JP7792314B2 - Oxygen isotope enrichment device and oxygen isotope enrichment method - Google Patents

Description

The present invention relates to an oxygen isotope enrichment device and a method for enriching oxygen isotopes.

Stable isotopes are generally used as tracers in the fields of natural science and medicine, but the natural abundance of some stable isotopes is low, and many of them require significant enrichment before use.

For example, when stable oxygen isotopes are used as tracers in the fields of natural science and medicine, concentrations on the order of 100% are required. The natural abundances of oxygen-17 ( ¹⁷ O) and oxygen-18 ( ¹⁸ O) are 0.038% and 0.205%, respectively, and a concentration factor of about 10 to 1000 times is required.

Methods for enriching and separating oxygen isotopes are known, for example, from Patent Document 1, Patent Document 2, and Non-Patent Document 1.
The separation of isotopes by photoreaction described in Patent Document 1 is characterized by a large separation factor compared to other separation methods, but the enrichment factor is at most about 10 times, and a multi-stage process is required to achieve a high enrichment factor.

One example of such a multi-stage process is the cascade connection of the enrichment process disclosed in Patent Document 2 and the multi-stage process disclosed in Non-Patent Document 1. Figure 3 shows the configuration of a conventional oxygen isotope enrichment device equipped with a multi-stage process.

3, the conventional oxygen isotope enrichment apparatus 100 includes a plurality of apparatus groups k, k+1. Specifically, each of the apparatus groups k, k+1 includes an ozone generator 11 that generates ozone (O ₃ ) from oxygen (O ₂ ), and an ozone generator 12 that converts carbon tetrafluoride (CF ₄ an oxygen separation device 12 that separates oxygen from a mixture of oxygen, ozone, and carbon tetrafluoride; an ozone photolysis device 13 that irradiates the mixture of ozone and carbon tetrafluoride with light to selectively decompose ozone containing a specific oxygen isotope into oxygen; a collection device 14 that collects a mixed gas containing ozone, carbon tetrafluoride, and oxygen; an enrichment device 15 that separates the mixed gas containing ozone, carbon tetrafluoride, and oxygen into oxygen and a mixed gas of ozone and carbon tetrafluoride and enriches the oxygen isotope in the oxygen; an ozone removal device 18 that decomposes ozone from the mixed gas of ozone and carbon tetrafluoride to produce oxygen; and a carbon tetrafluoride separation device 19 that separates carbon tetrafluoride from a mixed gas of carbon tetrafluoride and oxygen. The oxygen isotope concentrating apparatus 100 is provided with an oxygen supply path 16 between the device group k and the next device group k+1, which introduces oxygen separated in the kth concentrating device 15 into the (k+1)th ozone generating device 11'. As shown in Figure 3, the (k+1)th device and path have the same configuration as the kth device and path, with "'" added after the reference numeral.

The enrichment method using the conventional oxygen isotope enrichment apparatus 100 includes a plurality of process groups k and k+1. Specifically, each of the process groups k and k+1 includes an ozone generation step of generating ozone (O ₃ ) from oxygen (O ₂ ), and a step of adding carbon tetrafluoride (CF ₄ The method for enriching oxygen isotopes includes a carbon tetrafluoride supply step for supplying ozone, ozone, and carbon tetrafluoride, an oxygen separation step for separating oxygen from a mixture of oxygen, ozone, and carbon tetrafluoride, an ozone photolysis step for irradiating the mixture of ozone and carbon tetrafluoride with light to selectively decompose ozone containing a specific oxygen isotope into oxygen, a collection step for collecting a mixed gas containing ozone, carbon tetrafluoride, and oxygen, an enrichment step for separating the mixed gas containing ozone, carbon tetrafluoride, and oxygen into oxygen and a mixed gas of ozone and carbon tetrafluoride and enriching the oxygen isotope in the oxygen, an ozone abatement step for decomposing ozone from the mixed gas of ozone and carbon tetrafluoride to produce oxygen, and a carbon tetrafluoride separation step for separating carbon tetrafluoride from the mixed gas of carbon tetrafluoride and oxygen. In the method for enriching oxygen isotopes, the oxygen separated in the enrichment step of the kth group is introduced as a raw material into the (k+1)th group ozone generation step.

In this way, conventional oxygen isotope enrichment devices 100 and enrichment methods perform specific stable oxygen isotope enrichment operations continuously.

