JPS628710B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] This invention relates to a nitrogen gas production apparatus.

[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. Figure 1 shows a nitrogen gas production device using this PSA method. In the figure, 1 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 ₁ and V ₂ are air-operated valves, and air compressed by the air compressor 2 is sent into the adsorption tank 6 by valve action. V ₃ and V ₄ are vacuum valves, and the interiors of the adsorption tanks 5 and 6 are 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. V ₅ , V ₆ , V ₇ and V ₉ are air operated valves. 7 is a product tank, and pipe 8
It is connected to the adsorption tanks 5 and 6 by. 7a is a product nitrogen gas extraction pipe, 7b is an impurity analyzer, 7
c is a flow meter.

This nitrogen gas production device compresses air with an air compressor 2, cools the compressed air with an aftercooler 3 attached to this air compressor 2, and removes condensed water with a separator 4. valve
It is sent to the adsorption tanks 5 and 6 via V ₁ or V ₂ . The two adsorption tanks 5 and 6 each have a built-in carbon molecular sieve for oxygen adsorption, and compressed air is sent into these adsorption tanks 5 and 6 alternately every minute by a pressure swing system. . 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 carbon molecular sieve adsorbs and removes the oxygen therein, and converts it into nitrogen gas, which passes through the valves _V5 ,
It is sent to the product tank 7 via V ₆ and V ₉ 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 _V2 , and the interior 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 characteristic of the carbon molecular sieve that selectively adsorbs oxygen, and therefore can obtain nitrogen gas at a low cost. However, as mentioned above, compressed air is sent alternately to the two adsorption tanks 5 and 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, the reality is that two sets of two adsorption tanks 5 and 6 must be provided, and one set must be kept as a spare. 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 liquid accumulated in the rectification tower to cool the compressed raw air. It is powered by the pressure of gas evaporated from air (low boiling point nitrogen is extracted as a gas through cryogenic liquefaction separation, and the remainder accumulates as oxygen-rich liquid air). However, the rotational speed of expansion turbines is extremely high (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 provides air compression means for compressing air taken in from the outside, removal means for removing carbon dioxide and moisture from the compressed air compressed by the air compression means, and compressed air that has passed through the removal means. A nitrogen gas production system equipped with a heat exchange means that cools 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 this heat exchange means, stores it at the bottom, and extracts only nitrogen as a gas from the upper side. The device includes a dephlegmator installed at the top of the rectification column to store liquid nitrogen for cooling, a liquid nitrogen storage means for receiving and storing liquid nitrogen from outside the device, and a liquid nitrogen storage means inside the liquid nitrogen storage means. a first introduction path that continuously introduces liquid nitrogen into the rectification column as a cold source for liquefying compressed air in place of the cold generated from the cold heat generation expander; and the liquid nitrogen storage means for the rectification column. control means for controlling the liquid level of liquid nitrogen in the dephlegmator to a constant level by controlling the amount of liquid nitrogen supplied from the fractionator; and nitrogen gas taken out as a gas from the rectification column and a nitrogen gas extraction path for increasing the temperature of the liquid nitrogen that has been vaporized after acting as a cold source by exchanging heat with the compressed air through the heat exchange means to produce a product nitrogen gas; a liquid nitrogen evaporator; a second introduction path for guiding liquid nitrogen in the liquid nitrogen storage means to the liquid nitrogen evaporator; and a guide path for guiding nitrogen gas vaporized in the liquid nitrogen evaporator into the nitrogen gas extraction path as product nitrogen gas. The gist of the present invention is a nitrogen gas production apparatus characterized by comprising a control means for controlling the supply of liquid nitrogen from the liquid nitrogen storage means to the rectification column and the liquid nitrogen evaporator.

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 and reducing the purity during the load fluctuations caused by the expansion turbine. Bad effects such as variations can be avoided, and nitrogen gas can be obtained at low cost. Moreover, this device
It is equipped with a liquid nitrogen evaporator separate from the rectification column.
In the event of a breakdown in the rectification column line or in the event of a significant increase in demand for product nitrogen gas that cannot be met by the rectification column alone, the liquid nitrogen evaporator is operated to convert the liquid nitrogen in the liquid nitrogen storage means into liquid nitrogen. Since it can be vaporized as product nitrogen gas in an evaporator, the supply of product nitrogen gas will not be interrupted or the purity of product nitrogen gas will not decrease when the demand increases significantly.

