JPH0719724A - High purity nitrogen gas preparing apparatus - Google Patents

Abstract

PURPOSE:To respond to variation in a demand amount, to reduce in entire size, to eliminate necessity of skillfulness for an operation and to prepare low- cost product nitrogen gas. CONSTITUTION:Not only generated cold of an expansion turbine but also liquid nitrogen of a liquid nitrogen storage tank is used as cold. A dephlegmator 15 containing a condenser 15a is provided in an upper part of a rectifying tower 10, and part of nitrogen gas in the power 10 is always guided and liquefied in the condenser 15a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high purity nitrogen gas producing apparatus.

[0002]

2. Description of the Related Art Generally, nitrogen gas is produced by a cryogenic liquefaction separator. This type of nitrogen gas production apparatus uses an expansion turbine for cooling the refrigerant of a heat exchanger for exchanging heat with the compressed air compressed by a compressor. The low-boiling-point nitrogen is taken out as a gas by the liquefaction separation, and the balance is driven by the pressure of the gas evaporated from the oxygen-rich liquid air).

[0003]

However, since the expansion turbine has an extremely high rotation speed (tens of thousands of revolutions / minute) and it is difficult to follow the load variation, it is possible to quickly respond to variations in the demand amount of product nitrogen gas. It has the drawback of not being able to deal with.

Further, in this type of nitrogen gas producing apparatus, a considerably high purity nitrogen gas can be produced by increasing the number of rectifying shelves in the rectifying tower. Can not respond to. That is, in the product nitrogen gas obtained by the above-mentioned nitrogen gas manufacturing apparatus, oxygen is mixed as an impurity, so that it is necessary to use the oxygen gas as it is, the ultra high purity nitrogen gas is required. It is often inconvenient in the electronics industry.

As a method of removing impure oxygen, a method of using a Pt catalyst to add a trace amount of hydrogen to nitrogen gas and reacting with impure oxygen in a temperature atmosphere of about 200 ° C. to remove it as water and a Ni catalyst are used. However, there is a method of removing impure oxygen in nitrogen gas by bringing it into contact with a Ni catalyst in an atmosphere of a temperature of about 200 ° C. to cause the following reaction.

[0006]

[Chemical 1]

However, in any of these methods, the temperature of nitrogen gas must be raised to bring it into contact with the catalyst, so that the apparatus cannot be incorporated into a nitrogen gas production apparatus which is an ultra-low temperature system. Therefore, the refining device must be installed separately from the nitrogen gas production device, which has the drawback of increasing the overall size. Moreover, in the above method,
High precision is required for adjusting the amount of hydrogen added, and unless the amount of hydrogen that just reacts with the amount of impure oxygen is added, oxygen will remain or the added hydrogen will remain and become impurities. Therefore, there is a problem that the operation requires skill. Further, in the above method, Ni generated by the reaction with impure oxygen
It was necessary to regenerate O by the reaction shown below, and H ₂ gas equipment for regeneration was required, resulting in an increase in refining costs.

[0008]

[Chemical 2]

Therefore, it is desired to provide a nitrogen gas production apparatus which can cope with fluctuations in demand, is small in size as a whole, does not require skill in operation, and can produce product nitrogen gas at low cost.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a high-purity nitrogen gas producing apparatus having the above-described performance.

[0011]

In order to achieve the above object, the high-purity nitrogen gas producing apparatus of the present invention has an air compression means for compressing the air taken in from the outside, and a compression compressed by the air compression means. Removing means for removing carbon dioxide gas and moisture in the air, heat exchanging means for cooling the compressed air that has passed through this removing means to an ultra low temperature, and liquefying part of the compressed air cooled to an ultra low temperature by this heat exchanging means. In a nitrogen gas production apparatus equipped with a rectification column that takes out only nitrogen stored in the bottom part as a gas from the upper side, a condenser built-in partial condenser provided in the upper part of the rectification column and a bottom part of the rectification column Liquid air introduction pipe for guiding the stored liquid air into the condenser as cold for cooling the condenser, a discharge pipe for discharging vaporized liquid air generated in the condenser to the outside, and vaporization of the discharge pipe Liquid air An expander for generating cold heat by using it to send the generated cold heat to the heat exchange means for cooling, and a first reflux liquid pipe for guiding a part of the nitrogen gas generated in the rectification column into the condenser. A second reflux liquid pipe for returning the liquefied nitrogen produced in the condenser as a reflux liquid into the rectification column, a liquid nitrogen storage means for receiving liquid nitrogen supplied from the outside of the apparatus and storing it, and the liquid nitrogen storage The liquid nitrogen in the means is provided with an introduction path for continuously introducing into the rectification column as cold for liquefying compressed air.