Furthermore, in the conventional oxygen isotope enrichment apparatus 100, each of the apparatus groups k and k+1 includes an ozone detoxification apparatus 18, a carbon tetrafluoride separation apparatus 19, and a carbon tetrafluoride return path 20 that returns the carbon tetrafluoride separated in the carbon tetrafluoride separation apparatus 19 to the carbon tetrafluoride supply apparatus 17 of any of the preceding process groups.
The conventional oxygen isotope enrichment apparatus 100 is provided with an oxygen exhaust path 25 for discharging oxygen separated in the carbon tetrafluoride separation device 19 to the outside of the system in any step group k, and with an oxygen return path 21′ for introducing oxygen separated in the carbon tetrafluoride separation device 19 into the ozone generator 11 in the preceding step group k in any step group k+1.
As described above, the conventional oxygen isotope enrichment device 100 and enrichment method are configured to reuse oxygen and carbon tetrafluoride.

International Publication No. 2007/020934 Japanese Patent Application Laid-Open No. 2008-080200

Nuclear Chemical Engineering by Hiroshi Yamamoto, Akira Kanagawa, and Kunio Higashi, published in 1976 by Nikkan Kogyo Shimbun

However, with the conventional oxygen isotope enrichment apparatus 100 and enrichment method shown in Figure 3, in order to reuse oxygen and carbon tetrafluoride, an ozone detoxification device 18 and a carbon tetrafluoride separation device 19 must be installed in each equipment group, and an ozone detoxification step and a carbon tetrafluoride separation step must be performed in each process group, resulting in a complex equipment configuration and number of processes.

Furthermore, with the conventional oxygen isotope enrichment apparatus 100 and enrichment method, there was a problem in that the amount of oxygen processed in the ozone generator 11 and ozone generation step increased in any of the equipment groups and process groups.

The present invention was made in consideration of the above circumstances, and aims to provide an oxygen isotope enrichment device and method that simplify the device configuration and processing steps in a multi-stage process in which stable oxygen isotope enrichment processes are configured in a cascade, and that can reduce the amount of oxygen processed.

In order to solve the above problems, the present invention has the following configuration.
[1] An ozone generator that generates ozone from oxygen;
a carbon tetrafluoride supply device located on the secondary side of the ozone generator and supplying carbon tetrafluoride to the mixture of oxygen and ozone;
an oxygen separator located on the secondary side of the carbon tetrafluoride supply device and separating oxygen from a mixture of oxygen, ozone, and carbon tetrafluoride;
an ozone photolysis device located on the secondary side of the oxygen separation device, which irradiates a mixture of ozone and carbon tetrafluoride with light to selectively decompose ozone containing a specific oxygen isotope into oxygen;
a collector located on the secondary side of the ozone photolysis device and configured to collect a mixed gas containing ozone, carbon tetrafluoride, and oxygen;
a plurality of device groups (first group to nth group) each having an enrichment device located on the secondary side of the collection device, which separates a mixed gas containing ozone, carbon tetrafluoride, and oxygen into oxygen and a mixed gas of ozone and carbon tetrafluoride, and enriches oxygen isotopes in the oxygen;
one or more oxygen supply paths for introducing oxygen separated in the kth (1≦k≦(n−1)) concentrator into the (k+1)th ozone generator;
and one or more mixed gas return paths for introducing a mixed gas of ozone and carbon tetrafluoride separated in any jth group (2≦j≦n) of the concentrating devices into any one of the first group to the (j-1)th group.
[2] The oxygen isotope enrichment device according to [1], further comprising an ozone concentration measuring device located in the mixed gas return path and measuring the ozone concentration in the mixed gas return path.
[3] One or more device groups, excluding any j-th group (2≦j≦n),
an ozone detoxification device located on the secondary side of the concentrator and configured to decompose ozone from a mixed gas of ozone and carbon tetrafluoride to generate oxygen;
The oxygen isotope enrichment device according to [1] or [2], further comprising: a carbon tetrafluoride separation device located on the secondary side of the ozone detoxification device and separating carbon tetrafluoride from a mixed gas of carbon tetrafluoride and oxygen.
[4] an ozone generating step of generating ozone from oxygen;
a carbon tetrafluoride supplying step of supplying carbon tetrafluoride to a mixture of unreacted oxygen and ozone;
an oxygen separation step of separating oxygen from a mixture of oxygen, ozone, and carbon tetrafluoride;
an ozone photolysis step in which a mixture of ozone and carbon tetrafluoride is irradiated with light to selectively decompose ozone containing a specific oxygen isotope into oxygen;
a collecting step of collecting a mixed gas containing undecomposed ozone, carbon tetrafluoride, and oxygen;
a concentration step of separating a mixed gas containing undecomposed ozone, carbon tetrafluoride, and oxygen into oxygen and a mixed gas of ozone and carbon tetrafluoride, and enriching oxygen isotopes in the oxygen,
The oxygen separated in the kth group (1≦k≦(n−1)) of the concentration step is used in the (k+1)th group of ozone generation steps,
A method for enriching oxygen isotopes, wherein a mixed gas of ozone and carbon tetrafluoride separated in the enrichment step of any jth group (2≦j≦n) is returned to any one of the first to (j−1)th groups of steps.
[5] The method for enriching oxygen isotopes according to [4], wherein the ozone concentration in the mixed gas of ozone and carbon tetrafluoride separated in the enrichment step of any j-th group (2≦j≦n) is monitored when the mixed gas is returned to any one of the first to (j−1)-th groups.
[6] One or more process groups, excluding any jth group (2≦j≦n),
an ozone detoxification step of generating oxygen by decomposing ozone from a mixed gas of ozone and carbon tetrafluoride after the concentration step;
The method for enriching oxygen isotopes according to [4] or [5], further comprising a carbon tetrafluoride separation step of separating carbon tetrafluoride from a mixed gas of carbon tetrafluoride and oxygen after the ozone removal step.

