Palm oil is extracted from fresh fruit bunches (FFB) through a mechanical process that ensures the quality of crude palm oil. The primary products obtained in the palm oil mill are palm oil and palm kernel, with biomass as a secondary by-product.
The process stages in a palm oil mill consist of sterilization, stripping, digestion and pressing, clarification, purification, drying, and storage. For the kernels, the stages include nut/fiber separation, nut conditioning and cracking, cracked mixture separation, and kernel drying and storage. The dried kernels are further crushed through mechanical processes or solvent extraction to obtain crude palm kernel oil.
Sterilization is the primary stage, where the bunches are sterilized with live steam at 3 kg/cm². This process deactivates the enzyme lipase, preventing the build-up of free fatty acids. The sterilized bunches are then conveyed to the stripping section, where the fruitlets are detached and taken for further processing in the oil recovery section. The stripped bunches, coming out of the stripper, are conveyed outside the process plant for use as raw material in boilers.
Digestion: The fruitlets obtained from the stripper are fed into the digester, where the purpose is to disrupt the mesocarp of the palm fruit and break up the maximum quantity of oil-bearing cells to facilitate oil release.
Pressing: The hot digested mash is then fed into a screw press to extract oil. The resulting mixture of oil, water, and sludge is sent to the oil purification section. The press cake, which contains nuts and fibers, is sent to the nut recovery section.
Clarification: The oil-water-sludge mixture from pressing is pumped to a clarifier and allowed to settle. Here, the oil separates from the sludge and water. The clarified oil still contains small amounts of dirt and solid particles, necessitating further purification in a centrifuge.
The purified oil may contain residual moisture, which needs to be removed before storage. This is typically done using a vacuum dryer and vacuum pump. The dried oil is then pumped to storage.
The press cake from the screw press is a compact mass with high moisture content. It is fed into a paddle screw conveyor, which helps break up the compact mass. The loosened mixture of fruits and nuts is then sent to a vertical separating column, where fibers are separated from the upward airflow through a cyclone separator and collected at the bottom. The fibers obtained are reused as boiler fuel.
The heavier nuts drop to the bottom of the separating column and are directed to a rotating nut polishing drum. The polishing drum removes fiber residues attached to the nuts. The polished nuts exiting the polishing drum are taken for kernel recovery.
Polished nuts from the nut recovery section are cracked using a nut cracker/ripper mill. Winnowing technology is employed to separate dust, small shell particles, and dirt from the cracked mixture.
The remaining mixture of kernel and shell is fed into a water mixture tank and pumped using a hydrocyclone pump, where kernel and shell separation occurs. The separated kernels are sent to drying silos, and the dried kernels are bagged or taken for further extraction processing.
The palm kernel and other by-products like empty fruit bunches and palm press fibers can be utilized for various applications such as animal feed, energy production, and as organic fertilizers.
