JPH09264666A - Nitrogen and oxygen manufacturing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nitrogen and oxygen manufacturing system to economically manufacture high purity liquid nitrogen containing no carbon monoxide by reducing an amount of a using catalyst for removing carbon monoxide as much as possible. SOLUTION: Raw material air 1 is fractionated and separated into nitrogen and oxygen by a fractionating tower 19. After a liquid nitrogen raw material 4a being a part of product nitrogen gas 4a sampled from the top part of a low pressure tower 21 of the fractionating tower 19 is compressed and boosted in three stages by compressors 36, 37, and 38, the liquid nitrogen raw material is liquefied through the passage of it through a heat-exchanger 40, an expansion valve 41, and a gas liquid separator 42 to manufacture liquid nitrogen 4f. In this case, by selectively passing a liquid nitrogen raw material 4b, passing through the first stage compressor 36, through one of catalyst towers, the liquid nitrogen raw material makes contact with a nickel catalyst to adsorb and remove carbon monoxide and thereafter, guided as high purity nitrogen gas 4c, containing no carbon monoxide, to the second stage compressor 37.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitrogen / oxygen production system for producing oxygen and nitrogen by rectification from air as a raw material, and in particular, a nitrogen / oxygen production system capable of obtaining nitrogen gas and liquid nitrogen as product nitrogen. It relates to an oxygen production system.

[0002]

2. Description of the Related Art This type of nitrogen / oxygen production system generally produces nitrogen gas and oxygen gas (or liquid oxygen) by rectifying and separating raw material air with an air separation device equipped with a rectification tower. In addition, a part of the nitrogen gas obtained by the air separation device is condensed and liquefied by the liquid nitrogen manufacturing device to manufacture liquid nitrogen.

That is, the air separation device converts raw material air into
Carbon dioxide and water originally contained in this are adsorbed and removed by an adsorption device, then cooled to near the boiling point and introduced into the rectification column, and the rectification action in the rectification column causes the product gases, nitrogen gas and oxygen. It is configured to obtain gas (or liquid oxygen). Further, the liquid nitrogen production device uses a part of the product nitrogen gas obtained by the air separation device as the liquid nitrogen raw material, and the liquid nitrogen raw material introduced from the air separation device is stepwise by a plurality of compressors. Liquid nitrogen, which is product nitrogen, is manufactured by increasing the pressure to 2, cooling to near the liquefaction point, expanding, and separating gas and liquid.

By the way, since liquid nitrogen is often used in the field of semiconductor manufacturing in recent years, it is generally required to have high purity. On the other hand, the product nitrogen gas obtained in the rectification column is not required to have high purity like liquid nitrogen for its use, and its necessity is small. That is, since nitrogen gas can be made highly pure as needed by users who receive it as a product, it is necessary to make it highly pure at the manufacturing stage, unlike liquid nitrogen. There is little sex.

However, in the above system using a part of the product nitrogen gas collected from the rectification tower as the liquid nitrogen raw material, the liquid nitrogen obtained by the liquid nitrogen production apparatus contains carbon monoxide. However, it cannot be used for applications requiring high purity, such as in the field of semiconductor manufacturing. That is, since the boiling points of nitrogen and carbon monoxide are similar (nitrogen is −195.8 ° C., whereas carbon monoxide is −191.5 ° C.), rectification in a standard type rectification column is performed. Depending on the action, it is extremely difficult to completely separate the two. Therefore, the product nitrogen gas collected from the air separation device contains carbon monoxide (generally, contains 0.5 to 1.5 mol ppm of carbon monoxide), and as a result, this Naturally, carbon monoxide will also be included in the liquid nitrogen made from.

Therefore, in the conventional nitrogen / oxygen production system, a high-purity liquid containing almost no carbon monoxide is obtained by oxidizing and removing carbon monoxide from the feed air supplied to the rectification column in advance. It has been proposed to obtain nitrogen. That is, on the inlet side of the adsorption device described above,
By providing a carbon monoxide oxidizer equipped with a catalyst tower loaded with a noble metal catalyst such as platinum or palladium, and contacting the raw air with the noble metal catalyst in the catalyst tower, the carbon monoxide contained therein is exchanged with oxygen. By the reaction, it is converted into carbon dioxide, and this carbon dioxide is adsorbed and removed by the adsorption device together with carbon dioxide (and water) originally contained in the raw material air.

