JPH10130010A - Purifying method of gaseous carbon dioxide and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove nitrogen oxide and CO by performing a catalytic reaction in the coexistence of plural specific gases to prevent the deterioration of the performance of a nitrogen oxide removing catalyst in a purifying method by removing impurities from a crude gaseous carbon dioxide containing at least nitrogen oxide and CO as the impurities. SOLUTION: The catalytic reaction of a reaction using preferably a noble metal (e.g. Pd) catalyst is performed in the coexistence of H2 and O2 under a prescribed pressure. That is, O2 is added simultaneously with or before or after the addition of H2 prior to the catalytic reaction, CO is allowed to react with O2 to convert to CO2 in the presence of the catalyst and at the same time, the reducing and removing reaction of nitrogen oxide is performed by H2 to prevent the lowering of the NO removing ratio caused by the obstruction due to the catalyst poisoning action of CO. That is, two catalytic reactions of the CO oxidation reaction and the nitrogen oxide reducing reaction are executed only in one process one time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for purifying carbon dioxide, and more particularly, to a crude carbon dioxide obtained by condensing a raw material gas with an alkanolamine absorption type carbon dioxide concentrator or a pressure fluctuation type adsorption separator (PSA apparatus). Gas,
The present invention further relates to a method and an apparatus for obtaining high-purity liquefied carbon dioxide gas by removing trace impurities such as nitrogen oxides, carbon monoxide, hydrocarbons, oxygen, nitrogen and the like which are further purified.

[0002]

2. Description of the Related Art High-purity carbon dioxide gas used as a raw material gas for the food industry and the chemical industry is generally used as a by-product gas in the synthesis of ammonia, an off-gas for hydrolysis of naphtha and the like in oil refining, a combustion gas such as a boiler, or the like. First, a crude carbon dioxide gas is obtained from an exhaust gas from steelmaking and refining by using an alkanolamine absorption method carbon dioxide gas concentrator or a pressure fluctuation type adsorption separator (PSA device), and then the crude carbon dioxide gas is purified to remove trace impurities. High purity carbon dioxide gas is obtained by removing.

An example of a conventional apparatus and method for purifying crude carbon dioxide from combustion gas by the alkanolamine absorption carbon dioxide concentrator will be described with reference to FIG. Table 1 shows an example of the composition of the raw material gas, for example, the combustion gas (after removing water).

[0004]

[Table 1]

As is apparent from Table 1, as undesirable components, trace amounts of carbon monoxide, nitrogen oxides (NOx), various sulfur compounds, oxygen, nitrogen and the like are contained. A trace amount of carbon monoxide may be intermittently mixed only for a certain period depending on the operating conditions of the apparatus. When carbon monoxide is contained in the raw material gas, for example, about 0.5 ppm or less, even if the crude carbon dioxide gas is purified by the pressure fluctuation adsorption separation device, it is contained in the crude carbon dioxide gas about 0.5 ppm or less. I will.

In the case of the alkanolamine absorption method using monoethanolamine, a raw material gas (combustion gas or the like) from the raw material gas source 1 is supplied to a monoethanolamine absorption type carbon dioxide concentration device (MEA absorption type CO ₂ concentration device). 2 to obtain a crude carbon dioxide gas. The MEA absorption type CO ₂ concentrating apparatus 2 includes a step of introducing the raw material gas into a washing tower and bringing the raw material gas into contact with an aqueous caustic soda solution flowing down from the top to separate impurities such as sulfur compounds contained in the raw material gas, A step of bringing the monoethanolamine solution and the like into countercurrent gas-liquid contact in an absorption tower to absorb carbon dioxide gas, a step of stripping the solution having absorbed the carbon dioxide gas in a regeneration tower to remove concentrated carbon dioxide gas, and washing with water. And washing and removing the residual amine in a tower to obtain a crude carbon dioxide gas.

[0007] The crude carbon dioxide gas obtained by the MEA absorption type CO ₂ concentrating apparatus 2 is usually 99.0% or more of carbon dioxide gas, and contains 0.01 to 1.0% of nitrogen and 0.1% as trace impurities. It contains 1 ppm to several hundred ppm of oxygen, a saturated amount of water, 1 to several ppm of nitric oxide, and 0.01 ppm or less of nitrogen dioxide. Although it is usually below the detection limit, an odor component, carbon monoxide, or the like may be temporarily contained as an impurity depending on operating conditions. This carbon monoxide is generated under the operating conditions as described above, and during the specific condition operation period, 0.5 to 3 pp is contained in the crude carbon dioxide gas.
m.

