28/07/2022 HRS Heat Exchangers Ltd
By Matt Hale, International Sales & Marketing Director, HRS Heat Exchangers
Health products and functional medicines containing CBD (cannabidiol) are growing in popularity, with the UK market now worth £690 million a year according to trade association ACI1, making it the second largest market of the world after the United States. However, traditional extraction processes do not always take advantage of the latest evaporation technology.
In fact, current market growth is outpacing even industry predictions, and it has been estimated that with the right political support, the European market for legal cannabis products could be worth around €3.2 billion a year 2025
What is CBD?
CBD is a chemical extracted from the hemp and marijuana plants, and although it is an active ingredient in the cannabis drug, it does not cause the psychoactive effects associated with THC, which is also found in plants. Although medical studies are inconclusive, some of the claimed benefits of CBD include reducing inflammation, improving relaxation and focus, and slowing digestion. As such, it is often used to treat problems such as anxiety and insomnia, as well as some types of seizures and some digestive complaints.
How is CBD extracted?
There are a number of different techniques for extracting CBD from the hemp plant, although most of these require the use of solvents that are effective at separating CBD from other chemical compounds found in the plant. Once the CBD is extracted, the solvent evaporates leaving pure CBD oil.
Some methods use supercritical carbon dioxide in a closed-loop extractor to extract the CBD under pressure, resulting in a liquid mixture of CO2 and CBD, which must then be separated by evaporation, but a solvent step is usually still required alcoholics For this reason, the use of liquid solvents based on alcohols (ethanol, or isopropyl alcohol – IPA) or hydrocarbons (butane or propane) is also sometimes used, which are much simpler and more direct. However, unless the evaporation step is performed correctly, some residual alcohol may remain in the CBD oil mixture.
It is important to remember that even when CO2 extraction is used, another step involving alcoholic solvents will still be required. Each method has its own advantages and disadvantages and the best method for one manufacturer may not be suitable for another.
Once CBD oil has been separated from the solvent, it is usually refined and distilled to produce pure CBD oil that is free of other compounds such as THC, waxes, and lipids. The exact nature of this refining process will affect the chemical profile of the resulting CBD product and also depends on the extraction method used.
Considerations for evaporation
To maintain the characteristics of CBD oil, low temperature evaporation techniques must be used, often involving separate vacuum extraction systems to lower the boiling point of the solvent.
On a small scale, laboratory-based rotary evaporation systems (with or without vacuum extraction) may be adequate and are in fact one of the most common systems in use today. But as the market grows and producers need to increase production, they are likely to look to the type of low-temperature evaporator used in pharmaceutical or food production. Additionally, maximizing solvent recovery with this system requires a high level of vacuum control and therefore often requires specialized process supervision.
Multi-stage fallen film evaporation processes are very efficient and allow for much higher yields. As a continuous system, there is no need to disassemble and clean between each run and clean-in-place (CIP) is used to maintain hygienic conditions and prevent contamination. Having different temperature regimes in each evaporation stage improves ethanol removal and the unit is highly efficient as each evaporation stage is maintained at a lower pressure than the previous one.
With 40 years of experience in supplying heat exchangers and evaporators for the pharmaceutical and food industries, HRS offers equipment that meets the highest standards of hygiene and traceability and is well placed to support the rapidly growing CBD industry to fulfill its market potential.
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