MEMBRANE SEPARATION PROCESS

摘要

The invention is directed to a membrane separation process of an aqueous feed solution. In one aspect the membrane separation process of the invention comprises passing an aqueous feed comprising one or more dissolved compounds having an increasing water solubility with increasing temperature through a membrane module comprising a feed inlet and a liquid retentate outlet, wherein the temperature in the outlet is higher than the temperature in the inlet, and wherein a positive driving force for water vapour permeation is created by maintaining the water vapour pressure at the distillate side lower than at the retentate side by other means than by a temperature difference, such that one or more of said dissolved compounds at least partially crystallise in said retentate, and wherein the relative temperatures of the feed inlet and the liquid retentate outlet are set. In another aspect, the membrane separation process of the invention comprises: - subjecting an aqueous feed comprising one or more dissolved compounds to a membrane distillation process, and - thereafter, preferably directly thereafter, passing the retentate from the membrane distillation process through a membrane module comprising a feed inlet and a liquid retentate outlet, wherein the temperature in the outlet is equal to or higher than the temperature in the inlet, and wherein a positive driving force for water vapour permeation is created by maintaining the water vapour pressure at the distillate side lower than at the retentate side by other means than by a temperature difference, such that one or more of said dissolved compounds at least partially crystallise in said retentate, and wherein the relative temperatures of the feed inlet and the liquid retentate outlet are set.