JP4417142B2 - Air separation method and apparatus used therefor - Google Patents

Description

  The present invention relates to an air separation method and an apparatus used therefor.

Generally, a cryogenic air separation device liquefies air by cold and rectifies and separates each component (N ₂ , O ₂ , Ar, etc.), and then takes out the desired component in a gaseous or liquid state. As a cold source, cold energy such as an expansion turbine is used. As such a cryogenic air separation apparatus, there is a high-purity nitrogen gas production apparatus using an expansion turbine 30 as shown in FIG. In the figure, 11 is a raw material air compressor for compressing raw material air, 12 is a pair of two adsorption towers, and water (H ₂ O) and carbon dioxide in compressed air compressed by the raw material air compressor 11 It acts to adsorb and remove impurities such as (CO ₂ ). Reference numeral 13 denotes a compressed air supply pipe that supplies the compressed air that has passed through the adsorption tower 12 to the heat exchanger 14.

Reference numeral 14 denotes a heat exchanger, into which compressed air from which H ₂ O, CO _{2 and the} like are adsorbed and removed by the adsorption tower 12 is sent and cooled to an ultra-low temperature. Reference numeral 16 denotes a rectifying tower, which further cools the compressed air cooled to an ultra-low temperature by the heat exchanger 14 and sent through the compressed air introduction pipe 15, liquefies a part thereof, and stores it as liquid air 21 at the bottom, and N ₂ Is stored in the upper part in a gaseous state. Reference numeral 17 denotes a condenser (condenser) with a condenser 18 disposed above the rectifying column 16. A part of the N ₂ gas accumulated in the upper part of the rectifying column 16 is fed into the condenser 18 via a first reflux liquid pipe 19. Further, the inside of the condenser 17 is in a depressurized state as compared with the inside of the rectifying column 16, and the stored liquid air (N ₂ ; 50 to 70%, O ₂ ; 30 to 50%) 21 at the bottom of the rectifying column 16. Is fed through a feed pipe 22 with an expansion valve 22a and is vaporized to cool the internal temperature to a temperature below the boiling point of liquid nitrogen (LN ₂ ). By this cooling, the N ₂ gas sent from the rectification column 16 through the first reflux pipe 19 into the condenser 18 is liquefied, and the LN ₂ liquefied and generated in the condenser 18 is converted into the second reflux liquid. The pipe 20 flows down and is supplied to the upper part of the rectifying column 16 by reflux. Then, the reflux liquid supplied to the upper part of the rectifying column 16 flows down in the rectifying column 16, contacts the compressed air rising from the bottom of the rectifying column 16, and cools by cooling. A part is liquefied. In this process, the high boiling point component (O ₂ ) in the compressed air is liquefied and collected at the bottom of the rectification column 16, and the low boiling point component N ₂ gas is collected at the top of the rectification column 16.

  23 is a liquid level controller for controlling the liquid level of the stored liquid air 21 at the bottom of the rectifying column 16, and controls the amount of waste gas supplied to the expansion turbine 30 by opening and closing a flow rate adjusting valve 28 a described later. . That is, when the liquid level exceeds a predetermined value, the opening degree of the flow control valve 28a is reduced to reduce the amount of waste gas supplied to the expansion turbine 30, and when the liquid level falls below the predetermined value, the flow control valve The amount of waste gas supplied to the expansion turbine 30 is increased by increasing the opening of 28a.

25 is a N ₂ gas takeout pipe for taking out the N ₂ gas accumulated in the upper part of the rectification column 16 as product N ₂ gas, compressed air and low-temperature N ₂ gas was guided into the heat exchanger 14, fed therein Heat-exchanged to normal temperature and sent to the main pipe 26. 27 is a waste gas extraction pipe that takes out the vaporized liquid air accumulated in the upper part of the condenser 17 as waste gas, and drives the expansion turbine 30 through the branch pipe 28 through all or part of the low temperature waste gas (including the case where there is no waste gas). In the meantime, it acts to guide the remainder into the heat exchanger 14. The waste gas guided into the heat exchanger 14 is heat-exchanged with the compressed air sent into the heat exchanger 14 to reach room temperature, and then is led out from the heat exchanger 14 and discharged to the outside through the discharge pipe 29. . 27a is a pressure control valve provided in the waste gas extraction pipe 27, 27b is a pressure controller provided in the waste gas extraction pipe 27, and is a waste gas (due to fluctuations in the amount of waste gas supplied to the expansion turbine 30). In order to suppress the pressure fluctuation due to the flow rate fluctuation, the pressure control valve 27a is opened and closed to maintain the pressure of the waste gas line.

