Separation of low boiling constituents from a mixed gas
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 said ethane and higher molecular weight hydrocarbons and having a first pressure substantially above atmospheric pressure and a first temperature substantially below atmospheric temperature, at which first pressure and first temperature, said feed comprises both a vapor phase, representing a first vapor phase, and a liquid phase, representing a first liquid phase, comprising:
- (a) expanding at least a part of said vapor phase, in a first expansion step, to produce a first expanded fluid having a second pressure substantially lower than said first pressure and a second temperature substantially lower than said first temperature;
(b) introducing all of said first expanded fluid and any unexpanded first vapor phase into a separation-contacting zone adjacent the top thereof and introducing all of said first liquid phase into said separation-contacting zone at a lower intermediate point thereof, under conditions and in proportions such that the pressure at the top of said separation-contacting zone is substantially lower than the pressure at the bottom of said separation-contacting zone and the temperature at said top of said separation-contacting zone is substantially lower than the temperature at said bottom of said separation-contacting zone;
(c) separating said first expanded fluid, said unexpanded remaining portion of said first vapor phase and said first liquid phase, in said separation-contacting zone, to produce a second vapor phase and a second liquid phase;
(d) introducing said second vapor phase into a fractional distillation zone adjacent the top thereof and introducing said second liquid phase into said fractional distillation zone at an intermediate point thereof below the point of introduction of said second vapor phase;
(e) fractionally distilling said second vapor phase and said second liquid phase, in said frictional distillation zone, to produce a third vapor phase predominating in methane and containing insignificant amounts of ethane and higher molecular weight hydrocarbons and a third liquid phase predominating in ethane and higher molecular weight hydrocarbons and containing insignificant amounts of methane;
p1 (f) recovering said third vapor phase as a product; and
(g) recovering said third liquid phase as a product.
1 Assignment
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Accused Products
Abstract
Lower boiling constituents are separated from a normally gaseous feed mixture predominating in higher boiling constituents and containing significant amounts of such lower boiling constituents and 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 mixture includes both vapor and liquid phases, including introducing at least a portion of the vapor of the feed mixture representing a second vapor phase into a separation contacting zone adjacent the top thereof at a second pressure substantially lower than the first pressure and a second temperature substantially lower than the first temperature and introducing at least a portion of the liquid of the feed mixture representing a second liquid phase into the separation-contacting zone at a lower intermediate point at a third pressure and a third temperature approximately equal to the first pressure and the first temperature, respectively. The second pressure thus being substantially lower than the third pressure and the second temperature thus being substantially lower than the third temperature, separating the second vapor phase and the second liquid phase in the separation-contacting zone to produce a third vapor phase substantially enriched in the higher boiling constituents and a third liquid phase substantially enriched in the lower boiling constituents, introducing the third vapor phase into a fractional distillation zone adjacent the top thereof and introducing the third liquid phase into the fractional distillation zone at an upper intermediate point, fractionally distilling the third vapor phase and the third liquid phase to produce a fourth vapor phase substantially enriched in the higher boiling constituents and a fourth liquid phase substantially enriched in lower boiling constituents, recovering the fourth vapor phase as a product and recovering the fourth liquid phase as a product. In accordance with another aspect, at least a portion of the second vapor phase and/or at least a portion of the third vapor phase is expanded in a turbo expander.
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Citations
28 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 said ethane and higher molecular weight hydrocarbons and having a first pressure substantially above atmospheric pressure and a first temperature substantially below atmospheric temperature, at which first pressure and first temperature, said feed comprises both a vapor phase, representing a first vapor phase, and a liquid phase, representing a first liquid phase, comprising:
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(a) expanding at least a part of said vapor phase, in a first expansion step, to produce a first expanded fluid having a second pressure substantially lower than said first pressure and a second temperature substantially lower than said first temperature; (b) introducing all of said first expanded fluid and any unexpanded first vapor phase into a separation-contacting zone adjacent the top thereof and introducing all of said first liquid phase into said separation-contacting zone at a lower intermediate point thereof, under conditions and in proportions such that the pressure at the top of said separation-contacting zone is substantially lower than the pressure at the bottom of said separation-contacting zone and the temperature at said top of said separation-contacting zone is substantially lower than the temperature at said bottom of said separation-contacting zone; (c) separating said first expanded fluid, said unexpanded remaining portion of said first vapor phase and said first liquid phase, in said separation-contacting zone, to produce a second vapor phase and a second liquid phase; (d) introducing said second vapor phase into a fractional distillation zone adjacent the top thereof and introducing said second liquid phase into said fractional distillation zone at an intermediate point thereof below the point of introduction of said second vapor phase; (e) fractionally distilling said second vapor phase and said second liquid phase, in said frictional distillation zone, to produce a third vapor phase predominating in methane and containing insignificant amounts of ethane and higher molecular weight hydrocarbons and a third liquid phase predominating in ethane and higher molecular weight hydrocarbons and containing insignificant amounts of methane;
p1 (f) recovering said third vapor phase as a product; and(g) recovering said third liquid phase as a product. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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19. A method in accordance with claim 35 wherein the volume of the portion of the feed thus utilized to supply heat to the fractional distillation zone is controlled in accordance with the temperature at which the fifth vapor phase is returned to said fractional distillation zone.
Specification