History of Oil Palm
The oil palm ELAEIS GUINEENSIS grows around the globe in a zone of 10 degrees latitude to the north and south of the equator. Its utilization as basic nourishment had always been of vital importance to the inhabitants of this equatorial regions and its existence is reported as long as 3000 BC, when palm oil was known to the Egyptians under Pharaoh’s reign.
The Oil Palm originates from Africa where there is a wealth of oil palm genetic material. The natives of Guinea coast who had made a living by raiding for slaves, were induced to find a new occupation in processing and selling the oil for export; for through the trade in palm oil firmly established before 1850.
The Palm Oil Milling Process
The palm oil mills mainly involve the following processes:
a. Fruit reception and preparation,
b. Sterilization,
c. Threshing,
d. Digestion,
e. Pressing,
f. Oil clarification and
g. Nut processing.
The palm oil mills have their own facilities for power generation, water treatment and palm oil mill effluent (POME) treatment. The palm oil fibres and the palm kernel shells are the main fuels used in the furnace to generate steam and power in the cogeneration system. The furnace is typically a fixed grate combustion system which is low in combustion efficiency. The cogeneration system commonly uses the back pressure turbine which is low in overall process efficiency.
The Fresh Fruit bunches (FFB) are transported to the mill and loaded into cages or FFB feed conveyors and sterilized for about 1.5 hrs using saturated steam at a pressure of 3 bar(g). The sterilisation process retards the enzymatic activity that would otherwise lead to formation of free fatty acids, as well as cooks the fruit bunches allowing the fruitlets to detach easily. The bunches are then tipped and conveyed to a thresher where the fruitlets are stripped from the bunches.
The process consumes huge amount of water and produces high organic content of POME. It is estimated that the amount of POME generated is about 68% by weight of the processed FFB. The POME needs to be treated and comply with the DOE regulations before it can be discharged to the environment. Digested solids effluent and biogas were produced during the treatment process. Currently the solids and the treated POME are pumped to the oil palm plantations as fertilizer. In some mills, decanters have been incorporated in the process to extract the remnant oil in the clarifier sludge. The decanters extract part of the solids in the sludge and these solids account for about 8% by weight to FFB.
The press cake, the residues from the oil extraction in the screw press, comprises mainly of fibre and nuts. These are separated in a winnowing system and the fibre conveyed on to a storage platform for use as boiler fuel. The nuts are polished, cracked and the palm kernel shells extracted, dried, and stored in bulk silos. These are the main by-products of the palm oil milling process.
Steam and Power Generation
Utilization of existing energy resources is indispensable not only for large industrial processes but also for small production plant and in particular oil palm mills where the balance between heat and power are required for production process which are pre-condition for a ‘Combined Heat and Power (CHP) scheme’, or commonly referred to as Co- Generation System. Solid waste fuel in the form of shell, fibre and empty bunches which are by-products of the process are utilized as fuel for the boiler.
Steam is required for processing at the approximate rate of 500kg per hour. This steam can be easily raised in a reasonably efficient water tube boiler with fuel available from the fibre, shell and empty bunch. Power is required at the approximate rate of 15 to 25 kW per ton FFB. This can be easily be provided by placing a back-pressure single stage steam turbine between the boiler and the header of the mill processing system. Steam is generated from the boiler at a pressure of say 20 bar g and into the steam turbo alternator at 18.5 bar g at 260ºC with back pressure of 3.16 bar g for the mill process which is convenient and effective for process heating.
Every ton of FFB can produce 733 kg steam and 30 kW power. A system has been introduced for the treatment and disposal of empty bunches and recovery of palm oil and at the same instance reduces the moisture contents of the empty bunches to approx 45 % so that they can be used as solid waste fuel for the boiler and production of additional steam and electrical power.
Empty Fruit Components
General
1. Yield 19 - 23 % to Fresh Fruit Bunches
2. Oil Content 2 - 4 % Empty Fruit Bunchs
3. Moisture Content 65 - 70 % Empty Fruit Bunchs
4. Non-oil Solids 28 - 35 % Empty Fruit Bunchs
5. Nett Calorific Value 8,164 kJ/kg
6. Ash Content 4 - 6 % Empty Fruit Bunchs
7. Volatile Matter (0% Moisture) 87.04 % Empty Fruit Bunchs
8. Carbon (0% Moisture) 45.9 % Empty Fruit Bunchs
Trace elements
Al - 1.01% B - 3.75% Ca - 0.59% Cd - 0.00% Cr - 0.02% Fe - 0.20% K - 5.91% Mg - 0.23% Na - 1.83% P - 0.08% Pb - 0.01% S - 0.15% Si - 86.17% Ti - 0.15%. All the elements was analysed at 0% moisture content.
Dry matter composition
Lignin - 20 to 25 % Hollocellulose - 56 to 68 % Ash Content - 5%
