Helium recovery and purification apparatus and helium recovery and purification method

Abstract

To provide a helium recovery and purification system that enables more efficient recovery and purification of high-purity helium. [Solution] A helium recovery and purification apparatus is provided for recovering and purifying helium gas from a gas to be treated containing helium gas and impurity gas, comprising: a first separator that adsorbs and removes a portion of the impurity gas contained in the gas to be treated and extracts a first gas containing the helium gas; and a second separator arranged downstream of the first separator that adsorbs and removes at least a portion of the impurity gas and extracts a second gas containing the helium gas.

Description

Technical Field

[0001] The present disclosure relates to a helium recovery and purification apparatus and a helium recovery and purification method.

Background Art

[0002] Helium gas used in semiconductor manufacturing and the like is a scarce resource. Therefore, it is desirable to selectively recover and purify helium gas from the exhaust gas discharged from facilities that use helium.

[0003] Conventionally, as a method for recovering and purifying high-purity helium from a mixed gas containing helium, for example, a cryogenic separation method using gas-liquid equilibrium has been used (Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the recovery and purification of helium using the cryogenic separation method as in Patent Document 1, the separation and recovery of helium is carried out through a rectification process using the gas-liquid equilibrium of the components contained in the mixed gas. Although such helium recovery and purification using the cryogenic separation method enables the recovery and purification of relatively high-purity helium, it requires a large amount of energy for the recovery and purification process. Furthermore, since it includes a large rectification column, the apparatus can be large-scale. Therefore, there is a need for a method that can more efficiently recover and purify helium from the mixed gas.

[0006] The present disclosure has been made in view of such problems. That is, the main object of the present disclosure is to provide a helium recovery and purification apparatus and a helium recovery and purification method that enable efficient recovery and purification of high-purity helium gas. [Means for solving the problem]

[0007] To achieve the above objective, in one embodiment of this disclosure, A helium recovery and purification apparatus for recovering and purifying helium gas from a gas to be processed that contains helium gas and impurity gases, A first separator that adsorbs and removes a portion of the impurity gas contained in the gas to be processed and extracts the first gas containing the helium gas, A helium recovery and purification apparatus is provided, comprising a second separator located downstream of the first separator, which adsorbs and removes at least a portion of the impurity gas and extracts a second gas containing the helium gas.

[0008] Furthermore, in one embodiment of this disclosure, A helium recovery and purification method for recovering and purifying helium gas from a gas to be treated that contains helium gas and impurity gases, A first separation step involves adsorbing and removing a portion of the impurity gas contained in the gas to be processed, and extracting the first gas. A helium recovery and purification method is provided, which includes a second separation step of adsorbing and removing at least a portion of the impurity gas contained in the first gas and extracting a second gas containing the helium gas. [Effects of the Invention]

[0009] This disclosure provides a helium recovery and purification apparatus and a helium recovery and purification method that enable the efficient recovery and purification of high-purity helium. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram of the overall configuration of a helium recovery and purification apparatus according to the first embodiment of this disclosure. [Figure 2] Figure 2 is a schematic diagram illustrating an exemplary configuration of a separator according to a modified version of the first embodiment of this disclosure. [Figure 3]Figure 3 is a schematic diagram illustrating the configuration of a helium recovery and purification apparatus according to the second embodiment of this disclosure. [Figure 4] Figure 4 is a schematic diagram illustrating the configuration of a helium recovery and purification apparatus according to the second embodiment of this disclosure. [Figure 5] Figure 5 is a schematic diagram illustrating the configuration of a helium recovery and purification apparatus according to the third embodiment of this disclosure. [Figure 6] Figure 6 is a schematic diagram illustrating the configuration of a helium recovery and purification apparatus according to the third embodiment of this disclosure. [Figure 7] Figure 7 is a schematic flow chart illustrating the helium recovery and purification process according to the first embodiment of this disclosure. [Figure 8] Figure 8 is a schematic flow chart illustrating the helium recovery and purification process according to the second embodiment of this disclosure. [Figure 9] Figure 9 is a schematic flow chart illustrating the helium recovery and purification process according to the second embodiment of this disclosure. [Figure 10] Figure 10 is a schematic flow chart illustrating the helium recovery and purification process according to the third embodiment of this disclosure. [Figure 11] Figure 11 is a schematic flowchart illustrating the helium recovery and purification process according to a modified version of the third embodiment of this disclosure. [Modes for carrying out the invention]

[0011] Hereinafter, a helium recovery and purification apparatus and a helium recovery and purification method according to one embodiment of the present disclosure will be described with reference to the drawings. In each embodiment, the differences from those described in previous embodiments will be mainly described. In particular, similar effects and advantages due to similar configurations will not be mentioned sequentially for each embodiment. Among the components in the following embodiments, components not described in an independent claim will be described as optional components.

[0012] Furthermore, in the following description, terms indicating specific directions and positions are used as necessary. However, the use of these terms is for facilitating the understanding of the invention with reference to the drawings, and the technical scope of the present disclosure is not limited by the meanings of these terms. Unless otherwise specified, the same reference symbol or notation shall indicate the same member, part, or the same meaning content.

[0013] Also, terms such as "attached", "added", "connected", "coupled", and "interconnected", and similar terms, state that structures are directly or indirectly fixed or attached to each other by intervening elements, or that both are in a movable or rigid attachment or relationship, unless otherwise explicitly explained separately.

[0014] Furthermore, the features or benefits of the present disclosure are illustrated by referring to preferred embodiments. Such embodiments are described in sufficient detail to enable those skilled in the art to implement the present disclosure. It should also be understood that other embodiments can be utilized and that process or mechanical changes are possible without departing from the scope of the present disclosure. Therefore, the present disclosure is not explicitly limited to the preferred embodiments (either alone or in combination with other features) that exemplify non-limiting combinations of the possible features.

[0015] <Helium Recovery and Purification Device> [First Embodiment] FIG. 1 is a schematic diagram showing the configuration of a helium recovery and purification device according to the first embodiment of the present disclosure. The helium recovery and purification device 100 according to the first embodiment of the present disclosure removes impurity gas from a gas to be treated containing helium and impurity gas, and recovers and purifies helium gas. The helium recovery and purification device 100 mainly includes a first separator 30 and a second separator 50. Each of the first separator 30 and the second separator 50 may be configured to remove the impurity gas contained in the gas to be treated.

[0016] The first separator 30 and the second separator 50 may be fluidly connected to each other in this order. This means that the gas to be treated can flow from the first separator 30 to the second separator 50. For example, the first separator 30 and the second separator 50 may be fluidly connected to each other via piping or the like.

[0017] The first separator 30 and the second separator 50 do not necessarily have to be directly fluid-connected, and other components may be placed between each processor. For example, a tank capable of temporarily storing gas may be placed between the first separator 30 and the second separator 50. Also, a tank 20 capable of temporarily storing the gas to be treated may be placed upstream of the first separator 30. That is, a storage tank may be installed upstream of each processor, and gas may be supplied from the storage tank to each processor. By providing a storage tank, fluctuations in the flow rate of gas supplied to each processor can be suitably suppressed, and the supply of gas to each processor can be carried out more stably.

[0018] Furthermore, the piping that fluid-connects each processing unit may be equipped with valves, pumps, filters, pressure gauges, flow meters, concentration meters, and / or thermometers.

[0019] With the above configuration, the helium contained in the gas to be treated can be efficiently concentrated by removing impurity gas in stages in the first separator 30 and the second separator 50. Generally, when removing impurity gas from a gas to be treated, using cryogenic separation can suitably remove small amounts of impurity gas. On the other hand, removing large amounts of impurity gas from a gas to be treated requires a large rectification column, which can make the equipment larger in scale. In particular, cryogenic separation requires not only gas cooling but also rectification treatment, which can make the equipment configuration complex.

[0020] Furthermore, adsorption separation is a known method for removing impurity gases. However, generally, purifying high-purity helium gas using a single adsorption separator requires a large adsorption tower containing a large amount of adsorbent, as well as high adsorption pressure and long cycle times to increase the adsorption rate, posing challenges in terms of processing efficiency.

[0021] On the other hand, it has been found that the helium recovery and purification apparatus of this disclosure, by arranging two separators in series, can efficiently produce high-purity helium gas without excessively increasing the scale of the equipment compared to methods using cryogenic separation.

[0022] In the helium recovery and purification apparatus of this disclosure, impurity gases contained in the gas to be treated are removed stepwise as the gas passes through the first separator 30 and the second separator 50. This allows for the stepwise concentration of helium in the gas to be treated, ultimately enabling the acquisition of high-purity helium gas. Specifically, the first separator 30 removes a portion of the impurity gases contained in the gas to be treated, and extracts a first gas with a higher helium concentration than the gas to be treated. The first gas may then be introduced into the second separator 50. In the second separator 50, any remaining impurity gases in the first gas are further removed, thereby obtaining purified gas containing high-purity helium. In other words, by installing the second separator 50 downstream of the first separator 30, the second separator 50 can perform separation and removal of impurity gases with higher precision than the first separator 30. This improves the overall helium recovery and purification processing efficiency of the helium recovery and purification apparatus.

