JPH0731000B2 - Ultra high purity nitrogen gas production equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to an ultrahigh-purity nitrogen gas production apparatus.

[Conventional technology]

A conventional nitrogen gas production apparatus uses an expansion turbine for cooling the refrigerant of a heat exchanger for heat exchange of compressed air compressed by a compressor, and uses the expansion turbine to collect liquid air (deep cooling) in the rectification tower. By the liquefaction separation, low boiling point nitrogen is taken out as a gas,
The rest is stored as oxygen-rich liquid air) and is driven by the pressure of the gas evaporated from it. However,
The expansion turbine has an extremely high rotation speed (tens of thousands of times / minute), and it is difficult to follow the load fluctuation, and thus a specially trained operator is required. Further, since this machine rotates at high speed, it requires high precision in terms of mechanical structure, is expensive, and has a complicated mechanism, which requires specially trained maintenance personnel. That is, since the expansion turbine has a high-speed rotating portion, the above-mentioned various problems occur, and there is a strong demand for the removal of the expansion turbine having such a high-speed rotating portion.

[Problems to be Solved by the Invention]

In order to meet such a demand, the present inventor provides a liquid nitrogen storage tank for storing liquid nitrogen in place of the expansion turbine, and supplies the liquid nitrogen as cold from the liquid nitrogen storage tank to the rectification column. We have proposed a high-purity nitrogen gas production device called "Patent application No. 59-4123". Since the device does not have an expansion turbine, it is possible to solve all the above-mentioned problems that the expansion turbine has. However, in the above-mentioned proposed apparatus, it is generated in the rectification tower,
In some cases, the product nitrogen gas taken out from the product nitrogen gas take-out path is mixed with an impurity gas such as helium and hydrogen, which causes a problem that the purity of the product nitrogen gas is lowered.

The present invention has been made in view of the above circumstances, and an ultrahigh-purity nitrogen gas production apparatus that does not use an expansion turbine and does not mix impurities such as helium and hydrogen into product nitrogen gas. The purpose is to provide.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the ultrahigh-purity nitrogen gas production apparatus of the present invention comprises an air compression means for compressing air taken in from the outside, and carbon dioxide gas in compressed air compressed by this air compression means. Removal means for removing water and heat, heat exchange means for cooling the compressed air that has passed through this removal means to an ultralow temperature, and a part of the compressed air cooled to an ultralow temperature by this heat exchange means to liquefy and store only nitrogen inside. , A liquid nitrogen storage means for storing liquid nitrogen, and a liquid nitrogen introduction passage for guiding the liquid nitrogen in the liquid nitrogen storage means to the rectification tower as a cold source for compressed air liquefaction, , A nitrogen gas extraction passage for taking out the vaporized nitrogen held in the rectification tower, the rectification tower has a dephlegmator section containing a condenser for producing a reflux liquid, and an inlet of the condenser And the exit is the first and second return It communicates with the upper part of the rectification column through a liquid passage, and the inlet of the nitrogen gas extraction passage is positioned at a position lower than the inlet of the first reflux liquid passage, so that the communication distance between both inlets is increased. The extension means is provided in the rectification column.

[Action]

This invention locates the inlet of the first reflux liquid passage at the top of the column where impure gas such as helium and hydrogen accumulates in the rectification column, and places the nitrogen gas removal passage at a position lower than the inlet of the passage. An extension means is provided for positioning the entrance of the take-out passage and for increasing the communication distance between the entrances.
Therefore, impure gases such as helium and hydrogen that are generated in the process of rectification and accumulated and accumulated in the column top of the rectification column are taken out from the inlet of the first reflux liquid passage and introduced into the condenser, Helium, which has a low boiling point in the condenser,
Hydrogen and the like remain vaporized, and only nitrogen is liquefied. Then, the above-mentioned impure gases such as helium and hydrogen are dumped into the outside atmosphere through the exhaust passage extending from the condenser.
As described above, in the present invention, since the inlet of the nitrogen gas extraction passage is positioned at a position lower than the inlet of the reflux liquid passage, impure gas such as helium and hydrogen accumulated and accumulated in the top of the rectification column is retained. Becomes difficult to mix in product nitrogen gas. In particular, in the present invention, the inlet of the reflux liquid passage,
In order to lengthen the communication distance with the inlet of the product nitrogen gas take-out path, since an extension means such as a shielding plate is provided,
The amount of product nitrogen gas taken out from the product nitrogen gas take-out passage increases, and impure gases such as helium and hydrogen that are sucked by the taken-out gas and accumulate and accumulate at the top of the rectification tower enter the product nitrogen gas. Even if an attempt is made to mix, the mixing is prevented by an extension means such as a shielding plate. Therefore, the impure gas such as helium and hydrogen is not mixed in the product nitrogen gas at all, and the product nitrogen gas becomes ultra-high purity.

