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Guangzhou Scikoon Industry Ltd. Co.
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2024 Posters

Processing

Session: Processing Poster Session

Evidence of a speed dependent critical pressure for the mechanical extraction for high-oil and low-fiber matrices.

Monday, April 29, 2024
5:00 PM – 6:00 PM EDT
Abstract: Sunflower kernels contain about 60% of oil and practically no fiber. Their mechanical extraction in screw presses leads to poor performances, like low throughput or poor oil yield. Studies about the topic are explaining the phenomenon by change in friction related to the absence/presence of the hulls, or by a low cake viscosity. To our knowledge the existence of a critical pressure, related to the compression speed, has never been described before. The critical pressure, in the case of a steady speed unidirectional compression, is the pressure at which the solid phase extrudes through the press orifices.
The study used a unidirectional press made up of a Omnitest Mecmesin 25 tester with a 50 kN sensor which moves the piston of the compression cell. A hollow cylinder, having a 40 mm inner diameter and 4 mm thick wall, contains the seed bed. Its temperature is controlled by a heating collar connected to a regulator. The piston slides in the hollow cylinder to compress the material at a controlled speed until it reaches the maximum pressure (35 MPa). In our experiment, constant compression speeds from 0.1 mm.min-1 to 20 mm.min-1 were tested at 65°C using 15 g of sunflower seeds or hulled kernels at 5% water content. Applied force and cylinder displacement were recorded by intervals of 0.02 sec.

The critical pressure evidenced here can be easily reached in industrial presses. Unlike piston presses, in screw presses, the material can flow back upstream and impede the axial displacement of the cake.  These observations are improving our understanding of the poor performances of screw presses with low-fiber high-oil content materials and could be useful for the design of better presses geometries.