JP6913772B2 - Stable isotope concentrator - Google Patents

Description

The present invention relates to a stable isotope concentrator.

Methods for separating stable isotopes that are present in a very small amount in nature include thermal diffusion separation, centrifugation, laser separation, chemical exchange separation, and distillation separation. Among these, distillation separation is suitable for mass production of isotopes of light elements. For example, as an industrial stable isotope separation method for oxygen, it is adopted for distillation separation of water, distillation separation of oxygen, and the like.

A characteristic of stable isotope separation by distillation is that it has a long start-up time. The start-up time is the time required for the concentration distribution up to the product concentration to be formed in the entire distillation column, and is the time from the start of operation of the apparatus to the collection of the product. An element that contributes to the start-up time is the amount of liquid hold-up. Concentration of stable isotopes has a problem that the production cost is high due to the long start-up time.

Another feature of stable isotope separation by distillation is that the separation coefficient is extremely close to 1, and several thousand theoretical plates are required to obtain a high-concentration stable isotope. Since the height of the distillation column is limited, it is necessary to divide the distillation column into a plurality of distillation columns and connect these plurality of distillation columns in series. Since stable isotopes have a small natural abundance ratio, the amount of product recovered is very small compared to the amount of raw material supplied. Therefore, among the plurality of distillation columns, the column diameter of the column that supplies the raw material is the largest, and the concentration of the product in the column increases as it approaches the terminal column that becomes the recovery section / concentration section. Can be made smaller (step cascade). As a result, not only the equipment cost is reduced, but also the liquid hold-up amount is reduced, which leads to a reduction in the start-up time.

In Patent Document 1, in a packed stable isotope concentrator by distillation, a packed tower filled with a regular packing is adopted as a packed tower with a small amount of liquid hold-up in order to shorten the start-up time. As a result, the liquid hold-up amount is further reduced, and the start-up time is shortened successfully.

Japanese Unexamined Patent Publication No. 11-188240

On the other hand, in order to reduce the tower diameter, it is necessary to provide a condenser and a reboiler in the tower whose diameter is smaller than that of the front tower, respectively, and the power increases as the number of the condenser and the reboiler increases. As described above, in order to shorten the start-up time, it is necessary to increase the power required for the capacitor and the reboiler, and there is a problem that the shortening of the start-up time and the reduction of the equipment cost and the electric power are in a trade-off relationship. ..

The present invention has been made in view of the above problems, and an object of the present invention is to provide a stable isotope concentrator having an excellent balance between shortening the start-up time and reducing equipment cost and electric power.

In order to achieve the above problems, the present invention adopts the following configuration.
[1] A stable isotope concentrator that concentrates stable isotopes by distillation.
A group of distillation columns in which multiple distillation columns are connected in series,
A raw material supply line that supplies raw materials to one of the distillation columns,
The distillation column group includes a product out-licensing line for out-licensing a product from another distillation column located on the secondary side of the one distillation column.
A stable isotope concentrator in which the one distillation column is a shelf column and the other distillation column is a packed column.
[2] The distillation column group is
A group of shelf columns consisting of one or more shelf columns including the one distillation column, and
It has a packed column group consisting of one or more distillation columns including the other distillation columns, and has.
The stable isotope concentrator according to the above [1], wherein the packed tower group is located on the secondary side of the shelf column group.
[3] The stable isotope concentrator according to the above [1] or [2], wherein the shelf column has a bottom concentration of a stable isotope to be enriched, which is equal to or higher than the natural abundance ratio and is 20 atomic% or less. ..

The stable isotope concentrator of the present invention has an excellent balance between shortening the start-up time and reducing equipment cost and electric power.

It is a system diagram which shows the main part of the stable isotope concentrator which concerns on embodiment of this invention. It is a system diagram which shows the stable isotope enrichment apparatus which concerns on the test example of this invention. It is a system diagram which shows the stable isotope enrichment apparatus which concerns on the test example of this invention.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings, showing embodiments.
In the drawings used in the following description, in order to make the features easier to understand, the featured parts may be enlarged for convenience, and the dimensional ratios of each component may not be the same as the actual ones. do not have.

