Recovery of trace gases from gas streams

Claim 2

A pressure swing adsorption process for the recovery of at least one gaseous impurity from a gas stream comprising repeatedly performing in sequence the steps: (a) cocurrently charging said gas stream at a superatmospheric adsorption pressure into a single adsorption vessel containing an adsorbent which selectively adsorbs said at least one gaseous impurity, thereby adsorbing said at least one gaseous impurity, while cocurrently discharging from said single adsorption vessel a nonadsorbed gas stream depleted in said at least one gas impurity; (b) partially countercurrently depressurizing said single adsorption vessel, thereby discharging gas therefrom, and collecting the discharged gas in a gas storage vessel; (c) further countercurrently depressurizing said single adsorption vessel, thereby discharging therefrom a gas product enriched in said at least one gaseous impurity; (d) partially pressurizing said single adsorption vessel by cocurrently charging thereinto gas from said gas storage vessel; and (e) further pressurizing said single adsorption vessel to said superatmospheric adsorption pressure by cocurrently charging said gas stream thereinto.

Claim 3

The process of claim 1, wherein step (b) is at least partly carried out by pumping gas from said adsorption vessel to said gas storage vessel.

Claim 4

The process of claim 2, wherein step (b) is carried out until the pressure in said adsorption vessel is reduced to about 1 to about 3 bara.

Claim 5

The process of claim 1, claim 2, or claim 3, wherein step (d) is at least partly carried out by pumping gas from said gas storage vessel to said adsorption vessel.

Claim 6

The process of claim 4, wherein steps (a) to (e) are carried out using a single pump means.

Claim 7

The process of claim 4, wherein step (c) is carried out by countercurrently evacuating said single adsorption vessel to subatmospheric pressure.

Claim 8

The process of claim 4, wherein step (d) is carried out by first permitting gas to flow from said gas storage vessel to said adsorption vessel without the aid of a pump until the pressure in these vessels is about equal, and then pumping additional gas from said gas storage vessel to said adsorption vessel.

Claim 9

The process of claim 1, claim 2 or claim 3, wherein step (c) is carried out by countercurrently evacuating said single adsorption vessel to subatmospheric pressure.

Claim 10

The process of claim 8, wherein said subatmospheric pressure is in the range of about 0.05 to about 0.8 bara.

Claim 11

The process of claim 9, wherein said superatmospheric pressure is in the range of about 1.5 to about 5 bara.

Claim 12

The process of claim 8, wherein said subatmospheric pressure is in the range of about 0.1 to about 0.3 bara.

Claim 13

The process of claim 2 or claim 3, wherein steps (a), (b), (c) and (e) are carried out using a single pump means.

Claim 14

The process of claim 3, wherein step (b) is carried out by first permitting gas to flow from said adsorption vessel to said gas storage vessel without the aid of a pump until the pressure in these vessels is about equal, and then pumping additional gas from said adsorption vessel to said gas storage vessel.

Claim 15

The process of claim 1, wherein steps (a), (c) and (e) are carried out using a single pump means.

Claim 16

The process of claim 14, wherein said single pump means is used to charge feed gas into a fed gas reservoir during at least part of step (b).

Claim 17

The process of claim 14, wherein said single pump means is used to charge ted gas into a fed gas reservoir during at least part of step (d).

Claim 18

The process of claim 1, wherein said adsorption pressure is in the range of about 1.1 to about 20 bara.

Claim 19

The process of claim 1, further comprising, prior to step (a) passing the gas stream through a gas reactor column to remove components that are chemically reactable.

Claim 20

The process of claim 1 or claim 18, further comprising prior to step (a) passing the gas stream through a solvent scrubber to remove components that are soluble or dispersible in the solvent.

Claim 21

The process of claim 1, further comprising, subsequent to step (c), further purifying said at least one gaseous impurity by subjecting said gas product enriched in said at least one gaseous impurity to cryogenic condensation.

Claim 22

Apparatus for separating a strongly adsorbed gas from a gas mixture comprising: (a) an adsorption vessel containing an adsorbent which selectively adsorbs said strongly adsorbed gas from said gas mixture and having a feed gas inlet end and a nonadsorbed gas outlet end; (b) a gas storage vessel; (c) pump means adaptable for charging feed gas into said adsorption vessel and for evacuating gas from said adsorption vessel; (d) first conduit means connecting the inlet end of said adsorption vessel with said gas storage vessel; (e) second conduit means connecting the inlet end of said pump means with a source of feed gas and the inlet end of said adsorption vessel; (f) Third conduit means connecting the outlet end of said pump means with the inlet end of said adsorption vessel and strongly adsorbed component discharge conduit means; (g) fourth conduit means connecting the nonadsorbed gas outlet end of said adsorption vessel with a nonadsorbed gas discharge conduit means; (h) valve means associated with said first conduit means for controlling the flow of gas between said adsorption vessel and said void space gas storage vessel; (i) valve means associated with said second conduit means for selectively providing communication between said source of feed gas and said inlet end of said pump means or between said inlet end of said adsorption vessel and said inlet end of said pump means; and (j) valve means associated with said third conduit means for selectively providing communication between said outlet end of said pump means and said inlet end of said adsorption vessel or between said inlet end of said pump means and said strongly adsorbed component discharge conduit means; and (k) valve means associated with said fourth conduit means for controlling the flow of gas between the nonadsorbed gas outlet end of said adsorption vessel and said nonadsorbed gas discharge conduit means.

Claim 23

Apparatus for separating a strongly adsorbed gas from a gas mixture comprising: (a) an adsorption vessel containing an adsorbent which selectively adsorbs said strongly adsorbed gas from said gas mixture and having a feed gas inlet end and a nonadsorbed gas outlet end; (b) a gas storage vessel; (c) pump means adaptable for charging feed gas into said adsorption vessel and for evacuating gas from said adsorption vessel; (d) first conduit means connecting the inlet end of said adsorption vessel with said gas storage vessel; (e) second conduit means connecting the inlet end of said pump means with a source of feed gas and the inlet end of said adsorption vessel; (f) Third conduit means connecting the outlet end of said pump means with the inlet end of said adsorption vessel and strongly adsorbed component discharge conduit means; (g) fourth conduit means connecting the nonadsorbed gas outlet end of said adsorption vessel with a nonadsorbed gas discharge conduit means; (h) valve means associated with said first conduit means for controlling the flow of gas between said adsorption vessel and said void space gas storage vessel; (i) valve means associated with said second conduit means for selectively providing communication between said source of feed gas and said inlet end of said pump means or between said inlet end of said adsorption vessel and said inlet end of said pump means; and (j) valve means associated with said third conduit means for selectively providing communication between said outlet end of said pump means and said inlet end of said adsorption vessel or between said inlet end of said pump means and said strongly adsorbed component discharge conduit means; and (k) valve means associated with said fourth conduit means for controlling the flow of gas between the nonadsorbed gas outlet end of said adsorption vessel and said nonadsorbed gas discharge conduit means.

Claim 24

The apparatus of claim 21, wherein the outlet end of said pump means is joined to said gas storage vessel by means of a conduit which contains a valve.

Claim 25

The apparatus of claim 21, wherein said third conduit means includes a feed gas buffer vessel.