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

〔Example〕

FIG. 1 shows an embodiment of the present invention. In the figure, 9 is an air compressor, 10 is a drain separator, 11 is a Freon cooler, and 12 is a set of two adsorption tubes. The adsorption column 12 is filled with a molecular sieve and serves to adsorb and remove H ₂ O and CO ₂ in the air compressed by the air compressor 9. Reference numeral 8 is a compressed air supply pipe for sending compressed air from which H ₂ O and CO ₂ have been adsorbed and removed. Reference numeral 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 removing means (adsorption cylinder) 12 is fed. Reference numeral 14 is a second heat exchanger, into which the compressed air that has passed through the first heat exchanger 13 is fed. Reference numeral 15 is a rectification column in which the tower top is connected to the dephlegmator section 21 having the condenser 21a, and the column section 22 is located below the condenser section 21a by the first and second heat exchangers 13 and 14. The compressed air that has been cooled to an ultra-low temperature and is sent through the compressed air supply passage 17 is further cooled, and a part of it is liquefied and stored as liquid air 18 at the bottom of the tower section 22, and only nitrogen in a gaseous state is provided on the upper ceiling of the tower section 22. It is supposed to be stored in the department. Reference numeral 23 is a liquid nitrogen storage means (tank), which feeds the internal liquid nitrogen (high-purity product) to the upper side of the tower portion 22 of the rectification tower 15 via the liquid nitrogen introduction passage 24a, Use as a cold source for the compressed air supplied to the inside. Explaining the rectification column 15 in more detail here, the rectification column 15 is divided into a dephlegmator section 21 and a tower section 22, and the condenser 21a in the dephlegmator section 21 has a column. A part of the nitrogen gas accumulated in the upper part of the portion 22 is sent in through the first reflux liquid passage 21b. The inside of the dephlegmator section 21 is in a reduced pressure state as compared with the inside of the tower section 22, and the stored liquid air (N ₂ 50 to 70%, O ₂ 30 to 50%) 18 at the bottom of the tower section 22 is an expansion valve. 19a with pipe 19
It is then sent through and 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. twenty five
Is a liquid level gauge, which controls the valve 26 according to the liquid level of the liquid air in the partial condenser 21 to control the supply amount of the liquid nitrogen from the liquid nitrogen storage means 23. The liquid nitrogen produced in the condenser 21a of the dephlegmator 21 is supplied to the upper part of the column part 22 of the rectification column 15 through the second reflux liquid passage 21c, and the liquid nitrogen is supplied. Liquid nitrogen is supplied from the nitrogen storage means 23 through the liquid nitrogen introduction passage 24a, and these flow downward in the tower portion 22 through the liquid nitrogen reservoir 21d, and in countercurrent with the compressed air rising from the bottom of the tower portion 22. It comes into contact with and is cooled to liquefy a part of it. In this process, the high boiling point component in the compressed air is liquefied and accumulated at the bottom of the tower part 22, and the nitrogen gas of the low boiling point component accumulates at the top of the tower part 22. 27 is a nitrogen gas take-out passage for taking out the nitrogen gas accumulated in the upper ceiling part of the tower part 22 of the rectification tower 15 as product nitrogen gas. Ultra-low temperature nitrogen gas is introduced into the second and first heat exchangers 14 and 13. It guides and heat-exchanges with the compressed air sent into it to bring it to room temperature and sends it to the main passage 28. In this case, at the uppermost part in the column part 22 of the rectification column 15, together with nitrogen gas, He (−269
° C.), since the H ₂ (-253 ° C.) or the like is accumulated, as in FIG. 2, the inlet 27a of the nitrogen gas takeout path 27 lower than the inlet 21e of the first reflux liquid passage 21b position is open, Only ultra-high-purity nitrogen gas that does not contain He and H ₂ etc. is taken out as product nitrogen gas. In order to promote this, a shielding plate (extending means) 21f having a droplet lower hole at the base is projected obliquely upward from the lower part of the inlet of the first reflux liquid passage 21b, and the nitrogen gas take-out inlet 27a and the first The communication distance with the inlet of the first reflux liquid passage 21b is lengthened, and thereby, due to the air flow generated when the product nitrogen gas flows into the passage 27, He, H ₂
The mixed nitrogen gas is prevented from mixing with the product nitrogen gas. The droplet drop hole of the shielding plate 21f has a function of flowing down the liquefied nitrogen gas component in the upper space of the shielding plate 21f. Also from the top of the condenser 21a above He, a gas vent passage 21g for escape of H ₂ or the like to the outside air and extends upward. 29 is a second and first heat exchanger for the vaporized liquid air in the dephlegmator 21.
A passage for feeding and cooling 14 and 13, 29a is a pressure holding valve. 30 is a backup system line, and a rectification tower 15
In order to make up for the shortage of product nitrogen gas flowing from the main passage 28 to the main passage 28, the liquid nitrogen in the liquid nitrogen storage means 23 is vaporized by the evaporator 31 so that a constant amount is constantly supplied to the main passage 28, and the air compression system line fails. When this is done, it has the function of supplying the entire amount of nitrogen gas consumed. In this case, the flow rate of the backup system line 30 is adjusted by the pressure adjusting valve 35 arranged at the downstream of the evaporator 31. An impurity analyzer 32 analyzes the purity of the product nitrogen gas sent to the main passage 28. When the purity is low, the valves 34 and 34a are operated to escape the product nitrogen gas to the outside as shown by arrow B. To act. The chain double-dashed line is a vacuum insulation box.

