Contents lists available at ScienceDirect Industrial Crops & Products journal homepage: www.elsevier.com/locate/indcrop Characterization of oilseeds mechanical expression in an instrumented pilot screw press Laurine Bogaert, Hebert Mathieu, Houcine Mhemdi ⁎ , Eugène Vorobiev Sorbonne Universités, Université de Technologie de Compiègne, Laboratoire Transformations Intégrées de la Matière Renouvelable (UTC/ESCOM, EA 4297 TIMR), Centre de Recherche de Royallieu, CS 60319, 60203 Compiègne Cedex, France ARTICLE INFO Keywords: Screw press Oilseeds Modeling Instrumentation Expression ABSTRACT This work studies oil seeds mechanical expression in a screw press. For this purpose, a pilot-scale screw press (0–40 kg/h) was instrumented by installing sixteen pressure sensors and three temperature probes throughout the screw. Canola (Brassica napus L) and flax (Linum usitatissimum) seeds were used for investigation. The impact of the screw rotation speed on the press performances and the matter flow inside the press was investigated. The screw press capacity, passage time, extraction yield and specific energy consumption were studied is the range of 0–18.2 rpm. For each experiment the radial pressure, the internal residual oil content and the matter velocity evolution were measured all along the screw. Results show that increasing the rotation speed enhances the press capacity and decreases the passage time, reduces the extraction yield and the specific energy consumption. The recorded data allowed the identification of different functional sections of the screw press (feed, compression and mixing/relaxation sections) in relation with the screw geometry. In the compression sections, high pressure leads to oil expression and the formation of hard cake. In the mixing sections, pressure falls to zero and press-cake becomes friable. The matter velocity in the mixing sections is quick as compared to that in compression sections. Furthermore, results show the existence of oil reflux phenomena inside the screw press cage. Based on the obtained results, the continuous screw press behavior was schematized as a succession of several individual batch presses with intermediates steps of press-cake mixing and oil refluxes in order to facilitate process modeling. 1. Introduction Solid–liquid expression (pressing) is a unit operation in which a li- quid is separated from a solid–liquid mixture by mechanical compres- sion. It is widely used in food and related industries, to express juice and vegetable oils from cellular materials. Hydraulic presses ensuring discontinuous and unidirectional compression are often used on la- boratory and pilot scale. Screw presses are implemented at the in- dustrial scale for continuous pressing of oilseeds (Beach, 1983; Hoffman, 1989; Homann et al., 1978; Laisney, 1983; Tindale and Hill- Haas, 1976; Ward, 1976). Industrially, seed oil recovery is achieved by a sequential process of mechanical expression and hexane extraction. Mechanical expression is generally considered as the most efficient technique to recover virgin oil of high quality, but it only allows a partial defatting of the seeds. Therefore, the resulting press cake is usually defatted by means of percolation with hexane. Screw presses are the most prevalent equipment used for oil seeds expression. A screw press consists of an horizontal or vertical screw fitting closely inside a perforated cage (frame) where liquid (oil) is expelled. Both screw and cage are tapered toward the discharge to increase the pressure on the material. The screw press performances mainly depend on the applied/developed pressure. Contrarily to a hydraulic press where the applied pressure can be set to the desired level, the pressure developed in a screw press is rather difficult to control and predict. Batch pressing has been intensively studied and referred in the lit- erature, as a first approach for understanding the expression me- chanism (Daun et al., 1993; De Ginestel, 1998; Hickox, 1953; Lanoisellé, 1996; Savoire, 2008; Willems et al., 2008). The impacts of seeds pretreatments (moisture conditioning, dehulling, flaking and cooking) and pressing parameters (pressure, temperature and time) have been studied for different oil seeds (sunflower, flax seed, rapeseed, etc.). Experimental data were analyzed and different phenomena were identified (air expulsion, primary and secondary consolidation, creep). https://doi.org/10.1016/j.indcrop.2018.04.039 Received 21 November 2017; Received in revised form 10 April 2018; Accepted 15 April 2018 ⁎ Corresponding author at: Université de Technologie de Compiègne Département de Génie des Procédés Industriels Laboratoire Transformations Intégrées de la Matière Renouvelable (UTC/ESCOM, EA 4297 TIMR) Centre de Recherche de Royallieu, CS 60319, 60203 Compiègne Cedex, France. E-mail addresses: h.mhemdi@escom.fr, h.mhemdi@live.fr (H. Mhemdi). Industrial Crops & Products 121 (2018) 106–113 0926-6690/ © 2018 Elsevier B.V. All rights reserved. T