EP0042159A1
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EP
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Air fractionation by pressure swing adsorption
Assignee: Air Products and Chemicals Inc
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Filing: 1981-06-12
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Granted: —
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Expires: 2001-06-12
Abstract
Abstract Improved oxygen recovery in the operation of a pressure swing adsorption system for air fractionation is obtained by passng the air, freed of water and CO2, through an adsorbent bed maintained at elevated temperature throughout the cycle and which is selective for retention of nitrogen, and consequent withdrawal of an oxygen-rich primary effluent product. In a preferred embodiment ambient air is passed through a pretreater section providing an adsorbent bed for removal of water and carbon dioxide. The thus purified air is compressed with consequent rise in temperature and then only partly cooled down by exchange with cooler desorbed and purged nitrogen-rich gas products withdrawn from the main adsorbent beds. These nitrogen-rich products thus heated by the exchange are employed in regenerating a water and carbon dioxide laden bed of the pretreater section. While the adsorption-desorption is operated in a pressure swing cycle, the pretreater section is operated in an independent thermal swing cycle. Alternatively, the feed air may be compressed prior to its introduction into the pretreater and the thus generated heat utilized by heat exchange for heating the purified air effluent to be fractionated.
Inventors
- 👤 Shivaji Sircar
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-04 10:28
CPC Classifications
B; B01; B01D; B01D53/00; B01D53/02; B01D53/04; B01D53/0462; B01D53/047; B01D2256/00; B01D2256/10; B01D2256/12; B01D2257/00; B01D2257/10; B01D2257/102; B01D2257/50; B01D2257/504; B01D2257/80; B01D2259/00; B01D2259/40; B01D2259/40011; B01D2259/40043; B01D2259/4005; B01D2259/40052; B01D2259/40058; B01D2259/40069; B01D2259/40077; B01D2259/40081; B01D2259/402; B01D2259/404; B01D2259/406; B01D2259/4061; Y; Y02; Y02C; Y02C20/00; Y02C20/40
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
353 words
In the method of producing oxygen-enriched air form ambient air, by pressure swing adsor;tion scheme, whereby nitrogen is selectively adsorbed on an adsorbent and an oxygen-enriched effluent stream is discharged as primary product, in a system comprising a plurality of main adsorbent beds operated in parallel in timed sequence, the improvement which comprises the following steps carried in recited cyclic sequence: (1) during an adsorption step introducing the feed air, prveiously freed of water and C0 2 , at elevated temperature and at superatmospheric pressure into a main sorbent bed which is selective for retention of nitrogen and which is operated at near the elevated base temperature of the feed air throughout the bed during the entire cycle, while withdrawing from said bed an unadsorbed oxygen-enriched effluent stream as primary product, (2) interrupting the introduction of feed air to said bed at the conclusion of said adsorption step and reducing the pressure of the bed by withdrawltherefrom of a secondary gas stream including voids gas and desorbed gas rich in nitrogen, said secondary gas being withdrawn in a direction opposite to that of the initial air feed direction, (3) purging said bed to remove part of the residual sorbed nitrogen therefrom when said bed is at the reduced pressure, by passing through the bed counter to initial feed direction a part of the oxygen-enriched product gas which is at the base temperature of the main beds, (4) repressuring the purged bed to an intermediate pressure level between that at step (1) and that at step (3), by flowing into the bed at the air inlet end thereof at least a portion of the secondary gas previously withdrawn from a companion bed at about the base temperature of the main beds, (5) further repressuring the bed to about the superatmospheric pressure level of step (1) by flowing thereinto a part of the oxygen-enriched product gas, said oxygen-enriched gas being introduced into said bed in a direction counter to that of step (1) above at about the base temperature of the main beds, and (6) repeating the recited sequence of steps beginning with step (1).
