JP2010076972A - Method for treating impure rare gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently and inexpensively recover a rare gas such as neon, xenon from an impure rare gas as a gas to be treated containing the rare gas such as neon, xenon and impurities of a halogen compound, hydrogen and hydrocarbon. <P>SOLUTION: The gas to be treated containing the rare gas such as neon, xenon and the halogen compound, hydrogen and hydrocarbon as impurities is sent to halogen removing columns 4a (4b) and is reacted with a reacting agent such as iron oxide to remove the halogen compound and then oxygen is added into the gas to be treated and introduced into an oxidation column 6 to oxidize hydrogen and hydrocarbon using an oxidation catalyst to obtain a gas to be treated containing water and carbon dioxide and the gas to be treated is sent to dehydration columns 11a (11b) filled with zeolite or the like to remove water. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a processing method and apparatus for removing a rare gas by removing impurities from an impure noble gas composed of a rare gas such as neon, xenon, or krypton and an impurity such as a halogen compound, hydrogen, or hydrocarbon, and a rare gas It relates to a recovery device.

In a xenon lamp or a gas laser oscillator, a mixed gas in which a small amount of a halogen compound such as hydrogen chloride (HCl) or ethyl bromide (C ₂ H ₅ Br) is added to a rare gas such as neon or xenon for excitation of light emission. Is used.
Such a mixed gas is recovered because it contains an expensive rare gas, and the rare gas is purified and recovered from the recovered mixed gas.

However, in this mixed gas, the halogen compound is decomposed along with the excitation of light emission, and by-products such as hydrogen and hydrocarbons are generated in addition to the halogen compound, and this by-product is contained in the recovered gas.
For example, a mixed gas obtained by adding hydrogen chloride to neon becomes a mixed gas containing hydrogen chloride, hydrogen, and chlorine as impurities in addition to neon, along with emission excitation.
In addition, a mixed gas obtained by adding ethyl bromide to neon and xenon becomes a mixed gas containing methane, ethylene, hydrogen bromide, and bromine as impurities in addition to neon and xenon in accordance with emission excitation. Such a mixed gas is called an impure noble gas.
Therefore, in order to recover the rare gas from this kind of impure noble gas, it is necessary to remove such impurities in advance.

Japanese Patent Application Laid-Open No. 2001-232134 discloses a method for recovering high-purity neon from impure neon gas recovered from a KrF excimer laser oscillator.
This method is based on low temperature adsorption separation. First, fluorine is removed from impure neon gas, then cooled to remove krypton by low temperature adsorption, and further cooled to remove impurities by low temperature adsorption to obtain high purity neon. Is.

When trying to process the above-mentioned impure noble gas by the processing method of the prior invention, there is a disadvantage that it is difficult to efficiently separate and remove the impurities, and further, the equipment cost for reducing the temperature due to low temperature adsorption, There is a problem that the operating cost increases.
JP 2001-232134 A

  Therefore, an object of the present invention is to efficiently produce a rare gas such as neon, xenon, or krypton from a rare gas such as neon, xenon, or krypton and an impure noble gas containing impurities such as a halogen compound, hydrogen, or hydrocarbon. It is to be able to collect with.

To solve this problem,
The invention according to claim 1 uses a noble gas and an impurity such as a halogen compound and hydrogen as impurities, or an impure noble gas containing a halogen compound, hydrogen and hydrocarbon as a treatment gas, and removes the halogen compound from the treatment gas. Next, oxygen is added to the gas to be treated to oxidize hydrogen or hydrocarbons to form a gas to be treated containing water or water and carbon dioxide gas, and an impurity of an impure noble gas characterized by removing water from the gas to be treated It is a processing method.

The invention according to claim 2 is the method for treating an impure noble gas according to claim 1, wherein the removal of the halogen compound is to bring the gas to be treated into contact with an adsorbent or a reactant made of a metal oxide.
The invention according to claim 3 is the method of treating an impure noble gas according to claim 1, wherein the oxidation is performed by a metal catalyst.

  According to a fourth aspect of the present invention, a gas containing a rare gas from which impurities have been removed by the impure noble gas processing method according to any one of the first to third aspects is purified by a pressure swing adsorption method, and the rare gas is recovered. This is a noble gas recovery method.

