JPH07305952A - Preparation of nitrogen gas - Google Patents

Abstract

PURPOSE:To allow to delicately follow up a load change by providing a nitrogen gas discharge passage in which a temperature rise is obtained by heat exchanging nitrogen gas and liquid nitrogen with compressed air via heat exchange means to obtain product nitrogen gas. CONSTITUTION:A fractionating tower 15 further cools compressed air cooled by first, second heat exchangers 13, 14, liquefies the part of the air, and stores it in the bottom of a dephlegmator 16. On the other hand, nitrogen gas generated when it is liquefied and separated in contact with the compressed air on a partition plate 21 via an introducing pipe 24 from a liquid nitrogen storage tank 23 is stored in the upper part of the dephlegmator 16. The gas stored in the upper part is taken out, and fed to a main pipe 28 via a pipe 27, and the second and first exchangers 14, 13. The fed gas is analyzed for purity as product nitrogen gas. When its purity is low, valves 34, 34a are operated to release the product gas out of a direction B. Accordingly, the gas having stable purity can be manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitrogen gas production device.

[0002]

2. Description of the Related Art An extremely large amount of nitrogen gas is used in the electronic industry. Therefore, inexpensive nitrogen gas is desired to be supplied, and the PSA method has been introduced to meet the request, whereby nitrogen gas is manufactured and supplied. FIG. 1 shows a nitrogen gas production apparatus using this PSA method. In the figure, 1 is an air intake, 2 is an air compressor,
3 is an aftercooler, 3a is a cooling water supply passage, and 4 is an oil / water separator. Reference numeral 5 is a first adsorption tank, 6 is a second adsorption tank, V ₁ and V ₂ are air actuated valves, and the air compressed by the air compressor 2 is sent to the adsorption tank 6 by a valve action. V ₃ and V ₄ are vacuum valves, and the adsorption tank 5,
The inside of 6 is evacuated by the action of the vacuum pump 6a. 6
b is a cooling pipe for supplying cooling water to the vacuum pump 6a, 6
c 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, which is connected to the adsorption tanks 5 and 6 by a pipe 8. Reference numeral 7a is a product nitrogen gas extraction pipe, 7b is an impurity analyzer, and 7c is a flow meter.

This nitrogen gas producing apparatus compresses air by an air compressor 2, cools the air compressed by an aftercooler 3 attached to the air compressor 2 and removes condensed water by a separator 4, Operating valve V ₁ or V ₂
It is sent to the adsorption tanks 5 and 6 via. Each of the two adsorption tanks 5 and 6 contains a carbon molecular sieve for adsorbing oxygen, and compressed air is alternately fed into the adsorption tanks 5 and 6 by the pressure swing method every one minute. In this case, the suction tanks 5 and 6 to which the 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, the oxygen content therein is adsorbed and removed by the carbon molecular sieve, becomes nitrogen gas, and passes through the valves V ₅ , V ₆ and V _9. It is sent to the product tank 7 and taken out from the pipe 7a. At this time, in the other adsorption tank 6, the air from the air compressor 2 is shut off by closing the valve V ₂ and the inside is vacuum-sucked by the vacuum pump 6a by opening the valve V ₄ . As a result, the oxygen adsorbed on the carbon molecular sieve is sucked and removed, 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.

[0004]

Since the above-mentioned nitrogen gas production apparatus produces nitrogen gas by utilizing the characteristic that the carbon molecular sieve selectively adsorbs oxygen, nitrogen gas can be obtained at low cost. However, as described above, compressed air is alternately sent to the two adsorption tanks 5 and 6 every minute, and at the same time, the other adsorption tank is vacuum-sucked, so that a large number of valves are required and It has a drawback that the operation is complicated and failures are likely to occur frequently. Therefore, in reality, it is necessary to provide two sets of two adsorption tanks 5 and 6 and one set as a spare. Therefore,
It also has the drawback of high equipment costs.