Claim 2
Dependent Claim
353 words
In the method of producing oxygen-enriched air form ambient air, by pressure swing adsor;tion scheme, whereby nitrogen is selectively adsorbed on an adsorbent and an oxygen-enriched effluent stream is discharged as primary product, in a system comprising a plurality of main adsorbent beds operated in parallel in timed sequence, the improvement which comprises the following steps carried in recited cyclic sequence: (1) during an adsorption step introducing the feed air, prveiously freed of water and C0 2 , at elevated temperature and at superatmospheric pressure into a main sorbent bed which is selective for retention of nitrogen and which is operated at near the elevated base temperature of the feed air throughout the bed during the entire cycle, while withdrawing from said bed an unadsorbed oxygen-enriched effluent stream as primary product, (2) interrupting the introduction of feed air to said bed at the conclusion of said adsorption step and reducing the pressure of the bed by withdrawltherefrom of a secondary gas stream including voids gas and desorbed gas rich in nitrogen, said secondary gas being withdrawn in a direction opposite to that of the initial air feed direction, (3) purging said bed to remove part of the residual sorbed nitrogen therefrom when said bed is at the reduced pressure, by passing through the bed counter to initial feed direction a part of the oxygen-enriched product gas which is at the base temperature of the main beds, (4) repressuring the purged bed to an intermediate pressure level between that at step (1) and that at step (3), by flowing into the bed at the air inlet end thereof at least a portion of the secondary gas previously withdrawn from a companion bed at about the base temperature of the main beds, (5) further repressuring the bed to about the superatmospheric pressure level of step (1) by flowing thereinto a part of the oxygen-enriched product gas, said oxygen-enriched gas being introduced into said bed in a direction counter to that of step (1) above at about the base temperature of the main beds, and (6) repeating the recited sequence of steps beginning with step (1).
Claim 3
Dependent Claim
24 words
The improvement as defined in Claim 1 wherein said feed air in step (1) is introduced at a temperature of at least aobut 90°F.
Claim 4
Dependent Claim
26 words
The improvement as defined in Claim 1 wherein said feed air in step (1) is introduced at a temperature in the range of 90° to 180°F.
Claim 5
Dependent Claim
63 words
The improvement as defined in Claim 3 wherein said temperature of the feed air in the recieted range is obtained by compressing air previously freed of water and C0 2 with consequent heating of said air, followed by cooling to said recited range at least in part by heat exchange with a cooler secondary gas stream comprising desorbed gases from the main beds.
Claim 6
Dependent Claim
57 words
The method as defined in Claim 3 wherein said temperature of the feed air in the recited range is obtained by compressing ambient air prior to removal of water and C0 2 therefrom and utilizing the heat of such compression, at least in part, to heat the purified air to the desired temperature in the recited range.
Claim 7
Dependent Claim
82 words
The improvement as defined in Claim 1 wherein said system of parallel main sorbent beds comprises at least three such beds and said pressure reduction in step (2) is carried out in at least two stages, during the first such stage of pressure reduction the withdrawn gas being transferred to a second companion bed then at lower pressure until approximate pressure equalization between the beds is attained and during the last pressure reduction stage further withdrawn gas is removed from the system.
Claim 8
Dependent Claim
46 words
The improvement as defined in Claim 6 wherein the effluent gas during the second stage of pressure reduction is at least in part passed through a heat exchanger for heat exchange with compressed hot feed air and then used as regenerating gas in a pretreatment column.
Claim 9
Dependent Claim
51 words
The improvement as defined in Claim 6 wherein the purge gas effluent from the main columns during said purging step (3) is at least in part passed through a heat exchanger for heat exchange with compressed hot feed air and then used as regenerating gas for one of the pretreatment columns.
Claim 10
Dependent Claim
114 words
The improvement as defined in Claim 1 wherein said systems of parallel main sorbent beds comprises at least four such beds and said pressure reduction in step (2) is carried out in at least three stages, during the first stage of pressure reduction the withdrawn gas being transferred to a second companion bed • then at lower pressure until approximate pressure equalization between the two beds is attained, during the second stage of pressure reduction the withdrawn gas being transferred to a third companion bed then at lower pressure until approximate pressure equalization between the beds is attained, and during the third stage of pressure reduction the withdrawn gas is removed from the system.
Claim 11
Dependent Claim
48 words
The improvement as defined in claim 9 wherein the effluent gas during the third stage of pressure reduction is at least in part passed through a heat exchanger for heat exchange with hot compressed feed air and then used as regenerating gas for one of the pretreatment columns.
