Mixed gas, method for producing same, and method for regenerating adsorbent

Abstract

The present invention addresses the problem of providing a mixed gas and a method for regenerating an adsorbent with which it is possible to suppress the pulverization of an adsorbent while removing adsorbed components from the adsorbent. The means for solving the above problem is a mixed gas containing 0.1-3.0 vol% water vapor and 97 vol% or more of a gas A different from the water vapor, wherein the gas A has a Henry's constant with respect to water at 0°C of 2000 atm / mole fraction or less.

Description

Mixed gas, method for producing the same, and method for regenerating adsorbent

[0001] The present invention relates to a mixed gas, a method for producing the same, and a method for regenerating an adsorbent.

[0002] Gas separation technology is used in various fields such as energy, environment, chemical industry, and food industry, and the appropriate separation technology is selected according to the type of gas and purpose. One such method, pressure swing adsorption (PSA), is well known as a method in which easily adsorbed gas components from a gas mixture containing two or more components are selectively adsorbed onto an adsorbent, and then desorbed by reducing the pressure to separate the gas.

[0003] Patent Document 1 describes a gas separation method for separating carbon dioxide and a gaseous substance A from a mixed gas containing carbon dioxide using an adsorption tower filled with an adsorbent, the method comprising: an adsorption step of introducing the mixed gas into the adsorption tower, adsorbing carbon dioxide onto the adsorbent, and removing the gaseous substance A; and a desorption step of removing carbon dioxide from the adsorbent by evacuating the carbon dioxide from the adsorption tower under reduced pressure, wherein the water content of the separated carbon dioxide is 2500 ppm by volume or less.

[0004] Japanese Patent Publication No. 2024-018452

[0005] Conventionally, as shown in Patent Document 1, specific components have been separated from raw material gases using adsorbents. However, when the adsorbed components on the adsorbent reach its adsorption capacity, the adsorbent is regenerated by desorbing the adsorbent, and the separation process of the raw material gas is repeatedly performed using the regenerated adsorbent.

[0006] Therefore, one method for regenerating adsorbents is to supply a mixed gas with a low content of adsorbent components, thereby lowering the partial pressure of the adsorbent components and desorbing them from the adsorbent. However, it has become clear that this method has the problem of causing the adsorbent to turn into powder.

[0007] Therefore, the present invention aims to provide a mixed gas and a method for regenerating an adsorbent that can remove adsorbed components from the adsorbent while suppressing the powdering of the adsorbent.

[0008] As a result of diligent research, the inventors of this invention have found that the above-mentioned problems can be solved by using a gas in which Henry's constant for water is below a predetermined value, and a mixed gas containing a certain amount of water vapor.

[0009] The present invention encompasses the following embodiments: <1> A mixed gas comprising 0.1% to 3.0% by volume of water vapor and 97% or more by volume of a gas A different from water vapor, wherein the gas A has a Henry constant for water at 0°C of 2000 atm / mol fraction or less. <2> The mixed gas according to <1>, wherein the gas A is carbon dioxide. <3> The mixed gas according to <1>, wherein the mixed gas further comprises at least one selected from methane, ethane, nitrogen, carbon monoxide, hydrogen, argon, and dimethyl ether. <4> The mixed gas according to <1>, wherein the concentration of gas B (excluding water vapor) having a Henry constant for water at 0°C greater than 2000 atm / mol fraction is 0% to 2.0% by volume. <5> A method for regenerating an adsorbent, comprising passing a mixed gas described in any of <1> to <4> above through a container filled with an adsorbent containing at least one selected from silica, activated carbon, alumina, and zeolite, to desorb components adsorbed on the adsorbent from the adsorbent. <6> The method for regenerating an adsorbent according to <5> above, wherein the adsorbent has the ability to adsorb carbon dioxide. <7> The method for regenerating an adsorbent according to <5> above, wherein the adsorbed component is water. <8> A method for producing a mixed gas containing 0.1 volume% to 3.0 volume% of water vapor and 97 volume% or more of gas A, which is a gas other than water vapor and has a Henry constant for water at 0°C of 2000 atm / mol fraction or less, comprising: an adsorption step in which a raw material gas containing water vapor, the gas A, and gas B (excluding water vapor) having a Henry constant for water at 0°C greater than 2000 atm / mol fraction is supplied to an adsorption tower having a desiccant and an adsorbent, and the water vapor is adsorbed by the desiccant and the gas A is adsorbed by the adsorbent to separate the gas B from the raw material gas; and a desorption step in which the inside of the adsorption tower is depressurized, wherein in the adsorption step the raw material gas is brought into contact with the desiccant and the adsorbent in that order inside the adsorption tower, and in the desorption step the inside of the adsorption tower is depressurized from the inlet side of the raw material gas to discharge the mixed gas outside the adsorption tower in a countercurrent direction with respect to the flow direction of the raw material gas in the adsorption step.

[0010] According to the present invention, it is possible to provide a mixed gas and a method for regenerating an adsorbent that can remove adsorbed components from the adsorbent while suppressing the powdering of the adsorbent.

[0011] Figure 1 is a schematic diagram of the apparatus for processing the raw material gas used in the embodiment. Figure 2 is a schematic diagram of the apparatus for regenerating the adsorbent used in the embodiment. Figure 3 is a schematic flow diagram of the gas separation method according to this embodiment. Figure 4 is a block diagram of the gas separation apparatus used in the gas separation method according to this embodiment. Figure 5 is a schematic flow diagram of the gas separation method according to this embodiment. Figure 6 is a schematic diagram of the apparatus for regenerating the adsorbent with the mixed gas produced using the gas separation method according to this embodiment. Figure 7 is a schematic diagram of the system 1000 in which biogas is applied as the raw material gas for the mixed gas production apparatus 100.

[0012] The following describes in detail embodiments for carrying out the present invention (hereinafter referred to as "this embodiment"). The present invention is not limited to the following description and can be implemented in various modifications within the scope of its gist.

[0013] [Mixed Gas] This embodiment provides a mixed gas comprising 0.1% to 3.0% by volume of water vapor and 97% or more by volume of a gas A different from water vapor, wherein the Henry constant of gas A for water at 0°C is 2000 atm / mol fraction or less. With the above configuration, it is possible to provide a mixed gas and a method for regenerating an adsorbent that can remove adsorbed components from the adsorbent while suppressing the powdering of the adsorbent.

[0014] The mixed gas according to this embodiment contains 0.1% to 3.0% by volume of water vapor. The mixed gas according to this embodiment is used to remove adsorbed components by contacting an adsorbent, but even if a certain amount of water vapor is contained in the mixed gas, the desorption of adsorbed components from the adsorbent will proceed, and the adsorbent will be regenerated. By including a predetermined amount or more of water vapor in the mixed gas, the intermolecular bonds inside the adsorbent can be reinforced, reducing internal friction and suppressing powdering. On the other hand, by keeping the amount of water vapor in the mixed gas below a predetermined amount, the adhesive strength inside the adsorbent can be appropriately maintained and powdering can be suppressed.

[0015] From the viewpoint of suppressing pulverization, the water vapor content in the mixed gas is preferably 0.2% to 2.5% by volume, more preferably 0.3% to 2.0% by volume, even more preferably 0.4% to 1.5% by volume, even more preferably 0.5% to 1.5% by volume, even more preferably 0.6% to 1.4% by volume, and even more preferably 0.7% to 1.2% by volume.

[0016] The water vapor content is measured using a dew point meter. The Vaisala DM70 Handy Type Dew Point Meter can be used as the dew point meter. The water vapor content is calculated by determining the water content (mol) from the dew point meter's measurement results, then calculating the molar concentration from the total molar amounts of the other components constituting the mixed gas, and finally determining the water vapor content (volume %) from this molar concentration. The water vapor content can be adjusted as appropriate, for example, by bubbling in a water tank.

[0017] Gas A is a gas different from water vapor. By selecting and using a gas A whose Henry constant for water at 0°C is 2000 atm / mol fraction or less, it is possible to remove adsorbed components from the adsorbent while suppressing the pulverization of the adsorbent. When a regeneration gas is supplied to an adsorbent that has adsorbed components to remove the adsorbed components, most of the water vapor is adsorbed by the adsorbent located on the supply side of the regeneration gas, making it difficult to suppress pulverization in the adsorbent located downstream. The smaller the Henry constant for water, the higher the affinity for water. By using an adsorbent with a Henry constant for water below a predetermined value during regeneration, the water vapor contained in the mixed gas is slowly released, and the pulverization of the downstream adsorbent can be suppressed as described above.

[0018] Henry's constant is the constant in Henry's Law, expressed by the following equation (1): P = Ex (1) (where x is the mole fraction of the solute gas in the liquid phase, p is the partial pressure (atm) of the solute gas in the gas phase in equilibrium with the liquid, and E is Henry's constant.)

[0019] Examples of gas A include carbon dioxide (728) (the number in parentheses is Henry's constant (atm / mole fraction)).

[0020] The gas A content is 97% by volume or more, preferably 98% by volume or more, in the mixed gas. The gas A content is measured using a gas A concentration meter. If gas A is carbon dioxide, it is measured using an infrared gas analyzer. As the infrared gas analyzer, Fuji Electric Co., Ltd., product name "ZPA", can be used. The gas A content is calculated by determining the gas A content (mol) from the measurement results of the infrared gas analyzer, calculating the molar concentration from the total molar amounts of the other components constituting the mixed gas, and taking this molar concentration as the gas A content (volume %).

[0021] The mixed gas according to this embodiment preferably further contains at least one selected from methane, ethane, nitrogen, carbon monoxide, hydrogen, argon, and dimethyl ether. Including these gases can further suppress the powdering of the adsorbent.

[0022] It is preferable that the concentration of gas B (excluding water vapor), whose Henry constant for water at 0°C is greater than 2000 atm / mol fraction, is between 0% by volume and 2.0% by volume. Having the concentration of gas B within this range further suppresses the powdering of the adsorbent.

[0023] Examples of gas B include helium (129,000), hydrogen (57,900), nitrogen (52,900), carbon monoxide (35,200), oxygen (25,500), methane (22,400), nitric oxide (16,900), ethane (12,600), ethylene (5,520), and argon (23,339) (the values ​​in parentheses are Henry's constants (atm / mole fraction)).

[0024] The content of gas B in the mixed gas is preferably 0% to 1.8% by volume, and more preferably 0% to 1.5% by volume. The content of gas B is measured using a gas B concentration meter. If gas B is methane, it is measured using an infrared gas analyzer. As the infrared gas analyzer, Fuji Electric Co., Ltd., product name "ZKJ", can be used. The content of gas B is calculated by determining the content of gas B (mol) from the measurement results of the infrared gas analyzer, calculating the molar concentration from the total molar amounts of the other components constituting the mixed gas, and taking this molar concentration as the content of gas B (volume %).

[0025] The mixed gas according to this embodiment is used to regenerate the adsorbent that has adsorbed the adsorbed components.

[0026] The mixed gas according to this embodiment can be produced by mixing product gas A, product gas B, and humidified gas A. An example of product gas A is product CO2. ２ The gas can be purchased from Fujii Shoji Co., Ltd. (purity: 99.5% by volume or higher). An example of product gas B is product CH. ４ The gas can be purchased from Fujii Shoji Co., Ltd. (purity: 99.9% by volume or higher). Humidified gas A can be produced, for example, by blowing product gas A into a water tank.

[0027] The mixed gas according to this embodiment may be produced by gas separation using a PSA method from a raw material gas containing water vapor, gas A, and gas B. Specifically, the process includes an adsorption step (hereinafter also simply referred to as the "adsorption step") in which the raw material gas is supplied to an adsorption tower having a desiccant and an adsorbent, and gas B is separated from the raw material gas by adsorbing water vapor onto the desiccant and gas A onto the adsorbent, and a desorption step (hereinafter also simply referred to as the "desorption step") in which the pressure inside the adsorption tower is reduced. In the adsorption step, the raw material gas is brought into contact with the desiccant and the adsorbent in that order inside the adsorption tower, and in the desorption step, the pressure inside the adsorption tower is reduced from the inlet side of the raw material gas, thereby discharging the mixed gas out of the adsorption tower in a countercurrent direction to the raw material gas flow direction in the adsorption step. The mixed gas may be produced continuously by switching between two or more adsorption towers.

