an alternative energy source from palm wasts industry for malaysia and indonesia

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An alternative energy source from palm wastes industry for

Malaysia and Indonesia

T.M.I. Mahlia a,*, M.Z. Abdulmuin a, T.M.I. Alamsyah b, D. Mukhlishien c

a Department of Mechanical Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysiab Department of Mechanical Engineering, University of Syiah Kuala, 23111 Darussalam, Banda Aceh, Indonesiac Department of Chemical Engineering, University of Syiah Kuala, 23111 Darussalam, Banda Aceh, Indonesia

Received 12 July 2000; accepted 6 December 2000

Abstract

Malaysia and Indonesia are the largest producers of palm oil product. The palm oil industry has con-

tributed 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

ber and shell from the processing wastes as an alternative fuel for electricity generation for this industry.This paper deals with energy conversion from the ber 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 ber 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 ber and shell combustion process is also

discussed. Furthermore, it has been found that the shell and ber 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 3060 tons FFB/h, in Sungai Tengi, Selangor,

Malaysia has been selected for this research. 2001 Elsevier Science Ltd. All rights reserved.

Keywords: Energy conversion; Alternative energy sources; Biomass fuel

Energy Conversion and Management 42 (2001) 21092118

www.elsevier.com/locate/enconman

* Corresponding author. Tel.: +60-3-759-5283; fax: +60-3-759-5317.

E-mail address: [email protected] (T.M.I. Mahlia).

0196-8904/01/$ - see front matter

2001 Elsevier Science Ltd. All rights reserved.PI I : S0196- 8904( 00) 00166- 7


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1. Introduction

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 offossil 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 andIndonesian agricultural sector. From the early 1920s the palm oil industry has developed rapidly,especially in the years 19602000. Although Malaysia is moving towards heavy industrialization,

the agriculturally based industries, such as palm oil industries, would remain at present. In In-donesia, after the economic turmoil in July 1997, the country has changed government policyfrom 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 theislands of Sumatra, Kalimantan and Sulawesi.

Nomenclature

As ashC carbonEe electricity required to process FFB (kW)Ep potential energy conversion from ber and shell (kJ/kg)Er energy to produce steam (kJ/kg)EFB empty fruit bunchFFA free fatty acid

FFB fresh fruit bunchH hydrogenHu caloric value (kJ/kg)Huf caloric value of ber (kJ/kg)

Hus caloric value of shell (kJ/kg)LHV lower heating value (kJ/kg)LHVf lower heating value of ber (kJ/kg)

LHVfs lower heating value of mixed ber and shell (kJ/kg)LHVs lower heating value of shell (kJ/kg)Mf ber production per hour (kg/h)Ms shell production per hour (kg/h)me steam required to generate electricity (kg/h)mp Steam required to process FFB (kg/h)mo potential steam obtained (kg/h)

O oxygenS sulfurwA theoretical air required per kg of fuel (kg/kgf)wF fuel (ber and shell) consumption (kg/s)gb boiler eciency (%)

2110 T.M.I. Mahlia et al. / Energy Conversion and Management 42 (2001) 21092118


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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 eld planting. Theproduction increases to a maximum in the rst 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 4.13million tons of palm oil per year. In other words, a total of more than 19.7 million tons FFB wereprocessed per year [1].

2. Palm oil mill process

Research shows that all the palm oil mills in Malaysia and Indonesia use small boilers forelectricity 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 useany type of fuel with a few modications. This type of boiler is able to process 3060 tons FFB/h.

Some primary palm oil mill processes are explained in the following section.

2.1. Sterilization

When the fruit bunches are cut from an oil palm and stored for several days, much of the fruitloosens naturally and may be shaken or knocked o 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 activeand would hydrolyze much of the oil when the fruit was pulped in the mortar. The oil yield ob-

tained 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.

2.2. Stripping

The objective of stripping is to separate the sterilized fruits from the sterilized bunch stalks.

2.3. Digestion

After the bunches have been stripped, the sterilized fruit, together with the accompanying calyxleaves, 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.

2.4. Oil extraction

The most usual method of extracting oil from the digested palm fruit is by pressing. The type ofpress used in this palm oil is the screw type press.

T.M.I. Mahlia et al. / Energy Conversion and Management 42 (2001) 21092118 2111


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2.5. Clarication

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 ofinsoluble solid and some of which is dissolved in the water. The water present in the crude palmoil can largely be removed by settling or centrifuging, since most of it is free or undissolved. Asmall proportion of it, however, is dissolved in the oil and this can only be removed by evapo-

ration in the dehydrator with or without the assistance of vacuum.

