JPH0882476A - Apparatus for producing high-purity nitrogen gas - Google Patents

Abstract

PURPOSE: To compensate the inadequacy of the performance of an expansion turbine in following up the fluctuations of the demand with injection of liquid nitrogen relating to an apparatus for producing nitrogen gas of superhigh purity by low-temperature liquefaction-separation of air. CONSTITUTION: To a rectifying column 15a with a dephlegmator 15 an expansion turbine and also a liquid-nitrogen storage tank are connected. The air supplied as raw material is cooled constantly by means of cold evolved by the expansion turbine, and, for a deficiency of the cold, liquid nitrogen is supplied from the liquid-nitrogen storage tank to the rectifying column 15a under the control of a liquid-level instrument 23.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD 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 has an expansion turbine for cooling a refrigerant of a heat exchanger for exchanging heat with compressed air compressed by a compressor, as disclosed in Japanese Patent Publication No. 52-41232. Use it by driving it with the pressure of the gas evaporated from the liquid air that accumulates in the rectification column (nitrogen with a low boiling point is taken out as a gas by cryogenic liquefaction separation, and the rest is stored as oxygen-rich liquid air). It has become.

[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 for removing impure oxygen, (1) Pt
A method of using a catalyst to add a trace amount of hydrogen to nitrogen gas and reacting it with impure oxygen in an atmosphere at a temperature of about 200 ° C. to remove it as water, and (2) using a Ni catalyst to obtain impurities in nitrogen gas Oxygen in the atmosphere of about 200 ℃ N
There is a method of contacting with an i-catalyst to cause the following reaction and removal.

[0006]

[Chemical formula 1] Ni + 1 / 2O ₂ → NiO

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. In addition, the method (1) requires high precision in adjusting the amount of hydrogen added, and if hydrogen is not added in an amount just to react with the amount of impure oxygen, oxygen remains or is added. Since hydrogen remains and becomes an impurity, there is a problem that skill is required for the operation. Further, in the above method (2), it is necessary to regenerate NiO generated by the reaction with impure oxygen (reaction shown below), which requires an H ₂ gas facility for regeneration, resulting in an increase in purification cost. Was there.

[0008]

[Chemical formula 2] NiO + H ₂ → Ni + H ₂ O

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 Expander for generating cold heat and sending the generated cold heat to the heat exchange means for cooling, liquid nitrogen storage means for receiving and storing liquid nitrogen from outside the device, and liquid nitrogen in the liquid nitrogen storage means. Is introduced into the rectification column as cold for liquefaction of compressed air, nitrogen taken out as a gas from the rectification column and the liquid nitrogen vaporized after finishing the action as a cold source in the rectification column. A nitrogen gas take-out path for raising the temperature of the product by passing it through the heat exchange means and exchanging heat with the compressed air passing through the inside to obtain product nitrogen gas is provided.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION That is, the high-purity nitrogen gas production apparatus of the present invention is not limited to the cold generated by the expansion turbine,
Since liquid nitrogen in the liquid nitrogen storage tank is also used as cold, it becomes possible to quickly respond to fluctuations in the demand amount of the product nitrogen gas, particularly large fluctuations in the important amount. That is, the expansion turbine is operated in a steady state so that a predetermined amount of product nitrogen gas is constantly produced, and the fluctuation of demand is compensated by the liquid nitrogen from the liquid nitrogen storage tank. It will be possible to quickly respond to fluctuations in demand without changing. More specifically, the expansion turbine is a high-speed rotator, and it is difficult to quickly change the amount of waste gas supplied to the expansion turbine in accordance with the change in the amount of product nitrogen gas taken out, and a time delay is always caused.
The present invention uses the expansion turbine that causes such a time delay and the supply of liquid nitrogen from the liquid nitrogen storage tank together to rotate the expansion turbine at a constant speed to generate a certain amount of refrigeration, and the remainder of the refrigeration. By supplying liquid nitrogen (including fluctuations) with liquid nitrogen, it is possible to quickly respond to fluctuations in demand. In this case, since the liquid nitrogen from the liquid nitrogen storage tank is liquid, the supply amount can be adjusted quickly and precisely, and since the liquid nitrogen is directly supplied to the rectification column, the supply amount can be adjusted. The effect will appear quickly. The device of the present invention is particularly effective in the case where the fluctuations in the demand amount of the product nitrogen gas between the daytime and the nighttime are significantly different (there are many daytime periods). In other words, the expansion turbine is used to cover all of the cold at night (late-night power is inexpensive), and the lack of cold during the day is supplemented with liquid nitrogen from the liquid nitrogen storage tank, so that the demand for day and night is increased. It will be possible to cope with significant fluctuations in the quantity, and also to cope with fluctuations in the demand for product nitrogen gas.