The oxygen isotope enrichment apparatus of the present invention simplifies the apparatus configuration and enables a reduction in the amount of oxygen processed in a multi-stage process in which stable oxygen isotope enrichment processes are configured in cascade.
Furthermore, the oxygen isotope enrichment method of the present invention simplifies the processing steps in a multi-stage process in which stable oxygen isotope enrichment processes are configured in a cascade, and makes it possible to reduce the amount of oxygen processed.

1 is a system diagram showing the configuration of an oxygen isotope enrichment device according to one embodiment of the present invention. 1 is a system diagram showing the configuration of an oxygen isotope enrichment device applied to an embodiment of the present invention. FIG. 1 is a system diagram showing the configuration of a conventional oxygen isotope enrichment device.

An oxygen isotope enrichment device, which is one embodiment of the present invention, will be described in detail below with reference to the drawings. Note that the drawings used in the following description may show characteristic parts enlarged for convenience in order to make the features easier to understand, and the dimensional proportions of each component may not necessarily be the same as in reality.

<Oxygen isotope enrichment device>
First, an oxygen isotope enrichment apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 is a system diagram showing an example of the configuration of the oxygen isotope enrichment apparatus according to this embodiment.
1, the oxygen isotope enrichment apparatus 1 of this embodiment includes a plurality of device groups (first to nth groups, where n is an integer of 2 or more). For convenience, only device group k and device group k+1 (1≦k≦(n−1)) are shown in FIG.

Equipment group k and equipment group k+1 each include an ozone generator 11, a carbon tetrafluoride supply device 17, an oxygen separator 12, an ozone photolysis device 13, a collector 14, and a concentrator 15. As shown in Figure 1, the components of the (k+1)th group of devices and pathways that have the same configuration as those of the kth group of devices and pathways are designated with an "'" after the reference numeral, and their description will be omitted.

The ozone generator 11 generates ozone from oxygen, using raw oxygen supplied from an oxygen supply source (not shown) or concentrated oxygen supplied from a group of upstream devices via an oxygen supply path 16. The ozone generator 11 generates ozone from oxygen by discharging electricity from electrodes equipped with a high-frequency power supply, or by irradiating the oxygen with ultraviolet light from a mercury lamp. The generated ozone is discharged from the ozone generator 11 as a mixture of oxygen and ozone.

The carbon tetrafluoride supply device 17 is located on the secondary side of the ozone generator 11 and supplies carbon tetrafluoride to the mixture of oxygen and ozone discharged from the ozone generator 11. After carbon tetrafluoride has been supplied, the mixture is introduced into the downstream oxygen separator 12.

