JP2012051753A - Method and apparatus for purifying gas - Google Patents

Abstract

[PROBLEMS] To purify by removing hydrocarbons, hydrogen, carbon monoxide, carbon dioxide, oxygen and water in a raw material gas composed of nitrogen gas or rare gas, and to make the purification apparatus compact and expensive. It is possible to reduce the filling amount of a simple catalyst and reduce the purification cost.
A step of bringing a raw material gas into contact with a catalyst to generate carbon dioxide and water, a step of bringing the raw material gas after being brought into contact with the catalyst into contact with a moisture adsorbent, and removing water. The step of removing oxygen of the reaction residue by bringing the raw material gas after removing water into contact with a nickel catalyst, and the raw material gas after removing the oxygen, contained 0.1 to 10 wt% of sodium. And a step of removing carbon dioxide by contacting with alumina, and employing a gas purification method.
[Selection figure] None

Description

  The present invention relates to a method for purifying by removing hydrocarbons, hydrogen, carbon monoxide, carbon dioxide, oxygen and water contained in an inert gas such as nitrogen gas and argon gas used in semiconductor production and the like. Relates to the device.

  In a semiconductor manufacturing process, a high purity inert gas such as nitrogen gas or argon gas is required. These inert gases are generally produced by a cryogenic air separation device, and in the inert gas produced by the cryogenic air separation device, ppm to ppb levels of methane, hydrogen, and carbon monoxide. , Carbon dioxide, oxygen, water, etc. are contained as impurities.

  However, with the recent high integration of semiconductors, it is desired that the impurity concentration in the inert gas used in the semiconductor manufacturing process is ppb or less. For this reason, it is necessary to further purify the inert gas source gas, but it has been difficult to efficiently remove hydrocarbons contained in the source gas.

  In addition, with the recent increase in the size of semiconductor factories, the amount of inert gas used has increased significantly. Along with this, the introduction of large-sized inert gas purification equipment is being promoted, but with the intense price competition of semiconductors, it is strongly desired to reduce the cost of the inert gas purification equipment.

  As described above, Patent Document 1 is known as a method for purifying by removing a small amount of impurities in the raw material gas. In Patent Document 1, hydrocarbons, carbon monoxide, oxygen and hydrogen are converted into carbon dioxide gas and water by a catalyst, then oxygen is removed by a catalyst layer, carbon dioxide is removed by a first adsorption layer, A method of removing moisture with a second adsorption layer has been proposed. However, in this method, since a large amount of water is generated by the reaction between the catalyst and the raw material gas, there is a problem in that the oxygen removal efficiency in the catalyst layer is lowered due to the influence.

As another method for purifying the source gas, Patent Document 2 proposes a method for removing impurities using a zirconium getter.
However, since zirconium getters are expensive and cannot be regenerated, this method is not suitable for refining a large amount of source gas.

Patent Document 3 discloses a method in which oxygen and carbon monoxide in a raw material gas are removed with a reducing metal, and then carbon dioxide and water are removed with an adsorbent such as zeolite. In this method, since the reduced metal after the adsorption of impurities can be regenerated with hydrogen gas, the reduced metal can be reused.
However, when the carbon dioxide partial pressure in the raw material gas is at the ppb level, the amount of carbon dioxide adsorbed by the zeolite becomes very small. Therefore, when purifying a large amount of inert gas, a large amount of zeolite is required, which increases the size of the apparatus and increases the cost.

Patent Document 4 discloses a method in which carbon dioxide in a raw material gas is removed with zinc oxide, oxygen and carbon monoxide are removed with a nickel catalyst or a copper catalyst, and water is further removed with a synthetic zeolite. Yes.
In this purification method, when carbon monoxide and oxygen are removed by a nickel catalyst, a trace amount of carbon dioxide is generated by the catalytic action. Therefore, it is necessary to fill a large amount of synthetic zeolite for adsorbing again the carbon dioxide generated by the catalytic action. As a result, the adsorption tower becomes large, and the cost of the inert gas purification equipment increases.

  Patent Documents 5 and 6 disclose a method of removing carbon dioxide in a raw material gas with alumina. In any of the methods, the amount of carbon dioxide adsorbed on alumina can be increased by containing alkali metal or earth metal in alumina. However, both methods are intended to remove carbon dioxide in the air, that is, carbon dioxide having a high concentration of about 400 ppm, and there is no knowledge of adsorption treatment of carbon dioxide having a low concentration. Further, in the adsorption treatment of high concentration carbon dioxide of about 400 ppm, zeolite adsorbs more carbon dioxide than alumina. For this reason, zeolite has been mainly used as an adsorbent for carbon dioxide in conventional purification apparatuses.

  In the above-described prior invention methods, in order to purify a large amount of raw material gas, a relatively large adsorption tower is required. Further, since the adsorbent is expensive, the manufacturing cost is increased. For this reason, a method for efficiently purifying a large amount of inert gas is desired.