[0008] Of the nitrogen oxides mixed in the raw material gas, nitrogen dioxide is removed in the production process of the crude carbon dioxide gas and in the purification process of the next process. Is reduced but not completely removed, and a small amount of nitric oxide of about several ppm passes through a dryer and a deodorizer and reaches a liquefier / purifier (rectification tower), where the monoxide at the inlet of the rectification tower is reduced. When the nitrogen concentration becomes 0.5 ppm or more, nitrogen dioxide is generated in the presence of oxygen, and this nitrogen dioxide is mixed into the product liquefied carbon dioxide on the liquid phase side, and this is mixed with the product specification value, for example, 0.01%.
It may exceed ppm.

Therefore, in order to remove the trace impurities, the crude carbon dioxide gas obtained by the MEA absorption type CO ₂ concentrator 2 is hydrogenated before or after the CO ₂ compressor 3 as shown in FIG. While adding hydrogen by means 4, CO 2
_{(2) After} compressing to a predetermined pressure by the compressor 3 and heating to 80 to 100 ° C., the mixture is introduced into the catalytic reaction tube 5 filled with a noble metal catalyst, and nitrogen oxides (NOx) are decomposed into nitrogen and water by hydrogenation reduction. Catalytic reaction step, moisture removal step by dryer 6, odor component and remaining NOx by deodorizer 7
, And then purified by rectifying and separating low-boiling components such as oxygen, nitrogen and hydrogen contained in the liquefied purifier (rectification tower) 8 to obtain the product liquefied carbon dioxide gas. The product is stored in the liquefied carbon dioxide gas storage tank 9.

[0010]

When crude carbon dioxide is produced by a solution absorption method using monoethanolamine, carbon monoxide is generated depending on the operating conditions, and is contained in the crude carbon dioxide in an amount of about 0.5 to 3 ppm. It has been confirmed that the trace amount of carbon monoxide generated under these operating conditions inhibits the following reaction in the catalytic reaction step in which the nitrogen oxides (NOx) are hydrogenated and reduced into nitrogen and moisture. Was confirmed. 2NO + 2H ₂ → N ₂ + 2H ₂ O 2NO + 4H ₂ + O ₂ → N ₂ + 4H ₂ O NO ₂ + 2H ₂ → 1 / 2N ₂ + 2H ₂ O

That is, as described above, carbon monoxide is not only mixed into the product high-purity carbon dioxide through the rectification step,
When a small amount of carbon monoxide is present, the catalytic reaction of nitrogen monoxide in the raw material gas hardly proceeds in the catalytic reaction step, and passes through. Also, as a result of catalyst poisoning by carbon monoxide,
A reduction in catalytic activity occurs. For this reason, the nitric oxide that was not decomposed in the catalytic reaction step passed through the adsorption step after the catalytic reaction step because of its trace amount and reached the rectification separation step, where it was mixed with this nitric oxide and oxygen in the rectification column. Reacts to form nitrogen dioxide and shifts to the liquefied carbon dioxide gas side to lower the quality of the product liquefied carbon dioxide gas.

Accordingly, the present invention provides a method for purifying carbon dioxide and a method for purifying carbon dioxide, which can prevent a decrease in catalytic performance due to carbon monoxide in a catalytic reaction for decomposing and removing nitrogen oxides, thereby obtaining high-purity carbon dioxide. It is an object of the present invention to provide a purification device.

[0013]

According to a first aspect of the present invention, there is provided a method for removing impurities from crude carbon dioxide gas containing at least trace amounts of nitrogen oxides and carbon monoxide as impurities. In the method for purifying carbon dioxide, the nitrogen oxides and carbon monoxide are removed by performing a catalytic reaction at a predetermined pressure in the coexistence of hydrogen and oxygen.

