JPS60122704A - Control system for fractionating air by selective adsorption - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION The present invention relates to the fractionation of gas mixtures by selective adsorption and particularly relates to the separation of gas mixtures by selective adsorption, with or without recovery of high purity nitrogen products. Concerning the recovery of oxygen-enriched gas fractions.

Systems for separating air components by selective adsorption to recover oxygen and/or nitrogen are well known in the art. Most known such systems typically use zeolite molecular sieve adsorbent beds to selectively retain nitrogen from the feed gas and collect the oxygen-enriched product stream as a primary effluent. There is.

When the sorption bed reaches a designed level of sorbed gas, the sorption bed is desorbed and/or purged to remove the nitrogen contained therein before being returned to the operating process. . This adsorption/desorption cycle relies primarily on swings in the pressure levels of these steps during the operating cycle. Also, to maintain continuous operation, several and more adsorbent beds are operated in parallel so that one adsorbent bed is operated in the adsorption step of the adsorption-desorption cycle while one adsorbent bed is operated in parallel. One or more combined adsorbent beds are operated in various regeneration steps.

In some known systems, the charge feed gas is introduced into an adsorption column at a relatively high initial pressure during the adsorption step, and then the column pressure is close to atmospheric pressure to effect column desorption. pressure or lowered to a pressure level below atmospheric pressure.

Air separation by vacuum swing adsorption (VIA) is described, for example, in U.S. Pat. Nos. 3,533,221 and 3,957,4.
No. 65, No. 4,013,429 and No. 4,26
No. 4,340. U.S. Patent No. 4,
As described in No. 013,429, the operation involves four main steps: That is,
(1) Ambient air from which moisture and CO2 have been removed in the pretreatment column is passed through a column that is placed in series with the pretreatment column and contains a bed of adsorbent for selectively retaining nitrogen in the feed gas, while Unadsorbed oxygen-enriched product gas is recovered as a primary effluent and collected and stored in a surge chamber, such as a retractable receiving vessel. The supply of ambient air is continued until an initial leakage of air or a slight air shortage occurs depending on the desired concentration of oxygen-enriched product. Air flow to the adsorbent bed is then shut off and switched to the combined adsorbent bed that has been previously regenerated and pressurized to the set operating pressure level. The out-of-service adsorbent bed is then flushed with high-purity nitrogen collected from the previous step during the cycle, thereby saturating the adsorbent bed with nitrogen. The bed is then (3) desorbed with high purity nitrogen by the exhaust gas. A portion of the high purity nitrogen is used as a cleaning gas (in step (2)) and the remainder is collected as a nitrogen product and stored in a surge chamber. After evacuating the adsorbent bed to the desired level, (4) a portion of the previously collected oxygen-enriched product gas is removed from the surge chamber;
It is then introduced into the adsorbent bed to saturate the adsorbent bed and return the pressure of the adsorbent bed to the desired pressure level to begin restarting the ambient air supply and repeating the cycle.

Similar except that the system is combined with a combined thermal swing section for operation to dry the wet nitrogen stream recovered by vacuum desorption of the pretreatment column and the nitrogen adsorption column. A sequence of operations is disclosed in US Pat. No. 4,264,340.

U.S. Patent Nos. 4,013,429 and 4,264
In the operation of conventional systems such as those described in No. 340, the time intervals for each of the steps in the cycle sequence are determined by a set program, The opening and closing of the hold control valve is controlled by a cycle timer device.

Du in pending U.S. Patent Application No. 416,463;
The duration of each adsorption step and nitrogen scrubbing step in the V8A process for air fractionation is determined by detecting the analyzed composition percentage of each withdrawn product stream during these steps and at the set composition level. Automatically controlled by terminating adsorption and washing respectively when reached. Additionally, the extent of evacuation of the main adsorbent bed and pretreatment bed is automatically controlled to end when a set vacuum level is detected. The control system operates in a similar manner to terminate the repressurization process when a set pressure level is reached. The flow rate of incoming air is kept constant.

[Summary of the invention]

The present invention provides that the air supply and/or nitrogen wash stages of the cycle collect the respective present amounts of oxygen and/or nitrogen (invθn) in separate surge vessels that collect the oxygen and nitrogen.
The present invention provides a novel automatic control system for regulating the vacuum swing adsorption process that is automatically adjusted according to the temperature. The present amounts of oxygen and nitrogen are monitored by pressure and/or level sensors in the oxygen surge container and nitrogen surge container.