Japanese Patent No. 2640513 Japanese Patent No. 2741622 Japanese Patent No. 2602670 Japanese Patent No. 3462604 Japanese Patent Laid-Open No. 11-518 Japanese Patent Laid-Open No. 2001-104737

  The problem in the present invention is that the purification device can be made compact when removing hydrocarbons, hydrogen, carbon monoxide, carbon dioxide, oxygen and water in the raw material gas composed of nitrogen gas or rare gas. In other words, it is possible to reduce the filling amount of an expensive catalyst and reduce the purification cost.

To solve this problem,
The invention according to claim 1 is a gas purification method for removing hydrocarbons, hydrogen, carbon monoxide, carbon dioxide, oxygen and water in a raw material gas comprising nitrogen gas or a rare gas, wherein the raw material gas is Contacting the catalyst with the hydrocarbons, hydrogen and carbon monoxide to react with an oxidizing gas to produce carbon dioxide and water; and the raw material gas after contacting the catalyst with the moisture adsorbent A step of removing water by contacting the substrate, a step of removing oxygen of a reaction residue by contacting the raw material gas after removing the water with a nickel catalyst, and the raw material gas after removing the oxygen And a step of removing carbon dioxide by bringing it into contact with alumina containing 0.1 to 10 wt% of sodium.

  According to a second aspect of the present invention, the source gas contains an oxidizing gas in an amount that can be stoichiometrically oxidized relative to the amount of hydrocarbons, hydrogen, and carbon monoxide to be reacted with the catalyst. If not, the oxidizing gas is supplied to the source gas until the amount of the hydrocarbons, hydrogen and carbon monoxide can be stoichiometrically oxidized, and then the source gas is brought into contact with the catalyst. The method for purifying a gas according to claim 1, wherein:

  The invention according to claim 3 is the gas purification method according to claim 1 or 2, wherein the partial pressure of carbon dioxide in the raw material gas is 19 Pa or less.

  According to a fourth aspect of the present invention, when the volume conversion filling amount of the nickel catalyst is Va (L) and the volume conversion filling amount of the alumina is Vb (L), a ratio of these filling amounts (Va / L The gas purification method according to any one of claims 1 to 3, wherein Vb) satisfies a relationship of Va / Vb <1.

  The invention according to claim 5 is characterized in that the catalyst is any one or more of Pt, Pd, Ru, Ag, Cu, Mn on a support made of any one or more of activated alumina, diatomaceous earth, and activated carbon. The method for purifying a gas according to any one of claims 1 to 4, wherein 0.01 to 5 wt% is supported.

  The invention according to claim 6 is the gas purification method according to any one of claims 1 to 5, wherein the oxidizing gas is oxygen.

  The invention according to claim 7 is the gas purification method according to any one of claims 1 to 6, wherein the hydrocarbon is methane.

  The invention according to claim 8 is a gas purification apparatus for removing hydrocarbons, hydrogen, carbon monoxide, carbon dioxide, oxygen and water in a raw material gas composed of nitrogen gas or a rare gas, the catalyst being filled with a catalyst A tower, and an adsorption tower provided downstream of the catalyst tower and filled with a moisture adsorbent, a nickel catalyst, and sodium-containing alumina in this order from the inflow side to the outflow side of the raw material gas. This is a gas purifier characterized by that.

According to the gas purification method of the present invention, the hydrocarbons, hydrogen and carbon monoxide in the raw material gas are reacted with the oxidizing gas in advance by bringing the raw material gas consisting of nitrogen gas or rare gas into contact with the catalyst. Can be converted to carbon dioxide and water. Therefore, unlike conventional purification methods that do not use catalyst contact, hydrocarbons in the raw material gas can be removed as carbon dioxide and water.
Moreover, the water in raw material gas can be removed by making the raw material gas after making it contact with a catalyst contact a water | moisture-content adsorption agent. For this reason, it is possible to prevent the nickel catalyst provided on the downstream side of the moisture adsorbent from deteriorating its function due to water. Moreover, since hydrogen and carbon monoxide are reacted with the oxidizing gas, only oxygen in the reaction residue can be removed by the nickel catalyst. For this reason, the filling amount of the nickel catalyst may be an amount capable of removing only oxygen of the reaction residue, and the filling amount can be reduced as compared with the conventional method.
In addition, since the conventional zeolite has a small amount of carbon dioxide adsorption, the Ni catalyst has also adsorbed carbon dioxide, but the sodium-containing alumina has a large amount of carbon dioxide adsorption, so the Ni catalyst only adsorbs oxygen. It is only necessary to fill the required amount, and the filling amount can be greatly reduced.
As a result, the filling amount of the expensive nickel catalyst decreases, and the filling amount of the inexpensive sodium-containing activated alumina increases. For this reason, the manufacturing cost of the inert gas can be reduced, and the purification apparatus can be made compact.

  In addition, when the source gas does not contain oxidizing gas in an amount higher than that stoichiometrically oxidized with respect to the amount of hydrocarbons, hydrogen and carbon monoxide to be reacted with the catalyst, the oxidizing gas is added. It is preferable to supply the source gas until hydrocarbons, hydrogen, and carbon monoxide are in a quantity that can be stoichiometrically oxidized. Thereby, all the hydrocarbons, hydrogen, and carbon monoxide in the raw material gas can be converted into carbon dioxide and water. Therefore, a nickel catalyst for removing hydrogen and carbon monoxide becomes unnecessary, and an increase in the amount of nickel catalyst can be suppressed.

