the adsorption tower in the first gas delivery process and introduced into the adsorption tower in the first gas introduction process. As described above, the on-off valve is controlled to execute the first gas delivery step and the first gas introduction step for the execution time stored by the control device 20, and based on the stored correspondence, the first flow rate control valve 15 The regulated gas flow rate is changed.

  The amount of gas introduced into the adsorption tower in the first gas introduction process is the pressure difference between the internal pressure at the start of the first gas delivery process and the internal pressure at the end of the first gas delivery process in the adsorption tower in the first gas delivery process. This corresponds to δP ′. Therefore, the amount of gas introduced into the adsorption tower in the first gas introduction process may be optimized by changing the pressure difference δP ′ according to the change in the detected helium concentration by the concentration sensor 24. For example, when the detected helium concentration is 30 vol% or more, the pressure difference δP ′ is 350 kPa, and when the detected helium concentration is 15 vol%, the gas flow rate and the raw material flowing through the communication channel such that the pressure difference δP ′ is 50 kPa. The relationship between the helium concentration of the helium gas G1 is predetermined. The adjustment of the gas flow rate by the first flow rate control valve 15 may be performed once in one cycle of the purification process, but may be performed once in a plurality of cycles if the concentration fluctuation of the raw material helium gas G1 is small.

  When the amount of gas introduced into the adsorption tower in the first gas introduction process is increased as the helium concentration in the raw material helium gas G1 is higher, the internal pressure of the adsorption tower at the start of the pressurization process following the first gas introduction process Changes. Therefore, when the internal pressure of the adsorption tower in the pressure increasing process is increased to the adsorption pressure, the amount of the purified helium gas G2 sent from the adsorption tower in the adsorption process and introduced into the adsorption tower in the pressure increasing process is also changed. preferable. In this case, in the pressure increasing process, the time of the pressure increasing process may be set to a predetermined value, and the flow rate of the gas flowing through the communication channel may be adjusted by the second flow rate control valve 17. Therefore, the relationship between the flow rate of gas flowing through the communication flow path adjusted by the second flow rate control valve 17 and the helium concentration of the raw material helium gas G1 may be determined in advance by experiments.

As a modification for increasing the amount of gas introduced into the adsorption tower in the first gas introduction step as the helium concentration in the raw material helium gas G1 is higher, the execution time of the first gas delivery step and the first gas introduction step is You may adjust. In this case, the flow rate control by the first flow rate control valve 15 is unnecessary because the gas flow rate flowing through the communication flow path is constant.
That is, the amount of gas introduced into the adsorption tower in the first gas introduction step corresponds to the product of the execution time of the first gas delivery step and the first gas introduction step and the gas flow rate flowing through the communication channel. By adjusting the execution time of the gas delivery process and the first gas introduction process, the amount of gas can be changed.
Therefore, a predetermined correspondence relationship between the execution time of the first gas delivery step and the first gas introduction step and the helium concentration in the raw material helium gas G1 is stored in the control device 20. The higher the helium concentration of the raw material helium gas G1 detected by the concentration sensor 24, the more gas is sent from the adsorption tower in the first gas delivery process and introduced into the adsorption tower in the first gas introduction process. As described above, the execution time of the first gas delivery process and the first gas introduction process based on the correspondence stored by the control device 20, that is, the control time of the on-off valve for the first gas delivery process and the first gas introduction process. Be changed. In addition, what is necessary is just to change the execution time of a pressure | voltage rise and a desorption process, when not changing the execution time of an adsorption | suction process when changing the execution time of a 1st gas delivery process and a 1st gas introduction process. Others may be controlled similarly to the embodiment.

  In order to introduce the internal gas of the adsorption tower in the second gas delivery process into the adsorption tower in the second gas introduction process, one of the open / close valves of the communication channel is opened. In the present embodiment, the second gas delivery step and the second gas introduction step until the internal pressure of the adsorption tower in the second gas delivery step and the internal pressure of the adsorption tower in the second gas introduction step are equalized. Is executed.

