JP2000107549A - Method for separation of rare gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method which can separate rare gas under the environmental conditions relatively near to the normal temperature without using a distillation method. SOLUTION: After an inclusion compound is produced by charging water and gas containing rare gas into a hydration vessel 2 and by keeping the inside of the hydration vessel 2 at such a temperature and a pressure as to produce the inclusion compound out of the water and the rare gas contained in the gas, a solid phase comprised of the inclusion compound and ice is formed in the hydration vessel 2 by lowering the temperature in the hydration vessel 2 to such a level below freezing so as to make ice out of the hydration vessel 2, and after deaeration of the hydration vessel 2, the temperature inside of the hydration vessel 2 is so raised to the decomposing temperature that the rare gas can be recovered from the hydration vessel 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to, for example,
The present invention relates to a rare gas separation technology for separating and generating a rare gas contained therein.

[0002]

2. Description of the Related Art Conventionally, separation and purification of a rare gas from air is mainly performed by a distillation method.

[0003]

However, in the case of employing such a distillation method, since the object to be separated is a rare gas, a considerably low temperature state (-185.5 in the case of argon).
C., about 153.4 ° C. for krypton, and about −108.1 ° C. for xenon). Due to such factors, the system for separating noble gas requires a complicated system,
The equipment had to be enlarged. Therefore, an object of the present application is to separate a rare gas using a relatively simple apparatus under a relatively near ambient temperature environment without using a distillation method as described above. Is to get the way.

[0004]

According to the present invention, there is provided a method for separating a rare gas according to the present invention, wherein a raw material gas containing a rare gas is mixed with water. The temperature at which this rare gas and water form an inclusion compound.
It is characterized in that it is brought into direct contact under pressure to separate a rare gas as an inclusion compound. The present inventors have now found that a rare gas and water form an inclusion compound under specific temperature and pressure conditions, and have completed the present invention. In this case, even if the rare gas is in a mixed state with nitrogen or the like,
By setting the temperature and pressure conditions under which the rare gas preferentially forms the clathrate, it is possible to increase the mixing ratio of the rare gas in the clathrate, and to separate the rare gas in the form of this clathrate. can do. One method for performing the above separation work is described in claim 2
As described in the above, the rare gas and water contained in the source gas are given priority over the gas excluding the rare gas contained in the source gas. The clathrate is directly contacted under the temperature and pressure at which the clathrate is formed, thereby generating the clathrate of both, isolating the clathrate formed, and decomposing the clathrate isolated Thus, the rare gas can be separated from the clathrate. That is, an inclusion compound of a rare gas and water is formed, and the formed inclusion compound is isolated by some operation (in fact, such an inclusion compound is a sherbet in which an inclusion compound is mixed in water). Since it is obtained in the form of a sherbet, it can be isolated by simply draining water from the sherbet-like thing), and the isolated clathrate is decomposed by, for example, a temperature raising operation, a pressure reducing operation, or the like. Thus, the rare gas can be obtained in a gaseous state.

[0005] One of the methods for performing the above separating operation is as follows.
While introducing the raw material gas containing the rare gas and water into the hydration tank, the rare gas and the water contained in the raw material gas have priority over the gas excluding the rare gas contained in the raw material gas. At the temperature and pressure at which the clathrate is generated, the inside of the hydrated vessel is maintained, and after both clathrates are produced, the inside of the hydrated vessel is reduced to the freezing temperature of water or lower, After cooling and solidifying the water in the tank, a solid phase composed of the clathrate compound and ice is formed in the hydrated tank, and after the inside of the hydrated tank is degassed, the state in the tank is included. The decomposition state in which the compound decomposes, and the gas released from the hydration tank in this decomposition state is collected,
It is preferable to separate and collect the rare gas. In this separation method, a hydrate tank capable of adjusting the temperature and pressure in the tank is used. First, a source gas containing a rare gas and water are introduced into a hydration tank, and clathrates of both are formed under predetermined conditions. After that, the inside of the hydrate tank is cooled to the freezing temperature of water or less, and the water in the tank is cooled and solidified. When this operation is performed, the solid phase composed of the clathrate compound and ice and the remaining gas (this is a gas mainly composed of the raw material gas and having a reduced rare gas component) are contained in the hydration tank. It is filled with a gas phase.
In this state, when the inside of the hydrated tank is degassed, first, the residual gas is removed. Then, the state in the tank is changed to a decomposition state (increased temperature or reduced pressure) in which the clathrate is decomposed, and in this decomposition state, the gas released from the hydration tank is collected. In addition, a gas having a high rare gas concentration can be separated and recovered. In this operation, the same hydration tank can be used to perform a more efficient separation operation under the condition where water is present.

