JP3299069B2 - Air low-temperature separation apparatus and separation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in technology for economically producing helium gas used in an optical fiber manufacturing process or optical glass manufacturing process together with at least nitrogen gas.

[0002]

2. Description of the Related Art Generally, oxygen (O ₂ ), nitrogen (N ₂ ), helium (H
e) is used, of which helium is only present at 5.2 PPM in the natural air and cannot be separated from natural air at economically attractive prices and leaves limited areas At present, it is separated from natural gas, liquefied, and imported into Japan. Therefore,
In recent years, it has been demanded that helium (He) after being used in the optical fiber manufacturing process and the like be purified again and recycled.
As disclosed in JP-A-5-172457 and the like, a step of cooling helium gas containing impurities collected in a manufacturing process, a step of separating impurities liquefied by cooling from helium gas, and a step of gas-liquid separation. For purifying helium through the step of discharging the liquid component, or compressing and cooling helium gas containing impurities recovered in the manufacturing process as disclosed in JP-A-6-210157. After that, the mixture is introduced into a filtration step to remove oil, moisture, and particulate matter in the cooled helium gas, and further introduced into a purification device selectively configured from a membrane separation system, an adsorption system, and the like. There has been proposed a method of purifying helium by removing impure high-boiling components in gas.

[0003]

All of the conventional helium refining methods are directed to a raw material gas containing 80% or more of helium and containing air as the remaining impurity. Since it is manufactured, a separate manufacturing facility is required to obtain nitrogen and oxygen other than helium, and low-concentration helium gas containing 50% or less of helium, which has been excluded from repurification, has other impurities. At present, it is treated as exhaust gas. The present invention has been made in view of the above-described circumstances, and effectively utilizes low-concentration helium gas that has been treated as exhaust gas to economically produce helium gas that can be reused in a manufacturing process together with at least nitrogen. It is an object to provide a low-temperature air separation apparatus and a separation method that can be manufactured.

[0004]

Means for Solving the Problems] Features Configuration of Air cryogenic separation apparatus according to the present invention for achieving the above object, according to claim 1
As described in the above, compression means for compressing the mixed raw material gas of low-concentration helium and air, cooling means for cooling the mixed raw material gas compressed by the compression means to near the liquefaction point, and cooled by the cooling means A rectification tower that rectifies and separates the mixed raw material gas to extract at least liquid nitrogen as a product, a condenser that condenses a mixed gas of nitrogen and helium that is taken out from the top of the rectification tower, and condenses and liquefies the condenser. comprising a gas-liquid separator, and a helium Sosei tower for taking out the uncondensed gas to and rectification helium gas to gas-liquid separation in the gas-liquid separator as a product for separating the liquid nitrogen, the helium crude Rectification tower
The uncondensed gas introduced into the helium crude fractionator
Heat of liquid nitrogen with liquid nitrogen obtained from the rectification column
A condenser that condenses and liquefies by replacement is provided,
Part of the liquid nitrogen obtained from the rectification column is
Subcooling before being introduced into the condenser of the crude rectification column.
A supercooler, and liquid nitrogen supercooled by the subcooler.
And an expansion valve for expanding the pressure to below atmospheric pressure .

According to the characteristic structure of the low-temperature air separation apparatus of the present invention,
In the optical fiber manufacturing process, optical glass manufacturing process, etc.
Liquefied mixed source gas of low concentration helium and air collected
Into the rectification column while cooling to near the point.
Mixed by mixing low-concentration helium with air.
Even if the concentration of helium in the source gas decreases,
By the rectification separation in the rectification column, which is the primary concentration step, mixing
Efficient separation of helium, nitrogen, and oxygen in the mixture gas
At least the liquid nitrogen produced in the process.
Element can be removed from the rectification column as a product. So
And nitrogen and helium removed from the top of the rectification column.
Helium secondary condensing process
Nitrogen and helium
From the mixed gas to separate and condense and liquefy nitrogen.
Um purity can be increased. Furthermore, gas-liquid separation means
The uncondensed gas separated in
Helium crude rectification column
The nitrogen content in the uncondensed gas is separated by rectification in
To produce helium gas with higher purity
Can be. Further, the helium crude rectification column provided with
Uncondensed gas introduced into the helium crude rectification column by the condenser
And indirect heat exchange between liquid nitrogen and
Efficiently condenses the nitrogen content of the uncondensed gas from the
It can be condensed. The helium crude fractionation tower
Liquid supercooled by a subcooler before being introduced into the condenser
By expanding the nitrogen below atmospheric pressure, the helicopter
Cryogenic cooling source required for the rectifier
Obtainable.