  At the same time that the depressurization step is performed in any of the adsorption towers 2a, 2b, 2c, and 2d, another adsorption tower 2a, 2b, 2c, and 2d in a state after the desorption step and before the second gas introduction step is performed. In either case, a cleaning process is performed. The interiors of the adsorption towers 2a, 2b, 2c, and 2d in the cleaning process are communicated with the interiors of the adsorption towers 2a, 2b, 2c, and 2d in the decompression process through a communication channel, and also communicated with the off-gas channel. As a result, the internal gas G4 ′ delivered from the adsorption tower in the depressurization step is introduced into the adsorption tower in the cleaning step and then discharged as off-gas G3 ′. The off-gas G3 ′ discharged from the adsorption tower in the cleaning process contains helium gas contained in the internal gas G4 ′ of the adsorption tower in the decompression process. The inside of the adsorption tower in the cleaning step is in a state where it is communicated from the off gas flow path to the buffer tank 22 via the vacuum pump 50 by the first to third switching valves 42, 45, and 48, and via the second discharge pipe 44 '. Thus, the state can be switched to a state leading to the normal pressure space. As a result, the off-gas G3 ′ is sucked into the vacuum pump 50, flows through the recycle flow path, reaches the buffer tank 22, or is discharged from the second discharge pipe 44 ′ into the normal pressure space. The inside of the adsorption tower in the cleaning process may not be communicated with the vacuum pump 50. In this case, the buffer tank 22 is connected to the off-gas flow path by the first and second switching valves 42 and 45 without the vacuum pump 50. And the off-gas G3 ′ reaches the buffer tank 22 via the recycle flow path, or passes through the first discharge pipe 44. Through the atmospheric pressure space.

  In the pressure swing adsorption apparatus 1, the amount of gas sent from the adsorption tower in the depressurization process and introduced into the adsorption tower in the cleaning process is the helium of the raw material helium gas G1 introduced into the adsorption towers 2a, 2b, 2c, and 2d. The higher the concentration, the less. Therefore, as described below, the execution time of the cleaning process is made constant, and the flow rate of the gas flowing through the communication flow path is adjusted by the first flow rate control valve 15. Furthermore, in the present embodiment, the cleaning step is executed when the helium concentration of the raw material helium gas G1 introduced into the adsorption towers 2a, 2b, 2c, and 2d is less than a predetermined set value, and the helium concentration is equal to or higher than the set value. When is, the cleaning process is not executed.

  In order to introduce the internal gas of the adsorption tower in the depressurization process into the adsorption tower in the washing process, one of the open / close valves of the communication flow path is opened. Therefore, the amount of gas introduced into the adsorption tower in the cleaning process corresponds to the product of the execution time of the cleaning process and the gas flow rate flowing through the communication channel. The execution time of the cleaning process of the present embodiment is set to a predetermined time, which is stored in the control device 20.

  The amount of gas introduced into the adsorption tower in the washing step can be changed by adjusting the flow rate of the gas flowing through the communication flow path using the first flow rate control valve 15. Therefore, a predetermined correspondence relationship between the flow rate of the gas G4 ′ introduced into the adsorption tower in the cleaning step in the communication flow path and the helium concentration of the raw material helium gas G1 is stored in the control device 20.

  As the helium concentration of the raw material helium gas G1 detected by the concentration sensor 24 increases, the amount of gas sent from the adsorption tower in the depressurization process and introduced into the adsorption tower in the cleaning process decreases. The on / off valve is controlled to execute the cleaning process for the execution time stored in the above, and the regulated gas flow rate by the first flow rate control valve 15 is changed based on the stored correspondence. Further, when a predetermined set value of the helium concentration is stored in the control device 20 and the helium concentration detected by the concentration sensor 24 is equal to or greater than the stored set value, the adjustment gas flow rate by the first flow rate control valve 15 is set to zero. The cleaning process is not performed. When the cleaning process is not executed, the pressure reducing process is not executed.

  The amount of gas introduced into the adsorption tower in the cleaning process corresponds to the pressure difference δP between the internal pressure at the start of the cleaning process and the internal pressure at the end of the cleaning process in the adsorption tower in the decompression process. Therefore, the amount of gas introduced into the adsorption tower in the cleaning process may be optimized by changing the pressure difference δP according to the change in the detected helium concentration by the concentration sensor 24. For example, when the detected helium concentration is 50 vol% or more, it is assumed that the cleaning process is not performed with the regulated gas flow rate by the first flow rate control valve 15 being zero so that the pressure difference δP becomes zero. When the detected helium concentration is less than 50 vol%, the gas flow rate and the raw material helium flowing through the communication flow path adjusted by the first flow control valve 15 so that the pressure difference δP increases as the detected helium concentration decreases. The relationship between the helium concentration of the gas G1 may be determined in advance by experiment. For example, when the detected helium concentration is 30 vol%, the pressure difference δP is 50 kPa, and when the detected helium concentration is 15 vol%, the gas flow rate through the communication flow path and the raw material helium gas G1 are such that the pressure difference δP is 70 kPa. A relationship between the helium concentration is predetermined. The adjustment of the gas flow rate by the first flow rate control valve 15 may be performed once in one cycle of the purification process, but may be performed once in a plurality of cycles if the concentration fluctuation of the raw material helium gas G1 is small.

