JPS6131872A - Production unit for high-purity nitrogen gas - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a high purity nitrogen gas production apparatus.

[Background technology]

Extremely large amounts of nitrogen gas are used in the electronics industry, but strict requirements have been placed on the purity of nitrogen gas from the perspective of maintaining and improving component precision. In other words, nitrogen gas is
Generally, air is used as a raw material, and after compressing it with a compressor, it is put into an adsorption column to remove carbon dioxide and moisture, and then cooled by exchanging heat with a refrigerant through a heat exchanger, and then deeply cooled in a rectification column. It is manufactured through a process of liquefying and separating product nitrogen gas, and raising the temperature of this gas to near room temperature through the aforementioned heat exchanger. However, since the product nitrogen gas produced in this way contains oxygen as an impurity, it is often inconvenient to use it as it is. Methods for removing impure oxygen include: ■ Using a PT catalyst, adding a small amount of hydrogen to nitrogen gas and reacting with impure oxygen in an atmosphere at a temperature of about 200°C to remove it as water; and ■ Using a Ni catalyst. There is a method of removing impure oxygen in nitrogen gas by bringing it into contact with a Ni catalyst in an atmosphere at a temperature of about 200° C. to cause a reaction of Nt+1/20□→NiO. However, in all of these methods, the nitrogen gas must be heated to a high temperature and brought into contact with the catalyst, so the apparatus cannot be incorporated into a nitrogen gas production apparatus that is an ultra-low temperature system. Therefore, it is necessary to install a purification device separately from the nitrogen gas production device, which has the drawback of increasing the overall size. Furthermore, the method (■) requires high precision in adjusting the amount of hydrogen added, and if the amount of hydrogen that is not added is just enough to react with the amount of impure oxygen, oxygen may remain or the added hydrogen may remain. The problem is that it requires skill to operate, as it becomes an impurity. In the method (①) above, Ni produced by the reaction with impure oxygen
There is a problem in that it becomes necessary to regenerate O (NiO+Hg→N i + H20), and H2 gas equipment for regeneration is required, leading to an increase in refining costs. Therefore, these improvements have been strongly desired.

In addition, conventional nitrogen gas production equipment uses an expansion turbine to cool the refrigerant in the heat exchanger that exchanges heat with the compressed air compressed by the compressor. Through cryogenic liquefaction separation, low-boiling point nitrogen is extracted as a gas, and the remainder accumulates as oxygen-rich liquid air.It is driven by the pressure of the evaporated gas. However, expansion turbines have extremely high rotational speeds (tens of thousands of rotations per minute), making it difficult to follow load fluctuations.
Specially trained operators are required. Furthermore, since this type of rotor rotates at a high speed, it requires high precision in its mechanical structure, is expensive, and has the disadvantage of requiring specially trained maintenance personnel due to its complicated mechanism. That is, since the expansion turbine has a high-speed rotating section, it causes the various problems described above, and there has been a strong desire to eliminate the expansion turbine having such a high-speed rotating section.

In order to meet these demands, the inventor has developed a nitrogen gas production device that removes the expansion turbine and instead supplies liquid nitrogen from the outside as cold into the rectification column.
A patent application (Japanese Patent Application No. 58-38050) has already been filed.

Since this device can produce nitrogen gas of extremely high purity, conventional purification equipment is completely unnecessary. Also,
Since the expansion turbine is removed, there are no adverse effects caused by it. However, in this device, the liquid nitrogen storage tank for storing liquid nitrogen is provided separately from the rectification column, so the installation space of the entire device is large. Furthermore, since the liquid nitrogen transport pipe (vacuum insulated pipe) extending from the liquid nitrogen storage tank to the rectification tower passes through the atmosphere, it also has the disadvantage that the evaporation loss of liquid nitrogen is large.

[Purpose of the invention]

The purpose of this invention is to provide an apparatus that can produce high-purity nitrogen gas without using an expansion turbine or purification equipment, requires less installation space, and reduces evaporation loss of liquid nitrogen. be.

