Ethanol (Cold Ethanol Extraction)

Cold ethanol extraction is a common method for extracting oils from plant materials. Due to its polarity, ethanol is chilled to subzero temperatures to avoid extracting additional, less desirable water-soluble molecules.

In this application biomass is placed in vessel and cold ethanol solvent is pumped in. The desired oils are rapidly dissolved in this solvent. Unlike hydrocarbon solvents, ethanol has no risk of leaving toxic residual chemicals in the product, which is especially important if for human consumption.

Pumps in this application may be used for circulating or transporting ethanol and the extract solution, often with some plant materials included, at temperatures as low as -94ᵒF (-70ᵒC). Pure ethanol viscosity is >4 cPs at these low temperatures, extract solution is even greater.

Positive displacement pumps are optimal for this application due to the ability to handle small, soft solids; the ability to develop higher pressures as filtration becomes blinded; the need for self-priming, the adjustable flow rate with variable speed drive, and the ability to handle varying viscosity.

Viking in the Process

Viking developed a special series of pumps for this application to be able to handle the extremely low temperatures and other requirements. The pumps circulate ethanol through the chiller and pump it to the extraction vessel, and then draw out the extract liquid and pump it through filtration to an evaporator where pure ethanol is recaptured for reuse, while the product oils are concentrated and removed.