JPS6148071B2 - - Google Patents

Description

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

[Background 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 put into an adsorption cylinder to remove carbon dioxide and moisture, and then passed through a heat exchanger to cool it by exchanging heat with a refrigerant, and then cryogenically liquefied and separated in a rectification tower to produce nitrogen gas. The product is manufactured through a process of manufacturing the product and raising the temperature of the product to around room temperature through the heat exchanger described above. however,
Since the product nitrogen gas produced in this way contains oxygen as an impurity, it is often inconvenient to use it as it is. Impure oxygen can be removed by adding a trace amount of hydrogen into nitrogen gas using a Pt catalyst and reacting with the impure oxygen in an atmosphere at a temperature of about 200°C to remove it as water, or by using a Ni catalyst to remove nitrogen gas. There is a method of removing impure oxygen in a gas by bringing it into contact with a Ni catalyst in an atmosphere at a temperature of about 200°C to cause a reaction of Ni+1/2O ₂ →NiO. However, in all of these methods, the nitrogen gas must be heated to a high temperature and brought into contact with the catalyst, so the apparatus cannot be incorporated into a nitrogen gas production apparatus that is an ultra-low temperature system. Therefore, it is necessary to install a purification device separately from the nitrogen gas production device, which has the disadvantage that the entire device becomes large. Furthermore, the above method requires high precision in adjusting the amount of hydrogen added, and if the amount of hydrogen that is not added is just enough to react with the amount of impure oxygen, oxygen may remain or the added hydrogen may remain. There is a problem in that it requires skill to operate because it becomes an impurity. In addition, in the above method, regeneration of NiO produced by reaction with impure oxygen (NiO
＋H ₂ →Ni＋H ₂ O), H ₂ for regeneration
Gas equipment was required, leading to an increase in refining costs. Therefore, these improvements have been strongly desired.

In addition, 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. Through cold liquefaction separation, low-boiling point nitrogen is extracted as a gas, and the remainder becomes oxygen-rich liquid air and accumulates.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).
However, it is difficult to follow load fluctuations, and specially trained operators are required. Also,
Since this device rotates at a high speed, it requires high precision in its mechanical structure, is expensive, and has the disadvantage of requiring specially trained personnel due to its complicated mechanism. In other words, since the expansion turbine has a high-speed rotating part, it causes various problems such as those mentioned above.
There has been a strong demand for the elimination of expansion turbines having such high-speed rotating parts.

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). Since this device can produce nitrogen gas of extremely high purity, conventional purification equipment is 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, in addition to nitrogen gas,
Oxygen gas is also used, and it has been desired to provide a device that can produce not only nitrogen gas but also oxygen gas with one device.

[Purpose of the invention]

An object of the present invention is to provide a high-purity nitrogen gas production apparatus 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.

[Disclosure of the invention]

In order to achieve the above object, the high purity nitrogen gas production apparatus 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 rectification column that extracts gas from the upper side, there is a partial condenser with a built-in condenser installed at the top of the rectification column, and liquid air stored at the bottom of the rectification column is transferred to the condenser. A liquid air introduction pipe that leads into the dephlegmator as cold air for cooling, a discharge pipe that discharges the vaporized liquid air generated in the dephlegmator to the outside, and a portion of the nitrogen gas generated in the rectification column. a first reflux liquid pipe that guides the liquefied nitrogen into the condenser, and a second reflux pipe that returns the liquefied nitrogen produced in the condenser to the rectification column as a reflux liquid.
a reflux liquid pipe, a liquid nitrogen storage means for receiving and storing liquid nitrogen from outside the device, 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 liquefy compressed air. The liquid air in the dephlegmator is controlled by an introduction path that continuously leads into the rectification column as a cooling source of the liquid air, and by controlling the amount of liquid nitrogen supplied to the rectification column from the liquid nitrogen storage means. a control means for controlling the surface constant;
The nitrogen taken out as a gas from the rectification column and the liquid nitrogen that has finished acting as a cold source and has been vaporized in the rectification column are passed through the heat exchange means and exchanged heat with the compressed air passing through the inside of the column. A nitrogen gas take-out passage for raising product nitrogen gas, a plurality of adsorption cylinders having a nitrogen gas selective adsorption capacity, and a plurality of adsorption cylinders that communicate the inlets of the plurality of adsorption cylinders and the outlet of the discharge pipe in the partial condenser, respectively. an inflow path pipe, a plurality of first on-off valves provided in each of the plurality of inflow path pipes, an oxygen gas extraction path extending from the outlet of each of the plurality of adsorption cylinders, a regeneration means for the adsorption cylinder, and the regeneration unit. a plurality of regeneration paths that communicate the means with the plurality of adsorption cylinders, a plurality of second on-off valves provided in each of the plurality of regeneration paths, and any one of the plurality of adsorption cylinders. The apparatus is configured to include on-off valve control means for controlling the opening and closing of the first and second on-off valves so that the remaining adsorption cylinders that have been adsorbed are regenerated or stopped.

