JPH0857240A - Gas purifying method and apparatus - Google Patents

Abstract

PURPOSE: To extend the life of an oxidizing catalyst in purifying gas without using special equipment by removing carbon monoxide and/or hydrogen in gas by the oxidation reaction due to the oxidizing catalyst. CONSTITUTION: A treatment cylinder 13 having a gas introducing part 11 and a gas lead-out part 12 is packed with a mixture C consisting of an oxidizing catalyst for converting carbon monoxide and hydrogen to carbon dioxide and water by catalytic reaction and an adsorbent adsorbing and removing carbon dioxide and gas to be treated is brought into contact with the mixture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas refining method and apparatus, and more particularly to a gas refining method suitable for removing carbon monoxide and hydrogen in the air supplied as a raw material gas to an air liquefaction separation apparatus. And equipment.

[0002]

2. Description of the Related Art In an air liquefaction separation apparatus for producing oxygen, nitrogen, etc., impurities such as water and carbon dioxide contained in raw material air are adsorbed and removed by an adsorbent such as zeolite. Carbon monoxide and hydrogen of about 5 to 10 ppm contained therein cannot be adsorbed and removed by an ordinary adsorbent for removing water and carbon dioxide, and carbon monoxide has a boiling point. Is close to the boiling point of nitrogen, it is difficult to separate it by rectification, and hydrogen is
It is possible to separate by rectification, but since the rectification equipment becomes complicated, usually there is a disadvantage that carbon monoxide and hydrogen are mixed as impurities in product nitrogen unless special measures are taken. .

Therefore, after the raw air is brought into contact with an oxidation catalyst to convert carbon monoxide into carbon dioxide and hydrogen into water, the produced carbon dioxide and water are adsorbed and removed by an adsorbent. For example, the refining device having the configuration shown in FIG. 3 is used.

The gas (air) refining apparatus shown in FIG. 3 has an air compressor 2 for compressing the raw material air sucked from the air intake port 1 to a predetermined pressure, the compressed raw material air and the high temperature discharged from the catalyst tube 3. Heat exchanger 4 for exchanging heat with the raw material air for heat recovery, heater 5 for further heating the raw material air to a predetermined temperature, and heat recovery with heat exchanger 4 derived from catalyst tube 3 The cooler 6 for cooling the raw material air subjected to the above, and the adsorption cylinders 7, 7 for removing impurities such as carbon dioxide and water in the cooled raw material air are provided.

The raw material air sucked from the air intake port 1 is heated to about 70 ° C. by the heat of compression in the air compressor 2, and is then discharged from the catalyst tube 3 in the heat exchanger 4 to have a high temperature of about 150 ° C. The heat is exchanged with air to raise the temperature to about 140 ° C., and the temperature is raised to a predetermined temperature, for example, about 150 ° C. by the heater 5 and introduced into the catalyst cylinder 3. Carbon monoxide and hydrogen in the raw material air introduced into the catalyst cylinder 3 are
Carbon monoxide is converted to carbon dioxide and hydrogen is converted to water by the catalytic reaction of the oxidation catalyst A such as palladium filled in the cylinder. The carbon dioxide and water generated in the catalyst column 4 are adsorbed on the adsorbent B such as zeolite filled in the adsorption column 7 together with the carbon dioxide and water originally contained in the raw material air, and the raw material air Removed from inside. The air thus purified is supplied to the main body (cold box) of the air liquefaction separation device through the pipe 8.

[0006]

However, in the apparatus for purifying air by utilizing the catalytic reaction as described above, the catalyst is deteriorated by the catalyst poison such as sulfur oxide contained in the atmosphere, and the oxidation catalyst is frequently used. There is a problem that it has to be replaced. Further, as described above, by using the oxidation catalyst under heating, it is possible to increase the activity of the oxidation catalyst, there is an advantage that the life can be extended, in the case of the air liquefaction separation device, the purification target gas Since the amount of raw material air is extremely large, a large amount of energy is required to heat a large amount of raw material air, and even if heat recovery is performed to reduce energy, a large heat exchanger must be used. It has the disadvantage of having to be installed.

