How Does a Wiped Film Evaporator Work
- Feed—The feed supply is composed of the prepared and purified crude oil to be distilled within the evaporator. Most machines have a pumping mechanism between the feed supply and the still body to provide a consistent flow rate.
- Still—This is the main body of a thin/wiped film evaporator where distillation occurs. The “still” body is one of the system’s most complex sections, including a motorized wiper mechanism, a feed connection, an inner or external condenser, and two discharge/vessels for distillate and residue. The still also has an outer jacket that is heated or cooled to create conditions for distillation.
- Distillate & Residue—Wiped film produces these two end products. The distillate is the targeted, purified compound that was selectively collected at boiling point, while the residue is any feed constituent that did not evaporate during distillation. It is considered a waste product or saved for another material application.
- Vacuum system & cold trap—The vacuum system allows distillation to occur at a lower temperature. It comprises one or more vacuum pumps and a secondary cold trap after the still. The cold trap traps any light vapor that doesn’t condense in the internal or external condenser, helping increase vacuum longevity.
The first step in wiped film distillation involves introducing the feed liquid into the wiped film evaporator. This feed liquid could be a mixture that needs separation or purification, such as essential oils or pharmaceutical compounds. Once inside the evaporator, a rotating heated wiper blade spreads the liquid into a thin, even layer across the surface.
- Vaporization: When the thin layer of feed liquid touches the evaporator’s heated surface, it quickly vaporizes due to the efficient heat transfer. This rapid vaporization results in faster processing compared to traditional methods like simple batch distillation.
- Separation: As the liquid vaporizes, the different components in the mixture separate based on their boiling points. Substances with lower boiling points vaporize faster than those with higher boiling points. This allows for precise control over which substances are collected at different stages of the wiped film evaporation process.
- Condensation: Once the components have been separated through selective vaporization, the vapors move toward an external condenser. Here, they cool down and condense into liquid form, now separated based on their unique boiling points.
- Collection: The condensed liquids, now separated into distinct components, are collected in a separate container. Meanwhile, the leftover residue, or “waste,” remains on the evaporator surface. This waste can either be disposed of or further processed if needed.
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