As a result, the air cryogenic separation apparatus of the present invention has
According to the characteristic configuration, optical fiber manufacturing process and optical glass
Low concentration that is treated as exhaust gas after use in the manufacturing process, etc.
Helium gas can be effectively used and reused in the manufacturing process
High purity helium gas with at least nitrogen efficiently
It can be manufactured, and is manufactured from a helium crude rectification column.
The purity of helium can be increased efficiently,
Furthermore, the uncondensed gas introduced into the helium crude fractionator
Nitrogen condensation and liquefaction can be performed more efficiently
In addition, it can be implemented advantageously in terms of equipment.

[0007] The first characterizing feature of the air low-temperature separation method of the present invention, as set forth in claim 2, compressing the mixed raw material gas of low concentration of helium and air compression means, the compressed mixed feed gas After cooling to the vicinity of the liquefaction point by the cooling means, the mixture is introduced into the lower part of the rectification tower, and the mixed gas of nitrogen and helium which is rectified and separated from the mixed raw material gas and taken out from the top by the rectification tower is passed through a condenser. The liquid nitrogen is introduced into a liquid separator, and the liquid nitrogen gas-liquid separated by the gas-liquid separator is introduced as a reflux liquid into the rectification section at the uppermost stage of the rectification column. The condensed gas is introduced into the lower part of the helium crude rectification column, and the helium gas rectified and separated in the helium crude rectification column is produced and taken out from the top, and several stages from the top of the rectification part of the rectification column removed liquid nitrogen as a product from the rectification unit below the rectification column Liquid nitrogen taken from the rectification unit
Part of the element is subcooled by a subcooler, and then subcooled by the subcooler.
Expand the cooled liquid nitrogen to below atmospheric pressure with an expansion valve
Then, the condenser provided in the helium crude rectification column
The point is to introduce .

According to the first characteristic configuration of the low-temperature air separation method of the present invention, the mixed raw material gas of low-concentration helium and air collected in the optical fiber manufacturing process, the optical glass manufacturing process, and the like is cooled to near the liquefaction point. Even if the concentration of helium in the mixed raw material gas is reduced by mixing the low-concentration helium with air by introducing into the rectification column, the rectification separation in the rectification column becomes the primary concentration step of helium. Sometimes helium, nitrogen and oxygen in the mixed raw material gas can be efficiently separated, and a part of the liquid nitrogen produced in the process after fractionating and separating low boiling components has a high boiling point. The product can be taken out from the rectification section several stages below the top of the rectification section of the rectification column in a state where the amount of oxygen as a component is small. Next, the mixed gas of nitrogen and helium taken out from the top of the rectification column is introduced into a condenser and a gas-liquid separator which is a secondary helium concentration step, so that the mixed gas of nitrogen and helium is The liquid is condensed and liquefied and separated.
It is necessary to introduce liquid nitrogen as a reflux liquid from the outside by increasing the purity of helium and introducing liquid nitrogen condensed and liquefied in the gas-liquid separator as a reflux liquid to the top of the rectification section of the rectification column. Rectification in the rectification section can be performed economically. Further, the uncondensed gas separated by the gas-liquid separation means is introduced into a helium crude rectification column that is a helium tertiary concentration step, whereby nitrogen in the uncondensed gas is rectified by the helium crude rectification column. The helium gas having high purity can be produced by separating the components. Ma
In addition, from the rectification section several stages below the rectification section top stage of the rectification column
Focusing on the cooling of the extracted liquid nitrogen, this liquid nitrogen
Was supercooled with a supercooler, and crude helium was used as a cold source.
By introducing it to the condenser of the distillation tower, it can
Helium crude rectification column without introducing liquid nitrogen
The nitrogen content of uncondensed gas introduced into
It is possible to efficiently condense and liquefy by heat exchange.
Furthermore, before being introduced into the condenser of the helium crude rectification column,
Expand the liquid nitrogen supercooled by the subcooler to below atmospheric pressure.
Is necessary in the condenser of the helium crude rectification column.
The required cryogenic heat source can be easily obtained.

