JPS61211687A - Production unit for 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] [Industrial application field] This invention relates to a nitrogen gas production device.

[Conventional technology]

The electronic industry uses extremely large amounts of nitrogen gas.

Therefore, it is desired to supply nitrogen gas at low cost, and in order to meet this demand, the PSA method has been introduced, and nitrogen gas has been manufactured and supplied using this method. This PS
Fig. 1 shows a nitrogen gas production apparatus using method A. In the figure, ■ is an air intake port, 2 is an air compressor, 3 is an aftercooler, 3a is a cooling water supply path, and 4 is an oil-water separator. 5 is a first adsorption tank, 6 is a second adsorption tank,
V and V2 are air-operated valves that send air compressed by the air compressor 2 into the adsorption tank 6 by valve action. ■
3 and 4 are vacuum valves, and the interior of the adsorption tank 5.6 is brought into a vacuum state by the action of the vacuum pump 6a. 6b is a cooling pipe that supplies cooling water to the vacuum pump 6a, 6C is a silencer, and 6d is its exhaust pipe. VS, V6. V?
and V, are air operated valves. 7 is a product tank, which is connected to the adsorption tanks 5 and 6 through a pipe 8. 7a is a product nitrogen gas extraction pipe, 7b is an impurity analysis needle, and 7C is a flow meter.

This nitrogen gas production device compresses air with an air compressor 2, and an aftercooler 3 attached to the air compressor 2.
The compressed air is cooled, condensed water is removed by a separator 4, and the air is sent to adsorption tanks 5 and 6 via an air-operated valve (1) or (2). The two adsorption tanks 5 and 6 each contain a carbon molecular sieve for oxygen adsorption, and compressed air is alternately fed into these adsorption tanks 5 and 6 every minute by a pressure swing method. In this case, the adsorption tanks 5 and 6 to which compressed air is not fed are brought into a vacuum state by the action of the vacuum pump 6a.

That is, the air compressed by the air compressor 2 enters one of the adsorption tanks 5, and the oxygen bones therein are adsorbed and removed by the carbon molecular resin, and the air becomes nitrogen gas, which flows into the valves V, V1. (2), and then sent to the product tank 7 and taken out from the pipe 7a. At this time, the air from the air compressor 2 is shut off from the other adsorption tank 6 by closing the valve vt, and the inside of the adsorption tank 6 is vacuumed by the vacuum pump 6a by opening the valve v4. As a result, the oxygen adsorbed on the carbon molecular sieve is removed by suction and the carbon molecular sieve is regenerated. In this way, nitrogen gas is alternately sent from the adsorption tanks 5 and 6 to the product tank 7, and product nitrogen gas is continuously obtained.

[Problem that the invention seeks to solve]

The above-mentioned nitrogen gas production apparatus produces nitrogen gas by utilizing the property of the carbon molecular sheet that selectively adsorbs oxygen, and therefore can obtain nitrogen gas at low cost. However, as mentioned above, compressed air is alternately sent to the two adsorption tanks 5.6 every minute, and at the same time, the inside of the other adsorption tank is vacuumed, which requires a large number of valves. It has the drawback of being complicated to operate and prone to frequent failures. Therefore, a set of two adsorption tanks 5.6
The reality is that we have to set up two sets and keep one set as a reserve. Therefore, it also has the disadvantage of high equipment costs.

On the other hand, conventional cryogenic liquefaction nitrogen gas production equipment uses an expansion turbine to cool the heat exchanger for cooling the compressed raw air compressed by the compressor, and uses the expansion turbine to cool the liquid accumulated in the rectification tower. It is driven by the pressure of gas evaporated from air (low boiling point nitrogen is extracted as a gas through cryogenic liquefaction separation, and the remainder is stored as oxygen-rich liquid air). However, expansion turbines have extremely high rotational speeds (tens of thousands of rotations per minute), making it difficult to follow load fluctuations (fluctuations in the amount of product nitrogen taken out (demand amount)). It has the disadvantage that it varies.

Furthermore, since this device rotates at high speed, it requires high precision in its mechanical structure, is expensive, and has the disadvantage that specially trained personnel are required due to the complicated mechanism. That is,
Since the expansion turbine has a high-speed rotating section, the above-mentioned problems arise, and there has been a strong desire to eliminate the expansion turbine having such a high-speed rotating section.