  The partial pressure of carbon dioxide in the raw material gas after removing oxygen is preferably 19 Pa or less. Sodium-containing activated alumina can remove carbon dioxide more efficiently than a zeolite catalyst when the partial pressure of carbon dioxide is 19 Pa or less. For this reason, the filling amount of sodium-containing activated alumina can be reduced, and the refinement apparatus can be made compact.

  Further, when the filling amount in terms of volume of the nickel catalyst is Va (L) and the filling amount in terms of volume of the alumina is Vb (L), the filling amount ratio (Va / Vb) is Va / Vb < It is desirable to satisfy the relationship of 1. The production cost of the inert gas can be reduced by increasing the packing ratio of alumina that is less expensive than the expensive nickel catalyst.

  The catalyst is supported by 0.01 to 5 wt% of one or more of Pt, Pd, Ru, Ag, Cu, and Mn on a support made of one or more of activated alumina, diatomaceous earth, and activated carbon. It is preferable that By using such a catalyst, hydrocarbons can be efficiently reacted with an oxidizing gas.

  The oxidizing gas is preferably oxygen. Oxygen is inexpensive and easy to handle, and has excellent reactivity with hydrocarbons, hydrogen, and carbon monoxide, and thus can be suitably reacted with the source gas.

  According to the gas purification apparatus of the present invention, it is possible to remove hydrocarbons in the raw material gas by providing the catalyst tower filled with the catalyst. In addition, an adsorption tower formed by packing a moisture adsorbent, a nickel catalyst, and sodium-containing alumina in this order from the inflow side to the outflow side of the raw material gas is provided on the downstream side of the catalyst tower. The oxygen and carbon dioxide in the reaction residue can be removed sequentially. For this reason, only oxygen of the reaction residue is removed by the nickel catalyst, and the filling amount of the nickel catalyst can be reduced as compared with the conventional method.

In addition, sodium-containing activated alumina can remove carbon dioxide more efficiently than a conventionally used zeolite catalyst, so there is no need to remove carbon dioxide with a Ni catalyst, and the amount of catalyst can be greatly reduced.
For this reason, the filling amount of the expensive nickel catalyst can be suppressed, and the manufacturing cost of the inert gas can be reduced and the refinement apparatus can be made compact.

FIG. 1 is a schematic configuration diagram showing an example of a gas purification apparatus of the present invention. FIG. 2 is a graph comparing the amount of carbon dioxide adsorbed at a low partial pressure between zeolite and the alumina of the present invention. FIG. 3 is a diagram showing the sodium content and the amount of carbon dioxide adsorbed contained in the alumina of the present invention.

Hereinafter, a gas purification apparatus 1 to which the present invention is applied will be described in detail with reference to the drawings together with a gas purification method using the same.
First, the structure of the gas purification apparatus 1 shown in FIG. 1 is demonstrated as one Embodiment of this invention.
This gas purification apparatus 1 is an apparatus for removing hydrocarbons, hydrogen, carbon monoxide, carbon dioxide, oxygen and water in a raw material gas composed of nitrogen gas or rare gas.
Further, as shown in FIG. 1, the gas purification apparatus 1 is schematically configured to include a catalyst tower 2 filled with a catalyst, and adsorption towers 3 </ b> A and 3 </ b> B provided on the downstream side of the catalyst tower 2. . Details of each component will be described below.

  The catalyst tower 2 is a unit for decomposing and removing hydrocarbons, hydrogen, and carbon monoxide, which are impurities contained in the raw material gas, into water and carbon dioxide using a catalyst. More specifically, a raw material gas supply source G1 is provided on the upstream side of the catalyst tower 2, and the raw material gas passing through the heat exchanger 4 provided in the path L1 from the raw material gas supply source G1 is supplied to the catalyst tower 2. Supplied in. The catalyst tower 2 is filled with a catalyst. A heater 2 a for heating the catalyst tower 2 is provided on the outer periphery of the catalyst tower 2.

The raw material gas is made of nitrogen gas or rare gas as described above, and contains hydrocarbons, hydrogen, carbon monoxide, carbon dioxide, oxygen and water at a concentration of 1 ppm to 10 ppm as impurities.
Here, the hydrocarbons to be treated in the catalyst tower 2 are not particularly limited, and examples thereof include alkanes such as methane and ethane, and aromatic hydrocarbons such as benzene. In particular, since methane has a high content in the air, it is often a countermeasure for treatment.

The catalyst is for contacting hydrocarbons, hydrogen and carbon monoxide in the raw material gas with oxygen, which is an oxidizing gas, to decompose into water and carbon dioxide by contacting with the raw material gas.
As such a catalyst, for example, one or more of Pt, Pd, Ru, Ag, Cu, and Mn is 0 or more on a support made of one or more of activated alumina, diatomaceous earth, and activated carbon. Examples include those supported by 01 to 5 wt%. The catalyst is not limited to those listed here, and other catalysts may be used as long as they have the same function. By using such a catalyst, hydrocarbons in the raw material gas can be efficiently reacted with oxygen.