[0012]

In other words, this high-purity nitrogen gas producing apparatus uses not only the cold generated by the expansion turbine but also the liquid nitrogen in the liquid nitrogen storage tank as the cold, so that the fluctuation of the demand amount of the product nitrogen gas, especially a significantly important amount of You will be able to respond quickly to changes. More specifically, since it takes a long time to change the rotation speed of the expansion turbine, it is possible to quickly change the supply amount of liquid nitrogen from the liquid nitrogen storage tank, so that it is possible to quickly respond to the change in the demand amount. become. Moreover, if the fluctuations in demand for product nitrogen gas during the daytime and nighttime are significantly different, an expansion turbine is used to cover the nighttime cold, and the lack of the daytime cold is covered by the liquid nitrogen from the liquid nitrogen storage tank. By supplementing it, it becomes possible to quickly and accurately respond to a drastic change in demand during the day and at night. Furthermore, since this apparatus can obtain high-purity product nitrogen gas, the refining apparatus as in the conventional example becomes unnecessary, and there is no inconvenience that the size of the entire apparatus is increased and skill is required for operation. In addition, the cost of product nitrogen gas is not increased.

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

[0014]

1 is a block diagram of an embodiment of the present 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 tubes. Adsorption cylinder 4
Has an action of adsorbing and removing H ₂ O and CO ₂ in the air compressed by the air compressor 1, which is filled with a molecular sieve. Reference numeral 13 is a compressed air supply pipe for sending compressed air from which H ₂ O and CO ₂ have been adsorbed and removed. Three
Reference numeral 8 is a heat exchanger, and H ₂ O and CO are absorbed by the adsorption cylinder 4.
Compressed air from which ₂ has been adsorbed and removed is fed. As shown in FIG. 2, a rectification column 10 has a condenser 15a with a built-in condenser 15a at the top of the column, is cooled to an ultralow temperature by a heat exchanger 38 (FIG. 1), and is passed through a pipe 16. Compressed compressed air is further cooled and part of it is liquefied and liquid air 3
6 is stored in the bottom part, and only nitrogen is stored in the upper ceiling part in a gas state. In FIG. 1, 7 is a liquid nitrogen storage tank which receives liquid nitrogen supplied from the outside of the device and stores the liquid nitrogen. The liquid nitrogen inside (high purity product) is passed through an introduction passage pipe 40 to the upper side of the rectification column 10. To the rectification tower 1
It is used as a cold source for the compressed air supplied to the inside. Here, the rectification column 10 will be described in more detail. The rectification column 10 is provided with a partial condenser 15 on the upper side of the ceiling plate 20 as shown in FIG. Part of the nitrogen gas accumulated in the upper part of the rectification column 10 is fed into the vessel 15a through the first reflux liquid pipe 15b. This divider 15
The inside is in a reduced pressure state as compared with the inside of the rectification tower 10, and the stored liquid air at the bottom of the rectification tower 10 (N ₂ ; 50 to 70%, O
₂ ; 30-50%) 36 is a pipe 37 with an expansion valve 18a
It is sent via a vaporizer and is vaporized to cool the internal temperature to a temperature below the boiling point of liquid nitrogen. Due to this cooling, the nitrogen gas fed into the condenser 15a from the rectification column 10 through the first reflux liquid pipe 15b is liquefied. 23
Is a liquid level gauge, and controls the valve 24 according to the liquid level of the liquid air in the dephlegmator 15 according to the liquid level to control the supply amount of the liquid nitrogen from the liquid nitrogen storage tank 7. In the upper part of the rectification column 10, the liquid nitrogen produced in the condenser 15a in the partial condenser 15 is connected to the second reflux liquid pipe 15
Liquid nitrogen is supplied from the liquid nitrogen storage tank 7 through the introduction path pipe 40, and these flow down through the liquid nitrogen reservoir 39 to the inside of the rectification tower 10. It comes into contact with the compressed air rising from the bottom of the tank in a countercurrent manner and cools it to liquefy a part thereof.
