Device and a process for separating methane from a gas mixture containing methane, carbon dioxide and hydrogen sulfide
AssigneeEvonik Operations GmbH
InventorFlorian Winkler
Life of this patent
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Abstract
In a device for separating methane from a gas mixture containing methane, carbon dioxide and hydrogen sulfide, comprising a gas compressor, two or three membrane separation stages downstream of the compressor and a hydrogen sulfide adsorber, comprising a bed of activated carbon having catalytic activity for oxidizing hydrogen sulfide with oxygen, arranged upstream of the membrane separation stages, oxygen content and relative humidity can be adjusted for optimum adsorption capacity of the hydrogen sulfide adsorber by recycling permeate from the second membrane separation stage, which receives the retentate of the first membrane separation stage, to a point upstream of the hydrogen sulfide adsorber.
Claims20
A device for separating methane from a gas mixture containing methane, carbon dioxide and hydrogen sulfide, comprising:
- a) a gas compressor;
- b) a feed line for feeding said gas mixture to said gas compressor;
- c) a first membrane separation stage downstream from said gas compressor, comprising a gas separation membrane having higher permeability for carbon dioxide than for methane, providing a first retentate and a first permeate;
- d) a second membrane separation stage, connected to said first membrane separation stage to receive the first retentate as feed, said second membrane separation stage comprising a gas separation membrane having higher permeability for carbon dioxide than for methane, providing a second retentate as a product gas enriched in methane and a second permeate;
- e) optionally a third membrane separation stage, connected to said first membrane separation stage to receive the first permeate as feed, said third membrane separation stage comprising a gas separation membrane having higher permeability for carbon dioxide than for methane, providing a third retentate and a third permeate;
- f) a recycle conduit connected to a recycle feed point on said feed line upstream from said gas compressor, wherein:
- i) said recycle conduit is connected to said second membrane separation stage to receive said second permeate;
- or,
- ii) if the optional third membrane separation stage is present, either:
- said recycle conduit is connected to said third membrane separation stage to receive said third retentate;
- or alternatively,
- said recycle conduit is connected to both said second membrane separation stage and said third membrane separation stage to receive said second permeate and said third retentate;
- and
- g) at least one hydrogen sulfide adsorber comprising a bed of activated carbon having catalytic activity for oxidizing hydrogen sulfide with oxygen, said hydrogen sulfide adsorber being arranged between said recycle feed point and said first membrane separation stage.
Dependencies are inferred from the claim text.