An expansion turbine 30 expands the waste gas supplied from the branch pipe 28 to obtain a lower temperature waste gas, and then joins the downstream side portion of the pressure control valve 27a of the waste gas extraction pipe 27 via the return pipe 31. Let Thereby, waste gas passing through the waste gas extraction pipe 27 (low-temperature waste gas not branched from the waste gas extraction pipe 27 and further low-temperature waste gas branched from the waste gas extraction pipe 27 and passed through the expansion turbine 30) The compressed air sent into the heat exchanger 14 is cooled to a low temperature by the waste gas passing through the branch pipe 28 and the product N ₂ gas sent from the N ₂ gas extraction pipe 25. A flow control valve 28 a provided at the turbine inlet of the expansion turbine 30 controls the amount of cold generated in the expansion turbine 30 by controlling the amount of waste gas supplied to the expansion turbine 30. In the figure, 32 is a vacuum cold box.

This apparatus produces product nitrogen gas as follows. That is, first, air is compressed by the air compressor 11, H ₂ O in the air compressed by the drain separator (not shown) is removed, and the air is cooled by the Freon cooler (not shown). Then, it is fed into the adsorption cylinder 12 and adsorbs and removes H ₂ O, CO _{2 and the} like in the compressed air. Next, the compressed air from which H ₂ O, CO _{2 and the} like are adsorbed and removed is cooled by a refrigerant such as product N ₂ gas sent from the rectification column 16 via the N ₂ gas extraction pipe 25 and waste gas sent from the expansion turbine 30. It is sent to the cooled heat exchanger 14 and cooled to an ultra-low temperature, and in that state, it is put into the lower part of the rectifying column 16. Next, this charged compressed air is cooled by bringing it into contact with the reflux liquid liquefied and generated by the condenser 18, and a part is liquefied and stored as liquid air 21 at the bottom of the rectifying column 16. In this process, the difference in the boiling point of N ₂ and O _2, O ₂ is liquefied is a high-boiling components in the compressed air, N ₂ remains in a gaseous state. Next, the N ₂ remaining in this gas state is taken out from the N ₂ gas take-out pipe 25 and sent to the heat exchanger 14, where the temperature is raised to near room temperature and sent out as a product N ₂ gas from the main pipe 26. On the other hand, the liquid air 21 collected in the lower part of the rectifying column 16 is sent into the condenser 17 to cool the condenser 18. By this cooling, the N ₂ gas fed into the condenser 18 from the upper part of the rectifying column 16 is liquefied to become a reflux liquid for the rectifying column 16, and returns to the rectifying column 16 through the second reflux liquid pipe 20. . Further, the liquid air 21 that has finished cooling the condenser 18 is vaporized and taken out as waste gas by the waste gas extraction pipe 27. Then, all or a part thereof is introduced into the expansion turbine 30 via the branch pipe 28, where cold is generated and sent to the heat exchanger 14, and the compressed air sent into the heat exchanger 14 is cooled. It has become. Moreover, the remainder is sent directly to the heat exchanger 14, and the compressed air sent into this heat exchanger 14 is cooled. Such waste gas is led out from the heat exchanger 14 and then discharged into the air through the discharge pipe 29.
Japanese Patent Publication No.52-41232

However, since the above-described expansion turbine 30 has a gas processing variable amount of about 20% in general, the gas processing amount cannot be changed greatly. Therefore, even when the amount of product N ₂ gas generated is small and the amount of waste gas generated is large compared to during steady operation, such as during startup, a large amount of waste gas is introduced into the expansion turbine 30 to cause a large amount of cooling. It takes a long time to start. Moreover, since it is difficult to adjust the flow rate of the expansion turbine 30 alone, it is necessary to provide the flow rate adjustment valve 28 a at the turbine inlet of the expansion turbine 30, which increases the cost.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an inexpensive air separation method and an apparatus used therefor, which can shorten the startup time.

