JPH0418223B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a high-purity nitrogen gas production apparatus.

[Conventional technology]

Extremely large amounts of nitrogen gas are used in the electronics industry, but strict requirements have been placed on the purity of nitrogen gas from the perspective of maintaining and improving component precision. In other words, nitrogen gas generally uses air as a raw material,
After compressing this in a compressor, it is placed in an adsorption column to remove carbon dioxide gas and moisture, and then cooled by exchanging heat with a refrigerant through a heat exchanger, and then cryogenically liquefied and separated in a rectification tower to produce nitrogen gas. It is manufactured through the process of producing the product and raising the temperature to around room temperature through the heat exchanger described above. like this,
Conventional nitrogen gas production equipment uses an expansion turbine to cool the refrigerant in the heat exchanger that cools the compressed air compressed by the compressor. The low-boiling point nitrogen is extracted as a gas through the separation, and the remainder remains as oxygen-rich liquid air.It is driven by the pressure of the evaporated gas. However, expansion turbines have extremely high rotational speeds (tens of thousands of rotations per minute), making it difficult to follow load fluctuations and requiring specially trained operators. In addition, since this product rotates at high speed, high precision is required due to the mechanical structure.
Moreover, it is expensive, and has the disadvantage that specially trained personnel are required because the machine is complex. 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 a high-speed rotating section such as a squirrel.

[Problem that the invention seeks to solve]

In order to meet such demands, this inventor
We have developed a nitrogen gas production device that removes the expansion turbine and instead supplies chilled liquid nitrogen from outside into the rectification column, and has already applied for a patent (patent application 1983-
38050). This device can produce nitrogen gas of extremely high purity, making conventional purification equipment completely unnecessary. Furthermore, since the expansion turbine is removed, there are no adverse effects caused by it. Therefore, it is most suitable for the electronic industry. However, in the electronics industry, oxygen gas is also used in addition to nitrogen gas, and it has been desired to provide a device that can produce not only nitrogen gas but also oxygen gas with one device.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a high-purity nitrogen gas production device that can produce high-purity nitrogen gas without using an expansion turbine or a purification device, and can also produce oxygen gas at the same time. That purpose.

[Means for solving problems]

In order to achieve the above object, the high purity nitrogen gas production device of the present invention includes an air compression means for compressing air taken in from the outside, and carbon dioxide and moisture in the compressed air compressed by the air compression means. a heat exchange means for cooling the compressed air that has passed through the removal means to an ultra-low temperature, and a part of the compressed air cooled to an ultra-low temperature by the heat exchange means to be liquefied and stored at the bottom to produce only nitrogen. In a nitrogen gas production device equipped with a nitrogen rectification column that takes out the nitrogen gas from the upper side through a nitrogen gas extraction passage as a gas, a decentralizer with a built-in condenser installed at the top of the nitrogen rectification column and a bottom part of the nitrogen rectification column are used. a liquid air introduction pipe that guides the stored liquid air into the demultiplexer as cold air for cooling the condenser; and a first pipe that guides a portion of the nitrogen gas produced in the nitrogen rectification column into the condenser. a reflux liquid pipe, a second reflux liquid pipe that returns the liquefied nitrogen generated in the condenser to the nitrogen rectification column as a reflux liquid, and a liquid nitrogen storage means for receiving and storing liquid nitrogen from outside the apparatus. and an introduction path for continuously introducing the liquid nitrogen in the liquid nitrogen storage means into the nitrogen rectification column as cold air for liquefying compressed air instead of the cold heat generated from the cold heat generation expander, and the nitrogen rectification column. control means for controlling the liquid level of liquid air in the dephlegmator to a constant level by controlling the amount of liquid nitrogen supplied from the liquid nitrogen storage means; an oxygen rectification column that separates the two by utilizing The apparatus is configured to include an oxygen take-off passage for taking out the separated oxygen, and an adsorption tower provided at a predetermined location of the oxygen take-off passage for adsorbing and removing impure hydrocarbons in the oxygen.