<Stable isotope concentrator>
FIG. 1 is a system diagram showing a main part of a stable isotope concentrator according to an embodiment of the present invention.
The stable isotope concentrator 100 of the present embodiment includes a group of distillation columns in which a plurality of distillation columns are connected in series (cascade method), a plurality of capacitors 21, a plurality of reboilers 22, a raw material supply line 30, and a product. It includes a lead-out line 31 and.

Hereinafter, the nth distillation column from the upstream end of the distillation column group is referred to as the nth distillation column.
The first distillation columns 1 to n are cascade-connected in the order of column numbers.
The first distillation column 1 to the nth distillation column n concentrates the stable isotope having a low boiling point on the top side of the column by distilling the cooled stable isotope at a low temperature, and the stable isotope having a high boiling point on the bottom side of the column. It is designed to concentrate stable isotopes. The first distillation column to which the raw material is supplied has the largest diameter, and the diameter gradually decreases toward the end.

The first distillation column 1 to the j-1 distillation column j-1 is a distillation column provided with a shelf step (hereinafter, referred to as a "shelf step tower"), and the jth distillation column j to the jth Each of the distillation columns n of n is a distillation column (hereinafter, referred to as “filling column”) filled with a regular packing.
In FIG. 1, among the first distillation columns 1 to n, the first distillation column (one distillation column) which is a shelf column and is supplied with stable isotopes as a raw material. Only the distillation column 1, the first distillation column j that switches from the shelf column to the filling column, and the nth distillation column n that is the column for collecting products (other distillation columns) are shown. ..

By the way, as described above, there are mainly two types of distillation columns, a shelf column and a packed column, each of which has the following characteristics.

(Characteristics of the shelf tower)
・ Equipment cost: Cheap when the tower diameter is large ・ Pressure loss: Large ・ Liquid hold-up amount: Large ・ Stage interval: About 100 mm for distillation columns such as air separation devices

(Characteristics of packed tower)
・ Equipment cost: Cheap when the tower diameter is small ・ Pressure loss: Small ・ Liquid holdup amount: Small ・ HETP (theoretical stage equivalent height): About 200 mm with high distillation performance

In the conventional stable isotope concentrator, a packed column having a small liquid hold-up amount is often used from the viewpoint of shortening the start-up time (for example, Patent Document 1).
On the other hand, by adopting a shelf column, if the comparison is made at the same tower height, the shelf column can earn about twice the number of theoretical plates, and two distillation columns are used as one. This makes it possible to reduce equipment costs and power. On the other hand, there is concern that the startup time will be prolonged.

However, as described above, the start-up time is the time required for the concentration distribution up to the product concentration to be formed in the entire distillation column, so that the concentration distribution in the distillation column has a small difference from the natural abundance ratio of stable isotopes. If it is a part, that is, a tower that supplies raw materials, or a tower that is close to a tower that supplies raw materials, it is expected that the time until the concentration distribution is formed is short. Further, the tower that supplies the raw material or the tower that is adjacent to the tower that supplies the raw material requires a large amount of power because the tower diameter is large, and the fact that the two towers in this portion can be combined into one tower greatly contributes to power reduction.

Therefore, in the stable isotope concentrator 100 of the present embodiment, among the plurality of distillation columns connected in cascade, at least a shelf column is adopted as a column for supplying raw materials, and a regular packed bed is used in a column other than the shelf column. Adopt a packed filling tower.

Specifically, as described above, the first distillation column 1 to the j-1 distillation column j-1 is a shelf column, and the jth distillation column j to the nth distillation column n It is a packed tower. That is, the stable isotope concentrator 100 of the present embodiment includes a shelf column group composed of one or more shelf columns (first distillation column 1 to j-1 distillation column j-1) and one or more shelf column towers. It has a packed column group consisting of packed columns (jth distillation column j to nth distillation column n). The shelf column group is located on the primary side, and the packed tower group is located on the secondary side. Further, the shelf column group includes a first distillation column 1 for supplying raw materials, and a packed column group includes an nth distillation column n for collecting (deriving) a product.