[0028] When producing the mixed gas according to this embodiment by gas separation using the PSA method, it is preferable to further include a step of draining the gas present in the tower after the adsorption step and before the desorption step (hereinafter also simply referred to as the "drainage step"). The gas drained from the adsorption tower may (1) be combined with the raw material gas, or (2) be flowed into another adsorption tower (which is under reduced pressure after the desorption step) (hereinafter, the former step will be referred to as the pressure reduction step, and the latter step as the inflow step). This makes it possible to reduce the amount of gas B remaining in the tower before the start of the desorption step, making it easier to keep the concentration of gas B in the produced mixed gas at 2.0 volume percent or less.

[0029] When the mixed gas according to this embodiment is produced by gas separation using the PSA method, a repressurization step (hereinafter also simply referred to as the "repressurization step") may be further included, in which gas B with a purity of 50% or more is supplied into the column after the desorption step. By supplying gas B with a purity of 50% or more into the column through the repressurization step, the pressure is restored, which prevents the raw material gas from flowing rapidly into the column initially when it is subjected to the adsorption step, thus preventing water vapor and gas A from passing through without being adsorbed by the adsorbent, and thus increasing the purity of gas B. As a result, high-purity gas B can be obtained as a by-product in the adsorption step.

[0030] When producing the mixed gas according to this embodiment by gas separation using the PSA method, two or more towers containing adsorbent are used in rotation. First, as an example, the method for producing the mixed gas according to this embodiment by gas separation using the PSA method will be explained using the case where two adsorption towers, adsorption tower a and adsorption tower b, containing adsorbent, are used. Figure 5 is a schematic flow diagram of the method for producing the mixed gas according to this embodiment. Figure 3 shows the processes carried out in adsorption tower a and adsorption tower b, respectively. In adsorption tower a and adsorption tower b, the adsorption process and the desorption process are repeatedly performed to separate gas A (easily adsorbable gas) and gas B (difficult to adsorb gas). The adsorption process is terminated based on the temperature change inside the adsorption tower detected by a provided measuring unit, and in the desorption process, gas A (easily adsorbable gas) adsorbed in the adsorption process is desorbed from the adsorbent. As a result, the adsorbent is regenerated and the adsorption process can be performed again. If the adsorption process is performed in adsorption tower a while the adsorbent is regenerated in adsorption tower b through a desorption process, then after the adsorption process in adsorption tower a is completed, the system can be switched to perform the adsorption process in adsorption tower b.

[0031] As shown in Figure 3, the raw material gas is supplied to adsorption tower a and the adsorption process is performed. If the pressure inside adsorption tower a has risen after the adsorption process is completed, a pressure reduction process may be performed. Subsequently, in the inflow process, adsorption tower a and adsorption tower b, which has been reduced in pressure by the desorption process, are connected, and the raw material gas remaining in adsorption tower a is allowed to flow into adsorption tower b. It is preferable that in adsorption tower b, the desorption process is performed prior to the inflow process to desorb water vapor and gas A from the adsorbent and reduce the pressure.

[0032] After the aforementioned inflow process, a desorption process is performed in adsorption tower a to recover water vapor and gas A, and to regenerate the adsorbent.

[0033] While the desorption process is performed in adsorption tower a, the adsorption process is performed in adsorption tower b. A repressurization process may be performed before the adsorption process. If the pressure inside adsorption tower b has risen after the adsorption process is completed, a pressure reduction process may be performed.

[0034] Subsequently, in the inflow process, adsorption tower b and adsorption tower a are connected, and the raw material gas remaining in adsorption tower b is introduced into adsorption tower a. In adsorption tower a, a repressurization process may be performed after the inflow process. Adsorption tower a is then subjected to the adsorption process again. Meanwhile, in adsorption tower b, after the inflow process, it is subjected to a desorption process and then subjected to the inflow process again. By repeating the above process, a mixed gas can be efficiently produced.

[0035] The following describes each process in detail, using as an example a gas separation apparatus having two or more towers containing adsorbents and dehumidifiers (hereinafter also simply referred to as "adsorption towers").

[0036] Figure 4 is a block diagram of a gas separation apparatus used in the gas separation method according to this embodiment. As shown in Figure 4, the gas separation apparatus includes two or more towers containing adsorbent, namely adsorption tower a and adsorption tower b, a raw material supply unit, a mixed gas product storage unit, a gas B product storage unit, and a pressure reducing device. The gas separation apparatus has a first flow path switching unit C1 and a second flow path switching unit C2 that can be switched to a flow path that allows raw material gas to be supplied to adsorption tower a or adsorption tower b in the adsorption process and introduces gas B into the gas B product storage unit; a flow path that connects adsorption tower a or adsorption tower b to the raw material supply unit and supplies the raw material gas remaining in the adsorption tower to the raw material supply unit in the pressure reduction process; a flow path that connects adsorption tower a and adsorption tower b in the inflow process; and a flow path that reduces the pressure inside adsorption tower a or adsorption tower b using a pressure reducing device in the desorption process. The first flow path switching unit C1 and the second flow path switching unit C2 can be configured to achieve the above functions with a plurality of pipes and automatic valves, as will be described later.

[0037] <Adsorption Tower> The adsorption tower is filled with an adsorbent and a desiccant. Two or more adsorption towers used in this embodiment may have different configurations, but it is preferable to use adsorption towers with the same configuration.

[0038] The adsorption tower is configured to allow the introduction of a raw material gas and the contact between the adsorbent and the raw material gas. In the adsorption process, by contacting the raw material gas with the adsorbent, gas A in the raw material gas is adsorbed by the adsorbent, and water vapor is adsorbed by the desiccant. Since gas A and water vapor in the raw material gas are adsorbed, gas B can be extracted. Furthermore, after the adsorption process, in the desorption process, the adsorption tower is depressurized to extract the product mixed gas. In this way, purified gas B and the product mixed gas are obtained in the adsorption and desorption processes.

[0039] An adsorption tower has a portion filled with adsorbent (hereinafter also referred to as the "adsorbent layer"), a portion filled with desiccant (hereinafter also referred to as the "desiccant layer"), and a portion that is not filled with adsorbent or desiccant. From the viewpoint of keeping the concentration of gas B in the adsorbent layer at 2.0 volume% or less and reducing pressure loss, the packing rate of the adsorbent is preferably 90 volume% or less, more preferably 65 to 80 volume%, and even more preferably 67 to 70 volume%. Here, the packing rate (volume%) is calculated by the following formula: Packing rate = [Volume of adsorbent] / [Volume in the adsorbent layer] × 100 Note that the volume of the adsorbent is expressed as adsorbent mass / bulk density. Similarly, regarding the packing rate of the desiccant, from the same viewpoint as the packing rate of the adsorbent, it is preferably 90 volume% or less, more preferably 65 to 80 volume%, and even more preferably 67 to 70 volume%.

[0040] In the portions of the adsorption tower that are not filled with adsorbent and desiccant, inert balls may be filled, for example, to promote diffusion perpendicular to the gas flow.

[0041] A smaller number of adsorption towers is preferable because it reduces the size of the separation apparatus. However, if there are too few towers, it becomes difficult to switch between multiple adsorption towers and continuously separate the gas. The number of adsorption towers is preferably two to six, more preferably two to four, and even more preferably three.

[0042] (Adsorbent) As the adsorbent, it is preferable to use a solid adsorbent. More specifically, examples of solid adsorbents include zeolite, metal-organic framework (MOF), carbonaceous char, activated carbon, reactivated carbon, carbon black, graphite, silica, silica gel, alumina clay, and metal oxides. Among these, it is preferable to use zeolite or activated carbon.

[0043] From the viewpoint of ensuring that the concentration of gas B in the mixed gas is 2.0 volume% or less, the adsorbent preferably has an adsorption capacity of 10 cc / g or more for gas A, such as carbon dioxide. The adsorption capacity for gas A (easily adsorbable gas) is preferably 20 cc / g or more, more preferably 40 cc / g or more, and even more preferably 50 cc / g or more. The upper limit of the adsorption capacity for gas A is not particularly limited, but for example, it is 100 cc / g or less. In the inflow process and pressure drop process, the gas adsorbed by the adsorbent washes away the gas B remaining in the tower, so the amount of gas B remaining in the tower can be reduced before the start of the desorption process, making it easier to ensure that the concentration of gas B in the produced mixed gas is 2.0 volume% or less. Furthermore, when the target to be separated is biogas, biogas generally contains methane and carbon dioxide, but high-purity biomethane with high market value can be recovered as gas B.

[0044] Examples of zeolites include CHA-type zeolite, GIS-type zeolite, FAU-type zeolite, MWF-type zeolite, and LTA-type zeolite. Among these, GIS-type zeolite or FAU-type zeolite is preferred, with GIS-type zeolite being preferred.

[0045] GIS-type zeolite is preferably composed mainly of silica and alumina. The main component is defined as a component that accounts for 51% or more by mass.

[0046] GIS-type zeolite may contain silica and alumina. The aluminum (Al) content in the GIS-type zeolite is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more. The silicon content in the GIS-type zeolite is preferably 3% by mass or more, and more preferably 5% by mass or more. The upper limit of the aluminum (Al) and silicon (Si) content is preferably such that the SAR described later satisfies a predetermined range, and is determined by the value of said SAR.

[0047] In GIS-type zeolites, the silica-alumina ratio (represented as the molar ratio of silica to alumina expressed as SiO2 / Al2O3, hereinafter also referred to as "SAR") is preferably 3.40 or higher. The lower the SAR of a GIS-type zeolite, the more hydrophilic it becomes, and the stronger its adsorption capacity for polar molecules such as carbon dioxide. If the SAR is too low, the adsorption capacity is too strong, requiring more energy to desorb by heating or vacuuming, so a higher SAR is preferable. However, if the SAR is too high, the interaction with the adsorbate becomes weak. The SAR is more preferably 4.40 to 3000, even more preferably 4.60 to 500, and even more preferably 4.80 to 100.

[0048] The phosphorus (P) content in GIS-type zeolite is preferably 4% by mass or less. The lower limit of the phosphorus content is not particularly limited and may be 0% by mass or more.

[0049] The zirconium (Zr) content in GIS-type zeolite is preferably 8% by mass or less. The lower limit of the Zr content is not particularly limited and may be 0% by mass or more.

[0050] The titanium (Ti) content in GIS-type zeolite is preferably 8% by mass or less. The lower limit of the Ti content is not particularly limited and may be 0% by mass or more.

[0051] From the viewpoint of further improving the selective adsorption capacity of carbon dioxide, it is more preferable that the phosphorus atom content in the zeolite be 1.5% by mass or less, and particularly preferable that it be 0% by mass.

[0052] Furthermore, the content of aluminum (Al), silicon (Si), phosphorus (P), zirconium (Zr), and titanium (Ti) can be measured by the method described in the examples below. The content of aluminum (Al), silicon (Si), phosphorus (P), zirconium (Zr), and titanium (Ti) can also be adjusted to the above-mentioned range by, for example, adjusting the composition ratio of the mixed gel used in the synthesis of the GIS-type zeolite to a preferred range described below.