[0023] (Gas to be treated) In this disclosure, the gas to be treated is a mixed gas containing helium and impurity gases. The concentration of helium in the gas to be treated can be, for example, 0.1 volume% or more. Furthermore, there is no particular upper limit to the helium concentration. Although this is merely an example, the upper limit to the helium concentration can be, for example, 95 volume% or less, 50 volume% or less, or 30 volume% or less. In particular, the helium recovery and purification apparatus of this disclosure can suitably purify high-purity helium gas from a gas to be treated containing a low concentration of helium between 0.1 volume% and 10 volume%.

[0024] Impurity gas refers to gaseous components other than helium contained in the gas to be treated. The gas to be treated may be, for example, exhaust gas discharged from a semiconductor manufacturing process (e.g., CVD equipment). The components of the impurity gas contained in the gas to be treated may be components other than helium that can be contained in exhaust gas discharged in a semiconductor manufacturing process. The gas to be treated may contain at least one selected from the group consisting of air, CO, hydrocarbons, and gaseous components used in semiconductor manufacturing processes as impurity gas. Specifically, the gas to be treated may contain at least one component selected from the group consisting of H2O, CO2, N2, H2, O2, Ar, CO, and hydrocarbons as impurity gas. Examples of hydrocarbons, although not particularly limited, include methane, ethane, ethylene, propane, propylene, butylene, methylpropene, dimethyl ether, and acetylene.

[0025] Generally, exhaust gases emitted from semiconductor manufacturing processes and other processes may be diluted with large amounts of nitrogen gas or air to dilute harmful components. Therefore, the gas to be treated may be a mixed gas mainly composed of N2 and containing a low concentration of helium. In other words, the gas to be treated may be a mixed gas containing at least a small amount of helium and a large amount of nitrogen. As described above, the helium recovery and purification apparatus of this disclosure has a configuration that removes impurity gases in stages using a first separator and a second separator. With such a configuration, helium can be efficiently recovered and purified even from a gas to be treated that contains a large amount of impurity gas such as N2 and has a low helium concentration.

[0026] For example, the helium recovery and purification apparatus of this disclosure can suitably obtain high-purity helium gas from a gas to be treated in which the N2 concentration is 50% by volume or more, 60% by volume or more, or 70% by volume or more. Furthermore, the upper limit of the N2 concentration contained in the gas to be treated may be, for example, 99.9% by volume or less.

[0027] The first separator 30 and the second separator 50 provided in the helium recovery and purification apparatus of this disclosure will be described in more detail below.

[0028] (1st separator) The first separator 30 may, for example, adsorb and remove a portion of the impurity gas contained in the gas to be treated by a pressure swing adsorption (PSA) method. In this embodiment, the first separator 30 may also be called the first adsorption separator. As the first separator 30 using the PSA method, a known PSA equipment configuration may be used. As shown in Figure 2, the first separator 30 may be equipped with an adsorption tower capable of adsorbing and removing predetermined components contained as impurity gases in the gas to be treated. Non-adsorbed gases, including helium, that are not captured by the adsorbent are extracted as the first gas. That is, the first separator 30 may be configured to extract a first gas having a higher helium concentration than the gas to be treated by adsorbing and removing a portion of the impurity gas from the gas to be treated. An exemplary configuration of the first separator 30 will be described below.

[0029] The first separator 30 can be a PSA type separator using a compressor, a PVSA (Pressure Vacuum Swing Absorption) type separator using a high-pressure blower and a vacuum pump, or a VSA (Vacuum Swing Absorption) type separator using a low-pressure blower and a vacuum pump.

[0030] The first separator 30 may include an adsorption tower, a supply line for supplying the gas to be treated to the adsorption tower, a transfer line for transferring the first gas extracted from the adsorption tower toward a downstream processor, and a discharge line for discharging off-gas resulting from the desorption of adsorbed impurities. For example, the helium recovery and purification apparatus may include a tank 35 downstream of the first separator 30, in which the first gas may be temporarily stored. The transfer line may be configured to transfer the first gas to the tank 35.

[0031] The adsorption tower of the first separator 30 is filled with an adsorbent that can selectively adsorb specific components of impurity gases contained in the gas to be treated. A portion of the impurity gases contained in the gas to be treated introduced into the adsorption tower is captured by the adsorbent under increased pressure. Non-adsorbed gases, including helium, that are not captured by the adsorbent are sent to the outside of the adsorption tower as the first gas via the transfer line. Subsequently, by decreasing the pressure inside the adsorption tower, the impurity gas components that were adsorbed on the adsorbent are desorbed from the adsorbent and discharged to the outside of the adsorption tower via the discharge line. The adsorbent is regenerated by this desorption. After that, by increasing the pressure inside the adsorption tower again, the adsorption of impurity gases in the gas to be treated can be performed again. In this way, the first separator 30 can adsorb and remove a portion of the impurity gases from the gas to be treated by repeatedly increasing and decreasing the pressure.

[0032] The number of adsorption towers is not particularly limited, and one or more adsorption towers may be provided. For example, the first separator 30 may use one to five adsorption towers. When multiple adsorption towers are provided, the adsorption and desorption processes may be staggered in each adsorption tower so that the adsorption process is performed in at least one adsorption tower while the helium recovery and purification apparatus is in operation. This makes it possible to simultaneously perform the adsorption and desorption of impurity gases in different adsorption towers, thereby enabling the continuous extraction of the first gas, which is an unadsorbed gas. Figure 2 is a schematic diagram of the first separator 30 according to one embodiment of the present disclosure. If processing efficiency is given greater importance, it is particularly preferable that three or more adsorption towers 301 are provided, as shown in Figure 2. For example, the first separator 30 may be equipped with three to five adsorption towers 301.

[0033] When operating the first separator 30, various control factors such as flow rate, cycle time, operating pressure and temperature of the adsorption tower, and the design of the adsorption tower size can be appropriately set considering the type and concentration of components of the gas to be treated. Here, cycle time refers to the time required for one cycle, from the start of supplying the raw material gas in the adsorption process to the completion of discharge of the off-gas in the desorption process. Although this is merely an example, if the helium concentration of the gas to be treated is 0.1 volume% or more and 10 volume% or less, the cycle time may be in the range of 10 seconds or more and 100 seconds or less. The flow rate of the gas to be treated can be appropriately changed depending on the size of the adsorption tower, the specifications of the vacuum pump, etc., but may be in the range of 50 L / min or more and 120 L / min or less. In addition, for each adsorption tower, the adsorption pressure may be in the range of 10 kPa or more and 60 kPa or less, and the desorption pressure may be in the range of -100 kPa or more and -80 kPa or less. According to the processing conditions described above, helium can be efficiently recovered and purified from the target gas containing low concentrations of helium.

[0034] The type of adsorbent packed into the adsorption tower of the first separator 30 may be appropriately selected according to the components of the impurity gas to be removed. For example, the first separator 30 may be capable of removing impurity gases that are difficult to remove in the second separator 50 located downstream of the first separator 30. The components of the impurity gas removed in the first separator 30 may be different from those removed in the second separator 50. Alternatively, the impurity gas removed in the first separator 30 may contain the same components as the impurity gas components removed in the second separator 50. In other words, the same impurity gas components may be removed in stages by the first separator 30 and the second separator 50.

[0035] For example, the impurity gas components removed by the first separator 30 may be components that are present in high concentrations in the gas to be treated. In other words, the first separator 30 may remove impurity gas components that are present in high concentrations in the gas to be treated, and the second separator 50 may remove impurity gas components that are present in low concentrations in the gas to be treated. This allows a large amount of impurity gas contained in the gas to be treated to be removed by the first separator 30, significantly increasing the helium concentration of the first gas. In other words, the helium concentration of the gas introduced into the second separator 50 can be increased. The second separator 50 removes low-concentration impurity gases from a gas containing high concentrations of helium, and the efficiency of impurity gas removal in the second separator 50 can be increased. In this way, helium gas can be efficiently recovered and purified from a gas to be treated with a low helium concentration. In this configuration, the removal of impurity gases in the first separator 30 can also be understood as a pretreatment to more favorably carry out the separation and removal of impurity gases in the second separator 50.

[0036] For example, the component adsorbed and removed in the first separator 30 may be at least one selected from the group consisting of H2O, CO, N2, O2, H2, Ar, hydrocarbons, and CO2. That is, the adsorbent packed into the adsorption column of the first separator 30 may be a known material capable of adsorbing at least one selected from the group consisting of H2O, CO, N2, O2, H2, Ar, hydrocarbons, and CO2. Examples of such adsorbents include type X or type A zeolite, activated carbon, porous silica, porous alumina, and / or metal-organic structures.