[0007] Therefore, an object of the present invention is to provide a method and an apparatus for purifying a gas which can extend the life of an oxidation catalyst without using special equipment.

[0008]

In order to achieve the above-mentioned object, a method for purifying a gas according to the present invention is an oxidation catalyst for converting carbon monoxide and / or hydrogen into carbon dioxide and / or water by a catalytic reaction. And a mixture of carbon dioxide and an adsorbent for adsorbing and removing carbon dioxide.

Further, in the gas purifying apparatus of the present invention, the carbon monoxide and / or hydrogen is converted into carbon dioxide and / or water by a catalytic reaction in a processing cylinder having a gas inlet and a gas outlet. And an adsorbent for adsorbing and removing carbon dioxide and water are filled with a mixture, and the device of the present invention further comprises a desiccant on the gas introduction side and a gas derivation section. This also includes filling and arranging an adsorbent on the side.

[0010]

[Operation] The above-mentioned adsorbent for adsorbing and removing carbon dioxide and water has an extremely large surface area and a high adsorption capacity, so it can adsorb not only carbon dioxide and water but also various catalyst poison components. it can. Therefore, according to the above configuration, components that become catalyst poisons such as sulfur oxides, carbon-containing compounds such as oil, nitrogen oxides and chlorides contained in gas can be adsorbed and removed by the adsorbent, and the oxidation catalyst Can be suppressed. Furthermore, by removing the water content with a desiccant in the previous stage, deterioration due to water can be prevented, and by filling the adsorbent in the latter stage, the carbon dioxide and water generated by the catalytic reaction can be reliably Can be removed.

[0011]

EXAMPLES Hereinafter, the present invention will be described in more detail based on examples in which it is applied to an adsorber for purifying raw material air of an air liquefaction separation apparatus. First, the gas purification apparatus shown in FIG. 1 has a pair of processing cylinders 13 each having a gas introduction unit 11 and a gas derivation unit 12.
A mixture C in which an oxidation catalyst for converting carbon monoxide and hydrogen into carbon dioxide and water by a catalytic reaction and an adsorbent for adsorbing and removing carbon dioxide and water are mixed in each cylinder of the adsorber consisting of And the desiccant D is filled on the gas introduction part 11 side of the mixture C. In the adsorber of a normal air liquefaction separation apparatus, when one of the pair of processing cylinders 13 is in the refining process, the other is used as a regeneration process, and both cylinders are sequentially switched to both processes to continuously supply the raw material air. It is configured to allow purification.

Raw material air, which is a gas to be purified (process gas), is sucked from an air intake port 21, compressed by an air compressor 22, and then cooled to a predetermined temperature by a cooler 23, which is in the purification process. It is introduced into the processing cylinder 13. The raw material air flowing into the cylinder from the gas introduction part 11 first comes into contact with the desiccant D filled in the introduction part side to remove water, and then comes into contact with the mixture C composed of the oxidation catalyst and the adsorbent. .

Various catalyst poison components such as carbon dioxide and sulfur oxides contained in the raw material air are adsorbed and removed by the adsorbent in the mixture C, and carbon monoxide and hydrogen are absorbed in the oxidation catalyst in the mixture C. When they come into contact with each other to cause a catalytic reaction, they react with oxygen in the air to convert carbon monoxide into carbon dioxide and hydrogen into water. The carbon dioxide and water generated by this catalytic reaction are adsorbed and removed by the adsorbent in the mixture C, like the carbon dioxide and the like. The raw material air thus purified by removing impurities is led out from the gas lead-out portion 12 and supplied to the main body portion (cold box) of the air liquefaction separation device through the pipe 24.

At this time, the other processing cylinder 13 is in the regeneration process, and the regeneration gas supplied from the pipe 25 is the gas outlet 12.
The carbon dioxide and the like adsorbed on the adsorbent in the mixture C and the water trapped in the desiccant D are desorbed and discharged from the gas introduction unit 11 through the pipe 26.