In order to achieve the above object, the present invention compresses air taken in from the outside by air compression means, removes impurities in the compressed air compressed by the air compression means by removal means, and passes through this removal means. the compressed air is cooled in the heat exchanger, the compressed air which has been cooled to a low temperature through the upper Symbol heat exchanger was separated by utilizing a boiling point difference of each component desired component at the top of the rectification means in the gaseous state Reserved, the remainder is stored as liquid air at the bottom of the rectifying means, and the waste gas generated in the rectifying means is taken out into the waste gas extraction path and introduced into the heat exchanger, and derived from the heat exchanger. An air separation method in which waste gas is discharged to the outside through a discharge path, wherein a part of the gas accumulated in the upper part of the rectifying means is taken out, cooled by a condenser and liquefied, and then the rectifying means Reflux to the upper part, and the refluxed liquid in the rectification means Flowing downward and making countercurrent contact with the compressed air rising from the bottom of the rectifying means, and by this contact, heat exchange is performed between the reflux liquid and the compressed air, and a part of the compressed air is liquefied. The rectifying means is allowed to flow down to the bottom of the rectifying means, and a part of the reflux liquid is vaporized to rise to the upper part of the rectifying means. On the other hand, a pulse tube type inflator is provided. The first gist is an air separation method in which waste gas in the waste gas take-out path is introduced, cooled and adiabatically expanded and then taken out from the pulse tube expander, and returned to the waste gas take-out path. An air compressing means for compressing air taken from the outside, a removing means for removing impurities in the compressed air compressed by the air compressing means, a heat exchanger for cooling the compressed air that has passed through the removing means, The via heat exchanger the compressed air which has been cooled to a low temperature and separated by utilizing the difference in boiling point components desired ingredient reservoir on top in a gaseous state, a rectification means for accumulating at the bottom and the remaining as liquid air , An air separation unit having a waste gas extraction path for extracting waste gas generated in the rectification means and introducing it into the heat exchanger, and a discharge path for discharging the waste gas derived from the heat exchanger to the outside A condenser provided outside the rectifying means, a first reflux pipe for taking out a part of the gas accumulated in the upper part of the rectifying means and inserting it into the condenser; and liquefying by the condenser And a second reflux pipe for refluxing the gas to the upper part of the rectification means, and a reflux liquid from the second reflux pipe flows down in the rectification means, and from the bottom of the rectification means. Contact with the rising compressed air countercurrently, and this contact Heat exchange is performed between the flowing liquid and the compressed air, and a part of the compressed air is liquefied and flows down to the bottom of the rectifying means, and a part of the reflux liquid is vaporized to be an upper part of the rectifying means. On the other hand, a pulse tube type expander is provided, and the pulse tube type expander introduces the waste gas in the waste gas take-out path into the pulse tube type expander, adiabatically expands and cools the pulse tube type expander. An air separation device configured to be taken out from the vessel and returned to the waste gas extraction path is a second gist.

  That is, in the air separation method of the present invention, the cold energy of the pulse tube expander is used as the cold source. This pulse tube expander is designed to change the open / close time and the number of open / close times of the open / close valve for waste gas suction and the open / close valve for discharge of the waste gas, etc. The amount can be changed as appropriate, and the amount of gas processing fluctuation is large. Therefore, a large amount of waste gas can be supplied to the pulse tube expander when the amount of product gas generated is small and the amount of waste gas generated is large, such as at the time of startup. , The startup time can be shortened. Moreover, since the flow rate of the pulse tube expander can be adjusted independently, it is not necessary to provide a flow rate control valve at the turbine inlet of the expansion turbine as in the conventional example, and the cost is reduced accordingly. Moreover, according to the air separation apparatus of the present invention, the above excellent air separation method can be performed.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing an embodiment of an air separation device of the present invention. In this embodiment, a pulse tube expander (pulse tube expander) 1 is used instead of the expansion turbine 30 used in the cryogenic air separation device of FIG. Since the pulse tube expander 1 can adjust the flow rate independently, the flow rate adjustment valve 28a at the turbine inlet of the expansion turbine 30 provided in the cryogenic air separation device of FIG. 9 is not provided. The liquid level controller 23 controls the liquid level of the liquid air 21 collected at the bottom of the rectifying column 16, as in the chilled air separation apparatus shown in FIG. The on-off valves 3, 4, 7 a, 8 a of the pulse tube expander 1 are opened and closed, and the amount of waste gas supplied to the pulse tube 2 is controlled. That is, when the liquid level exceeds a predetermined value, the number of times of opening and closing of the gas suction on-off valve 3 and the waste gas discharge on-off valve 4 (see FIG. 2) provided in the pulse tube expander 1 is reduced, When the amount of waste gas supplied to the panda 1 is decreased and the liquid level falls below a predetermined value, the number of times of opening and closing the gas suction on-off valve 3 and the waste gas discharge on-off valve 4 is increased, and the pulse tube expander 1 The amount of waste gas supplied to the system is increased. At this time, both the on-off valves 7a and 8a are appropriately controlled to open and close. The other parts are the same as those of the air separation device shown in FIG. 9, and the same reference numerals are given to the same parts.