[0037] When multiple types of components are adsorbed and removed in the first separator 30, the adsorption column may be filled with adsorbents suitable for the adsorption of each component in order. That is, multiple types of adsorbents may be filled into the adsorption column in any order.

[0038] (Second separator) The second separator 50, like the first separator 30, may be configured to adsorb and remove at least a portion of the impurity gases remaining in the processed gas by pressure swing adsorption (PSA). That is, the second separator 50, like the first separator 30, may be equipped with an adsorption tower capable of adsorbing and removing predetermined components contained as impurity gases in the gas being processed.

[0039] The number of adsorption towers in the second separator 50 is not particularly limited, and it may be equipped with one or more adsorption towers. For example, the second separator 50 may use one to five adsorption towers. If processing efficiency is given greater importance, it is particularly preferable to have three or more adsorption towers. For example, the second separator 30 may be equipped with three to five adsorption towers.

[0040] The type of adsorbent packed into the adsorption column of the second separator 50 may be appropriately selected according to the components of the impurity gas to be removed. For example, it is preferable that the second separator 50 is configured to remove impurity gas components that remain after being removed by the first separator 30. For example, the adsorption column of the second separator 50 may be packed with an adsorbent capable of removing impurity gas components different from those removed by the second separator 50. Alternatively, the adsorption column of the second separator 50 may be packed with an adsorbent capable of removing the same components as those removed by the second separator 50. In this disclosure, by providing the second separator 50 downstream of the first separator 30, components of impurity gas that could not be completely removed by the first separator 30 are removed, making it possible to purify helium gas to a higher purity. In such a configuration, the second separator 50 can also be understood as being responsible for purifying the helium-containing gas concentrated after passing through the first separator 30.

[0041] For example, the components of the impurity gas removed in the second separator 50 may be at least one selected from the group consisting of H2, hydrocarbons, Ar, H2O, CO, CO2, O2, and N2. In particular, the components of the impurity gas removed in the second separator 50 may include at least one selected from the group consisting of O2, N2, and Ar. That is, the adsorbent packed into the adsorption column of the second separator 50 may be a known material capable of capturing at least one selected from the group consisting of O2, Ar, and N2. Examples of such adsorbents include type X and type A zeolites, activated carbon, MSC (Molecular Sieve Carbon), porous silica, porous alumina, and / or metal-organic structures.

[0042] The second separator 50 can be a PSA type device using a compressor, or a PVSA type device using a blower and a vacuum pump.

[0043] If the second separator 50 is configured to perform the final purification process in the helium recovery and purification apparatus, it is preferable that the second separator 50 is a PSA type separator. In other words, if the second gas extracted from the second separator 50 is the final purified helium gas, it is preferable that the second separator 50 is a PSA type separator.

[0044] Normally, helium gas distributed as a product gas is filled into the product tank 60 under high pressure of approximately 0.5 MPa to 0.9 MPa. If the second separator 50 is a PSA type separator, the gas introduced into the second separator 50 is pressurized by a compressor and sent to the adsorption tower, so that the non-adsorbed gas (second gas) containing helium can be extracted under high pressure. Therefore, the second gas extracted from the second separator 50 can be filled into the product tank 60 as purified helium gas without being further pressurized using a compressor or the like. In other words, the helium recovery and purification apparatus of this disclosure can realize a simpler configuration that does not necessarily require a compressor between the second separator 50 and the product tank 60. Furthermore, if a compressor is installed between the second separator 50 and the product tank 60, there is a risk that impurity gases from the outside will be mixed in due to the operation of the compressor, and the purity of the purified gas will decrease. According to this disclosure, as described above, by adopting a configuration that eliminates the need for a compressor for the purified gas, the inclusion of impurity gases in the purified gas is effectively suppressed, making it possible to purify helium gas to a higher purity.

[0045] With the apparatus configuration described above, the helium recovery and purification apparatus of this disclosure is capable of purifying high-purity helium gas by gradually increasing the helium concentration. Specifically, the first gas extracted from the first separator 30 has a higher helium concentration than the gas to be processed. Furthermore, the second gas extracted from the second separator 50 has a higher helium concentration than the first gas. The helium concentration at each stage may be measured using a commercially available concentration meter.

[0046] More specifically, the concentration of helium in the first gas is higher than the concentration of helium in the gas to be treated, for example, it may be between 1% by volume and 60% by volume.

[0047] Furthermore, the helium concentration in the second gas may be higher than that in the first gas, for example, between 80% and 99.9999% by volume. The inventors of this application have demonstrated that, for example, by processing a gas with a helium concentration of approximately 8% by volume in the second separator 50 described above, a high-purity helium gas of 99.999% by volume can be obtained as the second gas. As described above, by installing the second separator 50 downstream of the first separator 30 and gradually increasing the helium concentration, it becomes possible to purify helium gas more efficiently.

[0048] The helium recovery and purification apparatus of this disclosure may further include a pretreatment unit installed upstream of the first separator 30. For example, the gas to be treated may be passed through a fine particle separator 10 to remove dust, which is a solid impurity such as fine particles contained in the gas to be treated, before being introduced into the first separator 30 (see Figure 1). The fine particle separator 10 may include one or more filters, and by passing the gas to be treated through the filters, fine particles contained in the gas to be treated may be captured. The filters are not particularly limited, but for example, commercially available HEPA filters and / or ULPA filters may be used. Such a fine particle separator 10 may also be called a fine particle capture unit, dust collector separator, dust collector filter, etc.

[0049] Although not shown in the figures, the helium recovery and purification apparatus may be configured to perform gas separation by membrane separation between the first separator 30 and the second separator 50, and / or downstream of the second separator 50. For example, the helium recovery and purification apparatus may further include a membrane separator capable of performing gas separation by membrane separation between the first separator 30 and the second separator 50, and / or downstream of the second separator 50. The membrane separator may include a separation membrane and be configured to separate a first gas containing helium gas from an impurity gas that does not contain helium gas. Such a membrane separator may be capable of separating and removing a portion of the impurity gas by utilizing the difference in the gas permeation rate through the membrane. For example, a portion of the impurity gas may be recovered as an impermeable gas, and the gas containing helium gas may be recovered as a permeable gas. Alternatively, the gas containing helium gas may be recovered as an impermeable gas, and a portion of the impurity gas may be recovered as a permeable gas. This allows for the appropriate removal of a portion of the impurity gas from the gas to be treated, thereby increasing the helium concentration.

[0050] The separation membrane used in the membrane separator is not particularly limited, as long as it can remove a portion of the impurity gases contained in the gas to be treated, and any known separation membrane may be used. For example, the separation membrane may be a known separation membrane capable of separating and recovering at least one substance selected from the group consisting of H2O, CO, N2, O2, Ar, hydrocarbons, and CO2 from helium gas.

[0051] A membrane separator may have only a single separation membrane or may have multiple separation membranes. For example, a membrane separator may have a separation membrane unit with multiple separation membranes. By having multiple separation membranes, it may be possible to remove multiple types of impurity gas components. Alternatively, by having multiple separation membranes capable of removing a common impurity gas component, it may be possible to remove impurity gases in stages. This may increase the efficiency of impurity gas removal.

[0052] [Second Embodiment] Figures 3 and 4 are schematic diagrams illustrating the configuration of a helium recovery and purification apparatus according to the second embodiment of this disclosure, respectively. The helium recovery and purification apparatus according to the second embodiment differs from the helium recovery and purification apparatus according to the first embodiment in that it includes a cryogenic separator 40 downstream of the first separator 30. The cryogenic separator 40 is configured to cool the introduced gas to liquefy a portion of the impurity gas and separate it into a liquid phase portion containing the liquefied material and a gaseous phase portion containing the gaseous component.

[0053] For example, as shown in Figure 3, the cryogenic separator 40 may be positioned between the first separator 30 and the second separator 50. The first separator 30, the cryogenic separator 40, and the second separator 50 may be fluidly connected to each other in this order. More specifically, the first separator 30 may be fluidly connected to the cryogenic separator 40, and the cryogenic separator 40 may be fluidly connected to the second separator 50. This means that the gas to be treated can flow into the first separator 30, the cryogenic separator 40, and the second separator 50 in that order. For example, the first separator 30 and the cryogenic separator 40, and / or the cryogenic separator 40 and the second separator 50 may be fluidly connected to each other via piping or the like.

[0054] Alternatively, as shown in Figure 4, the first separator 30, the second separator 50, and the cryogenic separator 40 may be fluid-connected to each other in that order. More specifically, the first separator 30 may be fluid-connected to the second separator 50, and the cryogenic separator 40 may be fluid-connected to the second separator 50. This means that the gas to be treated can flow into the first separator 30, the second separator 50, and the cryogenic separator 40 in that order.