By performing these controls, the production rate of oxygen and/or nitrogen can be changed as desired or as necessary.

[Detailed description of embodiments of the invention]

With the exception of the modified embodiment illustrated in FIG.
That is, it is consistent with (1) adsorption, (2) nitrogen cleaning, (6) desorption, and (4) repressurization.

At least two series of adsorbent beds are preferably used, each series comprising a pretreatment adsorbent bed and a main adsorbent bed, the series being operated alternately to divert the incoming air charge from one series to the other. It is now possible to switch to the series.

Referring now to FIG. 1, a nitrogen selective adsorbent is housed in two parallel adsorption columns 10 and 11 which are operated alternately in a controlled sequence. Upstream of each of columns 10 and 11, water and CO2 are removed from the air before feeding the incoming air to column 10 or 11.
Adsorbent bed 1 containing a solid adsorbent effective to remove
2 and 13 are provided. The air to be separated is supplied to a blower 16 through a line 15. Blower 1
6 discharges air into manifold 17. The alternating introduction of feed air into series A consisting of columns 12 and 10 and series B consisting of adsorbent beds 13 and 11 is effected by opening and closing valves 18 and 19.

The inlet air is ly/20 when valve 18 is in the open position.
is supplied to the adsorbent bed 12 of the series through the column 1
line 2 when 8 is congested and valve 19 is open.
1 to the adsorbent bed 16 of series B. During the period of operation, when ambient air containing moisture and CO2 is introduced into the pretreatment bed 12 through the valve 18, the cubicle 22 between the pretreatment bed 12 and the main adsorbent bed 10 is opened. In this way, moisture and CO
The air from which 2 has been removed enters and passes through the main adsorption bed 10. Nitrogen is selectively adsorbed in the main adsorption bed 10,
During this time, the oxygen-enriched effluent gas is discharged from the valve 24 and the tank 25.
is discharged into a closed line 26.

Line 26 supplies the effluent gas to a discharge line 26 which communicates with a telescopic container 27.

In the surge vessel 27 the enzyme-enriched effluent is collected and temporarily stored. The stored gas can be removed from the surge vessel 27 through line 29 for further processing as needed or for use as desired. Alternatively, the surge container 27 can be replaced by a constant volume container.

The operation described so far does not differ from that of US Pat. No. 4,014,429. However, according to the present invention, the control of the amount of gas in the surge container 27 storing gas and/or nitrogen, as described below, is controlled by the gas supply and/or process nitrogen cleaning. Used to adjust the process. The current amount of gas in these surge vessels is controlled by pressure sensors and/or level sensors combined to act on these surge vessels. The air supply to the pretreatment column 12 and the column The discharge of the oxygen-enriched effluent from 10 into the surge vessel 27 continues, during which the internal pressure of the surge vessel 27 is increased by the incoming oxygen-enriched gas. The surge container 27 is equipped with a level sensor device 60. The level sensor device 60 is activated when the Prada in the surge container 27 reaches a set height or level. The amount of gas present in the surge container 27 can be controlled by the pressure sensor 51 in addition to or in addition to the level sensor device 60. When sensors 50 and/or 31 are actuated, suitable relays are configured to close valves 14 and 24 and open valve 25 to interrupt the flow of feed air into the series of columns 12 and 1°. It is preferable to do so. Also, at this time, the cell 40 is automatically opened and nitrogen cleaning ``t'' of the columns 12 and 10 is started as described below.

If desired, if the air supply step is terminated before the surge vessel 27 is completely filled to the set level or causes nitrogen to escape from the column 10,
A timer device can be added to continue supplying air for a predetermined delay time interval after actuation of sensors 30 and/or 31. Alternatively, a timer device may be used in conjunction with current control of the nitrogen flushing process of vessel 41 to determine the total air supply process.

