JP2010110759A - Distillation apparatus and concentration method of oxygen isotope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a distillation apparatus capable of reducing a start-up time. <P>SOLUTION: The distillation apparatus consists of first to third towers 1, 2, 3, wherein the outlet of a first tower evaporator 6 and the inlet of a second tower condenser 7 are connected through a first introduction passage 12, the outlet of a second tower evaporator 8 and the inlet of a third tower condenser 9 are connected through a second introduction passage 13, the outlet of the second tower condenser 7 and the inlet of the first tower evaporator 6 are connected through a first return passage 14, and the outlet of the third tower condenser 9 and the inlet of the second tower evaporator 8 are connected through a second return passage 15. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a distillation apparatus and an oxygen isotope enrichment method.

  As represented by the isotope distillation separation process, a distillation operation in a system having a very small vapor pressure ratio (separation factor) requires a very large number of theoretical plates. In such a case, a packed column is generally used in order to suppress the pressure loss of the distillation column, but the packing height necessary for it is theoretically several hundred meters. Therefore, in an actual distillation apparatus, a plurality of distillation towers are connected by piping to constitute one distillation tower group as a whole. FIG. 18 shows an example of a distillation apparatus provided with three distillation columns and connected to the respective distillation columns (first to third columns 61, 62, 63). In this apparatus, the liquid accumulated in the bottoms of the first column 61 and the second column 62 is supplied as a reflux liquid to the tops of the second column 62 and the third column 63 by the liquid pumps 61a and 62a, respectively. Gases derived from the tops of the second column 62 and the third column 63 are returned as rising gas to the bottoms of the first column 61 and the second column 62, respectively. In this process, the process fluid is supplied from the first tower 61 to the second tower 62 and from the second tower 62 to the third tower 63 by the liquid pumps 61a and 62a, but from the second tower 62 to the first tower 61, Since the return of the process fluid from the third column 63 to the second column 62 is performed by a gas pressure difference, the pressure in the distillation column must increase in order from the first column 61 toward the third column 63. In general, since the vapor pressure ratio (separation coefficient) of the separated components is smaller as the operation pressure of the distillation column is higher, the distillation performance is lower in the second column 62 than in the first column 61 and in the third column 63 than in the second column 62. To do. In general, when the vapor pressure ratio of the separated components is very small and the filling height is very large, as in the isotope separation process, the specified amount (sampled amount, planned value as specified) is started after the device is started. It may take several months to several years before the product can be collected (hereinafter referred to as startup time). Therefore, shortening the start-up time has been a conventional problem. The start-up time greatly depends on the process fluid hold-up in the apparatus, and the larger the amount, the longer.

  FIG. 19 is a distillation process having the same function as the apparatus shown in FIG. 18, in which condensers 5, 7, 9 and evaporators 6, 8, 10 are provided in each column 71, 72, 73. This is an apparatus generally used in a process composed of a plurality of distillation columns. In such an apparatus, the column diameter of the distillation column decreases from the column 71 to which the raw material is fed to the column 73 on the downstream side. Thereby, the hold-up of the process fluid in the apparatus can be reduced and the startup time can be shortened. However, even when such an apparatus is used, the pressure in the distillation column increases from the first column 71 toward the third column 73, so that, as in the case of the apparatus shown in FIG. In addition, the third column 73 has lower distillation performance than the second column 72 and the second column 72. A decrease in distillation performance leads to an increase in the required packing height of the distillation column and, in turn, an increase in process fluid hold-up, which is undesirable from the viewpoint of shortening the start-up time. Further, in the conventional isotope distillation process, a packed column with irregular packing was used. In general, the irregular packing has a larger specific surface area than the regular packing, but the liquid hold-up in the distillation column may exceed 10 to 20% of the column volume, and in some cases may exceed 20%, thereby increasing the start-up time. It was a factor.

  This invention is made | formed in view of the said situation, The objective is to provide the apparatus whose starting time is shorter than before in the distillation apparatus comprised from a some distillation column.

  In order to solve the above problems, the distillation apparatus of the present invention is an apparatus for distilling and separating a gas or liquid composed of a plurality of components using a plurality of distillation towers (first to n-th towers) configured in cascade. , The outlet of the evaporator provided at or near the tower bottom of the k-th column (1 ≦ k ≦ (n−1)), and the condenser provided at or near the tower top of the (k + 1) -th column The inlet path connecting the inlet of the tower or the middle part of the tower, the condenser outlet of the (k + 1) th tower, the inlet of the evaporator provided near the tower bottom of the k-th tower, the tower bottom of the tower or the tower A return path is provided to connect the intermediate part of the first and second valves, and a valve for returning the condensate from the condenser outlet of the (k + 1) th tower to the kth tower by its own weight is provided in the return path. This is a distillation apparatus.

In the oxygen isotope enrichment method of the present invention, the source oxygen containing oxygen isotope weight components is concentrated by a cascade process comprising a plurality of distillation columns (first column to n-th column). k ≦ (n−1)) at the bottom of the tower or near the bottom of the tower, at least a part of the gas at the outlet of the condenser, or at the top of the tower of the (k + 1) th tower or the condenser at the top of the tower, At least a part of the liquid at the top of the (k + 1) th tower or at the condenser outlet of the tower is supplied to the middle part of the tower and the weight of the condensate itself as a return liquid is fed into the evaporator inlet of the kth tower. Alternatively, at least one of oxygen molecules ¹⁶ O ¹⁷ O, ¹⁶ O ¹⁸ O, ¹⁷ O ¹⁷ O, ¹⁷ O ¹⁸ O, and ¹⁸ O ¹⁸ O containing an oxygen isotope component by being returned to the tower bottom or the middle of the tower Specialize in concentrating It is a method for concentrating oxygen isotopes according to.

  In the method of the present invention, the oxygen isotope concentrate concentrated by the concentration method is subjected to oxygen isotope scrambling to obtain a concentrate having an increased concentration of at least one oxygen molecule containing the oxygen isotope component. This is a characteristic oxygen isotope enrichment method.

  In the method of the present invention, the oxygen isotope concentrate concentrated by the concentration method is subjected to oxygen isotope scrambling to obtain a concentrate having an increased concentration of at least one oxygen molecule containing the oxygen isotope component, The oxygen isotope enrichment method is characterized in that a concentrate is obtained by further increasing the concentration of at least one oxygen molecule containing the oxygen isotope weight component by the enrichment method.

  As described above, in the present invention, the outlet of the evaporator provided at or near the tower bottom of the k-th tower (1 ≦ k ≦ (n−1)), the (k + 1) -th tower An inlet path connecting the inlet of the condenser provided near the tower top or near the tower top or an intermediate part of the tower, the condenser outlet of the (k + 1) th tower, and evaporation provided near the tower bottom of the k-th tower. A return path connecting the inlet of the vessel or the bottom of the tower or the middle of the tower is provided, so that a part of the effluent from the condenser of the (k + 1) th tower can be returned through this return path. . For this reason, each column pressure can be set lower than before, the vapor pressure ratio between the isotope components in each column can be increased, and the distillation performance can be improved. Therefore, the filling height of each tower can be lowered, and the startup time can be shortened. In addition, a product containing an oxygen isotope component at a high concentration can be obtained. Further, the liquid hold-up amount can be reduced, and the startup time of the apparatus can be further shortened.

It is a schematic block diagram which shows the 1st Embodiment of the distillation apparatus of this invention. It is a perspective view which shows an example of the non-self-distribution promotion type | mold regular packing used for the distillation apparatus of this invention. It is a perspective view which shows the other example of the non-self distribution promotion type | mold regular packing used for the distillation apparatus of this invention. It is a perspective view which shows an example of the self-distribution promotion type | mold regular packing used for the distillation apparatus of this invention. It is a perspective view which shows the other example of the self-distribution promotion type | mold regular packing used for the distillation apparatus of this invention. It is a perspective view which shows another example of the self-distribution promotion type | formula regular packing used for the distillation apparatus of this invention. It is a schematic block diagram which shows the 2nd Example of the distillation apparatus of this invention. It is a schematic block diagram which shows the example of 3rd Embodiment of the distillation apparatus of this invention. It is a block diagram which shows the modification of the apparatus shown in FIG. It is a schematic block diagram which shows the other embodiment of the distillation apparatus of this invention. It is a schematic block diagram which shows the circulation path | route of the heat medium fluid used for the distillation apparatus shown in FIG. It is a schematic block diagram which shows further another example of embodiment of the distillation apparatus of this invention. It is a schematic block diagram which shows the hydrogenation reaction apparatus of the distillation apparatus shown in FIG. It is a schematic block diagram which shows further another example of embodiment of the distillation apparatus of this invention. It is a schematic block diagram which shows the example of the isotope scrambler used for the distillation apparatus shown in FIG. FIG. 15 is a graph showing the result of simulating the enrichment of oxygen isotope components, using the apparatus shown in FIG. 14 as an example, and shows the concentration distribution of each isotope component in each tower. In this graph, the horizontal axis represents the total filling height, and the vertical axis represents the concentration of each isotope component. Except that the number of distillation columns is 16, a graph showing the results of simulating the concentration of oxygen isotope weight components, using as an example a distillation apparatus employing the same configuration as the apparatus shown in FIG. It shows the concentration distribution of each isotope component in each tower. In this graph, the horizontal axis represents the total filling height, and the vertical axis represents the concentration of each isotope component. It is a schematic block diagram which shows an example of the conventional distillation apparatus. It is a schematic block diagram which shows the other example of the conventional distillation apparatus.