As a result, according to the first characteristic configuration of the low-temperature air separation method of the present invention, low-concentration helium gas, which has been treated as exhaust gas after use in an optical fiber manufacturing process or an optical glass manufacturing process, is effectively used. Te, along with a reusable purity helium gas in the manufacturing process can be manufactured together with at least nitrogen efficiently and economically, it is possible to increase the purity of the product nitrogen taken from the rectification column, f
Nitrogen condensation of uncondensed gas introduced into the crude rectifier
Liquefaction can be performed more efficiently and equipment
However, it can be implemented advantageously.

A second characteristic configuration of the low-temperature air separation method according to the present invention is the above-mentioned low-temperature air separation method.
In the first feature structure, and further, in terms of the product after it is used as a cooling source directing helium gas taken from the top of the helium Sosei column to the subcooler and the cooling means. The second characteristic configuration of the low-temperature air separation method of the present invention
According to the helicopter removed from the top of the helium crude fractionator,
Gas to the supercooler and cooling means to cool them
For use as a source, for subcoolers and heat exchange means
There is no need to introduce a separate cold source from outside. as a result,
According to the second characteristic configuration of the low-temperature air separation method of the present invention,
In addition to the effect of the first characteristic configuration of the air / low temperature separation method,
Mugas and nitrogen can be produced more economically.

A third characteristic configuration of the low-temperature air separation method according to the present invention is the above-mentioned low-temperature air separation method.
In the first and second characteristic configurations, the helium gas taken out from the top of the helium crude rectification column is purified by a membrane separator to obtain a product. The air cryogenic separation method of the present invention
According to the third characteristic configuration, the helium crude fractionation column is taken from the top.
The purified helium gas is purified by a membrane separator.
Removes high-boiling components, which are impurities in the product helium gas.
You can leave. Third method of the low-temperature air separation method of the present invention
According to the characteristic configuration, the first and second characteristics of the low-temperature air separation method
In addition to the effect of the configuration, increase the purity of the product helium gas
Can be

[0012] The fourth characteristic feature of the air low-temperature separation method of the present invention, as set forth in claim 5, the air low-temperature separation process
In the first to third characteristic configurations, the helium gas taken out of the membrane separator is compressed and cooled, then separated at a low temperature by an adsorption separator, and returned to room temperature to obtain a product. Book
According to the fourth aspect of the low-temperature air separation method of the present invention,
Helium gas extracted from the separator is compressed and separated by adsorption
Of high-boiling components, which are impurities in the product helium gas,
Once cooled to a low temperature suitable for
The product helium gas is introduced into the separator by the adsorption separator.
To the cryogenic separation more efficient better high-boiling components which is an impurity in the
Can be Fourth feature of the low-temperature air separation method of the present invention
According to the configuration, the first to third characteristic configurations of the low-temperature air separation method
In addition to the effects of
Can be planned.

[0013] The fifth characteristic configuration of the air low-temperature separation method of the present invention, as set forth in claim 6, the air low-temperature separation process
In the first to fourth characteristic configurations, a step of supplying an exhaust gas containing the remaining helium gas subjected to membrane separation by the membrane separator to the mixed raw material gas is provided. Of the present invention
According to a fifth characteristic configuration of the low-temperature air separation method, the membrane separation is performed.
Helium still remains in the exhaust gas separated by membrane
The gas can be reused as part of the mixed source gas
You. According to the fifth characteristic configuration of the low-temperature air separation method of the present invention.
For example, in addition to the effect of the fourth characteristic configuration of the low-temperature air separation method,
Helium gas remaining in the exhaust gas separated by membrane in the membrane separator
Helium gas by reusing
Can improve the efficiency of collecting waste gas.