[0053] From the viewpoint of improving the selective adsorption capacity of easily adsorbed gases such as carbon dioxide, it is preferable, and more preferable, for potassium to be included as the cation species in the GIS-type zeolite. The total content of potassium and lithium in the zeolite is calculated as the ratio (Z / T) of the total amount of substance of potassium and lithium to the total amount of substance of alkali metals (T) in the GIS-type zeolite. Z / T is preferably 0.05 or higher, more preferably 0.10 or higher, and even more preferably 0.15 or higher. There is no particular upper limit to Z / T, but Z / T may be 1.00 or lower. Z / T can be measured by thermally dissolving the zeolite in an aqueous sodium hydroxide solution or aqua regia and performing ICP-emission spectroscopy analysis using a solution that has been appropriately diluted. More specifically, Z / T can be measured by the method described in the examples below. Z / T can be adjusted by changing the ratio of potassium and lithium as cation species in the GIS-type zeolite.

[0054] The ratio of the amount of substance of potassium (K) to the total amount of substance of each alkali metal (T) in the GIS-type zeolite (K / T) is preferably 0.05 or higher, more preferably 0.10 or higher, and even more preferably 0.15 or higher. There is no particular upper limit to K / T, but K / T may be 1.00 or lower.

[0055] From the perspective of the energy required for desorption, a higher SAR is preferable. However, in GIS-type zeolites, it has been confirmed that when the SAR is high, adsorption-desorption hysteresis becomes apparent in the adsorption-desorption isotherm of gas A (easily adsorbed gas). In GIS-type zeolites, adsorption-desorption hysteresis in the adsorption-desorption isotherm of gas A (easily adsorbed gas) can be eliminated by controlling the bonding mode of Si and Al in the zeolite framework. Specifically, ２９ When the peak area intensities attributed to Q4(3Al), Q4(2Al), Q4(1Al), and Q4(0Al) observed in the Si-MAS-NMR spectrum are denoted as a, b, c, and d, respectively, it is preferable that (a+d) / (b+c)≧0.192 is satisfied, more preferably 0.913≧(a+d) / (b+c)≧0.195, and even more preferably 0.519≧(a+d) / (b+c)≧0.199. The peaks Q4(3Al), Q4(2Al), Q4(1Al), and Q4(0Al) observed in the Si-MAS-NMR spectrum represent the bonding modes of Si and Al in the zeolite framework, X and Y, which are the sums of the area intensities, represent the sum of the abundances of these bonding modes, and Z represents the abundance ratio. The relative abundance of silicon (Si) and aluminum (Al) bonding modes affects the structural changes of the zeolite skeleton itself during adsorption and desorption. Therefore, by setting the relative abundance of Si and Al bonding modes (Z) within the zeolite skeleton to an appropriate range, adsorption-desorption hysteresis in the adsorption-desorption isotherm can be eliminated.

[0056] ２９ Si-MAS-NMR spectra are prepared by preparing a desiccator with water at the bottom and maintaining a zeolite sample tube in the upper part of the desiccator at room temperature (25°C) for 48 hours to control humidity, after which measurements are taken using a solid-state NMR measuring device. An example of a solid-state NMR measuring device is the JEOL "RESONANCE ECA700" (magnetic field strength: 16.44 T (resonance frequency at 1H: 700 MHz)).

[0057] The GIS-type zeolite of this embodiment is ２９ In Si-MAS-NMR spectra, the following five peaks are generally observed.

[0058] ​(1) Q4(0Al): Peak of Si that is not bonded to Al at all via oxygen (2) Q4(1Al): Peak of Si bonded to one Al via oxygen (3) Q4(2Al): Peak of Si bonded to two Al via oxygen (4) Q4(3Al): Peak of Si bonded to three Al via oxygen (5) Q4(4Al): Peak of Si bonded to four Al via oxygen Also, ２９ In the Si-MAS-NMR spectrum, these peaks are generally located between -112 ppm and -80 ppm and can be attributed to Q4(0Al), Q4(1Al), Q4(2Al), Q4(3Al), and Q4(4Al) from the high-field side. The peak positions may vary depending on the cation species present in the zeolite framework, but generally the peaks are located within the following range.

[0059] (1) Q4(0Al): -105 ppm to -112 ppm (2) Q4(1Al): -100 ppm to -105 ppm (3) Q4(2Al): -95 ppm to -100 ppm (4) Q4(3Al): -87 ppm to -95 ppm (5) Q4(4Al): -80 ppm to -87 ppm ２９ The peak area intensity of the Si-MAS-NMR spectrum is obtained by analyzing it using the analysis program dmfit (version #202000113) with Gaussian and Lorentz functions, and optimizing four parameters—amplitude (height of the maximum value of the spectrum), position (spectral position, ppm), width (full width at half maximum of the spectrum, ppm), and Gauss / Lorentz ratio (xG / (1-x)L)—using the least squares algorithm.

[0060] Using the peak area intensities obtained from this calculation, the peak area intensities a, b, c, and d assigned to Q4(3Al), Q4(2Al), Q4(1Al), and Q4(0Al) can be determined.

[0061] ２９ ​The Si-MAS-NMR spectrum can be measured in more detail by the method described in the examples below. To set (a+d) / (b+c) within a predetermined range, it is possible to add a salt compound containing an alkali metal and / or an alkaline earth metal and adjust the ratio of the cations resulting from the addition of the salt compound to the aluminum source.

[0062] [Method for producing the adsorbent] (Preparation step) The above-mentioned GIS-type zeolite can be obtained by a production method that includes, for example, a preparation step of a mixed gel containing a silica source containing silicon, an aluminum source containing aluminum, an alkali source (not a salt) containing at least one selected from alkali metals (M1) and alkaline earth metals (M2), an alkali salt compound containing at least one selected from alkali metals (M1) and alkaline earth metals (M2), a phosphorus source containing phosphorus, an organic structure-defining agent, and water.

[0063] (Hydrothermal Synthesis Process) In the method for producing GIS-type zeolite, it is preferable to further include a hydrothermal synthesis process in which the hydrothermal synthesis temperature is 80°C to 200°C. The hydrothermal synthesis temperature is preferably 100°C to 180°C. The mixed gel obtained in the preparation process is subjected to hydrothermal synthesis by holding it at a predetermined temperature for a predetermined time, either by stirring or standing. The time for hydrothermal synthesis is not particularly limited as long as it is a commonly used time, but is preferably 3 hours to 30 days, more preferably 10 hours to 20 days, and even more preferably 24 hours to 10 days.

[0064] (Separation and Drying Process) After the hydrothermal synthesis process, the solid product and the liquid containing water are separated. The separation method is not particularly limited as long as it is a general method, and methods such as filtration, decantation, spray drying (rotary spray, nozzle spray, ultrasonic spray, etc.), drying using a rotary evaporator, vacuum drying, freeze-drying, or natural drying can be used, and separation can usually be achieved by filtration or decantation.

[0065] (Casturing process) In the method for producing GIS-type zeolite, it is preferable to further include a calcination process in which the calcination temperature is 300°C to 450°C. The calcination temperature is more preferably 350°C to 420°C, and even more preferably 360°C to 400°C or lower. The calcination time may be 0.5 hours to 10 days, 1 hour to 7 days, or 3 hours to 5 days. The calcination atmosphere is not particularly limited as long as it is a commonly used atmosphere, but usually an air atmosphere, an inert gas such as nitrogen or argon, or an atmosphere with added oxygen is used.

[0066] (Cation Exchange Step) In a method for producing GIS-type zeolite, it is preferable to further include a cation exchange step. The cation exchange can be performed using, but is not limited to, carbonates such as sodium carbonate, potassium carbonate, lithium carbonate, rubidium carbonate, cesium carbonate, magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, and ammonium carbonate; nitrates such as sodium nitrate, potassium nitrate, lithium nitrate, rubidium nitrate, cesium nitrate, magnesium nitrate, calcium nitrate, strontium nitrate, barium nitrate, and ammonium nitrate; salts obtained by changing the carbonate ions and nitrate ions contained in the carbonates and nitrates to halide ions, sulfate ions, carbonate ions, bicarbonate ions, acetate ions, phosphate ions, or hydrogen phosphate ions; or acids such as nitric acid and hydrochloric acid. The temperature for cation exchange is not particularly limited as long as it is a general cation exchange temperature, but is usually from room temperature to 100°C or below.

[0067] When separating zeolite after cation exchange, the separation method is not particularly limited as long as it is a general method, and methods such as filtration, decantation, spray drying (rotary spray, nozzle spray, ultrasonic spray, etc.), drying using a rotary evaporator, vacuum drying, freeze-drying, or natural drying can be used, and separation can usually be achieved by filtration or decantation.

[0068] (Dehumidifier) ​​Examples of dehumidifiers include activated alumina, silica gel, zeolite, and activated carbon. Among these, activated carbon or activated alumina is preferred as a dehumidifier from the viewpoint of resistance to liquid water, and activated alumina is more preferred. When the raw material gas contains 0.1 vol% or more of water, or when the raw material gas is supplied under pressure, there is a possibility that water will condense and liquid water will be generated. Therefore, a dehumidifier that does not significantly reduce the strength of the adsorbent molded body even when immersed in water is suitable.

[0069] The water vapor adsorption capacity of the desiccant is preferably 2.37 mol / kg or more, and more preferably 2.77 mol / kg or more, under conditions of a partial pressure of 1 kPa of water vapor and 35°C. The water vapor adsorption capacity of the desiccant is preferably 1.98 mol / kg or less, and more preferably 0.59 mol / kg or less, under conditions of a partial pressure of 0.01 kPa of water vapor and 35°C, in order to rapidly desorb water vapor during desorption. The water vapor adsorption capacity of the adsorbent is measured by introducing saturated water vapor of water at the measurement temperature of 35°C into the adsorbent to an absolute pressure of 0.01 to 5.4 kPa. During the measurement, the pressure is measured over time, and when the pressure fluctuation becomes 0.3% / 300 sec or less, it is determined that the saturated adsorption amount has been reached, and this is taken as the adsorption capacity at 35°C (unit: mol / kg). Furthermore, the adsorption capacities at partial pressures of water vapor of 1 kPa and 0.01 kPa are determined by creating adsorption isotherms that show the relationship between the change in pressure over time and the adsorption capacity, based on the measurement results used to determine the adsorption capacity, and then using the adsorption capacities at each pressure that can be read from these adsorption isotherms.

[0070] <Raw Material Supply Section> The raw material supply section refers to the raw material gas tank or piping located upstream of the booster equipment. The raw material supply section is filled with raw material gas. The raw material gas is boosted to a predetermined pressure by the booster from the raw material supply section and flows into the adsorption tower.

[0071] <Product Mixed Gas Storage Section> The product mixed gas storage section is filled with the manufactured mixed gas. In the desorption process, gas A and water vapor desorbed from the adsorbent and desiccant are stored in the product mixed gas storage section.

[0072] <Product Gas B Storage Section> The product gas B storage section is filled with purified gas B. In the adsorption process, gas B obtained by passing through the adsorption tower is stored in the product gas B storage section. In the repressurization process, gas B may be introduced from the product gas B storage section to the adsorption tower, which has a lower pressure, to increase the pressure of the adsorption tower. The product gas B storage section stores the gas B obtained in the adsorption process and plays the role of introducing a portion of it into the adsorption tower and increasing its pressure in the repressurization process. The product gas B storage section only needs to be large enough to supply a sufficient amount of gas B by connecting to the adsorption tower in the repressurization process (for example, equal to or greater than the volume of the adsorption tower), and gas B that overflows from the product gas B storage section after it is filled in the adsorption process may be introduced into a gas bag (not shown). When introducing into a gas bag, it is preferable to provide a back pressure valve downstream of the product gas B storage section and keep the valve closed until the product storage section reaches a predetermined pressure, and then open it.

[0073] [Raw material gas] The raw material gas used as raw material includes water vapor, gas A, and gas B. The content of gas A in the raw material gas may be 1% to 99% by volume, 5% to 90% by volume, 10% to 80% by volume, 20% to 70% by volume, or 30% to 70% by volume.

[0074] Each step of the gas separation method according to this embodiment will be described in detail.

