If the supply contains suspended matter or dissolved salts, then membrane pollution may be encountered. Thanks to considerable energy saving, the investment is still economically viable for complex distillations.įurther, pervaporation avoids contamination of the required flow, in contrast to, for example, azeotropic distillation where entrainers or extra components are used to eradicate the azeotrope. need for vacuum) are currently relatively expensive. However, the membranes and membrane installations, (incl. Savings of above 50% are easy to realise. The main advantage of pervaporation is the major potential to save energy. Membranes for separating 2 organic components are still in the development phase. They are also suitable for removing volatile components like hydrocarbons from air. Good hydrophobic commercial membranes are also available on the market for removing volatile organic components from wastewater. Recently, the technique was also used to drain bio-ethanol. The use of pervaporation to drain solvents is clearly on the increase. Good hydrophilic pervaporation membranes are available on the market. Further, it offers an energy advantage because only the permeating component must be converted in the gas phase. This it is an interesting alternative for separating azeotropic mixes or mixes with similar boiling points. Pervaporation is not based on a liquid-vapour balance like distillation, but is based on differences in sorption and diffusion in the various components in the supply.

This alternative is particularly interesting if the supply comes from an earlier process step in vapour form. Vapour permeation involves the supply being introduced in vapour form before it comes into contact with the membrane. There is also an alternative process, referred to as vapour permeation. Desorption in the gas phase on the permeate-side.

Selective diffusion through the membrane.Selective sorption in the membrane on the influent-side.The pervaporation process contains 3 steps: In most cases, the permeate is re-condensed. This low vapour pressure is normally achieved by placing a (slight) vacuum on the permeate-side of the membrane. Specifically for this process, the permeating component is converted into an evaporation phase, due to the low (partial) vapour pressure on the permeate-side. The used membrane is a dense non-porous membrane or a very finely-porous ceramic membrane that displays an affinity towards the component one wants to remove. Pervaporation is used to separate liquid mixes. Pervaporation is a membrane process comparable to distillation, and combines permeation and vaporisation.

Two tank approach pervaporation