JPH04208385A - Super purity nitrogen manufacture device - Google Patents

Abstract

PURPOSE:To supply product nitrogen having super purity in a constant and stable manner by using a cold storage tank without the application of an expansion turbine, supplying the cold stored in the cold storage tank to a partial condenser for the whole device, and storing a part of the manufactured super purity liquid nitrogen in a backup tank. CONSTITUTION:A first rectification device system alone is operated. A raw air is introduced into the bottom of a first rectification tower 8 where the raw air is partially liquefied and collected in the bottom of the first rectification tower 8. The liquid nitrogen is fed to a partial condenser 10 and used for cooling a condenser 11 in the partial condenser 10. Cold solution, such as the liquid nitrogen is simultaneously supplied into the partial condenser 10, thereby carrying out cooling action for the condenser 11. The nitrogen gas collected in the upper part of the first rectification tower 8 by its rectification action is introduced into the condenser 11, and subjected to the cooling action of the cold solution and liquefied. The liquefied component is returned into the first rectification tower 8 as a reflux solution. When the first rectification device system fails to meet the demand for the product nitrogen, a valve is opened so that super purity liquid nitrogen may flow from a back up tank 31 into a vaporizer 32 where it is gasified by means of a vaporizer 32 and supplied to a product nitrogen gas take out pipeline 26.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ultra-high purity nitrogen production apparatus.

[Conventional technology]

Conventional equipment for producing high-purity nitrogen, such as high-purity nitrogen gas, compresses raw air with a compressor, cools it through a heat exchanger, and sends it into a rectification column, where the raw air is cryogenically liquefied and separated. The nitrogen gas is then purified using a purifier. This type of nitrogen gas production equipment uses an expansion turbine whose driving source is oxygen-rich exhaust gas produced as a by-product in a rectification column, and uses the cold generated there to cool compressed air as a raw material. Since the expansion terchin is a high-speed rotating device (tens of thousands of times per minute), it is difficult to quickly adjust the rotation speed. Have difficulty. Therefore, in response to a significant increase in demand for product nitrogen gas, there is a delay in increasing the amount of refrigeration, resulting in a major problem in that impure nitrogen gas is produced during this time. Further, as mentioned above, since the expansion turbine rotates at high speed, it requires high precision in its mechanical structure and is expensive, and also has the disadvantage that specially trained personnel are required. That is, since the expansion turbine is a high-speed device, it causes the above-mentioned problems, and there has been a strong desire to eliminate the expansion turbine.

For this reason, the non-inventors have developed a device that removes the expansion turbine and instead supplies liquid nitrogen as cold to a rectification column, and separates the air by cryogenic liquefaction to produce nitrogen gas. The application was filed (Japanese Patent Application No. 146332/1982) and the patent application was published (Japanese Patent Publication No. 46747/1982). This device (hereinafter referred to as the "proposed device") is installed directly on the premises of a semiconductor manufacturing factory, etc., is manufactured at a liquid nitrogen manufacturing factory (equipped with a large cryogenic separation device), and is transported by tank truck. The resulting product is stored in a storage tank and used for cooling.This equipment produces 10 parts of high-purity product nitrogen gas per 1 part of chilled liquid nitrogen transported by lorry. In addition, because the resulting product is of high purity, there is no need for a conventional purifier.Furthermore, the follow-up operation for load fluctuations can be quickly achieved by controlling the amount of liquid nitrogen supplied. Because it can handle this, it does not cause a drop in product purity when the load fluctuates.

[Problems to be Solved by the Invention] However, in the electronics industry, semiconductor manufacturing technology has progressed dramatically, and extremely high purity nitrogen gas is required as the nitrogen gas used therein. For example, in the proposed device, the impurity 0□ is 0. O can be suppressed to about 5 ppm, and impurities such as CO□ and CH can also be suppressed to about 0.01 ppm. However, Hz and He cannot be suppressed, and they remain at about 0.2 ppm. However, the presence of such Hz and He, especially Hz, has a great negative influence on semiconductor manufacturing in these days when semiconductor manufacturing technology has advanced dramatically. In addition, in the current state of highly automated systems, there is a growing demand for a continuous and stable supply of ultra-high purity nitrogen gas. That is,
If ultra-high purity nitrogen gas is not stably supplied, many defective products due to impurities will occur in the semiconductor manufacturing process.