[Means for solving problems]

This invention was made in view of the above circumstances, and includes an air compression means for compressing air taken in from the outside, and a removal means for removing carbon dioxide and moisture from the compressed air compressed by the air compression means. A heat exchange means cools the compressed air that has passed through the removal means to an ultra-low temperature, and a part of the compressed air cooled to an ultra-low temperature by this heat exchange means is liquefied and stored at the bottom, and only nitrogen is taken out as a gas from the upper part. A nitrogen gas production device equipped with a rectification column includes a dephlegmator provided above the rectification column for storing liquid nitrogen, a liquid nitrogen storage means for receiving and storing liquid nitrogen from outside the device, and a liquid nitrogen storage means for receiving and storing liquid nitrogen from outside the device. The liquid nitrogen in the liquid nitrogen storage means is continuously introduced into the stored liquid nitrogen in the partial condenser in the rectification column as a cold source for compressed air liquefaction instead of the cold heat generated from the cold heat generation expander ( an introduction path, a control means for controlling the liquid level of the dephlegmator, and a control means for controlling the liquid level of the nitrogen gas taken out as a gas from the rectification column and the liquid nitrogen that has finished acting as a cooling source and has been vaporized in the rectification column. A nitrogen gas take-off passage is provided at an intermediate portion between the nitrogen gas take-off passage and the nitrogen gas that flows through the nitrogen gas take-off passage is provided at an intermediate portion of the nitrogen gas take-off passage. A condenser that cools and condenses and liquefies a part of the air, a cooling means that uses the cold heat of the liquid air accumulated at the bottom of the rectification column to cool the inside of the condenser, and a part of the liquid air that is generated by condensation and liquefaction in the condenser. The gist of the present invention is a nitrogen gas production apparatus characterized by comprising a return path for returning liquid nitrogen from the condenser to the rectification column.

In other words, the nitrogen gas production device of this invention uses the heat of vaporization of liquid nitrogen to cool the compressed air sent to the rectification column, liquefies and separates a portion of the compressed air, and retains the nitrogen as a gas. However, this is extracted as a product nitrogen gas by combining it with the vaporized liquid nitrogen after it has finished its role as a cold source in the rectification column, eliminating the need for an expansion turbine. Bad effects such as variations can be avoided, and nitrogen gas can be obtained at low cost. In particular, this device is equipped with a condenser in the middle of the nitrogen gas extraction path to cool the nitrogen gas flowing through the nitrogen gas extraction path, liquefy a portion of it, and return it to the rectification column. Therefore, 1. the condenser begins to produce rectifying action. As a result, even if the purity of the liquid nitrogen supplied from the liquid nitrogen storage means to the partial condenser of the rectification column is somewhat poor, product nitrogen gas with stable purity can be produced at all times without being affected by this. become. Moreover, this device is less likely to fail because it does not require a large number of valves like the PSA system. Therefore, unlike the PSA method, it is not necessary to prepare a set of two adsorption tanks as a backup, and equipment costs can also be saved.

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

〔Example〕

FIG. 2 is a block diagram of an embodiment of the present invention.

In the figure, 9 is an air compressor, 1O is a doshin separator, 1
1 is a fluorocarbon cooler, and 12 is a set of two adsorption cylinders. The adsorption cylinder 12 is filled with molecular sieve inside and absorbs HtO and CO in the air compressed by the air compressor 9.
! It has the effect of adsorbing and removing. 13 is the first heat exchanger, and the adsorption column 12 generates ■20 and CO! The compressed air that has been adsorbed and removed is sent in. 14 is a second heat exchanger, into which the compressed air that has passed through the first heat exchanger 13 is sent. 15 is a rectification column equipped with a dephlegmator 16 at the top for storing liquid nitrogen, and a first and second heat exchanger 13
．． The compressed air cooled to an ultra-low temperature by 14 is further cooled, a part of which is liquefied and stored at the bottom, and only nitrogen in a gaseous state is taken out from the top. That is, this rectification column 15 includes first and second heat exchangers 13.14.
The compressed air cooled to an ultra-low temperature (approximately -170°C) is transferred to the liquid air stored at the bottom of the rectification column 15 (
N250-70%, 0130-50%) is passed through 18 for further cooling, then injected into the interior through an expansion valve 19, oxygen, etc. are liquefied in a partial condenser 16, and nitrogen remains as a gas. . The decentralizer 16 is separated from the column section 22 by a partition plate 21 in which a large number of tubes 20 are installed. Liquid nitrogen supplied from the nitrogen storage tank 23 through the introduction path vibrator 24 is stored. The dephlegmator 16 guides the compressed air injected into the rectification column 15 into the tube 20 and cools it with the cold heat of the stored liquid nitrogen, liquefies oxygen (boiling point -183°C) and causes it to flow down. Nitrogen (boiling point -196°C) is moved upward as a gas. A portion of the gaseous nitrogen that has moved upward is liquefied as described above and becomes liquid nitrogen stored on the partition plate 21.