The second method is a method of purifying carbon dioxide gas for removing impurities from crude carbon dioxide gas containing at least trace amounts of nitrogen oxides and carbon monoxide as impurities. Is introduced into an alkanolamine absorption carbon dioxide concentrator or a pressure fluctuation adsorption type separator (PSA), and the crude carbon dioxide containing impurities is catalyzed at a predetermined pressure in the presence of trace amounts of oxygen and hydrogen. A catalytic reaction step of decomposing or reacting trace impurities such as the nitrogen oxides and carbon monoxide by a reaction,
An adsorption step of removing trace impurities such as moisture contained in the crude carbon dioxide gas by adsorption, and a liquefaction purification step of separating trace amounts of low-boiling impurities such as oxygen, nitrogen and hydrogen by liquefied fractionation. It is characterized in that a product liquefied carbon dioxide is obtained by removing trace impurities from carbon dioxide.

Further, in the first and second methods, the presence of oxygen in the crude carbon dioxide gas is either present beforehand or added to the raw material gas. Similarly, the presence of hydrogen is determined in the step before the catalyst step. The catalytic reaction performed at the predetermined pressure is a reaction with a noble metal catalyst, and the temperature of the catalytic reaction is 50 to 100 ° C.
Preferably it is 60 to 90 ° C.

In the second method, the adsorbing step includes a first adsorbing step of removing trace impurity components such as water content by adsorption, and a remaining trace impurity component that cannot be removed in the first adsorbing step. And a second adsorption step for removal.

An apparatus for purifying carbon dioxide for achieving the object of the present invention is a carbon dioxide purifier for removing impurities from crude carbon dioxide containing at least trace amounts of nitrogen oxides and carbon monoxide as impurities. Hydrogen addition means for adding hydrogen to the crude carbon dioxide containing trace impurities obtained by introducing combustion gas or steelmaking or refined exhaust gas into an alkanolamine absorption type carbon dioxide concentrator or a pressure fluctuation type adsorption separator; Oxygen concentration detecting means for detecting the oxygen concentration in the gas and / or oxygen adding means for adding oxygen to the crude carbon dioxide gas; and trace impurities such as nitrogen oxides and carbon monoxide in the crude carbon dioxide gas and hydrogen and oxygen. Reaction column, an adsorber for removing impurities such as moisture generated in the catalyst reaction tube, and low boiling impurities such as oxygen, nitrogen and hydrogen contained therein. And a liquefaction purifier separating off the partial liquefaction rectification, is characterized by obtaining a product liquefied carbon dioxide to remove traces of impurities from the crude carbon dioxide gas.

Further, the oxygen adding means adds oxygen to the crude carbon dioxide gas in front of the catalytic reaction tube,
A carbon dioxide gas compressor for compressing crude carbon dioxide gas is provided at a stage preceding the catalyst reaction tube, and the catalyst filled in the catalyst reaction tube is a noble metal catalyst, or a platinum catalyst and / or a palladium catalyst. Features.

Further, the adsorber comprises a first adsorber and a second adsorber.
The second adsorber is configured to remove trace impurity components that cannot be removed by the first adsorber. The first adsorber and the second adsorber may be provided continuously. Often,
It may be provided with a catalyst reaction tube interposed. The first adsorber includes:
The second adsorber is filled with an adsorbent mainly composed of silica gel and / or alumina gel and activated carbon in this order. It is characterized by being mixed and filled with various kinds of adsorbents.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the above-described method for purifying carbon dioxide gas and the apparatus for purifying carbon dioxide gas of the present invention, crude carbon dioxide gas
Prior to the catalytic reaction step, oxygen is added at the same time as or before and after the addition of hydrogen (no oxygen is added if oxygen is already present in the crude carbon dioxide gas), and monoxide is added in the presence of hydrogen and oxygen. In addition to reacting carbon with oxygen to form carbon dioxide, a reductive decomposition reaction of nitrogen oxides can be simultaneously performed with hydrogen. As a result, it is possible to prevent the nitrogen oxide removal rate, which has been hindered by the catalyst poison of carbon monoxide, from decreasing. In other words, the two reactions can be performed only once in the catalytic reaction step, that is, the oxidation reaction of carbon monoxide and the reduction reaction of nitrogen oxide can be performed in one step. Hereinafter, the purification apparatus and method will be described in more detail with reference to FIG.