[0075] <Adsorption Process> In the adsorption process, the raw material gas is supplied to an adsorption tower having a desiccant and an adsorbent, and gas B is separated from the raw material gas by adsorbing water vapor onto the desiccant and gas A onto the adsorbent. In the adsorption process, the raw material gas is brought into contact with the desiccant and the adsorbent in that order within the adsorption tower. In the adsorption process, the raw material gas may be passed through at least one of two or more adsorption towers to adsorb gas A onto the adsorbent in the tower and water vapor onto the desiccant in the tower, thereby separating and recovering gas B (a poorly adsorbed gas) from the raw material gas.

[0076] The pressure inside the adsorption tower during the adsorption process affects the purity of the recovered gas B. From the viewpoint of increasing the purity of gas B, a higher pressure in the adsorption process is desirable, but if it is too high, the cost required to increase the pressure will increase. Therefore, the pressure inside the adsorption tower during the adsorption process is preferably between 101.3 kPa and 700 kPa, and more preferably between 200 kPa and 400 kPa.

[0077] <Depressurization Process> In the depressurization process, a portion of the raw material gas inside the adsorption tower is released to reduce the pressure inside the tower, and the raw material gas released in the depressurization process is then supplied to the adsorption process. In the depressurization process, it is preferable that the inside of the adsorption tower is pressurized before the depressurization. "Pressurized state" means that the pressure is greater than 101.3 kPa.

[0078] In the pressure reduction process, it is preferable to connect the pressurized adsorption tower to the raw material supply section. As a portion of the gas flows from the adsorption tower to the raw material supply section, the pressure in the adsorption tower decreases to the pressure in the raw material supply section. In other words, the pressure reduction process causes the gas in the adsorption tower to move to the raw material supply section until the pressures in the adsorption tower and the raw material supply section become equal.

[0079] In the pressure reduction process, it is preferable to discharge the gas in a direction parallel to the raw material gas and supply it to the raw material supply section. When the gas in the tower is discharged in the pressure reduction process, the pressure inside the tower decreases, causing the adsorbed gas to desorb from the adsorbent. However, in the case of parallel flow, at the end of the adsorption process, unused adsorbent that has not adsorbed gas A will be located downstream of the gas discharged from the adsorption tower. Since the unused adsorbent is exposed to high-purity gas B, which has been purified by the adsorbent packed on the raw material gas inlet side, during the adsorption process, even though gas B is a gas that is difficult to adsorb, its adsorption capacity is large, and if the desorption process is carried out without desorbing the gas B adsorbed on the unused adsorbent, the concentration of gas B in the produced mixed gas will be high. When the gas in the tower is discharged in a direction parallel to the raw material gas and supplied to the raw material supply section in the pressure reduction process, the gas B adsorbed on the unused adsorbent can be purged, thereby reducing the concentration of gas B in the produced mixed gas.

[0080] From the viewpoint of reducing the concentration of gas B in the product mixed gas, the pressure after the depressurization process is preferably 101.3 kPa or more and 120.0 kPa or less, more preferably 101.3 kPa or more and 110.0 kPa or less, and even more preferably 101.3 kPa or more and 105.0 kPa or less.

[0081] <Inflow Process> In the inflow process, the raw material gas remaining in the adsorption tower after the adsorption process is allowed to flow into another adsorption tower. Specifically, the valves from the adsorption tower to the product storage section and the raw material supply section are closed, and the adsorption tower used in the adsorption process is connected to another adsorption tower. When two adsorption towers are connected, gas flows from the adsorption tower with higher pressure to the adsorption tower with lower pressure, and the pressures in the two adsorption towers become roughly equal. For this reason, this operation is sometimes called pressure equalization. In this way, in the inflow process, a portion of the gas in the adsorption tower is allowed to flow in using the pressure difference between the towers. For example, if an adsorption tower that has completed the adsorption process is connected to another adsorption tower that has completed the desorption process, gas flows from the adsorption tower that has completed the adsorption process to the other adsorption tower that has completed the desorption process. The tower used in the inflow process may be a tower that has completed the pressure reduction process after completing the adsorption process.

[0082] The following example will be given, where adsorption tower a is used in the adsorption process, adsorption tower b is used in the desorption process, and then the other towers are used in the inflow process. In addition, in the gas separation method according to this embodiment, adsorption tower b may be used in the adsorption process, adsorption tower a may be used in the desorption process, and then the other towers are used in the inflow process.

[0083] At the start of the inflow process into adsorption tower a, the pressure in adsorption tower a is equal to the pressure after the end of the adsorption process or the pressure drop process. On the other hand, the pressure at the end of the inflow process varies depending on the pressure in the connected adsorption tower b, the type of adsorbent, etc. In the inflow process, in addition to gas movement due to the pressure difference between towers, adsorption of gas A occurs in the destination tower, causing a slight pressure drop in the destination tower, and then gas movement occurs again to equalize the pressure between towers. As a result, it takes several tens of seconds for the pressure after inflow to become constant. The pressure after inflow in the inflow process refers to the pressure after the pressure has become constant.

[0084] In the inflow process, the lower the pressure in adsorption tower a (adsorption tower before the desorption process), the more gas B will be sent into other towers. This results in a lower pressure before the start of the subsequent desorption process, thus lowering the concentration of gas B in the mixed gas produced in the desorption process. On the other hand, if the pressure after inflow in the inflow process is too low, although more gas B will be sent into other towers in the inflow process, gas A adsorbed on the adsorbent will be desorbed and sent in, reducing the amount of gas A recovered in the desorption process.

[0085] For the reasons stated above, in terms of the concentration of gas B in the mixed gas produced, the pressure of the adsorption tower after the adsorption process following the inflow process is preferably 2 kPa or more and 80 kPa or less, more preferably 5 kPa or more and 60.0 kPa or less, and even more preferably 10 kPa or more and 40.0 kPa or less.

[0086] In the inflow process, the pressure in adsorption tower b increases after the desorption process. The pressure in adsorption tower b at the start of the inflow process may be the pressure after the desorption process is completed. The pressure in the tower after the desorption process following the inflow process is preferably 2 kPa or more and 80 kPa or less, more preferably 5 kPa or more and 60.0 kPa or less, and even more preferably 10 kPa or more and 40.0 kPa or less. The pressures in adsorption tower a and adsorption tower b after the inflow process may be the same or different.

[0087] In the inflow process, some of the water vapor adsorbed on the desiccant layer may also leak out. If the adsorbent is, for example, zeolite, the adsorption capacity for gas A may irreversibly decrease due to the adsorption of water vapor. Therefore, when connecting to another tower to feed in the gas leaking out in the inflow process, it is preferable to ensure that the moving gas does not pass through the adsorbent. Specifically, when connecting two adsorption towers in the inflow process, it is preferable to connect the raw material gas inlets of the adsorption towers to each other.

[0088] <Desorption Process> In the desorption process, the mixed gas is discharged outside the adsorption tower by reducing the pressure inside the tower. In the desorption process, the pressure inside the adsorption tower may be reduced using a depressurizing device. In the desorption process, the mixed gas may be discharged outside the adsorption tower in a counter-flow direction relative to the raw material gas flow direction in the adsorption process by reducing the pressure inside the adsorption tower from the raw material gas inlet side. When the pressure inside the adsorption tower is reduced, gas A adsorbed on the adsorbent is desorbed. In this way, the adsorbent is regenerated and a mixed gas is produced.

[0089] During the desorption process, the pressure in the adsorption tower decreases. The pressure at the start of the desorption process becomes the pressure at the end of the inflow process. If the adsorption tower is used as "another tower" in the inflow process after the completion of the desorption process, the lower the pressure at the end of the desorption process, the lower the tower pressure at the end of the inflow process, which improves the recovery rate of gas B and reduces the concentration of gas B in the produced mixed gas. Therefore, from the viewpoint of the concentration of gas B in the produced mixed gas, the pressure at the end of the desorption process is preferably 50.0 kPa or less, more preferably 30.0 kPa or less, and even more preferably 10.0 kPa or less. The lower limit is not particularly limited, but if it is too low, too much energy will be required for separation, so it is preferable to set it to 1 kPa or higher, and in practical terms, it is preferable to set it to 2 kPa or higher.

[0090] In the desorption process, water vapor adsorbed on the desiccant layer is also desorbed. Since water vapor has a higher adsorption capacity than gas A, desorption does not proceed even when the pressure inside the adsorption tower is reduced to a few kPa during the desorption process, making repeated use difficult in many cases. To overcome this, in addition to reducing the total pressure during system depressurization, one measure is to lower the gas phase moisture pressure near the adsorbent by flowing a purge gas different from water vapor, thereby promoting desorption. In a multilayer system in which the desiccant and gas A adsorbents are packed in layers, the raw material gas introduced during the adsorption process and gas A passing through the adsorption tower in countercurrent act as purge gases, promoting the desorption of water vapor from the desiccant layer. In the gas separation method according to this embodiment, the gas discharged outside the adsorption tower during the desorption process is used as the mixed gas according to this embodiment, but during the desorption process, gas A containing water vapor desorbed from the desiccant layer inside the adsorption tower may become part of the composition of the mixed gas according to this embodiment. In this case, the desorption step in the gas separation method according to this embodiment corresponds to partially performing the process of producing the mixed gas according to this embodiment and desorbing and regenerating the water vapor adsorbed on the adsorbent by the mixed gas according to this embodiment within the adsorption tower.

[0091] <Repressurization Process> In the repressurization process, gas B (a poorly adsorbed gas) with a purity of 50% or more is supplied into the tower. If the adsorption process is carried out after the desorption process is completed, or after the desorption process and after the inflow process is completed, without going through the repressurization process, the raw material gas will be supplied into the adsorption tower in a low-pressure state. As a result, the velocity of the raw material gas passing through the adsorption tower will be too high, and gas A (an easily adsorbed gas) contained in the raw material gas may not be sufficiently adsorbed by the adsorbent and may flow into the product gas B containment section. Therefore, if it is necessary to improve the purity of product gas B, it is preferable to carry out the repressurization process after the desorption process is completed.

[0092] The purity of gas B (a poorly adsorbed gas) supplied in the repressurization process is preferably 50% or higher, more preferably 75% or higher, and even more preferably 90% or higher. For example, gas B recovered in the adsorption process may be introduced into the adsorption tower from the product gas B containment section. If gas B is recovered in the adsorption process, it can be separated without reducing the purity of the recovered gas B even if it is subjected to the adsorption process again after repressurization. Since the gas introduced into the adsorption tower is not easily adsorbed by the adsorbent, the pressure inside the tower is increased. In this way, in the repressurization process, gas B is introduced into the adsorption tower and pressurized to a predetermined pressure. It is preferable to pressurize to the pressure of the adsorption process, but when pressurizing with gas introduced from the product gas B containment section, the pressure in the product gas B containment section decreases as the gas flows out, so depending on the size of the product containment section relative to the adsorption tower, it may not be possible to pressurize to the pressure of the adsorption process. Even a pressurization that occurs naturally according to the volume ratio of the product gas B containment section and the adsorption tower is effective in suppressing the decrease in the purity of gas B.

[0093] During the repressurization process, the pressure in the adsorption tower increases. The pressure at the start of the repressurization process may be the same as the pressure at the end of the desorption process or the pressure at the end of the inflow process. The pressure at the end of the repressurization process is preferably the same as the pressure at the start of the adsorption process, but it may be lower than the pressure at the start of the adsorption process.

[0094] After the repressurization process, the gas B introduced into the adsorption tower during the repressurization process is pushed out by the raw material gas supplied during the adsorption process and recovered as product gas B.

[0095] In the gas separation method according to this embodiment, the adsorption step, pressure drop step, inflow step, desorption step, inflow step, and repressurization step may be repeated depending on the amount of raw material gas to be processed and the composition of the desired mixed gas, and by repeating these steps, the mixed gas can be efficiently obtained.