The oxygen separator 12 is located on the secondary side of the ozone generator 11 and carbon tetrafluoride supply device 17, and separates oxygen from the mixture of oxygen, ozone, and carbon tetrafluoride. Specifically, the oxygen separator 12 separates oxygen by distillation or using an adsorbent such as silica gel. The separated and recovered oxygen is returned to the upstream ozone generator 11 via path 10 for reuse.

The ozone photolysis device 13 is located on the secondary side of the oxygen separation device 12 and irradiates the mixture of ozone and carbon tetrafluoride extracted from the oxygen separation device 12 with light to selectively decompose ozone containing specific oxygen isotopes into oxygen. The ozone photolysis device 13 uses a light source with a specific wavelength range to decompose ozone molecules containing specific oxygen isotopes.

Specific ozone molecules include, for example, ¹⁶ O ¹⁶ O ¹⁷ O, ¹⁶ O ¹⁶ O ¹⁸ O, ¹⁶ O ¹⁷ O ¹⁷ O, ¹⁶ O ¹⁸ O ¹⁸ O, and ¹⁶ O ¹⁷ O ¹⁸ O.

Furthermore, examples of light sources with specific wavelength ranges include sunlight spectroscopy, InGaAsP-based semiconductor lasers or light-emitting diodes, AlGaInP-based semiconductor lasers or light-emitting diodes, GaAsSb-based semiconductor lasers or light-emitting diodes, CdZnTe-based semiconductor lasers or light-emitting diodes, CdZnSe-based semiconductor lasers or light-emitting diodes, and dye lasers that can be optically pumped with mercury lamps, YAG lasers, Ar ion lasers, Kr ion lasers, etc.

In the ozone photolysis device 13, it is preferable to maintain a low temperature (e.g., in the range of 100 to 250 K) in the area where the mixture of ozone and carbon tetrafluoride flows in order to suppress the natural decomposition of ozone.

The collector 14 is located on the secondary side of the ozone photolysis device 13 and collects the mixed gas containing ozone, carbon tetrafluoride, and oxygen that is discharged from the ozone photolysis device 13. An example of the collector 14 is a double-tube condenser that continuously liquefies and collects the mixed gas.

The concentrator 15 is located on the secondary side of the collector 14 and separates the mixed gas containing ozone, carbon tetrafluoride, and oxygen discharged from the collector 14 into oxygen and a mixed gas of ozone and carbon tetrafluoride, thereby concentrating oxygen isotopes in the oxygen. Specifically, the concentrator 15 separates the oxygen by distillation or using an adsorbent such as silica gel.

The oxygen isotope enrichment device 1 of this embodiment includes multiple device groups (first group to nth group, where n is an integer of 2 or greater), with the number of device groups preferably being 2 to 10, and more preferably being 2 to 5.

The oxygen isotope enrichment apparatus 1 of this embodiment also includes one or more oxygen supply paths 16 that introduce oxygen separated in the kth (1≦k≦(n-1)) enrichment apparatus 15 into the (k+1)th ozone generator 11'. This allows the oxygen isotope enrichment apparatus 1 of this embodiment to continuously enrich a specific stable oxygen isotope.

Furthermore, the oxygen isotope enrichment apparatus 1 of this embodiment is equipped with one or more mixed gas return paths 23 that introduce the mixed gas of ozone and carbon tetrafluoride separated in the enrichment device 15 in any jth (2≦j≦n) device group into any of the first to (j-1)th groups preceding the jth group. Specifically, as shown in FIG. 1 , the k+1th group is equipped with a mixed gas return path 23' that introduces the mixed gas of ozone and carbon tetrafluoride separated in the enrichment device 15' into the kth oxygen separation device 12.

The oxygen isotope enrichment apparatus 1 of this embodiment is equipped with a mixed gas return path 23', so that undecomposed ozone that was not decomposed into oxygen in the (k+1)th ozone photolysis apparatus 13' can be reused as a mixed gas of ozone and carbon tetrafluoride. Therefore, oxygen generated on the secondary side of the enrichment apparatus 15' constituting the (k+1)th apparatus group is not supplied to the kth ozone generator 11, thereby reducing the amount of oxygen processed by the ozone generator 11.

