Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Carbon dioxide or hydrogen sulfide component
Reexamination Certificate
1998-12-09
2003-07-08
Dunn, Tom (Department: 1754)
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Carbon dioxide or hydrogen sulfide component
C423S220000, C423S246000, C423S247000, C423S248000
Reexamination Certificate
active
06589493
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a gas purification-treating agent and a gas purifying apparatus, more specifically to a gas purification-treating agent and a gas purifying apparatus which remove carbon monoxide and/or hydrogen contained in a gas by effecting oxidation reaction in the presence of oxygen, and which also remove carbon dioxide and/or water formed by the oxidation reaction together with carbon dioxide and/or water contained originally in the gas, and particularly to a gas purification-treating agent and a gas purifying apparatus, in a system where air is sucked and compressed and the compressed gas is fed as a raw gas to an air separation plant, which effect oxidization of carbon monoxide and/or hydrogen to remove such impurities from the compressed air.
Conventionally, when carbon monoxide and/or hydrogen contained in a gas are/is to be removed, it is carried out generally to remove first the substantial part of water contained originally in the gas, i.e. the water formed by condensation under compression, and then to convert carbon monoxide and/or hydrogen by catalytic reaction into carbon dioxide and/or water which are/is then removed by adsorption together with the residual water of condensation and carbon dioxide contained originally in the gas.
For example, in an air separation plant for producing oxygen, nitrogen, etc., the impurities such as water and carbon dioxide contained in the raw air are removed by adsorption to an adsorbent such as activated alumina and zeolite. However, carbon monoxide and hydrogen which are contained each in an amount of about 1 to 5 ppm in the atmospheric air cannot be removed by using the adsorbent for adsorbing and removing carbon dioxide and water. Meanwhile, it is difficult to remove carbon monoxide by means of distillation, because the boiling point of carbon monoxide is close to that of nitrogen, so that carbon monoxide remains as an impurity in the product nitrogen, resulting in the failure of producing a high-purity nitrogen gas, disadvantageously. Meanwhile, hydrogen, which has a low boiling point, can be separated by means of distillation. However, a distillation plate must be additionally installed so as to achieve separation of nitrogen and hydrogen.
Accordingly, as shown in
FIG. 12
, raw air supplied to an air inlet
1
is introduced through a filter
2
and a passage
3
to an air compressor
4
to be compressed there, and the compressed raw air is fed through an after-cooler
5
and a water separator
6
and further through a passage
7
to a preheater
8
which is a heat exchanger and then introduced through a passage
9
to a heater
10
to be heated there. The thus treated raw air is introduced through a passage
11
to a catalyst column
12
where it is brought into contact with a carbon monoxide oxidizing catalyst and a hydrogen oxidizing catalyst to effect reaction with the oxygen contained in the air and to convert carbon monoxide and hydrogen into carbon dioxide and water respectively. The compressed air which contained carbon dioxide and water is then introduced through a passage
13
to the preheater
8
where their temperatures are lowered, and after they are introduced through passages
14
and
15
to a cooler
16
and cooled therein, they are further introduced through a passage
17
and through either a passage
18
a
or
18
b
to either an adsorption unit
19
a
or an adsorption unit
19
b
where carbon dioxide and water contained originally in the raw air supplied are adsorbed and removed, by an adsorbent packed in the adsorption unit
19
a
or that in the unit
19
b
, together with the carbon dioxide and water formed by catalytic oxidation. The raw air thus purified is designed to be supplied through either a passage
20
a
or a passage
20
b
and through a passage
21
to an air separation plant
22
.
In the case where. a catalyst layer is incorporated in the system as shown in
FIG. 12
, the atmospheric air is brought into contact with the catalyst without going through any purifying means, so that the catalyst is deteriorated by catalyst poisons such as sulfur oxides contained in the atmospheric air. Accordingly, catalysts are used under heating as a measure for maintaining the catalytic activity. However, this requires electric power for heating a large amount of air, and even if the heat quantity required is reduced by heat recovery, a large heat exchanger is necessary for the recovery.
Meanwhile, in order to minimize the influence of catalyst poisons, it can be expected to install an adsorption unit for adsorbing and removing carbon dioxide and water contained originally in the air on the upstream side of the catalyst layer for catalyzing oxidation of carbon monoxide and/or hydrogen. According to this procedure, many catalyst poison can be removed by the purification action of the adsorbent, and the life of the catalyst can be improved. However, in this case, an extra adsorbent layer for adsorbing and removing carbon dioxide formed by oxidation of carbon monoxide and water formed by oxidation of hydrogen must be incorporated on the downstream side of the catalyst layer, requiring a high facility cost.
There are an affluence of literatures on oxidation catalysts for carbon monoxide and hydrogen describing a number of useful catalysts (e.g., Y. Murakami's, “SHOKUBAI REKKA MEKANIZUMU TO BOSHI TAISAKU (Catalyst Deterioration Mechanism and Its Prevention)”, published by Gijutsu-Joho Kyokai, 1995). In these literatures, there are general descriptions of the deterioration of catalysts (reduction in the catalytic activities), but there is found no literature describing deterioration of catalysts in removing very small amount of carbon monoxide and hydrogen contained in the atmospheric air as is discussed in the present invention.
Under the present circumstances, catalysts are maintained at high temperatures of 100° C. or higher in the conventional gas purifying apparatuses so as to maintain their activities based on the general consideration on catalytic reactions. However, in order to reduce electric power consumption rate in cryogenic separation of air, it is economically disadvantageous to heat a large amount of air as described above, and there has been expected an advent of catalysts having high activities of oxidizing carbon monoxide and/or hydrogen in the temperature range of about 5 to 50° C. and an apparatus enabling extended use of catalysts without deterioration.
OBJECT AND SUMMARY OF THE INVENTION
It is an objective of the invention to provide a gas purification-treating agent and a gas purifying apparatus which can remove carbon monoxide and/or hydrogen from a gas employing no special equipment.
Another objective of the invention is to provide a gas purifying apparatus realizing simplification of the conventional intricate pretreatment purification procedures including removal of carbon dioxide and water from a gas having passed through a carbon monoxide/hydrogen removing catalyst column, and downsizing of the apparatus.
The gas purification-treating agent and gas purifying apparatus for removing carbon monoxide and/or hydrogen contained in a gas according to the present invention are of the following constitutions and actions.
A first aspect of the present invention is a gas purification-treating agent for treating carbon monoxide and/or hydrogen contained in a gas in the presence of oxygen, and the agent consists of an adsorbent having carbon dioxide and/or water adsorptivity, and a metal or metal compound, carried thereon, which activates oxidation reaction of carbon monoxide and/or hydrogen. The adsorbent adsorbs carbon dioxide and/or water contained originally in the gas, as well as, carbon dioxide and/or water to be formed by the oxidation reaction of carbon monoxide and/or hydrogen. By subjecting the gas to purification treatment with this gas purification-treating agent, the carbon monoxide and/or hydrogen contained in the gas are/is oxidized in the presence of oxygen by the metal or metal compound which activates the
Hosaka Shoichi
Kawai Masato
Samata Chie
Armstrong Westerman & Hattori, LLP
Dunn Tom
Ildebrando Christina
Nippon Sanso Corporation
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