JP2003119009A - Method for producing nitrogen gas and equipment therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for easily and inexpensively producing high purity nitrogen gas or two nitrogen gases of different purities. SOLUTION: An equipment for producing nitrogen gas is composed of a hollow fiber membrane 40 in which compressed air is fed to leave nitrogen gas and a deoxidization chamber 50 with formed iron powder in which the left nitrogen gas is fed to increase the purity of the nitrogen gas.

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 producing nitrogen gas, and more specifically, it produces nitrogen gas of high purity and two types of nitrogen gas of high purity easily and inexpensively. It is about technology.

[0002]

2. Description of the Related Art Conventionally, there have been generally three types of techniques relating to a method and an apparatus for producing nitrogen gas: a PSA method, a membrane separation method, and a deep-chill separation method.

Among them, the PSA method is called Pressur.
e Swing Adsorption, which is an abbreviation for adsorbent that passes compressed air through an adsorbent that is a type of activated carbon, adsorbs a specific gas under high pressure, and expels a specific gas under low pressure. It is a method of separating nitrogen by adsorbing oxygen and the like from compressed air by utilizing the characteristics. In this case, the device has the same principle as that of the heatless dryer, the device is a two-cylinder type and is larger than the membrane separation type, and a maintenance load on the solenoid valve is also applied. The nitrogen purity was usually about 99 to 99.9999%.

On the other hand, in the membrane separation system, compressed air is sent into a hollow fiber membrane, which is a hollow fiber polymer membrane, and the difference in permeation amount of each gas component contained in the compressed air to the membrane is utilized. This is a method of separating nitrogen. In this case, the size is smaller and the maintenance load is smaller than the PSA method, but the nitrogen purity is 9
Since it is about 5 to 99.9%, it was not suitable for high purity needs.

Further, the deep-chill separation system is intended for a large quantity and needs of high purity, and air is cooled to separate and generate.
For example, when the temperature of air is around -190 ° C, the boiling point of nitrogen is -195.8 ° C and the boiling point of oxygen is -183.
Since the temperature is 0 ° C, oxygen is liquefied and can be separated out. In this case, high purity nitrogen of 99.999% or more can be obtained,
Large scale equipment was required. On the other hand, in addition to transportation by tank lorry, there was also adopted a method of installing a plant on the premises of a large user's factory or on an adjacent site, and piping.

[0006]

However, the above-mentioned conventional method and apparatus for producing nitrogen gas have the following problems.

First, in the case of the PSA system, the size of the device becomes large and there is a difficulty in maintaining the device such as the solenoid valve.

Next, in the case of the membrane separation system, the nitrogen purity is 95.
Since it is about 99.9%, it was not suitable for high purity needs.

Finally, in the case of the cryogenic separation system, 99.99
High-purity nitrogen of 9% or more was obtained, but large-scale equipment was required.

[0010]

The present invention is characterized in that compressed air is brought into contact with iron powder to form iron oxide, whereby oxygen in the compressed air is reduced and nitrogen gas remains. Furthermore, characterized by adding a catalyst to the iron powder, further characterized in that the catalyst is sodium chloride, further characterized by adding water to the iron powder, further, The above problem was solved by firstly passing the compressed air through a hollow fiber membrane and bringing the residual nitrogen gas into contact with the iron powder to further increase the purity of the nitrogen gas.

Further, according to the present invention, the hollow fiber membrane 40 for leaving the nitrogen gas by feeding compressed air and the deoxidizing chamber in which the iron powder for feeding the remaining nitrogen gas to make the nitrogen gas highly pure is formed. 50, further, water is formed in the deoxidizing chamber 50, and a catalyst is also formed in the deoxidizing chamber 50. Further, the hollow fiber membrane 40 is made of polyimide, and the catalyst is sodium chloride. Furthermore, a branch portion 122 is provided between the hollow fiber membrane 40 and the deoxidation chamber 50. The above-mentioned problem is solved by providing a nitrogen gas and producing two kinds of purity nitrogen gas 153 and 154.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A method and an apparatus for producing nitrogen gas according to the present invention will be described in detail with reference to the drawings. Here, FIG. 1 is an overall view of an embodiment showing the present invention,
FIG. 2 is a diagram showing a relationship between an oxygen meter concentration and an aeration time when another embodiment of the present invention is carried out.

As shown in FIG. 1, reference numeral 10 denotes a compressor, which is not specifically shown, but is composed of an electric motor and a compressor main body, and the rotation of the electric motor is transmitted to the compressor main body via a belt. The compressed air is generated by sucking the atmosphere 151 and stored in an air tank (not shown). In this case, the air tank may be arranged in the compressed air pipes 101, 102, 103 or downstream thereof, instead of being integrally formed with the compressor 10.

Here, the compressed air stored in the air tank of the compressor 10 includes compressed air piping 101, a prefilter 20 for removing foreign matters in the compressed air, the compressed air piping 102, and small foreign matters in the compressed air. It is configured to be fed into the hollow fiber membrane 40 via the micro mist filter 30 for removing the air and the compressed air pipe 103. A dryer for drying the compressed air may be arranged between the compressor 10 and the prefilter 20.