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

〔Example〕

FIG. 1 shows an embodiment of the 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 column 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 the first heat exchanger, and the adsorption cylinder 12
The compressed air from which H ₂ O and CO ₂ have been adsorbed and removed is sent through the compressed air supply pipe 8 .
The compressed air sent here is cooled to an extremely low temperature by the heat exchange action of the heat exchanger 13. 14 is a second heat exchanger, in which H ₂ O and CO ₂ are
The compressed air that has been adsorbed and removed is sent in. The compressed air sent into this second heat exchanger 14 is also cooled to an extremely low temperature by its heat exchange action. Reference numeral 15 denotes a nitrogen rectification column equipped with a decentralizer section 21 with a built-in condenser 21a at the top of the column, which further cools the compressed air cooled to an ultra-low temperature by the first heat exchanger 13 and sent through the pipe 17. A part of it is liquefied and stored as liquid air 18 at the bottom, and only nitrogen is stored in a gaseous state at the upper ceiling. 23 is a liquid nitrogen storage tank that receives liquid nitrogen from outside the apparatus and stores it. To explain the rectification column 15 in more detail, the rectification column 15 is equipped with a dephlegmator 21 above a ceiling plate 20, and has a liquid nitrogen storage tank 23 in its upper part.
Liquid nitrogen is introduced from the inlet pipe 24a through the condenser 21 in the demultiplexer 21.
The liquid nitrogen generated in step a is transferred to the second introduction pipe 21.
It is supplied through c. These liquid nitrogens flow down into the liquid nitrogen reservoir 21d, and the overflow is transferred to the rectification column 1.
The air flows downward in the rectification column 15, contacts the compressed air rising from the bottom of the rectification column 15 in a countercurrent manner, cools it, and partially liquefies it. In this process, the high boiling point components in the compressed air are liquefied and accumulate at the bottom of the rectification column 15, and the low boiling point components, nitrogen gas, accumulate at the top of the rectification column 15. Further, the condenser 21a is disposed in the demultiplexer 21 as described above, and the rectification column 15
A part of the nitrogen gas accumulated in the upper part of the reflux liquid pipe 21b is sent through the first reflux liquid pipe 21b. The inside of this dephlegmator 21 is in a lower pressure state than the inside of the rectification column 15,
The liquid air stored at the bottom of the rectification column 15 (N ₂ 50-70%,
O ₂ 30-50%) 18 is pipe 1 with expansion valve 19a
9 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 21a is liquefied, becomes a reflux liquid, and flows down into the liquid nitrogen reservoir 21d in the rectification column 15. 2
Reference numeral 5 denotes a liquid level gauge, which controls the amount of liquid nitrogen supplied from the liquid nitrogen storage tank 23 by controlling the valve 26 according to the liquid level so that the liquid level of the liquid air in the decentralizer 21 is maintained at a constant level. . 27 is an extraction pipe for taking out the nitrogen gas accumulated in the upper part of the rectification column 15, which guides the ultra-low temperature nitrogen gas into the first heat exchanger 13, exchanges heat with the compressed air sent there, and brings it to room temperature. It acts to feed the water into the pipe 28. In this case, since He (-269°C) and H ₂ (-253°C), which have low boiling points, tend to accumulate at the top of the rectifying column 15 along with nitrogen gas, the extraction pipe 27 is connected to the top of the rectifying column 15.
It opens considerably below the top of He,
It is designed to extract only pure nitrogen gas that does not contain _H2 . 29 is a pipe that sends the vaporized liquid air in the dephlegmator 21 to the first heat exchanger 13 for heat exchange, and then releases the air as shown by arrow A;
a is its pressure holding valve. Reference numeral 40 denotes an oxygen rectification column, which communicates with the bottom of the partial condenser 21 of the nitrogen rectification column 15 through a liquid air supply pipe 41, and converts the liquid air sent into the partial condenser 21 into a head difference. The nitrogen content is removed by vaporization due to the difference in boiling point, and the oxygen is stored in a liquid state at the bottom. Reference numeral 42 denotes a discharge pipe that sends the vaporized waste liquid nitrogen into the vaporized liquid air discharge pipe 29, mixes it with the vaporized liquid air, and discharges it. 43 is an extraction pipe for taking out the liquid oxygen accumulated at the bottom of the oxygen rectification column 40, and an adsorption column 4 filled with a hydrocarbon adsorbent such as silica gel or alumina gel.
3a and a second heat exchanger 14. That is, since hydrocarbons are mixed in the liquid oxygen accumulated at the bottom of the oxygen rectification column 40, this is removed by liquid phase adsorption in the adsorption column 43a, and the liquid oxygen is highly purified. The air is fed into the second heat exchanger 14, where it exchanges heat with the compressed air sent in from the branch pipe 9' to be heated into a gas and fed into the product oxygen gas extraction pipe 44. 45
is a compressed air transfer pipe extending from the second heat exchanger 14 to the pipe 17, and the middle part thereof is located in the oxygen rectification column 40 to heat the liquid oxygen accumulated at the bottom and vaporize a part of it. The liquid air is brought into contact with the liquid air flowing down from the pipe 41 into the column 40 in a countercurrent manner, thereby improving the rectification efficiency. In addition,
Reference numeral 30 denotes a backup system line, which, when the air compression system line breaks down, liquid nitrogen in the liquid nitrogen storage tank 23 is evaporated by the evaporator 31 and sent to the main pipe 28, so that the supply of nitrogen gas is not interrupted. Do it like this. 32 is an impurity analyzer that analyzes the purity of the product nitrogen gas sent to the main pipe 28, and when the purity is low, valves 34,
34a is activated to release the product nitrogen gas to the outside as indicated by arrow B.