The embodiment of the apparatus for purifying carbon dioxide shown in FIG. 1 uses a source gas (combustion gas, etc.) from a source gas source 11.
Monoethanolamine absorption carbon dioxide concentrator (MEA absorption CO ₂ concentrator) to obtain crude carbon dioxide gas
A CO ₂ compressor 13 is provided at the subsequent stage of the CO ₂ compressor 13 for adding a small amount of hydrogen to the crude carbon dioxide gas and an oxygen adding means 15 for adding oxygen to the crude carbon dioxide gas and compressing the crude carbon dioxide gas to a predetermined pressure. Is provided. CO ₂
In the subsequent stage of the compressor 13, a catalytic reaction tube 16 for reacting hydrogen and oxygen with trace impurities such as nitrogen oxides and carbon monoxide in the pressurized crude carbon dioxide gas, A first adsorber 17 for removing impurities, a second adsorber 18 for removing trace impurity components that could not be removed by the first adsorber 17, and liquefaction purification of low-boiling impurity components such as oxygen, nitrogen and hydrogen. A liquefied purifier (rectification tower) 19 that separates by distillation and a product liquefied carbon dioxide gas storage tank 20 that stores purified liquefied carbon dioxide gas obtained by the liquefied purifier 19 are provided in this order.

The addition of hydrogen by the hydrogen addition means 14 is performed before the catalyst reaction tube 16 because it is used for the catalytic reaction. Therefore, hydrogen is added by the hydrogen addition means 14 before either the CO ₂ compressor 13 or the catalyst reaction tube 16. Further, the addition of oxygen by the oxygen adding means 15 is also performed before the catalytic reaction column 16 because it is used for the catalytic reaction. Therefore, CO
₍₂₎ Oxygen is added by the oxygen adding means 15 in front of either the compressor 13 or the catalytic reaction tube 16.

Further, an oxygen concentration detecting means 21 for measuring the oxygen content in the crude carbon dioxide gas at this point is provided at the outlet of the monoethanolamine absorption type carbon dioxide gas enrichment device 12. And the oxygen adding means 15
Is for adding oxygen to the crude carbon dioxide gas based on the oxygen concentration detection value of the oxygen concentration detection means 21. If the oxygen concentration in the crude carbon dioxide gas is about several tens ppm, the oxygen addition means 15
The oxygen addition means 15 is not required, and the oxygen addition means 15 can be omitted. Depending on the oxygen concentration in the crude carbon dioxide gas, the oxygen concentration detection means 21 may be omitted and the oxygen addition means 15 may be omitted.
, A predetermined amount of oxygen may be continuously added. Further, the control of the amount of oxygen added by the oxygen adding means 15 can be automatically performed based on the detected value of the oxygen concentration in the source gas. The oxygen may be any gas containing oxygen, for example, air.

Further, the first adsorber 17 is filled with an adsorbent mainly composed of silica gel and / or alumina gel. The second adsorber 18 has an adsorbent mainly composed of silica gel and / or alumina gel at the inlet side of the container and an adsorbent suitable for removing odorous components such as activated carbon at the outlet side which is the upper layer of the container. Or an adsorber filled with an adsorbent mainly composed of silica gel and / or alumina gel and an adsorber filled with activated carbon may be connected in series, or a plurality of adsorbents may be used. You may mix and fill. As the catalyst filled in the catalyst reaction tube 16, a noble metal catalyst is suitable, and among them, a platinum catalyst and / or a palladium catalyst is preferable.

Next, an embodiment of a method for purifying carbon dioxide using this apparatus for purifying carbon dioxide will be described. First,
A raw material gas (combustion gas or the like) from a raw material gas source 11 is introduced into a monoethanolamine absorption type carbon dioxide gas concentration device (MEA absorption type CO ₂ concentration device) 12 to obtain a crude carbon dioxide gas. In this step, the raw material gas is introduced into the washing tower and brought into contact with an aqueous solution of caustic soda flowing down from the top of the column to separate impurities such as sulfur compounds contained in the raw material exhaust gas. Then, the solution is introduced into an absorption tower and brought into contact with an absorbing solution, for example, a monoethanolamine solution in a countercurrent gas-liquid state, to absorb carbon dioxide gas, and then heat-treating the solution absorbing the carbon dioxide gas in a regeneration tower. The concentrated carbon dioxide is removed by stripping, and the remaining amine is washed with a washing tower to obtain a crude carbon dioxide.

