Reclaiming Terpenes Lost in a Vacuum
By: Clancy Callaghan, Mechanical Engineer
This paper considers two methods used to condense terpenes and other Volatile Organic Compounds (VOC’s) from vapor to liquid in an effort to reclaim or “trap” them.
Condensing terpene vapors to liquid can be achieved by removing heat from the terpene molecules until they change phase from vapor to liquid (i.e. reach their Dew Point). To remove heat from the molecules it is necessary to transfer the heat to another material. This task becomes more challenging when under vacuum pressures--which requires colder temperatures than it would at atmospheric pressures.
There are three modes of heat transfer to consider: convection, conduction, and radiation.
Convection is not an option when operating at vacuum pressures since there are so few molecules, there is no opportunity for organized flow to facilitate convection.
Most cold traps and cold fingers have large cylindrical shapes that rely on radiation as the principle mode of heat transfer. The idea of the large cylindrical vessel is that the vapor will spend more time in the larger volume and lose enough heat during this time, via radiation, to condense. Because the vessels are typically large and smooth geometric shapes the molecules rarely engage any surface and therefore conduction plays a minimal role in heat transfer.
The CF-1000 relies on conduction as the principle mode of heat transfer, and radiation as secondary.
Because the unit’s condenser is made from a high grade alloy, which is 145 times more thermally conductive than glass, its surface reaches its low condensing temperature much faster than glass. It can retain a more uniform temperature, and can quickly and continuously remove heat.
Each time a molecule makes contact with a surface, some of its energy/heat is directly absorbed to the surrounding surface via conduction.
The CF-1000’s condenser also has a dynamic flow design that "confuses" the vapor particles forcing the molecules to make contact with the sub-zero surfaces until they lose enough energy to condense.
In addition to removing heat from the terpenes via conduction, the CF-1000 also removes heat from the molecules by absorbing the emission of electromagnetic waves (i.e. thermal radiation).
To take harvesting terpenes a step further, the CF-1000’s condenser surface is coated with a thin Teflon film that offers two distinct advantages over glass cold traps; it's hydrophobic & chemical properties.
The hydrophobic or “non-stick” properties of Teflon assist the accumulated liquid terpenes to flow down to the terpene collection chamber at the bottom of the unit.
An additional obstacle to consider is the chemical compatibility of materials used in contact with the VOC’s. The substances being collected are highly sought after, valuable, and frequently used for medical purposes. When trapping terpenes, it is crucial that we preserve their natural unadulterated properties.
The specialized hydrophobic coating we use is more chemically inert than glass--ensuring the purity of your condensates, and it is the clean-coating of choice across-the-board for medical equipment.
NOTE: This is due mainly to the manufacturing restrictions involved with using glass as the condensing surface. Glass is classified as an insulator and internal surfaces rarely attain advertised temperatures.