The legalization of hemp-derived CBD and of marijuana extracts for medical and recreational purposes in many U.S. states and all of Canada has led to significant growth in the CBD/THC extraction and distillation equipment sector. Many manufacturers of this equipment have been in business for a number of years, and the processes used for extraction and distillation have been refined over decades since they are used to extract and purify many different organic substances, chemicals, petrochemicals and alcoholic beverages.
However, hemp and marijuana have their own unique characteristics, and the processes to extract and purify CBD and THC from their respective plant sources are still being fine-tuned by processors and original equipment manufacturers.
There are quite a few different approaches to extraction and distillation of CBD/THC, each with their own benefits and less desirable side effects. But they all have common parameters that need to be controlled: temperature, pressure or vacuum, source material throughput volume and, for extraction, solvent feed rate.
Current extraction processes include CO2, butane, propane and ethanol. In each of these methods, the extraction agent is cooled down to temperatures that can reach minus-80 degrees Celsius and then compressed until it is liquefied. The temperature reduction is achieved using a chiller, which can be a standard piece of equipment or a custom unit designed to meet unique temperature profile requirements.
In commercial systems, extraction is typically performed in a jacketed vessel. Water, oil or other liquids are circulated within the jacket by a temperature control unit that maintains consistent vessel-wall and extraction-chamber temperatures.
Temperature control is necessary throughout all the steps in the process, but precise extraction chamber temperature control is absolutely essential to managing final product quality and characteristics. This high level of control must also be replicable from one batch to another and on a continuing basis over a large number of batches. Controlling temperature to within 0.275 degrees Celsius is a standard that permits a consistent finished product. Repeatability, in addition to accuracy, is extremely important for producers as it allows them to ensure consistent product quality.
For example, increasing the extraction temperature from the initial agent temperature can:
– Decrease the concentration of terpenoids in the extract;
– Risk denaturing the final CBD/THC product; and
– Increase wax/resin extraction and overall volume, but yield a lower quality product.
Similarly, decreasing extraction temperature can:
– Increase the concentration of oil in the extract; and
– Reduce the wax proportion of the extract.
For these reasons, having equipment that is capable of consistent and accurate temperature control is very important. Because of the demand for different product variations, chilling equipment and temperature control units with precise, closed-loop controls are critical.
Once the extraction process is complete, a processor is left with “crude extract” that is 55% to 75% cannabinoid and that may, in some instances, be sold without any further processing. For the majority of processors however, further separation of the remaining elements is necessary to obtain fully purified, high-value CBD/THC oil.
The next step in the purification process is to remove waxes by cooling the extract down to approximately minus-20 degrees Celsius in a chiller-driven, jacketed vessel. This “winterization” process precipitates some of the undesired elements out of the solution, which after filtering, leaves an oil made up of cannabinoids, chlorophyll and terpenes.
Decarboxylation is an important step that can be performed either before or after the winterization process. It is used to activate CBD/THC components and is accomplished by carefully heating an extracted solution to release the carboxyl ring group (COOH).
A distillation process is then conducted to complete the separation of the remaining elements and produce the purest possible CBD or THC oil. It is worth noting that even if a source material has been winterized, as much as 40% of the remaining feedstock may consist of undesirable materials. Also, in the case of ethanol extraction, ethanol must then be evaporated to separate it from CBD/THC components.
As in the extraction process, the distillation process used to fully purify CBD/THC oils requires closely controlled temperature, pressure and source material feed rates to ensure that the necessary interactions produce a high-quality finished product with characteristics that generate the highest possible value.
The most common pieces of equipment are wiped film short-path molecular stills. In this approach, the feedstock of oil is fed into a jacketed vessel that is often heated with an oil circulating temperature control unit to achieve temperatures up to 343 degrees Celsius, though the typical distillation temperature range is 130-180 degrees Celsius. In these systems, the feed stock is distributed on the evaporation chamber wall with a special wiper. The resulting thin film allows the more volatile terpenes to evaporate through the top of the chamber into their own external collection vessel, while the CBD/THC is collected along a temperature-controlled central condenser unit which is cooler (typically 60-70 degrees Celsius) than the evaporation chamber and serves to attract the cannabinoid vapor. The final step in the process is solvent removal, accomplished in a separate, external cold trap, which is also temperature controlled with a chiller.
Certain equipment manufacturers offer wiped film short-path molecular distilling equipment that integrates the removal of heavier materials directly into their distilling process. In this instance, chlorophyll, waxes and other heavier residue (up to 40% of the feed stock) descend the outer wall of the distillation vessel and are collected in their designated container.
In certain cases, a final step is taken to separate THC from CBD. Crystallization is a common method. A reactor vessel is filled with feedstock and a solvent which is chilled slowly from 60 degrees Celsius to minus-20 degrees Celsius. A slurry results and that is transferred to a Nutsche filter dryer to produce pure, dried crystals. The Nutsche filter is a jacketed vessel in which the temperature is controlled with a circulating hot oil unit. The process results in a 98% or higher purity of the CBD or THC product.
Dan Brandenburg is the director of sales and marketing at Delta T Systems. He can be contacted at 262-628-0331. Delta T Systems has worked with extraction and distillation equipment manufacturers, as well as end-user engineering groups, for more than 25 years, and designs products specifically to address customers’ production needs.