Membrane-aided distillation for carbon dioxide and hydrocarbon separation
AssigneeAir Products and Chemicals, Inc.
InventorGene A. Lucadamo
Life of this patent
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Abstract
A process is described for separating a carbonaceous off-gas in a low temperature distillative separation to produce a fuel gas stream, a carbon dioxide-sulfur stream and a heavy hydrocarbon stream wherein the carbon dioxide-sulfur stream is reduced in pressure to produce refrigeration to return a portion of the fuel gas stream as reflux to the distillation, and the fuel gas stream, now at relatively higher pressure than the carbon dioxide-sulfur stream, is passed over a semi-permeable membrane selective to carbon dioxide to separate carbon dioxide from the fuel gas to combine the permeate carbon dioxide with the carbon dioxide-sulfur stream.
Claims8
A process for the low temperature distillation separation of a carbonaceous off-gas into a heavy hydrocarbon stream, a high purity fuel gas product and a high purity carbon dioxide-sulfur stream product wherein the fuel gas product is enriched in fuel gas components and the carbon dioxide-sulfur stream product is enriched in carbon dioxide by further separation in a semi-permeable membrane, comprising providing a high purity fuel gas and a carbon dioxide-sulfur stream at high recoveries while minimizing capital investment and energy utilization by:
- (a) compressing and aftercooling an off-gas containing acid gases, light fuel gases and heavy hydrocarbons;
- (b) drying the off-gas to remove moisture and subcooling the off-gas against an external refrigeration source and by heat exchange with product streams;
- (c) initially separating the off-gas at low temperature in a distillation column to recover an initial fuel gas stream as an overhead fraction, a carbon dioxide-sulfur stream as a sidestream fraction and an heavy hydrocarbon-containing stream as a bottom fraction;
- (d) expanding the carbon dioxide-sulfur stream and potentially the heavy hydrocarbon stream to a lower pressure to provide refrigeration to cool and partially liquefy the initial fuel gas stream by heat exchange;
- (e) phase separating the initial fuel gas stream into a crude fuel gas product and a carbon dioxide-rich liquid stream which is recycled to the distillation column as reflux;
- and
- (f) upgrading the purity of the crude fuel gas product and the carbon dioxide-sulfur stream by passing the relatively higher pressure crude fuel gas stream over a semi-permeable membrane selective to carbon dioxide gas to separate a carbon dioxide permeate from the crude fuel gas stream and combining the carbon dioxide gas permeate with the lower pressure carbon dioxide-sulfur stream to provide a final high purity fuel gas product and a high purity carbon dioxide-sulfur stream product.
Dependencies are inferred from the claim text.