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing 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. The adsorption cylinder 4 is filled with a molecular sieve and has a function of adsorbing and removing H ₂ O and CO ₂ in the air compressed by the air compressor 1. 13 is H ₂ O, C
A compressed air supply pipe for sending compressed air in which O ₂ is adsorbed and removed. 38 is a heat exchanger, and the adsorption cylinder 4 causes H ₂
Compressed air from which O and CO ₂ have been adsorbed and removed is fed. Reference numeral 10 is a rectification column, and as shown in FIG. 2, the column top is equipped with a condenser 15a having a built-in condenser 15a.
8 (FIG. 1), the compressed air that has been cooled to an ultra-low temperature and sent through the pipe 16 is further cooled, and a part of it is liquefied and stored as liquid air 36 in the bottom portion, and only nitrogen in a gas state is stored in the upper ceiling portion. It has become. In FIG. 1, 7 is a liquid nitrogen storage tank that receives liquid nitrogen supplied from outside the device and stores it, and liquid nitrogen inside (high purity product)
Is sent to the upper side of the rectification tower 10 via the introduction path pipe 40, and is used as a cold source of the compressed air supplied into the rectification tower 10. The rectification tower 10 will now be described in more detail. As shown in FIG.
0 is equipped with a partial condenser 15 and a condenser 15a in the partial condenser 15 has a part of nitrogen gas accumulated in the upper portion of the rectification column 10 through a first reflux liquid pipe 15b. Sent in. The inside of the partial condenser 15 is in a reduced pressure state as compared with the inside of the rectification tower 10, and the stored liquid air (N ₂ ; 50 to 70%, O ₂ ; 30 to 50%) 36 at the bottom of the rectification tower 10 is provided. Is sent through a pipe 37 with an expansion valve 18a, vaporizes and cools 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. Reference numeral 23 is a liquid level gauge, and a dephlegmator 15
The valve 24 is controlled according to the liquid level of the liquid air in the liquid nitrogen storage tank 7 so that the liquid surface of the liquid nitrogen maintains a constant level, and the supply amount of the liquid nitrogen from the liquid nitrogen storage tank 7 is controlled. The liquid nitrogen produced in the condenser 15a in the dephlegmator 15 is supplied to the upper part of the rectification column 10 through the second reflux liquid pipe 15c and is supplied from the liquid nitrogen storage tank 7 to the liquid nitrogen storage tank 7. Nitrogen is supplied through an inlet pipe 40, and these flow down through the liquid nitrogen reservoir 39 in the rectification column 10 and come into countercurrent contact with the compressed air rising from the bottom of the rectification column 10 to cool it. It is designed to liquefy a part of it. In this process, the high boiling point component (oxygen) in the compressed air is liquefied and accumulated at the bottom of the rectification column 10,
Nitrogen gas having a low boiling point is accumulated in the upper part of the rectification column 10. 41
Is an extraction pipe for taking out the nitrogen gas accumulated in the upper ceiling part of the rectification tower 10 as product nitrogen gas, guiding the ultra-low temperature nitrogen gas into the heat exchanger 38, and exchanging heat with the compressed air fed thereinto at room temperature. It feeds into the main pipe 9. Reference numeral 11 denotes an adsorption column for adsorbing impurities such as oxygen filled with synthetic zeolite 3A, 4A or 5A (Molecular Sieves 3A, 4A, 5A, manufactured by Union Carbide) having a pore size of 3Å, 4Å or 5Å, Oxygen and carbon monoxide in the ultra-low temperature nitrogen gas provided in the middle of the extraction pipe 41 are selectively adsorbed and removed. Also,
In place of the above synthetic zeolites 3A, 4A and 5A, the above U
It is also possible to use synthetic zeolite 13X manufactured by Company C. 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, the adsorption cylinder 1
Since the amounts of impure oxygen and carbon monoxide in the ultra-low temperature nitrogen gas introduced into 1 are already at low levels after passing through the rectification column 10, the amounts of oxygen and carbon monoxide to be adsorbed are very small. Therefore, only one adsorption cylinder 11 is sufficient, and the zeolite can be regenerated once a year. In addition, at the uppermost part in the rectification tower 10, together with nitrogen gas, He (-269 ° C.) and H ₂ (-25
(3 ° C) is likely to accumulate, so the extraction pipe 41 is
0, the opening is much lower than the top, and He, H ₂
Only pure nitrogen gas that does not exist is taken out as product nitrogen gas. Reference numeral 35 is a discharge pipe for sending the vaporized liquid air in the dephlegmator 15 to the drive unit of the expansion turbine 34, and the expansion turbine 34 is driven by the pressure of the vaporized liquid air.
(Refer to FIG. 1), the refrigerant is sent through the path indicated by arrow B, and the compressed air sent into the heat exchanger 38 is cooled to an ultralow temperature and sent to the rectification column 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.
Product nitrogen gas and path from expansion turbine 34 to arrow B
Heat exchanger 3 cooled by the refrigerant sent in
It is sent to 8 and cooled to ultra low temperature, and in that state, the rectification tower 10
Put in the lower part of. Then, this input compressed air is
Fractionation tower 1 from body nitrogen storage tank 7 through introduction pipe 40
Liquid nitrogen and liquid nitrogen reservoir 39 sent into 0
Contact with overflowing liquid nitrogen to cool and liquefy a part of it
It is stored as liquid air 36 at the bottom of the rectification column 10. This
The difference between the boiling points of nitrogen and oxygen (boiling point of oxygen-18
3 ℃, boiling point of nitrogen-196 ℃)
Oxygen, which is the boiling point component, is liquefied and nitrogen remains as a gas.
Then, take out the nitrogen remaining in this gas as pipe 41.
And send it to the heat exchanger 38, and raise it to near room temperature.
It is heated and sent out as product nitrogen gas from the main pipe 9.
You On the other hand, the liquid air 36 accumulated at the bottom of the rectification tower 10
Then, this is sent into the dephlegmator 15 and the condenser 15a is
Allow to cool. This cooling causes condensation from the upper part of the rectification tower 10.
The nitrogen gas sent to the compressor 15a is liquefied and the rectification tower 10
It becomes the recirculating liquid for use, and is refined through the second recirculating liquid pipe 15c.
Return to distillation tower 10. Then, cooling of the condenser 15a is completed.
The liquid air 36 is vaporized and released by the discharge pipe 35.
In the air after it is sent to the 38 and cools the heat exchanger 38.
Is released to. In addition, from the liquid nitrogen storage tank 7 to the introduction pipe
Liquid nitrogen sent into the rectification column 10 via 40
Acts as a cold source for the liquefaction of compressed air, which itself
As a part of the product nitrogen gas that is vaporized and taken out from the pipe 41
Taken out.