In this case, when the pre-filter 20 has a capability of removing large foreign matters of 3 μ or more existing in the compressed air, the micro mist filter 30 has small foreign matters of 0.01 μ or more existing in the compressed air. Is desired, and in some cases, an activated carbon filter capable of removing the odor in the compressed air may be disposed downstream of the micromist filter 30. However, the capabilities of the filters 20 and 30 are not limited to the listed capabilities.

On the other hand, the hollow fiber membrane 40 is formed of a bundle of thousands of straw-shaped hollow fibers made of polyester, and each gas has its own characteristic by passing compressed air through the hollow fibers. This is a device that makes use of the difference in the permeation speed of the hollow fiber membranes to leave the most nitrogen gas contained in the air.

In this case, the gas that constitutes the compressed air permeates the hollow fiber membrane at a speed at which gas is released quickly and gas which is difficult to release, and the remaining gas is nitrogen gas. In particular, when the hollow fiber membrane is made of polyester, water vapor is most permeable, followed by hydrogen and helium, followed by carbon dioxide and carbon monoxide, and finally oxygen, argon, and nitrogen. It is difficult to survive, and nitrogen gas is the most difficult gas to pass through.

If the temperature does not change, the purity of the nitrogen gas produced depends on the pressure and time of the compressed air, that is, the flow rate.

As the hollow fiber membrane, resins such as polyolefin and polypropylene can be considered in addition to polyester.

Here, the nitrogen gas left by the compressed air passing through the hollow fiber membrane 40 is the nitrogen gas pipe 12
It is configured to reach the branching portion 122 after passing through 1.

Further, two piping systems are constructed from the branch section 122. The one piping system comprises the nitrogen gas first branch pipe 123, the opening / closing valve 131, and the nitrogen gas first branch pipe 124.

Further, as another piping system, the nitrogen gas second branch pipe 125, the opening / closing valve 132, and the nitrogen gas second branch pipe 1
26, the deoxidation chamber 50, the high-purity nitrogen gas pipe 127, the oxygen concentration meter 133, and the high-purity nitrogen gas pipe 128.

Here, the purpose of the on-off valves 131 and 132 is to
By opening / closing the opening / closing valves 131 and 132, one of the two piping systems can be selected.

On the other hand, the deoxygenation chamber 50 provided at the tip of the second branch pipe 126 for nitrogen gas removes a small amount of oxygen contained in the nitrogen gas remaining as the compressed air passes through the hollow fiber membrane 40. It is provided for the purpose of in this case,
In the deoxidizing chamber 50, iron powder, sodium chloride as a catalyst for promoting the oxidation reaction of iron, and a small amount of water for promoting the oxidation reaction of iron are formed.

As the deoxidizing chamber 50, various cases such as only iron powder, iron powder and catalyst, iron powder and water, etc. can be considered. In addition to sodium chloride, other catalysts such as potassium chloride are also conceivable as the catalyst.

The method and apparatus for producing nitrogen gas according to the present invention is constructed as described above, and its operation will be described below.

First, by operating the compressor 10, the atmosphere 151 is taken in and compressed air is produced. Here, the produced compressed air is sent to the hollow fiber membrane 40 via the compressed air pipe 101, the prefilter 20, the compressed air pipe 102, the micro mist filter 30, and the compressed air pipe 103. Therefore, the foreign matter that deteriorates the hollow fiber membrane 40 is removed by the pre-filter 20 and the micro mist filter 30.

On the other hand, in the hollow fiber membrane 40, water vapor, hydrogen, helium, carbon dioxide gas, carbon monoxide, argon, etc. are removed from the oxygen contained in the compressed air, and nitrogen gas remains and is sent out. . That is, oxygen-rich gas 1
The gas centering on oxygen is discharged at 52, and the remaining nitrogen gas is sent out to the nitrogen gas pipe 121. The purity of this nitrogen gas is about 95 to 99.9%, which is slight. Contains oxygen.

In this case, the nitrogen gas sent out from the hollow fiber membrane 40 passes through the nitrogen gas pipe 121 and the branch portion 12
Reach 2. Here, in the branch portion 122, a piping system leading to the on-off valve 131 via the nitrogen gas first branch pipe 123 and an on-off valve 132 via the nitrogen gas second branch pipe 125.
It is divided into another piping system leading to.

Therefore, the on-off valve 131 is opened to open the on-off valve 13.
When 2 is closed, the nitrogen gas delivered from the hollow fiber membrane 40 can be used as it is as the nitrogen gas 153 from the nitrogen gas first branch pipe 124. The nitrogen gas 153 in this case has a purity of about 95 to 99.9%.

On the other hand, the on-off valve 131 is closed and the on-off valve 132 is closed.
Is opened, the nitrogen gas sent out from the hollow fiber membrane 40 is sent into the deoxidizing chamber 50 through the nitrogen gas second branch pipe 126. Here, the nitrogen gas sent in contains a small amount of oxygen, but reacts with the iron forming the deoxidizing chamber 50 to form iron oxide, and thereby reduces the oxygen, thereby sending in the nitrogen gas. The purity of.

