The oil which is emitted from the expeller presses have various solid content levels depending on the oil seed type and the condition of the press. In order to remove larger solid particles, the oil is usually fed into a settling tank, which is also serves concurrently as a buffer tank. In some installations, a vibrating screen is used for pre-cleaning, or the oil is taken directly from the press to the press oil clarification unit.
In order to support the separation process, the solids are sprayed with hot water. A water quantity of 1 percent in relation to the oil quantity is normally adequate in this respect. The water is transfused with the oil in the feed pump to the decanter. The decanter – a horizontal scroll-type centrifuge – continuously separates the solids from the oil.
As a counteraction of adding water, any present phosphatides are hydrated and removed along with the solids. In order to avoid oil loss, the solids are returned to the press. The purified oil is then either processed directly or stored and dried in a vacuum.