Method and apparatus for separating gases

A method and apparatus for the separation of gases by preferential adsorption of at least one of the gases in which at least three adsorption zones are used, at least two of which are arranged in series to form the separation zone while at least one other is being regenerated for re-use in the separation zone, and in which periodically a fresh zone is added to the end of the separation section from which the product gas is recovered and the zone forming the first zone of the separation section is removed for regeneration whereby each zone is successively incorporated into the separation section and subsequently removed from it and regenerated ready for reincorporation into the separation section. Improved utilization of adsorbent and reduced loss of product gas for regeneration purposes is thereby achieved without loss of product purity.

Skip to:  ·  Claims  ·  References Cited  · Patent History  ·  Patent History

Claims

1. A method of separating a purified gas from a mixture thereof with at least one gaseous contaminant by pressure swing adsorption, said method comprising the steps of

a. providing an adsorption unit comprising x zones of adsorbent material which selectively adsorbs said gaseous contaminant, x being a whole number of at least three;
b. passing the gas mixture at a first pressure through y of the zones of said adsorption unit arranged in series with respect to the flow of the gas mixture therethrough, y being a whole number of from 2 to x-1 and said y zones constituting a separation section of said adsorption unit;
c. recovering from the last zone of said separation section a purified gas in which the concentration of the contaminant does not exceed a predetermined value which is below the concentration of contaminant in the gas mixture;
d. before the concentration of the contaminant in said purified gas rises above said predetermined value, but after the concentration of said contaminant in the gas stream leaving the zone forming the penultimate zone of said separation section has exceeded said predetermined value, adding another zone of said adsorption unit to the end of said separation section, expressed in terms of the direction of flow of said gas mixture through the separation section whereby said added zone now forms the last zone of said separation section;
e. removing from said separation section the zone forming the first zone of the section whereby the zone next to it in the separation section now becomes the first zone;
f. purging the adsorbent in said removed zone of adsorbed material by passing a purge gas through it at a second pressure which is lower than the first pressure whereby to prepare said zone for re-use in the adsorption section commencing as the last zone of said section; and
g. periodically repeating steps (d), (e) and (f) whereby each zone of said unit is in successive periods incorporated into the separation section as the last zone thereof, subsequently periodically progressed along said section until it becomes the first zone thereof, and then purged ready for re-incorporation into the separation section in a subsequent period.

2. A method as claimed in claim 1 in which x is at least 4 and y equals x-2, and in which each zone is subjected to a separate step of re-pressurisation subsequent to the purging step but before being incorporated into the separation section.

3. A method as claimed in claim 2 in which steps (d) and (e) are operated simultaneously.

4. A method as claimed in claim 2 in which substantially equal periods of time are alowed for the step of purging and the step of re-pressurisation.

5. A method as claimed in claim 2 in which x equals 4.

6. A method as claimed in claim 1 in which x is at least 5 and y equals x-3, and in which each zone is subjected to separate steps of depressurisation after being removed from the separation section and prior to the purging step, and of re-pressurisation subsequent to the purging step and before being incorporated into the separation section.

7. A method as claimed in claim 1 in which the purge gas is provided by a portion of the purified gas at reduced pressure.

8. A method as claimed in claim 1 which further includes causing a part of the gas mixture to by-pass the separation section and thereafter combining said part with the purified gas recovered from said separation section to form a combined gas stream, and controlling the flow rate of said part relative to the flow of the purified gas from said separation section so as to maintain the composition of the combined stream constant.

9. A method as claimed in claim 1 for the recovery of helium from helium-containing gas exhaled by divers inhaling a helium-diluted air composition under pressure.

10. A method as claimed in claim 9 in which the adsorbent is coconut shell-activated carbon.

11. A method as claimed in claim 9 in which the exhaled helium-containing gas is passed to a buffer vessel and thereafter compressed to a first elevated pressure and passed at said elevated pressure to the adsorption unit, and the purified helium recovered from the adsorption unit is further compressed to a second elevated pressure for subsequent recirculation for inhalation.

