How to stop the separation device

Abstract

The present invention provides a method for stopping a separation device that is provided with a separation membrane, the method being capable of preventing damage to the separation membrane.　A method for stopping a separation device, which is provided with a separation membrane, according to one embodiment of the present invention stops the separation device after a dehydration step by means of the separation membrane. This method comprises a process in which the separation membrane is placed in an environment A, wherein a water vapor partial pressure P(H2O) and a saturated water vapor pressure Psat(H2O) satisfy the relational expression P(H2O) / Psat(H2O) ≥ 0.001 and the temperature is 100°C or higher, and the temperature of the environment A is decreased.

Description

[Technical Field]

[0001] The present invention relates to a method for stopping a separation device. [Background technology]

[0002] A membrane separation method is known that uses a separation membrane to separate a specific substance from a mixture. For example, a separation method using a zeolite membrane has been proposed (see Non-Patent Literature 1). In separation apparatuses equipped with a separation membrane, the membrane may be heated under pressure to ensure it performs its intended function. In such separation apparatuses, preventing damage to the separation membrane due to cooling during shutdown is required. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Development of a membrane-assisted membrane reactor, Mitsui Engineering & Shipbuilding Technical Report, February 2003, No. 178, 115-120. [Overview of the project] [Problems that the invention aims to solve]

[0004] The main object of the present invention is to provide a method for stopping a separation apparatus equipped with a separation membrane, which can prevent damage to the separation membrane. [Means for solving the problem]

[0005] [1] A method for stopping a separation apparatus according to an embodiment of the present invention is a method for stopping a separation apparatus having a separation membrane after a dewatering step by a separation membrane, wherein the partial pressure of water vapor P(H2O) and the saturated water vapor pressure P sat (H2O) and [P(H2O) / P sat The method includes placing a separation membrane in environment A, where the relationship [(H2O)≧0.001] is satisfied and the temperature is 100°C or higher, and then lowering the temperature of environment A. [2] The method for stopping the separation apparatus in [1] above may include reducing the pressure of environment A. [3] The method for stopping the separation apparatus in [2] above may include reducing the pressure of environment A and then lowering the temperature. [4] In the method for stopping the separation apparatus described in any of [1] to [3] above, the temperature reduction may be performed by adjusting the output of the temperature control means. [5] The method for stopping the separation apparatus described in any of [2] to [4] above includes keeping the temperature of environment A approximately constant during the depressurization. [6] The method for stopping the separation apparatus described in any of [2] to [5] above may include performing a depressurization operation in stages. [7] The method for stopping the separation apparatus described in any of [1] to [6] above may include keeping the total pressure of environment A approximately constant during the temperature reduction. [8] In the method for stopping the separation apparatus described in any of [1] to [7] above, the temperature of environment A may be less than 400°C. [9] In the method for stopping the separation apparatus described in any of [1] to [8] above, in environment A, the water vapor partial pressure P(H2O) and the saturated water vapor pressure P sat (H2O) and [1>P(H2O) / P sat The relationship (H2O) may also be satisfied.

[10] In the method for stopping the separation apparatus described in any of [2] to [9] above, the depressurization operation may be stopped when the total pressure of environment A becomes atmospheric pressure + 10 kPa.

[11] In the method for stopping the separation apparatus described in any of [1] to

[10] above, the separation membrane may be a zeolite membrane.

[12] In the method for stopping the separation apparatus described in

[11] above, the zeolite membrane may be composed of LTA-type zeolite. [Effects of the Invention]