  FIG. 1 shows a first embodiment of a distillation apparatus according to the present invention. The distillation apparatus shown here includes three distillation columns arranged in cascade, that is, a first column 1, a second column 2, and a first column. Three towers 3 are provided. In addition, the distillation column is configured in cascade. The product that is concentrated in one distillation column is further concentrated in the next distillation column, and the distillation column is connected so that it can be further concentrated in the next distillation column. The entire distillation column constructed in this way is called a cascade process. In addition, a route indicated by a broken line in the figure is a modification of the present embodiment and is not included in the apparatus of the present embodiment.

  In the vicinity of the tops of the first to third towers 1, 2, and 3, a first tower condenser 5 that cools and liquefies at least a part of the gas derived from the tops of the towers 1, 2, and 3, respectively. A second tower condenser 7 and a third tower condenser 9 are provided. The condensers 5, 7, and 9 include first flow paths 5 a, 7 a, and 9 a through which gases derived from the tower tops of the towers 1, 2, and 3 are introduced, respectively, and a second flow path 5 b through which the heat medium fluid flows. , 7b, 9b, which can be cooled and liquefied by exchanging the derived gas with the heat medium fluid. As the condensers 5, 7, and 9, it is preferable to use plate fin type heat exchangers. In the illustrated example, the condensers 5, 7, and 9 are provided outside the towers 1, 2, and 3, but may be provided inside the tower tops of the towers 1, 2, and 3.

  In the vicinity of the tower bottoms of the towers 1, 2, and 3, a first tower evaporator 6 and a second tower evaporator 8 that heat and vaporize at least a part of the liquid led out from the tower bottoms of the towers 1, 2, and 3, respectively. A third tower evaporator 10 is provided. The evaporators 6, 8, and 10 include first flow paths 6a, 8a, and 10a into which liquids led from the towers 1, 2, and 3 are introduced, respectively, and second flow paths 6b, 8b, through which the heat medium fluid flows. 10b, and can be heated and vaporized by exchanging the derived liquid with a heat medium fluid. As the evaporators 6, 8, and 10, it is preferable to use plate fin type heat exchangers. In order to reduce liquid hold-up, these evaporators are installed at positions where the liquid amount in the liquid reservoir at the bottom of each distillation column is minimized within the operable range. In the illustrated example, the evaporators 6, 8, and 10 are provided outside the towers 1, 2, and 3, but may be provided inside the tower bottoms of the towers 1, 2, and 3. In this case, a coil heat exchanger may be used.

  In the distillation apparatus of this embodiment, the first tower evaporator 6 provided near the bottom of the first tower 1 (the outlet of the first flow path 6a) and the second tower 2 near the top. The inlet of the second tower condenser 7 (the inlet of the first flow path 7a) is connected by the first introduction path 12 via the valve 12v. Similarly, the outlet of the second tower evaporator 8 (the outlet of the first flow path 8a) and the inlet of the third tower condenser 9 (the inlet of the first flow path 9a) are second introduced via the valve 13v. They are connected by a path 13.

  The outlet of the second tower condenser 7 (the outlet of the first flow path 7a) and the inlet of the first tower evaporator 6 (the inlet of the first flow path 6a) are connected via the valve 14v to the first return path. 14 is connected. Similarly, the outlet of the third tower condenser 9 (the outlet of the first flow path 9a) and the inlet of the second tower evaporator 8 (the inlet of the first flow path 8a) are connected to the second through the valve 15v. They are connected by a return path 15. The mounting positions of the valves 14v and 15v are above the return paths 14 and 15 (near the condenser), and the pressure difference between the K-th column and the K + 1-th column in the cascade connection of a plurality of columns described later is the cascade system. It is provided at a position where a head pressure is obtained so as to obtain a pressure difference between the columns so that the can be operated.

  The first to third towers 1, 2, 3 are filled with a regular packing 11. As the regular packing 11, a non-self-distribution promoting regular packing and / or a self-distribution promoting regular packing can be suitably used. Non-self-distribution-promoting regular packing is a liquid flow in the cross-sectional direction perpendicular to the column axis, in which the liquid flow descending in the distillation column and the gas flow rising in the distillation column face each other along the surface. A packing material having a shape and structure in which gas-liquid contact is performed without promoting mixing of the gas flow, for example, a large number of plate-like materials made of aluminum, copper, an aluminum-copper alloy, stainless steel, various plastics, etc. The thing which has arrange | positioned the pipe | tube etc. in parallel with the main flow direction (column axial direction) can be mentioned. Here, the main flow refers to a liquid flow descending along the column axis direction and an ascending gas flow in the distillation column, and a substance generated at the interface between the liquid flow and the gas flow (that is, the boundary layer) on the surface of the packing material. It refers to the flow in the tower axis direction relative to the flow of movement.

  An example of a typical non-self-promoting ordered packing is shown in FIGS. The non-self-distribution promoting regular packing 51 shown in FIG. 2 is a honeycomb-like structure made of a plate material parallel to the tower axis direction. Further, the non-self-distribution-promoting ordered packing 52 shown in FIG. 3 includes a lattice structure composed of a plurality of plate members 52a parallel to each other and a plurality of plate members 52b perpendicular to the plate members 52a along the tower axis direction. It is arranged.

  In the self-distribution promoting ordered packing, the liquid flow descending in the distillation column and the gas flow rising in the distillation column are brought into gas-liquid contact mainly on the surface of the regular packing, and at this time, the liquid flow and gas flow are in contact with each other. Flow on the surface of the regular packing opposite to each other in the main flow direction along the column axis direction, and at the same time, mixing of the liquid flow and / or gas flow is promoted in a direction perpendicular to the main flow direction. Filler with shape and structure to be contacted, which is made of aluminum, copper, aluminum-copper alloy, stainless steel, various plastics, etc., into various regular shapes and made into a block structure of laminated structure And is also referred to as structured packing.

  Examples of typical self-distribution-promoting ordered packings are shown in FIGS. The self-distribution promoting regular packing 53 shown in FIG. 4 is formed by arranging a plurality of corrugated thin plates in parallel to the tower axis and laminating them so as to contact each other. The grooves are inclined with respect to the tower axis, and adjacent corrugated thin plates are arranged so that the forming directions of the corrugated grooves intersect. Furthermore, with each thin plate arranged so as to be perpendicular to the horizontal plane, each thin plate is formed with a number of rows along a direction perpendicular to the tower axis, and a number of holes are spaced from each other. 53a is provided. FIG. 5 shows a structural unit of another example of the self-distribution promoting regular packing, and the self-distribution promoting regular packing 54 shown here forms a wave-like groove by forming a corrugated sheet into a corrugated groove. Further, there is a feature in that a minute corrugated groove (fold) 54b formed in a direction forming a predetermined angle with respect to the corrugated groove is further provided. Reference numeral 54a denotes a hole formed in the thin plate. The self-distribution promoting type regular packing 55 shown in FIG. 6 has a portion provided with minute corrugated grooves (folds) 55b formed in a direction forming a predetermined angle with respect to the corrugated grooves on the corrugated thin plate, It has a structure in which smooth portions that are not provided are alternately arranged. Reference numeral 55a denotes a hole formed in the thin plate.

  Hereinafter, the first embodiment of the method for concentrating oxygen isotope components according to the present invention will be described in detail by taking as an example the case of using the apparatus of FIG. 1 which is the first embodiment of the distillation apparatus of the present invention. To do. First, the raw material oxygen gas is supplied into the tower 1 as a first tower feed 101 through a path 20 which is a feed section connected to an intermediate section (height direction intermediate section) of the first tower 1. As the raw material oxygen gas, it is desirable to use high purity oxygen. As the high-purity oxygen, it is possible to use an oxygen whose purity is increased to 99.999% or more by removing impurities such as argon, hydrocarbons, krypton, xenon, fluorine compounds (perfluorocarbon, etc.) in advance. In particular, it is preferable in terms of safety to use raw material oxygen from which hydrocarbons have been removed.

When the raw material oxygen gas supplied into the first column 1 rises in the column 1 and passes through the packing 11, it is vaporized in contact with a later-described reflux liquid (falling liquid). In the raw material oxygen gas, oxygen molecules containing heavy isotopes ^{(16 O 17 O, 16 O} 18 O, 17 O 17 O, 17 O 18 O, and ¹⁸ O ¹⁸ O) is easily condensed because the high-boiling, In the process of gas-liquid contact, the concentration of isotope in the descending liquid increases and the concentration of the isotope in the rising gas decreases. The rising gas having the reduced heavy component concentration and reaching the top of the tower is led out from the tower 1 through the path 21 and then divided into two, one of which is introduced into the first flow path 5a of the first tower condenser 5, where Heat exchange with the heat medium fluid flowing in the two flow paths 5 b is condensed and returned to the upper part of the tower 1 as a reflux liquid, and the other is discharged out of the system as waste gas 103 through the path 22.

The reflux liquid returned to the top of the first tower 1 is in gas-liquid contact with the raw material oxygen gas that rises in the tower 1 while flowing down the surface of the regular packing 11 as a descending liquid, and the ascending gas described later. The tower bottom of tower 1 is reached. In this process of vapor-liquid contact, the oxygen molecules containing liquefied easily heavy oxygen isotopes in the descending liquid ^{(16 O 17 O, 16 O} 18 O, 17 O 17 O, 17 O 18 O, and ¹⁸ O ¹⁸ O ) Is concentrated.

  The descending liquid reaching the tower bottom of the first tower 1 (hereinafter, the liquid accumulated in the tower bottom of each tower is referred to as the tower bottom liquid) is led out from the tower 1 through the path 23, and in the first return path 14 described above. After joining the first return liquid 107 described later and introduced into the first flow path 6a of the first tower evaporator 6, the heat medium fluid flowing in the second flow path 6b is exchanged for heat and vaporized, The first tower outlet gas 102, which is a concentrate enriched with oxygen isotope weight components, is led out from the evaporator 6 through the first introduction path 12 described above.