As described above, by using an oxidation catalyst for converting carbon monoxide and hydrogen in the raw material air into carbon dioxide and water with an adsorbent for adsorbing carbon dioxide and water, the oxidation catalyst is deteriorated. It is possible to adsorb and remove the catalyst poison components such as sulfur-containing compounds, carbon-containing compounds such as oil, nitrogen oxides, chlorides, etc., which can prevent deterioration of the oxidation catalyst due to these catalyst poisons. Furthermore, by removing the water with the desiccant in the previous stage, deterioration of the oxidation catalyst due to the water can be prevented.

As the above-mentioned oxidation catalyst, various kinds can be used. Particularly, for the oxidation of carbon monoxide, a catalyst in which platinum, palladium, or copper oxide is supported on activated alumina, and gold fine particles are subjected to metal oxidation. A catalyst fixed to a substance or a metal oxide catalyst such as copper oxide-manganese oxide or iron oxide-manganese oxide is effective, and for oxidizing hydrogen, a catalyst in which palladium is supported on activated alumina is effective. . On the other hand, a commonly used zeolite can be used as the adsorbent that adsorbs carbon dioxide and water, and activated alumina, silica gel, or the like can be used as the desiccant.

The mixing of the oxidation catalyst and the adsorbent means that the particles of the both are completely and uniformly mixed, but the mixing is insufficient, and there are many catalyst particles and many adsorbent particles. It may be in a mixed state. However, in order to prevent carbon monoxide and hydrogen in the gas from passing through the processing cylinder 13 without coming into contact with the oxidation catalyst, the generated carbon dioxide and the carbon dioxide originally contained in the air and the generated carbon dioxide are also generated. It is necessary that both of them are evenly filled in the radial direction (direction perpendicular to the gas flow) of the processing cylinder 13 so that the generated water does not pass through without being adsorbed by the adsorbent. Furthermore, the mixing ratio of the two may be appropriately set depending on the treated amount of gas, the contents of carbon monoxide, hydrogen, carbon dioxide, water and the like in the gas, the filling amount of the mixture, etc., and is not particularly limited. Absent.

The space velocity (the value obtained by dividing the gas flow rate by the filling volume) of the portion filled with the mixture C of the oxidation catalyst and the adsorbent is preferably 2,000 to 50,000 h ^-1. If the speed is low, it is not economical, and if it is high, the reaction may not proceed sufficiently, which may cause a problem.

Furthermore, since the oxidation catalyst oxidizes carbon monoxide and hydrogen contained in the treatment gas and converts them into carbon dioxide and water, it is not possible to mix the oxidation catalyst with the purified gas outlet of the treatment cylinder. Undesirably, it is desirable to mix the catalyst in a portion below 300 to 500 mm from the uppermost portion of the adsorbent layer on the purified gas outlet side. That is, FIG.
As shown in (1), it is desirable to fill the adsorbent E for adsorbing and removing carbon dioxide and water in the latter part of the portion filled with the mixture C of the oxidation catalyst and the adsorbent and at the outlet side of the processing gas. As a result, it is possible to reliably prevent carbon dioxide and water generated by the catalytic reaction from mixing in the purified gas. In addition,
2, the same elements as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the adsorber of the air liquefaction separation apparatus, in many cases, a desiccant for removing water contained in the air is piled up at an appropriate filling height in the lower stage which is the raw air introduction side. It is filled with an adsorbent for removing carbon dioxide. As the adsorbent for removing carbon dioxide, usually, the zeolite is used, and not only carbon dioxide, but since it has the ability to adsorb water and various catalyst poison components produced in the catalytic reaction, When the present invention is applied to an adsorber for purifying raw material air of an air liquefaction separation apparatus, an oxidizing catalyst may be mixed and filled in the adsorbent for removing carbon dioxide.