  An oxidizing gas supply source G2 is provided on the upstream side of the catalyst tower 2. The oxidizing gas supply source G2 is configured to supply the oxidizing gas to the raw material gas by opening and closing the valve V1 provided in the path L2. Also, supply of oxidizing gas when the source gas does not contain oxidizing gas in an amount that can be stoichiometrically oxidized relative to the amount of hydrocarbons, hydrogen, and carbon monoxide in the source gas. An oxidizing gas is supplied from the source G2. For this reason, even if the amount of the oxidizing gas in the raw material gas is insufficient, the oxidizing gas is sufficient until the amount of the hydrocarbons, hydrogen and carbon monoxide in the raw material gas can be stoichiometrically oxidized. Gas can be supplied to the source gas.

  The oxidizing gas is not particularly limited as long as it is a gas capable of completely burning hydrocarbons in the raw material gas. Examples of such a gas include allotropes of oxygen such as oxygen and ozone. Among these, oxygen is particularly preferable in terms of handling.

Adsorption towers 3A and 3B are units for removing water, reaction residue oxygen and carbon dioxide contained in the raw material gas derived from catalyst tower 2. Further, the adsorption tower 3A and the adsorption tower 3B have the same configuration.
More specifically, in the adsorption tower 3 </ b> A and the adsorption tower 3 </ b> B, the moisture adsorbent layer 6, the nickel catalyst layer 7, and the alumina layer 8 are directed from the source gas inflow side (bottom) to the outflow side (top). Are stacked and filled in this order. Further, the adsorption towers 3A and 3B are configured to be able to switch the flow of hydrogen gas supplied from the source gas and the regeneration gas supply source G4 by opening and closing the valves V2 to V9. In addition, heaters 3c and 3d for heating the adsorption towers 3A and 3B are provided on the outer circumferences of the adsorption towers 3A and 3B, respectively.

  The moisture adsorbent layer 6 is a moisture adsorbent for adsorbing water in the source gas by contacting the source gas. As the moisture adsorbent, for example, one or more of activated alumina, silica gel, and synthetic zeolite can be used. Further, the moisture adsorbent is not limited to those listed here, and any other adsorbent may be used as long as it has a function of adsorbing water in the source gas.

  The nickel catalyst layer 7 is provided in order to remove oxygen of the reaction residue in the raw material gas by contacting the raw material gas. Specifically, the nickel catalyst layer 7 is filled with a nickel catalyst that can be reused after being subjected to a reduction treatment with hydrogen. As such a nickel catalyst, for example, a catalyst in which 10 to 90 wt% of nickel metal is supported on a support such as activated alumina, diatomaceous earth, or activated carbon is used.

  The alumina layer 8 is provided to remove carbon dioxide in the raw material gas by contacting the raw material gas. Specifically, the alumina layer 8 is filled with γ-alumina containing 0.1 to 10 wt% sodium. Thus, by filling the alumina layer 8 with the sodium-containing activated alumina, the Ni catalyst only needs to be filled in an amount necessary for adsorbing only oxygen, and the filling amount can be greatly reduced. .

  Further, when the filling amount in terms of volume of the nickel catalyst is Va (L) and the filling amount in terms of volume of the alumina is Vb (L), the filling amount ratio (Va / Vb) is Va / Vb < It is desirable to satisfy the relationship of 1. Since alumina is cheaper than nickel catalyst, the production cost of the gas purifier 1 can be reduced by increasing the alumina filling amount ratio than the nickel catalyst.

  The adsorption towers 3A and 3B are supplied with the raw material gas which is led out from the catalyst tower 2 and passes through the heat exchanger 4 and the cooler 5. At that time, the source gas is configured to be supplied to either the adsorption tower 3A or 3B. Further, the upper side of the adsorption towers 3A and 3B is configured such that hydrogen gas from the regeneration gas supply source G4 is supplied to either the adsorption tower 3A or 3B through the path L7, the valve V10, and the path L8. Yes.

  Further, an inert gas discharge part G3 is provided in the path L5 on the upper side of the adsorption towers 3A and 3B, and the inert gas purified by the adsorption tower 3A or 3B is discharged. Further, the inert gas having passed through the path L8 and the valve V11 is supplied from the path L5 to the adsorption tower 3A or 3B. Further, an exhaust gas discharge part G5 is provided in the path L6 on the bottom side of the adsorption towers 3A and 3B, and the exhaust gas is discharged.

  In FIG. 1, the moisture adsorbent layer 6, the nickel catalyst layer 7 and the alumina layer 8 are stacked and filled from the bottom to the top in the adsorption tower 3A. However, from the inflow side to the outflow side of the raw material gas. The arrangement may be changed in reverse so that the order is the same. That is, the arrangement in the adsorption tower 3A may be reversed so that the raw material gas can flow from the top to the bottom of the adsorption tower 3A.

