IV
ABSTRAK
Tandan kosong kelapa sawit (EFB) sebagai bahan mentah buangan pejal amat
berpotensi digunakan untuk pelbagai industri seperti industri papan gentian, tilam dan
kusyen, pengawal hakisan, pengisi plastik tenno, pembuatan kertas, kawalan akustik,
penebat bunyi dan makanan haiwan. Keadaan operasi yang sesuai di dalam proses
pengeringan diperlukan untuk mendapatkan gentian EFB berkualiti tinggi. Pengering
tong berputar menggunakan bahantara pengeringan udara parIas telah digunakan
secara konvensional untuk mengeringkan gentian tandan kosong. Walaubagaimana
pun sistem pengering ini telah menemui masalah seperti gentian berpintal, kehitaman
gentian dan persentuhan tak
sekata antara udara panas
dan
gentian
yang
mengakibatkan kandungan lembaban produk tidak seragam. Untuk mengatasi masalah
tersebut, pada penyelidikan ini stirn panas lampau digunakan sebagai bahantara
pengeringan bagi pengeringan EFB. Pengeringan ini dijalankan pada julat suhu stirn
lIS-220°C, tekanan atmosfera, julat halaju stirn pennukaan 0.35-0.49
mis,
julat jarak
di antara muncung stirn ke pennukaan bahan 50-200 rom, dan piring berlubang
dengan saiz lubang antara 16-200 mesh. Penyelidikan ini menggunakan kandungan
kelembapan awal gentian dalam julat 0.96-1.46 gig asas kering. Perubahan berat
bahan pada setiap masa sewaktu proses pengeringan telah diukur menggunakan
kaedah penimbangan berselang. Kaitan di antara perubahan jisim dan
parameter-parameter uji kaji dihuraikan melalui nilai kandungan lembaban keseimbangan,
kinetik pengeringan dan lengkung pengeringan cirian, Dalam julat 115 - 220°C dan
tekanan atmosfera, nilai kandungan lembapan keseimbangan didapati mengikut
persamaan eksponen. Dengan menggunakan pakej SAS versi 6.12, nilai pekali k
=16.970, n
=
-0.005, dan nilai indeks kuasa m
=
1.466. Bagi penyingkiran lembapan
yang maksimum, suhu dan halaju stirn optimum ialah masing-masing 140°C dan 0.40
mls. Penyelidikan ini menunjukkan bahawa kesan halaju stirn adalah lebih kuat
daripada kesan suhu stirn dalam penurunan kandungan lembaban disebabkan oleh
kekuatan hentaman stirn pada pennukaan gentian melepaskan air yang tidak terikat di
dalam gentian. Lengkung pengeringan cirian gentian menunjukkan bahawa tidak ada
kala kadar pengeringan malar pada suhu lebih tinggi daripada 115°C. Penyelidikan ini
juga mendapati perubahan kandungan lembapan dipengaruhi oleh jarak keluaran stirn
ke pennukaan bahan, Keputusan menunjukkan bahawa jarak keluaran stirn yang
sesuai adalah 150 rom. Jaring bersaiz mesh 50 sesuai bagi piring bekas pengeringan
bahan pada keadaan operasi optimum iaitu pada suhu 140°C, halaju stirn 0.40 mls dan
jarak keluaran 150 mm. Bagi jaring piring bersaiz mesh 200, masa yang diperlukan
untuk mencapai keseimbangan adalah lebih lama disebabkan berlaku pemindahan
jisim wap air melalui dua mekanisme iaitu melalui mekanisme santakan dan
mekanisme telus. Pengeringan telus stirn panas lampau dapat mengurangkan
kandungan 1embaban sehingga 100% da1am tempoh 15 minit tanpa kondensasi.
Persamaan model matematik kajian ini boleh mewakili peristiwa pengeringan
keseluruhan, dan memi1iki kejituan yang tinggi. Di dalam kajian kua1iti, meter
testometric tensile
digunakan untuk menunjukkan hasil gentian mempunyai kekuatan
fizikal yang tinggi. Penggunaan kromameter pula menunjukkan wama hasil gentian
adalah lebih cerah. Mikrostruktur pennukaan gentian
yang didapati dengan
menggunakan mikroskopi pengimbas elektron (SEM), tidak berubah dengan kenaikan
suhu, tetapi pada ha1aju stirn tertentu mikrostruktur permukaan didapati berubah.
v
DRYING OF OIL PALM EMPTY FRUIT BUNCHES FIBRE THROUGH
DRYING SYSTEM USING SUPERHEATED STEAM
ABSTRACT
Empty fuit bunches (EFB) as a solid waste raw material has great potential to be used
in various industries such as in fiber board, matress and cushion, erosion controller,
thermoplastic filler, paper, acoustics control, sound insulator and animal feed meal
industries.
An
appropriate operational condition in drying process is required to obtain
a high quality EFB fiber. A rotary drum dryer with hot air drying medium has been
conventionally used to dry fibres. However this drying system suffers from tangled
fiber, fiber darkening and uneven contact between hot air and fiber that may cause non
uniformity in moisture content of product. To overcome this constraint, the present
work applied superheated steam as the drying media for EFB drying. The drying
experiment were carried out at a temperature range of lIS-220°C, atmospheric
pressure, a range of steam superficial velocity from 0.35 - 0.49 mis, a range of
distance from steam nozzle to EFB from 50-200 mm and a 16-200 mesh perforated
plate. This investigation used initial fiber moisture content in the range of 0.96-1.46
dry
basis. The change in mass of EFB during the drying process was periodically
measured by a stepwise method. The correlation between the change in mass and
experimental parameters is described by the equilibrium moisture content, drying
kinetics and drying characteristics.
In
the temperature range of lIS-220°C and
atmospheric pressure, the equilibrium moisture content value is found to follow an
exponential equation. By using a statistical package of verso 6.12 SAS it has been
found to have coefficient k
=
16.970, n
=
-0.005 and power index m
=
1.466.
It
was
found that for maximum moisture removal, the optimum temperature and steam
superficial velocity is 140°C and 0.40 mls respectively. This investigation shows that
the effect of steam velocity is stronger than that of steam temperature in decreasing
the moisture content that is caused by the strong steam impact onto the material
surface releasing the unbound water. The fiber drying characteristics curve shows that
there is no constant drying rate period at higher than 115°C. This study also found that
the moisture content change was also affected by the steam output distance onto
material. The result showed that the appropriate steam output distance was found to be
150 mm. Regarding the effect of perforated plate, this investigation found that a 50
mesh value is appropriate for the optimum operational condition. at temperature
140°C, steam superficial velocity 0.40 mls and steam output distance 150 mm. For
perforated plate of 200 mesh, the time required for gaining equilibrium condition has
been found to be longer since a mass transfer of water vapor has been occurred in both
through and impingement drying mechanism. The superheated steam through drying
system can successfully reduce the moisture content by almost 100
%
in 15 minutes,
and is also capable of preventing steam condensation during the drying process. The
mathematical modeling equations found in this study can represent the whole drying
process, and possess high accuracy. During quality tests using a testometric tensile
meter, the fiber product shows higher physical strength than fibers dried in the
conventional way. By using a chromameter, the fiber product is also found to be
brighter than fibers dried in the conventional way. The microstructure of the fiber
surface obtained by usingr the scanning electron microscope (SEM), does not change
with
increasing steam temperature, but
at certain steam velocity a change in
microstructure was observed.