2.6. Nut/ber separation

When the digested fruit is pressed to extract the oil, a cake made up of nuts and ber is pro-

duced. 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/ber separator thatmay bring about separation by mechanical means or by the use of an air stream.

2.7. Kernel extraction and drying

When the ber 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 sepa-rated from the kernels. The kernels must then be dried and cleaned, if necessary, before being

bagged.The complete operational process and product of the palm oil mill industry are shown in Fig. 1,

and the complete ow diagrams of mass balance of 30 tons FFB/h of the palm oil mill process are

shown in Fig. 2 [1].

3. 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 dened as the rate of processing FFB in terms of tonsper hour. The capacity of a large scale mill ranges from 10 to 60 tons FFB/h. The palm oil millused for this study has a capacity of 3060 tons FFB/h in two boilers. Each boiler can produce

about 4200 kg of ber and 1800 kg of shell per hour. This boiler has been designed with amaximum continuous rating of 18,780 kg/h, superheater outlet pressure at 22 bar and steamtemperature at 250C.

The biomass from FFB as fuels for the boiler can be classied as:

1. ber,2. shell,3. empty fruit bunches (EFB),

4. palm oil mill euent (POME).



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Fig. 1. Process operation and product of palm oil mill.



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Fig. 2. Mass balance of 30 tons FFB/h mill.



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From the processing of 1 ton of FFB/h the mill produces 140 kg of ber and 60 kg of shell [2]

per hour. Therefore, for the 30 tons FFB/h mill, it produces 4200 kg of ber and 1800 kg of shellper hour.

3.1. 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 sucient to consider only the ber and shell, since the EFB has to beshredded 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 comprisedof 6% shell and 14% ber with an average density of 1.02 kg/m [1]. The chemical composition on

the dry basis of palm oil wastes is shown in Table 1 [3].Based on the chemical composition in Table 1, the gross caloric value of the ber and shell are

calculated by the Dulong formula as:

Hu 2:32114; 093C 61; 095H O=8 1

Based on Eq. (1), the gross caloric value of ber Huf is 17,422 kJ/kg, and the gross caloricvalue of 35% wet and 65% dry ber is 11,324 kJ/kg. However, the gross caloric value of shellHus is 19,462 kJ/kg, and the gross caloric value of 10% wet and 90% dry shell is 17,516 kJ/kg.

The actual fuel is comprised of 70% Fiber and 30% shell so that the lower heating value per kgof the fuels mixed can be calculated by the following formula:

LHVfs 0:7LHVf 0:3LHVs 2

Based on Eq. (2), the lower heating value per kg of the fuels mixed is about 13,182 kJ/kg, so thatthe potential energy conversion from the ber and shell for that particular palm oil mill is cal-

culated by the following formula:

Ep Mf LHVf Ms LHVs 3

Based on Eq. (3), the potential energy conversion for the 30 tons FFB/h mill, which produces 4200

kg of ber and 1800 kg of shell per hour is about 72,083,200 kJ/kg.

3.2. Electricity requirement of a palm oil mill

The electrical energy required to process 1 ton of FFB is about 20 kW h [2]. Therefore, theelectrical power required to process 30 tons FFB/h is

Table 1

Chemical composition on dry basis of palm oil wastes

Element EFB (%) Fiber (%) Shell (%)

H 6.3 6.0 6.3

C 48.8 47.2 52.4

S 0.2 0.3 0.2

N 0.2 1.4 0.6

O 36.7 36.7 37.3

Ash 7.3 8.4 3.2



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Ee 30 20 600 kW

The steam required to generate 600 kW electrical power at 30 kg/kW at 20 bars is:

me 600 30 18; 000 kg=h

The steam required to process 30 tons FFB/h at 500 kg/ton is:

mp 500 30 15; 000 kg=h

The results from Eq. (3) show that for 30 tons FFB/h mill, the potential produced energy isabout 72,083,200 kJ/kg. With a boiler eciency of 68%, therefore, the available energy to raisesteam is [1]:

Er gb Ep 0:68 72; 083; 200 49; 016; 576 kJ=kg:

The energy required to generated 1 kg of steam is about 2590 kJ [2]. Therefore, the potential steamobtained is:

mo Er=2590 49; 016; 576=2590 18; 925 kg=h

According to the above calculation, there is more than sucient steam to generate electricityfor the milling processes, and the exhaust steam from the boiler can also be used for the FFBsterilization.