According to the gas purification apparatus 1 of this embodiment, it is possible to remove hydrocarbons in the raw material gas by providing the catalyst tower 2 filled with the catalyst. Further, on the downstream side of the catalyst tower 2, there are provided adsorption towers 3A and 3B filled with a moisture adsorbent, a nickel catalyst and sodium-containing alumina in this order from the inflow side to the outflow side of the raw material gas. As a result, water, oxygen and carbon dioxide in the reaction residue can be removed sequentially. For this reason, only oxygen of the reaction residue is removed by the nickel catalyst, and the filling amount of the nickel catalyst can be reduced as compared with the conventional method. In addition, since sodium-containing activated alumina can remove carbon dioxide more efficiently than a zeolite catalyst that has been used as a catalyst for removing carbon dioxide, the amount of catalyst (nickel catalyst) required for removing carbon dioxide. Can be greatly reduced.
For this reason, the filling amount of the expensive nickel catalyst can be suppressed, and the manufacturing cost of the inert gas can be reduced and the gas purification device 1 can be made compact.

  Next, the gas purification method of this embodiment will be described with reference to the drawings. The gas purification method (adsorption process) of the present embodiment is a process of generating carbon dioxide and water by bringing a raw material gas into contact with a catalyst and reacting hydrocarbons, hydrogen and carbon monoxide with an oxidizing gas, A step of removing water by bringing the raw material gas after contact with the catalyst into contact with a moisture adsorbent; and a step of removing oxygen in the reaction residue by bringing the raw material gas after removal of water into contact with the nickel catalyst; , And a step of removing carbon dioxide by bringing the source gas after removing oxygen into contact with alumina containing 0.1 to 10 wt% of sodium.

  First, as shown in FIG. 1, the source gas is introduced into the path L1 from the source gas supply source G1. At this time, as the source gas, for example, a gas produced by a cryogenic air separation device or a gas stored in a cold evaporator tank (ultra low temperature liquefied gas storage tank) can be used.

  Here, if the source gas does not contain an oxidizing gas that is more than stoichiometrically oxidizable with respect to the amount of hydrocarbons, hydrogen, and carbon monoxide in the source gas, It is preferable to introduce gas into the path L2. Note that the oxidizing gas is preferably supplied until the amount of the hydrocarbons, hydrogen, and carbon monoxide in the raw material gas exceeds the stoichiometric amount. Moreover, it is preferable to use oxygen as the oxidizing gas.

  Thus, the oxidizing gas is mixed with the raw material gas in the path L1, passes through the heat exchanger 4, and flows into the catalyst tower 2 heated by the heater 2a. At this time, when the temperatures of the raw material gas and the oxidizing gas are not sufficient, the heat exchanger 4 can appropriately heat them.

  Thereafter, the raw material gas contacts the catalyst in the catalyst tower 2, and hydrocarbons, hydrogen and carbon monoxide in the raw material gas react with the oxidizing gas. At this time, excess oxygen does not react and remains in the source gas as oxygen as a reaction residue. Also, carbon dioxide and water are generated by this reaction. Thereby, the impurities in the raw material gas at this stage are only carbon dioxide, water and oxygen of the reaction residue.

  Thereafter, the raw material gas is introduced into the adsorption tower 3A through the heat exchanger 4 and the cooler 5, the path L4, and the valve V2 provided in the path L3. At this time, if the temperature of the raw material gas is too high, the temperature may be adjusted appropriately by the heat exchanger 4 and the cooler 5. At this time, the source gas may be introduced into either the adsorption tower 3A or the adsorption tower 3B. Here, a case where the source gas is introduced into the adsorption tower 3A will be described.

  The source gas introduced into the adsorption tower 3 </ b> A first flows into the moisture adsorbent layer 6. Here, the source gas contacts the moisture adsorbent, and moisture is adsorbed and removed.

  Next, the raw material gas flowing out from the moisture adsorbent layer 6 flows into the nickel catalyst layer 7. Here, the source gas comes into contact with the nickel catalyst, and oxygen in the reaction residue is adsorbed and removed.

Next, the raw material gas flowing out from the nickel catalyst layer 7 flows into the alumina layer 8. Here, the source gas contacts the sodium-containing activated alumina, and carbon dioxide is adsorbed and removed. At this time, it is desirable that the partial pressure of carbon dioxide in the raw material gas before the contact with the sodium-containing activated alumina is 19 Pa or less. As shown in FIG. 2, sodium-containing activated alumina can remove carbon dioxide more efficiently than a zeolite catalyst when the partial pressure of carbon dioxide in the raw material gas is 19 Pa or less. Therefore, carbon dioxide can be efficiently adsorbed and removed by setting the partial pressure of carbon dioxide in the raw material gas to 19 Pa or less in advance. FIG. 2 is a graph comparing the carbon dioxide adsorption amounts of zeolite and alumina. Further, the measurement of the carbon dioxide adsorption amount in FIG. 2 is performed by using a constant capacity gas adsorption amount measuring device while keeping the temperature constant at 25 ° C. and arbitrarily setting the pressure.
Thus, since carbon dioxide in the raw material gas can be efficiently removed, the Ni catalyst only needs to be filled with an amount that adsorbs only oxygen, and the filling amount of the Ni catalyst can be reduced.