In this way, by supplying the raw material air containing no carbon monoxide to the rectification column, a high-purity product nitrogen gas containing almost no carbon monoxide can be obtained from the rectification column. . As a result, the liquid nitrogen obtained by the liquid nitrogen manufacturing apparatus using a part of the product nitrogen gas as a raw material becomes a high purity containing almost no carbon monoxide, and the semiconductor manufacturing field etc. which is required to have a high purity. Can also be used favorably.

[0008]

However, in the case where such a carbon monoxide oxidation device is provided, it is required that most of the nitrogen gas collected from the rectification column has high purity as described above. Despite being used as a product nitrogen gas that is not required or required, in order to keep the liquid nitrogen obtained from a very small part of the nitrogen gas as a raw material with high purity that does not contain carbon monoxide. , It is a catalyst for carbon monoxide removal, that is, a catalyst for carbon monoxide oxidation, to remove carbon monoxide from air, which is a raw material for all rectification products including product nitrogen gas and liquid nitrogen raw material. The amount of precious noble metal catalyst used is unnecessarily large, which is extremely uneconomical and wasteful. Therefore, in the conventional nitrogen / oxygen production system, it is not possible to economically produce high-purity liquid nitrogen required in the semiconductor production field and the like.

The present invention has been made in view of the above circumstances, and a high-purity liquid nitrogen containing no carbon monoxide,
It is an object of the present invention to provide a nitrogen / oxygen production system which can be economically produced by reducing the amount of carbon monoxide removal catalyst used as much as possible.

[0010]

The nitrogen / oxygen production system of the present invention which has solved this problem is an air separation device for rectifying and separating raw material air into nitrogen and oxygen, and nitrogen obtained by the air separation device. A liquid nitrogen production apparatus that produces liquid nitrogen by using a part of the gas as a liquid nitrogen raw material, and a liquid that adsorbs and removes carbon monoxide contained in the liquid nitrogen raw material introduced from the air separation device to the liquid nitrogen production apparatus by the action of a catalyst. And a nitrogen source refining device.

In such a nitrogen / oxygen production system, the liquid nitrogen raw material refining apparatus is provided with a catalyst tower loaded with a nickel catalyst, and carbon monoxide contained in the liquid nitrogen raw material is brought into contact with the nickel catalyst. It is preferable to remove by adsorption. Further, the liquid nitrogen production apparatus is provided with a plurality of compressors for increasing the pressure of the liquid nitrogen raw material introduced therein over a plurality of stages, and the liquid nitrogen raw material refining apparatus is an outlet part of the first stage compressor. It is preferably interposed between and the inlet of the second-stage compressor.

[0012]

FIG. 1 is a block diagram showing an embodiment of the present invention.
~ It demonstrates concretely based on FIG.

The nitrogen / oxygen production system according to the present invention is
As shown in FIG. 1, it comprises an air separation device 11, a liquid nitrogen production device 12, and a liquid nitrogen raw material purification device 13.

As shown in FIGS. 1 and 2, the air separation device 11 sequentially passes the raw material air 1 through the air filter 14, the compressor 15, the washing tower 16, the adsorbing device 17, and the main heat exchanger 18. The nitrogen gas 4 and the oxygen gas 7a as product gases are obtained by introducing them into the rectification column 19 and rectifying and separating nitrogen and oxygen in the rectification column 19.

