New approach for the elucidation of the phenomena involved in the operation of vegetable oil extraction presses☆

Abstract

In a context where the search for naturalness, the need to reduce the carbon footprint and the development of a decentralized crushing sector are intensifying, mechanical extraction is a technology that is regaining major importance for the industry. The performance of this technique remains far below what is desirable, while the understanding of the main phenomena involved in screw presses remains insufficient. This article, after a brief presentation of the state of the art of this discipline, presents a new model centered on the notions of pressure generation and plasticity. According to this approach, plasticity can account for parameters such as the water and oil content of oilseeds, their temperature, and their possible dehulling. Plasticity in turn would explain both the compressibility of the cake and its ability to resist the thrust of the screws, and consequently to generate pressure or to creep or flow backward depending on the geometry of the screw and the cage. The model must also incorporate the notions of compression velocity, friction, and the complexity of the interactions between these parameters and the impact of the succession of screw segments and cone rings. It has been built on observation and experience and gives an understanding of the need to work simultaneously on the conditioning and geometry of the presses to achieve improved performance in terms of energy, efficiency, and reduction of the temperatures experienced by the proteins and oils

Keywords

• screw geometry
• unidirectional pressing
• compressibility
• plasticity
• pressure generation