While some growers dry their plants, the chance for mold growth in the presence of heat or moisture may be too great. Storing hemp at low temperatures reduces the loss of CBD from the plant, which breaks down from heat and oxidation.
After separating from the extract, the pressurized solvent moves to the expansion filter where pressure is reduced to convert it back into a gas. Filters capture any particulate matter as the solvent moves out of the expansion filter and into the recovery container where it is pressurized back into a liquid and stored for use in subsequent extraction batches.
Fortunately, Klinge Corporation offers freezer equipment for maintaining temperatures down to -70°C and blast freezing down to -60°C. The equipment comes installed into insulated 40 foot long shipping containers, and some of the equipment can also be installed onto existing freezer rooms as well. Provided the facility has permission to store ethanol in a container without explosion proofing, this could be an excellent solution.
Producers have several options for extracting the oil from the hemp. These use both polar and non-polar substances (supercritical fluids, solvents, or alcohols) to dissolve cannabinoid compound from the plant. All of the below methods rely on accurately controlling the temperature during the process. Excessive heat during any step of the process can result in the loss of cannabinoids through oxidation.
Additional Temperature Control Applications for Hemp Processing
Because carbon dioxide is not flammable nor noxious, this method proves safer compared to hydrocarbon extraction, but the overall equipment and operating costs can be higher as well.
This process starts with the pressurized liquid solvent mixing with the hemp in an extraction column. After soaking, the operator sends the pressurized liquid through a screen and into a collection tank. The screen filters out solids from the mixture, allowing the combined extract and solvent to move into the collection tank.
The waxes and lipids will then need to be removed. This can be achieved by winterization (please see below) and afterwards a large percentage of the alcohol can be reclaimed through rotary evaporation to use in subsequent extractions.
Pressurized Hydrocarbon Extraction
When used as part of the alcohol extraction process, this would occur directly after filtering out pant material that did not get dissolved during alcohol extraction. If used as an additional refinement in a pressurized hydrocarbon extraction, the processor will need to take the ‘crude oil’ from the extraction and mix it with liquid ethanol until it has been fully dissolved. At this point, the winterization process will be the same regardless of the initial extraction method.
During vacuum distillation, the extract undergoes a high heat process under a vacuum. Temperatures range from 180 to 220 degrees Celsius, 356 to 428 degrees Fahrenheit. The finished product contains 60% to 90% cannabinoids. The heat allows for producers to separate individual compounds from the extract for higher purity.
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 Nutsche filter dryer to produce pure, dried crystals. The Nutsche 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.
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).
Delta T Systems – Your partner in Pure Temperature Control
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.
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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.
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.