Digester and Pressing


Because of cooking, sterilizing, threshing and mashing made the pulp soft and damage pulp cell structure, the palm pulp becomes soft and cell is broken. Then it is sent to continuous screw press. After pressing, oil palm fruit is divided into two parts: the mixture of oil, water and solid impurities, and the press cake (fiber and nut).The pulp stone separation obtained CPO and stone, press machine adopts the double screw helix continuous discharge and hydraulic, greatly improving production efficiency.

Palm Oil press station: Separate palm fruit and kernel, and oil press machine can obtain CPO (crude palm oil) and palm kernel. The adoption of double screw and hydraulic oil press machine can greatly improving working efficiency during palm oil production.

Digester Machine

Digester Machine

The fruits are then digested in the digester.

The digester is like a big blender and has a central shaft with arms that rotate and mesh up the fruit. This action breaks up the oil cells and conditions the fibre for pressing. This process involves the crushing of the fruits and warming the pulp before oil extraction is done. Warming is important in order to maximize oil extraction. Sterilized stripped fruit is fed to digester. There is also the steam heater in masher. The steam is used to cook the palm fruit and broke the cell of pulp. Because of cooking, sterilizing, threshing and mashing made the pulp soft and damage pulp cell structure, the palm pulp becomes soft and cell is broken.

In the digester, the palm fruits are pounded and turned into a mash which consists of mesocarp, fibres and nuts containing kernels. This mash of digested palm fruits is transferred to the screw press where crude oil is pressed out.

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.Screw Press

Screw Press.

Palm oil screw press is made of a rod-shaped punctured enclosure and a narrowly fitting twin screw that rotate in opposite directions running through it. Due to the commotion and massage action that is applied on the fruit pulp in the pressing cage, screw presses are known as the most effective machinery in breaking open the oil cells that remain unopened and hence extract more oil. Screw oil presses can be viewed as an extra digester. They are ideal for the extraction of palm oil and other kinds of vegetable oil.

The pressure is normally automatically controller by a hydraulic system. The higher the pressure of the cone the more pressure is applied to the mesh. The hydraulic system gets feedback from the power consumed by the screw press motor (Amperes). The correct pressure is when a small percentage of nut break and the oil to dry matter of the press fibre is about 8 %. If the pressure is set to high the nut breakage increases and kernel is lost. A simple test is to take a small amount of fibre and twist it in the hand, No oil should come out of the fibre, and it should not stain a cloth.

After pressing, oil palm fruit is divided into two parts: the mixture of oil, water and solid impurities (crude palm oil), and the press cake (fibre and nut). The extracted oil is mixed with fruit particles, water, sand and dirt.  The press cake consists of palm fibre and nuts.The remaining fibres and nuts are recovered and dried.

The press cake is the transferred to the depericarper for further processing. The crude oil is first screened with a vibrating screen to remove the course fibres and other dirt and it is then pumped to the clarification station for further processing.

The press liquor (oil, water, sand and impurities) is flowing to the continuously settling tank, where oil and sludge are separated due to sedimentation. The top phase (or clarified oil) is pumped into a centrifuge for final clarification. Before the crude palm oil (CPO) is ready for storage in the clear oil tank and further processing, it passes through a vacuum dryer to reduce the moisture content in order to slow down hydrolysis and oxidation.