In this process, the high boiling point component (oxygen) in the compressed air is liquefied and stored at the bottom of the rectification column 10, and the low boiling point component nitrogen gas is stored at the top of the rectification column 10. Reference numeral 41 is an extraction pipe for taking out the nitrogen gas accumulated in the upper ceiling portion of the rectification tower 10 as product nitrogen gas, and guiding ultra-low temperature nitrogen gas into the heat exchanger 38,
It exchanges heat with the compressed air sent therein to bring it to room temperature and sends it into the main pipe 9. 11 is 3Å, 4Å
Or synthetic zeolite 3A, 4A with pore size of 5Å
Or 5A (Molecular sieves 3A, 4A, 5A,
This is an adsorption column for adsorbing impurities such as oxygen filled with Union Carbide Co., Ltd., and is provided in the middle of the extraction pipe 41 to selectively adsorb and remove oxygen and carbon monoxide in the ultra-low temperature nitrogen gas. In addition, the above synthetic zeolite 3
It is also possible to use the synthetic zeolite 13X manufactured by Union Carbide Co. in place of A, 4A and 5A. In this way, since only oxygen and carbon monoxide are selectively adsorbed and removed in the temperature range of about −150 ° C., the ultra low temperature nitrogen gas has high purity. In this case, since the amounts of impure oxygen and carbon monoxide in the ultra-low temperature nitrogen gas introduced into the oxygen adsorption column 11 have already become low due to passing through the rectification column 10, the oxygen and carbon monoxide to be adsorbed. The amount is very small. Therefore, only one suction cylinder 11 is required,
It is enough to regenerate the zeolite once a year. In addition, at the uppermost part in the rectification tower 10, together with nitrogen gas, He (−269 ° C.) and H ₂ (−253) having a low boiling point were used.
(° C) tends to accumulate, so the take-out pipe 41 is
Of the pure nitrogen gas in which He and H ₂ are not mixed is taken out as the product nitrogen gas. Reference numeral 35 denotes a discharge pipe that sends the vaporized liquid air in the dephlegmator 15 to the drive unit of the expansion turbine 34, which drives the expansion turbine 34 (see FIG. 1) by the pressure of the vaporized liquid air and causes the refrigerant to flow through the path of arrow B. The compressed air sent to the heat exchanger 38 is cooled to an ultralow temperature and sent to the rectification tower 10.

This apparatus uses the product nitrogen gas in the following manner.
Manufacture That is, air is compressed by the air compressor 1.
Water in the air compressed by the drain separator 2
Removed and cooled by CFC cooler 3 and adsorbed in that state
It is sent to the cylinder 4 and H in the air ₂O and CO₂Adsorption removal
Leave. Then, H₂O, CO₂Compressed by adsorption
Air is sent from the rectification tower 10 through a pipe 35.
From the product nitrogen gas and expansion turbine, send it by the route of arrow B.
To the heat exchanger 38 that is cooled by the introduced refrigerant.
It is sent and cooled to an ultra-low temperature, and under that state, under the rectification tower 10.
Put in the department. Then, this input compressed air is mixed with liquid nitrogen.
Inside the rectification tower 10 from the elementary storage tank 7 via the introduction pipe 40
From the liquid nitrogen and liquid nitrogen reservoir 39 fed to
Cooling by contacting with overflowing liquid nitrogen, liquefying a part and rectifying
It is stored as liquid air 36 at the bottom of the tower 10. In the process
, The difference between the boiling points of nitrogen and oxygen (boiling point of oxygen-183
℃, boiling point of nitrogen -196 ℃), high boiling point in compressed air
Oxygen, which is a point component, liquefies, and nitrogen remains as a gas. One
Then, take out the nitrogen remaining as this gas from the pipe 41.
Take it out and send it to the heat exchanger 38 to raise the temperature to near room temperature
Then, it is sent out from the main pipe 9 as product nitrogen gas.
On the other hand, regarding the liquid air 36 accumulated in the lower part of the rectification tower 10
Sends it into the condenser 15 to cool the condenser 15a.
Let By this cooling, the condenser from the upper part of the rectification tower 10
Nitrogen gas sent to 15a is liquefied and
It becomes the reflux liquid and passes through the second reflux liquid pipe 15c to the rectification column.
Return to 10. Then, the liquid that has finished cooling the condenser 15a
The air 36 is vaporized and released by the discharge pipe 35 into a heat exchanger 38.
To heat the heat exchanger 38, and then release it into the air.
Will be issued. In addition, from the liquid nitrogen storage tank 7 to the introduction path pipe 40
The liquid nitrogen sent into the rectification column 10 via the
Acts as a cold source for condensed air liquefaction, vaporizing itself
Take out from the take-out pipe 41 as a part of product nitrogen gas
To be done.