This invention was made in view of these circumstances, and
□ and Co2. The purpose is to provide an ultra-high purity nitrogen production device that can constantly and stably supply ultra-high purity nitrogen with extremely low impurities such as not only C and H3 but also Hz and He.

1. Means for Solving the Problem] In order to achieve the above object, the ultra-high purity nitrogen production apparatus of the present invention includes a rectification column for cryogenic liquefaction separation.

First and second rectification devices equipped with a demultiplexer with a built-in condenser are provided at the top of the rectification column, and a storage tank receives and stores a cold liquid from outside the device. are provided in the first and second supply pipes for replacing the cold liquid in the storage tank with the cold heat generated by the cold heat generating expander and supplying them to the demultiplexers of the two precision devices; and a third control valve that vaporizes low-boiling impurity components and separates and removes them from liquid nitrogen due to the difference in boiling points.
a rectification column; an introduction pipe for introducing liquid nitrogen in the rectification column of the first precision device into the third rectification column;
A product extraction pipe that takes out as a product most of the liquid nitrogen from which low-boiling impurity components have been removed in the rectification column, a backup tank that stores the remainder of the liquid nitrogen from which the low-boiling impurity components have been removed, and a product from this backup tank. A backup pipe with a smoke generator extending to the nitrogen gas extraction valve 1',
Normally, the first rectifier is provided with a control means for controlling both of the control valves so as to supply cold liquid to the second rectifier in the event of an abnormality. In addition, in this invention, the cryogenic liquid refers to liquid nitrogen or liquid air.

[Effect]

The device of this invention normally operates as follows. That is, 1st. Of the second rectifier, only the first rectifier system (including the third rectifier) is operated, and the bottom of the rectifier (hereinafter referred to as "first rectifier") is Feedstock air is introduced, and a portion of it is liquefied and stored at the bottom of the first rectification column.

This liquid air is sent to the demultiplexer and used for cooling the condenser within the demultiplexer. A cold liquid such as liquid nitrogen produced in another cryogenic separation device, transported by a tank truck, etc., and stored in the tank of the device is simultaneously supplied into the dephlegmator to cool the condenser. Nitrogen gas accumulated in the upper part of the first rectification column by the rectification action of the first rectification tower is introduced into the condenser, and is liquefied by the cooling action of the cold liquid. The liquefied component is then returned to the first rectification column as a reflux liquid. This returned liquid nitrogen (including the liquid nitrogen produced in the rectification column) is either made into a high-purity product or is sent to the third rectification column, where hydrogen, helium, etc., which have a lower boiling point than nitrogen, is vaporized and removed as an ultra-high purity product. According to the rod device, it was difficult to remove He, which has a boiling point lower than that of nitrogen, but in the device of the present invention, since this is removed in the third rectification column, extremely high purity, e.g. 0□ is 0.001 p pm, C
o is 0.01 ppm, COx is 0.00 I P pm
, Hz is 0.0005 p p m, H2 is 0
．． It is possible to produce ultra-high purity nitrogen of OO5ppm or less. In this case, in the first rectifier system, if there is a failure in the feed air supply system, a power outage, or the first rectifier system cannot keep up with the demand for product nitrogen, the valve is opened to supply air from the backup tank to the evaporator. Ultra-high purity liquid nitrogen is flowed and vaporized in an evaporator, which is then supplied to the product nitrogen gas extraction pipe. If you want to do something like the above↓
This can be fully addressed. Next, in the first rectifier system of the old record, when a periodic inspection or an abnormality occurs, such as a clogged pipe in the rectifier, which cannot be repaired in a short time, the first rectifier The system is shut down and the second rectifier system is turned on. That is, the cold liquid nitrogen (which always contains impurities) stored in the storage tank is transferred to the rectification column of the second rectification device (hereinafter referred to as the "second rectification column").
In this second rectification column, impurities are separated by cryogenic cooling, and the nitrogen is made into an ultra-high purity product. This prevents interruption of the supply of ultra-high purity product nitrogen.

Next, examples will be described.

〔Example〕

FIG. 1 shows an embodiment of the invention. In the figure, 1 is an air compressor, 2 is a drain separator, 3 is a freon cooler, and 4 is a set of two adsorption towers.