[0014]

First Embodiment FIG. 1 shows recovered air containing a large amount of helium (for example, about 5%) used in an optical fiber manufacturing process or the like and natural air (5.2 PPM of natural air is contained in natural air). 2 shows a flow diagram of a low-temperature air separation apparatus for purifying and separating product helium gas, product nitrogen gas, and product oxygen gas using helium as a raw material gas, and a method for separating the same.

Then, air containing about 5% of helium (He) recovered after being used in the optical fiber manufacturing process is 1,000 Nm ³ / h (50 Nm in terms of 100% helium).
³ / h) is removed by the filter 1 and then introduced into the pipe P2 via the pipe P1.
0Nm ³ / h is pipe P2 after dust is removed by filter 2.
And mixed with air of 1,000 Nm ³ / h containing about 5% of helium (He), and a mixed material gas of 2,500 Nm ³ / h containing 2% of helium (in a steady state as described later, It becomes a mixed source gas of 2,503 Nm ³ / h, and the helium amount also increases to about 51 Nm ³ / h.)
Becomes And 2,500 containing this helium 2%
The mixed raw material gas of Nm ³ / h is compressed to about 7.3 ATA by a compressor 3 which is an example of a compression means, and cooled to about 5 ° C. by a cooler 4 which is a pre-cooling means via a pipe P3. After removing carbon dioxide gas and moisture in a decarburizer / dryer 5 which is an example of an adsorption means via P4, the carbon dioxide gas and water are introduced into a heat exchanger 6 which is an example of a cooling means via a pipe P5. Heat is exchanged indirectly with the nitrogen gas, product helium gas and waste gas in a countercurrent state, and finally cooled to near the liquefaction point.

A part of the mixed raw material gas to be cooled is taken out from the middle of the heat exchanger 6 through a pipe P6, expanded by an expansion turbine 7, and cooled by a low-temperature separation device (cold box) A.
To the low pressure rectification column 8 through the pipe P7
The remaining mixed material gas is further cooled to near the liquefaction point (about -170 ° C.) in the heat exchanger 6 and then passed through the pipe P8 to the intermediate pressure rectification tower 9. Introduced at the bottom.

Most of the oxygen and part of the nitrogen in the mixed raw material gas introduced into the lower part of the intermediate pressure rectification column 9 are rectified and liquefied, and are formed at the bottom of the medium pressure rectification column 9 as an oxygen-enriched liquid. Almost all of the remaining oxygen and nitrogen and helium are stored in the intermediate-pressure rectification tower 9 and rectified by gas-liquid contact with a reflux liquid described below in the rectification section of the medium-pressure rectification tower 9. A mixed gas of nitrogen and helium at a pressure of about 7 ATA is taken out from the top of the medium pressure rectification column 9 through a pipe P9 and introduced into the condenser 10. On the other hand, liquid oxygen stored at the bottom of the low-pressure rectification column 8 described later is taken out through the pipe P10 and introduced into the condenser 10,
The two are indirectly heat-exchanged with each other, and the liquid oxygen is vaporized and returned to the low-pressure rectification column 8 via the pipe P11. The mixed gas of nitrogen and helium is cooled and condensed, and guided to the pipe P12 for gas-liquid separation. Introduced into the vessel 11, from the bottom 99.95% nitrogen,
Liquid nitrogen of 0.05% helium is led out through the pipe P13, returned to the uppermost stage of the rectification section of the intermediate pressure rectification tower 9, and used as the above-mentioned reflux liquid. On the other hand, a mixed gas of 90% nitrogen and 10% helium is led out from the top of the gas-liquid separator 11 via a pipe P14, and the pressure is about 7 ATA and the temperature is about- 176 ° C
Introduced in.

