Two-stage Dehulling

Technology Description

This technology is an excellent solution for large-scale press shops. It is optimized for high oil yields and a high quality of press cakes for feed purposes.

Here is a list of advantages of dehulling prior to pressing (and achievable parameters):

1. Fibre content reduction leading to a higher-quality feed.
   
   
2. Increased oil yield. If unhulled seeds are pressed, a fraction of the oil remains soaked in the hulls in press cakes.
   
   
3. Less wear of the pressing machinery. Hulls are very abrasive and reducing their content increases the service life of compression screws. However, the high abrasiveness also affects the dehulling machine and all the elements along the transport path of the hulls, where extreme stress must be counted with. To extend the service life of parts that come in contact with the hulls, we only use top-quality materials and procedures.
   
   
4. Reducing wax and pigment content in oil. Waxes and colours (pigments) are found almost exclusively in the hull. Thus, removing most of the hull leads to a decrease in the wax content of pressed oil. The oil can be filtered more easily and the costs of oil processing are lower (e.g., winterization and bleaching).

After dehulling the seeds are sorted, at a first-stage sieve separator, into the following fractions:

• Small: oily dust, which proceeds to pressing.
• Mid-size: small seeds, kernels and their fragments; pieces of hulls. This fraction is destined for further processing (stage II).
• Large: whole seeds and large hulls. This fraction goes through aspiration in air flow, where hulls are sucked into the cyclone I. The leftovers after aspiration – intact seeds – are re-routed back into the huller to be processed again.

Mid-size fraction from the stage I sorter is carried into the stage II sorter, where it is separated into fractions:

• Large: a small amount of seeds, whole kernels and their larger fragments, large hulls. These are transported into the aspirator, where free hulls are aspirated into the separating cyclone. Remaining kernels and their fragments proceed to pressing.
• Mid-size: mid-size seeds, kernels and their fragments, small hull parts. These undergo aspiration in the air flow, where hulls are sucked out into the cyclone II. The rest proceeds to pressing.
• Small: small kernel and hull fragments, which are processed in the aspirator. Free hull fragments are sucked out into the separating cyclone. Remaining kernel fragments proceed to pressing.

The technology can be supplemented with the feature “HULL CHECK”, whereby the already separated hulls are sieved and aspirated again. Oily dust along with kernel remains that have been aspirated are separated out, which lowers the loss of kernel material and therefore oil loss.