JPS6148073B2 - - 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 + 1/20 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 exchanges heat with the compressed air compressed by the compressor. (Nitrogen with a low boiling point is extracted as a gas through cryogenic liquefaction separation, and the remainder becomes oxygen-rich liquid air and accumulates.) It is designed to be 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. Furthermore, since this type of rotor rotates at a high speed, it requires high precision in its mechanical structure, is expensive, and has the disadvantage of requiring specially trained maintenance personnel due to its 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. Furthermore, since it takes a long time for a nitrogen gas production device to start up from a stopped state to produce a product nitrogen gas, there has been a strong demand for shortening this start-up time.

[Purpose of the invention]

The object of the present invention is to provide an apparatus that can produce highly pure nitrogen gas without using an expansion turbine or a purification device and that has a short startup 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. a first introduction path that continuously leads into the rectification column as a cold water;
A second introduction path for introducing liquid nitrogen into the demultiplexer as cold water for cooling the condenser in the liquid nitrogen storage means, a valve for opening and closing the second introduction path, and a 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 to the nitrogen taken out as a gas from the rectification column and the A nitrogen gas extraction path is provided in which the liquid nitrogen, which has completed its function as a cold source and has been vaporized in the rectification column, is passed through the heat exchange means and exchanged with the compressed air passing through the column to raise its temperature and produce nitrogen gas as a product. It takes the structure of preparing.

Next, the present invention will be explained in detail 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 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. 8 is a compressed air supply pipe that sends compressed air in which H ₂ O and CO ₂ have been adsorbed and removed. 13 is a first heat exchanger, in which H ₂ O and
Compressed air from which CO ₂ has been adsorbed and removed is sent in.
14 is a second heat exchanger, and the first heat exchanger 1
Compressed air that has passed through step 3 is sent in. 15 is a rectification column equipped with a demultiplexer 21 with a built-in condenser 21a at the top of the column, and compressed air cooled to an ultra-low temperature by first and second heat exchangers 13 and 14 and sent through a pipe 17 is used. It is further cooled, a part of which is liquefied and stored in the bottom as liquid air 18, and only nitrogen in a gaseous state is stored in the upper ceiling. 2
Reference numeral 3 denotes a liquid nitrogen storage tank that stores liquid nitrogen supplied from the outside, and sends the internal liquid nitrogen (high purity product) to the upper side of the rectification column 15 via the first introduction pipe 24a. It is used as a cooling source for the compressed air supplied into the rectification column 15. Furthermore, when starting up the apparatus, liquid nitrogen is introduced into the partial condenser section 21 of the rectification column 15 via the second introduction pipe 24b for starting, which is equipped with a valve 21c, to shorten the start-up time. It's getting old. The valve 21c is
By opening/closing or adjusting the degree of opening, the flow of liquid nitrogen flowing through the pipe 24b is interrupted, the flow is adjusted, or the flow rate is adjusted. Therefore, in the present invention, opening and closing of the introduction path pipe 24b includes not only opening and closing of the flow path but also valve operations performed for the purpose of flow rate adjustment. To explain the rectification column 15 in more detail, the rectification column 15 is equipped with a demultiplexer 21 above a ceiling plate 20, and a condenser 2 in the demultiplexer 21
A part of the nitrogen gas accumulated in the upper part of the rectification column 15 is sent to 1a via 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, and the liquid air (N ₂ : 50-70%, O ₂ : 30-50%) 18 stored at the bottom of the rectification column 15 is sent through a pipe 19 with an expansion valve 19a,
It is designed to evaporate and 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.
25 is 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 part 21 is kept at a constant level. do. Liquid nitrogen generated in the condenser 21a in the demultiplexer 21 is supplied to the upper part of the rectification column 15 through a pipe 21c, and liquid nitrogen is supplied from the liquid nitrogen storage tank 23 to the second The reflux liquid is supplied through the pipe 24a, passes through the liquid nitrogen reservoir 21d, flows down inside the rectification column 15, contacts countercurrently with the compressed air rising from the bottom of the rectification column 15, and is cooled. Some of it is liquefied. 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. Reference numeral 27 denotes an extraction pipe for taking out the nitrogen gas accumulated in the upper ceiling of the rectification column 15 as product nitrogen gas, which guides the ultra-low temperature nitrogen gas into the second and first heat exchangers 14 and 13 and sends it there. The main pipe 28 is heated to room temperature by exchanging heat with the compressed air.
It has the effect of sending it into the In this case, 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 opening is considerably lower than the top, and only pure nitrogen gas containing no He or H ₂ is taken out as product nitrogen gas. 29 transfers the vaporized liquid air in the dephlegmator 21 to the second and first heat exchangers 14 and 13;
29a is its pressure holding valve. In addition, 30 is a backup system line, and when the air compression system 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, and the supply of nitrogen gas is interrupted. Make sure that there are no 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, operates valves 34, 34a to release the product nitrogen gas to the outside as shown by arrow B. have the effect of