Here, the stable isotope concentrator 100 of the present embodiment uses a shelf column in each distillation column in the range where the bottom concentration of the stable isotope to be enriched is in the range of the natural abundance ratio to 20%. That is, in the first distillation column 1 to the j-1 distillation column j-1, the concentration of the stable isotope to be concentrated is equal to or higher than the natural abundance ratio and is 20 atomic% or less. Then, in the j-th distillation column j in which the column bottom concentration of the stable isotope to be enriched exceeds 20 atomic%, the shelf column is switched to the packed column.

The tower for supplying the raw material does not necessarily have to be the first tower, and a distillation column serving as a recovery unit may be located in front of the tower for supplying the raw material.
Further, the tower for collecting products does not necessarily have to be the final tower (nth tower), and may be in the middle of the distillation column group.
Further, it is desirable that the step spacing of the shelf column is about 100 mm, and it is not suitable that the step spacing is wider than the HETP of the filling.

The capacitors 21 are provided in one or every several columns for each distillation column (first distillation column 1 to nth distillation column n).
The condenser 21 is provided on a circulation line 32 in which both ends are connected at different positions on the top of each distillation column. The condenser 21 has a function of liquefying the gas that has risen in the distillation column by heat exchange and lowering the inside of the distillation column again.

The reboiler 22 is provided in one or every few columns for each distillation column.
The reboiler 22 is provided on a circulation line 33 in which both ends are connected at different positions on the bottom of each distillation column. The reboiler 22 has a function of vaporizing the liquid that has descended in the distillation column by heat exchange and raising the inside of the distillation column again.

One end of the raw material supply line 30 is connected to the intermediate portion of the first distillation column 1. The raw material supply line 30 is a route for supplying a stable isotope to the intermediate portion of the first distillation column (one distillation column) 1. The raw material supply line 30 is provided with a valve.
The middle portion of the distillation column indicates a position other than the top and bottom of the distillation column.
The purity of the stable isotope supplied from the raw material supply line 30 is preferably as high as 99.999% or more.

Except for the final column, a part of the steam at the bottom of each distillation column in which the concentration of the heavy component of the stable isotope is increased is supplied to the top of the next column via the valve 23 by the path 34. The driving force of the flow is the pressure difference between the bottom of a distillation column and the top of the next column. The steam supplied to the top of the next tower is liquefied by the condenser 21 together with the rising steam in the tower, and is returned to the top of the tower.

Further, except for the first distillation column 1, a part of the reflux liquid near the top of each distillation column in which the concentration of the light component of the stable isotope was increased is passed through the valve 24 by the route 35 to the front column. It is supplied to the bottom of the tower. The driving force of the flow is the head pressure of the reflux liquid. The reflux liquid supplied to the bottom of the front tower is vaporized by the reboiler 22 together with the reflux liquid in the tower, and is returned to the bottom of the tower.

The product derivation line 31 is a route for deriving the concentrated stable isotope component from the nth distillation column (another distillation column) n as a product. One end of the product lead-out line 31 is connected to a portion of the nth distillation column n near the bottom of the column. The product is a stable isotope component concentrated to a high concentration (eg, 99% or more).

As described above, according to the stable isotope concentrator 100 of the present embodiment, the shelf column is adopted as at least the first distillation column 1 for supplying the raw materials among the plurality of cascade-connected distillation columns. A packed tower filled with a regular packing is adopted in a tower other than the shelf column. As a result, the stable isotope concentrator 100 of the present embodiment has an excellent balance between shortening the start-up time and reducing the equipment cost and the electric power.

Although the stable isotope concentrator of the present invention has been described above with reference to embodiments, the present invention is not limited to these embodiments. Each configuration in the above embodiment and a combination thereof are examples, and the configuration can be added, omitted, replaced, and other changes can be made without departing from the spirit of the present invention.

For example, the stable isotope concentrator 100 of the present embodiment may be configured to include a heat medium fluid circulation line that circulates the heat medium fluid through a plurality of capacitors 21. Heat exchange may be performed in each capacitor 21 by the heat medium fluid circulating in the heat medium fluid circulation line.

