Plant Design
——Distillation
The classical approach to distillation is to use distiller such as forced circulation evaporator or plate evaporator. Boiling temperatures can be reduced by reducing pressure reduction .Not suitable for heat-sensitive materials.
——Falling Film Evaporation (FFE)
This plant design features a continuous process where the feed material is evaporated from a thin film flowing down a heated surface due to gravity. This can reduce the marginal thickness of the film and reduce the residence time.
——Thin film Evaporation (TFE)
An active agitation of the falling film with a wiper system even further reduces the film thickness thus allowing a further reduction of the pressure. It also promotes the heat transfer from the evaporator surface into the feed material and enables even shorter residence times.
——Shortpath Distillation (SPD)
Each of the above approaches assumes the condensation of the vapors in an external condenser. The transportation of the vapours from the evaporator to the condenser requires an appropriate pipeline with adequate geometry (length, diameter). This, however, necessarily results in an additional pressure drop (Law of Hagen-Poiseuille) thus putting a lower boundary to the achievable pressure range.
This constraint can be avoided if the condenser is placed within the evaporator. This is the key characteristic of shortpath distillation which may be considered one of the most effective vacuum distillation devices.