Cryogenic gas processing
First Claim
1. A method for separating ethane and higher molecular weight hydrocarbons from a natural gas feed, predominating in methane and containing significant amounts of ethane and higher molecular weight hydrocarbons and carbon dioxide, having a first pressure substantially above atmospheric pressure and a first temperature substantially below atmospheric temperature and at which first pressure and first temperature said feed comprises both vapor and liquid phases, comprising:
- (a) separating said feed, in a separation zone, to separate the vapor phase of said feed, as a first vapor phase, and the liquid phase of said feed, as a first liquid phase;
(b) expanding at least a part of said first vapor phase to reduce the pressure thereof to a second lower pressure and reduce the temperature thereof to a second lower temperature and produce a first expanded fluid stream;
(c) fractionally distilling said first expanded fluid stream, any unexpanded remaining portion of said first vapor phase and said first liquid phase, in a fractionation zone, to produce a second vapor phase, significantly enriched in methane and carbon dioxide, and a second liquid phase, predominating in ethane and higher molecular weight hydrocarbons and containing insignificant amounts of methane;
(d) expanding at least a portion of said second vapor phase to reduce the pressure thereof to a third lower pressure and reduce the temperature thereof to a third lower temperature and produce a second expanded fluid stream, as a third vapor phase, predominating in methane, significantly enriched in carbon dioxide and containing insignificant amounts of ethane in higher molecular weight hydrocarbons, and a third liquid phase;
(e) separating said second expanded fluid stream, in a separation zone, to separate said third vapor phase and said third liquid phase;
(f) recycling said third liquid phase to said fractionation zone, as a reflux;
(g) recovering said third vapor phase as a product; and
(h) recovering said second liquid phase as a product;
(i) maintaining the temperature and pressure at all times throughout the process substantially within the liquid range of carbon dioxide.
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Accused Products
Abstract
Higher boiling constituents are separated from a normally gaseous feed mixture, predominating in lower boiling constituents and containing significant amounts of such higher boiling constituents, such as natural gas by fractionally distilling a feed mixture having a temperature substantially below atmospheric temperature at a pressure substantially above atmospheric pressure at which temperature and pressure the feed mixture comprises both vapor and liquid phases to produce a first vapor phase substantially enriched in lower boiling constituents and a first liquid phase substantially enriched in higher boiling constituents, expanding at least a part of the first vapor phase to reduce the pressure and temperature and produce an expanded fluid stream comprising a second vapor phase and a second liquid phase, separating the second vapor phase from the second liquid phase, recycling the second liquid phase to the fractional distillation step as a reflux, recovering the second vapor phase as a product and recovering the first liquid phase as a product. In another embodiment, at least a part of the feed mixture is expanded prior to fractional distillation. In other embodiments, the feed mixture is separated into a vapor phase and a liquid phase and at least a part of the vapor phase is expanded and/or the feed mixture is first cooled by indirect heat exchange with the second vapor phase prior to recovery of the latter as a product.
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Citations
25 Claims
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1. A method for separating ethane and higher molecular weight hydrocarbons from a natural gas feed, predominating in methane and containing significant amounts of ethane and higher molecular weight hydrocarbons and carbon dioxide, having a first pressure substantially above atmospheric pressure and a first temperature substantially below atmospheric temperature and at which first pressure and first temperature said feed comprises both vapor and liquid phases, comprising:
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(a) separating said feed, in a separation zone, to separate the vapor phase of said feed, as a first vapor phase, and the liquid phase of said feed, as a first liquid phase; (b) expanding at least a part of said first vapor phase to reduce the pressure thereof to a second lower pressure and reduce the temperature thereof to a second lower temperature and produce a first expanded fluid stream; (c) fractionally distilling said first expanded fluid stream, any unexpanded remaining portion of said first vapor phase and said first liquid phase, in a fractionation zone, to produce a second vapor phase, significantly enriched in methane and carbon dioxide, and a second liquid phase, predominating in ethane and higher molecular weight hydrocarbons and containing insignificant amounts of methane; (d) expanding at least a portion of said second vapor phase to reduce the pressure thereof to a third lower pressure and reduce the temperature thereof to a third lower temperature and produce a second expanded fluid stream, as a third vapor phase, predominating in methane, significantly enriched in carbon dioxide and containing insignificant amounts of ethane in higher molecular weight hydrocarbons, and a third liquid phase; (e) separating said second expanded fluid stream, in a separation zone, to separate said third vapor phase and said third liquid phase; (f) recycling said third liquid phase to said fractionation zone, as a reflux; (g) recovering said third vapor phase as a product; and (h) recovering said second liquid phase as a product; (i) maintaining the temperature and pressure at all times throughout the process substantially within the liquid range of carbon dioxide. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method for separating ethane and higher molecular weight hydrocarbons from a natural gas feed, predominating in methane and containing significant amounts of ethane and higher molecular weight hydrocarbons and carbon dioxide, having a first pressure substantially above atmospheric pressure and a first temperature near atmospheric temperature, comprising:
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(a) cooling said feed to reduce the temperature thereof to a second lower temperature substantially below atmospheric temperature and at which first pressure and second temperature said feed comprises both vapor and liquid phases; (b) separating the thus cooled feed, in a separation zone, to separate the vapor phase of said feed, as a first vapor phase, and the liquid phase of said feed, as a first liquid phase; (c) expanding at least a portion of said first vapor phase to reduce the pressure thereof to a second lower pressure and reduce the temperature thereof to a third lower temperature and produce a first expanded fluid stream; (d) fractionally distilling said first expanded fluid stream, any unexpanded remaining portion of said first vapor phase and said first liquid phase, in a fractionation zone, to produce a second vapor phase, significantly enriched in methane and carbon dioxide, and a second liquid phase, predominating in ethane and higher molecular weight hydrocarbons and containing insignificant amounts of methane; (e) expanding at least a portion of said second vapor phase to reduce the pressure thereof to a third lower pressure and reduce the temperature thereof to a fourth lower temperature and produce a second expanded fluid stream, as a third vapor phase, predominating in methane, significantly enriched in carbon dioxide and containing insignificant amounts of ethane and higher molecular weight hydrocarbons, and a third liquid phase; (f) separating said second expanded fluid stream, in a separation zone, to separate said third vapor phase and said third liquid phase; (g) recycling said third vapor phase to said fractionation zone, as a reflux; (h) recovering said third vapor phase as a product; and (i) recovering said second liquid phase as a product; (j) maintaining the temperature and pressure at all times throughout the process substantially within the liquid range of carbon dioxide. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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Specification