Temperature Control for CBD/THC Extraction and Distillation

 

The legalization of the hemp cannabis derivative CBD and of marijuana and its THC derivative for medical and recreational purposes in many US states and all of Canada has led to significant economic growth in the CBD/THC extraction and distillation equipment sector. Many of the manufacturers of these two categories of 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, chemical, petrochemical 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 (OEMs).

There are quite a few different approaches to extraction and distillation of CBD/THC products, and each has certain benefits as well as some less desirable side effects; but they all have in common these parameters that need to be controlled: temperature, pressure or vacuum, source material throughput volume, and for extraction, solvent feed rate.

 

Extraction Process – Temperature control considerations

 

Current extraction processes include CO2, butane or propane, and ethanol.  In each of these methods, the extraction agent is cooled down to temperatures that can reach -80°C (-176°F) 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 (TCU) which 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 in fact on a continuing basis over a large number of batches.  Controlling temperature to within .275°C (.5 °F) is a standard that permits a consistent finished product.  It is also important to note that repeatability, in addition to accuracy is extremely important for producers as it allows them to replicate the process over time, and thus insure 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
• increase wax/resin extraction and overall volume, but yield a lower quality product

Similarly, decreasing extraction temperature can lead to:

• increase the concentration of oil in the extract
• reduce the wax proportion of the extract

For these reasons, having equipment that is capable of consistent and accurate temperature control is very important to producers; and as there is demand for many variations of this extraction process’ final product, chilling equipment and temperature control units with high precision, closed loop controls are critical.

Once the extraction process is complete a processor is left with “crude extract” that is 55- 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 -20°C (-4°F) in a chiller-driven jacketed vessel. This “winterization” process precipitates some of the undesired elements out of the solution which after filtering, leaves oil made up of cannabinoids, chlorophyll and terpenes. Decarboxylation is an important step that may 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).

 

Distillation Process – Temperature control consideration

 

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 though 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 that is 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, molecular short-path stills.  In this approach, the feedstock of oil is fed into a jacketed vessel that is often heated with an oil circulating TCU to achieve temperatures up to 343°C (650°F), though the typical distillation temperature range is 130 -180°C (266-356°F). 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 TCU controlled central condenser unit which is cooler (typically 60-70°C / 140-158°F) than the evaporation chamber and serves to attract the cannabinoid vapor.  The final step in the process is solvent removal, which is accomplished in a separate, external cold trap, which is also temperature controlled with a chiller.

Certain OEMs offer wiped film molecular short-path 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 separation 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°C to -20°C.  A slurry results and that is transferred to a filter dryer to produce pure, dried crystals.  The filter is a jacketed vessel whose temperature is controlled with a circulating hot oil unit. The process results in a 98% or higher purity of the CBD or THC product.

Chillers

• Capabilities from 1-60 tons (higher capacities offered as custom designs)
• Variable speed design that can cut energy usage up to 50%
• Standard operating range from -18°C to 27°C (0°F to 80°F)
• Highly accurate closed loop temperature control to .275°C (.5°F)
• Data logging with remote control and analysis tools
• Industry 0 ready
• Long life heat exchange materials and low maintenance design

Temperature Control Units (TCUs)

• Water Circulating Temperature Control Units (TCU) will perform in processes up to 300°F (149°C)
  • ¾ to 7 ½ HP Pump, 25 to 150 GPM
  • 9 to 144 KW Low Watt Density Heater
  • 149°C (300°F) Fluid Operating Temperature
• Oil units up to 343°C/650°F
  • 6, 12, 18, 24 or 36 KW Heaters, or special designs up to 360 KW
  • Maximum Operation Temperature up to 343°C (650°F)
  • 10 to 150 GPM Pumping Capacity
  • Heating Only or Heating with Cooling Capabilities
• Dual circuit combination TCU/Chiller units