Product Refinement

Falling Film Evaporators

Written by Asia Mayfield

Most cannabis extraction methods require a solvent like ethanol. To create the final product, technicians need a reliable, cost-effective way to separate the solvent from the biomass. One way to do this is to use falling film evaporation.


What is falling film evaporation?

Falling film evaporators have been used for years in industries as varied as agriculture and seawater desalination. These evaporators are now common in the cannabis space as well, largely because their use can increase an extract maker’s energy efficiency saving time and money. Falling film evaporators use the physics of evaporation and gravity combined with heat in a vacuum to separate the solvent from cannabinoids and terpenes.

First, the cannabis and solvent mixture is added to the pre-warmer, which is the evaporator’s first chamber. It brings the temperature of the mixture close to its boiling point. Next, the mixture is moved to the top of the evaporator, where it begins to slide down heated tubes with gravitational assistance. The alcohol, having a lower boiling point than the cannabinoid-rich extract, evaporates as the mixture moves through the tubes and is collected in a cold trap or condenser. Because of its higher boiling point, the cannabis oil continues to flow down into a collection container. It is important to ensure that the walls of the evaporator are well coated so that the oil evenly flows down the walls as a thin film. If the evaporation tube is not thoroughly and evenly wetted, thermal degradation can occur.

The process is done under a vacuum, reducing the temperature required to evaporate the alcohol. This low temperature and the short contact time between the heat and the product compounds of interest helps protect thermally labile ingredients such as delta-9-tetrahydrocannabinol (THC) and terpenes.

Solvent recovery can be greater with an increase in evaporator surface area. The more tubes the evaporator has, the greater the surface area. With decreases in tube diameter, surface area also increases, therefore, it has been suggested that one look for smaller tube diameters and multiple tubes when shopping for a falling film evaporator.

Falling film evaporation can be more cost-effective than other solvent removal methods because the condensed ethanol vapor can be recycled for further use. Additionally, the scale of how much solvent can be recovered over time is greater with falling film evaporators than a technique like rotary evaporation. In addition, the relatively low temperatures required could mean lower energy costs.


Image source: Flickr


About the author

Asia Mayfield

Asia Mayfield is a freelance writer who focuses on the cannabis industry. She can be reached at [email protected]