The liquid nitrogen taken out from the rectification section several steps below the top of the rectification section of the intermediate pressure rectification column 9 at a pressure of about 7 ATA by a pipe P15 is supplied to a subcooler 13 to produce a product nitrogen gas, The product is supercooled by indirect heat exchange with product nitrogen gas, waste gas and crude helium gas, taken out through a pipe P16, partially expanded to a pressure of about 1.25 ATA by an expansion valve V1 inserted into the pipe P17, and heated to a temperature of about 1.25 ATA. -194 ° C., the nitrogen 90 introduced into the condenser a located in the middle of the rectifying section of the helium crude rectifying column 10 and introduced through the pipe P14.
%, Helium 10% indirect heat exchange. By this indirect heat exchange, the nitrogen component in the mixed gas is mainly condensed and flows down, and becomes a reflux liquid in the rectification section below the condenser a.

The mixed gas of nitrogen and helium rising through the condenser a of the helium crude rectification column 12 is supplied to the condenser a.
The nitrogen component is mainly condensed and flows down by the rectification section located above the rectification section and the condenser b located further above the rectification section, and the entire rectification of the helium crude rectification column 12 located below the condenser b It becomes a reflux liquid of the distillation section, and finally, liquid nitrogen of 99.95% of nitrogen and 0.05% of helium is formed at the bottom of the crude rectification column 12 of helium. The liquid nitrogen of 99.95% of nitrogen and 0.05% of helium is led out from the bottom of the helium crude rectification column 12 through a pipe P18, and is introduced into the uppermost rectification section of the medium pressure rectification tower 9 via a pipe P19. Then, it becomes a reflux liquid of the intermediate pressure rectification column 9.

The liquid nitrogen distributed by the pipe P20 branched from the pipe P17 as a cold source of the condenser b of the helium crude rectification column 12 has a pressure of about 0.2 ATA (by an expansion valve V2 inserted into the pipe P20). (Atmospheric pressure or lower), the temperature is reduced to about -207 ° C, and the condenser b
The nitrogen gas in the mixed gas that is introduced into the ascending gas is mainly condensed and flows down as a liquid, and is used as a cold source of the condenser b. After being converted into nitrogen gas and taken out by the pipe P21, heat exchange is performed. The gas is introduced into the vessel 6, is brought to room temperature by indirect heat exchange with the mixed raw material gas, and is exhausted to the atmosphere by the vacuum pump 14 via the pipe P22.

The helium crude rectification column 1 passes through the pipe P14.
The mixed gas of 10% helium and about 90% nitrogen introduced into the lower part of 0 is rectified by the helium crude rectification column 10 as described above to become a crude helium gas of about 95% helium and about 5% nitrogen, At a temperature of −204 ° C. and a pressure of about 6.9 ATA, it is taken out from the top of the helium crude rectification column 12 by a pipe P23 and used as a cold source of the subcooler 13 and then a pipe P
The crude helium gas is taken out at the pipe P25 and taken out at the pipe P25, and is taken out to the membrane separator 15 at a pressure of about 6.8AT.
Introduced about 47 Nm ³ / h in A, helium about 99%, nitrogen about 1% of the pressure helium gas of about 44 nm ³ / h is about 1.
Helium gas compressor 16 taken out from pipe P by 5ATA
, And the pressure is increased to the required pressure and supplied to the user. About ³ Nm ³ / remaining exhaust gas from the membrane separator 15
h is introduced into the pipe P2 by the pipe P26 and added as a helium source.