In the invention according to claim 5, a rare gas and a halogen compound and hydrogen as impurities or an impure noble gas containing a halogen compound, hydrogen and hydrocarbon are treated gas, and the treated gas is introduced to remove the halogen compound. A halogen removing unit, an oxidizing unit that adds oxygen to the gas to be processed derived from the halogen removing unit and oxidizes, and a water removing unit that removes water in the gas to be processed derived from the oxidizing unit. It is a processing apparatus for impure noble gases.
The invention according to claim 6 is the rare gas recovery apparatus characterized in that a purification device for recovering the rare gas by the pressure swing adsorption method is provided after the water removal section of the treatment apparatus according to claim 5.

According to the present invention, since the processing temperature in the entire processing process is set to room temperature to about 200 ° C., the equipment cost and the operation cost are remarkably reduced as compared with those by low temperature adsorption separation. Moreover, impurities can be removed well, and the purification of the rare gas in the subsequent process becomes easy.
Furthermore, since the halogen compound is removed at the beginning of the treatment process, corrosion of the equipment is prevented during the treatment in the next step.
In addition, since the halogen compound and water that impair the separation function of the adsorbent are removed during the purification by the pressure swing adsorption method in the latter stage, the rare gas can be recovered without any problem.

FIG. 1 shows an example of the processing apparatus of the present invention.
The gas to be treated is once sent from the pipe 1 to the buffer tank 2 and stored therein, and from there through the mass flow meter 3, the prescribed amount is introduced into the halogen removal cylinder 4 a (4 b).
As described above, the gas to be treated is composed of noble gases such as neon, xenon and krypton and hydrocarbons such as methane and ethylene as impurities, and halogen compounds such as hydrogen, hydrogen chloride, chlorine, hydrogen bromide and bromine. However, the composition varies partially depending on the type of collection source.

Here, consider a case where 15 liters of neon containing 5 vol% hydrogen chloride is enclosed in the laser oscillator as an excitation gas in terms of normal temperature and normal pressure. In this case, the use time of the laser oscillator is about 200 hours, and the excitation gas is discharged for replacement. This exhaust gas contains 2.5 vol% or less of hydrogen and 5 vol% or less of hydrogen chloride.
After exhausting this exhaust gas, a gas purge is performed with about 75 liters of high purity neon. The neon gas after the purge contains a trace amount of hydrogen and hydrogen chloride that have stayed and adsorbed inside the laser oscillator.

Thus, about 15 liters of exhaust gas and about 75 liters of purge gas are exhausted from the laser oscillator every about 200 hours, and about 90 liters of gas becomes the gas to be treated. The concentration of hydrogen and hydrogen chloride in the gas to be treated is diluted to about 1/5 with the purge gas.
In the following description, an example in which an impure noble gas composed of neon, hydrogen, and hydrogen chloride discharged from the laser oscillator is treated as a gas to be treated will be mainly described, and other components such as xenon and krypton may be used as necessary. In addition, the case where hydrocarbons are included will be described supplementarily.

The halogen removing cylinder 4a (4b) constitutes a halogen removing section, and the inside thereof is filled with an adsorbent or a reactive agent, and removes a halogen compound in the gas to be treated.
Activated carbon is used as the adsorbent, and the reactant is a metal oxide such as calcium, strontium, iron, copper, or zinc supported on a support such as zeolite, activated carbon, or alumina.

  When xenon is contained in the gas to be treated, a reactant using potassium ion exchange A-type zeolite as the carrier is suitable. Since potassium ion exchange type A zeolite has the property of hardly adsorbing xenon, xenon can be recovered without waste by adsorbing it in the halogen removal cylinder 4a (4b) without being adsorbed by the halogen removal cylinder 4a (4b). 98% or more of the xenon contained in the gas to be treated can be allowed to flow downstream.

An example of the reaction when using iron oxide supported as a reactant is shown below.
2Fe ₃ O ₄ + 12HCl → 6FeCl ₂ + 6H ₂ O + O ₂
2Fe ₃ O ₄ + 18HCl → 6FeCl ₂ + 8H ₂ O + H _{2
Fe3O 4 + 3Cl 2 → 3FeCl 2} + 2O 2
2Fe ₃ O ₄ + 9Cl ₂ → 6FeCl ₃ + 4O ₂

In this reaction, reaction heat is generated, but the concentration of hydrogen chloride and chlorine is 1 vol% or less, so that the temperature of the reactant does not rise rapidly.
The reaction temperature in the halogen removal cylinder 4a (4b) is 30 to 60 ° C., and the pressure is 0 to 10 kPa (gauge pressure).