This apparatus produces product nitrogen gas as follows. That is, the air is compressed by the air compressor 9, the water in the air compressed by the drain separator 10 is removed, and it is cooled by the Freon cooler 11, and then sent to the adsorption cylinder 12 in that state, and the H _{2 in} the air is reduced. Adsorbs and removes O and CO ₂ . Then,
Compressed air from which H ₂ O and CO ₂ have been adsorbed and removed is cooled by the product nitrogen gas or the like fed from the rectification column 15 through the nitrogen gas extraction passage 27. The first and second heat exchangers 13 Then, it is sent to 14, 14 to be cooled to an ultra-low temperature, and then charged into the lower part of the tower section 22 of the rectification tower 15 in that state. Then, the input compressed air, the liquid nitrogen sent from the liquid nitrogen storage means 23 into the tower portion 22 of the rectification tower 15 via the liquid nitrogen introduction passage 24a and the liquid nitrogen overflowed from the liquid nitrogen reservoir 21d. They are brought into contact with each other and cooled, and a part thereof is liquefied and stored as liquid air 18 at the bottom of the tower section 22.
In this process, due to the difference between 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 the compressed air, is liquefied and nitrogen remains as a gas.
Then, the nitrogen remaining in this gas is removed from the nitrogen gas discharge passage.
It is taken out from 27 and sent to the second and first heat exchangers 14 and 13, where it is heated to near room temperature and sent out from the main passage 28 as product nitrogen gas. In this case, since the inside of the column section 22 of the rectification column 15 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 nitrogen gas take-out passage 27 is also high. . Therefore, it is advantageous when this product nitrogen gas is used as a purging gas or the like. Also, since the pressure is so high, a large amount of gas can be transported with a pipe of the same diameter, and when the transport amount is constant, it is possible to use a pipe with a small diameter, which saves equipment costs. It will be possible. Further, nitrogen gas containing a gas having a lower boiling point than nitrogen gas, such as H ₂ and He, accumulates at the top of the tower section 22. This gas flows as an impure gas together with a part of the nitrogen gas into the condenser 21a from the first reflux liquid passage 21b, separates from the liquefied nitrogen gas there, and escapes from the degassing passage 21g to the outside air. At that time, since the inlet 21e of the first reflux liquid passage 21b is located at a position higher than the inlet 27a of the nitrogen gas extraction passage 27 (top side of the tower portion 22), impurities such as H ₂ and He accumulated at the top are impure. The gas is likely to enter the first reflux liquid passage 21b, and the top portion is shielded by the shielding plate 21f projecting obliquely upward from the lower portion of the inlet 21e, and is drawn by the product nitrogen gas flowing into the nitrogen gas extraction passage 27. It is possible to prevent the impure gas from being mixed. As a result, the purity of the product nitrogen gas taken out from the nitrogen gas take-out passage 27 becomes extremely high. The liquid nitrogen condensed and liquefied on the upper surface of the shielding plate 21f is dripped into the lower rectification shelf 21h from the droplet lower hole at the base of the shielding plate 21f and collected. On the other hand, the liquid air 18 accumulated in the lower part of the tower section 22 of the rectification tower 15 is sent into the dephlegmator section 21 to cool the condenser 21a. By this cooling, the nitrogen gas fed into the condenser 21a from the upper part of the column part 22 of the rectification column 15 is liquefied to become the reflux liquid in the rectification column part 22, and the second reflux liquid passage 21c is formed. After that, it returns to the tower section 22 of the rectification tower 15. Then, the liquid air 18 that has finished cooling the condenser 21a is vaporized,
After being sent to the second and first heat exchangers 14 and 13 through the passage 29 to cool the heat exchangers 14 and 13, they are discharged into the air. The liquid nitrogen storage means 23 to the liquid nitrogen introduction passage 24
The liquid nitrogen fed into the tower section 22 of the rectification column 15 via a acts as a cold source for liquefying compressed air, and is itself vaporized to remove one of the product nitrogen gases from the nitrogen gas extraction passage 27. Taken out as a part. Thus, the liquid nitrogen storage means 23
The liquid nitrogen of is not discarded after it has finished its function as a cold source for liquefying compressed air, but is commercialized by being combined with high-purity nitrogen gas that uses compressed air as a raw material.
Used without waste.