Nitrogen flushing of beds 12 and 10 is carried out in the same direction of gas flow as the previously carried out direction of feed air introduction. The nitrogen stored in the surge container 41 is passed through the open valve 18 and line 17 by the blower 16 which acts as a pump.
through line 20 , which in turn introduces nitrogen into pretreatment adsorption bed 12 . The introduced nitrogen passes through column 12 and open cell 22 to column 10.
continues to flow into column 10 and continues to flow through column 10.
Expel the gas contained in Dito to the outside and clean it. The wash effluent exits column 10 through open valve 25 and is discharged to the atmosphere via discharge line 45. A device can be provided for separately collecting the gas which is discharged through line 45 if desired.

Preferably, the nitrogen flush step is controlled by the amount of gas present in the nitrogen surge vessel 41.

The surge vessel 41 is equipped with a height level control sensor 47 and/or a pressure sensor 48 . When nitrogen is charged into the surge container 41 (from a nitrogen source described below), the pressure inside the surge container 41 increases and the pressure is detected by the sensor 4.
8 (or level sensor 47). Such a sensor 47°4
8, the volume of nitrogen introduced into the surge container 41 is the sum of the volume removed from the surge container 41 for the cleaning process and the volume removed as a product through line 49. Occurs when exceeds. sensor 47 or 48
can be connected in operation with a timer device. This timer device will use the excess nitrogen for a longer period of time for nitrogen cleaning when sensor 47 or 48 is activated, thereby improving the purity of the product. The timer is provided with a certain delay time interval in order to increase the efficiency. If sensor 47 or 48 is not activated during this cycle, the nitrogen flush time is reduced by a predetermined amount.

In this manner, the nitrogen flush time interval continues to decrease progressively during each successive cycle such that the stock in fusage vessel 41 eventually increases to a level sufficient to activate sensor 47 and fc 48. I am forced to do it. Therefore, by using sensors 47 or 48, the effective volume of nitrogen gas (as determined by the nitrogen flush time range) can be increased or decreased to increase or decrease the product nitrogen and vacuum desorb the adsorbent bed on which the nitrogen has been adsorbed. The volume of nitrogen gas obtained is adjusted to compensate for increases and decreases due to temperature changes. Alternatively, a predetermined timer device can be used to determine the total nitrogen wash step when used in conjunction with air supply step gas stock control as described above.

Once actuation of sensor 47 or 48 begins, with or without a time delay, valve 18.25
and 40 close and 7f-50 open to complete the cleaning process and begin the evacuation step of the operating sequence. valve 2
Vacuum pump 52 when 4 and 25 are in the closed position
By activating the valve 22f, the contained gas is desorbed from the adsorbent bed in the column 10, and the valve 22f is opened.
via pretreatment column 12 and into the inlet of pump 52 via open valve 50 and line 53. The outlet of pump 52 releases gas into surge container 41 .

Evacuation of columns 10 and 12 continues for a predetermined time interval set to achieve the desired vacuum level. At the end of this set time interval, valve 22 between columns 10 and 12 is closed and evacuation of column 12 continues for a further predetermined time interval. Preferably, this extended time interval coincides with the completion of the Series B nitrogen cleaning step.

When flow communication between columns 10 and 12 is interrupted by closing valve 22, repressurization of column 10 is initiated by simultaneously opening valve 24. Oxygen-enriched gas is removed from surge vessel 27 and transferred to line 2
6 and 23 into the evacuated column 10. During this period, the pretreatment column 12 is further evacuated.

When a predetermined period of time for subsequent evacuation of column 12 has elapsed, cell 50 is closed and valve 22 is reopened to allow oxygen-enriched gas to flow from column 10 into column 12 to reload column 12. Press. When both columns 10 and 12 reach the set pressure level, column 1
Either one or both of control switches 60 and 61 operatively associated with 0 and 12, respectively, are actuated, thereby terminating the repressurization of the columns of series A and into series A. A signal is generated to resume the air supply and the cycle of operation described above is repeated.

Next, 1 series B replaces series A and undergoes the same operation sequence as described for the series person. Valve 5
Evacuation of columns 11 and 15 begins when repressurization of both columns 1o and 12 of series A is initiated by closing o and opening 9P22. Columns 1o and 12 during the respective operating stages of series A and B.
Table 1 also shows the position of the flow control valves in combination with columns 11 and 15 when applied to a system with two parallel trains operating in parallel. Pressure control switches 67 and 68 of series B correspond to control switches 60 and 61 of series A and extend the same functionality.

In the system illustrated in FIG. 2, the same process sequence as described above is used. Second
In the figure, elements common to FIG. 1 are designated by the same reference numerals.