On the other hand, a conventional cryogenic liquefaction type nitrogen gas producing apparatus uses an expansion turbine for cooling a heat exchanger for cooling compressed raw material air compressed by a compressor, which is used in a rectification column. It is driven by the pressure of the gas evaporated from the liquid air accumulated in (the low boiling point nitrogen is taken out as a gas by the cryogenic liquefaction separation, and the rest is accumulated as oxygen-rich liquid air). However, the expansion turbine has a very high rotation speed (tens of thousands of times / minute) and it is difficult to follow the load fluctuation (fluctuation of product nitrogen extraction amount <demand amount>). It has a drawback that it varies. Further, since this machine rotates at high speed, it requires high precision in terms of mechanical structure, is expensive, and has a complicated mechanism, which requires specially trained personnel. That is, since the expansion turbine has a high-speed rotating portion, the above-mentioned various problems occur, and there is a strong demand for the removal of the expansion turbine having such a high-speed rotating portion.

[0006]

According to the present invention, there is provided air compression means for compressing air taken in from the outside, and removal means for removing carbon dioxide gas and moisture in the compressed air compressed by the air compression means, A heat exchange means for cooling the compressed air that has passed through this removal means to an ultra-low temperature, and a rectification section for liquefying a part of the compressed air cooled to an ultra-low temperature by this heat exchange means and collecting it in the bottom part to extract only nitrogen as gas from the upper side In a nitrogen gas production apparatus equipped with a tower, a partial condenser provided at the upper part of the rectification tower to make a reflux liquid by cold heat of liquid nitrogen and continuously flow it down into the rectification tower, Liquid nitrogen storage means for receiving the supply and storing the liquid nitrogen in the liquid nitrogen storage means continuously as a cold source for liquefying compressed air in place of the cold heat generated from the expander for cold heat generation Within Introducing passage, nitrogen gas taken out as a gas from the rectification tower and the liquid nitrogen vaporized after finishing the function as a cold source in the rectification tower are exchanged with the compressed air through the heat exchange means. Therefore, the gist of the present invention is a nitrogen gas production apparatus characterized in that it is provided with a nitrogen gas extraction path for raising the temperature to produce product nitrogen gas.

That is, the nitrogen gas production apparatus of the present invention utilizes the heat of vaporization of liquid nitrogen to cool the compressed air sent to the rectification column and liquefy and separate a portion of the compressed air to convert nitrogen into a gas. The expansion turbine is no longer necessary because it is retained as it is and taken out as product nitrogen gas together with liquid nitrogen that has vaporized after completing the action as a cold source in the rectification tower, and when the load changes due to the expansion turbine. It is possible to avoid adverse effects such as variations in purity, and to obtain nitrogen gas at low cost. In addition, this equipment is equipped with a liquid nitrogen evaporator separate from the rectification tower, and when there is a failure in the rectification tower line or when there is a large increase in the demand for product nitrogen gas that cannot be handled by the rectification tower alone. Since the liquid nitrogen in the liquid nitrogen storage means can be vaporized as product nitrogen gas in the liquid nitrogen evaporator by operating the liquid nitrogen evaporator, the supply of product nitrogen gas is interrupted or the demand amount is greatly increased. The purity of the product nitrogen gas does not deteriorate.

Next, the present invention will be described in detail based on embodiments.

[0009]

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, and 1
Reference numeral 1 is a CFC cooler, and 12 is a set of two adsorption tubes. The adsorption cylinder 12 is filled with molecular sieve and has H ₂ O and CO in the air compressed by the air compressor 9.
_It acts to adsorb and remove ₂ . Reference numeral 13 denotes 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 fed. Reference numeral 14 is a second heat exchanger, into which the compressed air that has passed through the first heat exchanger 13 is fed. Reference numeral 15 is a rectification column equipped with a partial condenser 16 for accumulating liquid nitrogen at the top of the column, and the first and second heat exchangers 1
The compressed air cooled to an ultra-low temperature by 3, 14 is further cooled, a part of it is liquefied and stored in the bottom part, and only nitrogen is taken out from the upper part in a gas state. That is,
The rectification tower 15 includes the first and second heat exchangers 13, 1
The compressed air cooled to ultra-low temperature (about -170 ° C.) via 4 is passed through the pipe 17 into the stored liquid air (N ₂ 50 to 70%, O ₂ 30 to 50%) 18 at the bottom of the rectification column 15. It is cooled and then injected through the expansion valve 19 to liquefy oxygen and the like in the rectification shelf and the partial condenser 16, and leave nitrogen as a gas. This demultiplexer 16 is
It is separated from the tower section 22 by a partition plate 21 in which a large number of tubes 20 are planted, and the liquid nitrogen and liquid nitrogen storage tanks 23 produced during the liquefaction separation of the compressed air are separated from the first section from the tower section 22. The liquid nitrogen supplied through the introduction path pipe 24 is stored. The demultiplexer 16 guides the gas derived from the compressed air rising in the rectification tower 15 through the rectification shelf into the tube 20 and cools it with the cold heat of the stored liquid nitrogen,
At the same time that the gas is partially condensed, a trace amount of oxygen (boiling point −183 ° C.) and the like in the gas is liquefied and allowed to flow down, and nitrogen (boiling point −19 ° C.)
(6 ° C.) is moved upward as a gas. Part of the gaseous nitrogen that has moved upward is liquefied as described above to become the stored liquid nitrogen on the partition plate 21.