As a modification to reduce the amount of gas sent from the adsorption tower in the depressurization process and introduced into the adsorption tower in the cleaning process as the helium concentration in the raw material helium gas G1 is higher, the execution time of the cleaning process is adjusted. May be. In this case, the flow rate control by the first flow rate control valve 15 is unnecessary because the gas flow rate flowing through the communication flow path is constant.
That is, the amount of gas introduced into the adsorption tower in the cleaning process corresponds to the product of the execution time of the cleaning process and the gas flow rate flowing through the communication channel, so that the amount of gas can be adjusted by adjusting the execution time of the cleaning process. Can be changed.
Therefore, a predetermined correspondence relationship between the execution time of the cleaning process and the helium concentration in the raw material helium gas G1 is stored in the control device 20. As the helium concentration of the raw material helium gas G1 detected by the concentration sensor 24 increases, the amount of gas sent from the adsorption tower in the depressurization process and introduced into the adsorption tower in the cleaning process decreases. The execution time of the cleaning process, that is, the control time of the on-off valve for the cleaning process is changed on the basis of the correspondence relationship stored in (1). In addition, when changing the execution time of a washing | cleaning process, when not changing the execution time of an adsorption | suction process, what is necessary is just to change the execution time of a pressure | voltage rise and a desorption process. Others may be controlled similarly to the embodiment.

  According to the embodiment and the modification, the raw material helium gas G1 can be purified by repeating the purification process cycle using the pressure swing adsorption device 1, and the purified helium gas G2 can be continuously obtained. The internal pressure difference of the adsorption tower is reduced twice for each purification treatment cycle. By reducing the internal pressure difference of the adsorption tower, the internal gas of the adsorption tower in the first and second gas delivery processes is introduced into the adsorption tower in the first and second gas introduction processes, so that it is included in the internal gas. Thus, the purified helium gas that is not adsorbed by the adsorbent can be recovered. Moreover, a vacuum desorption process can be performed by reducing the inside of an adsorption tower to less than atmospheric pressure with a vacuum pump in a desorption process. The performance of the adsorbent can be recovered by the vacuum desorption process. By reducing the internal pressure difference of the adsorption tower twice in each purification treatment cycle and recovering the performance of the adsorbent by the vacuum desorption process, the recovery rate of helium gas can be greatly improved by a synergistic effect. Furthermore, the recovery rate of helium gas can be improved by increasing the amount of gas introduced into the adsorption tower in the first gas introduction step as the helium concentration in the raw material helium gas G1 is higher. Further, by reducing the amount of gas introduced into the adsorption tower in the cleaning process as the helium concentration of the raw material helium gas G1 is higher, it is possible to prevent the helium gas recovery rate from being unnecessarily lowered. Therefore, for example, when helium gas discharged from an optical fiber manufacturing process or the like is used as the raw material helium gas, it is possible to flexibly cope with the concentration fluctuation of the raw material gas and efficiently obtain the target purity helium gas. Moreover, the recovery rate can also be improved by recycling the helium gas contained in the offgas G3 and G3 ′.