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, 10 is a drain separator, 11 is a fluorocarbon cooler, and 12 is a set of two adsorption cylinders. The adsorption cylinder 12 is filled with a molecular sieve and functions to adsorb and remove H ₂ O and CO ₂ from the air compressed by the air compressor 9. 13 is a first heat exchanger, into which compressed air from which H ₂ O and CO ₂ 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. 15 is a rectification column equipped with a dephlegmator 16 at the top for storing liquid nitrogen, which further cools compressed air that has been cooled to an ultra-low temperature by the first and second heat exchangers 13 and 14; A portion of it is liquefied and stored at the bottom, and only nitrogen is extracted in gaseous form from the top. That is, this rectification column 15 is
The compressed air cooled to an ultra-low temperature (approximately -170°C) via the first and second heat exchangers 13 and 14 is transferred to the stored liquid air (N ₂ 50-70%, It is further cooled by passing through an O ₂ (30 to 50%) 18, and 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. This demultiplexer 16 is
Partition plate 21 on which many tubes 20 are planted
It is separated from the tower section 22 by a partition plate 21.
Liquid nitrogen generated during liquefaction separation of compressed air and liquid nitrogen supplied from the liquid nitrogen storage tank 23 through the first introduction pipe 24 are stored above. 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, liquefying oxygen (boiling point -183°C) and causing it to flow down. It is designed to move nitrogen (boiling point -196°C) upwards as a liquid. 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 comes into contact with the liquid oxygen flowing down from the tube 20 in the same flow, so that the liquefaction and separation of oxygen is further promoted. Reference numeral 25 denotes a liquid level gauge that keeps the liquid level of the liquid nitrogen stored in the decentralizer 16 constant, and the valve 2
6 to control the amount of liquid nitrogen supplied from the liquid nitrogen storage tank 23. Reference numeral 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 transferred to the second and first heat exchangers 14 and 13.
The main pipe 28 is guided into the main pipe 28 by exchanging heat with the compressed air sent there to bring the air to room temperature. 29 is a feed pipe for feeding the liquid air 18 stored at the bottom of the rectification column 15 to the second and first heat exchangers 14, 13, and 29a is a pressure holding valve. The stored liquid air that has completed heat exchange (cooling of the compressed air in the heat exchangers 14 and 13) in the second and first heat exchangers 14 and 13 is vaporized and flows from the first heat exchanger 13 as shown in the arrow It is designed to be released as shown in A. Reference numeral 30 denotes a backup system line, which includes a liquid nitrogen evaporator 31, a second introduction path pipe 30a that supplies liquid nitrogen from the liquid nitrogen storage tank 23 to the liquid nitrogen evaporator 31, and a main pipe that carries the nitrogen gas vaporized and produced in the liquid nitrogen evaporator 31. 28, and a pressure regulating valve 33a provided on the guide pipe 30b. When the pressure on the secondary side (use side) falls below the set pressure, the pressure regulating valve 33a opens the valve or adjusts the degree of opening of the valve, so that the pressure on the secondary side maintains the set pressure. In this backup system line 30, when the pressure inside the main pipe 28 decreases due to a breakdown in the rectification column line or a significant increase in the demand for product nitrogen gas, the pressure regulating valve 33a is opened. Therefore, liquid nitrogen flows from the liquid nitrogen storage tank 23 to the liquid nitrogen evaporator 31 and is vaporized, and the resulting vaporized nitrogen gas flows into the main pipe 28 as product nitrogen gas. 32
is an impurity analyzer that analyzes the purity of the product nitrogen gas sent out from the main pipe 28, and when the purity is low, operates the valves 34, 34a to release the product nitrogen gas to the outside as shown by arrow B. act. 33 is a pressure regulating valve provided in the main pipe 28.

This device produces product nitrogen gas in the following manner. That is, air is compressed by an air compressor 9, moisture 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. , H ₂ O in air and
Adsorbs and removes CO ₂ . Next, the compressed air from which H ₂ O and CO ₂ have been adsorbed and removed is sent to the first heat exchanger 13 and the second heat exchanger 14 to be cooled to an ultra-low temperature, and then the stored liquid air at the bottom of the rectification column 15 is 18
After cooling, it is injected into the rectification column 15. And the difference between the boiling points of nitrogen and oxygen (boiling point of oxygen - 183
℃, the boiling point of nitrogen - 196℃) is used to liquefy oxygen in the air, and nitrogen is taken out as a gas and sent to the first or second heat exchanger 13, 14 where it is heated to near room temperature and then transferred to the main pipe. 28 as nitrogen gas. In this case, the liquid nitrogen in the liquid nitrogen storage tank 23 acts as a cold source for the partial condenser 16 of the rectification column 15, and is itself vaporized to the main pipe 2.
8 and is combined with the nitrogen gas in the air obtained from the rectification column 15 and taken out as a product nitrogen gas.