[Effect]

This device produces product nitrogen gas and oxygen gas as follows. That is, air is compressed by the air compressor 9, water in the compressed air is removed by the drain separator 10, and cooled by the fluorocarbon cooler 11. In this state, the air is sent to the adsorption column 12, and the H ₂ in the air is removed. Adsorbs and removes O and _CO2 .
Next, a part of the compressed air from which H ₂ O and CO ₂ have been adsorbed and removed is sent into the second heat exchanger 14 to be cooled to a low temperature, and the remaining part is sent to the first heat exchanger 13 to be cooled to an ultra-low temperature. After cooling, the rectification column 1 is added in that state.
Pour into the bottom of No.5. Next, this input compressed air is cooled by contacting with the liquid nitrogen sent into the rectification column 15 from the liquid nitrogen storage tank 23 and the liquid nitrogen generated in the condenser 21a and flowing down, and a part of it is liquefied and purified. It is stored as liquid air 18 at the bottom of the distillation column 15. In this process, due to the difference in the boiling points of nitrogen and oxygen (boiling point of oxygen -183°C, boiling point of nitrogen -196°C), oxygen, which is a high boiling point component in compressed air, liquefies, leaving nitrogen as a gas. Next, the remaining gaseous nitrogen is taken out from the extraction pipe 27 and sent to the first heat exchanger 13 where it is heated to near room temperature and sent out from the main pipe 28 as a product nitrogen gas. In this case, liquid nitrogen from liquid nitrogen storage tank 23 acts as a cold source for compressed air liquefaction;
The nitrogen gas itself is vaporized and taken out from the take-out pipe 27 as part of the product nitrogen gas. On the other hand, rectification column 1
The liquid air 18 accumulated at the bottom of the air filter 5 is sent into the demultiplexer 21 to cool the condenser 21, and then sent through the pipe 41 to the oxygen rectification column 40, where nitrogen is vaporized and removed and it becomes liquid oxygen. remains inside the tower 40. This remaining liquid oxygen is transferred to the adsorption tube 4 as a liquid.
3a, impure hydrocarbons therein are adsorbed and removed, and then fed into the second heat exchanger 14 where the temperature is raised and vaporized, and the product oxygen gas is removed as oxygen gas without hydrocarbons. 44
taken from. In this way, high-purity nitrogen gas and oxygen gas free of hydrocarbons can be obtained simultaneously using one device. In this case, the ratio (volume ratio) of the product nitrogen gas to the product oxygen gas obtained is approximately 10:1.