12. Apparatus for separating a purified gas from a mixture thereof with at least one gaseous contaminant, said apparatus comprising a pressure swing adsorption unit comprising a plurality of adsorption zones for adsorbing said contaminant from said mixture and means for purging adsobent of adsorbed contaminant, said adsorption unit including

at least four compartments for adsorbent, each having a gas inlet and a gas outlet for gas to be passed through adsorbent in the compartment, each compartment forming a separately isolatable adsorption zone,
an inlet for the gas mixtures to be separated in said unit,
an outlet for purified gas,
an inlet manifold connected to the inlet for the gas mixture,
a purified gas outlet manifold connected to the outlet for the purified product,
said means for purging adsorbent comprising a purge gas manifold,
a waste gas manifold,
first conduit means for connecting the inlet of each compartment to the inlet manifold, with an inlet valve in the conduit between each compartment inlet and the inlet manifold,
second conduit means for connecting the outlet from each compartment to the purified gas manifold, with an outlet valve in the conduit between each compartment outlet and the outlet manifold,
third conduit means for connecting the purge gas manifold to the outlet from each compartment, with a purge gas inlet valve in the conduit between each compartment outlet and the purge gas manifold,
fourth conduit means for connecting the inlet to each compartment to the waste gas manifold, there being a waste gas outlet valve between each compartment inlet and the waste gas manifold, and
fifth conduit means adapted to connect the compartments together for flow of gas therethrough with the outlet of each compartment connected to the inlet of the next compartment, there being a valve in the conduit between the outlet of each compartment and the inlet of the next compartment, said valves being arranged such that at least a first and a second of said compartments are connected in series to provide a separation section between the inlet manifold and the outlet manifold for flow of gas therethrough and in that order with respect to the gas flow, at least a third compartment is connected to the outlet manifold for re-pressurisation and at least a fourth compartment is connected for gas flow therethrough from the purge gas manifold to the waste gas manifold for purging, and automatic valve control means adapted periodically to switch the valves to connect said third compartment in series with said second compartment in said separation section to form the last compartment in said section, expressed in terms of flow of gas therethrough, disconnect said fourth compartment from said purge gas manifold and said waste gas manifold and connect it to said outlet manifold for re-pressurisation, and disconnect said first compartment from said separation section and connect it between the purge gas manifold and the waste gas manifold for purging.

13. Apparatus as claimed in claim 12 in which the valves are electrically operated solenoid valves.

14. Apparatus as claimed in claim 12 including electronic timing means for controlling the operation of the valves.

15. Apparatus as claimed in claim 12 further including means for compressing feed gas to be supplied to the unit, means for compressing product gas recovered from the unit, and prime mover means connected to each of said compressing means for driving same, and means drivably connected to said prime mover means for powering the operation of the pressure swing adsorption unit.

16. Apparatus as claimed in claim 15 further including means for cooling each of the compressing means, said cooling means including means drivably connected to said prime mover means for circulating a cooling medium through said compressing means.

17. Apparatus as claimed in claim 15 further including a buffer bessel adapted to store gas mixture for feeding to the first-mentioned compressor means.

18. Apparatus as claimed in claim 15 arranged in two packs, the first comprising the pressure swing adsorption unit and the second comprising the two compressing means, the prime mover means and the means for powering the operation of the pressure swing adsorption unit.

19. Apparatus as claimed in claim 15 applied to the recovery of helium from helium-containing gas exhaled by divers inhaling a helium-diluted air composition under pressure.

20. Apparatus as claimed in claim 12 further including conduit means connecting said outlet manifold with said purge gas manifold, said conduit means including a pressure reducing valve whereby a portion of said purified gas in said outlet manifold is passed at reduced pressure as purge gas to said purge gas manifold.