Next, the separation and production of oxygen gas and nitrogen gas using the above-mentioned low-temperature apparatus for purifying and separating helium will be described. The oxygen-enriched liquid collected at the bottom of the intermediate-pressure rectification tower 9 is introduced into the supercooler 13 via a pipe P27, and is indirectly heat-exchanged with product nitrogen gas, product nitrogen gas, waste gas and crude helium gas. After being supercooled, supercooler 1
3 is extracted by a pipe P28, expanded by an expansion valve V3 inserted into the pipe P28, and then introduced into a rectification section of the low-pressure rectification tower 8 which is lower than a connection position of the pipe P7. The mixed raw material gas introduced through the low pressure rectification column 8 together with the mixed raw material gas, and the liquid nitrogen taken out from the middle stage of the rectification section of the medium pressure rectification column 9 through the pipe P29 is passed through the supercooler 13 After being supercooled by indirect heat exchange with the product nitrogen gas, product nitrogen gas, waste gas and crude helium gas, it is taken out from the supercooler 13 by a pipe P30 and expanded by an expansion valve V4 inserted into the pipe P30. Liquid nitrogen which is introduced into the low pressure rectification tower 8 slightly above the connection position of the pipe P7 to become a reflux liquid, and which is taken out of the medium pressure rectification tower 9 by the pipe P15 and supercooled by the supercooling 13 Is piping P Extracted in 6, some of the pipe P
At 17, it is used as a cold source for the condensers a and b of the helium crude rectification column 12, and the remainder is expanded by an expansion valve V 5 via a pipe P 31, and then introduced into the uppermost rectification section of the low-pressure rectification column 8. Then, it flows down as a reflux liquid, is rectified by gas-liquid contact with the reflux liquid, and is stored as liquid oxygen at the bottom. The stored liquid nitrogen becomes a cold source of the condenser 10 and is vaporized by itself and returned to the low-pressure rectification column 8 again. Approximately 450 Nm ³ / h is taken out at about 1.6 ATA, and heat exchange with the mixed raw material gas is carried out in the heat exchanger 6 to reach normal temperature.
After being taken out by the pipe P33, it is compressed by the compressor 17 and supplied to the use destination.

The mixed raw material gas and raw material liquid introduced into the low-pressure rectification column 8 are rectified and separated in the rectification section, and the above-mentioned liquid oxygen is produced at the bottom, and about 980 Nm ³ / h of nitrogen gas is produced at the top. Of which, the product nitrogen gas has a pressure of about 1.3A
The TA is taken out by the pipe P34 and merges with the nitrogen gas taken out of the condenser a of the helium crude rectification column 12 by the pipe P41. The combined nitrogen gas is used as a cold source of the supercooler 13 and then taken out through a pipe P35, exchanges heat with the mixed raw material gas in the heat exchanger 6 to reach room temperature, and is taken out through a pipe P36. It is introduced into the compressor 18 and supplied to the use destination.

The waste gas is taken out of the low-pressure rectification column 8 from a position slightly above the position where the liquid nitrogen was introduced in the above-mentioned pipe P30 by a pipe P37, and becomes a cold source of the supercooler 13, and becomes a cold source of the pipe P38.
And exchanged heat with the mixed raw material gas in the heat exchanger 6 to reach a normal temperature, taken out by the pipe P39, used as a regenerating gas of the switchable decarburizer / dryer 5, and then released to the atmosphere by the pipe P40. .

[Second Embodiment] In the first embodiment, the purity of helium gas extracted as a product is as follows: helium He: 99%, nitrogen N ₂ : 1%.
And can be used for manufacturing light glass, but in general,
Low purity for other uses. Therefore, in purifying the high-purity helium gas used for general use, as shown in FIG. 2, the helium gas of 99% of helium He and 1% of nitrogen N ₂ is entirely supplied from the compressor 16 in the first embodiment (FIG. 2). Part may be taken out) through a pipe P50, introduced into a heat exchanger 6, cooled by indirect heat exchange with countercurrent helium gas, oxygen gas, nitrogen gas and waste gas.
1 and purified by alternately using a pair of low-temperature adsorbers 19A and 19B by opening and closing control of valves V6 to V9, to make high-purity helium gas of helium He: 99.9999%, taken out by piping P52, and heat exchange. It is returned to the vessel 6 to be at normal temperature, taken out through the pipe P53, and supplied to the place of use. The rest of the configuration is the same as that of the first embodiment, and the same components are denoted by the same reference numerals, and description thereof is omitted.