As mentioned above, this high-purity nitrogen gas production apparatus can produce high-purity product nitrogen gas and oxygen gas without using an expansion turbine, and does not cause any of the above-mentioned disadvantages caused by expansion turbines. Purification equipment can be eliminated. In particular, this high-purity nitrogen gas production apparatus is provided with a dephlegmator 21 having a built-in condenser 21a in the upper part of the rectification column 15, and a part of the nitrogen gas generated in the rectification column 15 is transferred into the condenser 21a. Since the liquefied nitrogen is constantly guided and liquefied, after a predetermined amount of liquefied nitrogen has accumulated in the condenser 21a, the liquefied nitrogen generated thereafter always returns to the rectification column 15 as a reflux liquid. Therefore, variations in product purity due to intermittent supply of reflux liquid from the condenser 21a (interruption of flow of reflux liquid causes liquid to run out in the upper rectifying shelf, causing gas blow-by phenomenon and reducing product purity). , the purity returns to a constant level when the flow resumes), and product nitrogen gas of stable purity can be supplied at all times. Moreover, in this device, even if the demand for product nitrogen gas fluctuates, the control means such as the liquid level gauge 25 controls the opening degree of the valve 26, etc.
By controlling the supply amount of liquid nitrogen to 5, the liquid level of liquid air in the demultiplexer 21 is controlled to a constant level, so it is possible to quickly respond to fluctuations in the demand amount, and also at this time, for the reason mentioned above. Therefore, there is no variation in purity. That is, when the demand for product nitrogen gas increases, the intake amount of raw material air is increased and this is supplied into the rectification column 15, similar to the conventional expansion turbine type device. As a result, the liquid air in the decentralizer 21 is vaporized to cool it, and the liquid level is lowered. This drop in the liquid level causes the liquid level gauge 25 to operate and supply liquid nitrogen, and as the amount of liquid nitrogen supplied increases, the amount of liquid air stored at the bottom of the rectification column increases, which causes the inside of the dephlegmator 21 to When the liquid level recovers, the liquid level gauge 25 appropriately reduces the amount of liquid nitrogen supplied to the rectification column. On the other hand, when the demand for product nitrogen gas decreases, contrary to the above, the decentralizer 21
As the liquid level in the column rises, the liquid level gauge 25 operates to reduce the amount of liquid nitrogen supplied to the rectification column 15 to eliminate unreasonableness due to excessive supply of liquid nitrogen. In this way, this device can quickly and rationally respond to changes in demand without causing variations in purity. Moreover, this device can produce highly pure oxygen gas at the same time as the nitrogen gas, making it possible to produce two types of high-purity gases with one device.

Note that, as shown in FIG. 2, a second branch pipe 9a is provided separately from the branch pipe 9', and this second
The branch pipe 9a is put into the special oxygen rectification column 40 without passing through the heat exchanger 14, and the high temperature that accumulates at the bottom of the oxygen rectification column 40 is removed using high-temperature compressed air that has not been cooled by the heat exchanger 14. Pure liquid oxygen may also be heated. By heating liquid oxygen with relatively high-temperature compressed air in this way, it is possible to quickly raise the temperature of liquid oxygen.
It becomes possible to quickly respond to changes in the amount taken out.

FIG. 3 shows another embodiment.

In this device, a liquid air supply pipe 41 is extended from the bottom of the rectification column 15 to the oxygen rectification column 40 instead of from the partial condenser 21 of the nitrogen rectification column 15.
Liquid air 18 accumulated at the bottom of the tank 5 is fed into an oxygen rectification column 40. The other parts are the same as the apparatus shown in FIG. 1, and the effects are also the same.

In addition, in all the above embodiments, the oxygen rectification column 4
The liquid oxygen accumulated at the bottom of the tube 43a is sent to the adsorption column 43a, and as shown in FIG.
It may be made to pass through the second heat exchanger 14. Then, as shown in the figure, a rectification column 15, 40 and a heat exchanger 1 are placed in a vacuum cooling box indicated by a dashed line in the figure.
3 and 14 may be housed to cut off heat intrusion from the outside and further improve purification efficiency. Further, the adsorption cylinder 43a is not limited to adsorption of carbon and hydrogen, but may be one suitable for removing components that may be mixed in in advance.

Furthermore, the apparatus of FIGS. 1 to 3 as well as the apparatus of FIG.
As shown in FIG. It may be made independent without being connected to the liquid air discharge pipe 29. By doing so, the oxygen rectification column 40 and the nitrogen rectification column 15 become independent from each other, so that oxygen gas can be produced almost unaffected by the amount of nitrogen gas produced by the nitrogen rectification column 15. You will be able to increase or decrease the amount.
Further, the stored liquid air may be supplied into the oxygen rectification column 40 from both the dephlegmator 21 and the nitrogen rectification column 15. Furthermore, the liquid oxygen taken out from the oxygen rectification column 40 may be directly used as product oxygen.