[0055] The cryogenic separator 40 does not necessarily have to be directly fluid-connected to the first separator 30 or the second separator 50, and other components may be placed between each processor. For example, as shown in Figures 3 and 4, tanks 35, 45, etc., capable of temporarily storing gas may be placed between the first separator 30 and the cryogenic separator 40, and / or between the cryogenic separator 40 and the second separator 50. That is, a storage tank may be installed upstream of each processor, and gas may be supplied to each processor from the storage tank. In addition, the helium-containing gas extracted from each processor may be sent to a storage tank installed downstream of each processor. By providing a storage tank, fluctuations in the flow rate of gas supplied to each processor can be suitably suppressed, and gas can be supplied to each processor more stably.

[0056] Furthermore, the piping that fluid-connects each processing unit may be equipped with valves, pumps, filters, pressure gauges, flow meters, concentration meters, and / or thermometers.

[0057] In the helium recovery and purification apparatus of this disclosure, the gas to be treated passes through a first separator 30, a cryogenic separator 40, and a second separator 50, thereby progressively removing impurity gases contained in the gas to be treated. This progressively concentrates the helium in the gas to be treated, ultimately enabling the acquisition of high-purity helium gas. For example, in the configuration shown in Figure 3, the first separator 30 adsorbs and removes some of the impurity gases contained in the gas to be treated, and a first gas with a higher helium concentration than the gas to be treated is extracted. The first gas is introduced into the cryogenic separator 40 and cooled. Cooling separates some of the impurity gases contained in the first gas into a liquid phase as liquefied substances, resulting in a gas phase portion with a higher helium concentration than the first gas. That is, in the cryogenic separator 40, the first gas is separated into a gas phase portion with concentrated helium and a liquid phase portion containing some of the impurity gases that were contained in the first gas. The gas phase portion may then be introduced into the second separator 50. In the second separator 50, at least a portion of the impurity gases remaining in the gas phase are adsorbed and removed, thereby obtaining purified gas containing high-purity helium.

[0058] Alternatively, as shown in Figure 4, the first separator 30, the second separator 50, and the cryogenic separator 40 may be fluidly connected to each other in this order. In this configuration, the first separator 30 adsorbs and removes some of the impurity gases contained in the gas to be treated, and a first gas with a higher helium concentration than the gas to be treated is extracted. The first gas is introduced into the second separator 50. The second separator 50 further adsorbs and removes some of the impurity gases contained in the first gas. As a result, a second gas with a higher helium concentration than the first gas is extracted. The second gas is then introduced into the cryogenic separator 40 and cooled. Cooling separates the impurity gases contained in the second gas into a liquid phase as liquefied substances, thereby obtaining a purified gas containing high-purity helium as the gas phase.

[0059] The helium recovery apparatus of this disclosure includes a first separator 30 and a second separator 50 that utilize adsorption, as well as a cryogenic separator 40 that can remove a portion of the impurity gas by gas-liquid separation. With this configuration, the helium contained in the gas to be treated can be efficiently concentrated by removing the impurity gas in stages in the first separator 30, the second separator 50, and the cryogenic separator 40. Gas-liquid separation by the cryogenic separator 40 separates the impurity gas as a liquefied substance, making it easy to remove a large amount of impurity gas contained in the gas to be treated. As a result, the amount of impurity gas removed by separators located upstream and / or downstream of the cryogenic separator 40 can be greatly reduced. This can, for example, reduce the processing time for adsorption removal, reduce the amount of adsorbent required for adsorption removal, and make it possible to make the size of the adsorption tower more compact. Thus, the helium recovery and purification apparatus of this disclosure can concentrate helium with high efficiency even in gases to be treated that have a low helium concentration and contain a large amount of impurity gas.

[0060] Furthermore, in the cryogenic separator 40, the introduced gas (first gas or second gas) is cooled to liquefy a portion of the impurity gas and remove it from the gas phase, thereby obtaining a gas (gas phase portion) in which helium is concentrated. Compared to separators using adsorption or cryogenic separation methods, such a cryogenic separator 40 does not require large equipment such as adsorption columns or rectification columns, and therefore may have a simpler configuration. In particular, unlike cryogenic separation methods, the cryogenic separator 40 of this disclosure does not require distillation, and therefore may have a simpler equipment configuration compared to separators using cryogenic separation methods. Accordingly, according to this disclosure, a helium recovery and purification apparatus that can efficiently recover helium with a more compact configuration can be realized.

[0061] Furthermore, the helium recovery and purification apparatus shown in Figures 3 and 4 includes separators for removing impurity gases upstream and / or downstream of the cryogenic separator 40. This allows for the effective removal of impurity gases that cannot be completely removed by the cryogenic separator 40. For example, impurity gas components that do not liquefy under the cooling conditions implemented by the cryogenic separator 40, and / or impurity gas components that remain in the gas phase without liquefaction, can be effectively removed by the first separator 30 and the second separator 50. This enables the more efficient recovery of high-purity purified helium gas.

[0062] A helium recovery and purification apparatus according to this disclosure, equipped with such a cryogenic separator 40, may be particularly effective when the gas to be processed is a mixed gas containing at least a small amount of helium and a large amount of nitrogen. The boiling point of N2 is approximately -196°C at atmospheric pressure, which is sufficiently higher than the boiling point of helium (approximately -269°C). Therefore, by providing cooling conditions in the cryogenic separator 40 that allow the N2 gas to be liquefied, it becomes possible to suitably remove the N2 gas that is mainly contained in the gas to be processed. In other words, by providing a cryogenic separator 40 in the helium recovery and purification apparatus according to this disclosure, the large amount of N2 gas contained in the gas to be processed can be removed more efficiently, and high-purity helium gas can be easily purified. Therefore, the helium recovery and purification apparatus according to this disclosure may be more useful when the gas to be processed is a helium-containing gas that contains a large amount of N2 gas.

[0063] The components of the impurity gas removed in the first separator 30 may be different from the components removed in the cryogenic separator 40. For example, the components removed in the first separator 30 may be components that do not liquefy under the cooling conditions implemented in the cryogenic separator 40. In one preferred embodiment, the components removed in the first separator 30 are components that can solidify under the cooling conditions implemented in the cryogenic separator 40. If the impurity gas solidifies in the cryogenic separator 40, it becomes necessary to remove the solidified impurity gas. By removing these components in advance in the first separator 30, which is installed upstream of the cryogenic separator 40, it becomes possible to omit the work of removing the solidified impurity components. In this configuration, the removal of impurity gas in the first separator 30 can be understood as a pretreatment for more favorably implementing gas-liquid separation in the cryogenic separator 40.

[0064] Furthermore, when the cryogenic separator 40 is positioned between the first separator 30 and the second separator 50 (see Figure 3), the first separator 30, which is positioned upstream of the cryogenic separator 40, may be a PVSA type separator. Generally, PVSA type separators can operate in a lower pressure range compared to PSA type separators. Therefore, the pressure difference between the first gas extracted from the first separator 30 and the gas in the cryogenic separator 40 can be reduced. In other words, the first gas can be introduced into the cryogenic separator 40 without significantly reducing the pressure of the first gas extracted from the first separator 30. This improves the energy efficiency of the separation operation through the first separator 30 and the cryogenic separator 40.

[0065] If the focus is on recovering higher purity helium gas, it is preferable to position the second separator 50 downstream of the cryogenic separator 40 (see Figure 3). The second separator 50, positioned upstream of the cryogenic separator 40, is preferably configured to remove components that remain after being liquefied in the cryogenic separator 40. For example, the adsorption column of the second separator 50 may be filled with an adsorbent capable of removing the same components as those liquefied and removed in the cryogenic separator 40. In the gas-liquid separation in the cryogenic separator 40, impurity gases are liquefied based on gas-liquid equilibrium, so trace amounts of impurity gases may remain in the gas phase. As shown in Figure 3, by providing a second separator 50 downstream of the cryogenic separator 40 that can remove components of impurity gases that were not liquefied in the cryogenic separator 40, it is possible to purify helium gas to a higher purity. In this configuration, the second separator 50 can also be understood as being responsible for the final purification of the helium-containing gas concentrated through the first separator 30 and the cryogenic separator 40.

[0066] The cryogenic separator 40 may include, for example, a cooling section for cooling the first gas extracted from the first separator 30 or the second gas extracted from the second separator 50, a supply line for introducing the first gas or the second gas into the cooling section, and a transfer line for extracting the gas phase portion separated into liquid and gas phase in the cooling section. The cryogenic separator 40 may also further include a discharge line for discharging the liquefied impurity gas, which is the liquid phase portion, from the cooling section.

[0067] The cryogenic separator 40 is configured to cool the first or second gas under conditions that liquefy at least a portion of the impurity gas while not liquefying the helium gas. For example, the cryogenic separator 40 is configured to cool the first or second gas to a temperature lower than the boiling point of the impurity gas but higher than the boiling point of helium. With such cooling, the helium gas remains in a gaseous state while at least a portion of the impurity gas is liquefied. As a result, the first or second gas introduced into the cryogenic separator 40 is separated into a liquid phase portion, which is the liquefied impurity gas, and a gaseous phase portion, which is the helium gas.

