JPS6217149B2 - - Google Patents

Description

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

[Conventional technology]

The electronic industry uses extremely large amounts of nitrogen gas. For this reason, it is desired to supply nitrogen gas at low cost, and in order to meet this demand, the PSA system has been introduced, and nitrogen gas has been produced and supplied using this method. Figure 1 shows a nitrogen gas production device using this PSA method. In the figure, 1 is an air intake port, 2 is an air compressor, 3 is an aftercooler, 3a is a cooling water supply path, and 4 is an oil-water separator. 5 is a first adsorption tank, 6 is a second adsorption tank, V ₁ and V ₂ are air-operated valves, and air compressed by the air compressor 2 is sent into the adsorption tank 6 by valve action. V ₃ and V ₄ are vacuum valves, and the interior of the adsorption tank 6 is brought into a vacuum state by the action of the vacuum pump 6a. 6b is a cooling pipe that supplies cooling water to the vacuum pump 6a, 6c is a silencer, and 6d is an exhaust pipe thereof. 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 through a pipe 8. 7a is a product nitrogen gas extraction pipe, 7b is an impurity analyzer, and 7c is a flow meter.

This continuous nitrogen gas production device compresses air with an air compressor 2, cools the compressed air with an aftercooler 3 attached to the air compressor 2, removes condensed water with a separator 4, and It is sent to the adsorption tanks 5 and 6 via the operating valve V ₁ or V ₂ . The two adsorption tanks 5 and 6 each have a built-in carbon molecular sieve for oxygen adsorption.
Compressed air is alternately fed into these adsorption tanks 5 and 6 every minute by a pressure swing system. In this case, the adsorption tanks 5 and 6 to which compressed air is not fed are brought into a vacuum state by the action of the vacuum pump 6a. That is, the air compressed by the air compressor 2 enters one of the adsorption tanks 5, and the carbon molecular sieve adsorbs and removes the oxygen therein, and converts it into nitrogen gas, which passes through the valves _V5 ,
It is sent into the product tank 7 through V ₇ and V ₉ , and is passed through the pipe 7a.
taken from. At this time, the other adsorption tank 6 is
Air from the air compressor 2 is shut off by closing the valve _V2 , and the interior is evacuated by the vacuum pump _6a by opening the valve V4. As a result, the oxygen adsorbed on the carbon molecular sieve is removed by suction, and the carbon molecular sieve is regenerated. In this way, nitrogen gas is alternately sent from the adsorption tanks 5 and 6 to the product tank 7, and product nitrogen gas is continuously obtained.

[Problem that the invention seeks to solve]

The above-described continuous nitrogen gas production apparatus produces nitrogen gas by utilizing the property of the carbon molecular sieve that selectively adsorbs oxygen, and therefore can obtain nitrogen gas at low cost. However, as mentioned above, compressed air is sent alternately to the two adsorption tanks 5 and 6 every minute, and at the same time, the inside of the other adsorption tank is vacuumed, which requires a large number of valves. It has the drawback of being complicated to operate and prone to frequent failures. Therefore, the reality is that two sets of two adsorption tanks 5 and 6 must be provided, and one set must be kept as a spare. Therefore, it also has the disadvantage of high equipment costs.

On the other hand, conventional cryogenic liquefaction nitrogen gas production equipment uses an expansion turbine to cool the heat exchanger for cooling the compressed raw air compressed by the compressor, and uses the liquid accumulated in the rectification tower to cool the compressed raw air. It is powered by the pressure of gas evaporated from air (low boiling point nitrogen is extracted as a gas through cryogenic liquefaction separation, and the remainder accumulates as oxygen-rich liquid air). However, the rotational speed of expansion turbines is extremely high (tens of thousands of rotations per minute), making it difficult to follow load fluctuations (fluctuations in the amount of product nitrogen taken out (demand amount)). It has the disadvantage that it varies. Furthermore, since this device rotates at high speed, it requires high precision in its mechanical structure, is expensive, and has the disadvantage that specially trained personnel are required due to the complicated mechanism. That is, since the expansion turbine has a high-speed rotating section, the above-mentioned problems arise, and there has been a strong desire to eliminate the expansion turbine having such a high-speed rotating section.

[Means for solving problems]

This invention provides air compression means for compressing air taken in from the outside, removal means for removing carbon dioxide and moisture from the compressed air compressed by the air compression means, and compressed air that has passed through the removal means. A nitrogen gas production system equipped with a heat exchange means that cools air to an ultra-low temperature, and a rectification column that liquefies a portion of the compressed air cooled to an ultra-low temperature by this heat exchange means, stores it inside, and extracts only nitrogen as a gas from the upper side. The apparatus includes a liquid nitrogen storage means for receiving and storing liquid nitrogen from outside the apparatus, and a liquid nitrogen storage means for storing the liquid nitrogen supplied from outside the apparatus, and a liquid nitrogen storage means for converting the liquid nitrogen in the liquid nitrogen storage means into cold heat generated from a cold heat generation expander to generate cold heat for liquefying compressed air. Nitrogen gas, which is taken out as a gas from the rectification column, passes through the heat exchange means and exchanges heat with the compressed air to raise the temperature and convert it into product nitrogen gas. The gist is a continuous nitrogen gas production device equipped with a nitrogen gas extraction path.