The catalyst poison component trapped in the adsorbent covers the surface of the adsorbent as the use time increases, but the concentration of the target adsorbent component (mainly carbon dioxide) is the catalyst. Since it is much higher than the concentration of poisonous components,
It hardly affects the adsorption amount. Although not always confirmed, it is considered that some of the catalyst poison components have been desorbed and removed from the adsorbent in the adsorbent regeneration step.

When the present invention is applied to an adsorber for purifying raw material air of an air liquefaction / separation apparatus, an oxidation catalyst is mixed in the adsorbent layer. The operation can be performed in the same manner as a normal adsorber, and the adsorption-desorption system can be either a room temperature adsorption-heat desorption method (so-called TSA method) or a pressure adsorption-decompression desorption method (so-called PSA method). Is also applicable.
Further, various conditions such as the number of processing cylinders to be used, adsorption-regeneration switching time, adsorption temperature / pressure, regeneration temperature / pressure, etc. may be conditions designed on the premise of adsorption / removal of water and carbon dioxide.

Although the present invention can be applied to the case of removing carbon monoxide and hydrogen in various other gases, since the oxidation reaction is utilized, carbon monoxide is contained in the gas. The condition is that there is a sufficient amount of oxygen to convert hydrogen or hydrogen to carbon dioxide or water, and when the oxygen content is low, it is necessary to add oxygen gas or oxygen-containing gas in advance. .

Further, according to the present invention, both carbon monoxide and hydrogen can be removed at the same time, but only one of them can be removed depending on the quality requirement of the gas after purification. . In this case, the type of oxidation catalyst may be selected appropriately. Further, in the above-mentioned example, the present invention is applied to the adsorber of the air liquefaction separation device in which the desiccant is filled in the former stage, but if the adsorbent mixed with the oxidation catalyst can sufficiently remove water, the former stage The desiccant can be omitted, and the mixing ratio of the oxidation catalyst can be changed between the gas introduction side or the gas derivation side and the intermediate portion. Further, in the above-mentioned embodiment, the switching type adsorber which continuously performs the refining process has been described as an example, but it is also applicable to the batch process in which one processing cylinder is used.

Next, an experimental example of the present invention will be described. Experimental Example 1 10 kg of activated alumina as a desiccant and 15 kg of molecular sieves 13X as a carbon dioxide adsorbent were prepared, and an oxidation catalyst having platinum supported on activated alumina was uniformly mixed with the molecular sieves 13X at a weight ratio of 5: 1. Then, as shown in FIG. 1, activated alumina was filled in the gas introduction side of the processing cylinder, and molecular sieves mixed with an oxidation catalyst were filled in the gas discharge side.

The two processing cylinders were arranged as shown in FIG. 1, and the purification (adsorption) step and the regeneration step were repeated alternately by switching for 4 hours. In the adsorption process, the space velocity is about 1000.
At 0 h ^-1 , air containing 5 ppm of carbon monoxide was treated at room temperature, and in the regeneration step, purified air equivalent to 20% of the raw material air was used as the purge gas for regeneration, and the temperature was 15
Flowed at 0 ° C. As a result, the carbon monoxide in the purified air is
The detection limit of the measuring instrument was 0.5 ppm or less. Also,
Carbon dioxide was 1 ppm or less, and water was dew point −75 ° C. or less.

Experimental Example 2 10 kg of activated alumina was prepared as a desiccant and 15 kg of molecular sieves 13X was prepared as a carbon dioxide adsorbent. The molecular sieves 13X were divided into two equal parts by weight, and an oxidation catalyst in which platinum was supported on activated alumina in a half amount thereof. Were uniformly mixed in a weight ratio of 5: 2. Then, as shown in FIG. 2, from the gas introduction side of the processing cylinder, the activated alumina, the molecular sieves mixed with the oxidation catalyst, and the molecular sieves alone were filled in this order.

The two processing cylinders were arranged as shown in FIG. 2, and the purification (adsorption) step and the regeneration step were repeated alternately by switching for 4 hours. In the adsorption process, the space velocity is about 1000.
At 0 h ^-1 , air containing 5 ppm of carbon monoxide was treated at room temperature, and in the regeneration step, purified air equivalent to 20% of the raw material air was used as the purge gas for regeneration, and the temperature was 15
Flowed at 0 ° C. As a result, the carbon monoxide in the purified air is
The detection limit of the measuring instrument was 0.5 ppm or less. Also,
Carbon dioxide was 1 ppm or less, and water was dew point −75 ° C. or less.