21. Apparartus as claimed in claim 20 in which said adsorption unit contains four compartments.

22. Apparatus for separating a purified gas from a mixture thereof with at least one gaseous contaminant, said apparatus comprising a pressure swing adsorption unit comprising a plurality of adsorption zones for adsorbing said contaminant from said mixture and means for purging adsorbent of adsorbed contaminant, said adsorption unit including

at least three compartments for adsorbent, each having a gas inlet and a gas outlet for gas to be passed through adsorbent in the compartment, each compartment forming a separately isolatable adsorption zone,
an inlet for the gas mixture to be separated in said unit,
an outlet for purified gas,
an inlet manifold connected to the inlet for the gas mixture,
a purified gas outlet manifold connected to the outlet for the purified product,
a purge gas manifold,
a waste gas manifold,
first conduit means for connecting the inlet of each compartment to the inlet manifold, with an inlet valve in the conduit between each compartment inlet and the inlet manifold,
second conduit means for connecting the outlet from each compartment to the purified gas manifold, with an outlet valve in the conduit between each compartment outlet and the outlet manifold,
third conduit means for connecting the purge gas manifold to the outlet from each compartment, with a purge gas inlet valve in the conduit between each compartment outlet and the purge gas manifold,
fourth conduit means for connecting the inlet to each compartment to the waste gas manifold, there being a waste gas outlet valve between each compartment inlet and the waste gas manifold, and
fifth conduit means adapted to connect the compartments together for flow of gas therethrough with the outlet of each compartment connected to the inlet compartment, there being a valve in the conduit between the outlet of each compartment and the inlet of the next compartment, said valves being arranged such that at least a first and a second of said compartments are connected in series to provide a separation section between the inlet manifold and the outlet manifold for flow of gas therethrough and in that order with respect to the gas flow, and at least a third compartment is connected for gas flow therethrough from the purge gas manifold to the waste gas manifold for purging, and automatic valve control means adapted periodically to switch the valves to disconnect said third compartment from said purge gas manifold and said waste gas manifold and connect it in series with said second compartment in said separation section to form the last compartment in said section, expressed in terms of flow of gas therethrough and disconnect said first compartment from said separation section and connect it between the purge gas manifold and the waste gas manifold for purging.

23. Apparatus as claimed in claim 22 and further including gas compressor means having a gas inlet communicating with the outlet of said waste gas manifold and a compressed gas outlet communicating with the inlet to said separation section, waste gas conduit means also communicating with said second waste gas manifold, valve means adapted to direct gas recovered from said third compartment to the one or the other of said waste gas conduit means and said compressor inlet and valve control means adapted to control the valve means to direct the gas recovered from said third compartment initially to said compressor inlet and subsequently to divert gas to said waste gas conduit means at or before the occurrence of a rapid increase in the concentration of contaminant in said gas.

24. Apparatus as claimed in claim 23 wherein said valve control means comprise sensor means for sensing the level of concentration of contaminant in said gas recovered from said third compartment and means responsive to said sensor means to operate the valve to direct said gas to said compressor inlet when said sensed level is below a predetermined level and to direct said gas to said waste conduit means when said sensed level exceeds said predetermined level.

25. Apparatus as claimed in claim 23 wherein said valve control means comprise sensor means for sensing the pressure of said gas recovered from said third compartment and means responsive to said sensor means to operate the valve to direct said gas to said compressor inlet when said sensed pressure exceeds a predetermined level and to direct said gas to said waste conduit means when said sensed level is below said predetermined level.

26. Apparatus as claimed in claim 23 wherein said valve control means comprises timing means adapted to operate said valve to divert said gas recovered from said third compartment from said compressor inlet to said waste conduit means at a predetermined time after the commencement of evacuation of said third compartment.