[Example 1]
The raw material helium gas G1 was purified according to the above embodiment using the helium gas purification system α.
The raw material helium gas G1 had a helium concentration of 30.0 vol% and an air concentration as an impurity gas of 70.0 vol%.
The supply flow rate of the raw material helium gas G1 to the pressure swing adsorption device 1 was 300 NL / h.
Each of the adsorption towers 2a, 2b, 2c, and 2d is made of stainless steel, has a cylindrical shape with an inner diameter of 37 mm, an inner dimension height of 1000 mm, and a capacity of about 1 L. Each of the adsorption towers 2a, 2b, 2c, and 2d was packed with about 0.7 L of activated carbon and about 0.3 L of zeolite as adsorbents.
As the purification process in the pressure swing adsorption device 1, in each of the adsorption towers 2a, 2b, 2c and 2d, the adsorption process is 130 seconds, the first gas delivery process is 15 seconds, the decompression process is 25 seconds, and the second gas delivery process is performed. 15 seconds, pressure release desorption step for 10 seconds, vacuum desorption step for 80 seconds, cleaning step for 25 seconds, second gas introduction step for 15 seconds, standby state for 75 seconds, first gas introduction step for 15 seconds, pressure increase step Were sequentially executed for 115 seconds. One cycle time from the start of the operation state (a) to the end of the operation state (t) was 520 seconds.
The maximum internal pressure of the adsorption towers 2a, 2b, 2c and 2d in the adsorption process was set to 0.8 MPa (gauge pressure). The pressure difference between the internal pressure of the adsorption tower at the start of the first gas delivery step and the internal pressure of the adsorption tower at the end of the first gas delivery step was 350 kPa. The pressure difference between the adsorption tower internal pressure at the start of the decompression step and the adsorption tower internal pressure at the end was set to 50 kPa. The second gas delivery step and the second gas introduction step were performed until the internal pressures of the two adsorption towers in both steps became equal. The internal pressure of the adsorption tower at the end of the vacuum desorption process was -95 kPa (gauge pressure).
Off-gas G3 and G3 'were discharged into the atmospheric pressure space without being recycled.
The flow rate of the purified helium gas G2 was 65.7 NL / h, the impurity concentration was 0.8 vol ppm (measured with GC-PDD manufactured by Shimadzu Corporation), and the helium recovery rate was 73.0%.

[Example 2]
The repetition interval of the adsorption process is changed by adjusting the adsorption process time in the pressure swing adsorption device 1 from the stable state of Example 1, the flow rate of the purified helium gas G2 is 68.2 NL / h, and the impurity concentration is 8.5 vol ppm. did. Others were the same as in Example 1. In this case, the recovery rate of helium was 75.8%.

Example 3
Assuming the concentration fluctuation of the raw material helium gas G1 from the stable state in Example 1, the helium concentration of the raw material helium gas G1 was changed to 50.0 vol% and the air concentration was changed to 50.0 vol%. The washing process and the decompression process were not performed. The repetition interval of the adsorption process was changed by adjusting the adsorption process time in the pressure swing adsorption apparatus 1, and the flow rate of the purified helium gas G2 was 121.4 NL / h, and the impurity concentration was 0.9 vol ppm. Others were the same as in Example 1. In this case, the helium recovery rate was 80.9%.

Example 4
Assuming the concentration fluctuation of the raw material helium gas G1 from the stable state in Example 1, the helium concentration of the raw material helium gas G1 was changed to 15.0 vol% and the air concentration was changed to 85.0 vol%. The pressure difference between the internal pressure of the adsorption tower at the start of the first gas delivery step and the internal pressure of the adsorption tower at the end of the first gas delivery step was 50 kPa. The pressure difference between the internal pressure of the adsorption tower at the start of the decompression step and the internal pressure at the end of the decompression step was set to 70 kPa. The repetition interval of the adsorption process was changed by adjusting the adsorption process time in the pressure swing adsorption apparatus 1, the flow rate of the purified helium gas G2 was 27.5 NL / h, and the impurity concentration was 0.9 vol ppm. Others were the same as in Example 1. In this case, the helium recovery rate was 61.2%.

Example 5
Assuming the concentration fluctuation of the raw material helium gas G1 from the stable state in Example 1, the helium concentration of the raw material helium gas G1 was changed to 50.0 vol% and the air concentration was changed to 50.0 vol%. By adjusting the adsorption process time in the pressure swing adsorption device 1, the repetition interval of the adsorption process was changed, the flow rate of the purified helium gas G2 was 116.1 NL / h, and the impurity concentration was 0.8 vol ppm. Others were the same as in Example 1. In this case, the helium recovery rate was 77.4%.

Example 6
50% of the off-gas G3, G3 ′ discharged from the pressure swing adsorption device 1 was mixed into the raw material helium gas G1 through the recycle channel. By adjusting the adsorption process time in the pressure swing adsorption device 1, the repetition interval of the adsorption process was changed, the flow rate of the purified helium gas G2 was 72.6 NL / h, and the impurity concentration was 0.8 vol ppm. Others were the same as in Example 1. In this case, the helium recovery rate in all steps was 80.7%.