[0006] According to embodiments of the present invention, a method for stopping a separation apparatus equipped with a separation membrane can be provided, which can prevent damage to the separation membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] [Figure 1] FIG. 1 is a schematic configuration diagram of a separation membrane composite used in a method for shutting down a separation device according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic configuration diagram of the separation membrane and a substrate in FIG. 1. [Figure 3A] FIG. 3A is a graph illustrating a method for shutting down a separation device according to one embodiment of the present invention. [Figure 3B] FIG. 3B is a graph illustrating a method for shutting down a separation device according to one embodiment of the present invention. [Figure 4] FIG. 4 is a graph illustrating a method for shutting down a separation device according to one embodiment of the present invention. [Figure 5] FIG. 5 is a graph illustrating a method for shutting down a separation device according to one embodiment of the present invention. [Figure 6] FIG. 6 is a graph illustrating a method for shutting down a separation device according to one embodiment of the present invention. [Figure 7] FIG. 7 is a schematic configuration diagram of one modification of the separation membrane composite. [Figure 8] FIG. 8 is a schematic cross-sectional view of the separation membrane composite in FIG. 7. [Figure 9] FIG. 9 is a schematic configuration diagram of another modification of the separation membrane composite. [Figure 10] FIG. 10 is a schematic diagram for illustrating an operation method of a separation device according to one embodiment of the present invention. DESCRIPTION OF EMBODIMENTS

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. In addition, for clearer explanation, the drawings may schematically represent the width, thickness, shape and the like of each part compared to the actual embodiments, but this is merely an example and does not limit the interpretation of the present invention.

[0009] A. Method for shutting down separation device Figure 1 is a schematic configuration diagram of a separation membrane composite used in the method for shutting down a separation device according to one embodiment of the present invention; Figure 2 is a schematic configuration diagram of the separation membrane and the base material in Figure 1.

[0010] The method for shutting down a separation device according to one embodiment of the present invention is a method for shutting down a separation device 1 including a separation membrane 2. In one embodiment, the separation membrane 2 constitutes a separation membrane composite 10. The separation membrane composite 10 includes the separation membrane 2 and a base material 3 disposed on one side of the separation membrane 2. The separation device 1 includes a first flow path 21 and a second flow path 22. The first flow path 21 is located on the separation membrane 2 side of the separation membrane composite 10. The second flow path 22 is located on the base material 3 side of the separation membrane composite 10. In one embodiment, the first flow path and the second flow path are separated by the separation membrane. In one embodiment, the first flow path may be a flow path through which a mixed gas to be separated in a dehydration step flows. In one embodiment, the second flow path may be a flow path through which a gas that has permeated through the separation membrane flows.

[0011] The method for shutting down the separation device is performed after a dehydration step performed by the separation membrane 2. In the dehydration step, dehydration of a water-containing fluid to be treated is performed by supplying the water-containing fluid (for example, a water-containing gas containing an organic compound) to the first flow path and separating water with the separation membrane. The water-containing fluid may be supplied under pressure. Further, the separation membrane may be heated to a predetermined temperature in order to exhibit separation performance of the separation membrane.

[0012] The method for shutting down the separation device includes placing the separation membrane in an environment where a water vapor partial pressure P(H2O) is within a predetermined range, and lowering the temperature of the environment. The method for shutting down the separation device may be a method of lowering the temperature of the separation membrane heated in the dehydration step to a predetermined temperature (for example, 100°C). In the present specification, the water vapor partial pressure P(H2O), saturated water vapor pressure P sat (H2O), when referring to pressures such as total pressure, the pressure may be the pressure of the first flow path (for example, the flow path inside the separation membrane) (for example, the pressure on the outlet side of the flow path), and in the separation membrane composite 10 shown in Figure 1, the pressure may be the pressure of the first flow path 21.

[0013] Specifically, an environment where the partial pressure of water vapor P(H2O) falls within a predetermined range refers to an environment where the partial pressure of water vapor P(H2O) and the saturated water vapor pressure P sat (H2O) satisfy the relationship [P(H2O) / P sat (H2O)≧0.001] and the temperature is 100° C. or higher. In the present specification, such an environment is referred to as "Environment A" for convenience. Environment A may be in (for example, at the outlet of) the first flow path.

[0014] The temperature of the Environment A is preferably lower than 400° C., more preferably 200° C. or lower. With such a range, damage to the separation membrane (for example, damage caused by dissolution of the separation membrane) can be prevented.