In this case, the compressed air injected into the column portion 22 of the rectification column 15 comes into countercurrent contact with the liquid oxygen flowing down from the tube 20, so that the liquefaction separation of oxygen is further promoted. A liquid level gauge 25 keeps the liquid level of the stored liquid nitrogen in the decompressor 16 constant, and controls the valve 26 according to the fluctuation of the liquid level of the liquid nitrogen in the decompressor 16 to control the liquid nitrogen storage tank 23.
Controls the supply of liquid nitrogen from. 27 is a demultiplexer 16
With the take-out pipe for taking out the nitrogen gas accumulated in the upper part of the reactor, the ultra-low temperature nitrogen gas is supplied to the second and first heat exchangers 14, 1.
It guides the inside of the pipe 3 and exchanges heat with the compressed air fed therein to bring it to room temperature and feeds it into the main pipe 28.
29 is a feed pipe for feeding the stored liquid air 18 at the bottom of the rectification column 15 to the second and first heat exchangers 14 and 13, and 29a is a pressure-holding valve. The stored liquid air that has completed the 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 to be the first.
The heat is discharged from the heat exchanger 13 as indicated by arrow A. Reference numeral 30 denotes a backup system line, which is a liquid nitrogen evaporator 31, a second introduction path pipe 30a for supplying liquid nitrogen from the liquid nitrogen storage tank 23 to the liquid nitrogen evaporator 31, and a main pipe for the nitrogen gas vaporized and produced by the liquid nitrogen evaporator 31. 28
It is composed of a guide pipe 30b that is fed to the guide pipe 30b and a pressure control valve 33a provided on the guide pipe 30b. The pressure control valve 33a opens the valve or adjusts the opening of the valve when the pressure on the secondary side (use side) falls below a set pressure,
The pressure on the secondary side acts to maintain the set pressure. In this backup system line 30, when the pressure in the main pipe 28 decreases due to a failure of the rectification column line or a large increase in the demand amount of product nitrogen gas, the pressure control valve 33a is opened. Therefore, liquid nitrogen flows from the liquid nitrogen storage tank 23 into the liquid nitrogen evaporator 31 and is vaporized, and the generated vaporized nitrogen gas flows into the main pipe 28 as product nitrogen gas. An impurity analyzer 32 analyzes the purity of the product nitrogen gas sent out from the main pipe 28. When the purity is low, the valves 34 and 3 are used.
4a is operated to release the product nitrogen gas to the outside as shown by arrow B. Reference numeral 33 is a pressure control valve provided in the main pipe 28.

This apparatus produces product nitrogen gas as follows. That is, air is compressed by the air compressor 9, water in the air compressed by the drain separator 10 is removed and cooled by the freon cooler 11, and then fed into the adsorption cylinder 12 filled with the molecular sieve. , for adsorbing and removing H ₂ O and CO ₂ in air. Then, 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 ultralow temperature, and the stored liquid air in the lower portion of the rectification column 15 is further cooled. After cooling at 18, it is injected into the rectification column 15. Then, the oxygen in the air is liquefied by utilizing the difference between the boiling points of nitrogen and oxygen (boiling point of oxygen-183 ° C., boiling point of nitrogen-196 ° C.), and the nitrogen is taken out as a gas to remove the first or second heat. It is sent to the exchangers 13 and 14 and the temperature is raised to near room temperature and taken out from the main pipe 28 as nitrogen gas. In this case, the liquid nitrogen in the liquid nitrogen storage tank 23 is the liquid nitrogen in the fractionator 1 of the rectification column 15.
6, which itself functions as a cold source, is vaporized and sent into the main pipe 28, is combined with the nitrogen gas in the air obtained from the rectification column 15, and is taken out as product nitrogen gas.