Since this high-purity nitrogen gas producing apparatus uses not only the cold generated by the expansion turbine 34 but also the liquid nitrogen in the liquid nitrogen storage tank 7 as cold, fluctuations in the demand amount of the product nitrogen gas, particularly a significantly important amount, You will be able to respond quickly to changes. That is, the expansion turbine is steadily operated to produce a predetermined amount of product nitrogen gas, and the demand fluctuation is supplemented by the liquid nitrogen from the liquid nitrogen storage tank 7, thereby changing the rotation speed of the expansion turbine. Without this, it will be possible to quickly respond to fluctuations in demand. More specifically, since it takes a long time to change the rotation speed of the expansion turbine 34, the supply amount of liquid nitrogen from the liquid nitrogen storage tank 7 can be changed quickly, so that the demand amount can be quickly changed. become able to. Moreover, when the fluctuations in the demand amount of the product nitrogen gas between the daytime and the nighttime are significantly different, the expansion turbine 34 is used to cover the nighttime cold, and the shortage of the daytime cold is supplied from the liquid nitrogen storage tank 7. By supplementing with nitrogen, it will be possible to respond quickly and accurately to significant fluctuations in demand during the day and at night. Furthermore, since this apparatus can obtain high-purity product nitrogen gas, the refining apparatus as in the conventional example becomes unnecessary, and there is no inconvenience that the size of the entire apparatus is increased and skill is required for operation. In addition, the cost of product nitrogen gas is not increased. In particular, this high-purity nitrogen gas production apparatus has a condenser 15 at the top of the rectification tower 10.
Since a partial condenser 15 with a built-in a is provided and a part of the nitrogen gas in the rectification column 10 is constantly guided into the condenser 15a to be liquefied, a predetermined amount of liquefied nitrogen is accumulated in the condenser 15a. Liquefied nitrogen produced thereafter always returns to the rectification column 10 as a reflux liquid. Therefore, the condenser 15a
Fluctuations in product purity due to intermittent supply of reflux liquid from the (from suspension of the flow of the reflux liquid, liquid disappears in the upper rectification shelf, leading to gas blow-through phenomenon, resulting in a decrease in product purity,
When the flow is resumed, the purity of the product does not return to a certain level), and the product nitrogen gas having a stable purity can always be supplied. Moreover, in this apparatus, even if the demand amount of the product nitrogen gas fluctuates, the control means such as the liquid level gauge 23 controls the opening degree of the valve 24 and the like to control the supply amount of the liquid nitrogen to the rectification column 10. As a result, the liquid level of the liquid air in the dephlegmator 15 is controlled to be constant, so that it is possible to quickly respond to the fluctuation of the demand amount, and at this time also, the purity variation does not occur for the reason described above. That is, when the demand amount of the product nitrogen gas increases, most of the generated nitrogen gas is taken out from the extraction pipe 41, the amount of nitrogen gas sent to the condenser 15a is reduced, and the amount of the reflux liquid generated in the condenser 15a is reduced. As a result, the amount of the stored liquid air 36 at the bottom of the rectification column is reduced, and the amount of the liquid air sent therefrom is reduced, so that the liquid level of the liquid air in the partial condenser 15 is lowered. As a result, the level gauge 23
Operates to increase the supply amount of liquid nitrogen to the rectification column 10, and by vaporizing the product nitrogen gas, the product nitrogen gas is rapidly produced to quickly respond to the increase in the demand amount. When the amount of liquid nitrogen stored in the bottom of the rectification column 10 increases due to the increase in the supply amount of liquid nitrogen, and the liquid level in the partial condenser 15 recovers accordingly, the liquid level gauge 23 supplies the liquid to the rectification column 10. The supply amount of nitrogen is properly controlled to be reduced. Contrary to the above, when the demand amount of the product nitrogen gas decreases, the liquid level in the partial condenser 15 rises, so that the liquid level gauge 23 operates to reduce the supply amount of liquid nitrogen to the rectification column 10. Eliminate irrationalities due to excess supply of liquid nitrogen. In this way, this device can quickly and rationally respond to fluctuations in the demand amount of product nitrogen gas without causing variations in purity. In addition, since the adsorption column 11 removes impurities such as oxygen and carbon monoxide, the product nitrogen gas can be further purified, and the raw material air taken from the air compressor 1 can be obtained. It is also possible to use a material containing a large amount of impurities in an industrial area or the like, and it becomes possible to obtain a good result.