27. A method of separating a purified gas from a mixture thereof with at least one gaseous contaminant, said method comprising the steps of

a. providing an adsorption unit comprising x zones of adsorbent material which selectively adsorbs said gaseous contaminant, x being a whole number of at least three;
b. passing the gas mixture at a first pressure through y of the zones of said adsorption unit arranged in series with respect to the flow of the gas mixture therethrough, y being a whole number of from 2 to x-1 and said y zones constituting a separation section of said adsorption unit;
c. recovering from the last zone of said separation section a purified gas in which the concentration of the contaminant does not exceed a predetermined value which is below the concentration of contaminant in the gas mixture;
d. before the concentration of the contaminant in said purified gas rises above said predetermined value, but after the concentration of said contaminant in the gas stream leaving the zone forming the penultimate zone of said separation section has exceeded said predetermined value, adding another zone of said adsorption unit to the end of said separation section, expressed in terms of the direction of flow of said gas mixture through the separation section whereby said added zone now forms the last zone of said separation section;
e. removing from said separation section the zone forming the first zone of the section whereby the zone next to it in the separation section now becomes the first zone;
f. regenerating the adsorbent in said removed zone by evacuation of said zone;
g. periodically repeating steps (d), (e) and (f) whereby each zone of said unit is in successive periods incorporated into the separation section as the last zone thereof, subsequently periodically progressed along said section until it becomes the first zone thereof, and then treated to regenerate the adsorbent therein ready for re-incorporation into the separation section in a subsequent period.

28. A method as claimed in claim 27 further including the step of recycling the gas initially exiting from said removed zone during the evacuation procedure of step (f) to the inlet of the separation section to be passed therethrough at substantially said first pressure, said recycle being continued until not later than the occurrence of a rapid increase in concentration of said contaminant in said exit gas.

29. A method as claimed in claim 28 which includes sensing the level of concentration of said contaminant in said exit gas and terminating the recycle of said exit gas when the level of contaminant rises to a predetermined level which is not greater than that which corresponds to the occurrence of said rapid increase.

30. A method as claimed in claim 27 which includes sensing the pressure of said exit gas and terminating the recycle of said exit gas when said pressure drops to a predetermined pressure which is not lower than the pressure at which said rapid increase in concentration of contaminant occurs.

31. A method as claimed in claim 27 in which said recycle is terminated at the end of a predetermined time interval after the commencement of the evacuation procedure of step (f), the length of said time interval being at most the length of the time interval at which said rapid increase of concentration of contaminant occurs.

32. A method of separating a purified gas from a mixture thereof with at least one gaseous contaminant by pressure swing adsorption, said method comprising the steps of

a. providing an adsorption unit comprising x zones of adsorbent material which selectively adsorbs said gaseous contaminant, x being a whole number of at least three;
b. passing the gas mixture at a first pressure through y of the zones of said adsorption unit arranged in series with respect to the flow of the gas mixture therethrough, y being a whole number of from 2 to x-1 and said y zones constituting a separation section of said adsorption unit;
c. recovering from the last zone of said separation section a purified gas in which the concentration of the contaminant does not exceed a predetermined value which is below the concentration of contaminant in the gas mixture;
d. before the concentration of the contaminant in said purified gas rises above said predetermined value, but after the concentration of said contaminant in the gas stream leaving the zone forming the penultimate zone of said separation section has exceeded said predetermined value, adding another zone of said adsorption unit to the end of said separation section, expressed in terms of the direction of flow of said gas mixture through the separation section whereby said added zone now forms the last zone of said separation section;
e. removing from said separation section the zone forming the first zone of the section whereby the zone next to it in the separation section now becomes the first zone;
f. reducing the pressure in said removed zone and purging the adsorbent in said removed zone of adsorbed material by passing a purge gas through it at a second pressure which is lower than the first pressure whereby to prepare said zone for re-use in the adsorption section commencing as the last zone of said section;
g. periodically repeating steps (d), (e) and (f) whereby each zone of said unit is in successive periods incorporated into the separation section as the last zone thereof, subsequently periodicaly progressed along said section until it becomes the first zone thereof, and then purged ready for re-incorporation into the separation section in a subsequent period; and
h. recycling the gas initially exiting from said removed zone during the step of reducing the pressure in said zone to the inlet of the separation section to be passed therethrough at substantially said first pressure, said recycle being continued until not later than the occurrence of a rapid increase in concentration of said contaminant in said exit gas.