In this case, the compressed air injected into the column section 22 of the rectification column 15 contacts the liquid oxygen flowing down from the tube 20 in a countercurrent manner. Therefore, liquefaction and separation of oxygen is further promoted. 25
is a liquid level gauge that keeps the liquid level of the liquid nitrogen stored in the dephlegmator 16 constant, and controls the valve 26 according to fluctuations in the liquid level of the liquid nitrogen in the dephlegmator 16 to control the liquid nitrogen from the liquid nitrogen storage tank 23. control the amount of liquid nitrogen supplied. 27 is a take-out pipe for taking out the nitrogen gas accumulated in the upper part of the dephlegmator 16, and the extremely low temperature nitrogen gas is taken out from the second pipe. The air is guided into the first 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. A condenser 35 is provided in the middle of the take-out pipe 27, and is configured to condense and liquefy a portion of the nitrogen gas flowing through the take-out pipe 27 and store it as liquid nitrogen 37 at the bottom.

A cooling pipe 35a is provided in the condenser 35, and one end 35b communicates with the bottom of the rectification column 15, and liquid air 18 accumulated at the bottom of the rectification column 15 is introduced through the expansion valve 19. It also generates cold heat for condensing and liquefying the nitrogen gas. The other end 35c of the cooling pipe 35a
extends through the second and first heat exchangers 14.13 and transfers the liquid air after generating cold heat to said heat exchanger 1.
3.14 It exchanges heat with the raw material air sent into the interior, heats it up, vaporizes it, and releases it into the atmosphere as shown by arrow A. 29a is its pressure holding valve. A return pipe 38 is designed to return the liquid nitrogen 37 accumulated at the bottom of the condenser 35 to the upper part of the rectification column section 22 as a reflux liquid using a head difference. Reference numeral 30 denotes a backup system line, in which liquid nitrogen in the liquid nitrogen storage tank 23 is evaporated by an evaporator 31 and transferred to the main pipe 2 when the air compression system line breaks down.
8 to ensure that the supply of nitrogen gas does not stop. 32 is an impurity analyzer, and main pipe 2
The purity of the product nitrogen gas sent out from 8 is analyzed, and when the purity is low, the valves 34 and 34a are operated to release the product nitrogen gas to the outside as shown by arrow B. 33 is a pressure regulating valve.

This device produces product nitrogen gas in the following manner. That is, air is compressed by an air compressor 9, water in the compressed air is removed by a drain separator 10, and cooled by a fluorocarbon cooler 11. In this state, the air is sent to an adsorption column 12 filled with molecular sieve. , adsorbs and removes HtO and CO2 in the air. Then, H,0,
The compressed air from which CO□ has been adsorbed and removed is transferred to the first heat exchanger 3.
Then, it is sent to the second heat exchanger 14 to be cooled to an ultra-low temperature, further cooled by the stored liquid air 18 at the bottom of the rectification column 15, and then injected into the rectification column 15. And the difference between the boiling points of nitrogen and oxygen (boiling point of oxygen -183℃, boiling point of nitrogen -1
(96°C) to liquefy oxygen in the air and extract nitrogen as a gas. Then, this is put into the condenser 35 and a part of it is liquefied, and it is returned to the upper part of the column section 22 of the rectification column 15a as a reflux liquid via the return pipe 38, and the remaining part (gas) is heated to the first or second heat source. The liquid nitrogen in the liquid nitrogen storage tank 23 is fed into exchangers 13 and 14, heated to near room temperature, and taken out from the main pipe 28 as nitrogen gas.
It acts as a cold source for the partial condenser 16 of the rectification column 15, and is vaporized and sent into the main pipe 28, and is combined with the nitrogen gas in the air obtained from the rectification column 15 and taken out as a product nitrogen gas. It will be done.

In this way, according to this nitrogen gas production device, compressed air is cooled using the heat of vaporization of liquid nitrogen, and the compressed air is sent to the rectification column 1.
5 to separate oxygen, etc., extract only nitrogen, and combine this with liquid nitrogen (in gaseous form), which is the cooling source, to produce nitrogen gas, completely eliminating the above-mentioned problems caused by expansion turbines. It is possible to obtain highly pure nitrogen gas at an extremely low cost.

That is, by setting the rectification column 15 with high precision,
Nitrogen gas with a purity of 99.999% can be obtained without variation in purity. On the other hand, a PSA type nitrogen gas production device can only obtain a purity of 99.3% at most, and a cryogenic liquefaction separation device using an expansion turbine causes variations in purity when the load fluctuates. In particular, this device is equipped with a condenser 35 in the middle of the nitrogen gas extraction pipe 27 to cool the nitrogen gas flowing through the nitrogen gas extraction pipe 27 and liquefy a part of it.
Since the liquid is returned to the upper part of the column as a reflux liquid, the condenser 35 comes to exert a rectification effect, and at the same time, the amount of reflux liquid in the rectification column section 22 increases. As a result, even if the purity of the liquid nitrogen supplied from the liquid nitrogen storage tank 23 to the demultiplexer 16 of the rectification column 15 is somewhat poor, product nitrogen gas with stable purity can be produced at all times without being affected by the purity. At the same time, the rectification effect can be improved by increasing the amount of reflux liquid. Moreover, this nitrogen gas production device can respond quickly even if there are fluctuations in the demand for product nitrogen gas because the liquid level gauge 25 controls the opening and closing of the valve 26 according to the fluctuations. , this is a major feature.