Example 7
From the stable state of Example 1, the pressure difference between the adsorption tower internal pressure at the start of the first gas delivery step and the adsorption tower internal pressure at the end was set to 50 kPa. Further, the pressure difference between the internal pressure of the adsorption tower at the start of the decompression step and the internal pressure at the end of the decompression step was set to 70 kPa. The repetition interval of the adsorption process was changed by adjusting the adsorption process time in the pressure swing adsorption device 1, the flow rate of the purified helium gas G2 was 60.7 NL / h, and the impurity concentration was 0.9 vol ppm. Others were the same as in Example 1. In this case, the recovery rate of helium was 67.4%.

[Comparative Example 1]
The raw material helium gas G1 was purified by setting the internal pressure of the adsorption tower at the end of the pressure desorption process to 5 kPa (gauge pressure) without performing the first gas delivery process, the first gas introduction process, and the vacuum desorption process. . The repetition interval of the adsorption process was changed by adjusting the adsorption process time in the pressure swing adsorption apparatus 1, the flow rate of the purified helium gas G2 was 55.6 NL / h, and the impurity concentration was 0.9 vol ppm. Others were the same as in Example 1. In this case, the helium recovery rate was 61.8%.

[Comparative Example 2]
The raw material helium gas G1 was purified without performing the first gas delivery step and the first gas introduction step. By adjusting the adsorption process time in the pressure swing adsorption apparatus 1, the repetition interval of the adsorption process was changed, the flow rate of the purified helium gas G2 was 57.7 NL / h, and the impurity concentration was 0.8 vol ppm. Others were the same as in Example 1. In this case, the helium recovery rate was 64.1%.

[Comparative Example 3]
The raw material helium gas G1 was purified with the internal pressure of the adsorption tower at the end of the pressure desorption process being 5 kPa (gauge pressure) without performing the vacuum desorption process. By adjusting the adsorption process time in the pressure swing adsorption apparatus 1, the repetition interval of the adsorption process was changed, the flow rate of the purified helium gas G2 was 57.2 NL / h, and the impurity concentration was 0.9 vol ppm. Others were the same as in Example 1. In this case, the helium recovery rate was 63.6%.

[Comparative Example 4]
The first gas delivery step, the first gas introduction step, and the vacuum desorption step were not performed, and the internal pressure of the adsorption tower at the end of the pressure desorption step was 5 kPa (gauge pressure), and the raw material helium gas G1 was purified. . By adjusting the adsorption process time in the pressure swing adsorption apparatus 1, the repetition interval of the adsorption process was changed, the flow rate of the purified helium gas G2 was set to 64.7 NL / h, and the impurity concentration was set to 8.7 vol ppm. Others were the same as in Example 1. In this case, the helium recovery rate was 71.9%.

[Comparative Example 5]
The raw gas helium gas G1 was purified by setting the internal pressure of the adsorption tower at the end of the pressure desorption process to 5 kPa (gauge pressure) without performing the first gas delivery process, the first gas introduction process, and the vacuum desorption process. The repetition interval of the adsorption process was changed by adjusting the adsorption process time in the pressure swing adsorption apparatus 1, the flow rate of the purified helium gas G2 was 100.5 NL / h, and the impurity concentration was 0.9 vol ppm. Others were the same as in Example 3. In this case, the helium recovery rate was 67.0%.

[Comparative Example 6]
The first gas delivery step, the first gas introduction step, and the vacuum desorption step were not performed, and the internal pressure of the adsorption tower at the end of the pressure desorption step was 5 kPa (gauge pressure), and the raw material helium gas G1 was purified. . The repetition interval of the adsorption process was changed by adjusting the adsorption process time in the pressure swing adsorption apparatus 1, the flow rate of the purified helium gas G2 was 25.1 NL / h, and the impurity concentration was 0.9 vol ppm. Others were the same as in Example 4. In this case, the helium recovery rate was 55.7%.