  A part of the first column derived gas 102 derived from the evaporator 6 is returned to the lower part of the column 1 through the path 24 and becomes an ascending gas rising in the column 1, and the other part is used as the second column feed gas 104. The gas flows into the second tower condenser 7 through the introduction path 12 and is introduced into the second tower condenser 7, where it is condensed and led out of the condenser 7 through the return path 14 and then divided into two. One of the bisected condensates joins the first tower bottom liquid as the first return liquid 107 through the first return path 14 and the valve 14v, and then enters the first tower evaporator 6. be introduced. The return liquid 107 is returned by the weight of the condensate itself, which is derived by liquefying the condenser 7 and flowing down the path 14.

  In the method of this embodiment, a part of the condensate that has passed through the second tower condenser 7 is returned to the first tower evaporator 6 as the first return liquid 107, and the return liquid is its own weight (head pressure). Therefore, the pressure at the top of the second tower 2 can be made lower than the pressure at the bottom of the first tower 1. Thus, the above-mentioned second column feed gas 104 can be sent to the second column 2 through paths 12 and 25.

  The other condensate derived from the condenser 7 and divided into two halves is supplied to the upper part of the second tower 2 as the second tower reflux liquid 104 through the path 25 and becomes the descending liquid, and the ascending gas and gas-liquid in the second tower 2. It reaches the bottom of the second tower 2 in contact. In this gas-liquid contact process, the concentration of the isotope weight component in the rising gas decreases and the oxygen isotope weight component is further concentrated in the descending solution.

  The rising gas having the reduced heavy component concentration and reaching the top of the tower is led out from the tower 2 through the path 28 and joins with the second tower feed gas 104 through the introduction path 12 as the top gas 106.

  The liquid at the bottom of the second tower 2, which is a concentrate enriched with oxygen isotope weight components, is led out from the tower 2 through the path 26, and joins the second return liquid 112 described later in the second return path 15 described above. Then, after the gas is introduced into the second tower evaporator 8 and vaporized, it is led out from the evaporator 8 through the second introduction path 13 as the second tower lead-out gas 105, which is a concentrate obtained by concentrating oxygen isotope components. Is done.

  A part of the second column derived gas 105 derived from the evaporator 8 is returned to the lower part of the column 2 through the path 27 and becomes an ascending gas rising in the column 2, and the other part is introduced as the third column feed gas 108. Through a path 13, it merges with a later-described third tower top gas 111, is introduced into a third tower condenser 9, condenses there, and is bisected after being led out from the condenser 9 through a second return path 15. The One of the bisected condensates is introduced into the second tower evaporator 8 as the second return liquid 112 through the second return path 15 and the valve 15v. The return liquid 112 is returned by liquefying and extracting the condenser 9 and the weight of the condensate itself flowing down the path 15.

  In the method of this embodiment, a part of the condensate that has passed through the third column condenser 9 is returned to the second column evaporator 8 as the second return liquid 112, and the return liquid is its own weight (head pressure). Therefore, the pressure at the top of the third tower 3 can be made lower than that at the bottom of the second tower 2. Thus, the third tower feed gas 108 can be sent to the third tower 3 through the paths 13 and 29.

  The other condensate derived from the condenser 9 and divided into two halves is supplied to the upper part of the third tower 3 as the third tower reflux liquid 108 through the path 29 and becomes the descending liquid, and the ascending gas and gas-liquid in the third tower 3. It reaches the bottom of the third tower 3 while making contact. In this gas-liquid contact process, the concentration of the isotope weight component in the rising gas decreases and the oxygen isotope weight component is further concentrated in the descending solution.

  The rising gas having the reduced heavy component concentration and reaching the top of the tower is led out from the tower 3 through the path 33 and joins with the third tower feed gas 108 through the introduction path 13 as the tower top gas 111.

  The liquid at the bottom of the third tower 3, which is a concentrate enriched with oxygen isotope components, is led out from the tower 3 through the path 30 and introduced into the third tower evaporator 10, where it is vaporized and then oxygen isotope. It is derived from the evaporator 10 as a third column derived gas 109 which is a concentrated component. The third tower derived gas 109 derived from the evaporator 10 is divided into two, one is returned to the lower part of the tower 3 through the path 31 and becomes the rising gas rising in the tower 3, and the other is the oxygen isotope component through the path 32. Is recovered as product gas 110, which is a concentrate obtained by concentrating.

  Here, the setting of the amount of the feed gas 104, 108 to the second tower and the third tower will be described. The flow rate of the second column feed gas 104 is relative to the flow rate of the target component accompanying the product recovered from the second column or the third column to the outside of the apparatus (in the present embodiment, only the product gas 110). It sets so that the flow volume of the target component accompanying the 2nd tower feed gas 104 may become sufficient quantity. Specifically, [the flow rate of the target component in the product 110 recovered from the second column or the third column to the outside of the apparatus] / [the flow rate of the target component accompanying the second column feed gas 104] = [of the target component] Yield] is preferably set so that the yield of the target component is 1% to 10% or less. If the amount of the second column feed gas 104 is made too small (if an attempt is made to increase the yield of the target component), the distillation performance of the second column and the third column will deteriorate. On the contrary, if the amount of the second column feed gas 104 is excessively increased, the distillation performance is not improved so much as the heat exchange amount between the first column evaporator 6 and the second column condenser 7 is increased.

  The flow rate of the third column feed gas 108 is third with respect to the flow rate of the target component accompanying the product recovered from the third column to the outside of the apparatus (only the product gas 110 in this embodiment). The flow rate of the target component entrained in the tower feed gas 108 is set to a sufficient amount. Specifically, [flow rate of target component entrained in product 110 recovered from the third column outside the apparatus] / [flow rate of target component entrained in third column feed gas 108] = [yield of target component] Is preferably set to be 1% to 10% or less. If the amount of the third column feed gas 108 is too small (too much to increase the yield of the target component), the distillation performance of the third column deteriorates. On the other hand, if the amount of the third column feed gas 108 is excessively increased, the distillation performance is not improved so much as the heat exchange amount between the second column evaporator 8 and the third column condenser 9 is increased.

Next, the operation control method for each tower will be described. When attention is paid to a certain tower, the following four parts can be controlled.
(1) A valve in a gas pipe supplied from the k-th tower to the (k + 1) -th tower.
(2) Valve of liquid piping returned from the (k + 1) th tower to the kth tower.
(3) Evaporator heat exchange (warm fluid flow, pressure)
(4) Heat exchange amount of condenser (flow rate and pressure of cold fluid)
Since it is difficult to adjust four at the same time, basically (1) and (3) are fixed for each tower, and (2) and (4) are adjusted while observing the state of the apparatus.

First, (3) adjustment of the heat exchange amount of the evaporator (flow rate and pressure of warm fluid) is performed as follows. The amount of heat exchange in the evaporator is not controlled after it is adjusted and set in advance so that the steam load of each column becomes an appropriate value (planned value). The density-corrected superficial velocity in the distillation column is 0.5 m / s (kg / m ³ ) ^0.5 or more, 3.0 m / s (kg / m ³ ) ^0.5 or less, preferably 0.7 m / s. (Kg / m ³ ) It is preferably set to be ^0.5 or more and 2.2 m / s (kg / m ³ ) ^0.5 or less.

  Next, (1) the valves 12v and 13v in the gas piping (paths 12 and 13) supplied from the k-th tower to the (k + 1) -th tower are adjusted. When the top pressures of the columns are substantially equal, the k-th tower bottom pressure is higher than the (k + 1) th tower top pressure by the pressure loss of the k-th tower. Therefore, after providing a valve in the middle of the piping, the flow rate of the gas supplied from the kth tower to the (k + 1) th tower is detected and controlled to a prescribed flow rate. Since this flow rate is not exact, once the flow rate is just good (approximately equal to the planned value), the valve opening is not adjusted. If the pressure in each column is constant, this flow rate hardly changes.

  Next, (4) the heat exchange amount of the condenser (flow rate and pressure of the cold fluid) is set. This is adjusted so that the pressure in each distillation column is constant. Since the heat exchange amount (3) of the evaporator is fixed, if the heat exchange amount (4) of the condenser is small, the pressure in the distillation column will continue to rise. Conversely, when the heat exchange amount (4) of the condenser is large, the pressure in the distillation column continues to decrease. Once adjusted to the optimum value, the intrusion heat of the device changes depending on the weather, and the pressure fluctuates. Therefore, it is necessary to control the heat exchange amount (4) of the condenser while always detecting the pressure of each column.

  Next, (2) the valves 14v and 15v of the liquid piping (paths 14 and 15) returned from the (k + 1) th tower to the kth tower are adjusted. The control valves 14v and 15v are installed at a position relatively close to the condenser at the top of the tower as long as a predetermined liquid head is obtained. This is to reduce the liquid holdup in the piping. This opening degree is adjusted while detecting the liquid level at the bottom of each distillation column (the liquid level of the evaporator). When this opening is too small and the return from the (k + 1) -th tower to the k-th tower becomes small, (1) since the valves 12v and 13v of the gas piping are fixed, from the (k + 1) -th tower to the n-th tower Process fluid hold-up is increasing. Since the pressure of each column is kept constant by (4) condensers 5, 7, and 9, an increase in holdup leads to an increase in the liquid level at the bottom of the distillation column. On the other hand, when the return from the (k + 1) th column to the kth column becomes large, the liquid level at the bottom of the distillation column decreases. Accordingly, (2) the valve of the liquid pipe must be controlled so that the liquid level at the bottom of each distillation column is constant. The control valves 14v and 15v are installed at a position relatively close to the condenser at the top of the tower within a range where a predetermined liquid head can be obtained. However, in consideration of ease of control and certainty, the control valves 14v and 15v are provided at a position close to the evaporator. Is good.

