Extraction Optimising Yield for Solid/Liquid Herbal Extraction

Editor: Doris Popp

A variety of leaves, stems, roots, seeds and barks are used in herbal extraction processes to produce traditional South East Asian and Chinese medicine, medicinal products, instant tea drinks and a wide variety of active ingredients and colours for use in industries such as food and beverage, pharmaceutical and cosmetics. The fundamental technology used has been around for many years, but SPX brings in-depth understanding and technological innovation to ensure yields are high and the process efficient.

The SPX design ensures an efficient filtration of the solids material, a self draining design and easy discharge of residues.
The SPX design ensures an efficient filtration of the solids material, a self draining design and easy discharge of residues.
(Picture: SPX)

The method for herbal extraction is very similar to making a cup of tea. Raw material is placed in a percolator and a solvent added (for tea this would be hot water). Parameters that affect the quality of the resulting product include temperature, time in the solvent, and ratio of solvent to active ingredient.

Rather than a cup or pot of tea, however, industrial-scale processes produce a few tonnes of product per hour and solvents used include fluids such as ethanol, acetone or ethyl acetate as well as water. The process temperature depends on the liquid utilised and typically varies from 70 °C to 90 °C, or up to 100 °C when water is being used.

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How to Handle Hazardous Solvents

Some solvents, such as acetone, are hazardous and may have regulations associated with management of their residue. To ensure careful treatment of such substances from a health and environmental standpoint, steam can be applied though the wet cake of exhausted material in the vessel, causing the solvent to evaporate. The vapours created are guided to a condensing system and discharged either for recycling within the system or to be transported to a recycling plant, depending on system requirements.

Equipment Developments

Traditional extractors are cylindrical with ingredients being added at the top. The mixture is then stirred to bring the solvent and raw material in contact. However, this method creates issues in the process with dust being swirled through the extract fluid, impacting the downstream process. Separating the liquid and solids at the end of the process for discharge also becomes more complicated.

SPX percolators have a conical shape which distributes the solvent homogeneously while enabling easy discharge of material after the process. The liquid passes between channels in the particles of the raw material and through a sieve at the bottom of the machine. The raw material is not stirred during the process, leaving the solid bulk within the vessel undisturbed. This is combined with internal filtration during the extraction cycle to ensure that the liquid can be easily discharged at the end of the cycle. This system design requires less volume for extraction and enables the solvent to be conveniently handled in buffer/storage tanks.

Customise Your Extraction Process

Pressure can be varied from –1 to 24 bar for best process results and the filtration within these vessels offers a simpler and more efficient method of extraction. Integrated solvent recovery and liquid discharge supported by a vacuum further help with the process efficiency.

As much as technology helps to improve the yield and efficiency from the extraction process, understanding of the application and its goals are of vital importance to ensure optimal production.

Field-Tested

SPX has a test centre in Warendorf, Germany, where pilot extraction, evaporation, distillation and drying can be carried out to trial processes and parameters used to ensure an efficient process with optimised yield and high-quality results. Pilot plants can also be rented for use at a customer’s site. Utilising the test centre and pilot plants can help determine the best type and ratio of solvent to raw material for new products and evaluate economic efficiency before investing in full-scale production capability. They further enable the design of the final system to be optimised to exactly meet the application needs and production goals.

SPX e&e Series technology is fully engineered to meet the requirements of each specific application. It is designed to be flexible, enabling adaption to different product batches, changing consumer demands and the fashions of the marketplace. Systems can be designed to handle hundreds of different raw materials to produce large batches, or just a few hundred litres of extract.

Yield is of primary importance to production costs and SPX extraction vessels are designed to maximise yield and process efficiency. Automatic filling along with quick and easy discharge of raw material and cleaning enable increased productivity with rapid changeover between batches. The process can offer steaming, vacuum stripping, percolation and solvent recovery with batch sizes from 50 l up to 20 m3. SPX extraction plants have easy accessibility and low maintenance needs with assured hygienic standards maintained through clean in place (CIP) and sterilise in place (SIP) capability. kem

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