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

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 cylinder 12 is filled with a molecular sieve and functions to adsorb and remove H ₂ BO and CO ₂ in the air compressed by the air compressor 9. 13 is a heat exchanger, in which the compressed air from which H ₂ O and CO ₂ have been adsorbed and removed by the adsorption cylinder 12 is
The compressed air is fed 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. 15 is a nitrogen rectification column equipped with a demultiplexer 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 heat exchanger 13 and sent through the pipe 17, and a part of it is is liquefied and stored in the bottom as liquid air 18, while only nitrogen is stored in a gaseous state in the upper ceiling. That is, the rectification column 15 is equipped with a dephlegmator 21 above the ceiling plate 20. 23 is a liquid nitrogen storage tank that receives liquid nitrogen from outside the apparatus and stores it. Liquid nitrogen is directly fed into the upper part of the rectification column 15 from the liquid nitrogen storage tank 23 through the introduction pipe 24a, and the demultiplexer 21 is fed into the liquid nitrogen reservoir 21d provided at the upper part. The liquid nitrogen produced in the condenser 21a is supplied downstream through the second reflux liquid pipe 21c, and both liquid nitrogens overflow and flow downward in the rectification column 15. It comes into contact with compressed air rising from the bottom in a countercurrent manner, cools it, and liquefies a portion of 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, as mentioned above, the condenser 21a is disposed inside the dephlegmator 21, and a part of the nitrogen gas accumulated in the upper part of the rectification column 15 is passed through the first reflux liquid pipe 21b. will be sent.
The inside of this dephlegmator 21 is in a lower pressure state than the inside of the rectifying column 15, and the liquid air (N ₂ 50-70%, O ₂ 30-50%) 18 stored at the bottom of the rectifying column 12 expands. Valve 1
It is fed through a pipe 19 with 9a and is vaporized to cool the internal temperature to a temperature below the boiling point of liquid nitrogen. Due to this cooling, the condenser 21
The nitrogen gas fed into the tank a is liquefied and flows down into the liquid nitrogen reservoir 21d in the rectification column 15 as described above. A liquid level gauge 25 controls a valve 26 according to the level of liquid air in the decentralizer 21 to control the amount of liquid nitrogen supplied from the liquid nitrogen storage tank 23 . Reference numeral 27 is a take-out pipe for taking out the nitrogen gas accumulated in the upper part of the rectification column 15, which guides the ultra-low temperature liquid gas into the heat exchanger 13, where it exchanges heat with the compressed air sent there, and is constantly sent to the main pipe 28. act. In this case, at the top of the rectification column 15, He (-
269°C) and H ₂ (-253°C) tend to accumulate, the take-out pipe 27 is opened well below the top of the rectification column 15 to allow only pure nitrogen gas without He and H ₂ to be mixed. It's supposed to be taken out. Reference numeral 29 is a discharge path pipe that sends the waste vaporized liquid air in the dephlegmator 21 to the heat exchanger 13, and 29a is its pressure holding valve. 40, 41, 42 are inside each
It is an adsorption column filled with an adsorbent (synthetic zeolite: molecular sieve) that selectively adsorbs _N2 , and its inlets are connected to valves 40b, 41b,
It is connected to the outlet of the discharge pipe 29 through inflow passages 40a, 41a, 42a with 42b. 44 is a vacuum pump, which connects the adsorption cylinder 4 through a suction path 43 and valves 40c, 41c, and 42c.
It is connected to the entrances of 0, 41, and 42. 40
d, 41d, and 42d are the adsorption cylinders 4, respectively.
0, 41, and 42, and are provided with valves 40e, 41e, and 42e, respectively. These outlet paths 40d, 41d, 42d
is connected to a buffer tank 46 via a product oxygen gas extraction path 45. The adsorption cylinders 40, 41,
42, one of them is used for adsorption, while the remaining one is subjected to the regeneration action by vacuum suction of the vacuum pump 44, and then one of the regenerated ones is used for adsorption, and first performs the adsorption operation. What was previously used will be reborn. Each of the above valves 40b, 40c, 40
e, 41b, 41c, 41e, 42b, 42c,
42e is controlled to open and close by a known valve control means (not shown), thereby realizing the above operations of the adsorption cylinders 40 to 42. The suction cylinders 40 to 42 repeat the above operations to perform continuous suction operation. In addition, 30 is a backup system line, and when the air compression line breaks down, the liquid nitrogen in the liquid nitrogen storage tank 23 is evaporated by the evaporator 31 and sent to the main pipe 28, thereby preventing the supply of nitrogen gas from being interrupted. Make sure not to. 32 is an impurity analyzer, which 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. Furthermore, the dashed line indicates a vacuum cooling box, which accommodates the rectification column 15 and the like to improve purification efficiency.

