| 摘要 |
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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