Pervaporation

Basic idea of pervaporation.

1. PRESENTATION ON PERVAPORATION Presented by:- KANCHI AKSHITH MT17MCL007 M.Tech 1 st Yr. Dept. of Chemical Engineering VNIT

2. INDEX HOW IT IS DONE? DESIGN MEMBRANES USED MATHEMATICAL FORMULAE TYPICAL APPLICATIONS POSTER REFERENCES

3. HOW IT IS DONE?? Separation of liquid mixtures by partial vaporization through a membrane ( nonporous) is the separation principle in pervaporation. The driving force for pervaporation process is the difference in chemical potential, corresponding to the concentration gradient between phases on the opposite sides of the interfacial barrier . The separation feature is based on affinity with membrane materials and hence the molecule having higher affinity is adsorbed and diffuses through the membrane while the membrane retains molecules having low affinity.

4. PROCESS DIAGRAM

5. DESIGN A composite membrane is used that is selective for species A, but with some finite permeability for species B. The dense, thin-film side of the membrane is in contact with the liquid side. The retentate is enriched in species B. Generally, a sweep fluid is not used on the other side of the membrane, but a pressure P2, which may be a vacuum, is held at or below the dew point of the permeate, making it vapour . Vaporization may occur near the downstream face such that the membrane operates with two zones, a liquid-phase zone and a vapour-phase zone, as shown in Figure. Alternatively, the vapour phase may exist only on the permeate side of the membrane . The vapour permeate is enriched in species A . Commercial membrane modules for PV are almost exclusively of the plate-and-frame type because of the ease of using gasketing materials that are resistant to organic solvents and the ease of providing heat exchange for vaporization and high-temperature operation. Hollow- fiber modules are used for removal of VOCs from wastewater. Because feeds are generally clean and operation is at low pressure, membrane fouling and damage is minimal, resulting in a useful membrane life of 2–4 years

6. DESIGN

7. MEMBRANES USED Hydrophilic  membranes are used for dehydration of alcohols containing small amounts of water and  hydrophobic  membranes are used for removal/recovery of trace amounts of organics from  aqueous  solutions. Presently there have been a number of investigators concerning R&D of the hydrophilic membrane, which can be cataloged into organic, inorganic, and organic-inorganic hybrid membranes. Organic-inorganic hybrid membranes showed improved performance of pervaporative dehydration of solution, with better flux and retention. Commercially available hydrophilic membranes are made of polymeric membrane materials such as polyvinyl alcohol (PVA), polyimides, polymaleimides , Nafion , and polyacrylonitrile (PAN). One of the most applied polymeric materials for organic separation is polydimethylsiloxane (PDMS). PDMS exhibits high selectivity and permeability towards organic substances because of the flexible structure.

8. MATHEMATICAL FORMULAE

9. TYPICAL APPLICATIONS Solvent Dehydration: dehydrating the ethanol/water and isopropanol/water azeotropes. Continuous ethanol removal from yeast fermenters. Continuous water removal from condensation reactions such as  esterification  to enhance conversion and rate of the reaction. Removing organic solvents from industrial waste waters. Combination of distillation and pervaporation/vapour permeation. Concentration of hydrophobic flavour compounds in aqueous solutions (using hydrophobic membranes ). Reduction of the  aromatics  content in refinery streams. Breaking of  azeotropes. Purification of extraction media.

10. POSTER

11. REFERENCES [1] en.wikipedia.org/wiki/ Pervaporation [2] Wenqi Li, Patricia Luis ; Understanding coupling effects in pervaporation of multi-component mixtures [3] Separation of barriers & solid agents ; Seader , Henley , Roper; Separation Process Principles (3rd edition ); pp 535-538

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