FIG. 3 shows an example in which the extension means is formed by a pipe 21i. This pipe 21i is the inlet of the first reflux liquid passage 21b.
It projects obliquely upward from 21e toward the top of the tower 22. Therefore, the inlet 21e of the pipe 21i can have a sufficient communication distance from the inlet 27a of the product nitrogen gas outlet passage 27. Therefore, the impure gas such as H ₂ and He accumulated at the top of the tower can be effectively guided to the condenser 21a.

FIG. 4 shows a rectification shelf 21h located 3 to 5 steps below the reflux liquid reservoir 21d provided at the outlet of the second reflux liquid passage 21c shown in FIG.
An example in which a liquid nitrogen reservoir 21k for accumulating the liquid nitrogen from the liquid nitrogen introducing passage 24a is arranged below is shown. In this configuration, even if impurities are mixed in the liquid nitrogen in the liquid nitrogen storage means 23, the liquid nitrogen is sufficiently rectified in the process of passing through the rectification shelf 21h by 2 to 3 stages and has a purity. improves. For example,
Liquid nitrogen having a purity of O ₂ of 2 ppm has a high purity of O ₂ of 0.2 ppm or less.

FIG. 5 shows an example in which the center of the ceiling portion of the tower portion 22 in FIG. 1 is projected upward so that the nitrogen gas mixed with H ₂ and He is retained therein. With this configuration, it is possible to obtain the effect that nitrogen mixed with H ₂ and He has no influence on the removal of product nitrogen.