The version of FIG. 2 uses a different control mechanism to complete the evacuation process. As can be understood from Figure 2,
The main adsorbent columns 10 and 11 are equipped with a vacuum detection switch 70
and 71, respectively.The exhaust system of series A is started when the nitrogen cleaning step is completed as described above.

Pumping of series A continues until switch 70 is activated at the set vacuum level. When the switch 70 is activated,
Valve 22 between columns 10 and 12 is closed and evacuation of only pretreatment column 12 continues for a set predetermined time interval and/or until the nitrogen flush of series B is completed. Pretreatment column 1 with 3P22 closed
During the further evacuation of 2, the oxygen-enriched gas from the storage vessel 27 flows into the main adsorbent column 10 via the open cell 24.

The operation of the embodiments of FIGS. 1 and 2 described above is particularly advantageous when vacuum swing adsorption (V8A) systems are operated to optimally produce high purity nitrogen. If the focus is on oxygen recovery, the simplified system illustrated in FIG. 5 can be used. In the variant system of FIG. 3, there is no need to use a nitrogen cleaning step, so the nitrogen storage container 41 as well as the cubicle 40 that would otherwise be required to be placed in the nitrogen cleaning line are omitted.

Therefore, the cycle when operated in oxygen recovery mode includes only three major steps: air supply, evacuation, and repressurization.

In the discharge line from the blower 16, in order to enable the blower 16 to operate continuously during intermittent periods when both series A and B are not in the air supply process and neither of these series are in the nitrogen cleaning process. A valve 59 is provided. With this configuration, the air flowing into the blower 16 via *14 is discharged into the atmosphere through the opened valve 59.

In order to remove water and CO2 from the ambient air supply, known solid adsorbents suitable for this purpose such as silica gel, alumina, activated carbon or natural or synthetic zeolite molecular sieves such as Nziwam are used in the pretreatment beds 12 and 13. Either mordenite or commercial 5A or 71C ore 13x zeolite can be used. Main adsorbent bed 10
and any solid adsorbent with a preferential affinity for total nitrogen adsorption from a mixture of nitrogen and oxygen, such as commercial 5 large molecular sieves (calcium zeolite A) or pores in the range of 5 to 10 angstroms. Synthetic indium mordenite can be used having a size of .

The use of the novel control system of the present invention in operations for the recovery of nitrogen and/or oxygen from the atmosphere does not require any modification of the normal operating conditions commonly used for such purposes. There isn't. The air supply step can be carried out at a pressure level of about atmospheric pressure or slightly above or below atmospheric pressure, for example, about 700-800 Torr. The operating train is maintained at this pressure level by pressurizing the column with previously recovered oxygen-enriched gas. Vacuum desorption of the main adsorbent columns 10 and 11, which were previously flushed with nitrogen, is carried out by bringing these columns to intermediate pressure levels, preferably in the range of 40 to 200 Torr. Pretreatment beds 12 and 15
The final vacuum desorption of is preferably maintained at a final pressure level in the range of 5 to 100 Torr.

FIG. 6 illustrates the seven-styling sequence used in the operation of the embodiment of the invention according to FIGS. 1 and 2 using two parallel adsorption trains designated A and B. . Table 2 below shows each layer of the cycle sequence process! The preferred operation is shown in terms of duration range and prototype cycle.

