Short path distillation (molecular distillation) is a special type of thin film distillation technology, at which even lower working pressures and therefore even lower boiling temperatures can be realized.

Different from the traditional wiped film evaporator design, the condenser is located inside the short path evaporator body. There is no vapour line between evaporator and condenser. The considerably lower pressure in the short path evaporator is obtained by the short distance for the vapours on their way from the evaporator surface to the condenser. In addition, the cross section area of flow is equal to the evaporator surface, so that there is only a minor pressure drop between evaporator and condenser. The special design of short path evaporators allows operating pressures, also on industrial scale distillation systems, down to 0.001 mbar. The very low operating pressures ensure very low distillation temperatures and therefore a very gentle distillation is possible. The short path distillation allows the thermal separation of high molecular and high-boiling products at high yields and good product quality.
If the distance between evaporator and condenser is in the order of the average free path length of the molecules, this process is also called "molecular distillation".

Thanks to the short residence time, the low evaporation temperature and the immediate cooling of the concentrate, thermal stress and decomposition of the product can be minimized.  
 
Advantages of short path distillation

• Continuous distillation process
• Very low operating pressures (up to 0.001 mbar)
• Short residence time
• High evaporation rates
• Low fouling on evaporator wall
• Compact design

Applications for short path evaporators

Short path evaporators manufactured by VTA

VTA provides short path evaporators from laboratory to production scale in sizes ranging from 0.04 - to 80 m² and for operating temperatures up to 400 °C. Different wiper systems are selected depending on the product properties.

The material for the product wetted evaporator parts will be selected depending on the corrosiveness and the reactivity of the processed products.

Product development in the VTA test centre

In the test centre VTA is able to perform feasibility and pilot tests with different sizes of short path evaporators. Production runs are also possible on the laboratory and pilot equipment.

Toll distillation at VTA site

In addition to the laboratory and pilot testing, VTA can perform toll distillation also on industrial scale short path distillation equipment.