Oil press

The oil press is a device for pressing oil from plant seeds or fruits and the central element of an oil mill . It is used in both central and decentralized oil mills . In it, the pressed material (oil fruits and seeds) is processed into vegetable oil and press cake .

Screw press with scourtins

Lever tree press with scourtins

Procedure

During the pressing process, which works with increasing compaction, the material to be pressed goes through different phases. When compressing without releasing liquid, the plant cells are first opened up and air escapes from the cavities. The actual oil separation takes place in the compression phase with the release of liquid, during which the pore volume is reduced and oil is released at the same time. After the oil has been dispensed, the press residue is shaped.

Ancient and Middle Ages

There are no major differences between ancient and medieval oil presses - the pressed material crushed by oil mills was filled in basket bags (French: scourtins ) made of palm leaves , hemp or other materials ; these were stacked one on top of the other in the press and pressed out by means of a lifting beam , which was pressed further and further down by rope winches etc. and wedge-shaped timbers etc. however, this method has proven to be too ineffective and impractical over time. With the screw presses that came up later, the basket bags, which in the 20th century were also made of coconut fibers , plaited plastic cords or metal wires, had to have a hole about 15 cm in the middle. The oil flowing out was first caught in a round stone with a one-sided outlet and from there it was filled into containers made of wood (vats), ceramic ( amphorae ), metal (buckets) or glass (bottles).

Modern times

Goods screw presses known since ancient times, today mainly so-called coming screw presses used. In general, these work on the same principle as a meat grinder . The pressed material is transported in a cylinder by means of a screw (spindle) and is separated into uncleaned trub oil and press cake by being squeezed out . The material to be pressed is fed to the cylinder through a funnel. The cylinder hole screw press and the strainer rod screw press are available as designs.

Screw presses, which are followed by extraction, reduce the oil content to approx. 20% and are known as pre-presses. In oil mills without extraction, on the other hand, the aim is to keep the residual oil content in the press cake as low as possible (from approx. 10% residual oil content).

Cylinder screw press

Individual parts of an IBG Monforts Oekotec cylinder hole screw press

In the cylinder hole screw press there are small bores at the rear end of the cylinder through which the pressed oil emerges. As a result, the product to be pressed is pressed by the screw against a mouth that is attached to the end of the cylinder. The solid components of the material to be pressed (press cake) are pressed out in the form of pellets through the orifice (press nozzle) .

Colander screw press

View into an open strainer screw press. The pressed oil comes out between the strainer bars.

In the strainer rod screw press, the cylinder is formed by rods arranged in parallel, which are arranged around the screw with small gaps. These are called strainer bars. When the pressed material is processed, it is transported through the screw and the oil escapes through the squeezing between the bars. The strainer bars are held in place by rings. The press cake is ejected in the form of small plates at the end of the screw.

Products

In the oil press, oil seeds and fruits are processed into vegetable oil or vegetable fats and the by-product press cake , also called oil meal. The vegetable oils are used as food and feed as well as in the technical area (chemistry, biofuels ). When pressing the oil products, the aim is to keep the temperature as low as possible. This guarantees a high product quality. In larger plants (central oil mills) the pressing is supplemented by extraction with solvents in order to increase the oil yield from the raw material.

literature

FNR: Handbook Production of Rapeseed Oil Fuel in Decentralized Oil Extraction Plants (PDF file; 5.41 MB)
Barbara Eder, Franz Eder: Vegetable oil as a fuel . ISBN 978-3-936896-05-3 .
Martin Kaltschmitt, Hans Hartmann, Hermann Hofbauer (Hrsg.): Energy from biomass. Basics, techniques and procedures . Springer Verlag, 2009, 2nd edition, pp. 715–716 and 727–728, ISBN 9783540850946 .

Web links

Commons : Oil Press - Collection of images, videos and audio files

Oil mill and oil press - Medieval Lexicon

Individual evidence

^ William Roger Paton , John Linton Myres : On some Karian and Hellenic oil-presses. In: Journal of Hellenic Studies 18, 1898, pp. 209-217.

[1] William Roger Paton , John Linton Myres : On some Karian and Hellenic oil-presses. In: Journal of Hellenic Studies 18, 1898, pp. 209-217.