SEPARATION OF A MIXTURE OF C4-HYDROCARBONS BY EXTRACTIVE DISTILLATION

摘要

A process for separating, by means of a selective solvent, a mixture of C4-hydrocarbons which contains some hydrocarbons which are more soluble in the selective solvent and some which are less soluble therein and recovering the selective solvent in a solvent recovery zone, which process comprises: separating the hydrocarbon mixture, in an extractive distillation zone, into a top product which contains the less soluble hydrocarbons and an extract which contains the more soluble hydrocarbons and the selective solvent, bringing the extract taken off the extractive distillation zone to a higher pressure than the pressure in the extractive distillation zone, heating the extract which is under this higher pressure in a heat exchange zone, by indirect heat exchange with the selective solvent obtained as the bottom product from the solvent recovery zone, subjecting the heated extract to a flash evaporation and letting down the heated extract, in the flash evaporation, to a pressure which is at least equal to the pressure in the extractive distillation zone and is higher than the pressure in the solvent recovery zone, recycling the vapor component of the extract obtained from the flash evaporation to the extractive distillation zone whilst the liquid phase remaining after the flash evaporation is fed to the solvent recovery zone, separating the liquid phase obtained from the flash evaporation in the solvent recovery zone into a product containing the hydrocarbons and, as the bottom product, the selective solvent which has been freed from the hydrocarbons, recycling the resulting selective solvent via the heat exchange zone to the extractive distillation zone, and recycling the product which is obtained from the solvent recovery zone and contains the hydrocarbons partially or, where appropriate,completely to the extractive distillation zone, after increasing the pressure in a compression zone.