That is, the raw material air 1 is the air filter 1
After being filtered in step 4, the compressor 15 presses an appropriate pressure (adsorption device).
The pressure required for the adsorption by the device 17 (generally 5 kg /
cm ^TwoG))) and the water is cooled in the water washing tower 16.
(Generally below 10 ° C), then introduced into adsorption device 17
Is done. The adsorption device 17 is loaded with an adsorbent such as zeolite.
It consists of a pair of adsorption towers 17a, 17a
Is introduced into one of the adsorption towers 17a and brought into contact with the adsorbent.
As a result, it is an unnecessary component contained in the raw material air 1.
To absorb and remove water and carbon dioxide
You. In this adsorption device 17, one adsorption tower 17a
While performing the adsorption process, the other adsorption tower 1
7a is an adsorbent due to the introduction of a regeneration purge gas 5 described later.
It is designed to perform the regeneration process of
And the regeneration process between the adsorption towers 17a, 17a at a fixed cycle.
It is designed to be repeated alternately for each clou
You.

The raw material air 1 that has passed through the adsorption device 17 is cooled to near the boiling point in the main heat exchanger 18 and then introduced into the rectification column 19. The main heat exchanger 18
Is an internal refrigeration system in which the raw material air 1 is cooled by heat exchange with a low temperature gas (product nitrogen gas 4 etc.) which is discharged from the rectification column 19 as described later.

As shown in FIG. 2, the rectification column 19 has an appropriate internal pressure (5 kg / g) equivalent to the pressure of the raw material air 1 introduced therein.
a high pressure tower 20 which is a lower tower operated at about cm ² G),
A lower pressure column 21, which is an upper column and is operated at an appropriate internal pressure (about 0.5 kg / cm ² G) lower than this, both columns 20,
It is equipped with the main condenser evaporator 22 interposed between 21, and the raw material air 1 is rectified and separated as follows. That is, the raw material air 1 that has passed through the main heat exchanger 18 is introduced into the lower part of the high pressure column 20, and while rising in the high pressure column 20,
The nitrogen concentration is increased by the countercurrent contact with the reflux liquid nitrogen 3a supplied from the upper part of the column, and reaches the upper part of the high pressure column 20 to become the nitrogen gas 2 having a low oxygen content. This nitrogen gas 2 is introduced into the main condenser evaporator 22 from the upper part of the high pressure column 20, and is cooled and condensed by heat exchange with the liquid oxygen 7 retained in the bottom part of the low pressure column 21 to become liquid nitrogen 3. A part of the liquid nitrogen 3 is refluxed to the upper part of the high pressure column 20 as the above-mentioned reflux liquid nitrogen 3a, and is introduced into the upper part of the low pressure column 21 through the heat exchanger 23.

On the other hand, the reflux liquid nitrogen 3a supplied from the upper portion into the high-pressure column 20 descends while making countercurrent contact with the rising air component in the high-pressure column 20, as described above. The oxygen concentration is increased by contact with the air, and the liquid air 6 (oxygen concentration is generally about 35 to 40%) is retained at the bottom of the high-pressure column 20. A part 6 a of the liquid air 6 passes through the heat exchanger 23 from the bottom of the high pressure column 20, and is then supplied to the middle part of the low pressure column 21. The rectification column 19 is equipped with an argon purification device including a crude argon column 24, a high-purity argon column 25, a blower 26, a drying column 27, a tank 28, etc., and the low-pressure column 2
Argon or the like concentrated and accumulated in the intermediate portion of 1 is re-refined, and is collected and stored in the tank 28 as liquid argon 8.

Thus, the rising component of the liquid air 6a supplied to the intermediate portion of the low pressure column 21 increases the nitrogen concentration by countercurrent contact with the reflux liquid nitrogen 3 supplied from the upper part of the low pressure column 21. Ascending, the nitrogen gas 4 having an extremely low oxygen concentration is formed at the top of the low-pressure column 21. This nitrogen gas 4 is sampled from the top of the low pressure column 21 and brought to room temperature by the main heat exchanger 18, and then passes through the product nitrogen gas supply passage 30 through the compressor 31 to a predetermined supply point (product nitrogen gas) ( It is supplied to the industrial complex). In addition, from the upper part of the low-pressure column 21, a part of the nitrogen gas rising toward the top (oxygen concentration is higher than the product nitrogen gas 4 reaching the top) 5 is collected, and the nitrogen gas 5 is subjected to main heat exchange. Vessel 18 and heater 5a,
After passing through 5a, it is introduced as a purge gas for regeneration into the adsorption tower 17a in the regeneration step.
In addition, the main condenser evaporator 2 collected from the upper part of the high-pressure column 20
A part 2a of the nitrogen gas 2 introduced into the main heat exchanger 1
After passing through 8, the pressure is increased by the braking portion 32a of the expansion turbine 32 and is expanded by the turbine portion 32b of the turbine 32 to generate cold, and then the top of the low pressure column 21 is directed to the main heat exchanger 18. It is mixed with nitrogen gas 4. In addition, in FIG. 1 and FIG. 2, 32 'is a heat exchanger.