From the difference in the helium recovery rate between Comparative Examples 1 and 2, the improvement in the helium recovery rate in the vacuum desorption process is about 2.3%. From the difference in the helium recovery rate between Comparative Examples 1 and 3, the degree of improvement in the helium recovery rate by increasing the number of reductions in the internal pressure difference of the adsorption tower from 1 to 2 is about 1.8%. Therefore, it has been conventionally thought that the improvement in the recovery rate will be about 4.1% even if the number of reductions in the internal pressure difference of the adsorption tower is increased and the vacuum desorption process is combined. However, from the difference between the helium recovery rate of Example 1 and the helium recovery rates of Comparative Examples 1 and 3, the improvement in the helium recovery rate by the combination is about 8.9% to 9.4%. Therefore, it can be confirmed that the combination produces a synergistic effect.
Further, from Examples 1 and 7, the amount of gas introduced from the adsorption tower in the first gas delivery process to the adsorption tower in the first gas introduction process is increased as the helium concentration of the raw material helium gas is increased, and the cleaning is performed. It can be confirmed that the recovery rate of helium gas is improved by reducing the amount of gas introduced into the adsorption tower in the process as the helium concentration of the raw material helium gas is higher.
From Examples 1 and 6, it can be confirmed that the off gas G3, G3 ′ is mixed into the raw material helium gas G1 through the recycle flow path, thereby improving the helium recovery rate.
From Examples 3 and 5, it can be confirmed that the helium recovery rate is improved by not performing the cleaning step when the concentration of the raw material gas helium is high.
From Examples 1 and 2, it can be confirmed that the helium recovery rate can be improved when it is not necessary to increase the purity of helium.
From Example 1 and Comparative Example 4, Example 3 and Comparative Example 5, Example 4 and Comparative Example 6, a combination of increasing the number of reductions in the internal pressure difference of the adsorption tower and the vacuum desorption step, purified helium It can be confirmed that the purity and helium recovery rate can be improved.

  The present invention is not limited to the above-described embodiments, examples, and modifications, and various modifications can be made without departing from the spirit of the present invention. For example, the number of adsorption towers in the adsorption apparatus is not limited to four towers, and may be three towers or five or more towers. Furthermore, the number of reductions in the internal pressure difference of the adsorption tower in each purification treatment cycle may be three or more. Moreover, in the said embodiment, although the pressurization process was performed by introduce | transducing purified helium gas into an adsorption tower, it may replace with refined helium gas and may implement a pressurization process by introduce | transducing source gas into an adsorption tower. Furthermore, not only the internal gas from the adsorption tower in the first gas delivery step but also the raw material gas may be introduced into the adsorption tower in the first gas introduction step.

  DESCRIPTION OF SYMBOLS 1 ... Pressure swing adsorption apparatus, 2a, 2b, 2c, 2d ... Adsorption tower, 3 ... Raw material gas introduction piping (raw material gas introduction flow path), 4 ... Purification gas piping (purification gas flow path), 5 ... Off gas piping (off gas) Flow path), 6a, 6b, 6c, 6d ... 1st to 4th on-off valve (raw material gas introduction path on-off valve), 7a, 7b, 7c, 7d ... 5th to 8th on-off valve (purified gas path on-off valve) , 8a, 8b, 8c, 8d ... 9th to 12th on-off valves (off gas passage on-off valves), 9 ... communication pipes (communication flow passages), 10a, 10b, 10c, 10d, 11a, 11b, 11c, 11d, 12a 12b, 12c, 12d, 14, 16 ... thirteenth to twenty-sixth on-off valves (communication passage on-off valves), 15 ... first flow control valve, 20 ... control device, 24 ... concentration sensor, 41, 43, 46, 47 49 ... 1st-5th recycle piping (recycle flow path).

Claims (13)

