Secrets of Wiped Film Distillation - Part 5

Secrets of Wiped Film Distillation - Part 5

No need for bleed or sweep

Traditional distillation approaches often include a nitrogen bleed to carry the vapors over to the condenser, especially when trying to dry a little bit of solvent out of an oil. This is often done in a short path setup or a rotovap. The idea is the vapors form just above the surface of the liquid and the bleed "sweeps" them away from the liquid.

However, in a wiped film still this is completely unnecessary, but many users of the equipment still utilize a bleed anyway. In fact, when I started at Pope, my dad was describing how he would use a nitrogen sweep. Without it, he didn't think the system would remove solvent down to ultra-low levels.

My dad was an R&D chemist for 42 years and his knowledge in chemistry far surpassed mine. However, in the area of wiped film distillation, he was not an expert. It is such a specialized piece of equipment that many of the best chemists in industry use it incorrectly.

The key advantage of a wiped film still system is the agitated, thin film. Essentially, the heat source is on the surface of the film, so there is no barrier to evaporation. Then, the internal condenser is directly next to the wall. The condenser acts like a magnet and quickly removes all vapors from the gas phase.

These two attributes of the still allow the wiped film system to remove solvents and even larger molecules down to 20 ppm or even less. A sweep is not necessary and can even be detrimental due to the loss of vacuum.

Please connect for more insights into wiped film distillation and reach out if you ever want to discuss if this technology is a good fit for your application.