The mixed gas return path 23' is a path located between the concentrator 15' in the k+1th equipment group and the oxygen separator 12 in the first equipment group. Note that, since selective decomposition of non-isotopes by ozone in the mixed gas return path 23' results in a decrease in isotope enrichment, it is preferable to form an oxide film in advance on the inside of the piping that makes up the mixed gas return path 23' using high-concentration ozone or the like to suppress ozone decomposition due to metal catalytic reactions on the inner surface of the piping. It is also preferable to maintain the mixed gas return path 23' at a low temperature (for example, in the range of 100 to 250 K) to suppress natural decomposition of ozone.

An ozone concentration measuring device 22' is located in the mixed gas return path 23'. This device measures the ozone concentration in the mixed gas of ozone and carbon tetrafluoride flowing through the mixed gas return path 23'. This allows the ozone concentration in the mixed gas return path 23' to be monitored and maintained within a safe concentration range.

The ozone concentration measuring device 22' is not particularly limited, but a device that uses light absorption, such as ultraviolet spectroscopy, is preferred because ozone is less likely to be altered.

Furthermore, in the oxygen isotope enrichment apparatus 1 of this embodiment, one or more device groups, excluding any jth group (2≦j≦n), have an ozone detoxification device 18 and a carbon tetrafluoride separation device 19. In other words, any jth device group (2≦j≦n) does not have an ozone detoxification device 18 or a carbon tetrafluoride separation device 19.

Specifically, as shown in FIG. 1, the kth equipment group includes an ozone detoxification device 18 and a carbon tetrafluoride separation device 19. The k+1th equipment group does not include an ozone detoxification device 18 or a carbon tetrafluoride separation device 19.

The ozone detoxification device 18 is located on the secondary side of the concentrator 15 and generates oxygen by decomposing ozone from the mixed gas of ozone and carbon tetrafluoride discharged from the concentrator 15. The ozone detoxification device 18 performs ozone decomposition at room temperature. Specifically, a catalyst is used to lower the activation energy of the ozone self-decomposition reaction, thereby decomposing the ozone.

The carbon tetrafluoride separation device 19 is located on the secondary side of the ozone abatement device 18 and separates carbon tetrafluoride from the mixed gas of carbon tetrafluoride and oxygen discharged from the ozone abatement device 18. Specifically, the carbon tetrafluoride separation device 19 separates the mixed gas of carbon tetrafluoride and oxygen into carbon tetrafluoride and oxygen by distillation or using an adsorbent such as silica gel.

The carbon tetrafluoride separated by the carbon tetrafluoride separation device 19 is returned via a line 20 to the carbon tetrafluoride supply device 17 at the previous stage for reuse.
The oxygen separated by the carbon tetrafluoride separator 19 can be extracted via an oxygen exhaust line 25 .

According to the oxygen isotope enrichment apparatus 1 of this embodiment, the kth device group has an ozone detoxification device 18 and a carbon tetrafluoride separation device 19, while the k+1th device group does not have an ozone detoxification device 18 or a carbon tetrafluoride separation device 19, thereby simplifying the device configuration.

<Method for enriching oxygen isotopes>
Next, a method for enriching oxygen isotopes according to one embodiment of the present invention will be described in detail using the above-described oxygen isotope enrichment apparatus 1 as an example.
The method for enriching oxygen isotopes according to this embodiment includes a plurality of step groups (first to nth groups, where n is an integer of 2 or greater). For convenience, this embodiment shows only step group k and step group k+1 (1≦k≦(n−1)).

Process group k and process group k+1 each include an ozone generation step, a carbon tetrafluoride supply step, an oxygen separation step, an ozone photolysis step, a capture step, and a concentration step.

In the ozone generation step, ozone is generated from oxygen in the ozone generator 11 using raw oxygen supplied from an oxygen supply source (not shown) or concentrated oxygen supplied from a group of devices in the preceding stage via the oxygen supply path 16. The generated ozone is discharged from the ozone generator 11 as a mixture of oxygen and ozone.

In the carbon tetrafluoride supply step, carbon tetrafluoride is supplied to the mixture of oxygen and ozone obtained in the ozone generation step. The mixture after carbon tetrafluoride has been supplied is used in the subsequent oxygen separation step.

In the oxygen separation step, oxygen is separated from the mixture of oxygen, ozone, and carbon tetrafluoride in the oxygen separation device 12. The separated and recovered oxygen is reused in the preceding ozone generation step.

In the ozone photolysis step, the mixture of ozone and carbon tetrafluoride obtained in the oxygen separation step is irradiated with light in the ozone photolysis device 13 to selectively decompose ozone containing specific oxygen isotopes into oxygen.