That is, the continuous nitrogen gas production apparatus of the present invention uses the heat of vaporization of liquid nitrogen to cool the compressed air sent to the heat exchange means, and liquefies and separates a part of the compressed air in the rectification column to produce nitrogen. Since it is retained as a gas and taken out as manufactured nitrogen gas, an expansion turbine is not required, and the disadvantages such as variation in purity caused by the expansion turbine at the time of load fluctuations can be avoided, and nitrogen gas can be obtained at low cost. You will be able to do this. Also, unlike the PSA system, it does not require a large number of valves, so there are fewer failures.

Next, the present invention will be explained in detail based on examples.

〔Example〕

FIG. 2 is a block diagram of an embodiment of the present invention.
In the figure, 9 is an air compressor, 10 is a drain separator, 11 is a fluorocarbon cooler, and 12 is a set of two adsorption cylinders. The adsorption cylinder 12 is filled with a molecular sieve and functions to adsorb and remove H ₂ O and CO ₂ from the air compressed by the air compressor 9. 13 is a first heat exchanger, into which compressed air from which H ₂ O and CO ₂ have been adsorbed and removed by the adsorption column 12 is sent. 14 is a second heat exchanger, into which the compressed air that has passed through the first heat exchanger 13 is sent. Reference numeral 15 denotes a liquid nitrogen storage tank, in which the liquid nitrogen inside is sent to the second heat exchanger 14 through an inlet pipe 16, where it is exchanged with the compressed air sent into the second heat exchanger 14, and then into the second heat exchanger 14. 1 heat exchanger 1
3, where it exchanges heat with the compressed air sent into the first heat exchanger 13 and is vaporized. The liquid nitrogen vaporized by the first heat exchanger 13 is discharged into the atmosphere through a discharge pipe 16a. A pressure control valve is provided at the outlet of the discharge pipe 16a, and the inlet pipe 16 and the discharge pipe 16
Control the amount of liquid nitrogen in a.

The rectification column 18 takes in compressed air cooled to an ultra-low temperature (approximately -170°C) from the lower part through the first and second heat exchangers 13 and 14, and extracts oxygen in the compressed air (boiling point -183°C). liquefies nitrogen (boiling point -196
°C) is discharged from the top.
18a is a first guide pipe that guides the ultra-low temperature nitrogen gas discharged from the upper part of the rectification column 18 to the second and first heat exchangers 14, 13, and exchanges heat with the compressed air sent there. The product gas is brought to room temperature and sent to the main pipe 17 as a product gas. 18
b is the rectifier pipe, and the liquid air accumulated at the bottom of the rectifier 18 (liquid nitrogen is also mixed in)
The cooling pipe 1 installed at the top of the rectification column 18
8c to cool the pipe 18c. Reference numeral 18d designates a second guide pipe that sends the liquid air that has been cooled in the pipe to the second and first heat exchangers 14 and 13. second and first
Heat exchange between heat exchangers 14 and 13 (heat exchanger 14,
The liquid air that has finished cooling the compressed air in the first heat exchanger 13 is vaporized and discharged into the atmosphere from the discharge pipe 13a of the first heat exchanger 13 as shown by the arrow. Reference numeral 19 denotes a backup system line, and when the air compression system line breaks down, the liquid nitrogen in the liquid nitrogen storage tank 15 is sent to the evaporator 20 where it is evaporated and sent to the main pipe 17 to supply nitrogen gas. This is to ensure that there is no interruption.

This device produces product nitrogen gas in the following manner. That is, air is compressed by an air compressor 9, moisture in the compressed air is removed by a drain separator 10, and cooled by a fluorocarbon cooler 11. In this state, the air is sent to an adsorption column 12 filled with molecular sieve. , H ₂ O in air and
Adsorbs and removes CO ₂ . 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 ultra-low temperature, and then sent into the rectification column 18 . Then, the oxygen in the air is liquefied by utilizing the difference in boiling point between nitrogen and oxygen (the boiling point of oxygen is -183°C, the boiling point of nitrogen is -196°C), and the nitrogen is taken out as a gas and transferred to the first heat exchanger 13. The main pipe 1 is heated to near normal temperature.
7 as a product nitrogen gas. in this case,
The liquid nitrogen in the liquid nitrogen storage tank 15 acts as a cold source for the first and second heat exchangers 13 and 14,
The gas itself is vaporized and discharged into the atmosphere from the discharge pipe 16a.

As described above, according to this nitrogen gas continuous production device, compressed air is cooled using the heat of vaporization of liquid nitrogen, and is sent to the rectification column 18 to separate oxygen and other substances to extract only nitrogen. Since the nitrogen gas is produced as a product, the above-mentioned disadvantages caused by the expansion turbine do not occur at all, and highly purified nitrogen gas can be obtained at an extremely low cost. In particular, this device can only control heat transfer since the inlet pipe 16 from the liquid nitrogen storage tank 15 is independent from the rectifier line. Therefore, it has the advantage of being able to operate without considering pressure fluctuations within the rectification column 18.