  In the example shown in FIG. 1, the halogen removing cylinder 4a (4b) has a two-cylinder structure, one is used for removing halogen compounds, and the other is used alternately for adsorbent or reactant exchange and standby. However, it may be a one-tube configuration. This is because not only when the gas to be treated is always supplied continuously, but also as described above, for example, it may be supplied at intervals of about 200 hours.

  The to-be-processed gas from which the halogen compound has been removed in the halogen removal cylinder 4a (4b) flows through the pipe 5 and is sent to the oxidation cylinder 6, but oxygen is added in the middle thereof. This oxygen passes from the oxygen supply source (not shown) through the mass flow meter 7, and the prescribed amount flows into the pipe 5, joins the gas to be processed, and is introduced into the oxidation cylinder 6.

The oxidation cylinder 6 constitutes an oxidation part, and the inside thereof is filled with an oxidation catalyst. As this oxidation catalyst, a catalyst in which one or more kinds of catalytic metals selected from the group of platinum, palladium, gold, silver and nickel are supported on a carrier such as alumina is used.
A heater 8 is provided on the outer periphery of the oxidation cylinder 6 so that the inside of the oxidation cylinder 6 is maintained at a temperature of 50 to 300 ° C., preferably 80 to 200 ° C.

The flow rate of oxygen added to the gas to be processed is 0.5 to 2 times, preferably 0.7 times the hydrogen flow rate or the total amount of the hydrogen flow rate and the hydrocarbon flow rate assumed to be contained in the gas to be processed. The amount is 1.5 to 1.5 times.
When the gas to be treated to which oxygen has been added is introduced into the oxidation cylinder 6, it is oxidized by the action of the internal oxidation catalyst, and the hydrogen in the gas to be treated contains water and hydrocarbons. Hydrocarbons turn into water and carbon dioxide. The reaction temperature is 50 to 300 ° C, preferably 80 to 200 ° C.

  The gas to be treated derived from the oxidation cylinder 6 is introduced into the heat exchanger 9 and cooled. The operating temperature of the heat exchanger 9 is 5 to 80 ° C, preferably 15 to 35 ° C. Even if the gas to be treated is cooled by the heat exchanger 9, the amount of water generated by the oxidation cylinder 6 is very small, so that no condensation occurs. Further, since the gas to be treated is cooled, the heat resistance temperature of various valves provided in the subsequent stage of the oxidation cylinder 6 is not exceeded.

The gas to be treated having a temperature of 5 to 80 ° C. derived from the heat exchanger 9 flows through the pipe 10 and is sent to the dehydration cylinder 11a (11b) serving as a water removal unit. The dehydrating cylinder 11a (11b) is filled with an adsorbent such as zeolite, activated carbon, or alumina, and water in the gas to be treated is adsorbed and removed by the adsorbent and is derived from the dehydrating cylinder 11a (11b). The gas to be treated is a mixed gas composed of neon and unreacted oxygen. This mixed gas is sent to a PSA purifier (not shown) through a pipe 12 and neon is recovered.
In the case where hydrocarbons are contained in the gas to be treated, the gas to be treated derived from the dehydration cylinder 11a (11b) contains unreacted oxygen and carbon dioxide gas. This mixed gas is also sent to the PSA purifier (not shown) through the pipe 12, and the rare gas is recovered.

  When xenon is contained in the gas to be treated, potassium ion exchange A-type zeolite is suitable as the adsorbent as before. Since the potassium ion exchange type A zeolite has a property of hardly adsorbing xenon, by using this, xenon can be recovered without waste by flowing to the subsequent stage without being adsorbed by the dehydrating cylinder 11a (11b), 98% or more of the xenon contained in the gas to be treated can be passed to the subsequent stage.

In this embodiment, two dehydration cylinders 11a and 11b are used. When one dehydration cylinder 11a is in the water adsorption process, the other dehydration cylinder 11b is used as an adsorbent regeneration process or standby process. By repeating this operation alternately, water can be removed continuously.
If the introduction of the gas to be treated is intermittent, the treatment can be performed by repeating the adsorption process and the regeneration process with one dehydrating cylinder 11a.