  In the distillation apparatus of this embodiment, the outlet of the first tower evaporator 6 and the inlet of the second tower condenser 7 are connected by the first introduction path 12, and the outlet of the second tower evaporator 8 and the third tower are connected. The inlet of the condenser 9 is connected by the second introduction path 13, and the outlet of the second tower condenser 7 and the inlet of the first tower evaporator 6 are connected by the first return path 14, and the third tower Since the outlet of the condenser 9 and the inlet of the second tower evaporator 8 are connected by the second return path 15, some of the condensate that has passed through the condensers 7 and 9 is evaporated as return liquids 107 and 112. Can be returned to vessels 6 and 8. For this reason, the pressure in the towers 2 and 3 can be set lower than before, the vapor pressure ratio between the isotope components in each tower can be increased, and the distillation performance can be improved. Thereby, the filling height of each column can be lowered, the amount of liquid hold-up can be reduced, and the startup time can be shortened. For the above reasons, a product containing an oxygen isotope component at a high concentration can be obtained efficiently.

  Further, in the conventional apparatus (FIG. 19), the entire supply path from the tower on the front stage side to the tower on the rear stage side is filled with liquid, whereas in the apparatus of this embodiment, of the return paths, Only the portion corresponding to the liquid head corresponding to the pressure difference between these towers is filled with liquid. That is, the pressure difference between these towers required to return the return liquids 107 and 112 liquefied by the condensers 7 and 9 to the front stage tower in the return path from the rear stage tower to the front stage tower. Only the path portion corresponding to the liquid head corresponding to is filled with the liquid. For this reason, the liquid hold-up amount is reduced, and the startup time of the apparatus can be further shortened. In particular, when the column diameter of the distillation column is small, the pipe diameter of the return path is relatively large, so it is considered that the difference in liquid holdup between the apparatus of the present embodiment and the conventional apparatus increases, and the startup In terms of time, it is considered that the superiority of the device of the present invention becomes clearer.

  Further, by using regular packing (self-distribution promoting packing or non-distribution promoting packing) in the columns 1, 2, and 3, the pressure loss in the column can be reduced, and the pressure in the column can be set low. . For this reason, while increasing the vapor pressure ratio between each component and raising distillation efficiency, liquid holdup amount can be made small and the starting time can be shortened further. Along with this, the operation cost can be reduced. Furthermore, by using the self-distributed regular packing, the gas-liquid contact efficiency in the column can be increased, and the isotope enrichment efficiency can be increased.

  In the distillation apparatus of the above embodiment, the outlet of the second tower condenser 7 and the inlet of the first tower evaporator 6 are connected by the first return path 14, and the outlet of the third tower condenser 9 and the second tower are connected. Although the inlet of the evaporator 8 is connected by the 2nd return path | route 15, the distillation apparatus of this invention is not restricted to this, As the 1st return path | route is shown by the code | symbol 14a (path | route shown with a broken line) The outlet of the second tower condenser 7 is connected to the intermediate part of the first tower 1, and the second return path is indicated by reference numeral 15a (path indicated by a broken line) of the third tower condenser 9 as shown in FIG. The outlet and the intermediate part of the second tower 2 may be connected. In addition, the towers 1, 2, and 3 are not limited to packed towers using the above packing, and wet wall towers can also be used.

FIG. 7 shows a second embodiment of the distillation apparatus of the present invention. The distillation apparatus shown here is different from the distillation apparatus shown in FIG. 1 in the following points.
(1) The outlet of the first tower evaporator 6 and the top of the second tower 2 are directly connected by the first introduction path 35, and the second tower feed gas 104 ′ passed through the first tower evaporator 6 is It can be directly supplied to the top of the second tower 2.
(2) The outlet of the second tower evaporator 8 and the top of the third tower 3 are directly connected by the second introduction path 36, and the third tower feed gas 108 ′ passed through the second tower evaporator 8 is It can be directly supplied to the top of the third tower 3.
(3) The outlet of the second tower condenser 7 and the tower bottom of the first tower 1 are connected by the first return path 37, and the return liquid 107 ′ from the second tower condenser 7 is supplied to the first tower 1. It can be returned to the bottom of the tower.
(4) The outlet of the third tower condenser 9 and the bottom of the second tower 2 are connected by the second return path 38, and the return liquid 112 ′ from the third tower condenser 9 is connected to the second tower 2. It can be returned to the bottom of the tower. In addition, the path | route shown with a broken line in a figure is a modification of the apparatus of this embodiment, as it mentions later.

  Hereinafter, the second embodiment of the method for concentrating oxygen isotopes according to the present invention will be described by taking the case of using the apparatus of FIG. 7 as an example. The raw material oxygen gas supplied into the first column 1 as the first column feed 101 through the path 20 is distilled by gas-liquid contact in the column 1. The tower bottom liquid enriched with oxygen isotopes in the first tower 1 is introduced into the first tower evaporator 6 through the path 23 ', where it is vaporized and led out from the evaporator 6 as the first tower outlet gas 102'. Is done. A part of the derived gas 102 ′ is returned to the lower part of the first tower 1 through the path 39, and the other part is directly introduced into the top of the second tower 2 as the second tower feed 104 ′ through the first introduction path 35. Is done. The rising gas that has reached the top of the tower due to a decrease in the isotope component concentration in the second tower 2 is led out from the second tower 2 through the path 28 ′ as the tower top gas 106 and condensed in the second tower condenser 7. , One is returned as a reflux liquid to the upper part of the second tower 2 through the path 25 ′, and the other is returned to the bottom of the first tower 1 as the first return liquid 107 ′ through the first return path 37. .

  The tower bottom liquid enriched with oxygen isotopic components in the second tower 2 is introduced into the second tower evaporator 8 through the path 26 ', where it is vaporized and led out from the evaporator 8 as the second tower outlet gas 105'. Is done. A part of the derived gas 105 ′ is returned to the lower part of the second tower 2 through the path 40, and the other part is directly introduced into the top of the third tower 3 as the third tower feed 108 ′ through the second introduction path 36. The The rising gas that has reached the top of the tower due to a decrease in the isotope weight component concentration in the third tower 3 is led out from the third tower 3 through the path 33 ′ as the tower top gas 111 and condensed in the third tower condenser 9. , One is introduced as the reflux liquid of the tower 3 through the path 29 'to the upper part of the third tower 3, and the other is fed as the second return liquid 112' through the second return path 38 to the bottom of the second tower 2. Will be returned.

  In the distillation apparatus of the present embodiment, a part of the condensate that has passed through the condensers 7 and 9 can be returned to the preceding column as the return liquids 107 ′ and 112 ′ by the weight (head pressure) of the condensate itself. . For this reason, the amount of liquid is smaller than that of the conventional method using a liquid pump, and the start-up time can be shortened as in the apparatus of the first embodiment. In addition, by connecting the tower bottom and the tower top, a product containing a high concentration of oxygen isotope components can be obtained efficiently with a small total tower length.

  In the distillation apparatus of the above embodiment, the outlet of the first tower evaporator 6 and the top of the second tower 2 are connected by the first introduction path 35, and the outlet of the second tower evaporator 8 and the third tower 3 are connected. The tower top of the tower 3 is connected by the second introduction path 36, and the outlet of the second tower condenser 7 and the tower bottom of the first tower 1 are connected by the first return path 37, so that the third tower Although the outlet of the condenser 9 and the bottom of the second column 2 are connected by the second return path 38, the distillation apparatus of the present invention is not limited to this. For example, as indicated by reference numerals 35a and 36a (paths indicated by broken lines), the first and second introduction paths can be connected to the middle portion of the towers 2 and 3 instead of the tower tops, or reference numerals 37a and 38a. As shown, the first and second return paths can be connected not to the tower bottoms of towers 1 and 2 but to the middle part of towers 1 and 2.

FIG. 8 shows a third embodiment of the distillation apparatus of the present invention. The distillation apparatus shown here is different from the distillation apparatus shown in FIG. 7 in the following points.
(1) The path 28 ′ for guiding the top gas 106 of the second tower 2 to the second tower condenser 7 and the tower bottom of the first tower 1 are connected by the first return path 37 ′. A part of the second tower top gas 106 can be returned to the bottom of the first tower 1.
(2) The path 33 ′ for guiding the top gas 111 of the third tower 3 to the third tower condenser 9 and the tower bottom of the second tower 2 are connected by the second return path 38 ′, and the third tower Part of the third tower top gas 111 can be returned to the bottom of the second tower 2.
(3) Blowers 41 and 42 are provided in the first and second return paths 37 'and 38', respectively. As the blowers 41 and 42, a room temperature compressor or a low temperature compressor can be used. However, when a room temperature compressor is used, as shown in FIG. 9, heat exchangers 41a and 42a are connected to the return paths 37 ′ and 38 ′. Need to intervene.

  Hereinafter, the case of using the apparatus of FIG. 8 as an example will be described with respect to the third embodiment of the oxygen isotope weight concentration method of the present invention. The rising gas having a reduced isotope component concentration in the second tower 2 and reaching the top of the tower 2 is divided into two after being led out from the second tower 2 through the path 28 ′ as the tower top gas 106. One of the bisected tower top gas 106 is condensed in the second tower condenser 7 and then returned to the upper part of the second tower 2 to become the reflux liquid of the tower, and the other is blower 41 through the first return path 37 ′. In this way, the pressure is increased and returned to the bottom of the first tower 1 as the first return liquid 107 ″. Similarly, the top gas 111 led out from the top of the third tower 3 passes through the path 33 ′. Through the third tower 3 and then divided into two. One is condensed in the third tower condenser 9 and then returned to the upper part of the third tower 3 to become the reflux liquid of the tower, and the other is the second return path. 38 'reaches the blower 42, where it is pressurized and returned to the bottom of the second tower 2 as the second return liquid 112 ".