〔Effect of the invention〕

The high-purity nitrogen gas production device 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 entire device has no rotating parts and is prone to failure. It doesn't happen at all. Furthermore, while expansion turbines are expensive, liquid nitrogen storage tanks are inexpensive and do not require special personnel. Furthermore, the expansion turbine (which is driven by the pressure of the gas evaporated from the liquid air accumulated in the nitrogen rectification column) has an extremely high rotational speed (tens of thousands of rotations/minute), so load fluctuations (removal of product nitrogen gas) It is difficult to make fine-grained follow-up movements for changes in quantity. Therefore, it is difficult to accurately change the amount of liquid air supplied to the expansion turbine in accordance with changes in the amount of product nitrogen gas taken out, and to constantly cool compressed air, which is the raw material for producing nitrogen gas, to a constant temperature. As a result, the purity of the product nitrogen gas obtained varies, and low-purity products are frequently produced, resulting in an overall low purity product nitrogen gas.
The device of this invention uses a liquid nitrogen storage tank instead, and the supply amount can be finely adjusted as a cooling source. Therefore, it is possible to closely follow load fluctuations, and the purity is stable and extremely high. It becomes possible to produce nitrogen gas. Therefore, conventional purification equipment is not required. especially,
The apparatus of this invention is provided with a demultiplexer with a built-in condenser in the upper part of the nitrogen rectification column, and a part of the nitrogen gas generated in the rectification column is constantly introduced into the condenser in the demultiplexer. Liquefaction Reflux The reflux liquid is liquefied, and the reflux liquid is constantly returned to the rectification column, and at the same time, the amount of liquid nitrogen supplied from the liquid nitrogen storage means to the rectification column is controlled by the control means, so that the liquid in the fractionator is Since the surface is kept constant, it is possible to respond extremely quickly to load fluctuations, and in this case, there is no variation in the purity of the product nitrogen gas. Furthermore, this equipment is equipped with an oxygen rectification column, and after nitrogen gas has been extracted, the oxygen-rich liquid air is supplied from the nitrogen rectification column to the oxygen rectification column to produce oxygen, which is then passed through an adsorption column and turned into a product. Therefore, it becomes possible to efficiently produce high-purity oxygen gas that does not contain impure hydrocarbons. As described above, the apparatus of the present invention allows efficient production of high-purity nitrogen gas and high-purity oxygen gas with a single apparatus, and is therefore optimal for use in the electronics industry.

[Brief explanation of drawings]

Fig. 1 is a block diagram of one embodiment of the present invention, Fig. 2 is a block diagram of a modification thereof, Fig. 3 is a block diagram of another embodiment, and Figs. 4 and 5 are still other embodiments. FIG. 9...Air compressor, 12...Adsorption cylinder, 13,1
4...Heat exchanger, 15...Nitrogen rectification column, 17...
Pipe, 18...Liquid air, 21...Demultiplexer, 2
1a... Condenser, 21d... Liquid nitrogen reservoir, 23
...Liquid nitrogen storage tank, 24a...Introduction pipe, 2
7...Takeout pipe, 28...Main pipe, 40
...Oxygen rectification column, 41...Liquid air supply pipe,
42...Discharge pipe, 43...Take-out pipe, 43
a... Adsorption cylinder, 44... Product oxygen gas extraction pipe, 45... Pipe.

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. It is equipped with a heat exchange means for cooling, and a nitrogen rectification column that liquefies a part of the compressed air cooled to an ultra-low temperature by the heat exchange means, stores it at the bottom, and extracts only nitrogen as a gas from the upper side through the nitrogen gas extraction passage. In a nitrogen gas production device, a demultiplexer with a built-in condenser is installed at the top of a nitrogen rectification column, and liquid air stored at the bottom of the nitrogen rectification column is used as cold air for cooling the condenser in the demultiplexer. a first reflux liquid pipe that guides a portion of the nitrogen gas generated in the nitrogen rectification column into the condenser, and a first reflux liquid pipe that guides a portion of the nitrogen gas generated in the nitrogen rectification column into the condenser, and a first reflux liquid pipe that guides the liquefied nitrogen generated in the condenser to the reflux liquid. A second reflux liquid pipe that returns the liquid to the nitrogen rectification column; a liquid nitrogen storage means for receiving and storing liquid nitrogen from outside the apparatus; By controlling an introduction path that continuously leads the compressed air into the nitrogen rectification column as cold air for liquefaction in place of the generated cold heat, and the supply amount of liquid nitrogen from the liquid nitrogen storage means to the nitrogen rectification column. A control means for controlling the liquid level of the liquid air in the dephlegmator to a constant level, an oxygen rectification column for separating the liquid air using the difference in boiling point between nitrogen and oxygen, and the nitrogen rectification for the liquid air. A liquid air supply path for supplying the liquid air stored in the column or dephlegmator into the oxygen rectification column, an oxygen extraction path for taking out the oxygen separated in the oxygen rectification column, and a predetermined line of the oxygen extraction path. A high-purity nitrogen gas production device characterized by being equipped with adsorption towers installed at locations to adsorb and remove impure hydrocarbons from oxygen.