As described above, according to this nitrogen gas producing apparatus, the compressed air is cooled by utilizing the heat of vaporization of liquid nitrogen, and the compressed air is sent to the rectification column 15 to separate oxygen and the like and take out only nitrogen, This is combined with liquid nitrogen (which is in a gaseous state) that has become a cold source to produce product nitrogen gas, so the above-mentioned harmful effects caused by the expansion turbine do not occur at all, extremely inexpensive and high-purity nitrogen gas is produced. Obtainable.

That is, by setting the rectification column 15 with high accuracy, it is possible to obtain nitrogen gas having a purity of 99.999% without variation in purity. On the contrary,
At most 99.3 in the PSA type nitrogen gas production equipment
Since only the one with a purity of 10% can be obtained, the refrigerating liquefaction separation apparatus using the expansion turbine has a variation in the purity when the load changes. In addition, this nitrogen gas manufacturing apparatus can respond promptly even if the demand amount of the product nitrogen gas fluctuates, because the liquid level gauge 25 controls the opening degree and opening / closing of the valve 26 according to the fluctuation. Then, when the demand volume increases significantly that cannot be handled by the valve control by the liquid level gauge 25,
Alternatively, when product nitrogen gas cannot be obtained from the rectification tower 15 due to a failure of the rectification tower line, the backup system line 30 is activated and the liquid nitrogen in the liquid nitrogen storage tank 23 is directly vaporized by the evaporator 31. Since the product nitrogen gas is supplied to the main pipe 28 as the product nitrogen gas, the occurrence of a decrease in the purity of the product nitrogen gas at the time of a large increase in the demand amount and the pouring of the product nitrogen gas are avoided, and the product nitrogen gas is always stably supplied. This is a major feature. Moreover, since this device uses one liquid nitrogen storage tank 23 as both storage tanks for the rectification tower line and the backup line, the equipment cost can be greatly saved and the installation space for the liquid nitrogen storage tank can be reduced. The entire device can be made compact, which is also a major feature.

As described above, according to the nitrogen gas production apparatus of the present invention, high-purity nitrogen gas can be obtained in a stable state, so that it can be directly applied to the electronics industry.
Since this gas does not contain carbon dioxide gas (which has been removed in the manufacturing apparatus), it is not necessary to separately install an adsorption tank for carbon dioxide gas. Furthermore, a large amount of nitrogen gas can be obtained by supplying a small amount of liquid nitrogen.
That is, according to the nitrogen gas production apparatus of the present invention, 1000 Nm ³ of product nitrogen gas can be obtained by sending 100 Nm ³ (gas equivalent) of liquid nitrogen from the liquid nitrogen storage tank 23 to the partial condenser 16. As described above, according to this manufacturing apparatus, by supplying a small amount of liquid nitrogen, product nitrogen gas which is 10 times as much as the product nitrogen gas can be obtained.
Therefore, extremely inexpensive nitrogen gas can be obtained. Further, as compared with the conventional cryogenic liquefaction separation method nitrogen gas production apparatus using the PSA method or expansion turbine, the apparatus is simple and the entire apparatus is inexpensive, and a large number of valves and the like are not required. The reliability is high. Also, no special personnel are required due to the expansion turbine.

FIG. 3 is a block diagram of another embodiment. In this nitrogen gas production apparatus, a condenser 35 is attached above the rectification column 15 and communicated with an upper portion of the partial condenser 16 by a communication pipe 36, and nitrogen gas accumulated in the upper portion of the partial condenser 16 (the partial condenser The nitrogen gas obtained by liquefying and separating oxygen by the vessel 16 + the vaporized nitrogen gas of liquid nitrogen supplied from the liquid nitrogen storage tank 23) is put into the condenser 35. One end 35b of this nitrogen gas communicates with the bottom of the rectification column 15, and the other end 35c communicates with the second and first heat exchangers 14, 1.
3 is cooled by a cooling pipe 35a that is open to the air (refrigerant is stored liquid air at the bottom of the rectification column 15) to condense a part of the liquid nitrogen 37, and the generated liquid nitrogen 37 is utilized by the head difference. The uncondensed nitrogen gas is fed back into the main pipe 28 through the second and first heat exchangers 14 and 13 from the return pipe 38 into the partial condenser 16. The other parts are the same as those in the above-described embodiment, and the same parts are designated by the same reference numerals.