  Thereafter, the raw material gas is led out as purified gas (inert gas) from the inert gas discharge part G3 via the valve V8 and the path L5. At this time, the concentration of impurities (hydrocarbon, hydrogen, carbon monoxide, carbon dioxide, oxygen and water) of the inert gas is 0.1 ppb level or less.

Next, the regeneration step in the adsorption tower 3A will be described.
First, after performing the adsorption process in the adsorption tower 3A, the valves V2 to V9 are opened and closed to switch the flow of the source gas and the hydrogen gas. Thereby, the adsorption tower 3A enters the regeneration process, and the adsorption tower 3B enters the adsorption process.

  Next, hydrogen gas is introduced into the path L7 from the regeneration gas supply source G4. As a result, the hydrogen gas is mixed with a part of the purified inert gas in the path L8 to become a mixed gas having a hydrogen concentration of 1 to 5 vol%. Next, the mixed gas is introduced to the upper side of the adsorption tower 3A. Thereby, the mixed gas sequentially passes through the alumina layer 8, the nickel catalyst layer 7, and the moisture adsorbent layer 6.

At this time, the adsorption tower 3A is heated by the heater 3c. Therefore, impurities such as carbon dioxide adsorbed on the alumina layer 8, oxygen adsorbed on the nickel catalyst layer 7, moisture adsorbed on the moisture adsorbent layer 6 are heated by the heater 3 c and the action of the mixed gas. Detach one after another. Thereby, the said impurity mixes with mixed gas, and it discharges | emits as exhaust gas from the exhaust-gas discharge part G5 through the path | route L6.
The adsorption tower 3A that has been regenerated in this way waits for the next adsorption step.

  Further, during the regeneration step in the adsorption tower 3A, the source gas introduced into the adsorption tower 3B is adsorbed with impurities in the same manner as described above, and is discharged from the inert gas discharge part G3 as an inert gas. Since this is the same as the adsorption step in the adsorption tower 3A described above, the description is omitted.

According to the gas purification method of the present embodiment, by bringing the raw material gas into contact with the catalyst, hydrocarbons, hydrogen, and carbon monoxide in the raw material gas are reacted with the oxidizing gas in advance to form carbon dioxide and water. Can be converted. Therefore, unlike conventional purification methods that do not use catalyst contact, hydrocarbons in the raw material gas can be removed as carbon dioxide and water.
Moreover, the water in raw material gas can be removed by making the raw material gas after making it contact with a catalyst contact a water | moisture-content adsorption agent. For this reason, it is possible to prevent the nickel catalyst provided on the downstream side of the moisture adsorbent from deteriorating its function due to water. Moreover, since hydrogen and carbon monoxide are reacted with the oxidizing gas, only oxygen in the reaction residue can be removed by the nickel catalyst. For this reason, the filling amount of the nickel catalyst only needs to be an amount capable of removing only oxygen in the reaction residue, and the filling amount can be reduced as compared with the conventional gas purification method.

In addition, when the source gas does not contain oxidizing gas in an amount higher than that stoichiometrically oxidized with respect to the amount of hydrocarbons, hydrogen and carbon monoxide to be reacted with the catalyst, the oxidizing gas is added. The hydrocarbons, hydrogen and carbon monoxide in the source gas are all converted to carbon dioxide by supplying the source gas until the amount of hydrocarbons, hydrogen and carbon monoxide can be oxidized stoichiometrically. Can be converted to water. Therefore, a nickel catalyst for removing hydrogen and carbon monoxide becomes unnecessary.
For this reason, the filling amount of an expensive nickel catalyst can be reduced, and the manufacturing cost of an inert gas can be reduced.

Further, by setting the partial pressure of carbon dioxide in the raw material gas to 19 Pa or less, carbon dioxide can be efficiently removed by sodium-containing activated alumina. For this reason, the filling amount of the Ni catalyst can be reduced.
As described above, the content of the catalyst (nickel catalyst, sodium-containing activated alumina) in the adsorption tower 3A (3B) can be reduced. For this reason, the gas purification apparatus 1 can be made compact.

  Hereinafter, the gas purification method of the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
First, a catalyst tower 2 was prepared by filling 400 mm of alumina-supported Pd catalyst in a stainless steel cylinder having an inner diameter of 100 mm. Further, in a stainless steel cylinder with an inner diameter of 100 mm, a moisture adsorbent layer 6 (MS5A) made of a zeolite layer with a thickness of 100 mm, a nickel catalyst layer 7 (N112) with a thickness of 50 mm, and sodium with a thickness of 250 mm in weight ratio. An alumina layer 8 containing 5.8% was formed in order from the raw material gas inflow side to the outflow side to obtain an adsorption tower 3A.

First, each layer of the adsorption tower 3A was regenerated under the following conditions.
First, nitrogen containing a hydrogen concentration of 2 vol% was introduced into the adsorption tower 3A through the path L7 and the path L8 at a flow rate of 2 Nm ³ / hour for 3 hours and heated to 200 ° C. by the heater 3c. Next, after flowing nitrogen through the adsorption tower 3A at a flow rate of 2 Nm ³ / hour, the adsorption tower 3A was cooled.

