A new twin‐screw press design for oil extraction of dehulled sunflower seeds

Transport of material in a single‐screw press depends mainly on friction between the material and the barrel’s inner surface and the screw surface during screw rotation. Thus, a solid core component, like seed hulls, is often necessary to produce the fraction. This sometimes causes excess frictional heat, large energy consumption and oil deterioration. Furthermore, if single‐screw presses are not configured with breaker bars or other special equipment, they provide inadequate crushing and mixing. A twin‐screw oil press can be expected to solve these problems because of the higher transportation force, similar to a gear pump, and better mixing and crushing at the twin‐screw interface. A twin‐screw press (screw diameter=136 mm, length/diameter=6.5, screw speed 15–100 rpm, feed rate=50–150 kg/h) was designed with partially intermeshing and counter‐rotating screws and was tested on dehulled sunflower seed. The results were compared to a single‐screw lab‐scale press. Dehulled sun‐flower seed (wt, 6.0%; oil, 58.6%) without pretreatments (crushing or cooking) gave 93.6% oil recovery with the twin‐screw press, in contrast to 20% oil recovery with the single‐screw press. The oil expressed with a twin‐screw press had less foreign material than the oil from the single‐screw press. Other properties of the oil were also good. Energy consumption of the twin‐screw press was more efficient. All results suggested that oil production from dehulled sunflower seed with a twin‐screw press is highly efficient.