When purifying the raw material helium gas containing the impurity gas using a pressure swing adsorption device having a plurality of adsorption towers,
In each of the adsorption towers, an adsorbent that adsorbs the impurity gas in preference to helium gas is stored,
The raw helium gas is sequentially introduced into each of the adsorption towers,
In each of the adsorption towers, an adsorption step of adsorbing the impurity gas contained in the introduced raw material helium gas to the adsorbent under pressure and discharging purified helium gas that is not adsorbed by the adsorbent, and from the adsorbent A desorption process for desorbing the impurity gas and discharging it as an off-gas, and a pressure increasing process for increasing the internal pressure are sequentially executed.
A first gas delivery step for delivering an internal gas from any of the adsorption towers after the adsorption step and before the desorption step is performed, and at the same time, the delivered internal gas is removed after the desorption step. Performing a first gas introduction step for introducing into one of the adsorption towers in a state before the pressure raising step,
At the same time as performing the second gas delivery step for delivering the internal gas from any of the adsorption towers after the first gas delivery step and before the desorption step, the delivered internal gas is removed from the desorption step. Performing a second gas introduction step to be introduced into another of the adsorption towers after and before the first gas introduction step;
A method for purifying helium gas, wherein in the desorption step, the inside of the adsorption tower is depressurized to less than atmospheric pressure by a vacuum pump.   The amount of gas sent from the adsorption tower in the first gas delivery step and introduced into the adsorption tower in the first gas introduction step is increased as the helium concentration of the raw material helium gas is higher. The method for purifying helium gas described in 1.   At any one of the adsorption towers after the first gas delivery step and before the second gas delivery step, a depressurization step for reducing the internal pressure is performed, and at the same time after the desorption step and the first gas delivery step. 3. The cleaning step of discharging the internal gas of the adsorption tower in the depressurization step and discharging it as off-gas in another one of the adsorption towers in a state before the two-gas introduction step is performed. Helium gas purification method.   4. The helium gas according to claim 3, wherein the amount of gas sent from the adsorption tower in the depressurization step and introduced into the adsorption tower in the cleaning step is reduced as the helium concentration of the raw material helium gas is higher. Purification method.   The method for purifying helium gas according to claim 4, wherein the cleaning step is not executed when the helium concentration of the raw material helium gas is equal to or higher than a predetermined set value.   The helium gas according to any one of claims 1 to 5, wherein the offgas is led to a flow path for introducing the raw material helium gas into each of the adsorption towers so that the offgas is recycled as the raw material helium gas. Purification method. A pressure swing adsorption device having a plurality of adsorption towers;
Each of the adsorption towers contains an adsorbent that adsorbs the impurity gas preferentially over helium gas,
The pressure swing adsorption device includes a raw material gas introduction flow channel for introducing the raw material helium gas into each of the adsorption towers, a purified gas flow channel for discharging purified helium gas from each of the adsorption towers, and the adsorption tower An off-gas flow path for discharging off-gas from each of them, a communication flow path for communicating any one of the adsorption towers with another, and a separate space between each of the adsorption towers and the source gas introduction flow path A source gas introduction path opening / closing valve that opens and closes to each other, a purification gas path opening / closing valve that individually opens and closes between each of the adsorption towers and the purified gas flow path, and a space between each of the adsorption towers and the off gas flow path An off-gas path opening / closing valve that opens and closes, and a communication path opening / closing valve that individually opens and closes between each of the adsorption towers and the communication flow path,
Each of the opening / closing valves is an automatic valve having an opening / closing actuator so that the opening / closing operation can be performed individually, and is connected to a control device,
In each of the adsorption towers, an adsorption step of adsorbing the impurity gas contained in the introduced raw material helium gas to the adsorbent under pressure and discharging purified helium gas that is not adsorbed by the adsorbent, and from the adsorbent Each of the on-off valves is controlled by the control device so that a desorption step of desorbing the impurity gas and discharging it as an off-gas and a boosting step of increasing the internal pressure are sequentially performed,
A first gas delivery step for delivering an internal gas from any of the adsorption towers after the adsorption step and before the desorption step is performed, and at the same time, the delivered internal gas is removed after the desorption step. In order to execute the first gas introduction step to be introduced into any one of the adsorption towers in the state before the pressure increasing step, the inside of any of the adsorption towers in the first gas delivery step, and the first Each of the on-off valves is controlled by the control device so as to communicate with any other interior of the adsorption tower in one gas introduction step,
At the same time as performing the second gas delivery step for delivering the internal gas from any of the adsorption towers after the first gas delivery step and before the desorption step, the delivered internal gas is removed from the desorption step. Any of the adsorption towers in the second gas delivery step to perform a second gas introduction step after being introduced into another of the adsorption towers in a state before the first gas introduction step. Each of the on-off valves is controlled by the control device so that the inside of the gas and the inside of any one of the adsorption towers in the second gas introduction step communicate with each other,