33. A method as claimed in claim 32 which includes sensing the level of concentration of said contaminant in said exit gas and terminating the recycle of said exit gas when the level of contaminant rises to a predetermined level which is not greater than that which corresponds to the occurrence of said rapid increase.

34. A method as claimed in claim 32 which includes sensing the pressure of said exit gas and terminating the recycle of said exit gas when said pressure drops to a predetermined pressure which is not lower than the pressure at which said rapid increase in concentration of contaminant occurs.

35. A method as claimed in claim 32 in which said recycle is terminated at the end of a predetermined time interval after the commencement of the evacuation procedure of step (f), the length of said time interval being at most the length of the time interval at which said rapid increase of concentration of contaminant occurs.

36. Apparatus for separating a purified gas from a mixture thereof with at least one gaseous contaminant, said apparatus comprising an adsorption unit comprising a plurality of adsorption zones for adsorbing said contaminant from said mixture and means for regenerating adsorbent, said adsorption unit including

at least three compartments for adsorbent, each having a gas inlet and a gas outlet for gas to be passed through adsorbent in the compartment, each compartment forming a separately isolatable adsorption zone,
an inlet for the gas mixture to be separated in said unit,
an outlet for purified gas,
an inlet manifold connected to the inlet for the gas mixture,
a purified gas outlet manifold connected to the outlet for the purified product,
said regenerating means comprising means for evacuating the adsorption zones,
first conduit means for connecting the inlet of each compartment to the inlet manifold, with an inlet valve in the conduit between each compartment inlet and the inlet manifold,
second conduit means for connecting the outlet from each compartment to the purified gas manifold, with an outlet valve in the conduit between each compartment outlet and the outlet manifold, third conduit means for connecting the interior of each compartment to said evacuating means, there being a valve between each compartment interior and the evacuating means, and
fourth conduit means adapted to connect the compartments together for flow of gas therethrough with the outlet of each compartment connected to the inlet of the next compartment, there being a valve in the conduit between the outlet of each compartment and the inlet of the next compartment, said valves being arranged such that at least a first and a second of said compartments are connected in series to provide a separation section between the inlet manifold and the outlet manifold for flow of gas therethrough and in that order with respect to the gas flow, and at least a third compartment is connected to said evacuating means for regeneration of the adsorbent therein, and automatic valve control means adapted periodically to switch the valves to disconnect said third compartment from said evacuating means and connect it in series with said second compartment in said separation section to form the last compartment in said section, expressed in terms of flow of gas therethrough and disconnect said first compartment from said separation section and connect it to said evacuating means for regeneration of the adsorbent therein.
Referenced Cited
U.S. Patent Documents
3006438 October 1961 DeYarmett
3085379 April 1963 Kiyonaga et al.
3176445 April 1965 Collins et al.
3252268 May 1966 Stark
3257773 June 1966 Conners et al.
3703068 November 1972 Wagner
Patent History
Patent number: RE29941
Type: Grant
Filed: Mar 13, 1978
Date of Patent: Mar 20, 1979
Assignee: Petrocarbon Developments Ltd. (Manchester)
Inventor: Graham Bird (Papillion, NE)
Primary Examiner: Robert H. Spitzer
Law Firm: Browdy and Neimark
Application Number: 5/885,592
Classifications
Current U.S. Class: 55/21; 55/58; 55/62; 55/66; 55/162; 55/163; 55/179
International Classification: B01D 1506; B01D 5304;