Table 2 Average time Prototype cycle (sec) Time (sec) B = Repressurization 10-6060 AF = Air supply 30-5045 NR = Nitrogen wash 20-4035 E = Exhaust 60-120 100 Ex = Extended exhaust 5-2010 FIG. 4 illustrates a cycle sequence programmed for automatic operation of a system for implementing the invention according to the embodiment illustrated in FIGS. The system is purged before the start of the adsorption cycle. At the beginning of the adsorption cycle, air is supplied to the repressurized train B while train A is being evacuated. The sequence of steps performed in series B is shown in the right block of FIG. The supply of air to the B series columns 16 and 11 continues until the surge container 27 is sufficiently filled to activate the sensor 60 or 31. When this filling is completed, the valve 6 controls the outflow of the oxygen-enriched gas from the box 14 and the column 11, which controls the supply of air to the line B.
6 are both closed. Also, at this time, the valve 40 is automatically opened and nitrogen cleaning of the columns 16 and 11 with nitrogen from the surge container 41 is started. As previously mentioned, the duration of the nitrogen flush step can be shortened or lengthened depending on the amount of nitrogen present in the surge vessel 41. Also, the start of exhaust for series B, as indicated by the dotted arrow line leading to the block where "Wait until exhaust for series A is completed," is the time when the extended exhaust is set by the relay ( seconds) until completion. According to the embodiment of FIG. 1, evacuation of train B is continued for a predetermined period of time set by a cycle timer or for an extended time interval coinciding with completion of the nitrogen scrub step of train A. Alternatively, according to the embodiment of FIG. It will continue until it closes. Column 1
Evacuation of column 11 continues, while repressurization of column 11 with oxygen-enriched gas begins. Evacuation of the column 16 continues until either it is shut off after a set predetermined time or the nitrogen flush step of series A is completed. Upon completion of evacuation of column 13, cell 62 is reopened to allow repressurized gas from column 11 to flow into column 13. The cycle is repeated when both columns 11 and 15 are maintained at operating pressure and are boiled out with the introduction of feed air into train B.

In series A (on the left side of Figure 4), the same process sequence as described for series B is carried out,
It begins with the exhaust of series A when the supply air is pumped into series B.

The control of the duration of the nitrogen flush step, preferably by the existing amount of nitrogen in the surge vessel 41, is illustrated in FIG. In this way, during train B pumping, the desorbed nitrogen is released into the surge vessel 41. sensor 47 and/or 4
Step 8 determines whether nitrogen has been filled into the surge container 41 to the design level. If sensor 47 indicates that surge container 41 is completely filled, the system follows path Y (yes), increases the nitrogen flush time (BR) in series B, and sets the nitrogen flush timer to 1. It operates to reach the maximum level of the set range, and excess nitrogen is used in the nitrogen cleaning step to increase the purity of the product. If the existing amount of nitrogen in surge vessel 41 drops below the amount required to operate sensors 47 and/or 48 during a particular cycle, as shown by path N in FIG. The flush timer setting is decreased by a predetermined amount such that the nitrogen flush time is increased during each successive cycle until the amount of nitrogen present in surge reservoir 41 is sufficient to activate sensors 47 and/or 48. continues to decrease by the same amount. In this manner, the extent of cleaning is adjusted to compensate for increases or decreases in the flow of product nitrogen and the volume of evacuated gas caused by temperature changes or other occurring fluctuations.

Although FIG. 5 shows the control system applied to series B, it will be understood that the same operational controls would be applied to series A as well.

The cycle sequence of operation according to the embodiment of FIG. 3 is illustrated in the chart of FIG. As can be seen from this chart, train A is allowed to idle for a short period of time between the completion of the air inlet stroke and the beginning of the exhaust stroke.

This idle period increases the capacity of the vacuum system (RI2) thereby reducing the time for the evacuation step and the extended evacuation step and can be eliminated by approximately 9 combined cycles.

During the entire period in which train A undergoes the repressurization (R), air supply (AF), and idle sequence, train B undergoes the exhaust (E
) and (EX) sequences.

Also, when train A is evacuated, train B undergoes the same sequence. By controlling the amount of gas collected in the multi-nitrogen surge vessel 41 and oxygen surge vessel 27, respectively, according to the present invention, Analysis of the oxygen content of the primary effluent from the main adsorbent column has created a problem in the plant-scale operation of conventional air fractionation systems, where analysis is used as the main control for terminating the air supply process. One of the drawbacks of such conventional systems is caused by drift in the calibration of the oxygen analyzer due to changes in time and ambient temperature. Moreover, since the oxygen present in the oxygen storage vessel is not monitored, there is no guarantee that sufficient gas will always be available to provide the necessary repressurization of the column. In the operation of such prior art vacuum swing adsorption (V8A) equipment, the 'control system is designed to provide a constant production rate at the highest temperature. There is no provision to automatically brake the nitrogen wash when the temperature drops, and the extent of the nitrogen wash can be used to improve product purity; The raw product must be discharged from the nitrogen surge vessel. On the other hand, the control of the nitrogen current in the nitrogen surge container is not monitored, so if the nitrogen content in the nitrogen surge container becomes too low for the required cleaning, it is necessary to take the unit out of operation. It might become.

