Category Archives: Crystallization

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Pesticide Removal from Fish Oil by Short Path Distillation


Aug 2022

Pesticide Removal from Fish Oil by Short Path Distillation

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Fish oil is a valuable nutrient and well-known for its high omega-3 fatty acid content. In general, the fatty acid spectrum is considered to have a positive impact on health, especially EPA (eicosapentaenoic acid) and DHA (docosaheaxanenoic acid). High EPA/DHA oils are highly sought after and achieve high market prices. However, depending on the source of the oils, they typically contain a considerable amount of so-called POPs (persistent organic pollutants) that are not easily bio-degradable and thus accumulate in nature. Many of these POPs are quite toxic even in extremely small concentrations below ppm levels, including PCBs, halogenated furans and dioxins, brominated phenyl ethers, DDT etc.

Specifically, fish liver oils have relatively high concentrations of POPs which exceed the limits given by legislation of many countries. In this case, Short Path Distillation can help to reduce the content to an acceptable level.

Short Path Distillation (sometimes referred to as Molecular Distillation) is a wiped film technology that can operate at extremely low absolute pressures down to 0.001 mbar. This is achieved by eliminating all usual pressure drops that occur in classical distillation equipment. By continuously feeding into a heated vertical evaporator and spreading the feed to a very thin film on the inner evaporator wall by a specifically designed rotor, no hydrostatic pressure hinders the evaporation, taking smoothly place from the surface of the wiped film. The generated vapors will then have a quite short path from place of evaporation to the place of condensation, as the condenser is packed concentrically inside the evaporator shell. By this construction, the usual pressure drop by vapor mass flow to an external condenser is also removed, thus the equipment can operate at the extreme low vacuum conditions. This in turn enables to distill at temperatures that are reduced by 150-200 K compared to a distillation at ambient pressure. Short Path Distillation can therefore be considered the gentlest distillation process, which opens distillation to separation tasks that would not otherwise be possible.

SPDU with cross section

SPDU roller type rotor top view

By optimizing the crystallization process with our pilot size Technoforce Plug Flow Crystallizer, we were able to maximize yield with a narrow crystal size distribution for the monomer. The solution was directly coming from the upstream depolymerization at elevated temperature and was gradually cooled down at two different cooling media temperatures in one single TPFC. Thus, in one step we achieved the desired separation, while for demands of even higher purity it is always possible to repeat the crystallization by using either the same or a different solvent, a process known as re-crystallization.

In our laboratories in Nashik/India or Geleen/The Netherlands we can offer our customers bench scale and pilot scale crystallization trials in our continuous Plug Flow Crystallizers. Choice of suitable solvent as well as some pre-investigations regarding solubility curves should be performed by the customer beforehand to speed-up the project.

Technoforce has already designed and built several hundred skids of process intensification technology for oils and fats applications, fine chemistry, polymers, food and pharma products and other industrial sectors. We also offer other evaporation technologies like Short Path Distillation, Agitated Thin Film Evaporation and Drying, Falling Film, Rising Film and Forced Circulation Evaporation, as well as Liquid-Liquid Extraction in columns or centrifugal systems.

Typical SPDU skid unit

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Short Path Distillation
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