Experimental Example 3 10 kg of activated alumina was prepared as a desiccant, and 15 kg of molecular sieves 13X was prepared as a carbon dioxide adsorbent. The molecular sieves 13X were divided into two equal parts by weight, and half of them were oxidized with palladium supported on activated alumina. The catalyst was uniformly mixed in a weight ratio of 5: 2. And FIG.
As shown in FIG. 5, from the gas introduction side of the treatment cylinder, activated alumina, molecular sieves mixed with an oxidation catalyst, and molecular sieves alone were filled in this order.

The two processing cylinders were arranged as shown in FIG. 2, and the purification (adsorption) step and the regeneration step were alternately repeated by switching for 4 hours. In the adsorption process, the space velocity is about 1000.
At 0 h ^-1 , air containing 5 ppm of carbon monoxide and 5 ppm of hydrogen was treated at room temperature, and in the regeneration step, purified air equivalent to 20% of the raw material air was used as a purge gas for regeneration, and flowed at a temperature of 150 ° C. . As a result, carbon monoxide and hydrogen in the purified air each had a detection limit of 0.5 ppm or less of the measuring instrument. Also, carbon dioxide is 1p
pm or less, and the water content was −75 ° C. or less.

[0031]

As described above, according to the gas purification method and apparatus of the present invention, the oxidation catalyst is mixed with the adsorbent and used, so that the component which becomes the catalyst poison can be adsorbed and removed by the adsorbent. Deterioration of the oxidation catalyst can also be suppressed by placing a desiccant in the previous stage to remove water beforehand, and by placing an adsorbent in the latter stage, carbon dioxide and water are mixed in the gas after purification. Can be surely prevented. This not only makes it possible to suppress deterioration of the oxidation catalyst and prolong its life significantly, but it also eliminates the need to heat the oxidation catalyst to increase its activity, thus significantly reducing equipment costs and energy costs. Therefore, it is optimal as a raw material air purification device for an air liquefaction separation device for producing extremely high-purity nitrogen gas used in the semiconductor industry and the like.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment in which the present invention is applied to an adsorber for purifying raw material air of an air liquefaction separation device.

FIG. 2 is a system diagram showing another embodiment.

FIG. 3 is a system diagram showing an example of a conventional raw material air purification device in an air liquefaction separation device.

[Explanation of symbols]

11 ... Gas introduction part, 12 ... Gas derivation part, 13 ... Processing cylinder C ... Mixture of oxidation catalyst and adsorbent, D ... Desiccant, E ... Adsorbent

Claims (4)

[Claims] 1. A method for purifying a gas for removing carbon monoxide and / or hydrogen contained in the gas, the oxidation for converting the carbon monoxide and / or hydrogen into carbon dioxide and / or water by a catalytic reaction. A method for purifying gas, which comprises bringing a gas into contact with a mixture of a catalyst and an adsorbent for adsorbing and removing carbon dioxide and water. 2. A gas purification apparatus for removing carbon monoxide and / or hydrogen contained in a gas, wherein the carbon monoxide and / or hydrogen is contained in a processing cylinder having an inlet and an outlet for the gas. An apparatus for purifying gas, comprising a mixture of an oxidation catalyst for converting carbon dioxide into carbon dioxide and / or water by a catalytic reaction and an adsorbent for adsorbing and removing carbon dioxide and water. 3. The gas purifying apparatus according to claim 2, wherein a desiccant for removing water in the gas is filled in a preceding stage of the mixture of the oxidation catalyst and the adsorbent. 4. The gas purifying apparatus according to claim 2, wherein an adsorbent for adsorbing and removing carbon dioxide and water is filled in the latter stage of the mixture of the oxidation catalyst and the adsorbent.