Further, the stable isotope concentrator 100 of the present embodiment may be configured to include a heat medium fluid circulation line that circulates the heat medium fluid via a plurality of reboilers 22. The heat exchange may be performed in each reboiler 22 by the heat medium fluid circulating in the heat medium fluid circulation line.

Hereinafter, the present invention will be described in detail with reference to Test Examples, but the present invention is not limited thereto.

(Test Example 1-1)
^{In Test Example 1-1, 18} O was concentrated using the stable isotope concentrator 200 shown in FIG.
The stable isotope concentrator 200 has the same basic configuration as the stable isotope concentrator 100. The distillation column group is composed of 12 distillation columns, the first distillation column 1 is a shelf column, and the second to twelfth distillation columns 2 to 12 are packed columns filled with a regular packed material. Liquefied nitrogen is used as the cold source of the condenser, and liquefied nitrogen is supplied to each condenser from the liquefied nitrogen supply line 38. Gas nitrogen is used as the heat source of the reboiler, and gas nitrogen is supplied to each reboiler from the gas nitrogen supply line 39. Further, the stable isotope concentrator 200 includes an isotope scrambler 20. The isotope concentrated gas extraction line 36 has one end connected to the intermediate portion of the ninth distillation column 9 and the other end connected to the isotope scrambler 20, and extracts a part or all of oxygen to extract an isotope. It is designed to be supplied to the scrambler 20. The oxygen that has undergone the isotope exchange reaction in the isotope scrambler 20 is returned from the isotope concentrated gas return line 37 to the intermediate portion of the ninth distillation column 9.

The flow rate and composition of the raw material high-purity oxygen to be supplied are as shown in Table 1.
The step spacing of the first distillation column 1 was set to 100 mm.
Further, as the filling of the second distillation column to the twelfth distillation column 12, the one having a HETP of 200 mm was adopted.

^{When the apparatus was stable, the abundance ratio of 18} O in the oxygen gas delivered from the bottom of the first distillation column 1, which is the final column of the shelf column, was 0.9 atomic%.
The abundance ratio of stable isotope molecules of oxygen gas delivered from the bottom of the 12th distillation column 12 is as shown in Table 2.
The total heat exchange amount of the capacitor and the reboiler was 1480 kW. The start-up time of the stable isotope concentrator 200 was 150 days. As a result, the amount of electric power required for startup was 5328 MW · h.

(Test Example 1-2)
^{In Test Example 1-2, 18} O was concentrated using the stable isotope concentrator 300 shown in FIG.
The stable isotope concentrator 300 is substantially the same as the stable isotope concentrator 200 except that the number of distillation columns is 13, and the first distillation column 1 is a packed column filled with a regular packed material. The isotope scrambler 20 is connected to the middle portion of the tenth distillation column 10.
As the packed material of the first filling column 1 to the thirteenth distillation column 13, a packed bed having a HETP of 200 mm was adopted.
The flow rate and composition of the raw material high-purity oxygen to be supplied are as shown in Table 1 in the same manner as in the stable isotope concentrator 200.

The abundance ratio of stable isotope molecules of oxygen gas delivered from the bottom of the thirteenth distillation column 13 when the apparatus was stabilized was as shown in Table 3.
The total heat exchange amount of the capacitor and the reboiler was 2020 kW. The start-up time of the stable isotope concentrator 300 was 149 days, and the amount of electric power required for start-up was 7223 MW · h.

(Verification 1)
In Test Example 1-1, the product concentration and start-up time were the same as those in Test Example 1-2.
On the other hand, in Test Example 1-1, the required heat exchange amount could be reduced by about 30% as compared with Test Example 1-2, and the required number of towers could be reduced by one.
From this result, it was found that according to Test Example 1-1 of the present invention, the equipment cost and the power can be reduced without prolonging the start-up time.