In this apparatus, product nitrogen gas is produced in the following manner. First, the air compressor 9 is operated, and the valves 26 and 24c are operated to supply liquid nitrogen from the liquid nitrogen storage tank 23 into the rectification column 15 and the dephlegmator 21. The liquid nitrogen supplied into the rectification column 15 is vaporized because the rectification column 15 has not yet been cooled, and most of it is vaporized into the product take-out pipe 27.
The gas reaches the second and first heat exchangers 14, 13 via the air, cools them and becomes room temperature gas, which is discharged into the atmosphere through the pipe 28 and valve 34a. Also,
A part of the liquid nitrogen vaporized in the rectification column 15 enters the condenser 21a in the demultiplexer 21 via the first introduction pipe 21b, cools it, and then flows into the pipe 21.
e into the atmosphere. In addition, the liquid nitrogen supplied from the liquid nitrogen storage tank 23 into the dephlegmator 21 is
A portion of the gas vaporizes and exits into the atmosphere from the discharge pipe 29, but since the heat capacity of the partial condenser 21 is small, the majority remains in the partial condenser 21 in a liquid state. On the other hand, the air compressed by the air compressor 9 has moisture removed by a drain separator 10, is cooled by a freon cooler 11, and in that state is sent to an adsorption column 12 where H ₂ O and CO ₂ are adsorbed and removed. be done. Then,
The compressed air from which H ₂ O and CO ₂ have been adsorbed and removed is sent to the first and second heat exchangers 13 and 14, which are cooled by vaporized liquid nitrogen in the rectification column 15, and is brought to an ultra-low temperature. It is cooled and put into the lower part of the rectification column 15 in that state. In this case, if liquid nitrogen is not supplied to the dephlegmator 21, the rectification column 15 must produce the reflux liquid itself. That is, the compressed air sent into the rectification column 15 is cooled and liquefied using liquid nitrogen supplied from the liquid nitrogen storage tank 23, and this is sent into the demultiplexer 21 to liquefy the condenser 21a. Liquid nitrogen must be created to cool and serve as a reflux liquid. However, since the rectifier 15 is not cooled when the device is started, the liquid nitrogen supplied from the liquid nitrogen storage tank 23 does not serve as a cold source for liquefying compressed air, but immediately vaporizes and is injected into the rectifier 15. The compressed air is passed through the pipe 27 along with the arrow B.
escaping into the atmosphere. Therefore, rectification tower 1
The liquid air 18 does not easily accumulate at the bottom of the dephlegmator 5, and as a result, it becomes difficult to feed the liquid air into the dephlegmator 21, so it takes a long time to start up (approximately 15 to 16 hours). However, the demultiplexer 21
When liquid nitrogen is supplied into the rectifying column 1, the condenser 21a is immediately cooled by it, and liquid nitrogen, which becomes the reflux liquid, is quickly generated, and this is sent to the rectifying column 1.
It flows down into 5. Therefore, this combined with the liquid nitrogen supplied from the liquid nitrogen storage tank 23 quickly cools the inside of the rectification column 15, and the raw compressed air introduced from the lower part of the rectification column 15 is liquefied and separated. is liquefied, nitrogen remains as a gas, and this is taken out from the take-out pipe 27 as a product nitrogen gas (rise time is approximately 1 hour). Nitrogen gas is taken out from the take-out pipe 27 in a short time after the start-up of the device, and is sent to the second and first heat exchangers 14 and 13, where it is heated to near room temperature, and then released from the main pipe 28 as a product nitrogen gas. sent out. In this case, rectification column 1
5 is at a high pressure due to the compression force of the air compressor 9 and the vapor pressure of liquid nitrogen, the pressure of the product nitrogen gas taken out from the takeout pipe 27 is also high. Therefore, this product nitrogen gas is particularly effective when used as a purge gas. The liquid nitrogen fed into the rectification column 15 from the liquid nitrogen storage tank 23 via the first inlet pipe 24a acts as a cold source for liquefying compressed air, and is vaporized and sent to the extraction pipe. 27 as part of the product nitrogen gas. In addition, after the liquid air 18 has accumulated at the bottom of the rectification column 15, it is cooled for cooling the condenser 21a and sent to the demultiplexer 21, so that the liquid nitrogen supply is no longer necessary, and the valve 24c is closed. As mentioned above, after the liquid nitrogen in the liquid nitrogen storage tank 23 has finished its role as a cold source for compressed air liquefaction, it is not discarded, but is combined with high-purity nitrogen gas made from compressed air. It will be commercialized and used without waste.