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 the cold, fluctuations in the demand amount of the product nitrogen gas, particularly a significantly important amount. It will be possible to quickly respond to changes in. That is, the expansion turbine 34 is steadily operated to produce a predetermined amount of product nitrogen gas, and the fluctuation of demand is supplemented by the liquid nitrogen from the liquid nitrogen storage tank 7, whereby the rotation speed of the expansion turbine 34, etc. It will be possible to quickly respond to fluctuations in demand without changing. More specifically, since it takes a long time to change the rotation speed of the expansion turbine 34, the supply amount of the liquid nitrogen from the liquid nitrogen storage tank 7 can be changed quickly.
It will be possible to quickly respond to fluctuations in demand. 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 compensated by the liquid nitrogen from the liquid nitrogen storage tank 7. 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. In particular,
This high-purity nitrogen gas producing apparatus is provided with a condenser 15a built-in type partial condenser 15 in the upper part of the rectification column 10, and the condenser 15
Since a part of the nitrogen gas in the rectification column 10 is always guided into the inside of a to be liquefied, after a predetermined amount of the liquefied nitrogen is accumulated in the condenser 15a, the liquefied nitrogen generated thereafter is always rectified as a reflux liquid. It comes to return to the distillation column 10. Therefore, variations in product purity due to the intermittent supply of the reflux liquid from the condenser 15a are interrupted (the interruption of the flow of the reflux liquid causes the liquid to disappear in the upper rectification shelf, leading to a gas blow-through phenomenon, which lowers the product purity. The product nitrogen gas having a stable purity can always be supplied without causing (returning to a certain purity) when restarted. Moreover, in this device, even if the demand amount of the product nitrogen gas fluctuates, the control means such as the liquid level gauge 23 is used for the valve 2
Since the liquid level of the liquid air in the dephlegmator 15 is controlled to be constant by controlling the opening degree of 4 and the supply amount of liquid nitrogen to the rectification column 10, it is possible to quickly respond to the fluctuation of the demand amount. At this time, the purity does not fluctuate due to 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 liquid level gauge 23 is activated to increase the supply amount of liquid nitrogen to the rectification column 10, and by vaporizing the liquid nitrogen gas, the product nitrogen gas is rapidly produced and the demand amount is quickly increased. When the amount of liquid nitrogen stored increases at the bottom of the rectification column 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 liquid nitrogen to the rectification column 10. Is appropriately 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. The nitrogen gas is supplied to the main pipe 9 so that the supply of nitrogen gas is not interrupted. Further, the main pipe 9 is provided with an impurity analyzer 27 and valves 28, 29 to analyze the purity of the product nitrogen gas sent to the main pipe 9, and when the purity is low, the valves 29, 2 are used.
8 is operated to let the product nitrogen gas escape to the outside as shown by arrow A. Since the other parts are substantially the same as those of the apparatus of FIG. 1, 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]

