Plant Design

Batch Distillation

The classical approach to distillation is batchwise (discontinuous) and uses uses a pot still (alembic). The potential to reduce pressure reduction in order to reduce boiling temperatures is limited, however, due to the necessity to overcome the hydrostatic pressure in the pot still. In addition, residence times may be fairly large which also promotes thermal degradation. Hence, batch distillation is not an adequate setup for gentle thermal separation. Corresponding devices are not offered by UIC.

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. The marginal thickness of the film allows a reduction of both the pressure range and the residence time.

Thinfilm 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.

Typical pressure ranges and residence times for the different plant types are compared in the adjacent diagram.