JPH0611255A - High purity nitrogen gas preparing device - Google Patents

Abstract

PURPOSE:To make it possible to cope with the variation of a demand quantity quickly by a method wherein an expansion turbine and the feeding of liquid nitrogen from a liquid nitrogen storage means are operated in parallel, and the liquid nitrogen feeding quantity from the liquid nitrogen storage means is controlled, and the liquid level of liquid air in a dephlegmeter is controlled to be uniform. CONSTITUTION:A dephlegmeter 15 in which a condenser is built in is provided at an upper part of a fractionator 10, and one part of gaseous nitrogen in the fractionator 10 is always guided into the condenser to liquefy the gaseous nitrogen, and after liquefied nitrogen is accumulated to a specified quantity, the liquid nitrogen which is formed after that is always returned to the fractionator 10 as a circulating liquid. That is, a specified quantity of product gaseous nitrogen is prepared by always operating an expansion turbine, and in addition, a fluctuated portion of demand is compensated by liquid nitrogen from a liquid nitrogen storage tank 7. Even when a variation is generated in the demand quantity of the product gaseous nitrogen, the opening degree of a valve is controlled by a control means, and the feeding quantity of liquid nitrogen to the fractionator 10 is controlled, and thus, the liquid level of liquid air in the dephlegmeter 15 is controlled to be uniform, and therefore, the title device can cope with the variation of demand quantity quickly.

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 Nitrogen is generally produced by a cryogenic liquefaction separator. This type of nitrogen producing apparatus uses an expansion turbine for cooling a refrigerant of a heat exchanger for exchanging heat with compressed air compressed by a compressor, as disclosed in, for example, Japanese Patent Publication No. 52-41232. This is driven by the pressure of the waste gas evaporated from the liquid air that accumulates in the rectification column (nitrogen with a low boiling point is taken out as gas by deep-chill liquefaction separation, and the rest is accumulated as oxygen-rich liquid air). It has become.

[0003]

However, the expansion turbine has an extremely high rotational speed (tens of thousands of revolutions / minute), and it is difficult to perform a quick follow-up operation with respect to a load change. That is, even if the amount of cold gas generated by the expansion turbine is changed by controlling the flow rate of the waste gas flowing in the flow path of the expansion turbine with the control valve, the amount of cold gas generated by the expansion turbine can be changed. Since it takes time to change, it is not possible to respond promptly (a delay of several tens of minutes occurs).

On the other hand, instead of using the cold generated by the expansion turbine as described above, an apparatus for introducing liquid nitrogen stored in the liquid nitrogen tank into the rectification column as cold instead of the cold is proposed. No. 50-47882). However, this device cannot be equipped with an adjusting mechanism for adjusting the supply amount of cold liquid nitrogen according to the fluctuation of the demand for product nitrogen gas. It has the drawback that it cannot respond to fluctuations in gas demand at all.

Therefore, it is desired to provide a nitrogen gas production apparatus capable of promptly responding to fluctuations in demand.

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.

[0007]

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 introduction path for introducing liquid nitrogen in the means into the rectification column as cold for liquefying compressed air, and the dephlegmator by controlling the supply amount of the liquid nitrogen from the liquid nitrogen storage means to the rectification column. Control means for controlling the liquid surface of the liquid air in the inside of the rectification tower to a constant level, and nitrogen which is taken out as a gas from the rectification tower and the liquid nitrogen vaporized after finishing the operation as a cold source in the rectification tower to the heat exchange means. Compression through it A configuration that includes a nitrogen gas takeout path for a product nitrogen gas increased in temperature by the gas and heat exchange.

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

[0009]

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
Is filled with molecular sieve and has an action of adsorbing and removing H ₂ O and CO ₂ in the air compressed by the air compressor 1. 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 so as to maintain a constant level, thereby controlling 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 the 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,
(Union Carbide Co., Ltd.) is an adsorption column for adsorbing impurities such as oxygen, which is provided in the middle of the extraction pipe 41 and selectively adsorbs and removes 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 for sending the vaporized liquid air (waste gas) 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 in the arrow direction. The compressed air sent through the route B and sent into the heat exchanger 38 is cooled to an ultralow temperature and sent to the rectification column 10.