Inside the adsorption tower 4 ↓ This is filled with molecular sieve, and the H in the air compressed by the air compressor 11i1 is
2O and CO□ are adsorbed and removed. 5 is H2O, CO2
This is the compressed air supply pipe that sends the compressed air that has been adsorbed and removed. 6 is a main heat exchanger, into which compressed air from which H, 0 and CO□ have been adsorbed and removed by the adsorption tower 4 is sent. 7
is a compressed air delivery pipe, through which compressed air cooled to an ultra-low temperature by the main heat exchanger 6 is sent. A is the first rectifier,
8 is the rectification column (first rectification column), and the main heat exchanger 6
Compressed air cooled to ultra-low temperatures is sent to the bottom. A portion of the compressed air is liquefied in the first rectification column 8 and stored at the bottom as liquid air 9, and nitrogen is stored at the top in a gaseous state. The nitrogen gas stored in the upper part is rectified into a high-purity product as it passes through a large number of rectification shelves (not shown) in the first rectification column 8 and ascends. Reference numeral 10 denotes a dephlegmator provided at the top of the first rectification column 8, and a first reflux liquid pipe 12 extends from the top of the first rectification column 8 to the top of the internal condenser 11. There is. The nitrogen gas at the upper part of the rectification column 8 is introduced into the condenser 11 through this first reflux liquid vibe 12 and is liquefied. Reference numeral 13 denotes a second reflux liquid pipe, which introduces the liquid nitrogen produced by liquefaction in the condenser 11 as a reflux liquid into the reflux liquid reservoir 14 at the upper part of the first rectification column 8. 13a is in the nitrogen gas introduced into the condenser 11,
H.

