Cryogenic/Membrane Separations with Interstage Compression Recycle of the Permeate
Publication Date: 2009-Dec-31
The IP.com Prior Art Database
Compression Recycle of the Permeate
Cryogenic carbon dioxide separation plants typically involve gas/liquid flash separators followed by cryogenic distillation.
Vapor for the separators is vented; vapor from the distillation tower is recycled back to the flash separators. To raise recovery, higher feed pressures are required.
Prior work with membranes suggests that the vapor stream from the separators be recycled with a membrane or that the vent stream from the distillation column be recycled with a membrane. This raises recovery at constant column pressure, and is lower in energy cost than raising column pressure.
Recycling both streams to the same point using separate membrane operations is more energy efficient than recycling either stage by itself at high recoveries.
Incondensable vapor from the flash separators can be recycled using membranes with the permeate of the membrane unit, consisting primarily of carbon dioxide, being recompressed and fed back to the cryogenic separator, or in the case of oxy coal power production, being recycled to the boiler for oxygen value. This decouples the recovery/purity curve of a cryogenic system.
Permeate from the recovery of the incondensable vapor is recycled at sufficiently high pressure to be fed back into the feed compressor in an interstages of the cryogenic feed compressor. Maintaining the permeate pre...