[0006] As described above, the inclusion of rare gas and water
1.5-150kgf / cm^Two Condition
It is preferable to carry out the above. Also, as a rare gas, Al
If you want to separate gon
Temperature condition within the range of 0 ° C. to 30 ° C.
150kgf / cm ^Two What to do under the conditions
Is preferred. In the case of krypton, in the same temperature range,
14.5 to 150 kgf / cm^Two , For xenon,
1.5-150kgf / cm in the same temperature range^Two To do
Is preferred. Under such pressure conditions, the algo
, Krypton and xenon form clathrates with water
In addition, since nitrogen does not form inclusion compounds,
Nitrogen, which can be an obstacle to separation, can be sufficiently separated
That's because.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the method for separating a rare gas according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the rare gas separation process of the present application. As shown in the figure, in the separation process, the rare gas is separated through a step of forming an inclusion compound of the rare gas with water. FIG. 2 shows a schematic configuration of an apparatus 1 used for performing separation through such a rare gas hydrate formation step. As shown in FIG. 1, the apparatus 1 includes a hydration tank 2 configured to be capable of introducing and discharging a source gas into and from a tank via a gas introduction path 6 according to a predetermined cycle. 2 is provided with a water tank 3 which is also configured to be capable of introducing and discharging water. The water tank 3 and the hydration tank 2 are connected by a water introduction path 5. The hydration tank 2 is configured so that the temperature and pressure in the tank can be adjusted and controlled. Further, a gas outlet path 4 connected to the gas phase side of the hydrate forming tank 2 is provided, and the gas outlet path 4 is on the downstream side, and is selectively used as a deaeration path 4a and a gas recovery path 4b. Is configured to be selectively connectable. Therefore, the configuration is such that degassing from the gas phase portion 2a of the hydration tank 2 and gas recovery of the rare gas can be performed alternatively. Here, the downstream side of the deaeration path 4a is open to the atmosphere side via a suction blower 8, and the gas recovery path 4b includes a recovery tank 7 on the downstream side.

Hereinafter, the case where the rare gas is separated and recovered by using the above-described apparatus 1 will be described step by step. 1. Water is introduced into the hydrated tank 2 from the water tank 3 via the water introduction passage 5 (a water introduction step shown in FIG. 1). 2 A source gas is introduced into the hydrated tank 2 into which water has been introduced via the gas introduction path 6 (a source gas introduction step shown in FIG. 1). In this case, the raw material gas is a gas containing a rare gas, which is air itself and a rare gas (for example, 1 gas selected from argon, xenon, and krypton).
In the case where the concentration of the above-mentioned gas is higher than the concentration of the rare gas in the air, either gas may be used. (3) The temperature and pressure in the hydration tank 2 in which the raw material gas and water are mixed are set so that the rare gas and water form an inclusion compound. Although the temperature and pressure will be described later, it is preferable that the temperature is 0 to 7 ° and the condition is about 50 kgf / cm ² (hydrate setting condition setting step shown in FIG. 1). 4 By setting the conditions in the hydration tank 2 as described above, an inclusion compound of the rare gas with water is formed in the tank, resulting in a sherbet-like state in the tank (the hydrate shown in FIG. 1). Forming step). (5) The temperature of the hydration tank 2 is set to a freezing temperature of about −10 ° C. or less, and water in the tank is solidified (consolidation step shown in FIG. 1). In this state, the phase of the rare gas hydrate and ice is mixed in the tank. 8 After the completion of the consolidation step, the gas in the phase is degassed to leave no gas in the phase (degassing step shown in FIG. 1). 9 Next, the temperature and pressure in the hydrated tank 2 are changed to a state in which the hydrate is decomposed (for example, at normal temperature and normal pressure).
The hydrate is decomposed, and the rare gas in the hydrate is released to the gas phase portion 2a side. In this state, the gas released from the hydrate phase is collected in the recovery tank 7 via the gas recovery path 4b (a gas recovery step shown in FIG. 1). In this decomposed state, water is kept in a liquid phase state. 10 The amount of water in the hydrate tank 2 is adjusted in relation to the amount of water stored in the water tank 3. Thereafter, the steps described above are repeated.