, He is a first discharge pipe that discharges impurity components with a lower boiling point than nitrogen, such as He, in a gaseous state, and extends from the upper part of the condenser 11 to the outside through the main heat exchanger 6, and discharges He, Hz, and He to the outside. . 15 is a liquid air pipe which introduces the liquid air 9 at the bottom of the rectification column into the dephlegmator 10 to cool the condenser 7 and condenser 11;
1 has the effect of liquefying the nitrogen gas passing through it. 16 is a liquid nitrogen storage tank (hereinafter abbreviated as "storage tank") that stores liquid nitrogen that becomes cold, and stores liquid nitrogen produced in another cryogenic separation device and transported by a tank truck or the like. For convenience of illustration, the storage tank 16 is depicted at the top of the drawing, or the storage tank 16 is installed on the ground. I
A supply pipe 7 extends from the storage tank 16 to the demultiplexer 10, and cools the condenser 11 with the cold heat of liquid nitrogen. 27 is its control valve. In the dephlegmator 10, this liquid nitrogen and liquid air supplied from the bottom of the rectification column 8 exist in a mixed state. 18 is a discharge pipe extending from the upper part of the dephlegmator 10 through the main heat exchanger 6;
A mixed gas of liquid air and liquid nitrogen, which exerts a cooling effect inside and is itself vaporized, is discharged to the outside as exhaust gas via the main heat exchanger 6. 18a is a waste liquid pipe which extends to the outside through the evaporator 18b and connects to the dephlegmator lO.
The mixed liquid that accumulates at the bottom of the tank (in which CH4, etc. are condensed and mixed due to repeated condensation) is gasified and released. A branch pipe 5a branched from the compressed air supply pipe 5 extends to the evaporator 18b, and a part of the compressed air is cooled by heat exchange with the evaporator 18b. 19゛ is the third rectification column. 20 is an introduction pipe extending from the liquid nitrogen reservoir 20a at the upper part of the first rectification column 8 to the third rectification column 19. The liquid nitrogen produced by the rectification action of the column 8 is led into the third rectification column 19. Third rectification column 1
9 contains impurity components such as Hz and He, which have a boiling point lower than that of nitrogen, from the liquid nitrogen sent in through the introduction pipe 20.
Remove by distillation. 21 is a second discharge pipe extending from the upper part of the third rectification column 19, which sends vaporized low-boiling point impurity components such as 21b is a return pipe that returns the liquefied nitrogen to the third rectification column 19.21g
is a pipe extending from the upper part of the condenser 21a through the main heat exchanger 6, through which the low-boiling impurity components are brought to room temperature by heat exchange and discharged to the outside. 21c is a 20th fractionator that incorporates the condenser 21a, and a pipe 21e extending from the center of the first fractionator 8 connects the central portion of the first fractionator 8 to the fractionator 21c. A reservoir of liquid nitrogen (impurities have not been sufficiently removed) is supplied. This liquid nitrogen is used for cooling the condenser 21a. Reference numeral 21f denotes a waste nitrogen pipe which discharges waste liquid nitrogen, which has been heat exchanged and vaporized in the condenser 21a, to the outside via the main heat exchanger 6. In the third rectifying column 19, ultra-highly purified liquid nitrogen from which low-boiling point impurity components such as Hz and He have been removed is stored at the bottom. A product liquid nitrogen extraction pipe 24 for taking out ultra-high purity product liquid nitrogen extends from the bottom of the third rectification column 19, and the ultra-high purity liquid nitrogen is provided for demand through this pipe 24. 25 is a branch pipe branched from the pipe 24, which passes from the bottom to the top of the condenser II and extends to the third rectification column 19, which cools the condenser 1 with the cold heat of the product liquid nitrogen, and It functions to return the liquid nitrogen vaporized during the process to the upper part of the product liquid nitrogen storage tank 23. 26 is a product nitrogen gas take-off pipe, and the third rectification column 19
It extends from the middle stage using the main heat exchanger 6, and at the bottom of the third rectification column 19, the nitrogen gas produced by vaporizing the stored liquid nitrogen and the nitrogen gas produced in the condenser 11 are heated to a temperature exceeding room temperature. It will be provided to demand as high-purity nitrogen gas. 30 is a pressurized tank, 31 is a backup tank, and 32 is an evaporator. 33 is a backup pipe that branches from the liquid nitrogen extraction pipe 24 and extends to the pressurized tank 30, which supplies ultra-high purity liquid nitrogen to the pressurized tank 30. 34 is a backup pipe extending from the pressurized tank 30 to the backup tank 31, and the evaporator 30 provided in the pressurized tank 30
High purity liquid nitrogen pressurized by the action of a is sent to the backup tank 31. 35 is a backup pipe extending from the backup tank 31 to the product nitrogen gas extraction pipe 26, in which the ultra-high purity liquid nitrogen drawn out from the backup tank 31 is vaporized in the evaporator 32, and the product is produced as ultra-high purity product nitrogen gas at approximately room temperature. The nitrogen gas is supplied to the nitrogen gas extraction pipe 26. These backup pipes 33, 34.
35, a pressurized tank 30, a backup tank 31, and an evaporator 32 form a backup line. 36 is an on-off valve provided in the backup pipe 33, and 38 is a pressure control valve. A' is a second rectification apparatus, which has substantially the same structure as the first rectification apparatus A, so that the part corresponding to the first rectification apparatus A is provided with the first rectification apparatus [ The same reference numerals as A are given. A pipe 41 extends from the storage tank 16 to approximately the center of the second rectification column 8' of the second rectification apparatus A', and supplies liquid nitrogen to the second rectification column 8'.
Liquid nitrogen is supplied in a gas-liquid mixed state to the upper side of the bottom of the second rectification column 8' through a pipe 42 with an evaporator 42a extending from the bottom of the second rectification column 8'.

To describe the second rectification column A' in more detail, the second rectification column 8' is equipped with liquid supplied from the storage tank 16 instead of the raw air supplied to the first rectification column 8. Nitrogen is used and introduced into the bottom in a gas-liquid state. This liquid nitrogen is subjected to the rectifying action of the second rectifying column 8' and accumulates in the upper liquid nitrogen reservoir as ultra-high-purity liquid nitrogen, and then passes through the pipe 20' and the evaporator 44 to an ultra-high-purity liquid nitrogen at approximately room temperature. The product becomes high-purity nitrogen gas and is sent to the product nitrogen gas extraction pipe 26. In addition, 45 and 46 are pipes 13a' and 1, respectively.
8', the waste gas and H
A low boiling point impurity component gas such as e is heated to around room temperature.

In the figure, LIC is a liquid level gauge combined with a valve, which controls the opening or opening/closing of the valve depending on the liquid level at the installation location, thereby constantly controlling the liquid level at the installation location. Moreover, the dashed line indicates a vacuum cooling box, and the inside of the box is kept vacuum cold.