[0015] FIG. 3A and FIG. 3B are graphs illustrating a method for stopping a separation device according to one embodiment of the present invention. In FIG. 3A and FIG. 3B, the vertical axis represents the total pressure of the environment where the separation membrane is placed, and the horizontal axis represents the temperature. FIG. 3B is an enlarged view of FIG. 3A in the vertical axis range from 0 kPa to 30 kPa for the purpose of making the line of P(H2O) / P sat (H2O)=0.001 easier to see. Further, in FIG. 3A and FIG. 3B, areas satisfying the conditions of Environment A are colored. Although FIG. 3A and FIG. 3B show an example where the supply water vapor concentration is 25 mol%, the supply water vapor concentration is not limited thereto and can be any appropriate value. The end point of the preceding dehydration step is taken as the starting point S of the stopping method for the separation device described above. In the embodiment shown in FIG. 3, the temperature at the starting point S is 150° C., and the total pressure is 1000 kPaA. In the embodiment of the present invention, as indicated by the arrow in FIG. 3A, [P(H2O) / P satThe separation membrane is cooled under conditions that satisfy the relationship [(H2O)≧0.001] and where the temperature is 100°C or higher. By cooling the separation membrane in this way, drying of the separation membrane can be suppressed and various types of damage, such as cracks, can be prevented. In one embodiment, the cooling of environment A is performed by adjusting the output of the temperature control means. Preferably, the cooling of environment A is performed by supplying a water-containing gas (e.g., water-containing air) whose temperature has been controlled by the temperature control means to the first flow path.

[0016] In the above environment A, P(H2O) / P sat The (H2O) content is preferably 0.005 or higher, and more preferably 0.05 or higher. Within this range, the above effects become significant. Furthermore, the measuring instruments can be simplified. In addition, general-purpose parts can be used for the measuring instruments, which reduces costs.

[0017] Furthermore, in the above environment A, P(H2O) / P sat The (H2O) value is preferably less than 1 (for example, below the dashed line in Figure 3A), more preferably 0.95 or less, and even more preferably 0.9 or less. Within this range, the effects of the present invention can be reliably obtained. By setting environment A to such a state, damage to the separation membrane by droplets (for example, damage caused by the dissolution of the separation membrane) can be prevented.

[0018] In one embodiment, as shown in Figure 3A, the method for stopping the separation apparatus includes reducing the pressure of environment A. In one embodiment, the pressurized environment in the preceding dehydration process (e.g., an environment with a pressure of 0.1 MPaG to 20 MPaG) is reduced in the method for stopping the separation apparatus. This reduction in pressure may be an operation that reduces the amount of moisture in environment A.

[0019] Figures 4 and 5 are graphs illustrating a method for stopping a separation apparatus according to one embodiment of the present invention. In one embodiment, the environment A is depressurized and then cooled. Preferably, as shown in Figures 4 and 5, at the starting point S of the stopping method, the environment A is first depressurized. Depressurization may be accompanied by cooling of the environment A. For example, a natural decrease in temperature due to depressurization is permitted. In one embodiment, the temperature of the environment A is kept approximately constant (for example, within a temperature change of 5°C) during depressurization. According to this embodiment, damage to the separation membrane due to drying can be prevented, and the accuracy of preventing damage to the separation membrane due to droplets can also be significantly increased.

[0020] In one embodiment, the environment A is cooled down and then depressurized (Figure 6). In one embodiment, at the starting point S of the stopping method, the environment A is first cooled down. In one embodiment, during cooling, the pressure of environment A is kept approximately constant (for example, a pressure change of 50 kPa or less). According to this embodiment, damage to the separation membrane due to drying can be prevented, and the accuracy of preventing damage to the separation membrane due to droplets can also be significantly increased.

[0021] Preferably, even under reduced pressure, a pressure greater than atmospheric pressure is maintained in environment A. This prevents damage to the separation membrane due to drying.

[0022] In one embodiment, when the pressure is reduced, the temperature of environment A is reduced by adjusting the output of the temperature control means. For example, a heating device is used as the temperature control means to mitigate the natural decrease in temperature during pressure reduction, or to keep the temperature change approximately constant. Examples of heating devices include reactors involved in chemical reactions, heaters, heat exchangers, etc. Alternatively, a heating device used in the preceding dehydration process may be repurposed as the temperature control means.