This apparatus is used as a 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.

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, particularly the significant fluctuation of the important amount. You will be able to respond quickly to. That is, the expansion turbine is operated in a steady state to produce a predetermined amount of product nitrogen gas, and the fluctuation in demand is supplemented by the liquid nitrogen from the liquid nitrogen storage tank to change the rotation speed of the expansion turbine. Instead, 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, 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. In particular, this high-purity nitrogen gas production apparatus has a condenser 15a built-in partial condenser 1 above the rectification tower 10.
5, a part of the nitrogen gas in the rectification column 10 is always guided into the condenser 15a to be liquefied. Therefore, after a predetermined amount of liquefied nitrogen is accumulated in the condenser 15a, liquefaction to be generated thereafter. Nitrogen always returns to the rectification column 10 as a reflux liquid. Therefore, variations in product purity due to the intermittent supply of the reflux liquid flowing down from the condenser 15a (the interruption of the flow-down 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, with this device,
Even if the demand amount of the product nitrogen gas fluctuates, a control unit such as the liquid level gauge 23 controls the opening degree of the valve 24 and the like to control the rectification tower 10.
Since the liquid level of the liquid air in the dephlegmator 15 is controlled to be constant by controlling the supply amount of the liquid nitrogen with respect to, it is possible to quickly respond to the fluctuation of the demand amount, and at this time also for the reason described above. No variation in purity occurs. 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. The amount of liquid nitrogen stored in the bottom of the rectification column increases due to the increase in the supply amount of liquid nitrogen, and accordingly the dephlegmator 15
When the liquid level in the interior is restored, the liquid level gauge 23 is used to
The supply amount of liquid nitrogen to the 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 of not hindering the supply of the product nitrogen gas even when the air compression system line fails.

[0014]

The high-purity nitrogen gas producing apparatus of the present invention is
Since not only the cold generated by the expansion turbine but also the liquid nitrogen in the liquid nitrogen storage tank is used as the cold, it becomes possible to promptly respond to the fluctuation of the demand amount of the product nitrogen gas, particularly the large fluctuation of the demand 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 rotating device, 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. This invention uses an expansion turbine that causes such a time delay and the supply of liquid nitrogen from a liquid nitrogen storage tank in combination, and rotates the expansion turbine at a constant speed to generate a certain amount of refrigeration.
Liquid nitrogen is used to cover the rest of the cold (including fluctuations) so that fluctuations in demand can be dealt with quickly. 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 cheap), 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 Capable of responding to significant fluctuations in volume,
Moreover, it becomes possible to respond to fluctuations in demand for product nitrogen gas. Particularly, in the high-purity nitrogen gas production apparatus of the present invention, regarding the adjustment of the supply amount of liquid nitrogen based on the fluctuation of the demand amount of product nitrogen gas, the control unit supplies the liquid nitrogen from the liquid nitrogen storage unit to the rectification column. Since the liquid level of the dephlegmator is controlled to be constant by controlling the amount, it is possible to respond to demand fluctuations very quickly and precisely, and there is no variation in the purity of the 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 FIG.

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, a liquid nitrogen storage means for receiving and storing liquid nitrogen supplied from the outside of the apparatus, and 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 a control means for controlling the liquid level of the liquid air in the dephlegmator to a constant level by controlling the supply amount of liquid nitrogen from the liquid nitrogen storage means to the rectification tower, and gas from the rectification tower. In the rectification tower and nitrogen taken out as The liquid nitrogen that has finished its function as a cold source has been provided with a nitrogen gas take-out path for raising the temperature of the vaporized liquid nitrogen by exchanging heat with the compressed air passing through the inside through the heat exchanging means. Characteristic high-purity nitrogen gas production equipment.