In this configuration, raw air is normally supplied to the air compressor 1.
water is removed by a drain cooler 2, further cooled by a fluorocarbon cooler 3, and sent in that state to an adsorption tower 4, where H2O and CO□ are adsorbed and removed. Then, it is sent to the main heat exchanger 6 and cooled to an ultra-low temperature, and is introduced into the bottom of the first rectification column 8 in a gas-liquid mixed state. The raw air is further cooled and liquefied at the bottom of the first rectification column 8, and a portion of the feed air is collected at the bottom of the first rectification column 8 as liquid air. The remainder goes to the first rectification column 8.
In the process, it is rectified, and high-boiling components such as oxygen are liquefied and separated due to the difference in boiling points. As a result, liquid nitrogen containing oxygen as an impurity accumulates approximately in the center of the first rectification column 8 (a portion of which is introduced into the waste liquid nitrogen tank 21c as waste liquid nitrogen through the pipe 21e), and High purity nitrogen gas accumulates. The liquid air accumulated at the bottom of the first rectification column 8 is introduced into the dephlegmator 10 via the pipe 15 and cools the condenser 11 there.

Nitrogen gas accumulated in the upper part of the first rectification column 8 is introduced into this condenser 11, is cooled by the cold heat of the liquid air, liquefies, and flows down to the upper part of the first rectification column 8 as a reflux liquid. do. Furthermore, liquid nitrogen is supplied to the demultiplexer 11 from a storage tank 16, and cools the condenser 11 together with the liquid air. Liquid air and liquid nitrogen vaporized by cooling the condenser 11 are taken out from the upper part of the decentralizer as waste gas through a pipe 18, cooled by the main heat exchanger 6, and then discharged to the outside. On the other hand, the liquid nitrogen that has flowed down as the reflux liquid into the upper part of the first rectification column 8 (this includes not only the reflux liquid but also the liquid nitrogen generated by the rectification action of the first rectification column 8 itself). ) is sent through pipe 20 to a third rectification column I9, where low-boiling impurities (He, H2) are removed by distillation. This results in
The liquid nitrogen is ultra-purified and collected at the bottom of the third rectification column 19. A part of the stored ultra-high purity liquid nitrogen is provided for demand through the pipe 24, and the remainder is sent to the condenser 11 through the branch pipe 25, where it is vaporized and becomes the ultra-high purity product nitrogen gas. Return to the third rectification column I9. This ultra-high purity product nitrogen gas is taken out from pipe 2.
6 to the main heat exchanger 6, where it exchanges heat with raw material air and becomes room temperature and is used for demand. In addition, the low-boiling point impurity component gas such as He that has been vaporized and removed in the third rectification column 19 is sent to the condenser 21a, where the waste liquid nitrogen introduced from the center of the first rectification column 8 is collected. After the nitrogen gas is liquefied and removed by the cooling agent, it is discharged to the outside through the main heat exchanger 6.

In addition, during periodic inspections of the first rectifier A system or when the amount of product nitrogen cannot keep up with demand, the action of the valve 38 allows the ultra-high purity liquid nitrogen in the backup tank 31 to be transferred to the evaporator 32.
The product is vaporized and supplied to 26 product nitrogen extraction pipes as ultra-high purity product nitrogen gas.

In addition, in the event of an abnormality such as when a pipe is clogged inside the first rectification column 8 or the like leading to the first rectification device and it takes a long time to repair, the air compressor l is stopped and the valve 27 is closed. Stop the first rectifier A system. Then, from the storage tank 16, the second rectifier A' is connected via the pipe 41.
Supply liquid nitrogen (containing trace amounts of impurities) to the

A part of this liquid nitrogen is sent to the center of the rectification column 8' and becomes a reflux liquid, and the remainder passes through the evaporator 42a and becomes a gas-liquid mixture and is sent to the bottom of the second rectification column 8' as a raw material. Supplied. In this second rectification column 8', the raw material liquid nitrogen supplied as described above undergoes a rectification action, becomes ultra-high purity liquid nitrogen, and accumulates in the upper part. This is pipe 2
It is taken out from 0, vaporized in the evaporator 44, becomes ultra-high purity product nitrogen gas at approximately room temperature, and is supplied to the take-out pipe 26 for demand.

In this way, an ultra-high purity product is supplied not only when the first rectification apparatus A is normal but also when it is abnormal. Therefore, the supply of ultra-high purity product nitrogen is never interrupted.