In this way, according to this nitrogen gas production device,
Cools compressed air using the heat of vaporization of liquid nitrogen,
It is sent to the rectification column 15 to separate oxygen, etc. and extract only nitrogen, which is then combined with liquid nitrogen (in gaseous form), which is the source of cooling, to produce nitrogen gas. It is possible to obtain highly purified nitrogen gas at extremely low cost without causing any of the above-mentioned disadvantages.

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. In contrast, with PSA nitrogen gas production equipment, at most
Only 99.3% purity can be obtained, and in cryogenic liquefaction separators that use expansion turbines, the purity varies when the load fluctuates. Moreover, in this nitrogen gas production apparatus, even if there is a change in the demand for product nitrogen gas, the liquid level gauge 25 controls the degree of opening and opening/closing of the valve 26 in accordance with the change, so that it can respond quickly. When there is a significant increase in demand that cannot be handled by valve control using the liquid level gauge 25,
Or rectifier 15 due to a failure in the rectifier line.
When product nitrogen gas cannot be obtained from the main pipe 28, the backup line 30 is activated and the liquid nitrogen in the liquid nitrogen storage tank 23 is directly vaporized by the evaporator 31, and this is converted into product nitrogen gas to the main pipe 28.
This avoids the occurrence of a decrease in the purity of the product nitrogen gas and the interruption of the product nitrogen gas supply when the demand increases significantly, making it possible to constantly and stably supply the product nitrogen gas, which is a major feature. . Moreover, this device has one liquid nitrogen storage tank and two
3 is shared as a storage tank for both the rectification column line and the back-up line, so equipment costs can be significantly reduced, and at the same time, the installation space for the liquid nitrogen storage tank can be reduced, making the entire device more compact. , this is also a major feature.

As described above, according to the nitrogen gas production apparatus of the present invention, highly purified nitrogen gas can be obtained in a stable state, so that it can be directly used in the electronic industry. And since this gas does not contain carbon dioxide (it is removed in the manufacturing equipment),
There is no need to separately equip an adsorption tank for carbon dioxide gas. Furthermore, a large amount of nitrogen gas can be obtained by simply supplying a small amount of liquid nitrogen. That is,
According to the nitrogen gas production apparatus of the present invention, by sending 100 Nm ³ (gas equivalent) of liquid nitrogen from the liquid nitrogen storage tank 23 to the dephlegmator 16, product nitrogen gas of 1000 Nm ³ can be obtained. In this way, with this production equipment, 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. In addition, compared to nitrogen gas production equipment using the PSA method or the conventional cryogenic liquefaction separation method that uses an expansion turbine, the equipment is simple and inexpensive, and it does not require a large number of valves. High reliability. It also eliminates the need for special personnel due to the expansion turbine.

FIG. 3 is a block diagram of another embodiment. This nitrogen gas production device has a condenser 35 installed above the rectification column 15.
The nitrogen gas stored in the upper part of the partial condenser 16 (nitrogen gas obtained by liquefying and separating oxygen by the partial condenser 16 + liquid) The structure is such that liquid nitrogen (vaporized nitrogen gas) supplied from the nitrogen storage tank 23 is introduced into the condenser 35. One end 35b communicates this nitrogen gas with the bottom of the rectification column 15, and the other end 35c communicates with the second and first heat exchangers 14, 1.
Cooling pipe 3 open to the air through 3
5a (the refrigerant is liquid air stored at the bottom of the rectification column 15), a part of it is condensed, and the generated liquid nitrogen 37 is returned to the demultiplexer 16 from the return pipe 38 using the head difference. Uncondensed nitrogen gas is sent into the main pipe 28 through the second and first heat exchangers 14 and 13. The other parts are the same as those in the previous embodiment, and the same parts are given the same reference numerals.

