| 摘要 |
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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