[0023] In one embodiment, when reducing the pressure of environment A, the depressurization operation is performed in stages (Figures 4 and 6). In this specification, "the depressurization operation is performed in stages" means that, between the start and end of the method for stopping the separation apparatus, there are two or more periods (preferably five or more, more preferably 20 or more) during which the pressure (total pressure) of environment A remains approximately constant (for example, within a pressure change of 50 kPa). The upper limit of the number of periods during which the pressure (total pressure) of environment A remains approximately constant is, for example, 150 times or less. For example, when reducing the pressure from 3 MPa to 0.1 MPa, the depressurization operation is performed in 58 stages, with a period during which the pressure (total pressure) of environment A remains approximately constant after every 50 kPa reduction in pressure. By performing the depressurization operation in stages, damage to the separation membrane can be prevented. In one embodiment, the number of periods during which the pressure (total pressure) of environment A remains approximately constant is 10 times or less.

[0024] In one embodiment, the method for stopping the separation device includes keeping the total pressure of environment A approximately constant (for example, within a pressure change of 50 kPa) when the temperature of environment A is reduced (Figures 4 to 6).

[0025] Preferably, in the method for stopping the separation apparatus, the depressurization operation is stopped when the total pressure of environment A becomes atmospheric pressure + 10 kPa (preferably + 50 kPa). After the total pressure of environment A becomes atmospheric pressure + 10 kPa (preferably + 50 kPa), the temperature of the separation membrane is kept below 100°C. In this way, the separation apparatus can be stopped while preventing damage to the separation membrane. In another embodiment, the depressurization operation is stopped when the total pressure of environment A becomes atmospheric pressure.

[0026] B. Separation device B-1. Separation membrane complex As shown in Figure 1, the separation device 1 typically comprises a separation membrane complex 10 including a substrate 3 and a separation membrane 2. Although not shown, the separation membrane complex 10 is used in any suitable case. Typically, the separation membrane complex 10 extends in the same direction as the first flow path. The length of the separation membrane complex 10 can be arbitrarily and appropriately adjusted.

[0027] B-1-1. Base material The substrate 3 supports the separation membrane 2. In one embodiment, the substrate 3 is a porous substrate. The porous substrate has, for example, a monolithic structure and comprises a three-dimensional network-like continuous skeleton and communicating pores defined by the skeleton.

[0028] The porous substrate can be composed of any suitable material. Typical materials for the porous substrate include ceramic sintered bodies. Examples of ceramic sintered bodies include alumina, silica, mullite, zirconia, titania, yttria, silicon nitride, silicon carbide, and cordierite. Ceramic sintered bodies can be used alone or in combination. Among ceramic sintered bodies, alumina is preferred.

[0029] The porous substrate may contain an inorganic binder. Examples of inorganic binders include titania, mullite, easily sintered alumina, silica, glass frit, clay minerals, and easily sintered cordierite. The inorganic binders can be used alone or in combination.

[0030] The porous substrate may consist of a single layer or have a multilayer structure in which multiple layers are stacked. In one embodiment, the porous substrate has a multilayer structure having multiple layers with different pore sizes, as shown in Figure 2. In this case, it is preferable that the pore size is smaller closer to the separation membrane 2.

[0031] The average pore size of the porous substrate is, for example, 0.01 μm to 70 μm, preferably 0.05 μm to 25 μm. The average pore size of the porous substrate on the separation membrane side is 0.01 μm to 1 μm, preferably 0.05 μm to 0.5 μm. Regarding the distribution of pore size throughout the porous substrate, including the surface and interior, D5 is, for example, 0.01 μm to 50 μm, D50 is, for example, 0.05 μm to 70 μm, and D95 ​​is, for example, 0.1 μm to 2000 μm. The porosity of the porous substrate on the separation membrane side is, for example, 25% to 50%. The average pore size of the porous substrate can be measured, for example, by a mercury porosimeter, palm porometer, or nanopalm porometer.