Next, an adsorption process was performed.
First, 1 ppm-methane, 1 ppm-hydrogen, 1 ppm-carbon monoxide, 0.5 ppm-carbon dioxide, 4 ppm-oxygen, 2.6 ppm-nitrogen containing moisture is used as a raw material gas, pressure 100 PaG, temperature 400 ° C., flow rate 15 Nm ^3. / Hour was introduced into the catalyst tower 2. Thereafter, the temperature of the raw material gas was cooled to 25 ° C. by the heat exchanger 4 and the cooler 5 and introduced into the adsorption tower 3A.
Oxygen was detected as the first breakthrough component when 50 hours had elapsed after the start of introduction of the raw material gas into the adsorption tower 3A.

(Example 2)
A catalyst tower 2 was prepared by filling 400 mm of alumina-supported Pt catalyst in a stainless steel cylinder having an inner diameter of 100 mm. Further, in a stainless steel cylinder having an inner diameter of 100 mm, a water adsorbent layer 6 ((MS5A) consisting of a zeolite layer having a thickness of 100 mm from above, a nickel catalyst layer 7 (N112) having a thickness of 50 mm, and sodium having a thickness of 250 mm were added. The alumina layer 8 containing 5.8% by weight was formed in order from the raw material gas inflow side to the outflow side to obtain an adsorption tower 3A.

Next, after the adsorption tower 3A was regenerated under the same conditions as in Example 1, the adsorption process was performed under the same conditions as in Example 1.
Oxygen was detected as the first breakthrough component when 49 hours had elapsed after starting the introduction of the raw material gas into the catalyst tower 2 and the adsorption tower 3A.

(Comparative Example 1)
In a stainless steel cylinder with an inner diameter of 100 mm, a moisture adsorbent layer 6 (MS5A) consisting of a zeolite layer with a thickness of 100 mm, a nickel catalyst layer 7 (N112) with a thickness of 200 mm, and sodium with a thickness of 250 mm in weight ratio. An alumina layer 8 containing 5.8% was formed in order from the raw material gas inflow side to the outflow side to obtain an adsorption tower 3A. Next, the regeneration process was performed under the following conditions.

First, nitrogen having a hydrogen concentration of 2 vol% was heated to 200 ° C., and passed through the adsorption tower 3A through the path L7 and the path L8 at a flow rate of 2 Nm ³ / hour for 3 hours. Next, nitrogen was heated to 200 ° C. and allowed to flow through the adsorption tower 3A at a flow rate of 2 Nm ³ / hour for 3 hours.
After that, nitrogen containing 1 ppm-methane, 1 ppm-hydrogen, 1 ppm-carbon monoxide, 0.5 ppm-carbon dioxide, 4 ppm-oxygen, 2.6 ppm-water is used as a raw material gas, pressure 100 PaG, temperature 25 ° C., flow rate ( It was introduced into the adsorption tower 3A under conditions of a superficial velocity of 26.5 cm / second and a flow rate of 15 Nm ³ / hour.
Immediately after the start of introduction, 1 ppm of methane was detected, and when 47 hours had passed, hydrogen was detected as the first breakthrough component.

(Comparative Example 2)
A catalyst tower 2 was prepared by filling 400 mm of an alumina-supported Pd catalyst into a stainless steel cylinder having an inner diameter of 100 mm. Further, in a stainless steel cylinder with an inner diameter of 100 mm, a nickel catalyst layer 6 (N112) with a thickness of 50 mm, a moisture adsorbent layer 7 (MS5A) made of a zeolite layer with a thickness of 100 mm, and sodium with a thickness of 250 mm in weight ratio. An alumina layer 8 containing 5.8% was formed in order from the raw material gas inflow side to the outflow side to obtain an adsorption tower 3A.

  Next, after the adsorption tower 3A was regenerated under the same conditions as in Example 1, a raw material gas having the same composition as in Example 1 was introduced into the catalyst tower 2 and the adsorption tower 3A under the same conditions. Oxygen was detected as the first breakthrough component when 40 hours had elapsed after starting the introduction of the raw material gas into the catalyst tower 2 and the adsorption tower 3A.

(Comparative Example 3)
A catalyst tower 2 was prepared by filling 400 mm of an alumina-supported Pd catalyst into a stainless steel cylinder having an inner diameter of 100 mm. In addition, in a stainless steel cylinder having an inner diameter of 100 mm, a moisture adsorbent layer 6 (MS5A) composed of a zeolite layer having a thickness of 100 mm from above, a nickel catalyst layer 7 (N112) having a thickness of 50 mm, and an alumina layer 8 having a thickness of 250 mm. Were formed in order from the raw material gas inflow side to the outflow side to form an adsorption tower 3A.

  Next, after the adsorption tower 3A was regenerated under the same conditions as in Example 1, a raw material gas having the same composition as in Example 1 was introduced into the catalyst tower 2 and the adsorption tower 3A under the same conditions. Carbon dioxide was detected as the first breakthrough component when 27 hours passed after starting the introduction of the raw material gas into the catalyst tower 2 and the adsorption tower 3A.