[0068] At least a portion of the impurity gas is removed as liquefaction, resulting in a concentration of helium in the gas phase. This yields a gas phase with a higher helium concentration than the gas introduced into the cryogenic separator 40. The gas phase may be removed via a transfer line. Thus, the cryogenic separator 40 provided in the helium recovery and purification apparatus of this disclosure is configured to cool the introduced gas and allow for the extraction of the gas phase containing helium gas. Therefore, the cryogenic separator 40 does not require equipment such as a rectification column for rectification, as in cryogenic separation methods, and can have a very simple structure.

[0069] Cooling of the gas introduced into the cryogenic separator 40 may be carried out in a cooling section. Cooling of the gas in the cooling section may be achieved by any means capable of cooling to a temperature at which a portion of the impurity gas liquefies. For example, the cooling section may include a cooling tank equipped with a cooling mechanism, and the gas introduced into the cooling tank may be cooled within the cooling tank. For example, cooling may be carried out using a commercially available cryogenic refrigerator. Although not particularly limited, various refrigerators such as mechanical refrigerators GM refrigerators, pulse tube refrigerators, GM-JT refrigerators, or Solvay refrigerators can be used as cryogenic refrigerators.

[0070] The liquid phase containing liquefied impurity gas and the gas phase containing helium gas may be separated by static cooling in a cooling tank. The impurity gas, liquefied by cooling, accumulates as the liquid phase at the bottom of the cooling tank, while the gas phase containing helium is located at the top of the cooling tank. By cooling the gas introduced into the cooling tank all at once and removing the gas phase, it becomes possible to efficiently process large quantities of gas.

[0071] Alternatively, the cooling unit may further include a gas-liquid separator to suitably separate the liquefied impurity gas from the gas phase. For example, the liquid phase and the gas phase may be separated using a centrifugal gas-liquid separator. With such a configuration, it becomes possible to more suitably separate the liquid phase and the gas phase, and to obtain a gas phase with a higher helium concentration.

[0072] The components of the impurity gas removed by the cryogenic separator 40 are components that liquefy under cooling conditions in which helium can exist as a gas. For example, the components of the impurity gas removed by the cryogenic separator 40 may be at least one selected from the group consisting of H2O, CO, Ar, O2, N2, and CO2.

[0073] The cryogenic separator 40 may be operated under cooling conditions that allow for the extraction of helium as a gas while simultaneously liquefying impurity gases. The cryogenic separator 40 may be configured to allow control of the temperature conditions of the cooling section in order to suitably extract a second gas in which helium is more concentrated.

[0074] For example, the cooling temperature of the gas in the cryogenic separator 40 may be approximately -195°C or lower. While there are no particular limitations on the lower limit of the cooling temperature, if energy efficiency in cooling is a priority, it may be, for example, -250°C or higher, -240°C or higher, or -230°C or higher. As mentioned above, when the gas to be processed contains N2 as the main component, it is more preferable that the cooling temperature be approximately -195°C or lower and approximately -210°C or higher. By using such cooling conditions, a large amount of N2 gas can be removed in the cryogenic separator 40, making it possible to obtain high-purity helium gas more efficiently.

[0075] Furthermore, the cryogenic separator 40 may liquefy a portion of the impurity gas by controlling (for example, compressing) the pressure in the cooling section. In other words, the cryogenic separator 40 may be configured to allow control of the pressure conditions in the cooling section.

[0076] The gas cooling conditions in the cryogenic separator 40 (pressure in the cooling tank, flow rate of gas introduced into the cooling tank, etc.) may be appropriately selected according to the type and concentration of impurity gas components to be removed. For example, the pressure (gauge pressure) in the cooling tank may be less than or equal to the adsorption pressure of the first separator 30 or second separator 50 located before the cryogenic separator 40. This eliminates the need to compress the gas introduced during separation in the cryogenic separator 40. Eliminating the need for gas compression makes it possible to improve the efficiency and simplify the process and equipment. Furthermore, it is possible to avoid the risk of contamination with impurity gases associated with gas compression, thus enabling the acquisition of higher concentrations of helium gas. For example, the pressure (gauge pressure) in the cooling tank may be 25 kPa or less. While there are no particular limitations on the lower limit of the pressure (gauge pressure) in the cooling tank, if the focus is on obtaining a gas containing a more preferably higher concentration of helium from a gas containing a low concentration of helium (e.g., 0.1% to 10% by volume), the flow rate of the gas to be treated may be in the range of, for example, 8 L / min to 30 L / min. In one embodiment, after the helium concentration in the gas phase portion of the cooling tank is adjusted to a predetermined value, the flow rate of gas introduced into the cooling tank and the flow rate of gas discharged from the cooling tank may be adjusted so that the helium concentration in the gas phase portion is maintained. This can control the gauge pressure in the cooling tank. For example, the inventors of this application have demonstrated that by treating a gas with a helium concentration of approximately 10% by volume in a cryogenic separator 40 at the above-mentioned flow rate, a temperature of -206°C, and a pressure of 25 kPa, a gas with a helium concentration of approximately 60% by volume can be obtained.

[0077] As shown in Figure 3, when a cryogenic separator 40 is placed between the first separator 30 and the second separator 50, the concentration of helium in the gas phase portion may be higher than the concentration of helium in the first gas, and may be between 30% by volume and 60% by volume. When the helium concentration in the gas phase portion is within the above range, the efficiency of removing impurity gases in the subsequent second separator is increased, making it possible to obtain a more suitable high-purity helium gas. Furthermore, in this configuration, the concentration of helium in the second gas extracted from the second separator 50 may be higher than the concentration of helium in the gas phase portion, and may be between 80% by volume and 99.9999% by volume.

[0078] As described above, by gradually increasing the helium concentration, it becomes possible to purify helium more efficiently and effectively. In particular, in this disclosure, the efficiency of recovery and purification is improved by removing most of the impurity gas in the cryogenic separator 40 provided between the first separator 30 and the second separator 50. Furthermore, the cryogenic separator 40 has a very simple configuration compared to equipment using cryogenic separation, enabling the miniaturization of the apparatus. In addition, by providing separators using the adsorption method upstream and downstream of the cryogenic separator 40, it is possible to achieve the purification of helium gas to a higher purity.

[0079] [Third Embodiment] Next, a helium recovery and purification apparatus according to the third embodiment will be described. Figures 5 and 6 are schematic diagrams of helium recovery and purification apparatuses 103 and 104 according to the third embodiment, respectively. As shown in the figures, the helium recovery and purification apparatus according to the third embodiment differs from the helium recovery and purification apparatus according to the first embodiment in that it includes a return line 52 that merges the off-gas discharged from the second separator 50 with the gas upstream of the second separator 50.

[0080] For example, the return line 52 may be configured to return at least a portion of the off-gas discharged from the second separator 50 to a processor located upstream. In this specification, "off-gas" means the gas separated and recovered as an impurity gas in the second separator 50. For example, "off-gas" means the gas discharged when impurity gas components captured by the adsorbent are desorbed, and may also be called desorption gas. The return line 52 may be configured to supply at least a portion of the off-gas discharged from the second processor to upstream processors such as the first separator 30, the cryogenic separator 40 (if provided), and / or the second separator 50. The off-gas supplied via the return line 52 is subjected to recovery and purification treatment again. That is, the return line 52 makes it possible to recycle the off-gas discharged from the second separator 50. This allows the helium gas, if present in trace amounts in the off-gas, to be suitably recovered by further recovery and purification treatment. Therefore, it becomes possible to further improve the recovery rate of helium contained in the gas being processed. Consequently, with this configuration, it becomes possible to recover and purify high-purity helium gas with a higher recovery rate.

[0081] For example, the return line 52 may be configured to return at least a portion of the off-gas discharged from the second separator 50 to the first separator 30 (see Figure 5). That is, at least a portion of the off-gas discharged from the second separator 50 may be configured to pass through the return line 52 and merge with the gas to be treated that is introduced into the first separator 30. For example, at least a portion of the off-gas may be introduced into a storage tank 20 provided immediately before the first separator 30 and merge with the gas to be treated in the storage tank 20. With such a configuration, at least a portion of the off-gas from the second separator 50 can be used again for adsorption removal in the first separator 30, making it possible to more effectively remove impurity gases while improving the helium recovery rate.

[0082] Furthermore, the inventors have discovered that the helium concentration of the gas to be treated can be increased by the merging of the gas to be treated and the off-gas introduced into the first separator 30. This makes it possible to purify helium gas to a higher purity after passing through the first separator 30 and the second separator 50. This effect is more pronounced when the helium concentration of the gas to be treated is low (for example, 0.1 vol% to 10 vol%). In other words, with the above configuration that returns the off-gas, it is possible to suitably purify helium gas to a higher purity from a gas to be treated that contains a low concentration of helium.