[Third Embodiment] In the first embodiment described above, a mixed raw material gas containing helium He of 2% and having a concentration of 2,500 Nm ³ / h (in a steady state, a mixed raw material gas of 2,503 Nm ³ / h) is used. A part was taken out from the middle of the heat exchanger 6 and expanded by the expansion turbine 7 to generate cold heat, which was introduced into the low-pressure rectification column 8 as a cold heat source in the low-temperature separation device (cold box) A. The amount of recovered helium gas was reduced by the amount of gas used for the cold heat source. Therefore, as shown in FIG.
A mixed material gas of 2,500 Nm ³ / h containing 2% of helium He (a mixed material gas of 2,503 Nm ³ / h in a steady state) is introduced into the heat exchanger 6, and helium gas, nitrogen gas and The indirect heat exchange with the waste gas is carried out, and the whole amount is cooled to near the liquefaction point and introduced into the medium pressure rectification column 9. The oxygen-enriched liquid is supplied to the bottom of the medium pressure rectification column 9, At the top of 9, a mixed gas of nitrogen and helium is produced. Then, the oxygen-enriched liquid at the bottom of the intermediate-pressure rectification column 9 is taken out through the pipe P60, introduced into the supercooler 13 and supercooled, then taken out through the pipe P61, and about 3 ATA is introduced through the expansion valve V10 inserted into the pipe P61. Is introduced to the condenser 10 after being expanded to the intermediate pressure of
Exchanges heat with the mixed gas of nitrogen and helium introduced into the heat exchanger, and the oxygen-enriched liquid becomes waste gas, is introduced into the heat exchanger 6 via the pipe P62, and exchanges heat with the mixed raw material gas flowing in the opposite direction. The pipe is taken out from the middle of the pipe P63, introduced into the expansion turbine 20, expanded from the intermediate pressure to a pressure close to the atmospheric pressure to generate cold heat, returned to the heat exchanger 6 via the pipe P64, and cooled by the low-temperature separation device (cold box). ) After being used as a cold heat source in A, it was brought to room temperature, taken out by piping P39, and thereafter the same as in the first embodiment.

The mixed gas of nitrogen and helium taken out from the top of the medium pressure rectification column 9 is supplied to a condenser 10, a gas-liquid separator 11, a helium crude rectification column 12,
Subcooler 13, heat exchanger 6, membrane separator 15, and compressor 1
Although supplied to the destination through 6, the amount of the recovered product helium gas can be increased as compared with the first embodiment. If oxygen is also required at the same time, the oxygen 30 which is taken out of the decarburizer / dryer 5 via the pipe P40 as liquid oxygen if necessary.
% To 40% of the exhaust gas may be supplied in the form of oxygen gas through a membrane separator or an adsorption separator. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

[Other Embodiments] In each of the above embodiments, the mixed source gas of low-concentration helium containing about 5% helium and air has been described as an example. However, even if the recovered helium is of high purity (80%), it is mixed with it. If the amount of air generated is large and the helium concentration of the mixed raw material gas can be about 15% to 0.05%, preferably about 10% to 0.1%, helium having a purity that can be reused in the manufacturing process The gas can be produced efficiently and at least economically at a reasonable price with nitrogen. 2. In the case of producing helium, nitrogen and oxygen from a mixed source gas of low-concentration helium and air as in the above-described embodiment, a double rectification column is used. When producing and nitrogen, a single rectification column is used. 3. In the above embodiment, the helium crude rectification column 12 having two condensers a and b has been described as an example, but the helium crude rectification column 12 having one or three or more condensers is described. May be used.

In the claims, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the configuration of the attached drawings.

[Brief description of the drawings]

FIG. 1 is a flow diagram showing a low-temperature air separation apparatus and a separation method thereof according to a first embodiment.

FIG. 2 is a flow diagram showing a low-temperature air separation apparatus and a separation method thereof according to a second embodiment.

FIG. 3 is a flow diagram showing a low-temperature air separation apparatus and a separation method according to a third embodiment.