[Disclosure of the invention]

In order to achieve the above object, the present invention includes an air compression means for compressing air taken in from the outside, a removal means for removing carbon dioxide and water from the compressed air compressed by the air compression means, and a removal means for removing carbon dioxide and water from the compressed air compressed by the air compression means. A heat exchange means that cools the compressed air that has passed through the removal means to an ultra-low temperature; a rectification column that liquefies a part of the compressed air that has been cooled to an ultra-low temperature by the heat exchange means and stores it therein, retaining only nitrogen as a gas; a liquid nitrogen storage means for storing liquid nitrogen; an introduction path for guiding the liquid nitrogen in the liquid nitrogen storage means to the elliptical distillation column as a cold source for liquefying compressed air; and a vaporizer held in the rectification column. A nitrogen gas extraction passage for extracting nitrogen is provided, and at least the rectification column and the liquid nitrogen storage means are arranged in the same vacuum insulation container, and the rectification column and the liquid nitrogen storage means are provided integrally. It has this structure.

Next, the present invention will be explained in detail based on examples.

FIG. 1 shows an embodiment of the present invention, and FIG. 2 shows the concept of its main parts. In these figures, 9 is an air compressor, 1O is a drain separator, 11 is a freon cooler, 12
is a set of two adsorption cylinders. The adsorption column 12 is filled with molecular sieve and functions to adsorb and remove H2C and CO2 in the compressed air compressed by the air compressor 9. 8 is a compressed air supply pipe that sends compressed air in which H2C and Co2 have been adsorbed and removed. 13 is a first heat exchanger, into which compressed air from which H2C and CO2 have been adsorbed and removed by the adsorption column 12 is sent. 14 is a second heat exchanger, into which the compressed air that has passed through the first heat exchanger 13 is sent. Reference numeral 15 denotes a rectification column whose top part is a dephlegmator part 21 having a condenser 21a, and the part below it is a column part 22, and the first and second heat exchangers 13,
The compressed air cooled to an ultra-low temperature by 14 and sent through the pipe 17 is further cooled, a part of which is liquefied and stored at the bottom of the tower section 22 as liquid air 18, and only nitrogen in a gaseous state is sent to the upper ceiling of the tower section 22. It is designed to be stored in 22a. 23 is a substantially cylindrical liquid nitrogen storage tank fitted around the outer periphery of the rectification column section 22, and the liquid nitrogen (high purity product) 23a inside is rectified through the introduction pipe 24a. The compressed air is fed into the upper side of the tower section 22 of the tower 15 and serves as a cold source for the compressed air supplied into the tower section 22. Here, the rectification column 1
5 in more detail, the rectification column 15 consists of a dephlegmator part 21 and a column part 22, and a condenser 21a in the dephlegmator part 21 contains part of the nitrogen gas accumulated in the upper part of the column part 22. part is fed through pipe 21b. This pipe 21b
is branched from a take-out pipe 27 that takes out the nitrogen gas accumulated in the upper part of the tower section 22 as a product nitrogen gas. The inside of the dephlegmator section 21 is in a lower pressure state than the inside of the column section 22, and the liquid air (N,: 50~
70%, 0□; 30-50%) 18 is fed through a pipe 19 with an expansion valve 19a, and is vaporized to cool the internal temperature to a temperature below the boiling point of liquid nitrogen. Due to this cooling, the nitrogen gas fed into the condenser 21a is liquefied. In the upper part of the column section 22 of the rectification column 15,
Liquid nitrogen generated in the condenser 21a of the demultiplexer section 21 is supplied downstream through the pipe 21c, and liquid nitrogen 23a is supplied from the liquid nitrogen storage tank 23 through the pipe 24a, which flows into the liquid nitrogen reservoir 21d. The air then flows downward in the tower section 22, contacts the compressed air rising from the bottom of the tower section 22 in a countercurrent manner, cools it, and partially liquefies it.

In this process, high boiling point components in the compressed air are liquefied and
Nitrogen gas, which is a low boiling point component, accumulates at the top of the tower section 22. Reference numeral 27 denotes a take-out pipe for taking out the nitrogen gas accumulated in the upper ceiling part 22a of the rectification column section 22 as a product nitrogen gas as described above, and the extremely low temperature nitrogen gas is passed through the second and first pipes.
The air is guided into the heat exchangers 14 and 13, where it exchanges heat with the compressed air sent there to bring it to room temperature and send it into the main pipe 28. In this case, He (
, -26'9°C) and H2 (253°C) tend to accumulate, so the take-out pipe 27 opens well below the top of the tower section 22, allowing only pure nitrogen gas without He and H2 to be collected. It is designed to be extracted as product nitrogen gas. 2
9 is a pipe that sends the vaporized liquid air in the dephlegmator section 21 to the second and first heat exchangers 14.13 for heat exchange and then releases it into the atmosphere, and 29a is its pressure holding valve. . A dashed-dotted line A indicates a vacuum cooling section with pearlite vacuum insulation, and indicates the rectification column 15 and the first. A second heat exchanger 13,14 as well as a liquid nitrogen storage tank 23 are accommodated. In addition, 30 is a liquid nitrogen supply pipe of the liquid nitrogen storage tank 23, 32 is an impurity analyzer, and the main pipe 2
The purity of the product nitrogen gas sent out in step 8 is analyzed, and if the purity is low (), the valves 34, 34a are operated to release the product nitrogen gas to the outside as shown by arrow B.