As described above, the nitrogen gas production apparatus of the present invention allows highly pure nitrogen gas to be obtained in a stable state, so that it can be directly used in the electronic industry. Furthermore, since this gas does not contain carbon dioxide (it is removed within the manufacturing equipment), there is no need to separately equip an adsorption tank for carbon dioxide, and what is more, all you need to do is supply a small amount of liquid nitrogen. A large amount of nitrogen and gas can be obtained. That is, according to the nitrogen gas production apparatus of the present invention, by sending 100 Nnr (gas equivalent) of liquid nitrogen from the liquid nitrogen storage tank 23 to the dephlegmator 16, a product nitrogen gas of 100 ON- can be obtained. In this way, according to this manufacturing apparatus, by supplying only a small amount of liquid nitrogen, 10 times as much product nitrogen gas can be obtained. Therefore, extremely cheap nitrogen gas can be obtained. Also, P.S.A.
Compared to nitrogen gas production equipment using the conventional cryogenic liquefaction separation method that uses expansion turbines and expansion turbines, the equipment is simple and inexpensive, and it does not require a large number of valves.
The reliability of the device is high. It also eliminates the need for special personnel due to expansion turbines. Moreover, since a backup system line is provided, nitrogen gas can be supplied even when the air compression system line is malfunctioning, and the supply of nitrogen gas will not be interrupted.

Note that the return destination of the liquid nitrogen in the condenser 35 is not limited to the upper part of the column section 22 of the rectification column as described above. For example, it may be returned to the demultiplexer 16 as shown in FIG. In this case, the effect of increasing the reflux liquid in the rectification column section 22 will not be obtained, but the rectification effect of the condenser 35 will be exerted, so the purity of the liquid nitrogen in the liquid nitrogen storage tank 23 will deteriorate to some extent. But don't be influenced by it.

〔Effect of the invention〕

As described above, the nitrogen gas production device of the present invention does not use an expansion turbine and instead uses a 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. Failures do not occur.Moreover, the expansion turbine is a high-speed rotating device, and it is difficult to operate to closely follow load fluctuations (changes in the amount of product nitrogen gas taken out). 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. In particular, the apparatus of the present invention is configured such that a condenser is provided in the middle of the nitrogen gas take-off passage to cool the nitrogen gas flowing through the nitrogen gas take-off passage, liquefy a part of it, and return it to the rectification column. Because there are
The condenser comes to perform a rectifying action. As a result, even if the purity of the liquid nitrogen supplied from the liquid nitrogen storage means to the fractionator of the rectification column is somewhat poor, product nitrogen gas with stable purity can be produced at all times without being affected by this. It has excellent effects.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional example, FIG. 2 is a block diagram of one embodiment of the present invention, and FIG. 3 is a block diagram of another embodiment.

Claims (1)

[Claims] (1) An air compression means for compressing air taken in from the outside, a removal means for removing carbon dioxide and moisture from the compressed air compressed by the air compression means, and a removal means for removing the compressed air after passing through the removal means. A nitrogen gas production device equipped with a heat exchange means that cools the air to an ultra-low temperature, and a rectification column that liquefies a portion of the compressed air cooled to an ultra-low temperature by the heat exchange means, stores it at the bottom, and extracts only nitrogen as a gas from the top. , a dephlegmator installed in the upper part of the rectification column stores liquid nitrogen, a liquid nitrogen storage means for receiving and storing liquid nitrogen from outside the apparatus, and a liquid nitrogen storage means for storing liquid nitrogen in the liquid nitrogen storage means. An introduction path that continuously leads into the stored liquid nitrogen in the partial condenser in the rectification column as a cold source for compressed air liquefaction in place of the generated cold heat from the generation expander, and a liquid level in the partial condenser. and a control means for controlling the nitrogen gas taken out as a gas from the rectification column and the liquid nitrogen which has finished acting as a cold source and has been vaporized in the rectification column and exchanges heat with the compressed air through the heat exchange means. A nitrogen gas take-off passage that raises the temperature by exchanging the nitrogen gas to produce a product nitrogen gas; and a condenser that cools the nitrogen gas flowing through the nitrogen gas take-out passage and condenses and liquefies a part of it, which is provided in the middle of the nitrogen gas take-off passage. a cooling means for cooling the inside of the condenser using the cold heat of the liquid air accumulated at the bottom of the rectifying column; A nitrogen gas production device characterized by being equipped with a return path for returning to a tower.