In the collection step, a collection device 14 is used to collect the mixed gas containing ozone, carbon tetrafluoride, and oxygen obtained in the ozone photolysis step.

In the enrichment step, the enrichment device 15 is used to separate the mixed gas containing ozone, carbon tetrafluoride, and oxygen obtained in the collection step into oxygen and a mixed gas of ozone and carbon tetrafluoride, thereby enriching oxygen isotopes in the oxygen.

The oxygen isotope enrichment method of this embodiment includes multiple process groups (first to nth groups, where n is an integer of 2 or greater), with the number of process groups preferably being 2 to 10, and more preferably being 2 to 5.

Furthermore, in the oxygen isotope enrichment method of this embodiment, the oxygen separated in the kth (1≦k≦(n-1)) enrichment step is used in the ozone generation step that constitutes the (k+1)th process group. This allows the oxygen isotope enrichment method of this embodiment to continuously perform enrichment operations for specific stable oxygen isotopes.

Furthermore, in the oxygen isotope enrichment method of this embodiment, in any jth (2≦j≦n) process group, the mixed gas of ozone and carbon tetrafluoride separated in the enrichment step is returned to any one of the first to (j-1)th process groups that precedes the jth process group. Specifically, in the k+1th process group, the mixed gas of ozone and carbon tetrafluoride separated in the enrichment step is introduced into the kth oxygen separation step.

According to the oxygen isotope enrichment method of this embodiment, undecomposed ozone that was not decomposed into oxygen in the (k+1)th ozone photolysis step can be reused as a mixed gas of ozone and carbon tetrafluoride. Therefore, oxygen generated on the secondary side of the enrichment step that constitutes the (k+1)th process group is not used in the kth ozone generation step, thereby reducing the amount of oxygen processed in the ozone generation step.

In the oxygen isotope enrichment method of this embodiment, the ozone concentration in the mixed gas of ozone and carbon tetrafluoride separated in any jth (2≦j≦n) enrichment step is monitored when the mixed gas is returned to any one of the first to (j-1)th process groups.

Ozone concentration can be monitored as needed. For example, when the oxygen isotope enrichment device 1 shown in Figure 1 is operating steadily, monitoring may be performed at regular intervals. Furthermore, for example, when the device is started up, when the device's condition is unstable, or when the device's operating conditions are changed, the ozone concentration may be monitored continuously.

If the ozone concentration exceeds a predetermined value, other fluids within the oxygen isotope enrichment device 1 can be introduced into the mixed gas return path 23' to dilute the ozone in the path, thereby reducing the ozone concentration.

Furthermore, in the oxygen isotope enrichment method of this embodiment, one or more process groups, excluding any jth group (2≦j≦n), include an ozone abatement step and a carbon tetrafluoride separation step. In other words, any jth group (2≦j≦n) does not include an ozone abatement step or a carbon tetrafluoride separation step.

Specifically, the kth process group includes an ozone detoxification step and a carbon tetrafluoride separation step. The k+1th process group does not include an ozone detoxification step or a carbon tetrafluoride separation step.

The ozone detoxification step uses an ozone detoxification device 18 to decompose ozone from the mixed gas of ozone and carbon tetrafluoride obtained in the concentration step to produce oxygen.

In the carbon tetrafluoride separation step, carbon tetrafluoride is separated from the mixed gas of carbon tetrafluoride and oxygen obtained in the ozone detoxification step using a carbon tetrafluoride separation device 19. Specifically, in the carbon tetrafluoride separation step, the mixed gas of carbon tetrafluoride and oxygen is separated into carbon tetrafluoride and oxygen.

The carbon tetrafluoride separated in the carbon tetrafluoride separation step is returned to the carbon tetrafluoride supply device 17 in the preceding stage via a path 20 and reused in the carbon tetrafluoride supply step.
Furthermore, the oxygen separated in the carbon tetrafluoride separation step can be extracted via the oxygen exhaust line 25 .

According to the oxygen isotope enrichment method of this embodiment, the kth process group includes an ozone detoxification step and a carbon tetrafluoride separation step, while the k+1th process group does not include an ozone detoxification step or a carbon tetrafluoride separation step, thereby simplifying the process.

The technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

The effects of the present invention will be explained below using examples, but the present invention is not limited to the configuration of the examples.