  In the distillation apparatus of this embodiment, since each path is supplied in a gaseous state and is not liquid, the start-up time can be shortened as in the apparatus of the first embodiment described above. Further, since the tower bottom and the tower top, and the tower top and the tower bottom are connected to each other, a product containing an oxygen isotope component at a high concentration can be obtained. In the distillation apparatus of the present embodiment, the outlet of the first tower evaporator 6 and the tower top of the second tower 2 are connected by the first introduction path 35, and the outlet of the second tower evaporator 8 and the third tower 3 are connected. The tower top of the tower 3 is connected by a second introduction path 36, and the inlet of the second tower condenser 7 and the tower bottom of the first tower 1 are connected by a first return path 37 '. Although the inlet of the column condenser 9 and the column bottom of the second column 2 are connected by the second return path 38 ', the distillation apparatus of the present invention is not limited to this. For example, as indicated by reference numerals 35a and 36a (paths indicated by broken lines), the first and second introduction paths can be connected to the middle portion of the towers 2 and 3 instead of the tower tops. , 38′a, the first and second return paths can be connected to the middle of towers 1 and 2 instead of the tower bottoms of towers 1 and 2.

In each of the above embodiments, a distillation apparatus having three distillation columns has been shown. However, in the distillation apparatus of the present invention, the number of distillation columns is not limited to this. The distillation apparatus shown in FIG. 10 is a distillation apparatus having n distillation columns. Distillation apparatus shown here, the distillation column _A 1 to A _n of the n, a condenser _B 1 .about.B _n provided near the top of these columns _A 1 to A _n, the tower _A 1 to A _n The evaporators C _{1 to} C _n provided near the tower bottom, the outlet of the k-th tower evaporator C _k provided near the tower bottom of the k-th tower (1 ≦ k ≦ (n−1)) and the (k + 1) th ) Return path E connecting the introduction paths D _{1 to} D _n−1 connecting the tower top and the outlet of the (k + 1) th tower condenser B _{k + 1} of the (k + 1) th tower and the tower bottom of the kth tower. _{1 to} En _-1 are provided. The number n of distillation columns can be 2 to 100, for example.

FIG. 11 shows a circulation system of the heat medium fluid of the evaporator and the condenser in the distillation apparatus shown in FIG. As shown in FIG. 11, each of the condensers B _{1 to} B _n and the evaporators C _{1 to} C _n are connected by a circulation path 81 for a heat medium fluid. In this circulation path 81, the heat medium fluid in the storage tank 82 is led out, introduced into the condensers B _{1 to} B _n through the first flow path of the pump 83 and the supercooler 84, and then the supercooler 84. After reaching the first flow path of the heat exchanger 85 through the second flow path, and then introduced into the evaporators C _{1 to} C _n through the blower 86 and the second flow path of the heat exchanger 85, the storage tank 82 It is supposed to be returned. The supercooler 84 is for cooling the heat medium fluid in order to prevent the heat medium fluid from vaporizing before reaching the condenser.

  In the present invention, similarly, in the distillation apparatus of the first embodiment shown in FIG. 1, the distillation apparatus of the second embodiment shown in FIG. 7, and the distillation apparatus of the third embodiment shown in FIG. The number is not limited to the illustrated example, and can be set arbitrarily.

Further, in each of the above embodiments, the method of concentrating the oxygen isotope component by low-temperature distillation of the raw material oxygen is shown. However, the present invention is not limited to this, and water is used as a raw material. Distilling with an example distillation apparatus, and concentrating at least one of deuterium water H ₂ ¹⁷ O, H ₂ ¹⁸ O, D ₂ ¹⁷ O, D ₂ ¹⁸ O, DH ¹⁷ O, and DH ¹⁸ O containing oxygen isotope components By doing so, heavy oxygen water can also be produced. Even in this case, the activation time can be shortened as in the first embodiment. In addition, a heavy oxygen water product containing an oxygen isotope weight component at a high concentration can be obtained.

12 and 13 show a distillation apparatus used for carrying out another embodiment of the method for producing heavy oxygen water of the present invention, and the apparatus shown here includes a plurality of distillation columns A _{1 to} A. oxygen distillation column unit F ₁ for oxygen distillation with _n , water distillation column unit F ₂ for water distillation with a plurality of distillation columns A ′ ₁ to A′n, and between these units F ₁ and F ₂ Is provided with a hydrogenation reaction apparatus 300A. The configuration of the distillation apparatus shown in FIG. 10 can be adopted for the distillation column units F ₁ and F ₂ .

Hydrogenation reaction device 300A shown in FIG. 13, the buffer tank 341 which stores concentrate through the oxygen distillation column unit F ₁ (oxygen gas) temporarily a path 342 for guiding the oxygen gas in the buffer tank 341, not shown The main configuration is a combustor 300 having a path 343 for introducing hydrogen (or deuterium) supplied from a supply source, a combustion chamber 344 for reacting oxygen and hydrogen supplied from these paths 342 and 343, and a controller 345. It is an element.

  The combustion chamber 344 includes a burner 344a that mixes and burns oxygen and hydrogen supplied into the combustion chamber 344, a heater 344b that ignites the oxygen / hydrogen mixed gas, and a cooling coil that cools a reaction product (water vapor). 344c. Reference numeral 344d denotes an outlet for taking out the reaction product (water) in the combustion chamber 344 through a valve.

  The controller 345 adjusts the flow rate control valve 342b based on a signal based on a preset value and a signal based on the oxygen gas flow rate detected by the oxygen flow rate detector 342a provided in the path 342, and passes through the path 342 to the combustion chamber 344. The supply amount of oxygen gas supplied into the inside can be adjusted. Further, the controller 345 adjusts the flow rate control valve 343b based on a signal based on a preset value and a signal based on the hydrogen flow rate detected by the hydrogen flow rate detector 343a provided in the path 343, and the combustion chamber is passed through the path 343. The supply amount of hydrogen supplied into 344 can be adjusted. Reference numerals 342c and 343c denote check valves, reference numerals 342d and 343d denote backfire preventers, and reference numeral 344e denotes a discharge path for discharging a very small amount of unreacted gas in the combustion chamber 344 through the valve.

Hereinafter, an embodiment of the method for producing heavy oxygen water according to the present invention will be described by taking the case of using the distillation apparatus as an example. The raw material oxygen is supplied to the oxygen distillation column unit F ₁ to obtain an intermediate product gas 110 ′ that is a concentrate obtained by concentrating oxygen isotopic components. This intermediate product gas 110 ′ (oxygen gas) is introduced into the combustor 300 of the hydrogenation reactor 300A through the path 44 and the control valve 44a. The oxygen gas introduced into the combustor 300 is introduced into the combustion chamber 344 through the buffer tank 341, the passage 342, and the burner 344a. At the same time, hydrogen supplied from a supply source (not shown) is supplied into the combustion chamber 344 through the path 343 and the burner 344a.

  At this time, the controller 345 performs calculation based on a signal based on the set value and a feedback signal based on the oxygen gas flow rate detected by the oxygen flow rate detector 342a, and the flow rate adjustment valve 342b is adjusted by the resulting signal, Similarly, calculation is performed by a signal based on a set value from the controller 345 and a feedback signal based on the hydrogen flow rate detected by the hydrogen flow rate detector 343a, and the flow rate control valve 343b is adjusted by the resulting signal to generate water. The oxygen and hydrogen in an amount close to the stoichiometric amount for is supplied into the combustion chamber 344 via the burner 344a.

  As described above, the oxygen and hydrogen supplied to the combustion chamber 344 are always controlled to have a flow rate close to the stoichiometric amount by the feedback control as described above, but the excessively introduced gas is still discharged through the valve through the valve 344e. Are periodically discharged to prevent the gas from accumulating in the combustion chamber 344. In order to further reduce the amount of exhaust gas, it is preferable to employ more strict control means such as using feedforward control together.

The oxygen and hydrogen supplied into the combustion chamber 344 are mixed in the burner 344a, then jetted into the combustion chamber 344, ignited by the heater 344b, and reacted to generate water. Produced water, after which most condensed by cooling by the cooling coil 344 c, are led out to the outer combustion chamber 344 through the outlet 344d, via the path 45 is introduced into the water distillation column unit F ₂ as produced water 113. Since this produced water 113 is obtained by using the intermediate product gas 110 ′, which is a concentrate of oxygen isotope weight components, as raw material, it becomes heavy oxygen water containing a large amount of oxygen isotope weight components.

Since the water distillation column unit F ₂ has the same configuration as that of the oxygen distillation column unit F ₁ , the generated water in the distillation column unit F ₂ is the same as the concentration process of the oxygen isotope component in the unit F ₁ . The heavy components in 113, that is, H ₂ ¹⁷ O, H ₂ ¹⁸ O, D ₂ ¹⁷ O, D ₂ ¹⁸ O, DH ¹⁷ O, and DH ¹⁸ O are concentrated and recovered as product heavy oxygen water 114.

  In the distillation apparatus of the present embodiment, the start-up time can be shortened as in the first embodiment described above. In addition, a heavy oxygen water product containing an oxygen isotope weight component at a high concentration can be obtained.