The control system of the present invention not only eliminates these drawbacks of prior art control systems, but also provides additional advantages, including the ability to operate at various production rates with a device that adjusts the nitrogen wash accordingly. can. By adjusting the nitrogen wash, excess nitrogen produced can be advantageously used to maximize product purity.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic flow diagram illustrating a system for carrying out an embodiment of the present invention specifically designed to optimally produce high purity nitrogen; FIG. Figure 3 is a schematic flow diagram of a system similar to that of Figure 1 using different mechanisms to complete the evacuation step in the cycle sequence, and Figure 3 is a nitrogen wash step and a surge vessel for collecting the nitrogen product gas. 4 is a schematic flow diagram of a simplified variation of FIG. 1 designed to optimally produce a stream of particularly oxygen-enriched product having removed In the block diagram of the automatic operating sequence of the control system, FIG. υ,
6 is a cycle sequence chart of operation according to the embodiment of FIGS. 1 and 2, and FIG.
3 is a cycle sequence chart of operation according to the illustrated embodiment; FIG. 10.11...Adsorption column, 12.13...Pretreatment adsorbent column, 16...Blower, A, B...Series,
27... Surge container, 30... Level sensor device,
61... Pressure sensor, 41... Surge container, 47...
...FJ awning control seven sensors, 48...pressure sensor,
52..., PE empty bong, 60, 61... Control switch, 67.68... Pressure control switch, 70.71
...Vacuum sensor switch.

Claims (1)