By setting the rectification column 18 with high precision, the above apparatus can obtain nitrogen gas with a purity of 99.999% without variation in purity. In contrast, with PSA nitrogen gas production equipment, at most
Only 99.3% purity can be obtained, and in cryogenic liquefaction separators that use expansion turbines, the purity varies when the load fluctuates. In addition, when the demand increases significantly or when product nitrogen gas cannot be obtained from the rectifier 18 due to a malfunction in the rectifier line, the backup system line 1
9 is activated to directly vaporize the liquid nitrogen in the liquid nitrogen storage tank 15 in the evaporator 20 and flow it into the main pipe 17 as product nitrogen gas. This prevents generation of nitrogen gas and interruption of the supply of product nitrogen gas, and allows stable supply of product nitrogen gas at all times. In addition, this device uses one liquid nitrogen storage tank 15 as a storage tank for both the rectification column line and the backup system line, so it is possible to significantly reduce equipment costs and reduce the installation space of the liquid nitrogen storage tank. I can,
The entire device can be made more compact.

As described above, according to the continuous nitrogen gas production apparatus of the present invention, highly purified nitrogen gas can be obtained in a stable state, so that it can be directly used in the electronic industry. Since this gas does not contain carbon dioxide (it is removed within the production equipment), there is no need to separately equip an adsorption tank for carbon dioxide. Furthermore, a large amount of nitrogen gas can be obtained by simply supplying a small amount of liquid nitrogen. That is, according to the nitrogen gas continuous production apparatus of the present invention,
By sending 100 Nm ³ (gas equivalent) of liquid nitrogen from the liquid nitrogen storage tank 15 to the heat exchangers 14 and 13, product nitrogen gas of 1000 Nm ³ can be obtained. In this way, with this production equipment, by supplying only a small amount of liquid nitrogen, 10 times as much product nitrogen gas can be obtained. Therefore,
Extremely cheap nitrogen gas can now be obtained. In addition, compared to nitrogen gas production equipment using the PSA method or the conventional cryogenic liquefaction separation method that uses an expansion turbine, the equipment is simple and inexpensive, and it does not require a large number of valves. High reliability. It also eliminates the need for special personnel due to the expansion turbine.

Note that although a backup system line is provided in the above embodiment, this need not necessarily be provided.

〔Effect of the invention〕

As described above, the nitrogen gas continuous production apparatus of the present invention does not use an expansion turbine, but instead uses a liquid nitrogen storage means such as a liquid nitrogen storage tank that does not have any rotating parts, so the apparatus as a whole has no rotating parts. No malfunctions occur at all. Additionally, unlike the PSA system, it does not have a large number of valves, so valve-related failures do not occur. Moreover, since the expansion turbine is a high-speed rotating device, it is difficult to perform operation that closely follows load fluctuations (changes in the amount of product nitrogen gas taken out).However, the device of this invention uses a liquid nitrogen storage tank instead of the expansion turbine. Since liquid nitrogen, whose supply amount can be finely adjusted, is used as a cold source, it is possible to closely follow load fluctuations, and it becomes possible to produce nitrogen gas with stable and extremely high purity. In particular, the device of this invention
Liquid nitrogen is supplied from the liquid nitrogen storage means to the heat exchange means, and since this introduction path is independent from the rectification column line, it is possible to control only heat transfer, and pressure fluctuations within the rectification column can be controlled. It has the advantage of being able to be driven without having to take this into account. Furthermore, since the continuous nitrogen gas production apparatus of the present invention can easily be equipped with a backup line that is activated when the apparatus malfunctions, this can also contribute to eliminating the need for backup equipment.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional example, and FIG. 2 is a block diagram of an embodiment of the present invention. 9... Air compressor, 12... Adsorption cylinder, 13...
First heat exchanger, 14...Second heat exchanger, 15
...Liquid nitrogen storage tank, 18...Rectification tower.

Claims (1)

[Claims] 1. Air compression means for compressing air taken in from the outside, removal means for removing carbon dioxide and moisture from the compressed air compressed by this air compression means, and cooling the compressed air that has passed through this removal means to an ultra-low temperature. In a nitrogen gas production device equipped with a cooling heat exchange means and a rectification column that liquefies a part of the compressed air cooled to an ultra-low temperature by the heat exchange means and stores it inside and extracts only nitrogen as a gas from the upper side, A liquid nitrogen storage means that receives liquid nitrogen from outside the device and stores it, and a liquid nitrogen storage means that continuously uses the liquid nitrogen in the liquid nitrogen storage means as a cold source for liquefying compressed air in place of the cold heat generated from the cold heat generation expander. Nitrogen gas taken out as a gas from the rectification column is passed through the heat exchange means and heat exchanged with the compressed air to raise the temperature and produce nitrogen gas as a product nitrogen gas. A continuous nitrogen gas production device characterized by being equipped with an extraction path.