  In this embodiment, the pulse tube expander 1 is an active buffer type as shown in FIG. 2, and a branch pipe 28 and a return pipe 31 are connected to a low temperature end portion of the pulse tube expander 1 itself. Pulse tube 2, gas suction on-off valve 3 provided on the branch pipe 28, waste gas discharge on-off valve 4 provided on the return pipe 31, and on-off valve 7 a, Two active buffer tanks 5 and 6 connected via connecting pipes 7 and 8 with 8a are provided. Then, the low-temperature waste gas sucked into the pulse tube 2 from the branch pipe 28 is adiabatically expanded and cooled in the pulse tube 2 to be further cooled, and then discharged to the return pipe 31. The gas is cooled and supplied to the heat exchanger 14. In the pulse tube expander 1, the amount of waste gas sucked into and discharged from the pulse tube 2 can be varied by appropriately setting the opening / closing time, the number of times of opening / closing, and the like of both the opening / closing valves 3 and 4. For this reason, a large amount of waste gas can be supplied to the pulse tube 2 when the amount of generated product gas is small and the amount of generated waste gas is large, such as during start-up, and the start-up time can be shortened. In this embodiment, the branch pipe 28 and the return pipe 31 are connected to the low temperature end portion of the pulse tube 2 via the first connection pipe 2a, but may be connected separately. Moreover, although the two connection pipes 7 and 8 are connected with the high temperature end part of the pulse tube 2 via the 2nd connection pipe 2b, you may connect separately, respectively.

  In the above configuration, the operation of the pulse tube expander 1 is performed by repeating the following cycle. That is, first, as shown in FIG. 3, the gas intake on-off valve 3, the waste gas discharge on-off valve 4 and the second on-off valve 7a are closed. In this state, the inside of the pulse tube 2 is the same pressure as the internal pressure of the low-pressure waste gas source. Next, when the first on-off valve 8 a is opened, the high-pressure waste gas in the high-pressure active buffer tank 6 flows into the high temperature end of the pulse tube 2, and the gas pressure in the pulse tube 2 is close to the pressure of the high-pressure active buffer tank 6. To rise. The gas distribution in the pulse tube 2 in the process P is shown in FIG. In FIG. 3, D is high-pressure waste gas introduced from the high-pressure active buffer tank 6, and B and C are waste gas in the pulse tube 2 that has been changed from low pressure to high pressure. In FIG. 3, reference numerals 2 c and 2 d denote disk-like laminar flow members disposed at the low temperature end and the high temperature end of the pulse tube 2.

  Next, as shown in FIG. 4, when only the gas intake on-off valve 3 is opened with the first on-off valve 8a opened (the other on-off valves 4 and 7a remain unchanged), the high-pressure waste gas High pressure waste gas is supplied from the source and flows into the low temperature end of the pulse tube 2. At this time, the supply pressure of the high-pressure waste gas source is set slightly higher than the pressure of the high-pressure active buffer tank 6, and the high-pressure waste gas of the high-pressure active buffer tank 6 that has flowed into the high-temperature end of the pulse tube 2 in the above process P. D (see FIG. 3) is immediately returned to the high pressure active buffer tank 6. This process Q is basically an isobaric supply process, and the gas distribution in the pulse tube 2 is shown in FIG. In FIG. 4, A is high-pressure waste gas introduced into the pulse tube 2 from the high-pressure waste gas source.

  Next, as shown in FIG. 5, after the first on-off valve 8a and the gas intake on-off valve 3 are closed (the waste gas discharge on-off valve 4 remains closed), the second on-off valve 7a is opened. When the valve is operated, the gas C (see FIG. 4) at the high temperature end of the pulse tube 2 flows (returns) into the low-pressure active buffer tank 5, so that the pressure in the pulse tube 2 decreases to the pressure of the low-pressure active buffer tank 5. That is, the high-pressure waste gas A that has entered the low-temperature end of the pulse tube 2 in the above process Q expands to the pressure of the low-pressure active buffer tank 5 together with the waste gas B, drops in temperature, and reaches the low-temperature end side of the pulse tube 2. Cooling. The gas distribution in the pulse tube 2 in the process R is shown in FIG.