(Test Example 2-1)
In Test Example 2-1, it is composed of 10 distillation columns, the first distillation column to the third distillation column 3 are shelf columns, and the fourth distillation column to the tenth distillation column 10 are regularly filled. ¹⁸ O was enriched using a stable isotope concentrator, which is a packed column filled with material. It is almost the same as the stable isotope concentrator 200 except that the total number of distillation columns and the number of shelf columns and packed columns are different.
The flow rate and composition of the raw material high-purity oxygen to be supplied are as shown in Table 1 in the same manner as in the stable isotope concentrator 200.

^{When the apparatus was stable, the abundance ratio of 18} O in the oxygen gas delivered from the bottom of the third distillation column 3, which is the final column of the shelf column, was 19.4 atomic%.
The abundance ratio of stable isotope molecules of oxygen gas delivered from the bottom of the tenth distillation column 10 is as shown in Table 4.
The total heat exchange amount of the capacitor and the reboiler was 1315 kW. The start-up time was 168 days, and the amount of electric power required for start-up was 5302 MW · h.

(Test Example 2-2)
In Test Example 2-2, it is composed of nine distillation columns, the first distillation column to the fourth distillation column 4 are shelf columns, and the fifth distillation column to the ninth distillation column 9 are regularly filled. ¹⁸ O was enriched using a stable isotope concentrator, which is a packed column filled with material. It is almost the same as the stable isotope concentrator 200 except that the total number of distillation columns and the number of shelf columns and packed columns are different.
The flow rate and composition of the raw material high-purity oxygen to be supplied are as shown in Table 1 in the same manner as in the stable isotope concentrator 200.

^{When the apparatus was stable, the abundance ratio of 18} O in the oxygen gas delivered from the bottom of the fourth distillation column 4, which is the final column of the shelf column, was 49.7 atomic%.
The abundance ratio of stable isotope molecules of oxygen gas delivered from the bottom of the ninth distillation column 9 is as shown in Table 5.
The total heat exchange amount of the capacitor and the reboiler was 1285 kW. The start-up time was 194 days, and the amount of electric power required for start-up was 5983 MW · h.

(Verification 2)
It was found that increasing the number of shelf towers used increases the startup time, and if the shelf towers are used in the range where the concentration of the bottom of the object to be concentrated is up to 20%, the power until startup is reduced. did it.
On the other hand, when the shelf column was used in the range where the concentration of the bottom of the object to be concentrated exceeded 20 atomic%, the power until activation increased as in Test Example 2-2. In addition, since the diameter of the distillation column in the latter stage is smaller, the equipment cost that can be reduced is also smaller.
From this result, it was found that in the present invention, it is desirable to use the shelf column in the range where the concentration of the bottom of the object to be concentrated is up to 20 atomic%.

The above results are applicable not only to oxygen but also to other stable isotopes. For example, even in the stable isotope enrichment of carbon and hydrogen, if the number of shelves used is increased, the start-up time will be extended, and the shelves can be concentrated in the range where the concentration of the bottom of the object to be enriched is up to 20 atomic%. If used, the power to start can be reduced.

The present invention is a distillation apparatus for distilling a cryogenic fluid, and uses a distillation apparatus including a group of distillation columns in which a plurality of distillation columns are cascaded, and a stable isotope atom that exists in a very small amount in nature. It is applicable to a stable isotope concentrator for concentrating.

1, j-1, j, n ... Distillation column 21 ... Condenser 22 ... Ribola 30 ... Raw material supply line 31 ... Product lead-out line 100-700 ... Stable isotope concentrator

Claims (2)

A stable isotope concentrator that concentrates stable isotopes by distillation.
A group of distillation columns in which multiple distillation columns are connected in series,
A raw material supply line that supplies raw materials to one of the distillation columns,
Among the distillation column group, and a product outlet line for deriving a product from another distillation column located downstream than the one distillation column,
The one distillation column is a shelf column ,
Before Symbol other distillation column is a packed column,
The distillation column group includes a shelf column group composed of one or more shelf columns including the one distillation column, and a packed column group composed of one or more distillation columns including the other distillation columns.
A stable isotope concentrator in which the packed column group is located after the shelf column group. The stable isotope concentrator according to claim 1 , wherein the shelf column has a bottom concentration of a stable isotope to be enriched, which is equal to or higher than the natural abundance ratio and is 20 atomic% or less.

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