FIG. 2 shows another embodiment. In this embodiment, the liquid nitrogen supply pipe 30 also extends from the storage tank 16 to the center of the first rectification column 8. The other parts are the same as those in FIG. By doing this, in addition to obtaining the same effects as mentioned above, the amount of cold supplied to the entire device is increased, so it is possible to significantly shorten the time required to stop and restart the device. effect will be obtained.

In the above explanation, ultra-high purity liquid nitrogen is taken out from the second rectification column 8', but the ultra-high purity nitrogen gas accumulated at the top of the rectification column 8' is directly used as product nitrogen gas. You can also take it out.

In addition, liquid nitrogen is stored in the storage tank 16,
Instead, liquid air is stored and used for each precision device A,
It may also be supplied to A'.

Further, the portion X surrounded by the dashed line in FIG. 1 may be changed as shown in FIG. 3.

〔Effect of the invention〕

As described above, the ultra-high purity nitrogen gas production apparatus of the present invention does not use an expansion turbine, but instead uses a cold storage tank, and supplies the cold water from the cold storage tank to the demultiplexer instead of the rectifier. The entire device is kept cold. Therefore, since the above-mentioned cold does not mix into the product nitrogen,
Even if impurities are mixed into the cold temperature, the purity of the product nitrogen will not decrease due to the mixed impurities. Moreover,
Because it does not use an expansion tachin, which is a high-speed rotating device,
In addition to eliminating the need for personnel to operate the expansion turbine, it also enables detailed follow-up operation to load fluctuations (changes in the amount of product nitrogen taken out), making it possible to constantly and stably supply high-purity products. Moreover, the apparatus of the present invention is equipped with a third rectification column, into which the liquid nitrogen obtained in the first rectification apparatus is introduced, and in order to remove He etc. having a lower boiling point than nitrogen,
The proposed device can also remove He, etc., which cannot be separated, and it becomes possible to produce product nitrogen with ultra-high purity, which cannot be obtained with the proposed device. In particular, in the apparatus of the present invention, a part of the ultra-high purity liquid nitrogen produced as described above is stored in a backup tank, and is used during periodic inspections of the first rectifier system and when the demand for product nitrogen gas is checked. When there is a significant increase in demand, this can be vaporized and made into ultra-high purity product nitrogen gas to meet demand. Furthermore, the apparatus of the present invention is provided with a second rectification apparatus together with the first rectification apparatus, and when an abnormality occurs in the first rectification apparatus, the cold liquid is supplied from the cold storage tank to the second rectification apparatus, It is possible to produce ultra-high purity product nitrogen. Therefore, ultra-high purity product nitrogen can be stably supplied at all times.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of one embodiment of the present invention, Fig. 2 is a block diagram of another embodiment, and the third is an explanatory diagram of a modification of the portion surrounded by the dashed line X in Fig. 1. .

Claims (2)

[Claims] (1) A rectification column for cryogenic liquefaction separation, and a first and second rectification device equipped with a dephlegmator with a built-in condenser installed in the upper part of the rectification column, and the device A storage tank is provided for receiving and storing a cold liquid supplied from the outside, and first and second first and second rectifiers are provided for supplying the cold liquid in the storage tank to the cold heat generated by the cold heat generating expander and supplying the cold liquid to the two rectifiers. a supply pipe, a control valve provided on each of the above-mentioned pipes, a third rectification column that vaporizes low-boiling impurity components and separates and removes them from liquid nitrogen due to the difference in boiling points, and the first rectification device. An introduction pipe for introducing the liquid nitrogen in the rectification column into the third rectification column, and a product extraction pipe for taking out as a product most of the liquid nitrogen from which low-boiling impurity components have been removed in the third rectification column. A pipe, a backup tank for extracting and storing the remainder of the liquid nitrogen from which the low boiling point impurity components have been removed, a backup pipe with an evaporator extending from the backup tank to the product nitrogen gas extraction pipe, and a first rectification device that is normally used. An apparatus for producing ultra-high purity nitrogen, characterized in that a control means is provided for controlling both of the control valves so as to supply cold liquid to the second rectification apparatus in the event of an abnormality. (2) In the third rectification column, a branch pipe extends from the product take-out pipe for taking out the liquid nitrogen as a product to the condenser of the demultiplexer, and by passing through the condenser, the product liquid nitrogen is transferred to the condenser. The ultra-high purity nitrogen production apparatus according to claim 1, wherein the nitrogen gas is vaporized by heat exchange with a circulating component in the nitrogen gas.