The crude carbon dioxide obtained by the MEA absorption type CO ₂ concentrator 12 is usually 99.0% or more of carbon dioxide and 0.01 to 1.0% of nitrogen and 0.1% as trace impurities. 1 ppm to several 100 ppm of oxygen, saturated amount of moisture, 1 to several ppm of nitric oxide, 0.01 ppm
The following nitrogen dioxide is contained. Also, depending on the operating conditions, a very small amount of carbon monoxide, an odor component, etc. is contained as an impurity. The carbon monoxide generated under the operating conditions is contained in the crude carbon dioxide gas at about 0.5 to 3 ppm during the operation under the specific conditions.

Next, the MEA absorption type CO ₂ concentrator 12
The process enters a purification step for removing trace impurities from the crude carbon dioxide gas obtained in the above. A small amount of oxygen for oxidizing carbon monoxide in the catalytic reaction step is added to the crude carbon dioxide gas entering the purification step by the oxygen addition means 15. The oxygen adding means 15 may be optional, and the oxygen adding portion is not necessarily limited to the CO ₂ compressor 1.
It is not necessary to be before 3 and it is sufficient that it is before the catalytic reaction tube 16 such as after the CO ₂ compressor 13. Further, an oxygen compressor may be used as a means for introducing oxygen, and its choice is free. The added amount of oxygen is set to several tens ppm.

The crude carbon dioxide gas entering the refining process includes:
A small amount of hydrogen for decomposing nitrogen oxides is added by the hydrogenation means 14 in the catalytic reaction step. The hydrogenation means 14 may be optional, and the hydrogenation site is not necessarily CO 2
Need not be before the _second compressor 13, CO ₂ compressor 13
For example, after the catalyst reaction tube 16. In addition, a hydrogen compressor can be freely selected as a means for introducing hydrogen. The amount of hydrogen added may be slightly greater than the stoichiometric amount with respect to the amount of nitrogen oxide and the amount of oxygen. Excess hydrogen is separated and removed in the liquefaction rectification step in the liquefaction purifier 19.

Next, the crude carbon dioxide gas is to compress the pressure required for this purification step, a CO ₂ compressor 13 28 kg
/ Cm ² G. The compression pressure in this compression step may be any pressure required for all steps of the purification step, and is usually in the range of about 5 to 30 kg / cm ² G, and
Particularly preferred is a range of from 30 kg / cm ² G to 30 kg / cm ² G.

Subsequently, pressurized crude carbon dioxide gas was supplied to the catalyst reaction tube 1.
6 to perform a catalytic reaction step. At this time, the pressurized crude carbon dioxide gas is heated to 80 ° C. by a heat exchanger, a heater, etc., and introduced into a catalytic reaction tube 16 filled with a noble metal catalyst, oxidizing carbon monoxide and simultaneously nitric oxide. To reduce. In this step, the contained carbon monoxide becomes carbon dioxide, and the contained nitric oxide is reduced and rendered harmless by the following reaction. The catalyst may be a noble metal catalyst such as rhodium, ruthenium, gold, silver or the like in addition to platinum or palladium. When using platinum or palladium, the catalyst reaction temperature is suitably in the range of about 50 to 100 ° C, preferably 60 to 90 ° C. 2NO + 2H ₂ → N ₂ + 2H ₂ O 2NO + 4H ₂ + O ₂ → N ₂ + 4H ₂ O NO ₂ + 2H ₂ → 1 / 2N ₂ + 2H ₂ O

The crude carbon dioxide gas which has completed the catalytic reaction step is
After being introduced into the first adsorber 17 and entering the first adsorption step, it is accompanied by the above-mentioned crude carbon dioxide gas production step, and is not separated by the water separator after the compression step. Remove moisture and the like. In this step, the water content is removed to a dew point of -60 ° C or lower.

Next, although not an essential step, in view of safety in quality assurance, crude carbon dioxide gas is introduced into the second adsorber 18 to perform the second adsorption step, to remove residual moisture and to perform the first adsorption step. Removal of trace amounts of odor components and the like that could not be removed by
That is, in the normal operation, water generated in the catalytic reaction step in the catalytic reaction tube 16 and odor components which cannot be removed in the first adsorption step and which are mixed below the detection limit under operating conditions are removed. If no odor component is contained,
It is natural that there is no need to fill a deodorizing adsorbent such as activated carbon. The first adsorber 17 and the second adsorber 18 are:
Each is a two cylinder switching type, one cylinder is in the adsorption process,
A continuous operation is performed by using the other cylinders alternately with the regeneration process.