[0083] Furthermore, the return line 52 may be configured to return at least a portion of the off-gas discharged from the second separator 50 to the second separator 50 (see Figure 6). At least a portion of the off-gas discharged from the second separator 50 may be configured to pass through the return line 52 and merge with the gas introduced into the second separator 50. For example, at least a portion of the off-gas from the second separator 50 may be introduced into a storage tank 45 located immediately before the second separator 50, and merge in the storage tank 45 with the gas transferred from a processor upstream of the second separator 50. With this configuration, at least a portion of the off-gas from the second separator 50 can be subjected to the adsorption removal treatment in the second separator 50 again. This makes it possible to improve the helium recovery rate while more effectively removing impurity gases.

[0084] Furthermore, when the off-gas is recirculated in the second separator 50, the off-gas is reprocessed in the second separator 50 without going through processing in the first separator 30 and the cryogenic separator 40. This suppresses the release of helium remaining in the off-gas along with the off-gas discharged in the first separator 30 and / or the liquefied material discharged in the cryogenic separator 40. In other words, it may be possible to suppress the outflow of helium contained in the off-gas and improve the helium recovery rate.

[0085] The off-gas recycled via the return line 52 does not have to be the entire amount of off-gas discharged from the second separator 50. For example, 1 volume percent or more of the total amount of off-gas discharged from the second separator 50 may be recycled via the return line 52. The more off-gas recycled, the higher the recovery rate of helium gas may be. If the focus is on improving the recovery rate, the proportion of off-gas recycled from the total amount of off-gas discharged from the second separator 50 may be, for example, 10 volume percent or more, 30 volume percent or more, or 50 volume percent or more.

[0086] According to the apparatus of this disclosure, at least 60% of the helium contained in the gas to be treated can be recovered. In other words, in the apparatus of this disclosure, the helium recovery rate from the gas to be treated can be 60% or more.

[0087] Furthermore, the inventors have found that if the amount of off-gas recycled is excessively large, the purity of the ultimately obtained purified gas may decrease, while the introduction of a small amount of off-gas can contribute to increasing the purity of the purified gas. If the priority is to obtain a highly purified gas, the proportion of off-gas recycled from the total amount of off-gas from the second separator 50 may be, for example, 50% or less, 30% or less, or 20% or less. If the priority is on both the recovery rate and the purity of the purified gas, the proportion of off-gas recycled from the total amount of off-gas from the second separator 50 may be, for example, 1% to 50% or 1% to 30%. This makes it possible to purify helium gas with a high recovery rate and high purity.

[0088] [Other embodiments] Furthermore, for example, the first separator 30 may be provided with a return line that returns the off-gas discharged from the first separator 30 back to the first separator 30. The off-gas discharged when desorbing impurity gases captured in the first separator 30 may pass through the return line and merge with the gas to be treated before being subjected to processing in the first separator 30. For example, a return line may be provided that fluidly connects the first separator 30 and the storage tank 20 so that the off-gas discharged from the first separator 30 is returned to the storage tank 20 installed in front of the first separator 30. The off-gas merges with the gas to be treated in the storage tank 20 and is reprocessed in the first separator 30 together with the gas to be treated. This makes it possible to suitably recover helium mixed in trace amounts in the off-gas, thereby further improving the helium recovery rate from the gas to be treated.

[0089] Next, the helium recovery and purification method of this disclosure will be described.

[0090] <Helium recovery and purification method> [First Embodiment] The helium recovery and purification method of this disclosure recovers and purifies helium from a gas to be treated that contains helium and impurity gases. According to the method of this disclosure, a high-concentration helium-purified gas can be efficiently obtained from a low-concentration helium-containing gas through a multi-stage separation process.

[0091] Figure 7 is a schematic flow chart illustrating the helium recovery and purification method of this disclosure. The method mainly includes a first separation step 3, which adsorbs and removes a portion of the impurity gases contained in the gas to be treated to obtain a first gas with a higher helium concentration than the gas to be treated, and a second separation step 5, which adsorbs and removes at least a portion of the impurity gases contained in the first gas to obtain a second gas with a higher helium concentration than the first gas. According to the method of this disclosure, by removing impurity gases from the gas to be treated through a multi-stage separation process including the first separation step 3 and the second separation step 5, and by gradually concentrating helium, high-purity helium gas can be efficiently obtained in the end.

[0092] The process described above will be explained below.

[0093] (1st separation step) In the first separation step 3, a portion of the impurity gas is removed from the gas to be treated. The removal of the impurity gas may be carried out, for example, using the pressure swing adsorption method (PSA method). This extracts a first gas with a higher helium concentration than the gas to be treated. The separation step using the PSA method includes an adsorption step in which the impurity gas is captured by an adsorbent, and a desorption step in which the captured impurity gas is desorbed.

[0094] In the adsorption step, the gas to be treated is introduced into an adsorption tower filled with an adsorbent. For example, impurity gases in the gas to be treated may be captured by the adsorbent under pressurized conditions within the adsorption tower. The non-adsorbed gas containing helium is removed as the first gas. By removing some of the impurities from the gas to be treated by the adsorbent, a first gas with concentrated helium can be obtained.

[0095] In the desorption step, the pressure inside the adsorption tower is reduced, causing impurity gas components captured by the adsorbent to desorb and be discharged as off-gas. This regenerates the adsorbent. Subsequently, the pressure inside the adsorption tower is increased again, and the adsorption step is performed again. This pressure increase inside the adsorption tower may be achieved, for example, by introducing the gas to be treated into the adsorption tower.

[0096] In one preferred embodiment, the adsorption step and the desorption step described above may be performed alternately in multiple adsorption towers with staggered periods. That is, while the adsorption step is being performed in one of the multiple adsorption towers, the desorption step may be performed in another adsorption tower. This allows the gas to be treated to be processed continuously, and the first gas can be stably supplied to the next process.

[0097] Furthermore, the method may include a purging step after the adsorption step, in addition to the desorption step, using a portion of the first gas obtained as a non-adsorbed gas. In the purging step, by introducing a portion of the first gas into the adsorption tower, residual impurity gases in the adsorption tower are removed, and the adsorbent can be more effectively regenerated. As a result, the adsorption capacity of the adsorbent for impurity gases can be more effectively utilized in the subsequent adsorption step.

[0098] In the first separation step 3, impurity gases that are difficult to remove in the downstream processing step, the second separation step 5, may be removed. That is, the components of the impurity gas removed in the first separation step may be different from the components removed in the subsequent separation step. Alternatively, the components of the impurity gas removed in the first separation step may be the same as the components removed in the subsequent separation step.

[0099] (Second separation step) In the second separation step 5, similar to the first separation step 3, at least a portion of the impurity gas contained in the gas introduced from the upstream processing step (e.g., the first separation step) may be removed using a pressure swing adsorption method. This extracts a second gas with a higher helium concentration than the introduced gas. The second separation step 5 using the pressure swing adsorption method includes, similar to the first separation step 3, an adsorption step in which the impurity gas is captured by an adsorbent, and a desorption step in which the captured impurity gas is desorbed.

[0100] The impurity gas components removed in the second separation step 5 may be the same as those removed in the first separation step 3, or they may be different from those removed in the first separation step 3. The second separation step 5 may be carried out in the same manner as the first separation step 3, except that the impurity components removed may be different. That is, the second separation step 5 may be carried out in the same steps as the first separation step 3, except that the type of adsorbent, which is appropriately selected depending on the type of component to be adsorbed and removed, and the conditions such as temperature, pressure, and cycle time in the adsorption step may differ.

[0101] For example, in the second separation step 5, it is preferable that any components remaining in the introduced gas are removed. In other words, in the second separation step 5, it is preferable that any impurity gas components remaining that were not removed in the upstream separation step are removed. For example, in the second separation step 5, the type of adsorbent and various conditions such as temperature, pressure, and cycle time in the adsorption step may be set to remove any impurity gas components remaining in the introduced gas. In the method of this disclosure, by performing the second separation step 5 using the adsorption method as a subsequent step, it is possible to suitably remove at least a portion of the impurity gas components that were not completely removed in the upstream separation steps, including the first separation step 3 and / or the low-temperature separation step 4 described later. This makes it possible to efficiently purify high-purity helium gas.

[0102] [Second Embodiment] Figures 8 and 9 are schematic flow diagrams illustrating a helium recovery and purification method according to a second embodiment of the present disclosure. As shown in the figures, the method may further include a low-temperature separation step 4 in which the introduced gas is cooled to separate it into a gas phase portion having a higher helium concentration than the introduced gas and a liquid phase portion containing liquefied impurity gases. According to this method, high-purity helium gas can ultimately be obtained by removing impurity gases from the gas to be treated through a multi-stage separation process including a first separation step 3, a second separation step 5, and a low-temperature separation step 4, and by gradually concentrating helium.