As described above, since the high-purity nitrogen gas producing apparatus of the present invention uses not only the cold generated by the expansion turbine but also the liquid nitrogen in the liquid nitrogen storage tank as the cold, the demand amount of the product nitrogen gas can be reduced. You will be able to respond quickly to changes, especially to significant changes in significant amounts. That is, the expansion turbine is operated in a steady state so that a predetermined amount of product nitrogen gas is constantly produced, and the fluctuation of demand is compensated by the liquid nitrogen from the liquid nitrogen storage tank. It will be possible to quickly respond to fluctuations in demand without changing. More specifically, the expansion turbine is a high-speed rotator, and it is difficult to quickly change the amount of waste gas supplied to the expansion turbine in accordance with the change in the amount of product nitrogen gas taken out, and a time delay is always caused. The present invention uses the expansion turbine that causes such a time delay and the supply of liquid nitrogen from the liquid nitrogen storage tank together to rotate the expansion turbine at a constant speed to generate a certain amount of refrigeration, and the remainder of the refrigeration. By supplying liquid nitrogen (including fluctuations) with liquid nitrogen, it is possible to quickly respond to fluctuations in demand. In this case, since the liquid nitrogen from the liquid nitrogen storage tank is liquid, the supply amount can be adjusted quickly and precisely, and since the liquid nitrogen is directly supplied to the rectification column, the supply amount can be adjusted. The effect will appear quickly. The present invention is particularly effective in the case where the fluctuations in the demand amount of the product nitrogen gas between the daytime and the nighttime are significantly different (there are many daytime periods).
In other words, the expansion turbine is used to cover all of the cold at night (late-night power is inexpensive), and the lack of cold during the day is supplemented with liquid nitrogen from the liquid nitrogen storage tank, so that the demand for day and night is increased. It will be possible to cope with significant fluctuations in the quantity, and also to cope with fluctuations in the demand for product nitrogen gas.

[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 above embodiment.

FIG. 3 is a configuration diagram of another embodiment of the present invention.

[Description of sign]

 4 Adsorption Column 7 Liquid Nitrogen Storage Tank 9 Main Pipe 10 Fractionation Column 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 Inlet Pipe 41 Extraction 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. Liquid nitrogen storage means for receiving and storing liquid nitrogen supplied from outside the apparatus, an introduction path for guiding the liquid nitrogen in the liquid nitrogen storage means into the rectification column as refrigeration for liquefying compressed air, and the rectification Nitrogen taken out as a gas from the tower and the liquid nitrogen vaporized after finishing the action as a cold source in the rectification tower are heat-exchanged with the compressed air passing through the heat exchange means to raise the temperature. A high-purity nitrogen gas production apparatus, comprising: a nitrogen gas extraction path for supplying nitrogen gas.