[0032] As shown in Figure 1, the base material 3 typically separates the first flow path 21 and the second flow path 22 described above. The base material 3 can take any suitable shape. Examples of the base material 3's shape include cylindrical, honeycomb, and flat plate shapes. In one embodiment, the base material 3 is a cylindrical base material 3a. Examples of cross-sectional shapes in the direction perpendicular to the longitudinal direction of the cylindrical base material 3a include triangles, quadrilaterals, pentagons, polygons with hexagons or more, circles, and ellipses, with a circle being preferred. The outer diameter and length of the cylindrical base material can be appropriately set depending on the purpose.

[0033] In this embodiment, the internal space of the cylindrical substrate 3a (the space defined by the inner circumferential surface of the cylindrical substrate) includes either the first flow path 21 or the second flow path 22, and the external space of the cylindrical substrate 3a (the space outside the outer circumferential surface of the cylindrical substrate) includes either the first flow path 21 or the second flow path 22. In the illustrated example, the internal space of the cylindrical substrate 3a includes the first flow path 21, and the external space of the cylindrical substrate 3a includes the second flow path 22.

[0034] In another embodiment, as shown in Figures 7 and 8, the base material 3 is a honeycomb base material 3b. The honeycomb base material 3b has partition walls 33 that define a plurality of cells 34. The cells 34 are formed in a cylindrical shape so as to penetrate the honeycomb base material 3b in the longitudinal direction.

[0035] Cell 34 extends in the longitudinal direction (axial direction) of the honeycomb substrate 3b from the first end face E1 (inlet end face) to the second end face E2 (outlet end face) of the honeycomb substrate 3b (Figure 8 (See reference). The cell 34 has any suitable shape in a cross-section perpendicular to the longitudinal direction of the honeycomb substrate 3b. Examples of cell cross-sectional shapes include triangles, quadrilaterals, pentagons, polygons with hexagons or more, circles, and ellipses. The cross-sectional shapes and sizes of the cells may all be the same, or at least some may differ. Among such cell cross-sectional shapes, a circle is preferred.

[0036] The distance between the central axes of multiple cells 34 is, for example, 0.3 mm to 20 mm. The cell density (i.e., the number of cells 34 per unit area) in a cross-section perpendicular to the longitudinal direction of the honeycomb substrate can be appropriately set depending on the purpose. The cell density is, for example, 0.5 cells / cm 2 ~320 cells / cm 2 This is possible. If the cell density is within this range, sufficient strength and effective GSA (geometric surface area) of the honeycomb substrate can be ensured.

[0037] The honeycomb substrate 3b has any suitable shape (overall shape). Examples of honeycomb substrate shapes include a cylindrical shape with a circular base, an elliptical columnar shape with an elliptical base, a prismatic columnar shape with a polygonal base, and a columnar shape with an irregular base. The honeycomb substrate 3b in the illustrated example has a cylindrical shape. The outer diameter and length of the honeycomb substrate can be appropriately set depending on the purpose.

[0038] In this embodiment, the internal space of each of the multiple cells 34 (the space defined by the inner circumferential surface of the cell) includes either the first flow path 21 or the second flow path 22, and the external space of the honeycomb substrate 3b (the space outside the outer circumferential surface of the honeycomb substrate) includes the other of the first flow path 21 or the second flow path 22. In the illustrated example, the internal space of the cell 34 includes the first flow path 21, and the external space of the honeycomb substrate 3b includes the second flow path 22.

[0039] B-1-2. Separation membrane The separation membrane 2 is typically provided directly on the surface of the substrate 3. The separation membrane 2 may face the first channel 21 (see Figures 1 and 8) or the second channel 22 (see Figure 9). When the separation membrane faces the first channel, the substance to be separated contained in the mixture passing through the first channel comes into direct contact with the separation membrane. Therefore, the separation membrane can efficiently separate the substance to be separated. When the separation membrane faces the second channel, the substance to be separated contained in the mixture passing through the first channel permeates the substrate and reaches the separation membrane. In this way as well, the separation membrane can separate the substance to be separated.

