The process of oil purification is divided into four (4) sub-processes during which the suspended matter is dissociated from the raw crude oil.
Vibrating Screen of Raw Crude Oil
Screening of raw crude oil is carried out in order to separate large size of solids such as dirt, fibres and fragments of the pericarps from the liquid phase. Water is added to the raw oil and passed through a vibrating screen in order to improve the separation process. After sieving, the oil still contains small size solids and water. Due to large surfaces of contact of oil with air, the oil quality can be affected as an oxidation process can occur.
Separation of Suspended Solids from Oil
The process is carried out to produce raw crude oil with expected composition of 90% oil and 10% water. The conventional procedure of separation of oil from water and suspended solids is the “oil separation tank” method. Oil is heated either by the introduction of steam or with closed steam heating coils which facilitates gravity separation. Depending on the applied settling tank surface loading rate and retention time, this procedure has a low-separation efficiency, which is about 50%. As a result, either the separated oil still contains a high concentration of suspended solids or the settled residue (settling tank bottom sludge) contains a high content of oil. In addition, long retention times combined with high temperature can also reduce oil quality. To improve the separation process, some mills switch from the settling tank system to a more efficient oil clarification system using a three-phase centrifuge (decanter).
The separated oil floating on top of the settling tank is then collected by a funnel system and sent to the oil purification system. The settling tank underflow is collected in the sludge tank and subsequently treated for recovery of oil.
Purification is a final process during which fine suspended solids are separated and removed from crude oil. Raw crude oil from the settling tank (top oil) is combined with recovered oil from the treatment of the settling tank underflow. This results in a total crude-oil production of about 163 kg per ton of FFB being processed.
Centrifuges carry out this final oil purification step (solids removal). For improved operation efficiency, these centrifuges are equipped with an automatic cake discharge and cleaning system. As the suspended solids content in raw crude oil is low, generated volumes of solid residues are negligible leading to a lower impact on the environment.
Oil Drying and Cooling
Due to high content of water in the purified crude oil, a treatment process referred as oil drying and cooling is required. The purified crude oil goes into a vacuum evaporation system. Subsequently, the dried crude oil is kept in storage tanks and sold to an oil refinery. This crude oil drying process-step has a lower environmental impact.
Continuous clarification tank
Continuous clarification tank clear lake containing oil enters into the oil tank, pump into centrifuge separation. The separated palm oil enters into circulating tank, and circulating pump sends it into oil clarification tank.
The separated waste oil enters into slag pit discharge, and the upper oil is recovered into circulation oil tank.