Claims: 1) Ambient air, previously freed of water and CO2, is passed through a bed of solid adsorbent that selectively reserves nitrogen over oxygen, so that the oxygen is removed from said bed and collected in a receiver. an ambient atmosphere comprising producing an enriched gaseous effluent and applying a vacuum to the nitrogen-adsorbed adsorbent to desorb it, and then repressurizing the adsorbent bed with a portion of said oxygen-enriched gaseous effluent. In the operation of a circulation system for recovering an oxygen-enriched effluent product by selective adsorption of nitrogen from an air feed stream, the continuity of the air feed process is maintained by monitoring the current amount of oxygen-enriched gas in the receiver. A method of operating the circulation system, characterized in that it comprises automatically controlling it. 2) the air supply is continued until the receiver is retractable and the retractable receiver is filled to a detected set height level, and upon completion of filling the receiver, further air supply to the bed; 5) The supply of air continues until a set gas pressure level is detected in the receiver. Claim 1, characterized in that when a set gas pressure level is detected, further air supply to the bed is automatically cut off and vacuum desorption of the bed is initiated. How to operate the circulation system described in section. Removal of water and Co2 contained therein from the ambient air by passing the ambient air through a bed of adsorbent placed in series with said bed of solid adsorbent which selectively retains nitrogen. An operating method applied to the circulation system according to claim 1. 5) (1) introducing water and CO2-removed air into a bed of adsorbent that selectively retains nitrogen and collecting the unadsorbed oxygen-enriched effluent in a second Luciper;
(3) desorbing the nitrogen by applying a vacuum to the nitrogen-adsorbed bed;
and passing the desorbed nitrogen effluent into the second receiver, and (4) supplying oxygen-enriched gas removed from the first lucifer into the adsorbent bed. In the fractionation of air by a vacuum swing adsorption process, including the subsequent steps of repressurization, step ( A method for fractionating air by a vacuum swing adsorption method, characterized in that it includes controlling the duration of 1) and/or (2), respectively. 6) The first receiver is extendable and retractable, and the duration of step (1) is automatically terminated upon activation of a height level sensor device combined with the first extendable receiver. A method for separating air according to claim 6. 7) upon activation of said height level sensor device, the introduction of air and collection of oxygen-enriched effluent continues for a predetermined time interval set by the initial operating diameter of said height level sensor device; A method for separating air according to claim 6. 8) The air fractionation method according to claim 5, characterized in that the duration of step (1) is automatically terminated after reaching a preset pressure level in the first luciper. 9) A patent characterized in that after reaching the set pressure level in the first lucifer, the introduction of air and the collection of the oxygen-enriched effluent are continued for a predetermined time interval before the end of step (1). A method for separating air according to claim 8. 10) the second receiver is extendable and retractable;
A method according to claim 8, characterized in that the duration of step (2) is automatically terminated upon actuation of the height level sensor device combined with the extendable receiver of the invention. 0 11) The process continues for a predetermined time interval in accordance with the operation of the height level sensor device, in which an initial operating diameter of the height level sensor device is set. 10. A method of air fractionation according to claim 10. 12) The duration of step (2) is automatically terminated after reaching a set pressure level in the second receiver. Air fractionation method described. '3) After reaching the set pressure level in the second receiver, the operation of step (2) is continued for a predetermined time interval before the end of step (2). The air fractionation method described in paragraph 12. 14) A method according to claim 5, characterized in that the vacuum desorption step (6) is carried out until a predetermined vacuum level is reached in the adsorbent bed. 15) Nitrogen is selectively adsorbed from the air fed into the adsorption column during the period of operation, during which time the oxygen-enriched gas effluent released from said adsorption column is collected and stored in a surge vessel, and the adsorption The nitrogen-containing column is then desorbed by vacuum, and a device for controlling the duration of the air supply operation period is provided with a current volume monitoring device in combination with the effluent storage surge vessel, and a device for controlling the duration of the air supply operation period is included in the surge vessel. The monitoring device is activated when the detected water pressure level or the detected height level of the gas collected in the gas reaches a predetermined value, and the monitoring device starts closing the valve to close the valve. A circulation system for fractionating air, characterized in that it is operable to terminate a period of air delivery operation. 16) further comprising a second surge vessel for storing nitrogen gas desorbed from said nitrogen adsorbed column and a portion of the nitrogen stored therein from said second surge vessel after said air supply operation period; a device for removing the nitrogen and flowing the nitrogen through the column on which the nitrogen has been adsorbed to wash the column; and a device for controlling the nitrogen wash duration, the nitrogen wash duration control device controlling the second surge. a current amount monitoring device associated with the container, the monitoring device being activated when the pressure level or height level of nitrogen gas in the second surge container reaches a predetermined set value; 16. The circulation system of claim 15, wherein the device is operative to initiate valve closure to terminate the nitrogen flush. 17) In combination with the surge container, the current amount monitoring device further includes a moving device for extending the duration of the nitrogen flushing period by a preset time interval of operation of the monitoring device, 17. A circulation system according to claim 16, characterized in that the closing of a predetermined cell is delayed for a time interval 18) combined with said effluent storage container. The current inventory monitoring device further includes a moving device for extending the duration of the air supply operation period by a preset time interval of operation of the monitoring device, and the current amount monitoring device further includes a moving device for extending the duration of the air supply operation period by a preset time interval of operation of the monitoring device, 17. The circulation system according to claim 16, wherein the closing of the valve is delayed. 19) The current volume monitoring device in combination with the effluent storage surge container further includes a slowing device for extending the duration of the air supply operation period by a predetermined time interval of operation of the monitoring device. 16. The circulation system according to claim 15, wherein the valve is opened and closed during the extended time interval. 20) A claim further comprising a device for controlling the duration of the vacuum desorption step, the control device comprising a vacuum level sensor switch operatively associated with the nitrogen thermosorption column. The circulation system according to item 15. 21) Air or nitrogen free of water and carbon dioxide is introduced into a selective retention column, and the unadsorbed oxygen-enriched effluent is collected in a first surge vessel, and the column with adsorbed A vacuum is applied to the column which has been flushed with a flow of high purity nitrogen gas taken from a second surge vessel and adsorbed with nitrogen to desorb the nitrogen, and the desorbed nitrogen effluent is transferred to the second surge vessel. 9 and flow the oxygen-enriched gas removed from the first surge vessel into the column to repressurize the column; and/or a device for controlling the duration of said air supply and/or cleaning of said nitrogen-adsorbed adsorbent bed, including a current amount monitoring device in combination with a second surge vessel; The present quantity monitoring device is activated when the detected pressure level or the detected height level of the gas collected in the surge vessel reaches a predetermined threshold value, and the monitoring device controls the closing of the valve. Vacuum swing adsorption system for fractionating air, characterized in that it is operable to initiate a cut and end the air introduction period and/or the nitrogen cleaning period. 22) The vacuum swing adsorption system according to claim 21, wherein the first surge container is expandable and retractable. 25) Claim 21 (D vacuum swing adsorption system), wherein the second surge container is expandable and retractable.