On the other hand, the descending component of the liquid air 6a supplied to the intermediate portion of the low pressure column 21 descends in the low pressure column 21 while increasing the oxygen concentration, and becomes oxygen gas 7a in the lower part of the low pressure column 21, Further, it becomes liquid oxygen 7 and stays at the bottom of the low pressure column 21. Then, the oxygen gas 7a collected from the lower part of the low pressure column 21 passes through the main heat exchanger 18 and is cooled to room temperature, and then passes through the compressor 34 from the product oxygen gas supply passage 33 to be a predetermined product oxygen gas. It is supplied to the supply destination. In addition, the oxygen gas 7 a collected from the lower part of the low pressure column 21 includes the liquid oxygen 7 a accumulated at the bottom of the low pressure column 21.
Volatilized from (nitrogen gas 2 passing through the main condenser evaporator 22)
Oxygen gas is also included.

As shown in FIGS. 1 and 3, the liquid nitrogen producing apparatus 12 produces liquid nitrogen 4f by using a part 4a of the product nitrogen gas 4 taken from the top of the low pressure column 21 as a liquid nitrogen raw material. , First to third compressors 36, 37, 38
a, first and second expansion turbines 38 and 39, and heat exchanger 4
0, expansion valve 41, gas-liquid separator 42, and liquid nitrogen tank 43
In addition to the above, the liquid nitrogen raw material refining apparatus 13 is incorporated as described later.

That is, the liquid nitrogen raw material 4a, which is a part of the product nitrogen gas 4, is introduced into the liquid nitrogen production apparatus 12 from the liquid nitrogen raw material introduction passage 35 which is branched and connected to the product nitrogen gas supply passage 30. This liquid nitrogen raw material is nitrogen gas 4
First, a is the first to third compressors 36, 3 arranged in series.
7, 38a sequentially compresses and boosts pressure in three stages. Generally, 5-6 kg / c depending on the first compressor 36
The pressure is increased to about m ² G, then to about 32 kg / cm ² G by the second compressor 37, and finally to about 49 kg / cm ² G by the third compressor 38 a. In this example, the braking portion of the first expansion turbine 38 for generating cold, which will be described later, is used as the third compressor 38a.

The nitrogen gas 4e that has passed through the third compressor 38a is deep-cooled to near the liquefaction point by the heat exchanger 40, expanded by the expansion valve 41 (Joule-Thomson expansion), and separated into gas and liquid. The gas and liquid separator 42 is separated from the gas content by the container 42 to produce liquid nitrogen 4f which is product nitrogen.
Are collected and stored in the liquid nitrogen tank 43.

By the way, in this example, the heat exchanger 40 is of an internal cold type, and a part 4 g of the nitrogen gas 4d passing through the second compressor 37 toward the third compressor 38a.
Is compressed and boosted by the braking part 39a of the second expansion turbine 39, and then expanded by the turbine parts 38b, 39b of the first and second expansion turbines 38, 39 to generate cold 4h, which is then transferred to the heat exchanger. It is devised to supply 40. The nitrogen gas 4h passing through the heat exchanger 40 is the second
It is designed to be returned to the inlet side line of the compressor 37.