Further, by providing an adsorption step before the catalytic reaction step, in the case of the monoethanolamine absorption method and the carbon dioxide gas concentration method, acetaldehyde mixed in the solution absorption step is removed, and propylene is formed into propylene by the catalytic reaction. Mixing into gas can be prevented. That is, the first adsorber 17 may be provided in front of the catalyst reaction tube 16 and the second adsorber 18 may be provided immediately after the catalyst reaction tube 16.

The crude carbon dioxide gas after the completion of the second adsorption step is
The heat is exchanged with the released gas in a heat exchanger (not shown), cooled to a predetermined temperature (for example, 10 ° C.), liquefied in a liquefier (not shown), and liquefied and purified in the rectification separation step (rectification). (Tower) 19, and low-boiling components such as oxygen, nitrogen and hydrogen contained therein are rectified and separated, collected at the top of the tower and discharged. The liquefied carbon dioxide gas separated at the bottom of the tower is derived from a liquefier / purifier (rectification tower) 18 and stored in a product liquefied carbon dioxide gas storage tank 20.

The product liquefied carbon dioxide purified and separated as described above has the product purity shown in the following examples, and a product having a high purity greatly exceeding the value of the Food Sanitation Law standard (food additive standard value) is obtained. Can be

It should be noted that the embodiment of the present invention is not limited to the above, and a new purification step may be inserted between the respective steps, which is also within the scope of the present invention.

[0037]

EXAMPLE Table 2 shows the results of measuring the concentration of impurities contained in the conventional method according to FIG. 2 in the case of producing a product liquefied carbon dioxide gas by purifying a combustion gas. Table 3 shows the results of measuring the concentrations.

The sampling position of the sample gas to be analyzed in the conventional method shown in FIG. 2 is as follows: sampling position: boiler flue (combustion gas) sampling position: CO ₂ compressor 3 outlet (crude carbon dioxide gas) sampling position: catalytic reaction tube 5 Outlet (carbon dioxide) Sampling position: 4 places of liquefier / purifier (rectification tower) 8 (product liquefied carbon dioxide).

[0039]

[Table 2]

The sampling position of the sample gas to be analyzed in the method of the present embodiment according to FIG. 1 is as follows: sampling position: boiler flue (combustion gas) sampling position: outlet of CO ₂ compressor 13 (crude carbon dioxide gas) sampling position: catalyst Outlet of reaction tube 16 (carbon dioxide) Sampling position: 4 places of liquefier / purifier (rectification tower) 19 outlet (product liquefied carbon dioxide).

[0041]

[Table 3]

As is clear from the above analysis values, when only a small amount of carbon monoxide is present in only one stage of the catalytic reaction step, it is possible to simultaneously remove nitrogen monoxide by the catalytic reaction. It is considered that the oxidation of carbon monoxide and the reduction of nitrogen monoxide proceed simultaneously in the presence of palladium catalyst in the coexistence of oxygen and hydrogen. As shown in Table 3, all the trace impurities contained were below the detection limit. Nitric oxide is also below the detection limit.
001 ppm or less. It should be noted that substantially the same results were obtained when platinum was used as the catalyst.

The high-purity carbon dioxide gas purified according to the present invention is suitable not only as a gas for foods and drinks but also as a dry ice gas, as well as a raw material gas for the chemical industry and a welding atmosphere gas. It can also be used as a stirring gas in steelmaking.

[0044]

As described above, according to the method for purifying carbon dioxide gas and the apparatus for purifying carbon dioxide gas of the present invention, oxygen is added at the same time as or before and after the addition of hydrogen before the catalytic reaction step. The presence of oxygen allows carbon monoxide to react with oxygen to form carbon dioxide, while at the same time reducing and removing nitrogen oxides with hydrogen. As a result, it is possible to prevent a decrease in the nitrogen monoxide removal rate which has been hindered by the catalyst poison of carbon monoxide. That is,
Two reactions, an oxidation reaction of carbon monoxide and a reduction reaction of nitrogen oxides, can be performed in one step only once in the catalytic reaction step.

Therefore, according to the present invention, high-purity carbon dioxide gas can be obtained with a simple apparatus configuration while preventing the catalytic performance of the nitrogen oxide removal catalytic reaction by carbon monoxide from decreasing.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a method and an apparatus for purifying carbon dioxide gas of the present invention.

FIG. 2 is a diagram illustrating an example of a conventional method and apparatus for purifying carbon dioxide.