  Next, as shown in FIG. 6, when the waste gas discharge on-off valve 4 is opened (the other on-off valves 3, 7 a, 8 a remain unchanged), the waste expanded in the pulse tube 2 in the process R described above. The gas A is discharged to the low pressure waste gas source, and the low pressure waste gas from the low pressure active buffer tank 5 flows into the pulse tube 2.

  Thus, one cycle is completed, and then the above process P is newly started. Since the workpiece is circulated in this way, the high-pressure waste gas expands constantly and becomes a low pressure. When heat conduction and mixing in the gas pulse tube 2 and loss due to flow are not considered, the pressure in the high-pressure active buffer tank 6 is the supply pressure of the high-pressure waste gas source, and the pressure in the low-pressure active buffer tank 5. Is equal to the internal pressure of the low-pressure waste gas source. When the above cycle is completed, the waste gas A eventually enters the pulse tube 2 from the high pressure waste gas source, adiabatically expands in the pulse tube 2 and generates cold, and then is discharged into the low pressure waste gas source. That's right. Further, the waste gas B always plays the role of a gas piston in the pulse tube 2, and C and D only enter and exit from the respective active buffer tanks 5 and 6, respectively.

  Table 1 below shows an indication of the gas throughput of the apparatus shown in FIGS. First, the premise is that only the low temperature waste gas in the waste gas line is used as cold in both the above-mentioned apparatuses. Further, the time (start-up time) from the start to the steady operation is determined by the amount of heat exchange in the waste gas line. A certain percentage of the waste gas in the waste gas line is self-expanded by the expansion turbine 30 (see FIG. 9) or the pulse tube expander 1 (see FIG. 1), and is further cooled to obtain further coldness. . And more cold can be obtained by supplying more waste gas to the expansion turbine 30 or the pulse tube expander 1. That is, the greater the amount of waste gas supplied to the expansion turbine 30 or the pulse tube expander 1, the more cold is obtained.

In both apparatuses, the total amount of raw material air is 100% by volume (hereinafter abbreviated as “%”). In both the above devices, it is assumed that the amount of product N ₂ gas at the time of steady operation and at the start and the amount of waste gas in the waste gas line are equal. That is, the two devices together, at the time of steady operation, the product N ₂ gas amount of 50% of the total amount of waste gas quantity of the waste gas line is to be 50% of the total amount, at the time of start, the product N ₂ gas amount Is 20% of the total amount, and the waste gas amount of the waste gas line is 80% of the total amount. Further, as described above, the gas processing fluctuation possible amount of the expansion turbine 30 is generally about 20%.

  As shown in Table 1 below, at the time of steady operation, both of the above devices are supplied to the heat exchanger 14 after 45% of the 50% waste gas is supplied to the expansion turbine 30 or the pulse tube expander 1. 5% is fed directly into the heat exchanger 14 (that is, not via the expansion turbine 30 or the pulse tube expander 1).

  On the other hand, at the start, only 50% of the 80% waste gas can be supplied to the expansion turbine 30 in the cryogenic air separation device of FIG. For this reason, only 50% of the waste gas is supplied to the expansion turbine 30 and then sent to the heat exchanger 14, and 30% of the waste gas is sent directly to the heat exchanger 14. Therefore, cold is obtained by 30% of the low temperature waste gas and 50% of the lower temperature waste gas (via the expansion turbine 30). On the other hand, in the air separation device of FIG. 1, 80% of all waste gas can be supplied to the pulse tube expander 1. Therefore, chilling is obtained by 80% of the lower temperature waste gas (via the pulse tube expander 1). As described above, in the air separation device of FIG. 1, the amount of cold gas is large in the waste gas sent to the heat exchanger 14, and thus the amount of cold is large, thereby the time until the entire system cools down. (That is, the time from start to steady operation [starting time]) is shortened.

As described above, in this embodiment, since the pulse tube expander 1 is used as a cold source, when the amount of product N ₂ gas generated is small and the amount of waste gas generated is large as at the time of startup. By supplying this large amount of waste gas to the pulse tube expander 1, the start-up time can be shortened. In addition, since the flow rate of the pulse tube expander 1 can be adjusted independently, it is not necessary to provide a flow rate control valve at the turbine inlet of the expansion turbine as in the conventional example, and the cost is reduced.