As shown in FIGS. 3 and 4, the liquid nitrogen raw material refining apparatus 13 has an outlet of the first compressor 36 and the second compressor 3.
7, a pair of catalyst towers 45a and 45b in which a catalyst 46 is loaded are arranged in parallel with each other, and the nitrogen gas 4b passing through the first compressor 36 is fed to the selected catalyst tower 45.
It passes through a (or the catalyst tower 45b) and is introduced into the second compressor 37. Any catalyst can be used as long as it can adsorb and remove carbon monoxide in the nitrogen gas, and a base metal catalyst such as nickel or iron can be arbitrarily used. Generally, the target nitrogen gas is the low pressure column 2.
Since it is the nitrogen gas 4 having an extremely low oxygen concentration collected from the top of 1, the coexistence of oxygen for oxidation is not required for the adsorption and removal action of carbon monoxide, and the adsorption operation and the regeneration operation can be easily performed. It is preferable to use a nickel catalyst (for example, a columnar pellet having a nickel content of 47 wt%, a diameter of 3 mm and a length of 3 mm).

Thus, the nitrogen gas 4b passing through the first compressor 36 is introduced into one catalyst tower 45a and passes through the inside of the catalyst tower 45a while being in contact with the nickel catalyst 46 loaded therein. During this time, carbon monoxide is adsorbed and removed by contact with the nickel catalyst 46. At the same time, a trace amount of oxygen contained in the nitrogen gas 4b is also adsorbed and removed. It is considered that the mechanism of adsorption and removal of carbon monoxide by the nickel catalyst 46 is due to chemical adsorption on the nickel catalyst surface as a nickel carbonyl-like compound having a significantly smaller number of carbon monoxide coordination numbers in terms of stoichiometric ratio. To be By the way, nickel catalyst 4
In order to effectively carry out the adsorption and removal of carbon monoxide by No. 6, it is necessary to properly control the pressure and temperature of the nitrogen gas introduced into the catalyst tower 45a. Regarding the temperature, a heater attached to the catalyst tower 45a is required. The temperature is controlled (not shown) (generally, it is preferable to control at room temperature to about 40 ° C.). On the other hand, the pressure is generally preferably set to 5 to 6 kg / cm ² G, but in this example, the liquid nitrogen raw material 4 a is compressed by the compressors 36, 3
Since the pressure is increased in multiple stages by 7, 38a, and the pressure increasing condition by the first compressor 36 which is the first-stage compressor matches the pressure condition required for the adsorption removal described above, the catalyst tower 4
No special means for pressurizing the nitrogen gas to be introduced into 5a is provided, and the nitrogen gas 4b whose pressure has been increased by the first compressor 36 is directly introduced into the catalyst tower 45a. It should be noted that the nitrogen gas 4b is 0.3% in the catalyst tower 45a (or the catalyst tower 45b).
Nickel catalyst 46 while passing at a linear velocity of about m / sec
It is preferable to keep it in contact with.

Therefore, according to the liquid nitrogen raw material refining apparatus 13, the nitrogen gas 4b that has passed through the first compressor 36 is purified to the high-purity nitrogen gas 4c from which carbon monoxide has been removed, and then the second compressor 37. That is, the high-purity nitrogen gas flows in the liquid nitrogen production line after the second compressor 37, and finally high-purity liquid nitrogen 4f containing no carbon monoxide is obtained. be able to.

By the way, "adsorption and removal of carbon monoxide by the nickel catalyst 46 is considered to be due to chemical adsorption on the nickel catalyst surface as a nickel carbonyl-like compound as described above" and "liquid nitrogen raw material 4a".
In other words, the nitrogen gas 4b introduced into the catalyst tower 45a has a very low oxygen concentration taken from the top of the low pressure tower 21, but since it contains a trace amount of oxygen, this trace amount of oxygen is Since it reacts with the nickel catalyst 46 to generate nickel oxide ”, in order to maintain a good adsorption and removal action of carbon monoxide over a long period of time, it is necessary to regenerate the nickel catalyst 46 having a reduced adsorption function. Is required. Therefore, in this example, the nickel catalyst 46 in the other catalyst tower 45b (or the catalyst tower 45a) is regenerated while performing the adsorption step in the one catalyst tower 45a (or the catalyst tower 45b), and It is devised that the regeneration step and the catalyst towers 45a and 45b are alternately repeated at regular intervals.