  The operation of the dehydrating cylinder 11a (11b) is performed by a normal temperature swing adsorption method, performing adsorption at a low temperature of 5 to 80 ° C., and regeneration at a high temperature of 100 to 300 ° C. Regeneration is performed by introducing nitrogen, argon, dry air, or the like heated to 100 to 300 ° C., preferably 150 to 250 ° C., from the tube 13 into the dehydrating cylinder 11a (11b).

The mixed gas derived from the dehydrating cylinder 11a (11b) is sent to a PSA (pressure swing adsorption method) purification device (not shown) and purified, and the rare gas is recovered.
The rare gas recovery apparatus of the present invention includes the PSA purification apparatus and the above-described processing apparatus.

  The composition of the mixed gas derived from the dehydration cylinder 11a (11b) of the above-described processing apparatus (hereinafter referred to as a rare gas recovery gas) varies depending on the composition of the gas to be processed, but neon, xenon, krypton, oxygen, It contains any two or more of carbon dioxide, for example, rare gas recovery gas containing neon and oxygen, rare gas recovery gas containing neon, xenon, oxygen and carbon dioxide, rare gas containing krypton, oxygen and carbon dioxide Gas for gas recovery is derived.

  Therefore, it is necessary to configure the PSA purifier according to the composition of the rare gas recovery gas and according to the case where the rare gas to be recovered is one type or two types.

  For example, when neon is recovered from a rare gas recovery gas containing neon and oxygen, a well-known PSA purifier equipped with an adsorption cylinder filled with activated carbon as an adsorbent is used. In this case, several tens of ppm of oxygen may remain in the neon after purification. In such a case, oxygen can be reduced to several tens of ppb if it is further introduced into a getter type purification apparatus.

  Further, when neon is recovered from a rare gas recovery gas containing neon, xenon, oxygen, and carbon dioxide, a PSA purifier having an adsorption cylinder filled with activated carbon as an adsorbent is used. At this time, the exhaust gas discharged to the exhaust side of the PSA purifier contains a considerable amount of xenon, and in addition, oxygen, carbon dioxide, and neon are also included. In order to recover xenon from the exhaust gas, carbon dioxide in the exhaust gas is removed by an adsorbent such as Na-X zeolite, and then activated carbon is used using a PSA purifier disclosed in JP-A-2006-61831. It becomes possible by using an adsorbent.

  Further, when recovering krypton from a rare gas recovery gas containing krypton, oxygen, and carbon dioxide, carbon dioxide is first removed by an adsorbent such as Na-X zeolite, and then disclosed in JP-A-2004-819. The krypton is recovered using the disclosed PSA purifier. The PSA purifying apparatus disclosed in Japanese Patent Application Laid-Open No. 2004-819 uses two types of adsorbents, and is an equilibrium separation type adsorbent that exhibits easy adsorptivity to krypton as the first adsorbent. Activated carbon is used as the second adsorbent, and zeolite 4A, which is a speed-separated adsorbent exhibiting easy adsorptivity to oxygen, is used.

Alternatively, carbon dioxide is first removed with an adsorbent such as Na-X zeolite, and then krypton is recovered by using a PSA purifier disclosed in JP-A-2006-61831 and using activated carbon as the adsorbent. it can.
In the above-described recovery method, an adsorbent such as Na-X zeolite is first used to remove carbon dioxide from the rare gas recovery gas. This is performed by a well-known temperature swing adsorption method (TSA). Is.

  In addition, in order to recover the rare gas from the impure noble gas, when the impure noble gas is directly introduced into the PSA purifier, the halogen compound is adsorbed and fixed to the adsorbent, and the separation function is lost and the noble gas is recovered. I can't.

FIG. 2 shows another example of the processing apparatus of the present invention. The apparatus of this example is different from that shown in FIG. 1 in that a counterflow heat exchanger 14 is used.
The to-be-treated gas derived from the halogen removing cylinder 4a (4b) is added with oxygen and introduced into the countercurrent heat exchanger 14, and is heated by exchanging heat with the high-temperature to-be-treated gas derived from the oxidation cylinder 6. In addition, it is introduced into the oxidation cylinder 6.

  With this configuration, the heat energy applied in the oxidation cylinder 6 is effectively recovered and used, so that the heating energy by the heater 8 can be reduced and energy is saved.

