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Volume 3, Issue 7
How do falling films work and what are potential solutions to improve them?
Falling films are usually only a partial solvent recovery tool. They often carry hidden costs and time loss because they are designed to recover just 70–80% of the solvents from a tincture of full spectrum oil suspended in a solvent. This requires manufacturers to purchase additional rotary evaporators that significantly slow the solvent recovery process. An alternative option for extractors to evaluate are all-in-one industrial solvent recovery and decarboxylation systems.
If you have been around the hemp or cannabis sectors, you have likely heard of falling films. They are widely considered to be one of the fastest solvent recovery systems on the market.
While they are a useful addition to the cannabis space, it is important to note that most falling films are not a one-stop-shop for solvent recovery. The vast majority can only evaporate 70–80% of solvents from a tincture, meaning extractors need to expend more capital on inefficient rotary evaporators that entirely erase the speed gain of a falling film.
Solvent recovery is one of the major bottlenecks in hemp and cannabis extraction processes. Whether manufacturers are using ethanol, CO2, or hydrocarbons to extract, they often use solvents such as ethanol in the initial extraction, the winterization or dewaxing, or the chromatography remediation phases. Falling films are distillation machines that use evaporation and condensation to “recover”
solvents and isolate desired products such as full
Falling films operate on a basic principle: It is easier to evaporate a thin film of water than a large pool. Most falling films are large columns that contain multiple vertical heated tubes. Each tube channels a thin falling film of solution. In this way, solvents such as ethanol can be quickly vaporized while the remaining solution trickles down to be captured at the bottom of the machine.
Falling films work best with dilute solutions that are mostly ethanol. Once the majority (70–80%) of the solvents have been recovered, a tincture of full-spectrum oil and ethanol becomes viscous and does not move in a uniform film. At that stage, the small tubes within a falling film can become obstructed while the high temperatures burn the oil.
This kind of obstruction has to be avoided at all costs. Falling films are notoriously difficult and costly to repair once the interior system has been compromised. For this reason, most falling films (except those that are hundreds of thousands of dollars) are only designed to reclaim 70–80% of solvents. They require extractors to make an additional purchase of a 20 L or 50 L rotary evaporator to “polish” off the residual ethanol.
Depending on the company you choose, that additional rotary evaporator will easily add $50,000 to $80,000 to your price tag (not including additional shipping, certification, and training costs). In addition, the high operating temperatures that falling films use tend to spoil terpenes, flavonoids, and full-spectrum oil.
Let’s look at some numbers to understand the actual time loss involved.
If you are working with 100 gallons of tincture that is 90% ethanol and 10% cannabidiol (CBD) oil, you can expect a 25 gph falling film to recover 67.5 gallons of ethanol in 2.5 h. However, at that point you would be left with 22.5 gallons of concentrated tincture that needs to be loaded into a 50 L rotary evaporator.
A 50 L rotary evaporator can reach 4 gph for very dilute tincture solutions, but if you are working with concentrated tincture, you can expect to get half that rate, 2 gph. Your rate to evaporate 22.5 gallons would be at least 11 h of continuous operation, not including the time to load and empty the system.
The total run time for that 25 gph falling film and 50 L rotary evaporator was 13.5 h to evaporate 90 gallons of ethanol. In other words, it’s really more of a 6.5 gph falling film.
That’s not fast, especially considering the price you paid for two different systems and the work to load and empty the rotary evaporator every 2 h.
In conclusion, falling films are not fast solutions if they need to be paired with a rotary evaporator. They carry high hidden costs and labor expenditures.
This is a problem my company has been working hard to innovate. Our industrial systems are designed to replace all this equipment. Working with the same 100 gallons of tincture as above, our system (X9 200 liter EcoChyll) could evaporate all 90 gallons of ethanol in 6 h. That is more than double the speed of the 25 gph falling film and 50 L rotary evaporator.
In addition, our 200 L system could decarboxylate all 10 gallons of CBD oil immediately. It would take 2 h to decarboxylate. Normally, decarboxylation reactors that can handle 10 gallons of oil cost more than $60,000 and take 6 h to run.
All told, you could spend hundreds of thousands of dollars for a 25 gph falling film, a 50 L rotovap, and a 100 L decarboxylation reactor to process 100 gallons of tincture in 20 h (not including labor to load and empty systems). Or you could spend far less to buy one of our systems and do it all in 8 h. We are pretty proud of those numbers.
NICK SHREWSBURY is a Technical Sales Representative at
Ecodyst LLC in Boxford, Massachusetts. Direct correspondence to: firstname.lastname@example.org
N. Shrewsbury, Cannabis Science and Technology 3(7), 57-58 (2020).