That is, while the adsorption step is being carried out in one catalyst tower 45a, a part 4'of the high-purity nitrogen gas 4c from the catalyst tower 45a toward the second compressor 37.
c is used as a reducing gas mixed with a predetermined amount (about 1%) of hydrogen gas by the hydrogen supply device 47, and then supplied to the other catalyst tower 45b as a purge gas for regeneration, and the nickel catalyst of the catalyst tower 45b is supplied. 46 is regenerated under suitable temperature conditions (generally 150-200 ° C). That is, the surface of the nickel catalyst 46 is regenerated to the reduced state. At this time, it is possible to use a gas other than the purified gas 4c described above as the purge gas for regeneration, but since the one containing carbon monoxide cannot be used, the purified gas 4c is used only for the purpose of regeneration. Without downsizing the playback mechanism,
It is also preferable in terms of simplification. Then, after a certain period of time, the nitrogen gas 4b is introduced into the regenerated catalyst tower 45b and the purge gas 4'c is supplied to the catalyst tower 45a after the adsorption step. After that, the switching between the adsorption process and the regeneration process is repeated at regular intervals. The adsorption process and the regeneration process can be switched automatically by controlling a valve or heater provided in the equipment line with a sequence program device, but even if the switching timing is set by a timer, Either control may be performed according to the carbon monoxide concentration in the nitrogen gas 4c by the carbon monoxide concentration sensor installed at the outlet of the catalyst tower. In addition, the recycled barge gas 4
′ C is cooled to an appropriate temperature by the cooler 48 and then discharged to the outside of the system. Although not shown, a filter, a flow meter, etc. are provided in the purified gas line or the like as needed.

As described above, in the above-mentioned nitrogen / oxygen production system, the liquid nitrogen raw material from which carbon monoxide (and oxygen) has been removed by the liquid nitrogen production apparatus 12 and the liquid nitrogen raw material refining apparatus 13 incorporated therein. 4a, 4b, 4c
Since the liquid nitrogen 4f is manufactured from ..., High-purity liquid nitrogen required in the semiconductor manufacturing field can be reliably obtained. Moreover, the liquid nitrogen raw materials 4a, 4b, 4c ... Required for producing the liquid nitrogen 4f are a part of the product nitrogen gas 4 obtained in the rectification column 19, and are extremely small compared to the raw material air 1 ( For example, 1 / of the raw air
Since it is about 10), as compared with the case where carbon monoxide is removed from the total amount of feed air by the carbon monoxide oxidizing device (and the adsorbing device) as described at the beginning, the catalyst required for removing carbon monoxide. The amount used can be greatly reduced, and product nitrogen and oxygen containing liquid nitrogen 4f can be manufactured extremely economically.

The present invention is not limited to the above-described embodiments, but can be appropriately improved and changed without departing from the basic principle of the present invention. For example, the present invention can be suitably applied not only to the above-mentioned internal cold type system but also to an external cold type system. Further, the configurations of the devices 11, 12, and 13 are also arbitrary. Further, the liquid nitrogen raw material refining apparatus 13 may be installed in the introduction line of the liquid nitrogen raw material 4a up to this, without being incorporated in the liquid nitrogen manufacturing apparatus 12.

[0032]

EXAMPLE Liquid nitrogen 4f was produced under the following conditions using the above-mentioned nitrogen / oxygen production system. That is, the water and carbon dioxide were removed by the adsorption device 17
Raw material air 1 of 4000 Nm ³ / h, 5 kg / cm ² G was cooled to near the boiling point in the main heat exchanger 18 and introduced into the high-pressure column 20, and the inside of the high-pressure column 20 was reduced to 5 kg / cm ² G and the low-pressure column 2
While maintaining 0.5 kg / cm ² G inside 1, the raw air 1 is rectified and separated into nitrogen and oxygen by the rectification column 19, and the low pressure column 2
From the top of 1 to 36 kg of nitrogen gas 4 of 0.5 kg / cm ² G
000 Nm ³ / h was sampled, the nitrogen gas 4 was brought to room temperature (28 ° C.) in the main heat exchanger 10, and a part 4 a thereof was first
It was introduced into the compressor 36. At this time, the amount of the nitrogen gas 4a introduced into the first compressor 36 was 7300 Nm ³ / h, and the concentrations of carbon monoxide and oxygen as impure components contained therein were carbon monoxide: 1 molppm and oxygen: 0.0
It was 1 molppm.