[Advantages of the Invention] The ultrahigh-purity nitrogen gas production apparatus of the present invention does not use an expansion turbine, but instead uses liquid nitrogen storage means such as a liquid nitrogen storage tank having no rotating part, so that the entire apparatus is There is no rotating part and no malfunction occurs. Moreover, since the liquid nitrogen storage tank is inexpensive, the cost of the entire device is also low, and since the supply amount of liquid nitrogen can be controlled instantaneously, the cooling supply amount of cold by the expansion turbine can be controlled (cooling by the expansion turbine). Control will cause a time delay)
Compared with, the purity of the product nitrogen gas becomes stable. Moreover, in the device of the present invention, in the rectification column, the inlet of the first reflux liquid passage is positioned at the top of the column where impure gases such as helium and hydrogen are accumulated, and nitrogen is provided at a position lower than the inlet of the passage. An extension means is provided for positioning the inlet of the take-out passage of the gas take-out passage and for increasing the communication distance between the two inlets. Therefore, impure gases such as helium and hydrogen that are generated in the process of rectification and accumulated and accumulated in the column top of the rectification column are taken out from the inlet of the first reflux liquid passage and introduced into the condenser, In the condenser, helium, hydrogen and the like having a low boiling point are kept in a vaporized state, and only nitrogen is liquefied. Then, the above-mentioned gaseous impurities such as helium and hydrogen are discharged into the atmosphere of the outside air through the exhaust passage extending from the condenser. As described above, in the present invention, since the inlet of the nitrogen gas extraction passage is positioned at a position lower than the inlet of the reflux liquid passage, impure gas such as helium and hydrogen accumulated and accumulated in the top of the rectification column is retained. Becomes difficult to mix in product nitrogen gas. Particularly, in the device of the present invention,
Since an extension means such as a shielding plate is provided to increase the communication distance between the inlet of the reflux liquid passage and the inlet of the product nitrogen gas extraction passage, the product nitrogen gas extracted from the product nitrogen gas extraction passage is provided. Even if an impure gas such as helium or hydrogen that is sucked into the taken-out gas and accumulated and accumulated at the top of the rectification tower is mixed in the product nitrogen gas, a means for extending the shielding plate, etc. Therefore, the mixture is prevented. Therefore, the impure gas such as helium and hydrogen is not mixed in the product nitrogen gas, and the product nitrogen gas becomes ultra-high purity.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention, FIGS. 2 and 3 are block diagrams showing a modified example of the column top, and FIG. 4 is a block diagram showing a modified example of a liquid nitrogen reservoir, and FIG. The figure is a configuration diagram of a modified example in which a protrusion is provided at the top of the tower. 9 ... Air compressor, 12 ... Removal means, 13,14 ... Heat exchanger, 15 ... Fractionation tower, 19 ... Liquid air intake passage, 19a ...
Expansion valve, 21 ... decompressor section, 21a ... condenser, 21b ... first
Reflux liquid passage, 21c ... second reflux liquid passage, 21d ...
Reflux liquid reservoir, 21e …… Inlet, 21i …… Pipe, 21f …… Rectifier plate, 21h …… Rectification shelf, 21k …… Liquid nitrogen reservoir, 22 …… Tower section,
23 ... Liquid nitrogen storage means, 24a ... Liquid nitrogen introduction passage, 2
7 …… Nitrogen gas extraction passage, 27a …… Inlet

Claims (4)

[Claims] 1. An air compression means for compressing air taken from the outside, a removal means for removing carbon dioxide gas and water in the compressed air compressed by the air compression means, and a compression through this removal means. Heat exchange means for cooling the air to an ultra-low temperature,
A rectification column that liquefies a part of the compressed air cooled to ultra-low temperature by this heat exchange means and stores it inside to hold only nitrogen as a gas, liquid nitrogen storage means for storing liquid nitrogen, and this liquid nitrogen storage means Liquid nitrogen in the liquid nitrogen introduction passage as a cold source for liquefaction of compressed air to the rectification column, and a nitrogen gas extraction passage for taking out the vaporized nitrogen held in the rectification column, the rectification column Has a condenser part containing a condenser for producing reflux liquid, and the inlet and outlet of the condenser communicate with the upper part of the rectification column through first and second reflux liquid passages, The inlet of the nitrogen gas extraction passage is positioned lower than the inlet of the first reflux liquid passage, and extension means for increasing the communication distance between the inlets is provided in the rectification column. Ultra-high-purity nitrogen gas production equipment. 2. The ultra-high purity according to claim 1, wherein the extending means is formed by a pipe projecting from the inlet of the first reflux liquid passage toward the top of the rectification column. Nitrogen gas production equipment. 3. The extension means is formed by a shield plate having a droplet lower hole provided so as to project from a lower portion of an inlet of the first reflux liquid passage to a front side of the inlet. Ultra-high purity nitrogen gas production equipment. 4. A liquid nitrogen reservoir for accumulating liquid nitrogen from the liquid nitrogen introduction passage under a rectification shelf located at a plurality of stages below the reflux liquid reservoir provided at the outlet of the second reflux liquid passage. The ultra-high-purity nitrogen gas production apparatus according to claim 1, wherein