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HEMP/CBD OIL
Sucessful extraction Solid liquid extraction has been described as the removal of a soluble material from an insoluble permeable substrate with a liquid solvent. Keeping in mind that water and alcohol are solvents, solvent extraction has been around for thousands of years for tinctures, nutraceuticals, flavours and coffee. As a unit operation, extraction can be broken down into at least four separate steps including: • Diffusion of the solvent into the solid particle • Dissolution of the extract into the solvent within the solid • Diffusion of the dissolved extract from within the solid to the surface • Washing the extract-rich solvent from the surface of the solid particle Solvent extractors must be designed to carry out these steps efficiently, at low cost, while minimising the labour force required to run the plant. To date, the largest and most industrial application has been the extraction of vegetable oil from oilseeds – such as soyabeans, canola, sunflower and new crops such as pongamia and camelina – most often using hexane as the solvent. Plant capacities can be as high as 12,000 www.ofimagazine.com
Hemp.CBD processing.indd 2
Many of the technologies and principles of continuous extraction used in the oilseed industry apply to the extraction of cannabidiol oil and production of hemp protein Richard Ozer tonnes/day, with plants managed by a single operator at the control station. Alternate solvents such as hydrous ethanol allow extraction of sugars and other phytochemicals from de-oiled vegetable seeds resulting in vegetable protein concentrates. These products have been used to retain moisture in meats during cooking and are the backbone of the meat analogue business currently taking the world by storm. From there, applications have grown to include salt from gels, polyester from shirts, purifying polymers, to hemp and hemp protein. Based on these well-developed extraction technologies, hemp has been successfully extracted with a variety of solvents, according to several considerations including: • Extraction efficiency. • Final end user perceptions. • Thermal values of the solvent and its effect on operating costs. • Components extracted by the solvent
and its effect on overall operating costs, for example, the extraction plant, winterisation and refining.
Continuous extraction
From batch and earlier extraction processes, the solvent extraction industry has grown and matured to involve a continuous process with well-integrated unit operations to facilitate safe, efficient, and easy-to-operate facilities. Many of the principles of continuous extraction in the oilseed industry apply to the extraction of cannabidiol (CBD) oil and production of hemp protein. A continuous solvent extraction plant is broken up into several unit operations: • Solvent extraction. • Desolventisation of the solids – where the oil is the principal product – where the solids are the principal product. • Distillation to recover solvent from the oil. u • Off gas handling. OFI – JULY/AUGUST 2022
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