The nitrogen gas 4a is fed to the first compressor 3
6, the pressure was increased to 5.8 kg / cm ² G, the pressure was increased, and the temperature was cooled to near room temperature (28 ° C.). Then, the columnar nickel catalyst 46 (Ni content: 47 wt.
%, Diameter: 3 mm, length: 3 mm)
5a, and a linear velocity of 0.3 m / s in the catalyst tower 45a.
The carbon monoxide and oxygen were adsorbed and removed by contact with the nickel catalyst 46.

Next, the nitrogen gas 4c (excluding the nitrogen gas 4'c used as a purge gas for regeneration of the other catalyst tower 45b) passing through the catalyst tower 45a is compressed to 32 kg / cm ² G by the second compressor 37, The pressure is increased, and the pressure is increased to 49 by the braking unit 38a of the first expansion turbine 38 which is the third compressor.
After compressing and increasing the pressure to kg / cm ² G, heat exchanger 40
After being deeply cooled to near the liquefaction point by passing through the expansion valve 41 and the gas-liquid separator 42, 70
Liquid nitrogen 4f of 00 Nm ³ / h was obtained.

At this time, the liquid nitrogen 4f flowing down from the gas-liquid separator 42 to the liquid nitrogen tank 43 was continuously measured by a reducing gas analyzer (RGA-5 type manufactured by Trace Analytical Co.). Carbon monoxide maintained 0.001 molppm or less, which is the limit value of quantification. Further, when oxygen analysis was performed using API-MS manufactured by Hitachi Tokyo Electronics Co., the oxygen concentration was 0.001 molpp.
It was m or less. From this, high purity liquid nitrogen 4f
It was confirmed that

By the way, as a comparative example, the liquid nitrogen raw material refining apparatus 12 is removed from the nitrogen / oxygen production system, the outlet of the first compressor 36 and the inlet of the second compressor 37 are directly connected, and adsorption is performed. In the upstream line of the device 17,
The carbon monoxide oxidizer described in the beginning (equipped with a catalyst column loaded with a noble metal catalyst) was incorporated to obtain the same amount of liquid nitrogen under the same conditions as described above. In this comparative example, in order to obtain high-purity liquid nitrogen equivalent to that of the example, an extremely large amount of noble metal catalyst was required as compared with the case of the example. Specifically, it was about 10 times the amount of nickel catalyst 46 used in the examples. This means that in the comparative example, the target gas for adsorbing and removing carbon monoxide was 74000 Nm ³ /
It can be easily understood from the fact that the raw material air of h is about 10 times the amount of nitrogen gas which is the target gas in the example (7300 Nm ³ / h).

[0037]

As can be understood from the above description, according to the invention of claim 1, a large amount of high-purity liquid nitrogen containing no carbon monoxide is added to the catalyst for removing carbon monoxide such as a nickel catalyst. It can be manufactured very economically without the need. Moreover, since the amount of catalyst used is small, it is possible to miniaturize the liquid nitrogen raw material refining device including the catalyst tower as much as possible, and as a result, the entire nitrogen / oxygen production system is supplied with the total amount of raw material air as described at the beginning. The size can be greatly reduced as compared with the case where the target carbon monoxide oxidation device is provided.

According to the second aspect of the invention, carbon monoxide can be effectively adsorbed and removed regardless of the properties of the liquid nitrogen raw material, such as the liquid nitrogen raw material having a low oxygen concentration.
High-purity liquid nitrogen can be efficiently produced.

Further, according to the invention of claim 3, as a pressurizing means necessary for effectively adsorbing and removing carbon monoxide, a part of the liquid nitrogen production apparatus (the first stage compressor,
Specifically, since the above-mentioned first compressor 36) is used, no special pressurizing means is required, and the liquid nitrogen raw material refining apparatus or the nitrogen / oxygen production system can be made smaller and simpler.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of a nitrogen / oxygen production system according to the present invention.

