The Extraction of Palm oil
This introductory article gives a brief description of the process of extracting palm oil in a modern factory. Detail descriptions are contained in other articles found at this site. A typical process flow diagram is included. Pictures are included in this article to make thing clearer to people unfamiliar to the oil Palm industry.
Palm oil factories are normally generate their own electricity. Electricity is generated by burning the waste products of the fruits, fibre and shell in a boiler. The boiler generates steam which drives a steam turbine to produce electricity. Palm oil mills are located in plantations that are far away from major towns and as such they also treat their own water supply.
The extraction process is a series of separating processes. These are described below.
Palm oil is extracted from oil palm fruits. Oil palm trees grow in the tropics and originated in Africa. The fruit bunch is cut when it is ripe as shown in the picture. The harvested fruit bunches are sent the processing plants by trucks for the extraction of Palm Oil.
The arriving fruit usually in trucks is dumped into a FFB (Fresh Fruit Bunch) hopper. It is then transferred to fruit cages. The cages are then moved into a steriliser.
The steriliser is similar in function of a pressure cooker. The fruits are heated with steam at a pressure of 45 psig for about one hour. This cooking process softens the fruits, enables the separation of the fruit from bunches and stops the enzymes that cause the increase of FFA (Free fatty acids) in the fruits.
In the next stage the fruit cages are tipped and conveyed to a threshing machine. This machine a rotary drum of about 2 meters in diameter. The drum rotates and bunches get lifted up and dropped when they reach the top of the drum. This action helps the detachment of fruits from the bunches and the separated fruit lets fall through the slots of the drum to a conveyor below.
The fruits are conveyed to a digester which mashes up the fruitlets so that when the mash is pressed in a screw press the oil is extracted efficiently. The out put from the screw press is crude palm oil and press cake. The extracted oil is mixed with fruit particles, water, sand and dirt. The press cake consists of palm fibre and nuts.
The press cake is the transferred to the depericarpper 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 oil is pumped to a heated vertical tank where the separation of oil from the sludge (mixture of water and dirt) takes place by gravity. The oil is skimmed from the top and the remaining dirt removed in a purifier. The heated clean oil is the passed to a vacuum chamber for the removal of the remaining moisture. The oil is the pumped to storage tanks for sale as crude palm oil.
Press Cake processing.
The press cake is conveyed in a conveyor that helps break up the cake to a depericarper. The depericarper is a square box that with a strong suction. The air removes the fibres and transports them to a cyclone. The fibre from the cyclone is sent to the boiler for burning as fuel for the generation of steam.
The nuts being heavier drop to the bottom of the depericarper and are cleaned in a rotary drum and transported to a silo for intermediate storage.
The nuts from the nut silo are first cracked in a nut cracker. The cracked mixture which consists of kernels and shell is the processed to separate the shells and kernels. This is done in air columns and by a water bath in a hydro-cyclone. The shell is sent to the boiler house to be used as fuel. The kernels are dried in a silo and then packed in bags for sale. Other factories extract oil from the kernel.
In a palm oil mill all the electricity required for processing can be generated from the waste products of the palm fruits. The diesel generators are only required for start up and shut done of processing in a well operated palm oil mill.
The fibre from the fruits after pressing and shell from cracked nuts are sent to the boiler for burning as fuel. The steam generated by the boiler is used to drive a steam turbine which is coupled to an alternator to generate electricity. In new mills with with efficient design additional electricity can be produced for external use.
In the palm oil mill process water is required for the steam generation, oil clarification, cleaning and domestic requirements. The quantity of water required is determined by the processing capacity of the mill. 30 tons per hour mill will require 30 cubic meters of water per hour. Most palm oil mills are located in plantations that are far away from towns. This requires most palm oil mill to treat their water requirements. The treatment plants purify the water for process use and then further treat it for use in the boilers.
The palm oil process uses water to separate the oil from sludge and solids in a tank. After the removal of oil, the waste water (effluent) is discharged from the mill. This effluent contains particles of vegetable matter and needs to be treated before discharge to the environment. The effluent needs to be treated because the vegetable matter in the liquid will decompose and during the decomposition process, the vegetable matter will use oxygen in the water. Therefore before the discharge of the effluent to a water course we let the decomposing process take place by keeping the effluent in ponds and let bacteria decompose the vegetable matter in the waste water.
This then is a simple explanation of the palm oil process.