[0096] In the gas separation method according to this embodiment, three or more adsorption towers may be used for the purpose of continuously separating gas while maintaining a constant amount of raw material gas. Constant means that the change in the flow rate of the raw material gas supplied from the raw material supply unit is within 10 mass percent throughout the operation of each process and at the time of switching to the next process. For example, the flow rate may increase or decrease instantaneously by opening and closing a valve to switch the raw material gas supply destination, but it is preferable to control the flow rate change to be within 10 mass percent, and more preferably within 5 mass percent, throughout the switching process. By suppressing the increase or decrease in flow rate, the load on the equipment is stabilized, so less capacity margin is required for the equipment. The time required for switching is not particularly limited as long as the gas flow rate is constant, but it can usually be completed in about 5 seconds.

[0097] An example of using three or more adsorption towers is to use three or more towers, and after the first tower is used for the adsorption process, switch the supply destination of the raw material gas to the second tower, and after the second tower is used for the adsorption process, switch the supply destination of the raw material gas to the third tower, thereby maintaining a constant supply rate of raw material gas to each tower.

[0098] Referring to Figure 5, we will explain in more detail, referring to the first tower as adsorption tower a, the second tower as adsorption tower b, and the third tower as adsorption tower c. While the adsorption process is being carried out in adsorption tower a, the desorption process is being carried out in adsorption tower c. After the adsorption process in adsorption tower a is completed, the supply destination of the raw material gas is switched to adsorption tower b and the desorption process is carried out thereafter, the pressure drop process is carried out in adsorption tower a, the inflow process is carried out in adsorption tower a and adsorption tower c, the desorption process is carried out in adsorption tower a, and then the pressure restoration process is carried out in adsorption tower c.

[0099] After the adsorption process is carried out in adsorption tower b, the supply destination of the raw gas is switched to adsorption tower c, adsorption tower b is depressurized, the inflow process is carried out in adsorption tower b and adsorption tower a, the desorption process is carried out in adsorption tower b, and the repressurization process is carried out in adsorption tower a.

[0100] After the adsorption process in adsorption tower c is completed, the supply destination of the raw material gas is switched to adsorption tower a. While the adsorption process is being carried out sequentially in adsorption tower b and adsorption tower c, adsorption tower a can continuously purify the raw material gas by performing a pressure drop process, an inflow process, a desorption process, an inflow process, and a repressurization process. A smaller number of adsorption towers is preferable because it reduces the size of the separation apparatus, but if there are too few, it becomes difficult to switch between multiple adsorption towers and continuously separate the gas. The number of adsorption towers is preferably two to six, more preferably two to four, and even more preferably three.

[0101] As described above, the gas separation method of this embodiment can produce a mixed gas from a raw material gas. Furthermore, the gas separation method of this embodiment can also be used to simultaneously produce not only a mixed gas but also high-purity gas B.

[0102] The gas separation apparatus and its operating mode according to the embodiment will be described in more detail below.

[0103] [Mixed Gas Production Apparatus 100] Referring to Figure 6, the general configuration of the mixed gas production apparatus 100 according to this embodiment will be described. The mixed gas production apparatus 100 includes a raw material gas supply line 1001, a raw material gas tank 1002, a pressurizing device 1003, adsorption towers 1005a and 1005b, a product gas B recovery line 1007, a product gas B storage section 1008, a pressure drop gas line 1010, an inflow gas line 1011, a product mixed gas recovery line 1014, a pressure reducing device 1015, a repressurizing gas line 1016, and a product mixed gas storage section 1025. The raw material gas supply line 1001 and the raw material gas tank 1002 are collectively referred to as the raw material supply section.

[0104] The adsorption tower 1005a has fixed beds 1020-1a and 1020-2a filled with an adsorbent and a desiccant configured to come into contact with the raw material gas introduced inside. One end of the adsorption tower 1005a is connected to the raw material gas supply line 1001, and the other end is connected to the product gas B recovery line 1007. The product gas B recovery line 1007 is equipped with an automatic valve AV 1006a. A product gas B containment section 1008 is connected to the end of the product gas B recovery line 1007.

[0105] The adsorption tower 1005a is connected to the pressure drop gas line 1010 at the end in the same direction as the end connected to the product gas B recovery line 1007. The raw material gas tank 1002 is connected to the end of the pressure drop gas line 1010. The raw material gas supply line 1001 may also be connected to the end of the pressure drop gas line 1010. An automatic valve AV 1009a is provided in the pressure drop gas line 1010 connected to the adsorption tower 1005a. The pressure drop gas line may also be connected to the end in the opposite direction from the end connected to the product gas B recovery line 1007.

[0106] The adsorption tower 1005a is connected to the product mixed gas recovery line 1014 at the end in the same direction as the end connected to the raw gas supply line 1001. The raw gas supply line 1001 is equipped with a raw gas tank 1002 and a pressurizing device 1003. The pressurizing device 1003 may be a compressor. An automatic valve AV 1004a is provided at the inlet of the adsorption tower 1005a. Meanwhile, a depressurizing device 1015 is connected to the product mixed gas recovery line 1014, and is configured to reduce the pressure inside the adsorption tower 1005a. The depressurizing device 1015 may be a vacuum pump. The product mixed gas recovery line 1014 may also be connected to the product mixed gas storage section 1025. Furthermore, the product mixed gas recovery line 1005 connected to the adsorption tower 1005a is equipped with an automatic valve AV 1013a.

[0107] The adsorption tower 1005a is connected to the repressurization gas line 1016 at the end in the same direction as the end connected to the product gas B recovery line 1007. The repressurization gas line 1016 is equipped with an automatic valve AV 1017a. The product gas B containment section 1008 is connected to the end of the repressurization gas line 1016.

[0108] The adsorption tower 1005b has fixed beds 1020-1b and 1020-2b filled with an adsorbent and a desiccant configured to come into contact with the raw material gas introduced inside. One end of the adsorption tower 1005b is connected to the raw material gas supply line 1001, and the other end is connected to the product gas B recovery line 1007. The product gas B recovery line 1007 is equipped with an automatic valve AV 1006b.

[0109] The adsorption tower 1005b is connected to the pressure drop gas line 1010 at the end in the same direction as the end connected to the product gas B recovery line 1007. The raw material gas tank 1002 is connected to the end of the pressure drop gas line 1010. The raw material gas supply line 1001 may also be connected to the end of the pressure drop gas line 1010. An automatic valve AV 1009b is provided in the pressure drop gas line 1010 connected to the adsorption tower 1005b. The pressure drop gas line may also be connected to the end in the opposite direction from the end connected to the product gas B recovery line 1007.

[0110] Adsorption tower 1005b is connected to the product mixed gas recovery line 1014 at the end in the same direction as the end connected to the raw gas supply line 1001. An automatic valve AV1004b is provided at the inlet of adsorption tower 1005b. Meanwhile, a depressurization device 1015 is connected to the product mixed gas recovery line 1014, and is configured to reduce the pressure inside adsorption tower 1005b. In addition, an automatic valve AV1013b is provided at the product mixed gas recovery line 1005, which is connected to adsorption tower 1005a.

[0111] The adsorption tower 1005b is connected to the repressurization gas line 1016 at the end in the same direction as the end connected to the product gas B recovery line 1007. The repressurization gas line is equipped with an automatic valve AV 1017b. The product gas B containment section 1008 is connected to the end of the repressurization gas line.

[0112] Adsorption towers 1005a and 1005b are connected by an inflow gas line 1011 at the end in the same direction as the end connected to the raw material gas supply line 1001. An automatic valve AV 1012 is provided in the inflow gas line 1011. The inflow gas line 1011 may also connect adsorption towers 1005a and 1005b at the end opposite to the end connected to the raw material gas supply line 1001, or it may connect adsorption towers 1005a and 1005b alternately at the end in the same direction as the end connected to the raw material gas supply line 1001 and the end opposite to it.

[0113] The gas separation apparatus may be equipped with pressure gauges for measuring the pressure at each position of the apparatus. The raw gas tank 1002 may be equipped with a pressure gauge 1018. The product gas B containment section 1008 may be equipped with a pressure gauge 1023. Pressure gauges 1022a and 1021a may be provided above and below the adsorption tower 1005a, respectively, and pressure gauges 1022b and 1021b may be provided above and below the adsorption tower 1005b, respectively. A pressure gauge 1019 may be provided downstream of the pressurizing device 1003, and a pressure gauge 1024 may be provided upstream of the depressurizing device 1015.

[0114] Next, with reference to Figure 6, the operation of the gas separation apparatus 100 of this embodiment will be described. Raw material gas for mixed gas production is supplied to the adsorption tower 1005a via the raw material gas supply line 1001. Then, gas A and water vapor contained in the raw material gas are adsorbed by the adsorbent and desiccant packed inside the adsorption tower 1005a, and product gas B is recovered from the product gas B recovery line 1007. In other words, in the adsorption tower 1005a, an adsorption process is performed in which raw material gas is introduced into the adsorption tower, gas A and water vapor are adsorbed by the adsorbent and desiccant, and gas B is extracted. During the adsorption process, the gas is introduced while maintaining the pressure in the adsorption tower at a constant predetermined pressure. Note that during the adsorption process, pressure loss occurs as the raw material gas flows through the adsorption tower, so a pressure difference may occur between the inlet and outlet of the adsorption tower.

[0115] After the adsorption process is complete, the gas inside the adsorption tower 1005a is released to the outside of the tower in order to reduce the pressure inside the tower. At this time, the gas inside the adsorption tower 1005a is recovered to the raw material supply section via the pressure drop gas line 1010. As the pressure inside the adsorption tower decreases, gas B is detached from the adsorbent, and some of the gas B remaining in the voids inside the adsorption tower is replaced by gas A. In other words, a pressure drop process is performed to recover gas B by allowing gas from inside the adsorption tower to flow in.

[0116] By connecting the adsorption tower 1005a and the adsorption tower 1005b via the inflow gas line 1011, the gas inside the adsorption tower 1005a is recovered into the adsorption tower 1005b. At this time, as the pressure inside the adsorption tower decreases, gas A is released from the adsorbent, and some of the gas B remaining in the voids inside the adsorption tower is further replaced by gas A. In other words, an inflow process is performed in which gas B is recovered by introducing the gas inside the adsorption tower.

[0117] The adsorption tower 1005a, which contains an adsorbent that has adsorbed gas A and a desiccant that has adsorbed water vapor, is depressurized by a depressurizing device 1015 to remove gas A and water vapor. This regenerates the adsorbent and desiccant in the adsorption tower 5a and extracts the product mixed gas. In other words, a desorption process is performed in which the product mixed gas is extracted by depressurizing and exhausting gas A and water vapor from the adsorption tower.

[0118] As described above, adsorption towers 1005a and 1005b repeatedly adsorb gas A and water vapor by introducing the raw material gas for mixed gas production and desorb gas A and water vapor by reducing the pressure. Therefore, while adsorption tower 1005a is desorbing gas A and water vapor, the raw material gas for mixed gas production is introduced into adsorption tower 1005b to adsorb gas A and water vapor. After the desorption of gas A and water vapor in adsorption tower 1005a is complete, the raw material gas for mixed gas production is introduced into adsorption tower 1005a again, and gas A and water vapor are desorbed in absorption tower 1005b by reducing the pressure. In this way, the adsorption and desorption of gas A and water vapor is repeatedly performed in each tower, and the raw material gas for mixed gas production can be processed continuously.

[0119] When adsorption tower 1005a is in the adsorption process and adsorption tower 1005b is in the desorption process, automatic valves AV1004a, AV1006a, and AV1013b are opened from the closed state of all automatic valves. By opening automatic valve AV1004a, which is located between the raw material gas tank 1002 and the adsorption tower 1005a, the raw material gas is introduced into the adsorption tower 1005a.