[0040] In one embodiment, the separation membrane 2 faces the first channel 21. In Figure 1, the substrate 3 is a cylindrical substrate 3a, and the separation membrane 2 is formed on the inner surface of the cylindrical substrate 3a. In the illustrated example, the first channel 21 is formed in the portion of the cross-section of the separation membrane composite 10 where the separation membrane 2 is not formed (typically the central part). Furthermore, in Figure 8, the substrate 3 is a honeycomb-shaped substrate 3b, and the separation membrane 2 is formed on the inner surface of each of the multiple cells 34. The first channel 21 is formed in the portion of the cross-section of the cell 34 where the separation membrane 2 is not formed (typically the central part). The separation membrane 2 may be formed over the entire inner surface of the cylindrical substrate 3a or cell 34 (i.e., surrounding the first channel 21), as shown in the illustrated example, or it may be formed on a part of the inner surface of the cylindrical substrate 3a or cell 34. When the separation membrane is formed to surround the first channel, the separation efficiency of the substance to be separated can be improved.

[0041] The separation membrane 2 typically has micropores. The separation membrane 2 separates a mixture into separated and unseparated substances by the action of a so-called molecular sieve, which controls the separation characteristics of a specific substance depending on the molecular size and the pore diameter of the separation membrane.

[0042] The separation membrane 2 can be composed of any suitable material. Examples of materials for the separation membrane 2 include zeolite, silica, and carbon. The membrane materials can be used individually or in combination.

[0043] When the substance to be separated contains water, zeolite is preferably used as the material for the separation membrane 2. In one embodiment, the separation membrane 2 is a zeolite membrane.

[0044] A zeolite film is constructed by forming a zeolite film on the surface of a substrate. The zeolite film may contain two or more types of zeolites with different structures and compositions.

[0045] Examples of zeolites that make up a zeolite film include those in which the central atom (T atom) of the oxygen tetrahedron (TO4) constituting the zeolite is solely Si, or composed of Si and Al; AlPO-type zeolites in which the T atom is composed of Al and P; SAPO-type zeolites in which the T atom is composed of Si, Al and P; MAPSO-type zeolites in which the T atom is composed of magnesium (Mg), Si, Al and P; and ZnAPSO-type zeolites in which the T atom is composed of zinc (Zn), Si, Al and P. Some of the T atoms may be substituted with other elements.

[0046] Examples of the above-mentioned zeolites include AEI type, AEN type, AFN type, AFV type, AFX type, BEA type, CHA type, DDR type, ERI type, ETL type, FAU type (X type, Y type), GIS type, LEV type, LTA type, MEL type, MFI type, MOR type, PAU type, RHO type, SAT type, and SOD type zeolites. Among these zeolites, LTA-type zeolites are a notable example.

[0047] The maximum number of member rings in a zeolite is, for example, 12 or less, preferably 10 or less, more preferably 8 or less, and for example, 6 or more.

[0048] The zeolite film contains SiO2 and Al2O3. The zeolite film may further contain alkali metals. The alkali metals are, for example, sodium (Na) or potassium (K).

[0049] The molar ratio of SiO2 / Al2O3 in the zeolite film is, for example, 100 or less, preferably 10 or less, more preferably less than 5, and even more preferably 4 or less. When the molar ratio of SiO2 / Al2O3 in the zeolite film is below the above upper limit, the damage to the zeolite film can be suppressed more stably. The lower limit of the molar ratio of SiO2 / Al2O3 in the zeolite film is typically 2. The molar ratio of SiO2 / Al2O3 can be measured, for example, by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX; X-ray acceleration voltage 10kV).

[0050] The average pore size of the separation membrane 2 can be arbitrarily and appropriately selected depending on the substance to be separated. The average pore size of the separation membrane 2 is, for example, 0.2 nm to 1 nm, preferably 0.3 nm to 0.5 nm. Reducing the average pore size of the separation membrane 2 increases selectivity. The average pore size of the separation membrane 2 is smaller than the average pore size of the substrate 3. If the separation membrane 2 is a zeolite membrane, the average pore size is defined as the arithmetic mean of the short and long axes of the n-membered ring pores, where n is the maximum number of member rings in the zeolite. An n-membered ring pore is a pore where the number of oxygen atoms in the ring structure formed by oxygen atoms bonded to T atoms is n. If there are multiple n-membered ring pores with equal n, the average pore size of the zeolite is defined as the arithmetic mean of the short and long axes of all n-membered ring pores. The average pore size of a zeolite membrane is determined by the skeletal structure of the zeolite, and can be found in the International Zeolite Society's "Database of Zeolite Structures" [online], and the Internet.<URL:http: / / www.iza-structure.org / databases / > It can be determined from the values ​​disclosed.