[Explanation of symbols]

12: monoethanolamine absorption method carbon dioxide gas concentrator (MEA absorption CO ₂ concentrator), 13: CO ₂ compressor, 14: hydrogenation means, 15: oxygen addition means, 16 ...
Catalytic reaction tube, 17: first adsorber, 18: second adsorber, 1
9 liquefaction refiner (rectification tower), 20 liquefied carbon dioxide gas storage tank,
21 ... Oxygen concentration detecting means

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Akio Kajiwara 2-51-3 Akabane, Kita-ku, Tokyo Liquefied Carbonated Inc. (72) Inventor Kaoru Koshibe 2-51-3 Akabane, Kita-ku, Tokyo Liquefaction Carbonated Inc.

Claims (12)

[Claims] In a method for purifying carbon dioxide gas for removing impurities from crude carbon dioxide gas containing at least trace amounts of nitrogen oxides and carbon monoxide as impurities, a catalytic reaction is carried out at a predetermined pressure in the coexistence of hydrogen and oxygen. A method for purifying carbon dioxide, wherein the nitrogen oxides and carbon monoxide are removed by performing the method. 2. A method for purifying carbon dioxide gas for removing impurities from crude carbon dioxide gas containing at least trace amounts of nitrogen oxides and carbon monoxide as impurities. A catalytic reaction step of decomposing or reacting the trace impurity components such as the nitrogen oxides and carbon monoxide by a catalytic reaction at a predetermined pressure in the presence of, and adsorbing the trace impurity components such as moisture contained in the crude carbon dioxide gas. Removal of trace impurities from crude carbon dioxide gas to obtain product liquefied carbon dioxide gas by adsorption step for removal and liquefaction purification step for separating trace amounts of low-boiling impurities such as oxygen, nitrogen and hydrogen by liquefied fractionation A method for purifying carbon dioxide. 3. The adsorption step includes a first adsorption step of removing trace impurity components such as water content by adsorption, and a second adsorption step of removing residual trace impurity components that cannot be removed in the first adsorption step. 3. The method for purifying carbon dioxide gas according to claim 2, comprising: 4. The method for purifying carbon dioxide according to claim 1, wherein the catalytic reaction performed at the predetermined pressure is a reaction using a noble metal catalyst. 5. The temperature of the catalytic reaction is 50 to 100.
The method for purifying carbon dioxide according to claim 1 or 2, wherein the temperature is ° C. 6. A carbon dioxide gas purifying apparatus for removing impurities from crude carbon dioxide gas containing at least trace amounts of nitrogen oxides and carbon monoxide as impurities, wherein hydrogenation means for adding hydrogen to the crude carbon dioxide gas, Oxygen concentration detection means for detecting the oxygen concentration in the crude carbon dioxide gas and / or oxygen addition means for adding oxygen to the crude carbon dioxide gas, and trace impurities such as nitrogen oxides and carbon monoxide in the crude carbon dioxide gas and hydrogen And a catalyst reaction tube for reacting with oxygen, and an adsorber for removing impurities such as moisture generated in the catalyst reaction tube,
A liquefaction purifier that separates and removes low-boiling impurities such as oxygen, nitrogen and hydrogen by liquefaction rectification, and obtains product liquefied carbon dioxide by removing trace impurities from crude carbon dioxide. Carbon dioxide purification equipment. 7. The apparatus for purifying carbon dioxide according to claim 6, wherein the catalyst filled in the catalytic reaction tube is a noble metal catalyst. 8. The apparatus for purifying carbon dioxide according to claim 6, wherein the catalyst filled in the catalytic reaction tube is a platinum catalyst and / or a palladium catalyst. 9. The adsorber comprises a first adsorber and a second adsorber, and the second adsorber removes trace impurity components that could not be removed by the first adsorber. An apparatus for purifying carbon dioxide according to claim 6, wherein 10. The first adsorber comprises silica gel and / or
10. The apparatus for purifying carbon dioxide according to claim 9, wherein the apparatus is filled with an adsorbent containing alumina gel as a main component. 11. The second adsorber comprises silica gel and / or silica gel.
10. The apparatus for purifying carbon dioxide according to claim 9, wherein an adsorbent mainly composed of alumina gel and activated carbon are stacked and filled. 12. The carbon dioxide purifying apparatus according to claim 9, wherein said second adsorber is formed by mixing and filling a plurality of types of adsorbents.