That is, this nitrogen gas production apparatus has a dephlegmator 1
The product nitrogen gas obtained from the upper part of 6 is transferred to a condenser 35.
The condenser 35 exerts a rectification effect in order to condense a portion of it and return it to the demultiplexer 16 to match the liquid nitrogen supplied from the liquid nitrogen storage tank 23. Therefore, compared to the apparatus of the above-mentioned embodiments, it is possible to obtain the excellent effect that liquid nitrogen of lower purity can be used as the liquid nitrogen to be supplied to the liquid nitrogen storage tank 23.

FIG. 4 is a block diagram of still another embodiment. In this nitrogen gas production apparatus, the return pipe 38 is connected to the upper part of the rectification column 15 instead of the decentralizer 16, so that the condensed liquid nitrogen is returned to the upper part of the rectification column 15. The other parts are the same as the embodiment shown in FIG. 3, and the same parts are given the same reference numerals.

According to this embodiment, in addition to obtaining the same effects as described above, it is also possible to improve the rectification effect because the amount of reflux liquid increases.

〔Effect of the invention〕

As described above, the nitrogen gas production device of the present invention does not use an expansion turbine, but 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. No failures occur. Furthermore, since the expansion turbine is a high-speed rotating device, it is difficult to operate the device to closely follow load fluctuations (changes in the amount of product nitrogen gas taken out).However, the device of this invention uses a liquid nitrogen storage tank instead of the expansion turbine. Since liquid nitrogen is used as the cold source, and the supply amount can be finely adjusted, it is possible to closely follow load fluctuations, and it is possible to produce nitrogen gas with stable and extremely high purity. In particular, the apparatus of the present invention is equipped with a liquid nitrogen evaporator separate from the rectification column, and when the rectification column line breaks down or there is a significant demand for product nitrogen gas that cannot be met by the rectification column alone. At the time of increase, the liquid nitrogen evaporator may be operated and the liquid nitrogen in the liquid nitrogen storage means may be vaporized as product nitrogen gas, which may interrupt the supply of product nitrogen gas or significantly increase the demand. This has the excellent effect that the purity of the product nitrogen gas does not deteriorate during the process. Moreover, since this device uses one liquid nitrogen storage means for both the rectification column line and the backup line, it is possible to significantly reduce equipment costs and at the same time to The installation space for the liquid nitrogen storage means can be reduced, and the entire device can be made more compact, which is a major feature.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional example, Fig. 2 is a block diagram of an embodiment of the present invention, Fig. 3 is a block diagram of another embodiment, and Fig. 4 is a block diagram of yet another embodiment. . 9...Air compressor, 12...Adsorption cylinder, 13,1
4... Heat exchanger, 15... Rectification column, 16... Decentralizer, 18... Storage liquid air, 23... Liquid nitrogen storage tank, 24... First introduction pipe, 25... Liquid level Total, 26...Valve, 27...Takeout pipe,
28...Main pipe, 30...Backup line system, 30a...Second introduction pipe, 31...
...Liquid nitrogen evaporator, 33, 33a...Pressure control valve.

Claims (1)

[Claims] 1. Air compression means for compressing air taken in from the outside, removal means for removing carbon dioxide and moisture 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 nitrogen gas production device equipped with a cooling heat exchange means and a rectification column that liquefies a part 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 upper side, A dephlegmator installed at the top of the rectification column stores liquid nitrogen for cooling, 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. a first introduction path that continuously leads into the rectification column as a cold source for liquefying compressed air in place of the cold generated from the cold heat generation expander, and a liquid from the liquid nitrogen storage means to the rectification column. A control means for controlling the liquid level of liquid nitrogen in the dephlegmator to a constant level by controlling the supply amount of nitrogen, and nitrogen gas taken out as a gas from the rectification column and as a cooling source in the rectification column. a nitrogen gas extraction path for increasing the temperature of the vaporized liquid nitrogen through the heat exchange means and exchanging heat with the compressed air to produce a product nitrogen gas;
a liquid nitrogen evaporator, a second introduction path for guiding liquid nitrogen from the liquid nitrogen storage means to the liquid nitrogen evaporator, and a nitrogen gas extraction path for converting the nitrogen gas vaporized in the liquid nitrogen evaporator into product nitrogen gas. What is claimed is: 1. A nitrogen gas production apparatus comprising: a guide path for guiding the liquid nitrogen into the liquid nitrogen evaporator; and a control means for controlling supply of liquid nitrogen from the liquid nitrogen storage means to the liquid nitrogen evaporator.