While under vacuum, the crude oil is added to the top of a heated vertical cylinder on a rotating plate. Specially designed wipers wipe the oil, thus creating and renewing the thin film. This thin film enables an efficient heat transfer, even for highly viscous fluids.
Short path distillation produces a high-quality product. You can get multiple fractions during the distillation process, depending on how high you raise the temperature. The multi-position flask collects the different fractions into different flasks, which allows for easy distillation.
As the oil enters the cylinder, it encounters the rotating, specially designed wipers or rollers that create and renew a thin film on the heated surface. A long, condenser in the middle of the wipers in the evaporator body, cooled with recirculating fluid, condenses the vapor. Receiving vessels collect the distillate and the high temperature residue at the bottom. A recirculating heater provides temperature control of the feed container and outer jacketed wiped film evaporator body. Refrigerated circulators cool the condenser and cold trap. Optimizing the feed rate, vacuum, and temperatures is essential to yield the desired component composition in the distillate.
So what are the differences and similarities between short path and wiped film distillation? Let’s dive in.
Crude oil is heated in a boiling flask with a magnetic stirrer. The condensing head is jacketed and requires a recirculating chiller to cool the condensing head to condense the cannabinoid vapor back into a liquid form.
Both options use vapor pressure (vacuum depth) to reach the lowest possible boiling points for our compounds to avoid degrading what we’re trying to capture—so either way, you’ll end up with a high-quality end product.
The compounds are then separated through slow thermal heating with precise and controlled temperatures. As you slowly raise the boiling flask temperature, you will get multiple fractions of the distillation—the higher you go, the different compounds you will be distilling, starting with highly volatile terpenes or solvent leftover at lower temperatures. Raising the temperature will create a new compound/fraction, and the multi-position receiving flask can be adjusted to collect the different fractions into different receiving flasks.
Cons of Short Path Distillation
Short path distillation utilizes an apparatus with a multi-position receiver and condensing head. This process is very limited in scale and production, but can produce high-quality distillate with an experienced operator.
A short path will typically have 3 fractions—heads (terpenes and high volatiles), main body (THC/CBD), and tails (high boiling point cannabinoids).
Feed material is delivered from a feed flask into a cylindrical evaporation section, having heating, on the outside, (either electric resistance or circulating hot fluid jacket type), and a diagonally slotted wiper mechanism forcing liquid around and downward in a thin film on the inside. In the center of the body is a closely positioned internal condenser, providing a short path for vapor molecules traveling from the heated surface to the condenser surface. For cannabinoids, the internal condenser fluid must be kept elevated (
Pope Wiped-Film Molecular Stills (WFMS) are a special type of short-path, molecular distillation equipment. These are continuous mode systems, as opposed to batch vessel distillation apparatus. The diagram below of the cannabinoid purification distillation process illustrates the means of this technology and shows the flow of the feed material and the separation of component fractions within the equipment. The same purification distillation process can be used for multiple cannabinoid compounds including CBD purification and THC purification.
70°C) to prevent high viscosity or freeze up of THC, CBD and related components. During the journey downward, lighter (lower boiling point) fractions of the liquid begin to vaporize, move to the internal condenser and condense, falling down as a liquid into a well that captures and separates the distilled liquid (cannabinoid) which flows into a receiver flask. Heavier residue material (Chlorophyll, salts, sugars, heavy wax fractions) does not evaporate and instead travels the length of the still body and flows into a different receiver flask. Because of the optimized Pope design, this all happens within a number of seconds, and under vacuum-lowered temperatures, thus minimizing any possibility of product degradation.