[0051] The thickness of the separation membrane 2 is, for example, 0.05 μm to 30 μm, preferably 0.1 μm to 20 μm, and more preferably 0.5 μm to 10 μm. Increasing the thickness of the separation membrane increases selectivity. Increasing the thickness of the separation membrane increases the permeation rate.

[0052] The surface roughness (Ra) of the separation membrane 2 is, for example, 5 μm or less, preferably 2 μm or less, more preferably 1 μm or less, and even more preferably 0.5 μm or less. The surface roughness (Ra) can be measured, for example, in accordance with JIS B 0601.

[0053] The separation membrane 2 can be formed by any suitable method depending on the material constituting the membrane. For example, a zeolite membrane can be formed using zeolite as a seed crystal. Base material Zeolite can be obtained by coating a substrate with seed crystals attached, immersing the substrate in a raw material solution, and growing zeolite using the seed crystals as nuclei through hydrothermal synthesis. The raw material solution includes, for example, a silica source, an alumina source, organic matter, an alkali source, and water. The heating temperature in hydrothermal synthesis is, for example, 60°C to 200°C. The heating time is, for example, 1 hour to 240 hours. Alternatively, a separation membrane may be formed using a raw material slurry obtained by mixing an organic binder, ceramic raw materials, and a solvent.

[0054] B-2. Supply Unit, First Recovery Unit, and Second Recovery Unit In one embodiment, as shown in Figure 10, the separation apparatus 1 further comprises, in addition to the separation membrane complex 10, a supply unit 4 for supplying a mixture to the first channel 21 of the separation membrane complex 10; a first recovery unit 5 for recovering the fluid that has passed through the first channel 21; and a second recovery unit 6 for recovering the permeate material that has permeated through the separation membrane 2. The separation apparatus 1 in the illustrated example is configured to allow adjustment of the temperature, pressure, and flow rate of the mixture passing through the first channel. Note that Figure 10 illustrates one embodiment of the present invention, and the present invention is not limited thereto.

[0055] The illustrated supply unit 4 is capable of adjusting the temperature and flow rate of the mixture supplied (flowing into) the first flow path 21. The supply unit 4 comprises a supply line 41, a heating device 42, and a flow rate regulator 43. The supply line 41 is a pipe for supplying the mixture to the first channel 21. The upstream end of the supply line 41 in the direction of mixture supply is connected to a storage tank for storing the mixture, for example, although not shown in the figure. The downstream end of the supply line 41 in the direction of mixture supply is connected to the inlet of the first channel 21 provided by the separation membrane complex 10 (Figure 10 reference). The heating device 42 is provided in the supply line 41 and is capable of heating the mixture passing through the supply line 41. The heating device 42 can employ any suitable configuration. The flow regulator 43 can adjust the flow rate of the mixture through the supply line 41. The flow regulator 43 can employ any suitable configuration. In the illustrated example, the flow regulator 43 is located in the supply line 41 between the heating device 42 and the separation membrane complex 10. The supply unit 4 may include other equipment as needed. For example, other equipment may be present between the flow regulator 43 and the separation membrane complex 10 in the supply line 41.