[Explanation of symbols]

 Reference Signs List 3 compression means (compressor) 4 pre-cooling means (cooler) 5 adsorption means (decarburizer / dryer) 6 cooling means (heat exchanger) 7 expansion turbine 8 low pressure rectification tower 9 rectification tower (medium pressure rectification tower) 10) Condenser 11 Gas-liquid separator 12 Helium crude fractionator 13 Subcooler 14 Vacuum pump 15 Membrane separator 16 Helium gas compressor 17 Oxygen gas compressor 18 Nitrogen gas compressor 19A Adsorption separator (low temperature adsorber) 19B adsorption separator (low temperature adsorber) a condenser b condenser

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shunzo Sasaki 2-13-8 Shimbashi, Minato-ku, Tokyo Inside Sumisho Finegas Co., Ltd. (72) Inventor Yoichi Murakami 2- 13-8 Shimbashi, Minato-ku, Tokyo Sumisho (56) References JP-A-62-41572 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F25J 1/00-5/00

Claims (6)

(57) [Claims] Compression means (3) for compressing a mixed material gas of low-concentration helium and air, and cooling means (6) for cooling the mixed material gas compressed by the compression means (3) to near a liquefaction point. A rectification tower (9) for rectifying and separating at least liquid nitrogen as a product by rectifying and separating the mixed raw material gas cooled by the cooling means (6); and nitrogen extracted from the top of the rectification tower (9). Condenser (1) that condenses a mixed gas of helium and helium
0), a gas-liquid separator (11) for separating liquid nitrogen condensed and liquefied in the condenser (10), and the gas-liquid separator (11)
Bei a helium SoseiTometo (12) for taking out the uncondensed gas to gas-liquid separation in the rectification to helium gas as a product
The helium crude fractionator (12) is provided with the helium crude fraction.
The nitrogen content of the uncondensed gas introduced into the distillation tower (12) is
By indirect heat exchange with liquid nitrogen obtained from the rectification column (9)
Condensers (a, b) for condensing and liquefying
Ri, a portion of the liquid nitrogen obtained from the rectification column (9), wherein
The helium crude rectification tower (12) is led to the condensers (a, b).
A subcooler (13) for subcooling before entering
The liquid nitrogen supercooled by the subcooler (13)
An air low-temperature separation device provided with an expansion valve (V2) that expands downward . 2. A mixed raw material gas of low-concentration helium and air is compressed by a compression means (3), and the compressed mixed raw material gas is cooled to a vicinity of a liquefaction point by a cooling means (6). 9), the mixed gas of nitrogen and helium which is rectified and separated from the mixed raw material gas in the rectification column (9) and taken out from the top is passed through a condenser (10) to a gas-liquid separator (1).
1), and the liquid nitrogen gas-liquid separated by the gas-liquid separator (11) is introduced as a reflux liquid into the rectification tower (9) at the uppermost stage of the rectification section. ) the uncondensed gas to gas-liquid separation is introduced into the lower portion of the helium SoseiTometo (12), take out the rectification separated helium gas in the helium SoseiTometo (12) as a product from the top together, the rectifying section liquid nitrogen from the rectification unit under several stages from the top of the rectification column (9) Eject the product was taken out from said rectifying part of the rectification column (9) liquid Nitrification
A part of the element is supercooled by a supercooler (13),
Liquid nitrogen supercooled by the pressure vessel (13) by the expansion valve (V2)
After expanding to below atmospheric pressure, the helium crude rectification
A low-temperature separation method for introducing air into condensers (a, b) provided in a tower (12) . 3. The helium gas extracted from the top of the helium crude fractionator (12) is introduced into a subcooler (13) and a cooling means (6) and used as a cold source to produce a product. 3. The method for low-temperature separation of air according to 2 . 4. The method for low-temperature separation of air according to claim 2, wherein the helium gas taken from the top of the helium crude fractionator (13) is purified by a membrane separator (15) to produce a product. 5. After compressing and cooling the helium gas taken out of the membrane separator (15), the adsorption separator (19).
The low-temperature air separation method according to claim 4 , wherein the low-temperature separation is performed at A, 19B) and the temperature is returned to room temperature to obtain a product. 6. The low-temperature air separation method according to claim 4 , wherein a step of supplying an exhaust gas containing the remaining helium gas that has undergone membrane separation in the membrane separator (15) to the mixed raw material gas is provided. .