Thin film evaporation differentiates between plants for thin-film, short-path or molecular distillation. All systems are recommended for separation of volatile from less volatile components, for organic products, which are characterised by thermic instability, high molecular weight or high viscosity. The most important characteristics are pressures of 1 to 0,001 mbar as well as short retention times of the products in the heated evaporator zone to avoid overheating or damage of the product. The plants are made of glass or of glass-metal-combination according to the requirements of the products.
Thin-Film (Wiped Film) Distillation
Evaporator and condenser are separated components which are connected by nozzles. The vacuum pump is directly connected to the condenser. Using this type of equipment the ultimate pressure is limited to some mbars. The medium retention time of the liquid within the thin-film evaporator is depending on viscosity and throughput.
Short Path Distillation
This is a thin-film evaporation under reduced pressure down to 0,001 mbar. In this type of distillation system the condenser is integrated in the centre of the evaporator. The distance between evaporation surface and condenser is extremely short and pressure losses are eliminated.
Film evaporation at reduced pressures of 0,001 mbar is also called “molecular distillation”.
The PILODIST short path distillation system is a bench scale system and designed for distillation of thermally sensitive products under vacuum. As a result all obtained values and datas of this pilot operation can be used also for larger systems. The system is used for organic products of thermic instability, high molecular weight and/or high viscosity of up to 45000 cP at operating temperatures and depending on the type of rotating wiper elements.
The evaporation surface consists of a vertical glass cylinder, double mantled and filled with a heating medium which is tempered by a thermostat. The product is being spread to a thin film on the inner surface of the evaporator by means of rotating wiper elements, available in glass and PTFE. These wipers are being pressed to the inner wall of the surface by centrifugal forces where they produce a thin film with a continuous distribution of the liquid film. The condenser is vertically arranged in the center of the glass evaporator, cooled by means of a cooling thermostat.
For the optimization of the evaporation process the type of wipers as well as the speed of the rotation can be adjusted to the viscosity of the product to be evaporated. The system includes a controller for vacuum, temperature, power supply for vacuum pump, thermostat and speed of wiper motor.
The rotating wiper basket is made of aluminium, hard covered with PTFE slide coating. It is available in 3 different versions (to be selected) to accommodate 3 different types of wiper elements:
- Type a: PTFE wipers and glass wipers which can be used alternatively.
These wiper elements are being moved by centrifugal forces
- Type b: PTFE wipers with spiral gearing
- Type c: PTFE wipers as rolls
Fig. 1: Different wiper inserts
a) Wiper elements made of glass resp. of glass-fibre reinforced PTFE.
b) Wiper elements made of PTFE or graphite with spiral gearing
c) Wiper elements with rolls, made of PTFE
Fig. 2: Different wiper baskets to accommodate wiper inserts
The extremely gentle heating of the evaporator is achieved by a heated liquid (oil) from an external circulation thermostat
Of late years, the demand for test and pilot plants for gentle distillation has considerably increased in the chemical, pharmaceutical and petrochemical industry. The constantly rising number of new complicated products and the rising world market price for raw materials are responsible for this demand.
For delicate distillation of thermally sensitive products, we have developed efficient plants laboratory and test operation which are preferably used for the following applications:
- Oil- and fat industry for distillation of mono- and diglycerides, fatty acids and their derivates, fatty alcohols, tall oils, terpentines, waxes
- Chemical industry, ethereal oils and olfactory products, detergents, insecticides, fertilizers, peroxides, metal-organic compounds etc.
- Petrochemical industry, parafin´s, lubricating oils, tar containing products, crude oil residues up to AET 720 °C
- Synthetic fibres industry, softeners, elastomeres, polyesters, polymeres
- Pharmaceutical industry,antibiotics, ferments, hop-, tobacco-, maw seed- and similar plant extracts effective as drugs, vitamines, hormones
- Food industry,milk products, aroma concentrates, coffee-, tea-, cacao biocatalyst concentrates, proteins and protein substances, fruit-juice, sugar derivates etc.