[0056] The first recovery unit 5 in the illustrated example is capable of adjusting the pressure in the first flow path 21. The first recovery unit 5 comprises a first recovery line 51 and a pressure regulating valve 52. The first recovery line 51 is a pipe through which the fluid (a mixture with reduced separation target substances) that has passed through the first channel 21 of the separation membrane complex 10 passes. The upstream end of the first recovery line 51 in the direction of fluid passage is connected to the outlet of the first channel 21 of the separation membrane complex 10 (Figure 10 (See reference). The downstream end of the first recovery line 51 in the direction of fluid passage is connected to a storage tank, for example, although not shown in the figure. The pressure regulating valve 52 is located in the first recovery line 51. The pressure regulating valve 52 can adjust the opening degree of the first recovery line 51, and thereby adjust the pressure in the first flow path 21. The temperature of environment A may be the temperature at the outlet of the separation membrane (separation membrane complex 10). If a pressure regulating valve 52 is provided, the temperature of environment A may be measured between the outlet of the separation membrane (separation membrane complex 10) and the pressure regulating valve 52. Furthermore, if the separation membranes are arranged in series and a heating device is further provided downstream of the separation membrane (separation membrane complex 10), the temperature of environment A may be measured upstream of the heating device. This temperature may also be the surface temperature of the piping.

[0057] The second recovery unit 6 in the illustrated example includes a second recovery line 61. The second recovery line 61 is a pipe through which the fluid (a fluid containing at least permeable material) that has passed through the second channel 22 of the separation membrane complex 10 passes. The upstream end of the second recovery line 61 in the direction of fluid passage is connected to the outlet of the second channel 22 of the separation membrane complex 10. The downstream end of the second recovery line 61 in the direction of fluid passage is connected to a storage tank, for example, although not shown in the figure.

[0058] In the embodiment described above, the supply unit 4 upstream of the separation membrane complex 10 adjusts the temperature and flow rate of the mixture supplied (flowing into) the first channel 21, and the first recovery unit 5 downstream of the separation membrane complex 10 adjusts the pressure of the mixture in the first channel 21. However, the configuration of the separation apparatus 1 is not limited to this. The supply unit 4 may be configured to adjust the pressure of the mixture in the first channel 21. Also, the first recovery unit 5 may be configured to adjust the flow rate of the mixture passing through the first channel 21. [Industrial applicability]

[0059] The method for stopping a separation apparatus according to an embodiment of the present invention can be used for separating a specific substance in a mixture, and is particularly suitable for separating water from a water-containing mixture. [Explanation of symbols]

[0060] 1 Separation device 2 Separation membrane 3 Base material 21 First channel 22 Second channel

Claims

1. A method for stopping a separation apparatus having a separation membrane after a dehydration step using the separation membrane, Water vapor partial pressure P(H) ２ O) and saturated water vapor pressure P ｓａｔ (H ２ O) and [P(H ２ O) / P ｓａｔ (H ２ The separation membrane is placed under environment A, which satisfies the relationship [O) ≥ 0.001] and has a temperature of 100°C or higher. This includes lowering the temperature of environment A. How to stop the separation device.

2. A method for stopping a separation apparatus according to claim 1, comprising reducing the pressure of the environment A.

3. A method for stopping a separation apparatus according to claim 2, comprising reducing the pressure of the environment A and then lowering its temperature.

4. The method for stopping a separation apparatus according to claim 3, wherein the temperature reduction is performed by adjusting the output of the temperature control means.

5. A method for stopping a separation apparatus according to any one of claims 2 to 4, comprising keeping the temperature of the environment A substantially constant during the depressurization.

6. A method for stopping a separation apparatus according to claim 5, wherein the depressurization operation is performed in stages.

7. A method for stopping a separation apparatus according to claim 1 or 2, comprising keeping the total pressure of the environment A substantially constant during the temperature reduction.

8. A method for stopping a separation apparatus according to claim 1 or 2, wherein the temperature of the environment A is less than 400°C.

9. In the aforementioned environment A, the partial pressure of water vapor P(H ２ O) and the saturated water vapor pressure P ｓａｔ (H ２ O) satisfy the relationship of [1>P(H ２ O) / P ｓａｔ (H ２ O)], the method for shutting down a separation device according to claim 1 or 2.

10. The method for stopping a separation apparatus according to claim 2, wherein the depressurization operation is stopped when the total pressure of environment A becomes atmospheric pressure + 10 kPa.

11. A method for stopping a separation apparatus according to claim 1 or 2, wherein the separation membrane is a zeolite membrane.

12. The method for stopping a separation apparatus according to claim 11, wherein the zeolite membrane is made of LTA-type zeolite.

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