<Example>
As the oxygen isotope enrichment apparatus of the present invention, an oxygen isotope enrichment apparatus 51 shown in Fig. 2 was used. The oxygen isotope enrichment apparatus 51 shows a configuration in which two device groups (first group and second group) are used in the oxygen isotope enrichment apparatus 1 shown in Fig. 1.

(Device configuration)
The oxygen isotope enrichment device 51 has the following configuration.
Ozone generator 11: Generates ozone from raw oxygen.
Oxygen supply path 16: Located between the first group of concentrators 15 and the second group of ozone generators 11'.
Concentrated oxygen outlet path 24': connected to the second group of concentrators 15'.
Oxygen exhaust line 25: connected to the first group of carbon tetrafluoride separators 19.
Mixed gas return line 23': Located between the second group concentrator 15' and the first group oxygen separator 12.

(Ozone photolysis conditions)
Ozone photolysis devices 13, 13': Decompose specific ozone molecules ( ¹⁶ O ¹⁶ O ¹⁷ O).
Laser light: Laser light (992 nm) from an external cavity laser (manufactured by Sacher Lasertechnik, "TEC-320") was used.

When laser light is irradiated onto ozone, it separates into one oxygen molecule and one oxygen atom, as shown in equation (1) below.

The oxygen atoms produced in the reaction of formula (1) above gain energy and decompose some of the surrounding ozone molecules, as shown in formula (2). In formula (2), n is the entrainment coefficient described in the prior art document (JP 2017-223547 A).

In this example, the entrainment coefficient was set to n = 5. Meanwhile, non-selective thermal decomposition of ozone (hereinafter referred to as thermal decomposition) also occurs simultaneously, unrelated to ozone photolysis. The amount of oxygen molecules generated by thermal decomposition of ozone was calculated assuming that it was proportional to the flow rate of ozone introduced into the ozone photolysis device 13.
After the start-up of the apparatus, when the "mixed gas return line 23'" is not being used, in a steady state, the supply amount of raw material oxygen and the amount of ozone introduced into the ozone photolysis apparatus 13 are equal in terms of the number of oxygen atoms. In other words, it can be said that the amount of oxygen molecules generated by the thermal decomposition of ozone is proportional to the flow rate of raw material oxygen.

In the ozone photolysis devices 13 and 13', the decomposition rate of the target ozone molecules ( ¹⁶ O ¹⁶ O ¹⁷ O) by laser was set to 50%.

In the first group of ozone photolysis devices 13, the laser decomposition amount was 7.63×10 ⁻⁸ (mol/s) and the thermal decomposition amount was 8.96×10 ⁻⁷ (mol/s) (same conditions as in the prior art document: JP 2017-223547 A).

The flow rate of the raw material oxygen was 6.36×10 ⁻⁸ (mol/s) due to the laser decomposition amount: 7.63×10 ⁻⁸ (mol/s) and the laser decomposition rate: 50%.

From the above conditions, the flow rate of each group and the concentration of oxygen 17 ( ¹⁷ O) in the oxygen isotope enrichment device 51 of the embodiment are calculated as shown in Table 1 below.

As shown in Table 1, when raw oxygen with an 17O concentration of 0.200 (atom %) is introduced into the first ozone generator 11 using the oxygen isotope enrichment device 51, the ^17O concentration is enriched to 0.624 (atom %) in the first group and to 1.67 (atom %) in the second group.

As such, the oxygen isotope enrichment apparatus (enrichment method) 51 of the embodiment, which is configured with multiple equipment groups (process groups), has been shown to be capable of enriching the isotope components to the order of 100% even when the isotope components to be enriched in the raw oxygen are dilute.

Furthermore, according to the oxygen isotope concentrating device (concentration method) 51 shown in FIG. 2, the ozone detoxifying device and carbon tetrafluoride separating device can be omitted in the second group.
The amount of oxygen processed by the ozone generator 11 in the first group can be reduced by the amount of ozone returned by the mixed gas return path 23' provided in the second group.
Here, the reducible amount of oxygen is calculated by the following formula (3).

As explained above, it has been suggested that the oxygen isotope enrichment device (enrichment method) 51 shown in FIG. 2 can reduce the amount of oxygen processed in the first ozone generation device 11 by 5.08 (m ³ ) per year by directly reusing undecomposed ozone in the second ozone photolysis device 13′.

