One-stage Dehulling

Technology Description

Farmet offers two versions of one-stage dehulling: one that lacks hull recovery and the other that includes hull recovery, which allows further dehulling of still-unhulled seeds.

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 refining are lower (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 goes through aspiration in air flow, where hulls are sucked into the cyclone I. Remaining material proceeds to pressing.
  
  
• Large: whole seeds and large hulls, which follow the same procedure as the mid-size fraction.

This technology is relatively simple and therefore does not achieve optimal results (one-stage dehulling cannot be expected to reach fibre content in sunflower seed press cakes of less than 20 %, which is a common requirement).

The version of one-stage dehulling with hull recovery involves further dehulling of the largest fraction of unhulled seeds), which leads to their repeated disruption. One-stage separation, however, does not secure separating out of the greasy dust and kernel fragments, which are carried by the air flow and separated out along with the hulls.

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 are separated out, which lowers the loss of kernel material and therefore oil loss.

This procedure is intended for smaller-scale technologies, especially for one-level cold pressing, where oil content in the press cakes is hi