In this case, when a small amount of water is added to iron, the oxidation reaction of iron is promoted, and when a catalyst such as sodium chloride is added, the oxidation reaction of iron is promoted. Of course, the addition of water and the catalyst will further accelerate the reaction.

In this way, the nitrogen gas sent out from the hollow fiber membrane 40 and sent into the deoxidizing chamber 50 has a higher purity, and the high-purity nitrogen gas pipe 127, the oxygen concentration meter 133, and the high-purity nitrogen gas pipe 128 are connected. Via high-purity nitrogen gas 15
4 can be used. The high-purity nitrogen gas 154 in this case can have a purity of about 99 to 99.99%.

Here, the purpose of disposing the oxygen concentration meter 133 is to determine the purity of the nitrogen gas. On the other hand, the oxidizing ability of the deoxidizing chamber 50 deteriorates over time. Therefore, the oximeter 133
It is also provided to determine when to replace the iron, water, or catalyst forming the deoxidizing chamber 50.

As another embodiment of the present invention, FIG.
It is also conceivable that the compressed air pipe 101 is connected to the deoxidizing chamber 50. That is, the compressor 10, the compressed air pipe 101, the deoxidizing chamber 50, the high-purity nitrogen gas pipe 127, the oxygen concentration meter 133, and the high-purity nitrogen gas pipe 128.
It is a structure. With this structure, nitrogen gas having a certain degree of purity can be obtained even in the deoxidizing chamber 50 alone.

That is, as shown in FIG. 2, generally, 18
Up to the 0th minute, the deoxidizing chamber 50 alone can produce nitrogen gas of a considerable degree of purity.

[0037]

As is apparent from the above description, the following effects can be achieved by the present invention.

First, the idea of the deoxidizing chamber 50 has made it possible to produce inexpensive and highly pure nitrogen gas.

Secondly, by passing compressed air through two devices, the hollow fiber membrane 40 and the deoxidizing chamber 50, it becomes possible to produce nitrogen gas of high purity at low cost.

Thirdly, by providing the branch portion 122,
It became possible to supply different types of nitrogen gas.

[Brief description of drawings]

FIG. 1 is an overall view of an embodiment showing the present invention.

FIG. 2 is a diagram showing a relationship between an oximeter concentration and an aeration time when another embodiment of the present invention is carried out.

[Explanation of symbols]

10 ... Compressor 20 ... Prefilter 30 ... Micro mist filter 40 ... Hollow fiber membrane 50 ... Deoxygenation chamber 101 ... Compressed air piping 102 ... Compressed air piping 103 ... Compressed air piping 121 ・ ・ ・ ・ ・ Nitrogen gas piping 122 ... Branching part 123 ... Nitrogen gas first branch pipe 124 ... Nitrogen gas first branch pipe 125: Nitrogen gas second branch pipe 126-Nitrogen gas second branch pipe 127 ... High-purity nitrogen gas piping 128: High-purity nitrogen gas piping 131 ・ ・ ・ ・ ・ Open / close valve 132 ... Open / close valve 133 ... Oxygen analyzer 151 ... Atmosphere 152: Oxygen-rich gas 153 ... Nitrogen gas 154 ・ ・ ・ ・ ・ High-purity nitrogen gas

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Claims (10)

[Claims] 1. A method for producing nitrogen gas, which comprises bringing compressed air into contact with iron powder to form iron oxide, thereby reducing oxygen in the compressed air to leave nitrogen gas. 2. The method for producing nitrogen gas according to claim 1, wherein a catalyst is added to the iron powder. 3. The method for producing nitrogen gas according to claim 2, wherein the catalyst is sodium chloride. 4. The method for producing nitrogen gas according to claim 1, wherein water is added to the iron powder. 5. The purity of the nitrogen gas is further increased by first passing the compressed air through a hollow fiber membrane and bringing the remaining nitrogen gas into contact with the iron powder. The method for producing nitrogen gas according to claim 1. 6. A hollow fiber membrane (40) for leaving nitrogen gas by feeding compressed air, and a deoxidizing chamber formed with iron powder for making the nitrogen gas highly pure by feeding the remaining nitrogen gas ( 50) An apparatus for producing nitrogen gas, comprising: 7. The apparatus for producing nitrogen gas according to claim 6, wherein water is also formed in the deoxidation chamber (50). 8. The nitrogen gas producing apparatus according to claim 6, wherein a catalyst is also formed in the deoxidizing chamber (50). 9. The nitrogen gas producing apparatus according to claim 8, wherein the hollow fiber membrane (40) is made of polyimide, and the catalyst is sodium chloride. 10. A branch portion (122) is provided between the hollow fiber membrane (40) and the deoxidizing chamber (50) to produce two kinds of nitrogen gas (153, 154) having purity. The nitrogen gas production apparatus according to any one of claims 6 to 9.