Malaysia and Indonesia are the largest producers of palm oil product. The palm oil industry has contributed the biggest income to the countries for many years. Moreover, palm oils has emerged as one of the most important oils in the worlds oils and the market of fats. About 90% of palm oil is used as food related products worldwide, and the other 10% is used for basic raw material for soap. There are more than a hundred palm oil processing mills in the two countries. As such, a lot of savings can be done by using the fiber and shell from the processing wastes as an alternative fuel for electricity generation for this industry. This paper deals with energy conversion from the fiber and shell of the industry wastes as an alternative energy source for the palm oil mill industry in the two countries mentioned. The study concentrates on using the fiber and shell obtained from the processing of palm oil as fuels for the boiler instead of fossil fuel. In addition, the possibility of excess air and fuel air ratio for the fiber and shell combustion process is also discussed. Furthermore, it has been found that the shell and fiber alone can supply more steam and electricity than is required. Some palm oil mills in Malaysia and Indonesia have applied this strategy successfully. The FELDA palm oil mill, with the capacity 30±60 tons FFB/h, in Sungai Tengi, Selangor, Malaysia has been selected for this research.
The worlds demand for energy grows rapidly, and therefore, the time has come to look for alternative sources of energy, such as renewable energy, to replace the rapidly depleting supply of fossil fuel. Producing energy from renewable oil palm wastes can contribute to avoiding the use of fossil fuel for this industry. Palm oil has been one of the success stories of the Malaysian and Indonesian agricultural sector. From the early 1920s the palm oil industry has developed rapidly, especially in the years 1960±2000. Although Malaysia is moving towards heavy industrialization, the agriculturally based industries, such as palm oil industries, would remain at present. In Indonesia, after the economic turmoil in July 1997, the country has changed government policy from industrial to agricultural in order to return the economy to the right track. For the last three years, many giant palm oil plantations and processing industries have been developed in the islands of Sumatra, Kalimantan and Sulawesi.
The oil palm is grown for its oils. Palm oil is extracted from the mesocarp and kernel of the matured fruits on the FFB. An oil palm starts to produce three years after field planting. The production increases to a maximum in the first 10 years and usually tends to decline slowly thereafter. With the present plant, FFB yields are usually more than 25 tons/ha/year. Presently, there are more than 1.46 million hectares of land under palm oil cultivation, which produce 4.13 million tons of palm oil per year. In other words, a total of more than 19.7 million tons FFB were processed per year.
Palm oil mill process
Research shows that all the palm oil mills in Malaysia and Indonesia use small boilers for electricity generation and the palm oil extraction processes. The common type of power plant used is a small water tube boiler. The boiler is a standard open D-type boiler, which is accessible to use any type of fuel with a few modifications. This type of boiler is able to process 30±60 tons FFB/h. Some primary palm oil mill processes are explained in the following section.
Sterilization
When the fruit bunches are cut from an oil palm and stored for several days, much of the fruit loosens naturally and may be shaken or knocked off the bunches. If the fruits were simply pounded in a mortar and pressed cold, an oil having a very high FFA content would be obtained. This would happen because the fat splitting enzymes present in the pericarp would remain active and would hydrolyze much of the oil when the fruit was pulped in the mortar. The oil yield obtained on pressing would be very small.
It would be possible to avoid such a rise in FFA during the pulping process and obtain high oil yield from naturally stripped fruit. This fruit must be cooked before being digested and pressed. Both processes can be done using steam above atmospheric pressure. The pressure vessel used for cooking palm fruit with steam is known as a sterilizer and the process as sterilization.
Stripping
The objective of stripping is to separate the sterilized fruits from the sterilized bunch stalks.
Digestion
After the bunches have been stripped, the sterilized fruit, together with the accompanying calyx leaves, must be reheated and the pericarp loosened from the nuts and prepared for pressing. This is performed in steam heated vessels with stirring arms, known as digesters or kettles.
Oil extraction
The most usual method of extracting oil from the digested palm fruit is by pressing. The type of press used in this palm oil is the screw type press.
Clarification
The crude oil extracted from the digested palm fruit by pressing contains varying amounts of water, together with impurities consisting of vegetable matter, some of which is in the form of insoluble solid and some of which is dissolved in the water. The water present in the crude palm oil can largely be removed by settling or centrifuging, since most of it is free or undissolved. A small proportion of it, however, is dissolved in the oil and this can only be removed by evaporation in the dehydrator with or without the assistance of vacuum.
Nut / fiber separation
When the digested fruit is pressed to extract the oil, a cake made up of nuts and fiber is produced. The composition of this cake varies considerably, being dependent on the type of fruit. The cake is given a preliminary breaking treatment before being fed into the nut / fiber separator that may bring about separation by mechanical means or by the use of an air stream.
Kernel extraction and drying
When the fiber has been separated from the nuts, the latter can then be prepared for crack- ing and cracked. Any uncracked nuts must be removed and recycled and the shell separated from the kernels. The kernels must then be dried and cleaned, if necessary, before being bagged.
Biomass fuel from fresh fruit bunch
The FELDA palm oil mill in Sungai Tengi, Selangor, Malaysia, has been selected for the analysis. The capacity of a palm oil mill is desined as the rate of processing FFB in terms of tons per hour. The capacity of a large scale mill ranges from 10 to 60 tons FFB/h. The palm oil mill used for this study has a capacity of 30±60 tons FFB/h in two boilers. Each boiler can produce about 4200 kg of fiber and 1800 kg of shell per hour. This boiler has been designed with a maximum continuous rating of 18,780 kg/h, superheater outlet pressure at 22 bar and steam temperature at 250°C.
The biomass from FFB as fuels for the boiler can be classified as:
1. fiber
2. shell,
3. empty fruit bunches (EFB),
4. palm oil mill effluent (POME).
From the processing of 1 ton of FFB/h the mill produces 140 kg of fiber and 60 kg of shell per hour. Therefore, for the 30 tons FFB/h mill, it produces 4200 kg of fiber and 1800 kg of shell per hour.
Energy conversion from palm wastes
The calculation is based on a mill with a capacity of 30 tons FFB/h. For potential energy conversion calculation, it is sufficient to consider only the fiber and shell, since the EFB has to be shredded and dehydrated in order to render it more easily combustible, and this will only increase the cost for pretreatment. Therefore, it will not be considered for fuel. The fuel is only comprised of 6% shell and 14% fiber with an average density of 1.02 kg/m.
Electricity requirement of a palm oil mill
The electrical energy required to process 1 ton of FFB is about 20 kW h. According to the calculation, there is more than sufficient steam to generate electricity for the milling processes, and the exhaust steam from the boiler can also be used for the FFB sterilization.
Conclusions
As tropical countries, Malaysia and Indonesia are considered to be very fortunate because of having palm oil plantations. Besides re-planting of burned rain forests, the plantation also offers many jobs for unskilled workers in the countries. In the energy point of view, the advantage of the palm oil industry is that the fiber and shell can be conveniently used as fuel for the steam boiler which is the heart of a palm oil mill. This energy is considered as free for the palm oil milling process. The calculation has shown that the shell and fiber alone can generate more than enough energy to meet the energy demand of the palm oil mill. Another advantage of using the fiber and shell as a boiler fuel is that it helps to dispose of these bulky materials which otherwise would contribute to environmental pollution. The ash from the combustion process is also found suit- able for fertilizer for the palm oil plantation.
source: Mahlia, T. M. I., Abdulmuin, M. Z., Alamsyah, T. M. I., Mukhlishien, D., (2001) An alternative energy source from palm wastes industry for Malaysia and Indonesia