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, the compressed air from which H ₂ O and CO ₂ have been adsorbed and removed is sent to the heat exchanger 13 to be cooled to an ultra-low temperature, and in this state is introduced into the lower part of the rectification column 15 . Then,
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 overflow liquid nitrogen from the liquid nitrogen reservoir 21d, and a part of it is liquefied to form the rectification column. It is stored as liquid air 18 at the bottom of 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, remove the nitrogen remaining in this gaseous state through pipe 2.
7 and sent to the heat exchanger 13, heated to near room temperature, and sent out from the main pipe 28 as a product nitrogen gas. In this case, liquid nitrogen storage tank 2
The liquid nitrogen supplied from 3 acts as a cold source for liquefying compressed air, and is itself vaporized and taken out from the take-out pipe 27 as a part of the product nitrogen gas. On the other hand, the liquid air 18 accumulated in the lower part of the rectification column 15 is sent into the dephlegmator 21 and
After cooling the air, it is vaporized to become waste vaporized liquid air, which is fed into the heat exchanger 13 through the pipe 29 and raised in temperature. There, the nitrogen gas is adsorbed and removed and becomes oxygen gas, which is then sent to the buffer tank 4.
sent to 6. In this case, the adsorption cylinders 40, 4
Any one of the cylinders 1 and 42 is activated for adsorption, while the remaining ones are subjected to the vacuum regeneration action of the vacuum pump 44, and then the adsorption column that has activated adsorption starts regeneration.
Each valve 40b to 42b, 40c to 42c, and one of the regenerated valves enters the adsorption operation.
40e to 42e are controlled by valve control means.
In this way, high purity nitrogen gas and oxygen gas can be obtained simultaneously using one device. In this case, the ratio (volume ratio) of the product nitrogen gas and product oxygen gas obtained is approximately 10:1.

As mentioned above, this nitrogen gas production device can produce high-purity product nitrogen gas without using an expansion turbine, and does not have any of the above-mentioned disadvantages caused by expansion turbines, and can eliminate the need for a purification device. . In particular, this high-purity nitrogen gas production apparatus has a demultiplexer 21 with a built-in condenser 21a in the upper part of the rectification column 15.
is provided, and in order to constantly guide a part of the nitrogen gas in the rectification column 15 into the condenser 21a and liquefy it, after a predetermined amount of liquefied nitrogen has accumulated in the condenser 21a, the liquefied nitrogen generated thereafter is constantly returned 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., and controls the amount of liquid nitrogen supplied to the rectification column 15. Since the liquid level of the liquid air in the dephlegmator 21 is controlled to be constant, fluctuations in demand can be quickly responded to, and also at this time, variations in purity do not occur for the reasons mentioned above. In other words, when the demand for product nitrogen gas increases, most of the produced nitrogen gas is produced from the take-out pipe 27 and the condenser 21
As the amount of nitrogen gas sent to a decreases, the amount of reflux liquid generated in the condenser 21a decreases, and as a result, the amount of liquid air 18 stored at the bottom of the rectification column decreases, and the amount of liquid air sent from there decreases. Since the amount of liquid air decreases, the level of liquid air in the dephlegmator 21 decreases.
As a result, the liquid level gauge 25 is activated to increase the amount of liquid nitrogen supplied to the rectification column 15, and by vaporizing the liquid nitrogen, product nitrogen gas is quickly produced to quickly respond to an increase in demand. When the amount of liquid air stored at the bottom of the rectification column increases due to the increase in the supply amount of liquid nitrogen, and the liquid level in the dephlegmator 21 recovers, the liquid level gauge 25 detects the amount of liquid air stored in the rectification column 15. The supply amount of liquid nitrogen is appropriately controlled to decrease. When the demand for product nitrogen gas decreases, contrary to the above, the decentralizer 2
Since the liquid level in the distillation column 1 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. Furthermore, this device produces oxygen gas from unnecessary oxygen-rich liquid air that has been passed through a rectification column and has extremely low impurities. can be manufactured efficiently.

Incidentally, instead of the liquid rectification column shown in FIG. 1, a rectification column manufactured as shown in FIG. 2 may be used. That is, in this rectification column 15, a dephlegmator part 21 is separated from the column part 15 by a partition plate 20 in which a large number of pipes 20a are installed, and a liquid nitrogen storage tank is provided in the dephlegmator part 21. Liquid nitrogen is supplied from pipe 23, and compressed air supplied from pipe 19 into tower section 15 is cooled within pipe 20a of partition plate 20 to liquefy the oxygen content, and the nitrogen is passed in a gaseous state to the dephlegmator section. It is designed to be taken out from the top of 21. In this case, unlike the previous embodiment, the liquid air 18 accumulated at the bottom of the rectification column 15 is used as a raw material for oxygen gas,
It is heated in the heat exchanger 13 and supplied to any adsorption column 40, 41, 42 in a vaporized state.