FIG. 7 shows another embodiment of the air separation device of the present invention. In this embodiment, the waste gas extraction pipe 27 sends all or part of the low-temperature waste gas (including the case where there is no waste gas) to the pulse tube expander 1 via the branch pipe 28, while the remainder is the heat exchanger. After being guided into 14, it acts to be released to the outside. Further, after the waste gas that has passed through the pulse tube expander 1 is guided into the heat exchanger 14 by the return pipe 31, it is discharged from the discharge pipe 29 to the outside. Other parts are the same as those of the air separation device shown in FIG. 1, and the same reference numerals are given to the same parts. This embodiment also acts in the same manner as the above embodiment and produces the same effects.

  FIG. 8 shows still another embodiment of the air separation device of the present invention. In this embodiment, the branch pipe 28 is branched from the waste gas extraction pipe 27 in the heat exchanger 14 in the air separation device of FIG. The other parts are the same as those of the air separation device shown in FIG. 7, and the same reference numerals are given to the same parts. This embodiment also acts in the same manner as the embodiment of FIG. 7 and produces the same effects.

It is a block diagram which shows one Embodiment of the air separation apparatus of this invention. It is explanatory drawing of a pulse tube expander. It is explanatory drawing which shows the effect | action of the said pulse tube expander. It is explanatory drawing which shows the effect | action of the said pulse tube expander. It is explanatory drawing which shows the effect | action of the said pulse tube expander. It is explanatory drawing which shows the effect | action of the said pulse tube expander. It is a block diagram which shows other embodiment of the air separation apparatus of this invention. It is a block diagram which shows other embodiment of the air separation apparatus of this invention. It is a block diagram which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pulse tube expander 11 Raw material air compressor 12 Adsorption tower 14 Heat exchanger 27 Waste gas extraction pipe 29 Release pipe

Claims (2)

Were taken from the outside air is compressed by the air compression means, the impurities in compressed air compressed by the air compression means is removed by removing means, it cooled compressed air passed through the removing means in the heat exchanger, the upper Symbol Compressed air cooled to a low temperature via a heat exchanger is separated using the difference in boiling point of each component, and the desired component is stored in the upper part of the rectifying means in a gaseous state, and the rest is liquid air as the above rectifying means. The waste gas generated in the rectification means is taken out into the waste gas extraction path and introduced into the heat exchanger, and the waste gas derived from the heat exchanger is discharged to the outside through the discharge path. In this air separation method, a part of the gas accumulated at the upper part of the rectifying means is taken out, cooled by a condenser and liquefied, and then refluxed to the upper part of the rectifying means. The bottom of the rectifying means is allowed to flow downward in the means In contact with the rising compressed air, the heat exchange is performed between the reflux liquid and the compressed air by this contact, and a part of the compressed air is liquefied to flow down to the bottom of the rectifying means. A part of the reflux liquid is vaporized and raised to the upper part of the rectification means. On the other hand, a pulse tube type expander is provided, and the waste gas in the waste gas take-out path is introduced into the pulse tube type expander. Then, after adiabatically expanding and cooling, the air is extracted from the pulse tube expander and returned to the waste gas extraction path. An air compressing means for compressing air taken from the outside, a removing means for removing impurities in the compressed air compressed by the air compressing means, a heat exchanger for cooling the compressed air that has passed through the removing means, and this heat Rectification means for separating the compressed air cooled to low temperature via the exchanger using the difference in boiling point of each component , storing the desired component in the gas state in the upper part, and storing the rest as liquid air in the bottom part ; An air separation device comprising: a waste gas extraction path for extracting waste gas generated in the rectification means and introducing it into the heat exchanger; and a discharge path for discharging the waste gas derived from the heat exchanger to the outside And a condenser provided outside the rectifying means, a first reflux pipe for taking out a part of the gas accumulated in the upper part of the rectifying means and inserting it into the condenser, and liquefied by the condenser. The gas above the rectification means A second reflux pipe for refluxing, and the reflux liquid from the second reflux pipe flows downward in the rectification means, and contacts the compressed air rising from the bottom of the rectification means in countercurrent. By this contact, heat exchange is performed between the reflux liquid and the compressed air, and a part of the compressed air is liquefied and flows down to the bottom of the rectifying means, and a part of the reflux liquid is vaporized to cause the purification. On the other hand, a pulse tube expander is provided, and the pulse tube expander is introduced with the waste gas in the waste gas take-out path and adiabatically expanded and cooled, and then the above. An air separation device configured to be taken out from a pulse tube expander and returned to the waste gas extraction path.