Figure 14 illustrates another embodiment of the distillation apparatus of the present invention, the apparatus shown here, the distillation column A ₁ to A _n of the n, near the top of these columns A ₁ to A _n a condenser _B 1 .about.B _n provided, the evaporator _C 1 -C _n provided in the vicinity of the bottom of the tower _a 1 to a _n, the k column (1 ≦ k ≦ (n- 1)) of Introducing paths D _{1 to} D _n−1 connecting the outlet of the k-th tower evaporator C _k provided near the tower bottom and the top of the (k + 1) _-th tower, and the (k + 1) _-th tower of the (k + 1) _-th tower Return routes E _{1 to} E _n-1 connecting the outlet of the condenser B _{k + 1} and the bottom of the k-th tower, and an isotope scrambler 47 are provided.

The isotope scrambler 47 is for further concentrating the oxygen isotope concentrate concentrated by the towers A _{1 to} A _h by oxygen isotope scrambling, and the inlet side is connected to the h-th tower A _h via the extraction path 48. Connected to the lower part, the outlet side is connected to the middle part of the i-th tower A _i adjacent to the rear stage side of the h-th tower A _h via a return path 49.

As an isotope scrambler 47, there is an isotope scrambler 47 that uses an isotope exchange reaction catalyst, and an oxygen molecule that is once converted into another compound and then decomposed to obtain an oxygen molecule. Isotopically scrambler 47, when used as the former, by contacting the bottom gas column A _h is a heavy oxygen isotopes concentrate isotope exchange reaction catalyst, in a concentrate isotopes to be described later The body exchange reaction can be promoted, whereby the concentration of heavy component oxygen molecules in the concentrate can be further increased.

In this case, the isotope scrambler 47 includes a catalyst cylinder (not shown) and an isotope exchange reaction catalyst filled therein. As this isotope exchange reaction catalyst, for example, a catalyst containing one or more selected from the group consisting of W, Ta, Pd, Rh, Pt, and Au can be used. In addition to the above, the isotope exchange reaction catalyst is Ti oxide, Zr oxide, Cr oxide, Mn oxide, Fe oxide, Co oxide, Ni oxide, Cu oxide, Al oxide, Si oxidation A material including one or more selected from the group consisting of an oxide, a Sn oxide, and a V oxide can also be used. In addition, it is also possible to use a mixture of the above-mentioned single metal catalyst and the above-mentioned metal oxide catalyst in one kind or plural kinds.

Isotopically scrambler 47, the case of using the latter ones, once another compound bottom gas column A _h is a heavy oxygen isotopes concentrate is converted to (e.g. water), then decomposing this oxygen Obtaining molecules further increases the concentration of heavy oxygen molecules in the concentrate. An example of an isotope scrambler 47 employing this method is shown in FIG.

  In FIG. 15, the isotope scrambler 47 mainly comprises an argon circulation blower 87, a catalyst cylinder 88 filled with an oxidation reaction catalyst, an electrolyzer 89, and an oxygen purifier 90. As the oxidation reaction catalyst filled in the catalyst cylinder 88, for example, a catalyst containing one or more selected from the group consisting of Pd, Pt, Rh, Ru, Ni, Cu and Au can be used. Furthermore, it is composed of a catalyst in which Pd, Pt, Rh, Ru, etc. are supported on Al oxide, Si oxide, Ti oxide, Zr oxide, Cr oxide, V oxide, Co oxide, Mn oxide, etc. What contains 1 type or 2 or more types selected from the group can also be used.

  The argon circulation blower 87 is provided to circulate the gas in the argon circulation system including the catalyst cylinder 88, the cooler 91, and the chiller 92. Since oxygen and hydrogen coexist in the circulation system, an argon supply line 98 for supplying argon for diluting the gas in the system is connected to the circulation system in consideration of the explosion range. This circulation system is provided with a hydrogen gas supply line 97 in order to keep the hydrogen concentration at the outlet of the chiller 92 at about 2%.

Next, an embodiment of the oxygen isotope enrichment method of the present invention will be described by taking the case of using the above apparatus as an example. The feed 101 through path 20 and fed to the first column A _1, below, was concentrated heavy oxygen isotopes according to the process described above while reaching the tower A _h, obtaining a bottom liquid of column A _h is concentrate . Next, this tower bottom liquid is introduced into the isotope scrambler 47 as the lead-out gas 115 through the path 48.

The oxygen gas supplied from the path 48 to the suction side of the argon circulation blower 87 is mixed with argon and hydrogen, and the pressure is increased to about 80 to 100 kPa (gauge) by the blower 87 and introduced into the catalyst cylinder 88. Further, a very small amount of hydrogen (reaction removed by a catalyst cylinder 95 described later) is replenished from a line 97 at the outlet of the blower 87. Hydrogen and oxygen react in the catalyst cylinder 88 (2H ₂ + O ₂ → 2H ₂ O) to produce water, and the composition at the outlet of the catalyst cylinder 88 is about 2% hydrogen, about 0.5% water vapor, and about 97.5 argon. %.

  The mixed gas is cooled by a cooler 91 and a chiller 92, and water is separated into a storage tank 93. This water is sent to the electrolytic cell 94 (pressure 400 kPa gauge) by a pump provided in the electrolyzer 89 and electrolyzed, and again, hydrogen gas containing a trace amount of oxygen and oxygen gas containing a trace amount of hydrogen. Separated. The former hydrogen gas is recovered in the argon circulation system. A trace amount of hydrogen, water, and the like are removed from the latter oxygen gas by an oxygen purifier 90 equipped with a catalyst cylinder 95 and an adsorber 96, led out through a path 49, and returned to the oxygen distillation column. For the regeneration gas of the adsorber 96, in order to prevent the loss of oxygen gas enriched in oxygen isotope weight components, an extra-high purity oxygen gas (a gas having the same specifications as the feed gas in the first distillation column) is used. Note that the flow rate of the isotope scrambler-returning oxygen gas 116 is extremely small compared to the amount of rising gas in the distillation column to which the oxygen gas is returned. It does not affect.

  Looking at the entire apparatus of the isotope scrambler 47, the gas outlet is a line 49 of purified isotope scrambler-return gas 116 and ultra-high purity oxygen supplied separately for the regeneration of the adsorber 96. Since there is only a gas discharge port, other gases circulate in the apparatus and there is almost no gas loss. Therefore, the amount of hydrogen gas and argon gas replenished from the replenishment line is extremely small.

In the catalyst cylinder 88 of the isotope scrambler 47, hydrogen and oxygen react with an oxidation reaction catalyst to generate water. For example, when A, B, C, and D are any isotope atoms of ¹⁶ O, ¹⁷ O, and ¹⁸ O,
2H ₂ + AB → H ₂ A + H ₂ B
Or 2H ₂ + CD → H ₂ C + H ₂ D
Or 2H ₂ + AA → 2H ₂ A
As a result of such reactions, the atoms that made up the oxygen molecule are separated into separate water molecules. The abundance ratio of each oxygen isotope component in the reaction product (water molecule) obtained here is determined by the abundance ratio of each isotope component in the derived gas 115. Further, in the electrolysis device 89 of the isotope scrambler 47, water molecules are decomposed into oxygen molecules and hydrogen molecules by electrolysis. Similarly, if A, B, C, and D are any isotope atoms of ¹⁶ O, ¹⁷ O, and ¹⁸ O,
H ₂ A + H ₂ C → 2H ₂ + AC
Or H ₂ B + H ₂ D → 2H ₂ + BD
Or 2H ₂ C → 2H ₂ + CC
As a result, water molecules are decomposed into oxygen molecules and hydrogen molecules. The combination of oxygen atoms constituting the oxygen molecules obtained here is stochastically determined by the abundance ratio of oxygen isotope components present in the water molecules. Note that when a plurality of types of isotope molecules exist as described above, the random change of the atoms of each molecule by each molecule is called isotope scrambling, and a device that performs this is called an isotope scrambler.

When a method using an isotope exchange reaction catalyst is used as the isotope scrambler 47, the isotope exchange reaction is performed by the isotope exchange reaction catalyst in the catalyst cylinder of the isotope scrambler 47. An isotope exchange reaction is a reaction in which a partner atom in a diatomic molecule is exchanged with another atom on a sufficiently heated catalyst surface. That is, the isotope exchange reaction is, for example, when A, B, C, and D are any isotope atoms of ¹⁶ O, ¹⁷ O, and ¹⁸ O.
AB + CD = AC + BD
Or AB + CD = AD + BC
It is a reaction that becomes. Focusing on a certain isotope atom, after a sufficient amount of time has passed, the isotope atom that is the partner as a molecule will be stochastically determined by the abundance ratio of each isotope component before starting the isotope exchange reaction . Therefore, the abundance ratio of each isotope component in the reactant (oxygen isotope molecule) obtained by the isotope exchange reaction by the isotope scrambler 47 is determined by the abundance ratio of each isotope component in the derived gas 115. become.

That is, for example, if the derived gas 115 has components of ¹⁶ O ¹⁶ O, ¹⁶ O ¹⁷ O, and ¹⁶ O ¹⁸ O, and the respective mole fractions are Y ₁₁ , Y ₁₂ , and Y ₁₃ , any of the above methods can be used. Even if it is used, the combination of oxygen atoms constituting the oxygen molecule is changed randomly depending on the existence probability of each isotope component by the isotope scrambler 47, so the concentration of each component after isotope scrambling is
_{^{16 O 16 O: (Y 11}} + Y 12/2 + Y 13/2) 2 ··· (i)
_{^{16 O 17 O: (Y 11}} + Y 12/2 + Y 13/2) Y 12 ··· (ii)
_{^{16 O 18 O: (Y 11}} + Y 12/2 + Y 13/2) Y 13 ··· (iii)
_{^{17 O 17 O: Y 2 12}} /4 ··· (iv)
_{^{17 O 18 O: Y 12 Y}} 13/2 ··· (v)
¹⁸ O ¹⁸ O: Y ² 13/4 (vi)
It becomes.