FIG. 3 is a block diagram of another embodiment. That is, in this embodiment, a backup system line 12 extending from the liquid nitrogen storage tank 7 to the main pipe 9 is provided, and when the air compression system line fails, the liquid nitrogen in the liquid nitrogen storage tank 7 is evaporated by the evaporator 14, Make sure that the supply of nitrogen gas to the main pipe 9 is not interrupted. Further, the main pipe 9 has an impurity analyzer 27, valves 28, 29.
Is provided, and the purity of the product nitrogen gas sent to the main pipe 9 is analyzed. When the purity is low, the valves 29 and 28 are operated to let the product nitrogen gas escape to the outside as shown by arrow A. There is. Since the other parts are substantially the same as those of the first device, the same parts are designated by the same reference numerals.

This device has the same effect as that of the device shown in FIG. 1, and also has an effect that it does not hinder the supply of the product nitrogen gas even if the air compression system line fails.

[0019]

The high-purity nitrogen gas producing apparatus of the present invention is
Since it is configured as described above, it is possible to cope with the fluctuation of the demand amount, and it is possible to manufacture the product nitrogen gas at a low cost while the whole is small in size and does not require skill in operation.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a detailed view of a main part of the main part.

FIG. 3 is a configuration diagram of another embodiment.

[Explanation of symbols]

 4 Adsorption Column 7 Liquid Nitrogen Storage Tank 9 Main Pipe 10 Fractionation Column 41 Extraction Pipe 11 Oxygen Adsorption Column 15 Decompressor 15a Condenser 15b First Reflux Liquid Pipe 15c Second Reflux Liquid Pipe 34 Expansion Turbine 38 Heat Exchanger 40 Introductory pipe

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 equipment 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 take out only nitrogen from the upper side as gas In, a condenser built-in type condenser provided in the upper part of the rectification tower, and a liquid air introduction pipe for guiding the stored liquid air at the bottom of the rectification tower into the condenser as cold for cooling the condenser. When,
A discharge pipe for discharging the vaporized liquid air generated in the dephlegmator to the outside, and an expander for generating cold heat by using the vaporized liquid air of the discharge pipe and sending the generated cold heat to the heat exchange means for cooling. A first reflux liquid pipe that guides a part of the nitrogen gas generated in the rectification column into the condenser, and a second reflux liquid pipe that returns the liquefied nitrogen generated in the condenser into the rectification column as reflux liquid. A reflux liquid pipe, liquid nitrogen storage means for receiving and supplying liquid nitrogen from outside the apparatus, and liquid nitrogen in the liquid nitrogen storage means is continuously cooled in the rectification column as chill for compressed air liquefaction. An apparatus for producing high-purity nitrogen gas, which is equipped with a lead-in path for leading.