CO2 changes states at different temps and pressures. This gives us the abilitility to control very specifically what kind of solvent we are using, as well as, overall yield. So it is possible to lower settings to achieve a softer solvent extraction, or higher settings to get a stronger solvent extraction. The extraction process with CO2 makes it possible to control separator settings, that drop-out the extracted oil from the CO2 gas solvent. This can effect carry-over amounts as well as quality of the final product. To limit loss of collection and fractionation of both terpenes, THC, and Cannabinoids, you need to lower the pressure of the CO2 and entrained oil. As the CO2 expands, and drops pressure, a huge amount of temperature drop occurs, which necessitates the use of heat during expansion. For lower CO2 gas pressure, a heat exchanger or chiller can be utilized to lower gas temperatures on the back end of the collection vessels, which lowers the pressure.
There are a number to techniques to help reduce or eliminate carry-over. One innovation that Infinity Supercritical has developed, is using electrostatic precipitation. A small charge is introduced (passively) into the CO2 gas and entrained oil, which charges the oil and makes it stick to the nearest opposite charged surface (collection vessel).
Cannabis oil which is not collected (termed carry-over), will continue through the closed-loop system and can clog the diaphragm pump, or the liquid CO2 pump, which will required down-time and maintenance to change the spring energized seals, and o-ring seals. This is such a problem with many commercial extraction systems, that many operators have complete spare pumps which they can replace, so that the downtime of the processing is kept to a minimum.
Contributors: Clinton S and Infinity Supercritical Staff.