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, it is possible to respond quickly to fluctuations in demand, and also at this time, there is no variation in purity due to 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 level gauge 25 indicates that the liquid air in the rectification column is The amount of nitrogen supplied is appropriately controlled to decrease. When the demand for product nitrogen gas decreases, contrary to the above, the liquid level in the dephlegmator 21 rises, so the liquid level gauge 25 operates to reduce the amount of liquid nitrogen supplied to the rectification column 15. Eliminate the absurdity based on oversupply of liquid nitrogen.
In this way, this device can quickly and rationally respond to changes in demand without causing variations in purity. Furthermore, when the apparatus is started up, liquid nitrogen is supplied to the partial condenser 21, and as a result, the reflux liquid is generated quickly, and the start-up time can be significantly shortened.

FIG. 2 shows an embodiment in which the apparatus shown in FIG. 1 is provided with a vacuum cooling box. That is, in this example,
Rectification column 15 and first and second heat exchangers 13,1
4 is housed in a vacuum cooling box (indicated by a dashed line),
Efforts are being made to improve rectification efficiency. The other parts are the same as the apparatus shown in FIG.

In the above embodiment, the valve 24c is closed after the liquid air accumulates at the bottom of the rectification column 15, but the opening degree of the valve 24c may be adjusted to reduce the flow rate.

〔Effect of the invention〕

The high-purity liquid gas production device of the present invention does not use an expansion turbine, but instead uses a liquid nitrogen storage means such as an inexpensive liquid nitrogen storage tank that does not have any rotating parts, so the entire device has no rotating parts and is less likely to malfunction. It will not occur at all and will be cheaper. Furthermore, the expansion turbine (which is driven by the pressure of gas evaporated from the liquid air accumulated in the nitrogen rectification column) has an extremely high rotation speed (tens of thousands of rotations/minute), so load fluctuations (removal of product nitrogen gas) It is difficult to precisely follow the changes in the amount of product nitrogen gas taken out, and the rotation speed of the expansion turbine is changed accurately according to changes in the amount of product nitrogen gas extracted, and the compressed air, which is the raw material for nitrogen gas production, is constantly cooled to a constant temperature. It is not easy to do this, and as a result, the purity of the product nitrogen gas that is obtained varies, and low-purity products are frequently produced, resulting in the overall purity of the product nitrogen gas being low. Using a liquid nitrogen storage tank and using liquid nitrogen as a cooling source, the amount of which can be finely adjusted, makes it possible to closely follow load fluctuations, making it possible to produce nitrogen gas with stable and extremely high purity. . Therefore, conventional purification equipment is not required. In particular, the apparatus of the present invention has a fractionator with a built-in condenser installed in the upper part of the fractionator, and a part of the nitrogen gas generated in the fractionator is constantly introduced into the condenser in the fractionator. to liquefy and reflux liquefy,
At the same time, the reflux liquid is constantly returned in the rectification column, and at the same time, the liquid level in the fractionator is kept constant by controlling the supply amount of liquid nitrogen from the liquid nitrogen storage means to the rectification column by the control means. Therefore, 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, since this device communicates the decentralizer and the liquid nitrogen storage means through the second introduction path, when the device is started up, liquid nitrogen is supplied into the dephlegmator to cool the condenser quickly. By creating a liquid nitrogen reflux solution, it will be possible to significantly shorten the start-up time.

[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 modification thereof. 9... Air compressor, 11, 12... Adsorption tube, 1
3, 14... Heat exchanger, 15... Nitrogen rectification column, 1
7... Pipe, 18... Liquid air, 21... Decentralizer, 21a... Condenser, 21b... First reflux liquid pipe, 21c... Second reflux liquid pipe, 21d
...Liquid nitrogen reservoir, 23...Liquid nitrogen storage tank, 24
a...First introduction pipe, 24b...Second introduction pipe, 24c...Valve, 27...Takeout pipe, 28...Main 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. 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. a first introduction path that continuously introduces the liquid nitrogen into the rectification column as cold air for liquefying compressed air instead of the cold heat generated from the cold heat generating expander; a second introduction path for introducing cold water for cooling the condenser into the demultiplexer; a valve for opening and closing the second introduction path; A control means for controlling the liquid level of liquid air in the dephlegmator to a constant level by controlling the supply amount; A high-purity nitrogen gas characterized by being equipped with a nitrogen gas extraction passage 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. Manufacturing equipment.