Secrets of Wiped Film Distillation - Part 6

Secrets of Wiped Film Distillation - Part 6

Carrier Fluids

Sometimes there are feed materials that are thick and challenging to pump. The way to handle those is to warm them up so that they thin out. Obtaining a viscosity curve vs temperature will help you understand if the material can be processed.

And often, that is good enough. Once the feed is flowing, the two streams coming out of the still also flow.

Other times, problems develop in the residue. Very often, the distillate is a thin component, and once removed from the feed, the residue becomes very thick. Viscosity tends to be additive (thin fluid plus thick fluid becomes medium thick fluid), so when a thin fluid is removed from a thick fluid, the remainder is very thick.

This problem is often offset by the temperature of the still. If you warmed your feed to 70°C to get it to flow, the still might be at 200°C, so the residue will flow out of the still.

Other times, even at temperature, the residue becomes too thick to flow. At this point, many operators conclude that wiped film distillation is not a good fit. But we aren't done just yet.

One solution is to add a small amount of a thin, large molecule as a carrier fluid. Triglycerides and polymers like PEG500 work great for this application. The carrier can thin out that residue and keep it dissolved and flowing out of the still. Carriers help in situations where the residue is so thick that it is backing up into the still because your gear pump can't keep up.

If you are running a still super slow because the residue won't pump well, or if there is a distillation you gave up on because of the residue, this could be a solution for you.

Reach out with any questions. I'd be happy to discuss.