A helium gas purification system comprising a vacuum pump for reducing the inside of the adsorption tower in the desorption step to less than atmospheric pressure. A flow control valve for adjusting the flow rate of the gas flowing through the communication channel;
The flow rate control valve is an automatic valve having a flow rate adjusting actuator so that a flow rate adjusting operation can be performed, and is connected to the control device,
A sensor for detecting a helium concentration of the raw material helium gas and connected to the control device;
A predetermined execution time of the first gas delivery step and the first gas introduction step is stored in the control device;
Between the flow rate of the gas sent from the adsorption tower in the first gas delivery step and introduced into the adsorption tower in the first gas introduction step in the communication channel and the helium concentration of the raw helium gas Is stored in the control device,
The amount of gas delivered from the adsorption tower in the first gas delivery process and introduced into the adsorption tower in the first gas introduction process is increased as the helium concentration detected by the sensor increases. The on-off valve is controlled to execute the first gas delivery step and the first gas introduction step for the execution time stored by the control device, and the communication is performed by the flow rate control valve based on the correspondence relationship. The method for purifying helium gas according to claim 7, wherein the opening degree of the flow path is changed. A sensor for detecting a helium concentration of the raw material helium gas and connected to the control device;
A predetermined correspondence between the execution time of the first gas delivery step and the first gas introduction step and the helium concentration in the raw material helium gas is stored in the control device,
The amount of gas delivered from the adsorption tower in the first gas delivery process and introduced into the adsorption tower in the first gas introduction process is increased as the helium concentration detected by the sensor increases. The helium gas purification system according to claim 7, wherein an execution time of the first gas delivery step and the first gas introduction step is changed by the control device based on the correspondence.   In any of the adsorption towers after the first gas delivery step and before the second gas delivery step, a depressurization step for reducing the internal pressure is performed, and at the same time after the desorption step. In any one of the adsorption towers in a state before the second gas introduction step, the cleaning step is performed in which the internal gas of the adsorption tower in the decompression step is introduced and then discharged as an off-gas. The helium gas purification system according to any one of claims 7 to 9, wherein each of the on-off valves is controlled by a control device. In any of the adsorption towers after the first gas delivery step and before the second gas delivery step, a depressurization step for reducing the internal pressure is performed, and at the same time after the desorption step. In any one of the adsorption towers in a state before the second gas introduction step, the cleaning step is performed in which the internal gas of the adsorption tower in the decompression step is introduced and then discharged as an off-gas. Each of the on-off valves is controlled by a control device,
A flow control valve for adjusting the flow rate of the gas flowing through the communication channel;
The flow rate control valve is an automatic valve having a flow rate adjusting actuator so that a flow rate adjusting operation can be performed, and is connected to the control device,
A sensor for detecting a helium concentration of the raw material helium gas and connected to the control device;
A predetermined execution time of the cleaning step is stored in the control device;
Predetermined correspondence between the flow rate of the gas sent from the adsorption tower in the depressurization step and introduced into the adsorption tower in the cleaning step in the communication flow path and the helium concentration of the raw material helium gas A relationship is stored in the controller,
The amount of gas sent from the adsorption tower in the depressurization step and introduced into the adsorption tower in the washing step is stored by the control device so that the helium concentration detected by the sensor becomes smaller. The helium according to claim 7, wherein the on-off valve is controlled to execute the cleaning step only for the executed time, and the opening degree of the communication channel is changed by the flow rate control valve based on the correspondence relationship. Gas purification system. In any of the adsorption towers after the first gas delivery step and before the second gas delivery step, a depressurization step for reducing the internal pressure is performed, and at the same time after the desorption step. In any one of the adsorption towers in a state before the second gas introduction step, the cleaning step is performed in which the internal gas of the adsorption tower in the decompression step is introduced and then discharged as an off-gas. Each of the on-off valves is controlled by a control device,
A sensor for detecting a helium concentration of the raw material helium gas and connected to the control device;
A predetermined correspondence between the execution time of the cleaning step and the helium concentration in the raw material helium gas is stored in the control device,
The control device controls the apparatus so that the amount of gas delivered from the adsorption tower in the depressurization step and introduced into the adsorption tower in the cleaning step decreases as the helium concentration detected by the sensor increases. The helium gas purification system according to claim 7, wherein an execution time of the cleaning step is changed based on the correspondence.   The helium gas purification system according to any one of claims 7 to 12, further comprising a recycle channel for connecting the off-gas channel to the source gas introduction channel.

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