1. What are some advantages of a wiped film still (WFS)?
A WFS is a high-efficiency molecular short path distillation system utilizing high vacuum, dynamic wall wiping, brief heating and a condensing surface a short distance from the evaporation surface. This, plus the continuous mode operation of the WFS cuts the heating residence time to seconds, versus hours. That’s important, because the longer the material boils, the more it will degrade—resulting in lower purity, yield, clarity and ultimately, profit. WFS will perform the same in larger size and throughput versions, as it will enlarge proportionally, leaving ample room for proper evaporation. “Short path” units, because they are spherical in make-up, do not have this scalability advantage. In fact, when they are made larger, the ratio of volume to available evaporation area (boundary where liquid interfaces with vapor) declines substantially, and relative throughput decreases.
2. Will wiped film molecular distillation work well after different types of extraction and other process steps?
Yes. You can count on improved purity and clarity whether hydrocarbon, ethanol, supercritical or other extraction methods were utilized. Winterizing (removing wax) is not required, but without it, you’ll need to clean and maintain the still more often. The still will also work well whether or not decarboxylation has been performed.
3. Should a wiped film still be procured large enough for estimated production rates a year or two down the road?
No, there are operational problems that arise when the equipment is much larger than needed for the near term. Start with a still matching actual production rate needs for the first six months, then revisit multiple unit needs later after operation has been running steadily. And because the WFS is scalable, when much greater quantities of material need to be processed, larger versions of equipment can be successfully utilized.
4. What is the most common problem typically encountered in operating wiped film stills?
By far, the most frequent issues we see have to do with insufficient prior removal of light components such as ethanol, water, lighter terpenes, gases, etc. These should have been decreased to lower values earlier via more aggressive rotovaping, decarboxylating and feed flask degassing. This allows greater vacuum, less flashing, better color, throughput, purity and yield. An early indication of a problem is when the first pass is running at more than a few torr and/or more than 1 percent of feed collecting in the cold trap.
5. What things are helpful to improve wiped film still operation results?
Proper maintenance of vacuum pumps and leak checking is more important than massive capacity rotary vane and booster pumps. If better than 0.02-torr in a clean, dry still is not obtainable, check for leaks and pump health and learn how to use your gas ballast valve! Know the inter-relationship of feed rate, vacuum level and temperature. Strategize your operation based on extract composition and product goals, and tweak parameters to optimize each run. Adapt for variations in starting material.