[0120] Next, a pressure reduction process may be provided. In the pressure reduction process, the valve from the adsorption tower 1005a to the product gas B containment section 1008 is closed, and the gas inside the tower is released from the pressurized adsorption tower to the raw material supply section. When switching from the adsorption process to the pressure reduction process in the adsorption tower 1005a, automatic valves AV1006a and AV1004a are closed, and automatic valve AV1009a in the pressure reduction gas line 1010 is opened. During this time, the desorption process may continue in the adsorption tower 1005b.

[0121] In the inflow process, only the automatic valve AV1012 installed in the inflow gas line 1011 opens, and the other automatic valves close. As a result, gas movement occurs only between the adsorption tower 1005a and the adsorption tower 1005b. For example, when the adsorption tower 1005a, which has completed the adsorption process, is connected to the adsorption tower 1005b, the pressure in the adsorption tower 1005a is higher than the pressure in the adsorption tower 1005b, so gas flows from the adsorption tower 1005a to the adsorption tower 1005b.

[0122] Next, a desorption process is performed in the adsorption tower 1005a. In the desorption process, automatic valves AV1004a, AV1006a, AV1009a, and AV1012 are closed, and automatic valve AV1013a is opened. Gas A and water vapor in the adsorption tower 1005a are introduced into the product mixed gas containment section 1025 by the depressurization device 1015.

[0123] On the other hand, after the inflow process, a repressurization process may be performed in the adsorption tower 1005b. The automatic valve AV1017b provided in the repressurization gas line 1016 is opened, and gas B is introduced from the product gas B containment section 1008 into the adsorption tower 1005b.

[0124] The mixed gas production apparatus 100 may use, for example, industrial exhaust gas containing carbon dioxide or biogas obtained by the fermentation of organic matter as the raw material gas for mixed gas production. Among these, biogas is preferred.

[0125] [Device 1000 for Producing Mixed Gas Using Biogas as Raw Material] Fig. 7 is a diagram showing the schematic configuration of a system 1000 in which biogas is applied as a raw material gas for producing a mixed gas in a mixed gas production device 100. In the application example, an example of separating and recovering methane, carbon dioxide, which are the main components of biogas, and trace amounts of water vapor to produce a mixed gas is shown. When biogas is used as the raw material gas for producing the mixed gas, usually, gas B is methane (CH ４ ), and gas A is carbon dioxide (CO ２ ).

[0126] The device 1000 for producing a mixed gas using biogas as a raw material in this embodiment includes a fermentation tank 200, a desulfurization tower 400, a siloxane removal device 500, an oxygen removal device 600, a cooling device 700, a dehydration device 800, and a gas separation device 100.

[0127] The fermentation tank 200 is a tank that generates biogas (hereinafter also referred to as "raw material gas for producing mixed gas") by fermenting sewage sludge generated from a sewage treatment plant, food residues generated from a food factory or a restaurant, and manure generated from a dairy farm, etc. in an anaerobic state. The fermentation tank 200 is connected to a blower 300 in order to supply the generated biogas to other devices.

[0128] The fermentation tank 200 may be connected to the desulfurization tower 400 before the biogas is introduced into the gas separation device 100. The desulfurization tower 400 is an adsorption tower for removing hydrogen sulfide contained in biogas. Examples of the desulfurizing agent filled in the desulfurization tower 400 include iron oxide. Iron oxide reacts with hydrogen sulfide contained in biogas to produce iron sulfide.

[0129] The fermentation tank 200 may be connected to the siloxane removal device 500 before the biogas is introduced into the gas separation device 100. The siloxane removal device 500 removes siloxane contained in biogas. This siloxane is a silicon oxide-containing substance contained in sewage sludge.

[0130] The fermentation tank 200 may be connected to an oxygen removal device 600 before the biogas is introduced into the gas separation device 100. The oxygen removal device 600 removes oxygen contained in the biogas. By removing this oxygen, the purified methane gas can be safely transported.

[0131] The fermentation tank 200 may be connected to a cooling device 700 before the biogas is introduced into the gas separation device 100. The cooling device 700 removes moisture contained in the biogas by cooling the supplied biogas. This lowers the dew point of the biogas. As the cooling device 700, for example, a water-cooled cooler, an air-cooled cooler, an electric cooler, etc., can be used.

[0132] Next, with reference to Figure 7, the operation of the biogas purification system 1000 of this embodiment will be described.

[0133] First, biogas is generated in the fermentation tank 200 by fermenting sewage sludge from sewage treatment plants, food waste from food factories and restaurants, and manure from dairy farmers, etc., under anaerobic conditions. The biogas at this stage contains hydrogen sulfide, water, and other substances.

[0134] The biogas generated in the fermentation tank 200 is sent to the desulfurization tower 400. In the desulfurization tower 400, hydrogen sulfide is removed from the biogas so that its concentration is at the level of several volumes ppm.

[0135] Subsequently, the biogas from which hydrogen sulfide has been removed is sent to the siloxane removal unit 500. In the siloxane removal unit 500, the concentration of siloxane contained in the biogas is reduced to several mg / Nm³. ３ Remove siloxane to achieve a level of saturation.

[0136] Subsequently, the biogas from which siloxane has been removed is sent to the oxygen removal device 600. In the oxygen removal device 600, oxygen is removed so that the oxygen concentration in the biogas is at the level of several volumes ppm.

[0137] Next, the biogas is sent to the cooling device 700. The cooling device 700 cools the biogas and removes the water contained in it, thereby lowering the dew point of the biogas.

[0138] The biogas, from which hydrogen sulfide, siloxane, and excess water have been removed, is sent to the gas separation unit 100. The operation of the gas separation unit 100 is as described above.

[0139] According to the gas separation method of this embodiment, high-purity methane and the mixed gas according to this embodiment can be efficiently recovered.

[0140] [Method for regenerating the adsorbent] The method for regenerating the adsorbent according to this embodiment involves circulating the mixed gas according to this embodiment through a container filled with the adsorbent to remove the adsorbed components.

[0141] The adsorbent component is not particularly limited, but examples include water, methane, and ethane. Among these, it is preferable to use it for regenerating adsorbents that have adsorbed water. When removing adsorbed water, removing water by placing the adsorbent under reduced pressure can require a lot of energy, but by regenerating it using the mixed gas according to this embodiment, the adsorbent can be regenerated with high energy efficiency.

[0142] The container is not particularly limited and may be, for example, a column that can be filled with an adsorbent, or an adsorption tower comprising one or more such columns. The container may be made of stainless steel (SUS).

[0143] The ratio (L / D) of the length L in the mixed gas supply direction to the diameter D in the adsorbent filling area within the container is preferably 50 or less, more preferably 0.1 to 30, even more preferably 0.3 to 20, and even more preferably 0.5 to 10.

[0144] (Adsorbent) The adsorbent includes, for example, at least one selected from silica, activated carbon, alumina, and zeolite. The object to be adsorbed by the adsorbent is not particularly limited, and it is sufficient if it physically adsorbs at least water. Examples of silica include silica gel. Examples of alumina include activated alumina. Examples of zeolite include CHA-type zeolite, GIS-type zeolite, FAU-type zeolite, MWF-type zeolite, LTA-type zeolite, etc. Among these, GIS-type zeolite or FAU-type zeolite is preferred, and GIS-type zeolite is preferred.

[0145] The shape of the adsorbent is not particularly limited, but examples include spherical, cylindrical, elliptical, barrel-shaped, clover-shaped, and ring-shaped. Among these, spherical and cylindrical shapes are preferred.

[0146] The adsorbent may contain a binder. Examples of binders include inorganic binders and organic binders.

[0147] Examples of inorganic binders include inorganic oxides such as alumina, silica, magnesia, zirconia, and titania; clay minerals such as bentonite and kaolin; calcium silicate; and calcium aluminate. Examples of alumina include α-alumina, γ-alumina, boehmite, pseudoboehmite, bayerite, gibbsite, and diaspore. Examples of silica include colloidal silica, water glass, fumed silica, silica sol, wet-process silica, dry-process silica, and natural silica. These inorganic binders may be used individually or in combination.

[0148] The inorganic binder content is preferably 1 to 99% by mass, more preferably 5 to 90% by mass, and even more preferably 8 to 80% by mass, relative to the total amount of adsorbent (100% by mass).

[0149] Examples of organic binders include cellulose, methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, latex, polyvinyl alcohol, vinyl acetate, polyvinyl acetal, vinyl chloride, acrylic, polyamide, urea, melamine, phenolic resin, polyester, polyurethane, polyamide, polybenzimidazole, chloroprene rubber, nitrile rubber, styrene-butadiene rubber, polysulfide, butyl rubber, silicone rubber, acrylic rubber, and urethane rubber. These organic binders may be used individually or in combination.

[0150] The content of the organic binder is preferably 1 to 99% by mass, more preferably 5 to 90% by mass, and even more preferably 8 to 80% by mass, relative to the total amount of the adsorbent (100% by mass).

[0151] The total content of the binder is preferably 1 to 99% by mass, more preferably 5 to 90% by mass, and even more preferably 8 to 80% by mass, based on the total amount of the adsorbent (100% by mass).

[0152] The adsorbent preferably has the ability to adsorb carbon dioxide. This makes it easier for carbon dioxide in the mixed gas to be adsorbed onto the adsorbent, and facilitates the desorption of the adsorbed component. "Having the ability to adsorb carbon dioxide" means that at 1 atm, the adsorption capacity of carbon dioxide is 5 cm³. ３ (STP) g －１ This means that the above is true. The carbon dioxide adsorption capacity is preferably 10 cm at 1 atm. ３ (STP) g －１ That's all. "Gaseous substance" refers to a substance that is a gas at room temperature (25°C) and normal pressure.

[0153] The adsorption selectivity of the adsorbent carbon dioxide / gas B (poorly adsorbed gas) is preferably 5 or higher, more preferably 10 or higher, even more preferably 13 or higher, and even more preferably 15 or higher. The upper limit of the adsorption selectivity is not particularly limited, but for example, it is 100 or less. The adsorption capacity of gas B (poorly adsorbed gas) to the adsorbent is (cm³ ３ (STP) g －１) is a gaseous substance with less adsorption capacity compared to carbon dioxide. The adsorption selectivity for carbon dioxide / poorly adsorbed gas is expressed as the carbon dioxide adsorption capacity / gas B (poorly adsorbed gas) adsorption capacity. The carbon dioxide adsorption capacity or gas B (poorly adsorbed gas) adsorption capacity is the carbon dioxide adsorption capacity (cc) or gas B (poorly adsorbed gas) adsorption capacity (cc) per gram of adsorbent at 25°C. Because it has the selective adsorption properties for carbon dioxide described above, the adsorbent is preferably GIS-type zeolite or FAU-type zeolite, with GIS-type zeolite being preferred.

[0154] The supply amount of the mixed gas per 1 kg of adsorbent is preferably 60 NL / kg or less, more preferably 40 NL / kg or less, and even more preferably 20 NL / kg or less.

[0155] The supply pressure of the mixed gas is preferably 500 kPa or less, more preferably 200 kPa or less, and even more preferably 150 kPa or less. The lower limit of the supply pressure of the mixed gas is not particularly limited, but may be, for example, 2 kPa or more, 10 kPa or more, or 50 kPa or more.

[0156] The present invention will be described more specifically below with reference to examples, but the present invention is not limited to these examples.

[0157] <Explanation of Adsorbents> Alumina: "KHD-24" (product name, Sumitomo Chemical Co., Ltd.) Silica Gel: "Silica Gel, Medium Granules (Blue)" (product name, Fujifilm Wako Pure Chemical Corporation) Zeolite: "Molecular Sieves 13X 1 / 8" (product name, Fujifilm Wako Pure Chemical Corporation) Activated Carbon: "Molcebon 3K-172" (product name, Osaka Gas Chemical Co., Ltd.)

[0158] [Example 1] (1) Pretreatment of adsorbent 1.69 kg of alumina (Sumitomo Chemical Co., Ltd., product name "KHD-24") was placed on a heat-resistant dish and placed in a vacuum oven. The alumina was then heated at 250°C for 3 hours under reduced pressure of 10 Pa or less to remove the adsorbed components.

