The development of a residual oil recovery system to increase the revenue of a palm oil mill

The Malaysian oil palm industry is an export orientated industry which heavily relies on the world market. The Malaysian oil palm industry has shown stellar performance in 2011. The average annual price of palm oil for the year 2011 breached the RM 3000 mark to register at RM 3219, while the export revenue of palm products reached a record high of RM 80.4 billion. Since the 1980s, the judicious utilisation of the various by-products through nutrient recycling in the fields has reduced environmental impact, thus paving the way towards a zero-waste policy. Crude palm oil (CPO) is produced in the palm oil mills by mechanically extracting it from the digested mesocarp of the palm fruits. Currently, mills uses screw presses for the oil extraction process. However, mechanical methods have their limitations, as some oil will still remain in the mesocarp, even after being subjected to high pressure mechanical squeezing in the screw presses. The pressed mesocarp fibre retains about 5.0%-11.0% oil expressed as a ratio to the dry matter. This translates into an oil loss per tonne of fresh fruit bunches (FFB) in the range of 0.25%-0.55%, at an average moisture content of 36% in the pressed mesocarp fibre. In order to recover part of this residual oil in the pressed mesocarp fibre, a residual oil recovery system (RORS) was developed. This system has the ability to recover the residual oil in the pressed mesocarp fibre by using a washing technique, followed by pressing to recover CPO. Water at a certain temperature is used to wash the pressed mesocarp fibre in the digester, following which the fibre is pressed in a screw press. The water and oil expelled by the pressing operation after channeling to a vibrating screen to filter out the solid tailings are directed to an oil recovery tank situated in the mill. The recovered oil is then fed into the clarification tank or the purifier tank while the water phase is either treated for recycling or disposed. The system is found to reduce the residual oil content in the pressed mesocarp fibre to as low as 2.0% on a dry basis. This translates into 0.72% on a wet basis. The normal oil loss in pressed mesocarp fibre in the mill is 5% to 11% on a dry basis (equivalent to 1.8% to 3.96% on a wet basis). The oil extracted by RORS also depends on the amount of oil loss, and will range from 3.0% to 9.0% on a dry basis, or 1.08%-3.24% on a wet basis. This translates into 0.15% to 0.45% oil recovery per tonne of FFB. CPO that is extracted from the pressed mesocarp fibre by RORS exhibits even better oil quality than the normal CPO