[0103] The low-temperature separation step 4 may be performed either before or after the second separation step 5. For example, as shown in Figure 8, the first separation step 3, the low-temperature separation step 4, and the second separation step 5 may be performed in this order. In other words, the low-temperature separation step 4 may be performed between the first separation step 3 and the second separation step 5. In this method, the low-temperature separation step 4 may be performed by cooling the first gas from the first separation step 3 to obtain a gas phase portion having a higher helium gas concentration than the first gas. Furthermore, in the second separation step 5, impurity gases may be removed from the gas phase portion obtained in the low-temperature separation step 4 to obtain a second gas having a higher helium concentration than the gas phase portion.

[0104] Alternatively, as shown in Figure 9, the first separation step 3, the second separation step 5, and the low-temperature separation step 4 may be carried out in this order. In this method, in the low-temperature separation step 4, the second gas from the second separation step 5 may be cooled to extract a gas phase portion having a higher helium gas concentration than the second gas.

[0105] In the low-temperature separation step 4, the gas obtained in the step prior to low-temperature separation step 4 is cooled, thereby liquefying some of the impurity gases contained in the gas. This cooling may be carried out based on the difference in boiling points between the impurity gases and helium. That is, by cooling the gas to a temperature range that is below the boiling point of the impurity gas components and above the boiling point of helium, the impurity gases condense and undergo a phase change from gas to liquid. As a result, the cooled gas is phase-separated into a liquid phase portion, which is the liquefied impurity, and a gas phase portion, which is the helium-concentrated portion after the liquefied impurity gases have been removed. After phase separation, the gas phase portion may be taken out and supplied to the next step.

[0106] In this cooling process, helium is concentrated by a simple operation in which the gas to be processed is cooled to condense and remove impurity gas components, and the gas phase portion is extracted. This process allows for the efficient reduction of a large amount of impurity gas from a gas containing a low concentration of helium. Furthermore, by performing separation processes using adsorption methods before and after the low-temperature separation process 4, impurity gas components that were not removed in the low-temperature separation process 4 can be suitably removed, and a higher purity helium gas can be obtained.

[0107] The multi-stage method of this disclosure may be particularly useful in the recovery and purification of helium from a gas to be treated that contains a large amount of impurity gas and a low concentration of helium. For example, the method of this disclosure may be particularly useful in the treatment of exhaust gas containing a large amount of nitrogen gas and a small amount of helium, which is discharged in the semiconductor manufacturing process. When such exhaust gas is used as the gas to be treated, conventional methods using adsorption and / or cryogenic separation methods consume a large amount of energy to remove the large amount of nitrogen gas and may require large-scale equipment such as adsorption towers and / or rectification towers. On the other hand, the method of this disclosure uses a low-temperature separation step 4, which allows for the easy removal of a large amount of nitrogen gas through a simple operation of cooling the gas to be treated and extracting the gas phase portion. Therefore, helium recovery and purification can be achieved with a more efficient and simpler equipment configuration. In particular, as shown in Figure 8, in a method in which a separation step using adsorption is performed after the low-temperature separation step, components that cannot be completely removed in the low-temperature separation step 4 can be removed in the second separation step 5, making it possible to purify helium gas to a higher purity.

[0108] [Third Embodiment] Next, a helium recovery and purification method according to the third embodiment will be described. Figures 10 and 11 are schematic flow diagrams illustrating the helium recovery and purification method according to the third embodiment of this disclosure. The helium recovery and purification method according to the third embodiment differs from the helium recovery and purification method according to the first embodiment in that it includes returning at least a portion of the off-gas discharged in the second separation step 5 to a processing step upstream of the second separation step 5.

[0109] The off-gas discharged in the desorption step of the second separation process 5 is mostly impurity gas, but may also contain trace amounts of helium. By returning this off-gas to the processing process upstream of the second separation process 5, it is possible to recover even more helium from the off-gas containing trace amounts of helium. This makes it possible to further improve the helium recovery rate from the gas being processed.

[0110] At least a portion of the off-gas discharged in the second separation step 5 may be merged with the upstream gas. For example, the off-gas discharged in the second processing step 5 may be returned to the first separation step 3, the low-temperature separation step 4 (if included), and / or the second separation step 5. The off-gas from the second separation step 5 is subjected to recovery and purification treatment again in the first separation step 3, the low-temperature separation step 4 (if included), and / or the second separation step 5. This allows trace amounts of helium contained in the off-gas to be suitably recovered through the recovery and purification treatment again. Therefore, it is possible to further improve the recovery rate of helium contained in the gas being treated. With this configuration, high-purity helium gas can be recovered and purified with a higher recovery rate.

[0111] For example, at least a portion of the off-gas discharged in the second separation step 5 may be returned to the first separation step 3 (see Figure 10). That is, at least a portion of the off-gas discharged in the second separation step 5 may be combined with the gas to be treated in the first separation step 3. In the first separation step 3, a mixed gas of the gas to be treated and the off-gas discharged from the second separation step 5 may be processed. This allows the off-gas from the second separation step 5 to be used again for the impurity gas removal treatment in the first separation step 3, thereby improving the helium gas recovery rate. Furthermore, if the helium gas concentration in the gas to be treated is low, the helium gas concentration of the gas introduced into the first separation step 3 can be increased by combining it with the off-gas. This makes it possible to further improve the purity of the purified gas finally obtained.

[0112] Alternatively or additionally, at least a portion of the off-gas discharged in the second separation step 5 may be returned to the second separation step (see Figure 11). That is, at least a portion of the off-gas discharged in the second separation step 5 may be combined with the gas introduced into the second separation step 5. In the second separation step 5, a mixed gas of the gas transferred from the upstream side of the second separation step 5 and the off-gas discharged from the second separation step 5 may be processed. With this configuration, the off-gas from the second separation step 5 can be used again for adsorption removal in the second separator 50. This makes it possible to improve the recovery rate of helium gas.

[0113] The embodiments of this disclosure have been described above, but these are merely typical examples. Those skilled in the art will readily understand that this disclosure is not limited thereto, and various embodiments are conceivable without altering the essence of this disclosure.