Some of ¹⁶ O contained in the ¹⁶ O ^{17 O,} 16 ^{O 18} O is accompanied to the ¹⁶ O ¹⁶ O, heavy component ⁽¹⁷ O and ¹⁸ O) of oxygen molecules ^{(18 O} 18 consisting only of O, ¹⁷ O ¹⁸ O and ¹⁷ O ¹⁷ O (hereinafter referred to as heavy component oxygen molecules) are increased.

Reactant concentration is increased in heavy components oxygen molecules isotopically scrambler 47 is supplied to the column A _i via path 49 as isotope scrambler return gas 116, below, through the tower A _i to A _n. Since the heavy component oxygen molecule has a high boiling point and is easy to concentrate, the concentration of the oxygen isotope component is further increased in this process.

In the oxygen isotope enrichment method of the above-described embodiment example, the start-up time can be shortened as in the above-described first embodiment example. Further, the oxygen isotope weight component concentrate obtained by the towers A _{1 to} A _h is supplied to the isotope scrambler 47, and isotope scrambler 47 in the isotope scrambler 47 performs heavy component oxygen molecules ( ^{18 O 18 O, 17 O 18 O} , and ¹⁷ O ¹⁷ O) concentration increased, by supplying the concentrate to the column _a i to a _n, since further increase the concentration of heavy oxygen isotopes, high heavy oxygen isotopes Products containing in concentration can be obtained.

In the illustrated apparatus, the outlet side path 49 of the isotope scrambler 47 is connected to the i-th tower _Ai . Thus, tower outlet passage 49 of the isotope scrambler 47 is connected, it is more desirable than the h column A _h of the inlet-side path 48 is connected is of a downstream side (second-stage) In the present invention, the present invention is not limited to this, and the tower to which the outlet side path 49 is connected may be a tower to which the inlet side path 48 is connected, or an upstream side (front stage side) of this tower.

That is, the isotope scrambler 47 can be incorporated in any part of the “apparatus composed of a plurality of distillation columns” configured in a cascade. For example, gas is extracted from an arbitrary place of the k-th column (including distillation column, condenser, reboiler, piping, etc.), treated with an isotope scrambler, and the j-th column (including distillation column, condenser, reboiler, piping, etc.) It is also possible to return to an arbitrary place. Here, the magnitude relationship between k and j is free, and there is a case where k = j. However, in order to effectively perform isotope scrambling, the position where the gas is extracted from the distillation apparatus is preferably the position where ¹⁶ O ¹⁸ O is most concentrated, and the position where the gas is returned to the distillation column after isotope scrambling. , rather than the concentration of ¹⁸ O ¹⁸ O in extracting position, since the larger the concentration of ¹⁸ O ¹⁸ O in the gas after the isotope scrambling, subsequent ^{(18 O 18} O than where the extracted is more concentrated Position).

In the present invention, deoxygenated water can also be obtained by supplying oxygen derived from the final tower _An to the hydrogenation reactor 300A and converting it into water.

  Next, a description will be given of the results of computer simulation in the case where the oxygen isotopic component is concentrated using each distillation apparatus. The distillation theory employed in the design of the distillation column of the present invention and the distillation theory employed in this simulation use a kinetic model for mass transfer. E. T.A. P (Height Equivalent to a Theoretical Plate) or equilibrium stage model is not used.

In the distillation theory using this kinetic model, the mass flux N is expressed as follows using the diffusion flux J and the convection term ρv.
N = J _GS + ρ _GS v _GS ω _GS
In addition, the following can be listed as a correlation equation related to mass transfer.
Sh _GS (J ^GS / N) = A ₁ ReG ^A2 · Sc _GS ^A3
Here, Sh, Re, and Sc are respectively defined by the following equations.
Sh _GS = Nd / (ρ _GS D _GS Δω _GS )
_{Re G = ρ G U G d} / μ G
Sc _GS = μ _GS / (ρ _GS D _GS )
N: Mass flux [kg / (m ² · s)]
J: Diffusion flux [kg / (m ² · s)]
d: equivalent diameter [m]
D: Diffusion coefficient [m ² / s]
ρ: Density [kg / m ³ ]
v: Speed [m / s]
ω: Concentration [kg / kg]
Sh: Sherwood number [-]
Re: Reynolds number [-]
Sc: Schmitt number [-]
Subscript G: Gas phase Subscript S: Gas-liquid interface

The goodness of this kinetic model is that it can accurately predict the mass transfer of intermediate components in a multicomponent system, the Merfree efficiency that occurs when calculations are performed using the equilibrium stage model, and the H.P. E. T. T. For example, P may not be an unrealistic result that takes a negative value. For the above model, see J.H. A. Wesselingh: 'Non-equilibrium modelling of distillation' IChemE Distillation A n d Absorption '97, vol. 1, pp. 1-21 (1997).

[Example 1]
Table 2 shows the results of simulation using the model described above when oxygen isotopes are concentrated using the distillation apparatus shown in FIG. The device specifications are shown in Table 1.

[Conventional example 1]
Table 2 also shows the results of simulations performed when oxygen isotopes are concentrated using the conventional distillation apparatus shown in FIG. This conventional apparatus assumed that the tower diameter and packing height of the first to third towers were the same as those of the apparatus of Example 1. The feed amount, product amount, reflux ratio, and the like were also set to the same values as in Example 1.

From Table 2, it can be seen that the method of Example 1 using the apparatus of FIG. 1 can increase the ¹⁶ O ¹⁸ O concentration of the product as compared with the method of Conventional Example 1 using the conventional apparatus. This is considered to be because the pressure in the column can be lowered in the case of Example 1 as compared with the conventional example 1, and therefore the vapor pressure ratio between the components in the column is increased and the distillation performance is improved. It is done.

  Table 2 also shows that in Example 1, the startup time of the apparatus can be shortened. This is considered to be due to the following reason. In Conventional Example 1, most of the piping that is a liquid supply path between the first tower and the second tower and between the second tower and the third tower is filled with the liquid, whereas in the first example, Then, between the first tower and the second tower, the pipes (return paths 14 and 15), which are liquid supply paths from the second tower to the first tower and from the third tower to the second tower, are filled with the liquid. This is because there is only a small portion corresponding to the liquid head corresponding to the pressure difference between the tower bottom and the tower top between the second tower and the third tower. For this reason, in Example 1, the liquid hold-up amount is reduced, and the startup time of the apparatus can be shortened.

When Example 1 and Conventional Example 1 were compared, the result of the liquid holdup of the ¹⁶ O ¹⁸ O component in the liquid supply pipe was superior to that of Conventional Example 1 in Example 1. In particular, when the tower diameter is smaller than those of Example 1 and Conventional Example 1, it is considered that the diameter of the liquid supply pipe is relatively large. Therefore, the liquid hold-up of the entire apparatus between the apparatus of the present invention and the conventional apparatus is reduced. The difference is considered to be large, and it is considered that the superiority of the device of the present invention is further clarified in terms of the startup time. Further, in the case where oxygen isotope enrichment is performed using a distillation column using an irregular packing instead of the regular packing used in Example 1, compared with Example 1, the ¹⁶ O ¹⁸ O component The liquid hold-up amount is considered to be about three times or more. This is because the liquid hold-up amount is 2-3% of the volume of the packed bed in the case of regular packing, but 10-20% in the case of irregular packing. Thus, when the regular packing is used, the liquid hold-up amount can be reduced, so that the start-up time can be greatly shortened.

Moreover, since the method of the first embodiment does not use a liquid pump, no power is required to operate it. Other effects obtained by not using the liquid pump include the following.
(1) Device / equipment costs are reduced.
(2) Since there is no switching to the backup liquid pump accompanying the maintenance of the liquid pump, the apparatus can be continuously operated stably.
(3) The operating cost of the liquid pump can be reduced.
(4) By reducing the intrusion heat by the liquid pump, the operating cost for cold replenishment (nitrogen cycle etc.) can be reduced.
On the other hand, the amount of heat exchange between the condenser and the evaporator in each column is larger in the present embodiment than in the conventional example, which is disadvantageous in terms of operation cost. This is because in the present invention, the liquid fed from the first tower to the second tower and the second tower to the third tower in the conventional apparatus is once gasified by the evaporator and then liquefied by the condenser. Moreover, it is because the gas which was returned from the second tower to the first tower and from the third tower to the second tower in the conventional apparatus is once liquefied by the condenser and then gasified by the evaporator. This point is a compensation for obtaining the advantage of lowering the distillation tower top pressure, eliminating the need for a liquid pump in the present invention, but this demerit is in comparison with the merit in comparison with the conventional method employing the liquid pump. Much smaller.

[Example 2]
Table 4 shows the result of performing a simulation in the case of using the distillation apparatus shown in FIG. 1 and producing heavy oxygen water using water as a raw material. Table 3 shows the apparatus specifications.

[Conventional example 2]
Table 4 also shows the results of simulation in the case of using the conventional distillation apparatus shown in FIG. 19 and producing heavy oxygen water using water as a raw material. In Conventional Example 2, the column diameter, packing height, feed amount, product amount, reflux ratio, etc. of the first to third columns were set to the same values as in Example 2.

From Table 4, it can be seen that the method of Example 2 using the apparatus of FIG. 1 can increase the H ₂ ¹⁸ O concentration of the product as compared with the method of Conventional Example 2 using the conventional apparatus. Moreover, in Example 2, it turns out that the amount of liquid holdups becomes small and the starting time of an apparatus can be shortened.

[Example 3]
Table 7 shows the result of simulation when heavy oxygen water is produced using the distillation apparatus shown in FIG. Oxygen distillation column unit F ₁ has ten distillation columns, water distillation column unit F ₂ was assumed to have a five distillation columns. The apparatus specifications of the oxygen distillation column unit F ₁ are shown in Table 5, and the apparatus specifications of the water distillation column unit F ₂ are shown in Table 6.