Further, in FIG. 2, numeral 31 indicates a special vacuum insulation layer. That is, as shown in FIG. 3, this vacuum insulation N31 is made of a heat insulating material 41 that is made by polymerizing Dexitar paper (paper material containing glass powder) and aluminum foil around the outer periphery of the rectification column 15.
The liquid nitrogen storage tank 23 is wound with a plurality of turns, and the space between its outer peripheral surface and the inner surface of the liquid nitrogen storage tank 23 is evacuated.

This device produces product nitrogen gas in the following manner. That is, air is compressed by the air compressor 9, water in the compressed air is removed by the drain separator 10, and cooled by the fluorocarbon cooler 11. In this state, the air is sent to the adsorption column 12 to remove H2O and CO□ is adsorbed and removed. Next, the compressed air from which H2O and CO2 have been adsorbed and removed is sent to the first and second heat exchangers 13 and 14 to be cooled to an ultra-low temperature, and in that state is introduced into the lower part of the rectification column section 22. Next, this input compressed air is cooled by contacting with the liquid nitrogen 23a sent into the rectification column section 22 from the liquid nitrogen storage tank 23 and the overflowing liquid nitrogen from the liquid nitrogen reservoir 21d, and a part of it is liquefied. The liquid air 18 is stored at the bottom of the tower section 22 as liquid air 18. In this process, the difference between the boiling points of nitrogen and oxygen (boiling point of oxygen - 183°C boiling point of 2M element - 196°
Due to C), oxygen, which is a high boiling point component in compressed air, is liquefied, and nitrogen remains as a gas. Next, the remaining gaseous nitrogen is taken out from the extraction pipe 27 and sent to the second and first heat exchangers 14.13, where it is heated to near room temperature and sent out from the main pipe 28 as a product nitrogen gas. In this case, from the liquid nitrogen storage tank 23 to the inlet pipe 24a
The liquid nitrogen fed into the rectification column section 22 acts as a cold source for liquefying compressed air, and is vaporized and taken out from the take-out pipe 27 as part of the product nitrogen gas.

In this way, this device has a substantially cylindrical liquid nitrogen storage tank 23 fitted around the rectification tower 15, and the rectification tower 15 and the liquid nitrogen storage tank 23 are connected to each other.
Since these are integrally constructed and housed in the same vacuum cooling box (dotted chain line), the installation space can be reduced.

In addition, until now, the liquid nitrogen storage tank was not placed in a vacuum cooling box but was installed separately, and the liquid nitrogen storage tank and the rectification tower were connected through liquid nitrogen transport piping (vacuum insulation piping) in the atmosphere. , the evaporation loss of liquid nitrogen from the transportation piping was large, but this device
and the rectification column 15 are constructed as described above, and the transport piping (introduction pipe 24) is placed in the vacuum cold insulation country in close proximity to the liquid nitrogen storage tank 23.
3, and the evaporation loss of the liquid nitrogen 23a is significantly reduced. Furthermore, since the rectification column 15 is fitted with a liquid nitrogen storage tank 23 and is cooled by the liquid nitrogen 23a, the heat insulation of the rectification column 15 itself is improved, and the rectification efficiency is improved. Furthermore, at the time of starting up the apparatus, the rectification column 15 is pre-cooled with the liquid nitrogen 23a of the liquid nitrogen storage tank 23, so that the start-up time can be shortened.

FIG. 4 shows another embodiment, and FIG. 5 shows the concept of its main part. In this embodiment, a liquid nitrogen storage tank 23 is fitted around a substantially cylindrical column section 22 of the rectification column 15, instead of fitting the rectification column with a substantially cylindrical liquid nitrogen storage tank as in the above embodiment. are doing. Since the other parts are the same as those in the previous embodiment, the explanation will be omitted.

This embodiment also has the same effects as the previous embodiment.