[0114] Furthermore, the above-described embodiment of the present disclosure includes the following preferred embodiments. <1> A helium recovery and purification apparatus for recovering and purifying helium gas from a gas to be processed that contains helium gas and impurity gases, A first separator that adsorbs and removes a portion of the impurity gas contained in the gas to be processed and extracts the first gas containing the helium gas, A helium recovery and purification apparatus comprising a second separator located downstream of the first separator, which adsorbs and removes at least a portion of the impurity gas and extracts a second gas containing the helium gas. <2> The concentration of helium in the gas to be treated is 0.1% by volume or more and 50% by volume or less. <1> The helium recovery and purification apparatus described above. <3> The first separator and the second separator are separators that operate by the pressure swing adsorption method, Each of the first separator and the second separator comprises three or more adsorption towers. <1> or <2> The helium recovery and purification apparatus described above. <4> The second separator includes a return line for recovering at least a portion of the off-gas obtained by desorbing the adsorbed impurity gases. The return line is configured to merge at least a portion of the off-gas with the gas upstream of the second separator. <1> ~ <3> A helium recovery and purification apparatus as described in any one of the following. <5> The return line is arranged to introduce at least a portion of the off-gas into the first separator. <4> The helium recovery and purification apparatus described above. <6> The return line is arranged to introduce at least a portion of the off-gas into the second separator. <4> or <5> The helium recovery and purification apparatus described above. <7> The first separator is further provided with a cryogenic separator located downstream of the first separator, which separates the gas phase containing helium gas from the liquid phase containing impurity gas by cooling. <1> ~ <6> A helium recovery and purification apparatus as described in any one of the following. <8> The low-temperature separator is configured to cool the first gas from the first separator, The second separator is configured to adsorb and remove at least a portion of the impurity gas contained in the gas phase portion from the low-temperature separator. <7> The helium recovery and purification apparatus described above. <9> The second separator is configured to adsorb and remove at least a portion of the impurity gas contained in the first gas from the first separator. The cryogenic separator is configured to cool the second gas from the second separator. <7> or <8> The helium recovery and purification apparatus described above. <10> The main component of the gas to be treated is N2. <1> ~ <9> A helium recovery and purification apparatus as described in any one of the following. <11> The concentration of N2 contained in the gas to be treated is 50% by volume or more and 99.9% by volume or less. <1> ~ <10> A helium recovery and purification apparatus as described in any one of the following. <12> Of the impurity gases, the components adsorbed and removed by the first separator and the components adsorbed and removed by the second separator are different from each other. <1> ~ <11> A helium recovery and purification apparatus as described in any one of the following. <13> Of the impurity gases, the component adsorbed and removed by the first separator is at least one selected from the group consisting of H2, hydrocarbons, Ar, H2O, CO, N2, O2, and CO2. <1> ~ <12> A helium recovery and purification apparatus as described in any one of the following. <14> Of the impurity gases, the component removed by the cryogenic separator is at least one selected from the group consisting of Ar, CO, O2, N2, and CO2. <7> ~ <9> A helium recovery and purification apparatus as described in any one of the following. <15> The main component of the aforementioned impurity gas is N2, Of the aforementioned impurity gases, the component removed by the cryogenic separator is mainly N2. <7> ~ <9> A helium recovery and purification apparatus as described in any one of the following. <16> Of the impurity gases, the component that is adsorbed and removed by the second separator is at least one selected from the group consisting of H2, hydrocarbons, Ar, H2O, CO, CO2, O2, and N2. <1> ~ <11> One of the following helium recovery and purification systems. <17> The concentration of helium in the first gas discharged from the first separator is higher than the concentration of helium in the gas to be treated. The concentration of helium in the first gas is between 1% by volume and 60% by volume. <1> ~ <16> A helium recovery and purification apparatus as described in any of the following. <18> The concentration of helium contained in the gas phase portion from the cryogenic separator is higher than the concentration of helium contained in the first gas. The concentration of helium in the gas phase portion is between 30% by volume and 60% by volume. <7> ~ <9> One of the following helium recovery and purification systems. <19> The concentration of helium in the second gas supplied from the second separator is higher than the concentration of helium in the gas introduced into the second separator. The concentration of helium in the second gas is between 80% by volume and 99.9999% by volume. <1> ~ <14> One of the following helium recovery and purification systems. <20> A helium recovery and purification method for recovering and purifying helium gas from a gas to be treated that contains helium gas and impurity gases, A first separation step involves adsorbing and removing a portion of the impurity gas contained in the gas to be processed, and extracting the first gas. A helium recovery and purification method comprising: a second separation step of adsorbing and removing at least a portion of the impurity gas contained in the first gas to obtain a second gas containing the helium gas. <21> The second separation step includes desorbing the adsorbed impurity gas, The further step includes combining at least a portion of the off-gas containing the desorbed impurity gas with the gas upstream of the second separation step. <20> A method for recovering and purifying helium. <22> The further step includes returning at least a portion of the off-gas to the first separation step. <21> The helium recovery and purification method described below. <23> The further step includes returning at least a portion of the off-gas to the second separation step. <21> or <22> The helium recovery and purification method described below. <24> Between the first separation step and the second separation step, the first gas is further cooled to separate it into a gas phase portion containing helium and a liquid phase portion containing the liquefied impurity gas, The impurity gas that is adsorbed and removed in the second separation step is the impurity gas contained in the gas phase portion. <21> ~ <23> A helium recovery and purification method described in any one of the following. <25> The following steps include a low-temperature separation step in which the second gas is cooled to separate it into a gas phase portion containing helium and a liquid phase portion containing the liquefied impurity gas. <21> ~ <23> A helium recovery and purification method described in any one of the following. [Industrial applicability]

[0115] The helium recovery and purification apparatus and helium recovery and purification method of this disclosure can be used in facilities in fields where helium recovery and purification are anticipated, such as semiconductor manufacturing plants and other facilities where a mixed gas containing helium is discharged as exhaust gas. [Explanation of Symbols]

[0116] 100-104 Helium recovery and purification system 10 Fine powder remover 20 Storage tanks 30 1st separator 35 Storage Tanks 40 Cryogenic separator 45 Storage tanks 50 Second separator 52 Return Line 60 product tanks

Claims

1. A helium recovery and purification apparatus for recovering and purifying helium gas from a gas to be processed that contains helium gas and impurity gases, A first separator that adsorbs and removes a portion of the impurity gas contained in the gas to be processed and extracts the first gas containing the helium gas, A helium recovery and purification apparatus comprising a second separator located downstream of the first separator, which adsorbs and removes at least a portion of the impurity gas and extracts a second gas containing the helium gas.

2. The helium recovery and purification apparatus according to claim 1, wherein the concentration of helium contained in the gas to be processed is 0.1 volume% or more and 50 volume% or less.

3. The first separator and the second separator are separators that operate by a pressure swing adsorption method, The helium recovery and purification apparatus according to claim 1, wherein each of the first separator and the second separator comprises three or more adsorption towers.

4. The second separator includes a return line for recovering at least a portion of the off-gas obtained by desorbing the adsorbed impurity gases. The helium recovery and purification apparatus according to claim 1, wherein the return line is configured to merge at least a portion of the off-gas with the gas upstream of the second separator.

5. The helium recovery and purification apparatus according to claim 4, wherein the return line is arranged to introduce at least a portion of the off-gas into the first separator.

6. The helium recovery and purification apparatus according to claim 4, wherein the return line is arranged to introduce at least a portion of the off-gas into the second separator.

7. The helium recovery and purification apparatus according to claim 1, further comprising a cryogenic separator disposed downstream of the first separator, which separates the helium gas-containing gas phase portion and the impurity gas-containing liquid phase portion by cooling.

8. The low-temperature separator is configured to cool the first gas from the first separator, The helium recovery and purification apparatus according to claim 7, wherein the second separator is configured to adsorb and remove at least a portion of the impurity gas contained in the gas phase portion from the low-temperature separator.

9. The second separator is configured to adsorb and remove at least a portion of the impurity gas contained in the first gas from the first separator. The helium recovery and purification apparatus according to claim 7, wherein the cryogenic separator is configured to cool the second gas from the second separator.

10. The main component of the gas to be treated is N ２ The helium recovery and purification apparatus according to claim 1.

11. N contained in the gas to be treated ２ The helium recovery and purification apparatus according to claim 1, wherein the concentration of is 50% by volume or more and 99.9% by volume or less.

12. The helium recovery and purification apparatus according to claim 1, wherein the components of the impurity gas that are adsorbed and removed by the first separator and the components that are adsorbed and removed by the second separator are different from each other.

13. Of the impurity gases, the component that is adsorbed and removed by the first separator is H ２ , hydrocarbons, Ar, H ２ O, CO, N ２ , O ２ and CO ２ The helium recovery and purification apparatus according to claim 1, wherein it is at least one selected from the group consisting of the following.

14. Among the impurity gases, the components removed by the low-temperature separator are Ar, CO, O ２ , N ２ and CO ２ The helium recovery and purification device according to claim 7, which is at least one selected from the group consisting of

15. The main component of the aforementioned impurity gas is N ２ And, Of the impurity gases mentioned above, the components removed by the cryogenic separator are mainly N ２ The helium recovery and purification apparatus according to claim 7.

16. Of the impurity gases, the component that is adsorbed and removed by the second separator is H ２ , hydrocarbons, Ar, H ２ O, CO ２ , O ２ and N ２ The helium recovery and purification apparatus according to claim 1, wherein it is at least one selected from the group consisting of the following.

17. The concentration of helium in the first gas discharged from the first separator is higher than the concentration of helium in the gas to be treated. The helium recovery and purification apparatus according to claim 1, wherein the concentration of helium contained in the first gas is 1% by volume or more and 60% by volume or less.

18. The concentration of helium contained in the gas phase portion from the cryogenic separator is higher than the concentration of helium contained in the first gas. The helium recovery and purification apparatus according to claim 8, wherein the concentration of helium contained in the gas phase portion is 30% by volume or more and 60% by volume or less.

19. The concentration of helium in the second gas supplied from the second separator is higher than the concentration of helium in the gas introduced into the second separator. The helium recovery and purification apparatus according to claim 1, wherein the concentration of helium contained in the second gas is 80% by volume or more and 99.9999% by volume or less.

20. A helium recovery and purification method for recovering and purifying helium gas from a gas to be treated that contains helium gas and impurity gases, A first separation step involves adsorbing and removing a portion of the impurity gas contained in the gas to be processed, and extracting the first gas. A helium recovery and purification method comprising: a second separation step of adsorbing and removing at least a portion of the impurity gas contained in the first gas to obtain a second gas containing the helium gas.

21. The second separation step includes desorbing the adsorbed impurity gas, The helium recovery and purification method according to claim 20, further comprising combining at least a portion of the off-gas containing the desorbed impurity gas with the gas upstream of the second separation step.

22. The helium recovery and purification method according to claim 21, further comprising returning at least a portion of the off-gas to the first separation step.

23. The helium recovery and purification method according to claim 21, further comprising returning at least a portion of the off-gas to the second separation step.

24. Between the first separation step and the second separation step, the first gas is further cooled to separate it into a gas phase portion containing helium and a liquid phase portion containing the liquefied impurity gas, and a low-temperature separation step is included. The helium recovery and purification method according to claim 21, wherein the impurity gas adsorbed and removed in the second separation step is the impurity gas contained in the gas phase portion.

25. The helium recovery and purification method according to claim 21, further comprising a low-temperature separation step after the second separation step, in which the second gas is cooled to separate it into a gas phase portion containing helium and a liquid phase portion containing the liquefied impurity gas.

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