[0159] (2) Processing of raw material gas The raw material gas was processed using the apparatus shown in Figure 1. 1.69 kg of pre-treated alumina was filled into a SUS pressure vessel 1 (inner diameter: 0.05 m, height: 1.00 m). After that, H ２ N containing O ２ The gas (hereinafter referred to as "raw material gas") is 1 Nm ３ The flow rate is circulated through the pressure vessel 1 at / hr, H ２ N with O excluded ２ A gas (hereinafter referred to as "processed gas") was obtained. At this time, the raw material gas was pressurized to 100 kPaA by the compressor 12. The flow rate of the raw material gas was controlled by the flow controller 11, and the H of the raw material gas was adjusted. ２ The oxygen concentration and pressure were measured using a moisture meter 15 and a pressure gauge 13, respectively. From the measurement values ​​of the moisture meter 15, the H of the raw gas was determined. ２ O was 3.1% by volume. The flow rate of the processed gas and H ２ The oxygen concentration was measured using a flow meter 14 and a moisture meter 16, respectively. The measurement value from the moisture meter 16 indicated the H concentration of the raw gas. ２ When the treatment was carried out until the oxygen concentration reached 2% by volume, the treatment was possible for 12.6 hours from the start of raw gas flow.

[0160] (3) Regeneration of the adsorbent A method for regenerating the adsorbent was carried out using the apparatus shown in Figure 2. 1.69 kg of alumina used in the treatment of the raw material gas was filled into a SUS pressure vessel 2 (inner diameter: 0.05 m, height: 1.00 m). After that, CO ２ CO2 from gas cylinder 21 ２ Gas, CH ４ CH from gas cylinder 22 ４ Gas was supplied, and the mixed gas for adsorbent regeneration (hereinafter simply referred to as "mixed gas") was circulated to line 207 via lines 204 and 206. At this time, by branching from line 201 to line 202, CO ２ A portion of the gas is passed through water tank 3, and humidifying CO2 is added. ２ It manufactures a mixed gas whose composition is H ２ O, CO ２ ,CH ４ This was done so that the composition of the mixed gas was measured using a moisture meter 31 and CO2. ２ Concentration meter 32, CH ４The concentration was measured by a concentration meter 33, and the flow rate was measured by a flow meter 28. Moisture meter 31, CO ２ Concentration meter 32, CH ４ The measured values ​​from the concentration meter 33 and the flow meter 28 were 0.7 vol%, 98.0 vol%, 1.3 vol% and 0.01 Nm³, respectively. ３ The flow controllers 23, 24, and 25 were adjusted to achieve a ratio of 1 / hr, then the three-way valve 92 was switched, the mixed gas was pressurized to 100 kPaA by the compressor 26, valve 82 was opened, and the mixed gas was circulated through lines 204 and 205 to the pressure vessel 2 filled with alumina. The moisture meter 41 measured the H of the mixed gas. ２ When the system was regenerated until the oxygen concentration was reached, the regeneration process was completed 0.34 hours after the start of mixed gas flow.

[0161] (4) Raw material gas treatment - adsorbent regeneration cycle The above-described raw material gas treatment - adsorbent regeneration cycle was repeated 10,000 times. As a result, the regeneration rate was 77% and the pulverization rate was 2.70%.

[0162] [Examples 2-8] Examples 2-8 were carried out in the same manner as Example 1, except that the composition of the mixed gas was changed to that shown in Table 1.

[0163] [Example 9] (1) Pretreatment of adsorbent 1.12 kg of zeolite (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product name "Molecular Sieves 13X 1 / 8") was placed in a heat-resistant dish and placed in a vacuum oven. The dish was then heated at 250°C for 3 hours under reduced pressure of 10 Pa or less to remove the adsorbed components from the alumina.

[0164] (2) Processing of the raw material gas The raw material gas was processed using the apparatus shown in Figure 1. 1.12 kg of the pre-treated zeolite was filled into a SUS pressure vessel 1 (inner diameter: 0.05 m, height: 1.00 m). After that, CH ４ H including ２ The gas (hereinafter referred to as "raw material gas") is 1 Nm ３ The CH is circulated through the pressure vessel 1 at / hr. ４ H excluded ２A gas (hereinafter referred to as "processed gas") was obtained. At this time, the raw material gas was pressurized to 300 kPaA by the compressor 12. The flow rate of the raw material gas was controlled by the flow controller 11, and the CH of the raw material gas was processed. ４ The concentration and pressure are CH, respectively. ４ The concentration was measured using a concentration meter 17 and a pressure gauge 13. ４ Based on the concentration meter readings, the CH of the raw gas ４ It was 60.0 volume percent. The flow rate of the processed gas and CH ４ The concentrations were measured using flowmeter 14 and CH, respectively. ４ The concentration was measured using a concentration meter 18. CH ４ The measurement value from the concentration meter 18 is CH4 of the raw material gas. ４ When the treatment was carried out until the concentration reached 2%, it was possible to perform the treatment for 0.039 hours from the start of raw gas distribution.

[0165] (3) Regeneration of the adsorbent The adsorbent was regenerated using the apparatus shown in Figure 2. 1.12 kg of the zeolite used in the treatment of the raw material gas was filled into a SUS pressure vessel 2 (inner diameter: 0.05 m, height: 1.00 m). After that, CO ２ CO2 from gas cylinder 21 ２ Gas, CH ４ CH from gas cylinder 22 ４ Gas was supplied, and the mixed gas for adsorbent regeneration (hereinafter simply referred to as "mixed gas") was circulated to line 207 via lines 204 and 206. At this time, by branching from line 201 to line 202, CO ２ A portion of the gas is passed through water tank 3, and humidifying CO2 is added. ２ It manufactures a mixed gas whose composition is H ２ O, CO ２ ,CH ４ This was done so that the composition of the mixed gas was measured using a moisture meter 31 and CO2. ２ Concentration meter 32, CH ４ The concentration was measured by a concentration meter 33, and the flow rate was measured by a flow meter 28. Moisture meter 31, CO ２ Concentration meter 32, CH ４ The measured values ​​from the concentration meter 33 and the flow meter 28 were 0.7 vol%, 98.0 vol%, 1.3 vol% and 0.01 Nm³, respectively. ３The flow controllers 23, 24, and 25 were adjusted to achieve a flow rate of / hr, and then the three-way valve 92 was switched to pressurize the mixed gas to 100 kPaA using the compressor 26. Valve 82 was then opened, and the mixed gas was circulated through lines 204 and 205 to the pressure vessel 2 filled with zeolite. ４ The measurement value from the concentration meter 42 is CH4 of the mixed gas. ４ When the mixture was regenerated until the desired concentration was reached, mixing was completed 1.17 hours after the start of gas circulation.

[0166] (4) Raw material gas treatment process - adsorbent regeneration cycle) The above raw material gas treatment - adsorbent regeneration cycle was repeated 10,000 times. As a result, the regeneration rate was 99% and the pulverization rate was 3.75%.

[0167] [Examples 10-16] Examples 10-16 were carried out in the same manner as in Example 9, except that the composition of the mixed gas was changed to that shown in Table 1.

[0168] [Example 17] (1) Pretreatment of adsorbent 1.69 kg of alumina (Sumitomo Chemical Co., Ltd., product name "KHD-24") was placed on a heat-resistant dish and placed in a vacuum oven. The alumina was then heated at 250°C for 3 hours under reduced pressure of 10 Pa or less to remove the adsorbed components.

[0169] (2) Processing of raw material gas The raw material gas was processed using the apparatus shown in Figure 1. 1.69 kg of pre-treated alumina was filled into a SUS pressure vessel 1 (inner diameter: 0.05 m, height: 1.00 m). After that, H ２ N containing O ２ The gas (hereinafter referred to as "raw material gas") is 1 Nm ３ The flow rate is circulated through the pressure vessel 1 at / hr, H ２ N with O excluded ２ A gas (hereinafter referred to as "processed gas") was obtained. At this time, the raw material gas was pressurized to 100 kPaA by the compressor 12. The flow rate of the raw material gas was controlled by the flow controller 11, and the H of the raw material gas was adjusted. ２ The oxygen concentration and pressure were measured using a moisture meter 15 and a pressure gauge 13, respectively. From the measurement values ​​of the moisture meter 15, the H of the raw gas was determined. ２ O was 3.1% by volume. The flow rate of the processed gas and H ２The oxygen concentration was measured using a flow meter 14 and a moisture meter 16, respectively. The measurement value from the moisture meter 16 indicated the H concentration of the raw gas. ２ When the treatment was carried out until the oxygen concentration reached 2% by volume, the treatment was possible for 12.6 hours from the start of raw gas flow.

[0170] (3) Regeneration of the adsorbent The adsorbent was regenerated using the apparatus shown in Figure 6. The raw material gas used to produce the mixed gas for regenerating the adsorbent was a gas having a composition of 3.1% by volume, 38.8% by volume, and 58.1% by volume of water, carbon dioxide, and methane, respectively. In addition, as in this example, the adsorbent may also be regenerated using a mixed gas in which the gas not included in the raw material gas in the "(2) Treatment of raw material gas" step (methane) is gas B.

[0171] 1.69 kg of alumina used in the processing of the raw gas was packed into a SUS pressure vessel 2 (inner diameter: 0.05 m, height: 1.00 m). Zeolite (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product name "Molecular Sieves 13X 1 / 8") 1020-1a and 1020-1b were packed as adsorbents, and alumina (manufactured by Sumitomo Chemical Co., Ltd., product name "KHD-24") 1020-2a and 1020-2b were packed as dehumidifiers, at a rate of 0.87 kg and 0.13 kg respectively, into adsorption towers 1005a and 1005b. At this time, the adsorption layer (the cylindrical part filled with adsorbents and dehumidifiers) was packed to a volume percentage of 68%. Before the following operation 1, adsorption towers 1005a and 1005b were reduced to 50 Pa and heated to 200°C to remove moisture contained in the adsorbents.

[0172] (Operation 1) Adsorption tower 1005a: With all automatic valves AV for the adsorption process closed, automatic valves AV1004a and AV1006a were opened, and the raw material gas was supplied to the adsorption tower 1005a at 300 kPa (absolute pressure) by the pressurizer 1003. Methane was stored in the product gas B storage section. After 2 minutes, automatic valves AV1004a and AV1006a were closed. The gas B (methane) that flowed out of the product gas B storage section 1008 between the opening and closing of automatic valves AV1004a and AV1006a was entirely recovered in a gas bag (not shown).

[0173] Adsorption tower 1005b: From a state where all automatic valves AV for the desorption process were closed, automatic valve AV 1013b was opened, and the adsorption tower 1005b was depressurized by the depressurization device 1015.

[0174] If operation 2 is skipped and operation 3 is initiated, the adsorption tower 1005b is depressurized, and after confirming that the pressure indicated by the pressure gauge 1022b located at the top of the adsorption tower reaches 6 kPa (absolute pressure), the automatic valve AV1013b is closed. Between the opening and closing of the automatic valve AV1013b, the gas 2 (product mixed gas) that has flowed out of the adsorption tower 1005b is supplied to the adsorbent regeneration device.

[0175] (Operation 2) Adsorption tower 1005a: After the pressure drop process operation 1, automatic valves AV1004a and AV1006a were closed, and automatic valve AV1009a was opened to allow the gas from adsorption tower 1005a to flow into the raw material gas tank 1002. After 10 seconds, automatic valve AV1009a was closed.

[0176] Adsorption tower 1005b: The automatic valve for the desorption process maintained the state of operation 1. After confirming that the pressure indicated by the pressure gauge 1022b located at the top of the adsorption tower reached 6 kPa (absolute pressure), the automatic valve AV1013b was closed. From the time the automatic valve AV1013b was opened until it was closed, the gas 2 (product mixed gas) that flowed out of the adsorption tower 1005b was supplied to the adsorbent regeneration device.