〔Effect of the invention〕

The high-purity nitrogen gas production device of the present invention does not use an expansion turbine, but instead uses liquid nitrogen storage means such as a liquid nitrogen storage tank that does not have any rotating parts, so the entire device has no rotating parts and is free from malfunctions. do not have. Furthermore, liquid nitrogen storage tanks are inexpensive and have a simple structure, so special personnel are not required.

Furthermore, the expansion turbine (which is driven by the pressure of gas evaporated from the liquid air accumulated in the nitrogen rectification column) has an extremely high rotational speed (tens of thousands of rotations/minute), so load fluctuations (the removal of product nitrogen gas) Therefore, it is difficult to precisely follow the changes in the amount of product nitrogen gas taken out, so the rotation speed of the expansion turbine is changed accurately according to changes in the amount of product nitrogen gas taken out, and the compressed air, which is the raw material for nitrogen gas production, is constantly cooled to a constant temperature. However, as a result, the purity of the product nitrogen gas varies, and low-purity products are frequently produced, resulting in the overall purity of the product nitrogen gas being low. By using a liquid nitrogen storage tank as a cooling source, the supply amount of which can be finely adjusted, is used as a cooling source, making it possible to closely follow load fluctuations and producing nitrogen gas with stable and extremely high purity. Therefore, conventional purification equipment is not required.Furthermore, the equipment of the present invention saves installation space because the rectification column and liquid nitrogen storage means are integrated in the same vacuum insulated container. In addition, until now, the liquid nitrogen storage tank was not placed inside a vacuum insulated container but was provided separately, and the liquid nitrogen storage tank and the rectification column were connected by liquid M transport piping (vacuum insulation piping). , the evaporation loss of liquid nitrogen from the transportation piping was large, but since this device had the liquid nitrogen storage tank and rectification tower configured as described above, the transportation piping was placed in a vacuum insulated container and the liquid nitrogen storage means was As a result, the transport piping can be cooled with liquid nitrogen in the liquid nitrogen storage tank, greatly reducing evaporation loss of liquid nitrogen.Furthermore, the rectification column can be cooled with liquid nitrogen in the liquid nitrogen storage tank. Since it is now cooled by liquid nitrogen in the storage means, the heat insulation of the rectification column itself is improved and the rectification efficiency is improved.Also,
At the start-up of the apparatus, the rectification column is pre-cooled with liquid nitrogen in the liquid nitrogen storage means, so that the start-up time can be shortened.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of an embodiment of the present invention, Fig. 2 is a conceptual diagram of its main parts, Fig. 3 is a sectional view taken along line AA' in Fig. 2, and Fig. 4
The figure is a block diagram of another embodiment, and FIG. 5 shows its main parts. Ii
It is a mental idea. 9... Air compressor 11.12... Adsorption cylinder 13゜14... Heat exchanger 15... Impurity rectification column 17...
・Liquid air for pipe 18 21... demultiplexer part 2
1a... Condenser 21d... Liquid nitrogen reservoir 22.
...Tower part 23...Liquid nitrogen storage tank 24a...Introduction path by 128...Main pipe

Claims (3)

[Claims] (1) Air compression means for compressing air taken in from the outside, removal means for removing carbon dioxide and water from the compressed air compressed by this air compression means, and cooling the compressed air that has passed through this removal means to an ultra-low temperature. A heat exchange means for cooling, a rectification column that liquefies a part of the compressed air cooled to an ultra-low temperature by the heat exchange means and stores it inside to retain only nitrogen as a gas, and a liquid nitrogen storage means for storing liquid nitrogen. and an introduction path for guiding the liquid nitrogen in the liquid nitrogen storage means to the rectification column as a cold source for liquefying compressed air, and a nitrogen gas extraction path for taking out the vaporized nitrogen held in the rectification column. , a high-purity nitrogen gas characterized in that at least the rectification column and the liquid nitrogen storage means are arranged in the same vacuum insulation container, and the rectification column and the liquid nitrogen storage means are provided integrally. Manufacturing equipment. (2) The rectification column and the liquid nitrogen storage means are integrally provided by forming the liquid nitrogen storage means into a substantially cylindrical shape and fitting the liquid nitrogen storage means into the rectification column.
High-purity nitrogen gas production equipment as described in . (3) The rectification column and the liquid nitrogen storage means are integrally provided by forming the rectification column into a substantially cylindrical shape and fitting the liquid nitrogen storage means onto the outside of the first claim.
High-purity nitrogen gas production equipment as described in .