Claim 12
Dependent Claim
52 words
The improvement as defined in claim 9 wherein the purge gas effluent withdrawn from the main columns during said purging step (3) is at least in part passed through a heat exchanger for heat exchange with compressed hot feed air and then used as regenerating gas for one of the pretreatment columns.
Claim 13
Dependent Claim
144 words
The improvement as defined in claim 1 wherein said system of parallel main sorbent beds comprises at least five such beds and the said pressure reduction in step (2) is carried out in at least four stages, during the first stage of pressure reduction the withdrawn gas being transferred to a second companion bed then at lower pressure until approximate pressure equalization between the two beds is attained, during the second stage of pressure reduction the withdrawn gas being transferred to a third companion bed then at lower pressure until approximate pressure equalization between the beds is attained, during the third stage of pressure reduction the withdrawn gas being transferred to a fourth companion bed then at lower pressure until approximate pressure equalization between the beds is attained, and during the fourth stage of pressure reduction the withdrawn gas is removed from the system.
Claim 14
Dependent Claim
48 words
The improvement as defined in claim 12 wherein the effluent gas during the fourth stage of pressure reduction is at least in part passed through a heat exchanger for heat exchange with hot compressed feed air and then used as regenerating gas for one of the pretreatment columns.
Claim 15
Dependent Claim
52 words
The improvement as defined in claim 12 wherein the purge gas effluent from the main columns during the said purging step (3) is at least in part passed through a heat exchanger for heat exchange with compressed hot feed air and then used as regenerating gas for one of the pretreatment columns.
Claim 16
Dependent Claim
61 words
The improvement as defined in claim 1 wherein said air feed of H 2 0 and C0 2 is obtained by passing ambient air through a pretreatment section comprising an absorbent bed selective in retention of H 2 0 and C0 2 and removal of these components from air containing the same, said pretreatment section being operated in temperature swing mode.
Claim 17
Dependent Claim
69 words
The improvement as defined in claim 15 wherein said pretreatment section comprises at least two absorbent beds selective in retention of H 2 0 and C0 2 operated in parallel such that while one bed is removing the H 2 0 and C0 2 impurities by adsorption at near ambient temperature, another bed containing sorbed H 2 0 and C0 2 is being regenerated at higher than ambient temperature.
Claim 18
Dependent Claim
45 words
The improvement as defined in claim 16 wherein said regeneration is effected by passing heated nitrogen-rich effluent gas from said main columns obtained from recited step (2) and/or step (3), wherein said effluent gas has been heated by heat exchange with compressed hot feed air.
Claim 19
Dependent Claim
23 words
The improvement as defined in claim 15 wherein said passage of ambient air through the pretreatment beds is effected at near ambient pressure.
Claim 20
Dependent Claim
22 words
The improvement as defined in claim 15 wherein said passage of ambient air through the pretreatment beds is effected at superatmospheric pressure.
Claim 21
Dependent Claim
162 words
The improvement as defined in claim 1 wherein said air feed of H 2 0 and C0 2 is obtained by passing ambient air through a pretreatment section comprising an adsorbent bed selective in removal of H 2 0 and C0 2 from an ambient air stream containing these components, and the thus purified air stream is heated by compression to a temperature level above that of the elevated base temperature at which said air is introduced into the main sorbent bed and thereafter cooled at least in part by heat exchange to said base temperature at which it is introduced into said main sorbent bed, the heat exchange being effected with cooler nitrogn-rich gas stream comprising effluent gases from said main columns during the depressurization and the purging steps and the said nitrogen-rich gas thus heated by said heat exchange being utilized in regeneration of an adsorbent bed of said pretreater section containing sorbed H 2 0 and C0 2 .
Claim 22
Dependent Claim
123 words
The improvement as defined in claim 1 wherein said air freed of H 2 0 and C0 2 is obtained by (a) compressing the ambient air to the superatmospheric pressure level of adsorption with consequent temperature rise of the air, (b) cooling the compressed air to near ambient temperature by a series of heat exchanges with cooler gases and other coolants, (c) passing the compressed gas at near ambient temperature through the adsorbent bed in the pretreatment section, and (d) heat exchanging the H 2 0 and C0 2 free air effluent from the pretreatment bed with part of the hot feed gas to raise its temperature to the base temperature level at which said air is introduced into the main sorbent bed.
References Cited (Backward Citations)
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