FIG. 2 is an enlarged view of a main part (air separation device) of FIG.

FIG. 3 is an enlarged view of a main part (a liquid nitrogen manufacturing apparatus and a liquid nitrogen raw material refining apparatus) of FIG.

FIG. 4 is a detailed view of a main part (liquid nitrogen raw material refining apparatus) of FIG.

[Explanation of symbols]

1 ... Raw material air, 4 ... Product nitrogen gas, 4a, 4b ... Nitrogen gas containing carbon monoxide (liquid nitrogen raw material), 4c, 4
d, 4e ... Nitrogen gas from which carbon monoxide has been adsorbed and removed (liquid nitrogen raw material), 4f ... Liquid nitrogen, 7a ... Product oxygen gas, 1
DESCRIPTION OF SYMBOLS 1 ... Air separation apparatus, 12 ... Liquid nitrogen manufacturing apparatus, 13 ... Liquid nitrogen raw material purification apparatus, 36 ... 1st compressor (1st stage compressor), 37 ... 2nd compressor (2nd stage compressor), 45a,
45b ... Catalyst tower, 46 ... Nickel catalyst.

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[Procedure amendment]

[Submission date] April 1, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0032

[Correction method] Change

[Correction contents]

[0032]

EXAMPLE Liquid nitrogen 4f was produced under the following conditions using the above-mentioned nitrogen / oxygen production system. That is, the water and carbon dioxide were removed by the adsorption device 17
Raw material air 1 of 4000 Nm ³ / h, 5 kg / cm ² G was cooled to near the boiling point in the main heat exchanger 18 and introduced into the high-pressure column 20, and the inside of the high-pressure column 20 was reduced to 5 kg / cm ² G and the low-pressure column 2
While maintaining 0.5 kg / cm ² G inside 1, the raw air 1 is rectified and separated into nitrogen and oxygen by the rectification column 19, and the low pressure column 2
From the top of 1 to 36 kg of nitrogen gas 4 of 0.5 kg / cm ² G
000 Nm ³ / h was sampled and this nitrogen gas 4 was used as the main heat exchanger.
After making room temperature (28 ° C) at 18 , part 4a is first
It was introduced into the compressor 36. At this time, the amount of the nitrogen gas 4a introduced into the first compressor 36 was 7300 Nm ³ / h, and the concentrations of carbon monoxide and oxygen as impure components contained therein were carbon monoxide: 1 molppm and oxygen: 0.0
It was 1 molppm.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeshi Goto, 3-2-35 Hinode, Itako-cho, Ikata-gun, Ikata-ken 5-6-14 Inventor Hiroshi Matsuzaki, 5-6-14 Hinode, Itako-cho, Whereabout-gun, Ibaraki Prefecture

Claims (3)

[Claims] 1. An air separation device for rectifying and separating raw material air into nitrogen and oxygen, and a liquid nitrogen production device for producing liquid nitrogen using a part of nitrogen gas obtained by the air separation device as liquid nitrogen raw material. And a liquid nitrogen raw material refining device for adsorbing and removing carbon monoxide contained in the liquid nitrogen raw material introduced into the liquid nitrogen producing device from the air separation device by the action of a catalyst. . 2. A liquid nitrogen raw material purification apparatus is provided with a catalyst tower loaded with a nickel catalyst, and carbon monoxide contained in the liquid nitrogen raw material is adsorbed and removed by contact with the nickel catalyst. The nitrogen / oxygen production system according to claim 1, which is characterized. 3. The liquid nitrogen production apparatus is provided with a plurality of compressors for increasing the pressure of the liquid nitrogen raw material introduced therein in plural stages, and the liquid nitrogen raw material purification apparatus is a first stage compressor. The nitrogen / oxygen production system according to claim 1 or 2, wherein the nitrogen / oxygen production system is interposed between the outlet of the second compressor and the inlet of the second-stage compressor.