[0177] (Operation 3) Adsorption towers 1005a and 1005b: After closing automatic valves AV1009a and AV1013b in inflow process operation 2, automatic valve AV1012 was opened to allow the gas from adsorption tower 1005a to flow into adsorption tower 1005b. After 10 seconds, automatic valve AV1012 was closed.

[0178] (Operation 4) Adsorption tower 1005a: After closing the automatic valve AV1012 in the desorption process operation 3, the automatic valve AV1013a was opened and the adsorption tower 1005a was depressurized by the depressurization device 1015.

[0179] Adsorption tower 1005b: After closing automatic valve AV1012 in the repressurization process operation 3, automatic valve AV1017b was opened, and gas was introduced from the product gas B containment section 1008. After confirming that the pressures indicated by pressure gauges 1021b and 1022b located above and below the adsorption tower 1005b reached 300 kPa (absolute pressure), automatic valve AV1017b was closed.

[0180] (Operation 5) Adsorption tower 1005a: The automatic valve for the desorption process maintained the state of Operation 4. If Operation 6 described later is skipped and Operation 7 is initiated, after depressurizing the adsorption tower 5a, the automatic valve AV1013a was closed after confirming that the pressure indicated by the pressure gauge 1022a located at the top of the adsorption tower reached 6 kPa (absolute pressure). From the time the automatic valve AV1013a is opened until it is closed, the gas 2 (product mixed gas) that has flowed out of the adsorption tower 1005a is supplied to the adsorbent regeneration device.

[0181] Adsorption tower 1005b: After closing the adsorption process automatic valve AV1017b, automatic valves AV1004b and AV1006b were opened, and the raw material gas was supplied to the adsorption tower 1005b at 300 kPa (absolute pressure) by the pressurizing device 1003. After 2 minutes, automatic valves AV1004b and AV1006b were closed. From the time automatic valves AV1004b and AV1006b were opened until they were closed, all of the gas 1 (methane) that had leaked out from the product gas B containment section was recovered in a gas bag (not shown).

[0182] (Operation 6) Adsorption tower 1005a: The automatic valve for the desorption process maintained the state of Operation 5. After confirming that the pressure indicated by the pressure gauge 1022a located at the top of the adsorption tower reached 6 kPa (absolute pressure), the automatic valve AV1013a was closed. From the time the automatic valve AV1013a was opened until it was closed, the gas 2 (product mixed gas) that flowed out of the adsorption tower 1005a was supplied to the adsorbent regeneration device.

[0183] Adsorption tower 1005b: After closing automatic valves AV1004b and AV1006b in the pressure drop process operation 5, automatic valve AV1009b was opened to allow the gas from adsorption tower 1005b to flow into the raw material gas tank 2. After 10 seconds, automatic valve AV1009b was closed.

[0184] (Operation 7) Adsorption towers 5a and 5b: After closing automatic valves AV1013a and AV1009b in inflow process operation 6, automatic valve AV1012 was opened to allow the gas from adsorption tower 1005b to flow into adsorption tower 1005a. After 10 seconds, automatic valve AV1012 was closed.

[0185] (Operation 8) Adsorption tower 1005a: After closing the automatic valve AV1012 in the repressurization process operation 7, the automatic valve AV1017a was opened and gas was allowed to flow in from the product gas B containment section 1008. After confirming that the pressure gauges 1021a located above and below the adsorption tower 1005a and the pressure indicated by the pressure gauge 1021a reached 300 kPa (absolute pressure), the automatic valve AV1017a was closed.

[0186] Adsorption tower 1005b: After closing automatic valve AV1012 in the desorption process operation 7, automatic valve AV1013b was opened, and the adsorption tower 1005b was depressurized by the depressurization device 1015.

[0187] (Operation 9) Adsorption tower 1005a: After closing the automatic valve AV1017a for the adsorption process, automatic valves AV1004a and AV1006a were opened, and the raw material gas was supplied to the adsorption tower 1005a at 300 kPa (absolute pressure) by the pressurizing device 1003. After 2 minutes, automatic valves AV1004a and AV1006a were closed. From the time automatic valves AV1004a and AV1006a were opened until they were closed, all of the gas 1 (methane) that had leaked out from the product gas B containment section was recovered in a gas bag (not shown). Adsorption tower 1005b: The automatic valves for the desorption process maintained the state of Operation 8. After confirming that the pressure indicated by the pressure gauge 1022b located at the top of the adsorption tower reached 6 kPa (absolute pressure), automatic valve AV1013b was closed. From the time the automatic valve AV1013b is opened until it is closed, the gas 2 (product mixed gas) that has leaked out of the adsorption tower 1005b is supplied to the adsorbent regeneration device.

[0188] After performing operations 1, 2, 3, 4, 5, 6, 7, 8, and 9 once, operations 2, 3, 4, 5, 6, 7, 8, and 9 were repeated 100 times.

[0189] All of the obtained gas 1 (methane) was recovered in its entirety. The methane purity of the obtained gas 1 was 98.1%. The obtained gas 2 (product mixed gas) is supplied to the adsorbent regenerator via the product mixed gas storage unit 1025. The composition of the product mixed gas was measured by a moisture meter 51, a CO ２ concentration meter 52, and a CH ４ concentration meter 53. The measured values of the moisture meter 51, the CO ２ concentration meter 52, and the CH ４ concentration meter 53 were 0.8% by volume, 98.5% by volume, and 0.7% by volume, respectively. The set value at the flow controller 75 was 0.01 Nm ３ / hr. After repeating operations 2, 3, 4, 5, 6, 7, 8, and 9 in the mixed gas production apparatus 5 times, the three-way valve 72 was switched, the valve 74 was released, and the mixed gas was circulated through the pressure-resistant container 71 filled with alumina via lines 302 and 304. When regeneration was carried out until the measured value of the moisture meter 61 became the H ２ O concentration of the mixed gas, regeneration was completed 0.34 hr after the start of mixed gas circulation.

[0190] (4) Treatment of the raw material gas - Regeneration cycle of the adsorbent The cycle operation of repeatedly carrying out the above-described treatment of the raw material gas - regeneration of the adsorbent was repeated 10,000 times. As a result, the regeneration rate was 74% and the pulverization rate was 2.55%.

[0191] [Comparative Examples 1 - 2] Comparative Examples 1 - 2 were carried out in the same manner as in Example 1, except that the composition of the mixed gas was changed to those shown in Table 1.

[0192] [Comparative Example 3] Comparative Example 3 was carried out in the same manner as in Example 9, except that the composition of the mixed gas was changed to those shown in Table 1.

[0193] (Definition of the regeneration rate) Using the adsorbent after the pretreatment step, when the treatment step was carried out, the treatment time was t Ｉｎｉ [hr], and when the treatment step - the 10,000th cycle treatment step of the drying step was carried out, the treatment time was t Ｆｉｎ [hr], then (regeneration rate) = t Ｆｉｎ / t Ｉｎｉ was defined.

[0194] (Definition of the pulverization rate) The weight of the adsorbent after the pretreatment step was W Ｉｎｉ[kg], treatment process - for the adsorbent after the 10,000th cycle of the drying process was carried out, after sieving with a stainless - steel sieve (sieve diameter: 2.80 mm), the weight of the adsorbent on the sieve after performing the same operations as the pretreatment process on the adsorbent on the sieve was W Ｆｉｎ [kg], and (powdering rate) = 1 - W Ｆｉｎ / W Ｉｎｉ was defined as such.

[0195] (Calculation of volume %) In this embodiment, for CO ２ , CH ４ , H ２ O, the concentrations were respectively C_CO ２ , C_CH ４ , C_H ２ O (unit: mol / mol), and the volume % was calculated as follows. CO ２ Volume % = C_CO ２ / (C_CO ２ + C_CH ４ + C_H ２ O) CH ４ Volume % = C_CH ４ / (C_CO ２ + C_CH ４ + C_H ２ O) H ２ OVolume % = C_H ２ O / (C_CO ２ + C_CH ４ + C_H ２ O)

[0196]

[0197] According to the drying method of this embodiment, while suppressing the powdering rate of the adsorbent, the adsorbent can be repeatedly dried.

[0198] This application claims priority from Japanese Patent Application No. 2024 - 230924 filed on December 26, 2024, and the entire description of that application is regarded as part of the disclosure of this application and is incorporated herein by reference.

[0199] R...raw material gas, 1, 2...pressure vessel, 3...water tank, 11, 23, 24, 25...flow controller, 12...compressor, 13...pressure gauge, 14...flow meter, 15, 16, 31, 41...moisture meter, 32, 42...CO ２ Concentration meter, 17, 18, 33, 43...CH ４ Concentration meter, 21...CO ２ Gas cylinder, 22...CH ４ Gas cylinder, 26... Compressor, 27... Pressure gauge, 28... Flow meter, 81, 82... Valves, 91, 92... Three-way valve, 201... CO ２ Line, 202...CO ２ Humidification line, 203...CH ４ Line, 204...Regeneration mixed gas line, 205...Regeneration line, 206...Bypass line, 207...Vent line, 1001...Raw material gas supply line, 1002...Raw material gas tank, 1003...Pressurization device, 1005a, 1005b...Adsorption tower, 1007...Product gas B recovery line, 1008...Product gas B storage section, 1010...Depressurization gas line, 1011...Inflow gas line, 1014...Product mixed gas recovery line, 1015...Depressurization device, 1016...Repressurization gas line, 1025...Product mixed gas storage section, 100...Gas separation device, 200...Fermentation tank, 400...Desulfurization tower, 500...Siloxane removal device, 600...Oxygen removal device, 700...Cooling device

Claims

1. A mixed gas comprising 0.1% by volume or more and 3.0% by volume or less of water vapor, and 97% by volume or more of a gas A different from water vapor, wherein the gas A has a Henry constant of 2000 atm / mol fraction or less for water at 0°C.

2. The mixed gas according to claim 1, wherein gas A is carbon dioxide.

3. The mixed gas according to claim 1, wherein the mixed gas further comprises at least one selected from methane, ethane, nitrogen, carbon monoxide, hydrogen, argon, and dimethyl ether.

4. The mixed gas according to claim 1, wherein the concentration of gas B (excluding water vapor), whose Henry constant for water at 0°C is greater than 2000 atm / mol fraction, is 0% by volume or more and 2.0% by volume or less.

5. A method for regenerating an adsorbent, comprising passing a mixed gas according to any one of claims 1 to 4 through a container filled with an adsorbent containing at least one selected from silica, activated carbon, alumina, and zeolite, to desorb components adsorbed on the adsorbent from the adsorbent.

6. The method for regenerating an adsorbent according to claim 5, wherein the adsorbent has the ability to adsorb carbon dioxide.

7. The method for regenerating an adsorbent according to claim 5, wherein the adsorbed component is water.

8. A method for producing a mixed gas containing 0.1% to 3.0% by volume of water vapor and 97% or more by volume of gas A, a gas different from water vapor whose Henry constant for water at 0°C is 2000 atm / mol fraction or less, comprising: an adsorption step in which a raw material gas containing water vapor, gas A, and gas B (excluding water vapor) whose Henry constant for water at 0°C is greater than 2000 atm / mol fraction is supplied to an adsorption tower having a desiccant and an adsorbent, and the water vapor is adsorbed by the desiccant and gas A is adsorbed by the adsorbent, thereby separating gas B from the raw material gas; and a desorption step in which the pressure inside the adsorption tower is reduced, wherein in the adsorption step, the raw material gas is brought into contact with the desiccant and the adsorbent in that order inside the adsorption tower, and in the desorption step, the pressure inside the adsorption tower is reduced from the inlet side of the raw material gas, thereby discharging the mixed gas outside the adsorption tower in a countercurrent direction with respect to the flow direction of the raw material gas in the adsorption step.

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