4. Fiber and shell combustion processes

Because of changing the fuel in the boiler, the excess air for the ber and shell fuel has to be

identied in order to get a perfect combustion process. Excess air is necessary in the combustionprocess because it has many eects on the boiler performance. This section presents the suitable

excess air for ber and shell as an alternative fuel for the boiler. The amount of oxygen requiredfor complete combustion of a kg of a substance and the products of combustion are shown inTable 2 [4].

Table 2

Amount of oxygen required for complete combustion and products of combustionElement O2 required for

combustion of 1 kg

substance (kg)

Product of combustion

H2O (kg) CO2 (kg) SO2 (kg)

H2 8 9

C 2.67 3.67

CO 0.57 1.67

S 1 2

CH4 4 2.25 2.75



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4.1. Fiber

From the chemical composition on the dry basis of palm oil wastes in Table 1, it can be as-

sumed that 1 kg of ber contains: 0.472 kg of C, 0.060 kg of H 2, 0.003 kg of S, 0.367 kg of O2.Therefore, the amount of oxygen required to burn 0.472 kg of C is 0:472 2:67 1:26024 kg.The amount of oxygen required to burn 0.06 kg of H2 is 0:06 8 0:48 kg. The amount ofoxygen required to burn 0.003 kg of S is 0:003 1 0:003 kg. Hence, the total amount of oxygen(O2) required to burn the C, H and S in the ber is 1:26024 0:48 0:003 kg 1:74324 kg. O2already present in ber is 0.367 kg, O2 to be supplied is 1:74324 0:367 1:37624 kg. Therefore,the amount of air theoretically required is 1:37624 100=23 5:98 kg=kg fiber.

4.2. Shell

From the chemical composition on the dry basis of palm oil wastes in Table 1, it can assumedthat 1 kg of shell contains; 0.524 kg of C, 0.063 kg of H2, 0.002 kg of S, 0.373 kg of O2. Theamount of O2 required to burn 0.524 kg of C is 0:524 2:67 1:39908 kg. The amount of O2required to burn 0.063 kg of H2 is 0:063 8 0:504 kg. The amount of O2 required to burn 0.002kg of S2 is 0:002 1 0:002 kg. Therefore, the total amount of O2 required to burn the C, H2 andS in the shell is 1:39908 0:504 0:002 kg 1:90508 kg. O2 already present in the shell is 0.373kg. O2 to be supplied is 1:90508 0:373 kg 1:53208 kg. Therefore, the amount of air requiredper kg of shell is 1:53208 100=23 6:66 kg=kg of shell.

4.3. Airfuel ratio

It is found that 1 kg of FFB contains 0.14 kg of ber and 0.06 kg of shell. Therefore, 1 kg ofbulk fuel (ber and shell) contains:

fiber 0:14=0:06 0:14 0:7 kg

shell 1 0:7 0:3 kg:

Hence, the theoretical air required per kg of fuel is

wA 0:7 5:98 0:3 6:66 6:184 kg=kg of fuel

The mill is operated at 30 tons FFB/h and from the previous calculations, it is found that 1000kg of FFB contains 200 kg of fuel (140 kg of ber and 60 kg of shell). Hence, 30 tons of FFBcontains:

30 200 6000 kg of fuel:

The fuel consumption per second is wF 6000=3600 kg=s 1:67 kg of fuel=s. Therefore, the airquantity required for complete combustion is wA 6:184 kg=kg of fuel 1:67 kg of fuel=s 10:327 kg=s. The air quantity per kg of fuel with 30% excess air is wA 10:327 30=100 10:327 13:425 kg=s, therefore the air fuel ratio is wA=wF 13:425=1:67 8:039.



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5. 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 oersmany jobs for unskilled workers in the countries. In the energy point of view, the advantage of thepalm oil industry is that the ber and shell can be conveniently used as fuel for the steam boilerwhich 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 ber alone can generate more than enoughenergy to meet the energy demand of the palm oil mill. Another advantage of using the ber andshell 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.

Acknowledgements

The authors would like to thank the Malaysian Ministry of Science, Technology and Envi-

ronment for nancial support under IRPA project no. 03-02-03-0353.

References

[1] Mahlia TMI. Dynamic modeling, simulation, and experimental validation of a palm oil mill boiler. M. Eng. Sc.

Thesis, University of Malaya, Kuala Lumpur, Malaysia, 1997.[2] Ngan MA, Ong ASH. PORIM Bulletin, Kuala Lumpur, Malaysia, vol. 14. 1987. p. 10.

[3] Shai AF. PORIM Bulletin, Kuala Lumpur, Malaysia, vol. 1. 1991. p. 59.

[4] Denzel PD. Fundamentals of boiler house techniques. Hutchinson Educational, 1973.


an alternative energy source from palm wasts industry for malaysia and indonesia

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