In this manner, a gas having a high rare gas concentration can be obtained in the recovery tank 7. Hereinafter, the results of experiments performed by the inventors of the present application on the present case will be described. Table 1 shows the results obtained when a rare gas was separated from a raw material gas having a clear gas composition by a single-stage separation process according to the above-described method. In this experimental example, the source gas is mainly composed of two types of gases, one of which is a rare gas to be separated and the other is a base gas other than the rare gas. Here, the main base gas is nitrogen
This is because the gas from which oxygen has been removed from the air is used as the source gas. Further, since xenon is often obtained in a mixed state with nitrogen, such a gas was used as a source gas. By the way, in the table, the initial concentration is the concentration of the rare gas in the raw material gas before performing the separation operation, and the concentration after the reaction is the concentration of the rare gas after performing the one-stage separation operation. is there. Further, the separation coefficient is determined as (post-reaction concentration / initial concentration). The reaction temperature is in units of ° C., the pressure is in units of kgf / cm ² , and the time is in units of hr, and indicates the time required for hydrate formation. Further, the concentration is expressed in%.

[0010]

[Table 1] From the above results, it can be seen that under the pressure and temperature conditions shown in Table 1, an inclusion compound of these source gases and water is formed, and the rare gas can be separated. The pressure and temperature conditions used here are such that the rare gas (Kr or Xe) to be separated and water have a high probability of forming an inclusion compound (hydrate) and are included in the source gas that interferes with the separation operation. Pressure and temperature at which inclusion compounds (hydrates) are less likely (or hardly formed) than other gases (specifically, nitrogen).

Now, in order to perform a more efficient separation in the combination of xenon and nitrogen, the temperature should be 0 ° C. to 7 ° C. under the same pressure condition (50 kgf / cm ² ).
Table 2 shows the change in the separation coefficient when the temperature was changed to ° C. The title system was the same as the system in Table 1.

[0012]

[Table 2]

As a result, in the combination of these gases, separation up to a maximum of 9.75 is possible as a separation coefficient, and a rare gas having a remarkably higher separation coefficient than a conventionally considered separation method can be obtained. It can be seen that separation can be performed. [Another Example] In the above embodiment, the relationship between xenon and nitrogen has been mainly described, but the method of the present invention can be applied to other rare gases.

[Brief description of the drawings]

FIG. 1 is a diagram showing a rare gas separation process of the present invention.

FIG. 2 is a diagram showing a configuration of an apparatus used for separating a rare gas.

[Explanation of symbols]

 2 Hydrating tank 7 Recovery tank

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazuo Nakamura 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi, Osaka F-term in Osaka Gas Co., Ltd. 4D020 AA10 BA23 BB03 BC01 BC02 CC10 CC21 DA01 DA03 DB02 DB04 DB06

Claims (7)

[Claims] 1. A method for separating a rare gas as an inclusion compound by directly contacting a raw material gas containing a rare gas with water at a temperature and pressure at which the rare gas and water form an inclusion compound. A method for separating a rare gas. 2. The method according to claim 1, wherein the source gas containing the rare gas and water are included preferentially with respect to the gas other than the rare gas contained in the source gas. Direct contact under the temperature and pressure to generate an inclusion compound, to generate an inclusion compound of both, while isolating the generated inclusion compound, decomposing the isolated inclusion compound, A method for separating a rare gas, wherein the rare gas is separated from the clathrate. 3. A source gas containing a rare gas and water are introduced into a hydrate tank, and the rare gas and water contained in the source gas are combined with the rare gas contained in the source gas. After maintaining the inside of the hydration tank at a temperature and pressure at which an inclusion compound is preferentially generated with respect to the gas to be removed and generating both inclusion compounds, the inside of the hydration tank is treated with water. The freezing temperature or less, the water in the tank is cooled and solidified, a solid phase composed of the clathrate compound and ice is formed in the hydrated tank, and the inside of the hydrated tank is degassed. A rare gas separation method in which a cladding compound is decomposed in a tank and a gas released from the hydration tank is recovered in this decomposition state to separate and recover a rare gas. 4. The method for separating a rare gas according to claim 1, wherein the rare gas and water are used as clathrate compounds under a condition of 1.5 to 150 kgf / cm ² . 5. The method according to claim 1, wherein the rare gas is argon, and the formation of the clathrate is performed under a temperature condition of 0 ° C. to 30 ° C.
4. The method for separating a rare gas according to claim 1, wherein the pressure is in the range of 95.5 to 150 kgf / cm < ² >. 6. The rare gas is krypton, and the formation of the clathrate is carried out at a temperature condition of 0 ° C. to 30 ° C.
The method of separation according to claim 1, 2 or 3 noble gas according pressure conditions performed under conditions within the 14.5~150kgf / cm ^2. 7. The method according to claim 1, wherein the rare gas is xenon, and the formation of the clathrate is carried out under a temperature condition of 0 ° C. to 30 ° C. and a pressure condition of 1.5 to 150 kgf / cm ^2. The method for separating a rare gas according to claim 1, 2 or 3, which is performed below.