  Table 1 summarizes the packing amounts of the catalyst and the adsorbent of each Example and Comparative Example, and the breakthrough components and breakthrough time obtained through experiments.

  From Example 1 and Comparative Example 1, it can be seen that methane was removed by reacting hydrocarbons (methane), hydrogen, carbon monoxide and oxygen with the catalyst of the catalyst tower 2. Furthermore, by reacting the raw material gas in advance in the catalyst tower 2, the load on the nickel catalyst is only oxygen, so that the filling amount of the nickel catalyst can be greatly reduced. (In Comparative Example 1, since the nickel catalyst was loaded with hydrogen, carbon monoxide, and oxygen, the breakthrough of hydrogen started in 47 hours even when the nickel catalyst was charged four times.)

  Further, it can be seen from Example 1 and Comparative Example 2 that when the moisture adsorbent layer 6 is formed on the upstream side of the nickel catalyst layer 7, the oxygen adsorption amount in the nickel catalyst layer 7 is increased.

  Moreover, it can be seen from Example 1 and Comparative Example 3 that when alumina containing sodium is used, carbon dioxide is not detected in the inert gas even if the filling amount of alumina is greatly reduced.

(Example 3)
Under the condition of carbon dioxide partial pressure of 1 Pa, the amount of carbon dioxide adsorbed on alumina was measured by changing the sodium content. As a result, the carbon dioxide adsorption amounts of alumina having a sodium content of 0.1 wt%, 1.6 wt%, 5.8 wt%, and 9.8 wt% were 38, 50, 60, and 65 mmol / kg, respectively. The carbon dioxide adsorption amount of alumina having a sodium content of 0.1 wt% or less was 28 mmol / kg. FIG. 3 is a graph showing the results, with the horizontal axis representing sodium content and the vertical axis representing carbon dioxide adsorption. In addition, the measurement of the carbon dioxide adsorption amount shown in FIG. 3 was performed by setting a temperature of 25 ° C. and a pressure of 1 Pa using a constant capacity gas adsorption amount measuring device.
From the graph of FIG. 3, it can be seen that the carbon dioxide adsorption ability of alumina containing sodium is higher than that of alumina not containing sodium.

DESCRIPTION OF SYMBOLS 1 ... Gas purification apparatus, 2 ... Catalyst tower, 3A, B ... Adsorption tower, 6 ... Moisture adsorbent layer, 7 ... Nickel catalyst layer, 8 ... Alumina layer, G1 ... Raw material gas supply source, G2 ... Oxidizing gas supply source , G3 ... inert gas discharge part

Claims (8)

A gas purification method for removing hydrocarbons, hydrogen, carbon monoxide, carbon dioxide, oxygen and water in a raw material gas consisting of nitrogen gas or rare gas,
Producing carbon dioxide and water by contacting the source gas with a catalyst and reacting the hydrocarbons, hydrogen and carbon monoxide with an oxidizing gas;
Removing the water by contacting the raw material gas after contacting the catalyst with a moisture adsorbent;
Removing oxygen of the reaction residue by contacting the raw material gas after removing the water with a nickel catalyst;
A step of removing carbon dioxide by contacting the raw material gas after removing the oxygen with alumina containing 0.1 to 10 wt% of sodium, and purifying the gas Method. When the source gas does not contain oxidizing gas in an amount that can be stoichiometrically oxidized relative to the amount of hydrocarbons, hydrogen, and carbon monoxide to be reacted with the catalyst,
An oxidizing gas is supplied to the source gas until the amount of the hydrocarbon, hydrogen and carbon monoxide is stoichiometrically oxidized, and then the source gas is brought into contact with the catalyst. The method for purifying a gas according to claim 1.   The method for purifying a gas according to claim 1 or 2, wherein a partial pressure of carbon dioxide in the raw material gas after removing the oxygen is 19 Pa or less.   When the filling amount in terms of volume of the nickel catalyst is Va (L) and the filling amount in terms of volume of the alumina is Vb (L), the filling amount ratio (Va / Vb) is Va / Vb < The gas purification method according to any one of claims 1 to 3, wherein the relationship 1 is satisfied.   One or more of Pt, Pd, Ru, Ag, Cu, Mn is supported on 0.01 to 5 wt% of the catalyst on a support made of one or more of activated alumina, diatomaceous earth, and activated carbon. The gas purification method according to any one of claims 1 to 4, wherein:   The gas purification method according to claim 1, wherein the oxidizing gas is oxygen.   The method for purifying a gas according to any one of claims 1 to 6, wherein the hydrocarbon is methane. A gas purifier for removing hydrocarbons, hydrogen, carbon monoxide, carbon dioxide, oxygen and water in a raw material gas consisting of nitrogen gas or rare gas,
A catalyst tower packed with a catalyst;
An adsorption tower provided downstream of the catalyst tower and filled with a moisture adsorbent, a nickel catalyst, and sodium-containing alumina in this order from the inflow side to the outflow side of the raw material gas. Gas purifier.

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