From Table 7, it can be seen that according to Example 3, heavy oxygen water in which the oxygen isotopic component ( ¹⁸ O) is concentrated to 97% or more can be obtained. In this Example 3, an annual production amount of about 60 kg is obtained, and the start-up time of the apparatus is about 140 days when the distillation column unit F ₁ for oxygen concentration and the distillation column unit F ₂ for water distillation are combined. I understand that. As in the third embodiment, as the example in which the concentration of using water distillation heavy oxygen isotopes ⁽¹⁸ O) is described in _{US patent 5057225, Thode, Smith,} A n d Walking : CA _n ad. J. et al. Res. There are those reported in 22,127 (1944), in this example, the cascade process consisting of three distillation columns, heavy oxygen isotopes ⁽¹⁸ O) was concentrated to 1.3% water 150g was obtained It has been reported. In this conventional example, the time required for startup is 120 days, and considering the productivity, it can be seen that the startup time can be significantly reduced in Example 3 as compared with the conventional example.

[Example 4]
Table 9 shows the results of simulation when the oxygen isotope component ( ¹⁸ O) is concentrated using the distillation apparatus shown in FIG. FIG. 16 shows the concentration distribution of each isotope component in each tower. It was assumed that the number (n) of distillation columns was 10, and the isotope scrambler 47 was installed between the sixth and seventh columns. Table 8 shows the apparatus specifications. In the table, the isotope scrambler supply gas refers to the derived gas 115 supplied to the isotope scrambler 47 through the path 48, and the isotope scrambler return gas is derived from the isotope scrambler 47, and the path 49 It refers to isotope scrambler return gas 116 to be supplied to the column a _i through.

Table 9 shows that according to Example 4, a concentrate obtained by concentrating the oxygen isotope weight component ( ¹⁸ O) to 97% or more can be obtained. In Example 4, it can be seen that a production amount of about 12 kg per year is obtained, and the startup time of the apparatus is 73 days.

In the apparatus shown in this embodiment, the flow rate of ¹⁸ O ¹⁸ O accompanying the product gas is
[Product gas flow rate] × [ ¹⁸ O ¹⁸ O concentration in product gas] = 1 × 10 −5 (mol / s) × 0.941 = 9.4 × 10 −6 (mol / s)
It is. On the other hand, the flow rate of ¹⁸ O ¹⁸ O accompanying the feed gas and supplied into the apparatus is
[Feed gas flow rate] × [ ¹⁸ O ¹⁸ O concentration in feed gas] = 0.3 (mol / s) × 4.2 × 10 −6 = 1.3 × 10 −6 (mol / s) Much smaller than the flow rate of ¹⁸ O ¹⁸ O entrained by the gas. In the present embodiment example, an isotope scrambler is provided to compensate for the shortage of ¹⁸ O ¹⁸ O. That is, by treating oxygen gas which is concentrated (preferably be 45% or more) ^{16 O} 18 ^O in the distillation column is a high concentration of an isotope scrambler, to generate a new ^{18 O} 18 ^O, by again returned to the distillation column it can be taken a number of ^{18 O} 18 ^O than the amount of ^{18 O} 18 ^O supplied with feed gas as a product. In this embodiment, as can be seen from Table 9, the isotope scrambler generates ¹⁸ O ¹⁸ O in an amount represented by the following formula.
[Isotope scrambler-treatment amount] × [[ ¹⁸ O ¹⁸ O outlet concentration] − [ ¹⁸ O ¹⁸ O inlet concentration]] = 6.0 × 10 −4 × [0.177−0.162] = 9. 0x10-6 (mol / s)

When this is combined with ¹⁸ O ¹⁸ O, 1.3 × 10 ⁻⁶ (mol / s) supplied by the feed gas, the total ¹⁸ O ¹⁸ O supplied to the distillation column is 10.3 × 10 ^−6. Therefore, it becomes possible to collect 9.4 × 10 ⁻⁶ (mol / s) of ¹⁸ O ¹⁸ O according to the product. If an isotope scrambler is not provided, the amount of feed gas must be at least (9.4 × 10 ⁻⁶ ) / (1.3 × 10 ⁻⁶ ) = 7.2 times or more. Accordingly, a distillation column having a large column diameter is required. This is not preferable from the viewpoint of holdup and start-up time. That is, in the apparatus shown in the present embodiment, by providing an isotope scrambler, it is possible to collect a product enriched with oxygen isotope weight with an apparatus having a smaller tower diameter than before.

[Example 5]
Table 10 shows the results of performing the distillation of oxygen stable isotopes by simulation using an apparatus in which exactly the same process as the apparatus of FIG. 1 is employed and the number of distillation columns is increased to 16 columns. Table 11 shows the specifications of this distillation apparatus.

This example is a case where the total height of the distillation column is increased for the purpose of obtaining a product in which ¹⁶ O ¹⁷ O, which is an intermediate component, is concentrated. FIG. 17 shows the composition distribution of each oxygen isotope in the tower. In this example, since a peak of ¹⁶ O ¹⁷ O appears in the vicinity of the tenth to twelfth towers, at least one of these towers A ¹⁶ O ¹⁷ O concentrated product can be obtained by collecting liquid or gas from the solution. In this example, gas was sampled as product gas 1 from the bottom (reboiler outlet) of the eleventh column. Further, the gas derived from the bottom of the sixteenth column was collected as product gas 2. In this example, the concentration of ¹⁶ O ¹⁷ O in the product 1 is about 50%, but if the total height of the distillation column is further increased, more concentrated ¹⁶ O ¹⁷ O can be obtained.

In this embodiment, the feed supplies oxygen purified to 99.999% or more to the first column. ¹⁶ O ¹⁷ O in the feed is 738 ppm and ¹⁶ O ¹⁸ O is 4070 ppm. Product gas 1 is collected from the bottom of the eleventh tower. If this product gas 12 is treated with a hydrogenation device in order to convert it into water, which is a normal usage form, heavy oxygen water having a ¹⁷ O concentration of about 25% can be obtained. Product gas 2 is collected from the bottom of the 16th tower. If this is treated with a hydrogenation device, heavy oxygen water having an ¹⁸ O concentration of about 48% can be obtained.

^{If no 17} O enriched product is required and only a product gas that is ¹⁶ O ¹⁸ O enriched gas is needed, the total height of the distillation can be much smaller than in this example. In that case, the composition at the peak of ¹⁶ O ¹⁷ O is about 1%. That is, paying attention to the composition distribution of ¹⁶ O ¹⁸ O in FIG. 17, the gradient of the composition is small from the first tower to the vicinity of the sixth tower, and in order to concentrate ¹⁶ O ¹⁷ O to a high concentration, In the embodiment, the total height is increased more than necessary for the ¹⁶ O ¹⁸ O component. That is, it can be seen that if the total filling height is increased, the intermediate component can be concentrated by the apparatus of the present invention.

1, 2, 3, A _{1 to An} ... distillation column 5, 7, 9, ... condenser 6, 8, 10 ... evaporator 11 ... regular packing 12, 13, 35, 36, D _{1 to} D _n-1 ... introduction path 14, 15, 37, 38, 37 ', 38', E _{1 to} E _n-1 ... return path 41, 42 ... blower 47 ...・ Isotope scramblers 51, 52... Non-self-distribution promoting regular packing 53, 54, 55 .. self-distribution promoting regular packing 300A.

Claims (4)

An apparatus for distilling and separating a gas or a liquid composed of a plurality of components using a plurality of distillation columns (first column to n-th column) configured in a cascade,
The outlet of the evaporator provided at or near the bottom of the k-th column (1 ≦ k ≦ (n−1)), and the condenser provided at or near the top of the (k + 1) -th column. An inlet path connecting the inlet or the middle of the tower, the condenser outlet of the (k + 1) th tower, the inlet of the evaporator provided near the tower bottom of the k-th tower, the tower bottom of the tower or the tower A return path for connecting the intermediate section is provided, and a valve for returning the condensate from the condenser outlet of the (k + 1) th tower to the kth tower by its own weight is provided in the return path. A distillation apparatus characterized by. When concentrating raw material oxygen containing oxygen isotope components by a cascade process comprising a plurality of distillation columns (first column to nth column),
At least part of the gas at the outlet of the evaporator provided at the bottom of the k-th tower (1 ≦ k ≦ (n−1)) or near the bottom of the tower is placed near the top of the (k + 1) -th tower or near the top of the tower. At least part of the liquid at the top of the (k + 1) th tower or at the condenser outlet of the tower is supplied to the condenser inlet provided or the middle part of the tower as the return liquid by its own weight as the return liquid. Oxygen molecules ¹⁶ O ¹⁷ O, ¹⁶ O ¹⁸ O, ¹⁷ O ¹⁷ O, ¹⁷ O ¹⁸ O, and ¹⁸ O containing oxygen isotope components by returning to the evaporator inlet of the k tower, the bottom of the tower, or the middle of the tower ^A method for concentrating oxygen isotopes, comprising concentrating at least one of ¹⁸ O.   The oxygen isotope concentrate concentrated by the enrichment method of claim 2 is subjected to oxygen isotope scrambling to obtain a concentrate in which the concentration of at least one oxygen molecule containing the oxygen isotope component is further increased. To enrich oxygen isotopes.   The oxygen isotope concentrate concentrated by the concentration method of claim 2 is subjected to oxygen isotope scrambling to obtain a concentrate having an increased concentration of at least one oxygen molecule containing the oxygen isotope component, A method for concentrating oxygen isotopes, further comprising obtaining a concentrate obtained by further increasing the concentration of at least one oxygen molecule containing said oxygen isotope component by the method of claim 2.

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