Specific examples are shown below.
Using the processing apparatus shown in FIG. 1, a simulated gas to be processed having the composition shown in Table 1 was processed.

As the halogen removal cylinder 4a (4b), a stainless steel reaction cylinder (inner diameter: 50 mm) filled with 200 g of an iron oxide-based detoxifying agent manufactured by Taiyo Nippon Sanso Corporation was used.
As the oxidation cylinder 6, a stainless steel reaction cylinder (inner diameter: 17.5 mm) filled with 30 g of Pd catalyst G74D (palladium; 0.5% / alumina) manufactured by Nissan Gardler Catalysts Ltd. was used as an oxidation catalyst. .
In the dehydrating cylinder 11a (11b), 60 g of Zeorum A-3 (potassium ion exchange type zeolite, hereinafter referred to as potassium A zeolite) manufactured by Tosoh Corporation as an adsorbent was filled in a stainless steel cylinder having an inner diameter of 17.5 mm. Using.

Chlorine, chloride, bromide, and bromine are used in the detectors (TG-100, TG-400, TG-3400, manufactured by Bionics, and SPM manufactured by Honeywell) in the subsequent stage of the halogen removal cylinder 4a (4b). Measurements were made. The dew point was measured with a dew point meter after the dehydrating cylinder 11a (11b).
Further, FT-IR (FT-100G manufactured by Horiba, Ltd.) for organic substances and other gases were measured at the exhaust gas outlet by a gas chromatograph.

A simulated gas to be processed having the composition shown in Table 1 was introduced at a total flow rate of 2000 cc / min for 8 hours. As shown in Table 2, oxygen was added to the oxidation cylinder 6. The oxidation cylinder 6 was used by heating to 80 ° C. from the outside. At this time, the outlet gas temperature reached 170 ° C. by reaction heat.
The dehydrating cylinder 11a (11b) was used by switching every 3 hours. At this time, the dew point did not exceed -80 ° C. Regeneration was performed at a temperature of 300 ° C. and a regeneration nitrogen flow rate of 0.25 L / min.

Halide was not detected by the detector after the halogen removal cylinder 4a (4b).
Table 3 shows the average concentrations of organic substances, oxygen, carbon dioxide gas and water in the gas derived from the dehydrating cylinder 11a (11b).

  From Table 3, it can be seen that halogen, hydrogen, and hydrocarbons in the gas were not detected and oxygen and carbon dioxide gas were contained.

It is a schematic block diagram which shows the example of the processing apparatus of this invention. It is a schematic block diagram which shows the other example of the processing apparatus of this invention.

Explanation of symbols

4a (4b) ... Halogen removal cylinder, 6 ... Oxidation cylinder, 11a (11b) ... Dehydration cylinder

Claims (6)

  A rare gas and an impure noble gas containing a halogen compound and hydrogen as impurities or a halogen compound, hydrogen and hydrocarbon are used as a gas to be treated, the halogen compound is removed from the gas to be treated, and oxygen is then added to the gas to be treated. A method for treating an impure noble gas, characterized in that hydrogen or hydrocarbon is added to oxidize water or a gas to be treated containing water and carbon dioxide gas, and water is removed from the gas to be treated.   2. The method for treating an impure noble gas according to claim 1, wherein the removal of the halogen compound is performed by bringing the gas to be treated into contact with an adsorbent or a reactant made of a metal oxide.   The impure noble gas treatment method according to claim 1, wherein the oxidation is performed by a metal catalyst.   A noble gas, wherein a gas containing a noble gas from which impurities are removed by the impure noble gas processing method according to any one of claims 1 to 3 is purified by a pressure swing adsorption method, and the noble gas is recovered. Recovery method.   A rare gas and a halogen compound and hydrogen as impurities, or an impure noble gas containing a halogen compound, hydrogen and hydrocarbon as a gas to be treated, and a halogen removing section for removing the halogen compound by introducing the gas to be treated; An impure noble gas processing apparatus comprising: an oxidation unit that adds oxygen to a gas to be processed derived from a removal unit and oxidizes; and a water removal unit that removes water in the gas to be processed derived from the oxidation unit.   6. A rare gas recovery apparatus, comprising a purification device for recovering a rare gas by a pressure swing adsorption method at a subsequent stage of the water removal section of the treatment apparatus according to claim 5.

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