That is, in this nitrogen gas producing apparatus, the product nitrogen gas obtained from the upper portion of the partial condenser 16 is guided to the condenser 35, a part of it is condensed and returned to the partial condenser 16, and the liquid nitrogen storage tank 23 In order to adjust to the liquid nitrogen supplied from the condenser 35, the condenser 35 comes to exert a rectification action. Therefore, it is possible to obtain an excellent effect that liquid nitrogen having a low purity can be used as the liquid nitrogen to be supplied to the liquid nitrogen storage tank 23, as compared with the devices of the above-described embodiments. FIG. 4 is a block diagram of another embodiment. In this nitrogen gas producing apparatus, the return pipe 38 is connected to the upper part of the rectification column 15 instead of the partial condenser 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 those in the embodiment of FIG. 3, and the same parts are designated by the same reference numerals.

According to this embodiment, in addition to the same effect as described above, the rectification effect can be improved because the amount of reflux liquid is increased.

[0018]

As described above, the nitrogen gas production apparatus of the present invention does not use an expansion turbine, but instead uses liquid nitrogen storage means such as a liquid nitrogen storage tank having no rotating part, so that the entire apparatus is used. As a result, there is no rotating part and no failure occurs. Moreover, since the expansion turbine is a high-speed rotating device, it is difficult to perform detailed follow-up operation with respect to load fluctuations (changes in the amount of product nitrogen gas taken out). However, the device of the present invention uses a liquid nitrogen storage tank instead of the expansion turbine. Since liquid nitrogen whose supply amount can be finely adjusted is used as a cold source, it is possible to finely follow load fluctuations, and nitrogen gas with stable purity and extremely high purity can be produced. In particular, the apparatus of the present invention is equipped with a liquid nitrogen evaporator separately from the rectification tower, and when the rectification tower line fails or the rectification tower alone cannot cope with the large demand for product nitrogen gas. At the time of increase, since the liquid nitrogen evaporator can be operated and the liquid nitrogen of the liquid nitrogen storage means can be vaporized as product nitrogen gas in the liquid nitrogen evaporator,
This has an excellent effect that the supply of the product nitrogen gas is not interrupted and the purity of the product nitrogen gas is not deteriorated when the demand amount is greatly increased. Moreover, since this device shares one liquid nitrogen storage means as liquid nitrogen storage means for both the rectification column line and the backup line, the facility cost can be significantly reduced, and at the same time, liquid nitrogen storage tanks and other liquid storage tanks can be saved. The installation space of the nitrogen storage means can be made small, and the entire apparatus can be made compact, which is a major feature.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a conventional example.

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

FIG. 3 is a configuration diagram of another embodiment.

FIG. 4 is a configuration diagram of still another embodiment.

[Explanation of symbols]

 9 Air compressor 12 Adsorption column 13,14 Heat exchanger 15 Fractionation tower 16 Fractionator 18 Storage liquid air 23 Liquid nitrogen storage tank 24 First inlet pipe 25 Liquid level gauge 26 Valve 27 Extraction pipe 28 Main pipe 30 Backup Line system 30a Second introduction path pipe 31 Liquid nitrogen evaporator 33, 33a Pressure control valve

Claims (1)

[Claims] 1. An air compression means for compressing air taken in from the outside, a removal means for removing carbon dioxide gas and moisture in the compressed air compressed by the air compression means, and compressed air passed through this removal means. Nitrogen gas production apparatus equipped with heat exchange means for cooling to ultra-low temperature and a rectification column for liquefying a part of the compressed air cooled to ultra-low temperature by this heat-exchange means and collecting it in the bottom part to extract only nitrogen as gas from the upper side In the above, in the upper part of the rectification tower, a partial condenser which forms a reflux liquid by the cold heat of liquid nitrogen and continuously flows it down into the rectification tower, and a liquid which receives the supply of liquid nitrogen from the outside of the device and stores it Nitrogen storage means, the liquid nitrogen in the liquid nitrogen storage means, instead of the generated cold heat from the expander for cold heat generation, an introduction path for continuously introducing into the rectification column as a cold source for liquefying compressed air, and From the rectification tower The nitrogen gas taken out as a gas and the liquid nitrogen vaporized after completing the action as a cold source in the rectification column are heat-exchanged with the compressed air via the heat exchange means to raise the temperature to obtain product nitrogen gas. A nitrogen gas production apparatus comprising a nitrogen gas extraction passage.