1, 51 Concentration devices 10, 20 Paths 11, 11' Ozone generation devices 12, 12' Oxygen separation devices 13, 13' Ozone photolysis devices 14, 14' Collection devices 15, 15' Concentration device 16 Oxygen supply paths 17, 17' Carbon tetrafluoride supply device 18 Ozone removal device 19 Carbon tetrafluoride separation device 21' Oxygen return path 22' Ozone concentration measurement device 23' Mixed gas return path 24' Concentrated oxygen extraction path 25 Oxygen exhaust path

Claims (6)

an ozone generator for generating ozone from oxygen;
a carbon tetrafluoride supply device located on the secondary side of the ozone generator and supplying carbon tetrafluoride to the mixture of oxygen and ozone;
an oxygen separator located on the secondary side of the carbon tetrafluoride supply device and separating oxygen from a mixture of oxygen, ozone, and carbon tetrafluoride;
an ozone photolysis device located on the secondary side of the oxygen separation device, which irradiates a mixture of ozone and carbon tetrafluoride with light to selectively decompose ozone containing a specific oxygen isotope into oxygen;
a collector located on the secondary side of the ozone photolysis device and configured to collect a mixed gas containing ozone, carbon tetrafluoride, and oxygen;
a plurality of device groups (first group to nth group) each having an enrichment device located on the secondary side of the collection device, which separates a mixed gas containing ozone, carbon tetrafluoride, and oxygen into oxygen and a mixed gas of ozone and carbon tetrafluoride, and enriches oxygen isotopes in the oxygen;
one or more oxygen supply paths for introducing oxygen separated in the kth (1≦k≦(n−1)) concentrator into the (k+1)th ozone generator;
and one or more mixed gas return paths for introducing a mixed gas of ozone and carbon tetrafluoride separated in any jth group (2≦j≦n) of the concentrating devices into any one of the first group to the (j-1)th group. The oxygen isotope enrichment device of claim 1, further comprising an ozone concentration measuring device located in the mixed gas return path and measuring the ozone concentration in the mixed gas return path. One or more device groups excluding any j-th group (2≦j≦n)
an ozone detoxification device located on the secondary side of the concentrator and configured to decompose ozone from a mixed gas of ozone and carbon tetrafluoride to generate oxygen;
3. The oxygen isotope enrichment apparatus according to claim 1, further comprising: a carbon tetrafluoride separation device located on the secondary side of the ozone detoxification device, which separates carbon tetrafluoride from a mixed gas of carbon tetrafluoride and oxygen. an ozone generating step of generating ozone from oxygen;
a carbon tetrafluoride supplying step of supplying carbon tetrafluoride to a mixture of unreacted oxygen and ozone;
an oxygen separation step of separating oxygen from a mixture of oxygen, ozone, and carbon tetrafluoride;
an ozone photolysis step in which a mixture of ozone and carbon tetrafluoride is irradiated with light to selectively decompose ozone containing a specific oxygen isotope into oxygen;
a collecting step of collecting a mixed gas containing undecomposed ozone, carbon tetrafluoride, and oxygen;
a concentration step of separating a mixed gas containing undecomposed ozone, carbon tetrafluoride, and oxygen into oxygen and a mixed gas of ozone and carbon tetrafluoride, and enriching oxygen isotopes in the oxygen,
The oxygen separated in the kth group (1≦k≦(n−1)) of the concentration step is used in the (k+1)th group of ozone generation steps,
A method for enriching oxygen isotopes, wherein a mixed gas of ozone and carbon tetrafluoride separated in the enrichment step of any jth group (2≦j≦n) is returned to any one of the first to (j−1)th groups of steps. The oxygen isotope enrichment method described in claim 4, wherein the ozone concentration in the mixed gas of ozone and carbon tetrafluoride separated in any jth group (2≦j≦n) of the enrichment steps is monitored when the mixed gas is returned to any one of the first to (j-1)th groups of steps. One or more process groups excluding any jth group (2≦j≦n)
an ozone detoxification step of generating oxygen by decomposing ozone from a mixed gas of ozone and carbon tetrafluoride after the concentration step;
6. The method for enriching oxygen isotopes according to claim 4, further comprising, after the ozone removal step, a carbon tetrafluoride separation step of separating carbon tetrafluoride from the mixed gas of carbon tetrafluoride and oxygen.