〔Effect of the invention〕

The high-purity liquid gas production apparatus of the present invention does not use an expansion turbine, but instead uses a liquid nitrogen storage tank that does not have any rotating parts, so the apparatus as a whole does not have any rotating parts, and no failure occurs 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 perform fine-grained follow-up operation for changes in quantity. Therefore,
Accurately changes the amount of liquid air supplied to the expansion turbine according to changes in the amount of product nitrogen gas extracted,
It is difficult to constantly cool the compressed air, which is the raw material for nitrogen gas production, to a constant temperature, and as a result, the purity of the product nitrogen gas obtained varies, and low-purity products are frequently produced, resulting in the overall production of nitrogen gas purity was decreasing. This device uses a liquid nitrogen storage tank instead, and uses liquid nitrogen, whose supply amount can be finely adjusted, as the cooling source for the compressed air, making it possible to closely follow load fluctuations, and with extremely stable purity. It becomes possible to produce high nitrogen gas. Therefore, conventional purification equipment is not required. In particular, this equipment is equipped with a fractionator with a built-in condenser at the top of the fractionator, and a portion of the nitrogen gas generated in the fractionator is constantly introduced into the condenser inside the fractionator to liquefy and reflux it. At the same time, the control means controls the amount of liquid nitrogen supplied from the liquid nitrogen storage means to the rectification tower to maintain the liquid level in the dephlegmator. Since it 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. Moreover, this device
Oxygen-rich waste gas (waste vaporized liquid air) from which impurities such as CO ₂ and H ₂ O have been removed by passing through a rectification tower etc. after nitrogen gas collection is passed from the nitrogen rectification tower. Since oxygen gas is produced by supplying it to the adsorption cylinder, oxygen gas can be obtained efficiently.
As described above, the apparatus of the present invention is ideal for use in the electronics industry because it can efficiently produce high-purity nitrogen gas and oxygen gas with one apparatus.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of a modified example of a rectification column. 9... Air compressor, 12... Adsorption cylinder, 13...
Heat exchanger, 15...Nitrogen rectification column, 17...Pipe, 18...Liquid air, 21...Decentralizer, 21a
...Condenser, 21d...Liquid nitrogen reservoir, 23...
Liquid nitrogen storage tank, 24a...Introduction pipe, 27...
...Takeout pipe, 28...Main pipe, 29...
Discharge pipe, 40, 41, 42... adsorption cylinder, 4
4...Vacuum pump, 45...Product oxygen gas extraction path.

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 at the bottom and extracts only nitrogen as a gas from the upper side, a condenser with a built-in condenser installed in the upper part of the rectification column; a liquid air introduction pipe that guides the liquid air stored at the bottom of the rectification column into the condenser as cold air for cooling the condenser; a discharge pipe for discharging the vaporized liquid air produced in the fractionator to the outside; a first reflux pipe for guiding a portion of the nitrogen gas produced in the rectification column into the condenser; A second reflux liquid pipe that returns the liquefied nitrogen produced in the vessel as a reflux liquid into the rectification column, a liquid nitrogen storage means for receiving and storing liquid nitrogen from outside the apparatus, and a liquid nitrogen storage means inside the liquid nitrogen storage means. an introduction path for continuously introducing liquid nitrogen into the rectification column as a cold source for liquefying compressed air in place of the cold heat generated from the cold heat generation expander; A control means for controlling the level of liquid air in the dephlegmator to a constant level by controlling the amount of nitrogen supplied; a nitrogen gas extraction path for increasing the temperature of the vaporized liquid nitrogen through the heat exchange means and exchanging heat with the compressed air passing through the heat exchange means to produce a product nitrogen gas; , a plurality of inlet pipes that communicate the inlets of the plurality of adsorption cylinders and the outlet of the discharge pipe in the demultiplexer, and a plurality of first inflow pipes provided in each of the plurality of inflow pipes. an on-off valve, an oxygen gas extraction path extending from the outlet of the plurality of adsorption cylinders, a regeneration means for the adsorption cylinder, a plurality of regeneration paths that communicate the regeneration means with the plurality of adsorption cylinders, and the plurality of regeneration cylinders. A plurality of second opening/closing valves provided respectively in the passages and the first and second opening/closing valves are operated so that any one of the plurality of adsorption cylinders is activated for adsorption and the remaining adsorption cylinder is regenerated or stopped. A high-purity nitrogen gas production device characterized by comprising an on-off valve control means for controlling the opening and closing of a valve.