Distillation Technology Dehydration and Purification

GEA applies 3 methods to achieve concentrations above the azeotropic point.

Where product purities superior to feasible concentrations through rectification are required, one of these technologies come to operation: Molecular sieve technology, distillation with entrainer, and pervaporation through hydrophilic membranes.

GEA Molecular Sieve or Adsorption Technology represents a low energy  process for dehydration of e.g. ethanol.

The superheated alcohol/water mixture passes a zeolite bed , that holds back the small water molecules  while the bigger alcohol molecules pass the bed.

GEA supplies as standard three adsorption vessels which operate in continuous batch mode.  One unit works in adsorption mode while the second is regenerated. The third vessel allows smooth switching between the two modes in order to ensure a long life service for the zeolite. Another advantage of the  third vessel is a constant flow  of the dehydrated ethanol vapors towards the distillation train, leading to a constant energy input  on one of the reboilers,  where the vapor is condensed.

But also the  two-vessel-concept  has proven itself within a multistage distillation plant , however not achieving as constant conditions as the three-vessel-concept.

 

The GEA Distillation with Entrainer represents a second technology for achieving concentrations above the azeotropic point of mixtures – or for mixtures of two very similar behaving compounds.

An example is the azeotropic distillation of IPA/ water-mixtures.  Cyclohexan is added to the mixture and creates  with the water a new  azeotropic mixture. This new azeotrop can can be rectified and is discharged as head product.  The dehydrated IPA  is discharged from the column bottom. In the entrainer recovery process the water is separated from the cyclohexane. The second application of the entrainer technology is the extractive distillation – according to the compound mixtures  the adequate process and entrainer must be defined.

The core of the GEA Pervaporation techniques is the  hydrophilic membrane. A vacuum is created on one side of the membrane and the differing diffusion resistances through the membrane and the differing partial pressures are the basis for the separation.