2011 International Conference on Alternative Energy in Developing Countries and Emerging Economies
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threefold lower molar ratio of methanol to fatty acids
could be used, which resulted in high biofuel yields of
95
–
97%, regardless of the initial material. In addition to
accelerating biofuel production, ultrasound can be used to
monitor the biofuel production process [4].
Nowadays, typical processing of biodiesel uses oil and
alcohol as main reactants. Normal short chain alcohol
used is methanol because of highest activity and low cost.
Anyway the disadvantages of methanol are less solubility
with oil and its toxicity. This research is focused on
substitution of methanol by ethanol because local supply
capacity of ethanol has increased; consequently its price
has lowered. Not only can we reduce methanol import,
but also ethyl ester is fully natural recycle energy.
This research is aimed to determine the optimal
condition for the pretreatment steps of ethyl ester
production by using CPO as raw material. The
pretreatment steps will consist of degumming and acid
catalyzed esterification steps by performing the
continuous process. The degumming has an objective to
reduce phosphorus content. The esterification has an
objective to reduce free fatty acid (FFA) to optimal level
for further alkali catalyzed transesterification. This
esterification will be conducted by assisting of high
intensity ultrasonic system.
III. M
ATERIALS AND
M
ETHODS
A. Raw Material and Chemicals
Commercial CPO (5% wt/wt of FFA) was purchased
from local palm oil mill suppliers used as feed for the
experiments. Both 99.5% wt/wt ethanol (C
2
H
5
OH) and 98%
wt/wt sulfuric acid (H
2
SO
4
) are commercial grade and
supply by local distributors.
B. Equipment
Ultrasonic processor; Model UP400S, 24 kHz,
Hielscher Germany including with a 22 mm.diameter
sonotrode was used as ultrasound generator. It can be
adjusted the amplitude in percentage of a maximum full
range of 100 micrometer and has acoustic power density
of 85 W/cm
2
and maximum submerged depth at 45 mm.
A cooling bath controlled with thermostat was provided
from Scientific Equipment Center, PSU, Songkhla,
Thailand. A water bath together with circulated pump
was used as temperature controlling system. A 400-mL
glass bottle with sealed plastic lid which has ID 60 mm.
and length of 155 mm. was used as an esterification
reactor. An attachment between sonotrode and the glass
reactor is sealed with synthetic rubber o-ring in order to
prevent any gas leakage. Temperature monitoring was
carried out by using digital thermometer, Templog; 8
channels Temperature Data Logger version 1.0 purchased
from Scientific Equipment Center, PSU, Songkhla,
Thailand. The thermo-probe was dipped in to the reaction
solution. The experiment equipment was set up as an
experiment schematic diagram below.
Fig. 1. The experiment schematic diagram.
C. Methodology
Design of experiment was constructed by using a
Taguchi method [3]. There were two stages, the first was
preliminary evaluate by randomly selected 5 factors at 4
levels each (table I) and second was modified by
considering results of the first one. For the first one, we
would get L
16
(4
5
) orthogonal array, corresponding with 16
runs showed in table III. The second one was finally
defined 5 re-ordered significant factors including
additional two interaction factors i.e. AxC and AxD at 2
levels. Then we would get L
8
(2
7
) orthogonal array,
corresponding with 8 runs showed in table IV.
TABLE
I
D
EFINITION
,
ORDER AND LEVELS OF THE FIRST STAGE FACTORS
Factors
Title
Meaning
Levels
A
% Cat.(w/w) % H
2
SO
4
by wt. of FFA
1, 2, 5, 20
B
% Amp.
% Amplitude of acoustic power
35, 55, 75,100
C
Molar Ratio Molar ratio of ethanol : FFA
5, 10, 20, 40
D
Temp. (C)
Reaction temperature (
°
C)
50, 60, 70, 80
E
Time (hr)
Reaction time in hour
0.5, 1, 2, 4
TABLE
II
D
EFINITION
,
ORDER AND LEVELS OF THE SECOND STAGE FACTORS
Factors
Title
Meaning
Levels
A
% Cat.(w/w) % H
2
SO
4
by wt. of FFA
30, 60
B
Time (hr)
Reaction time in hour
1, 2
C
Temp. (C)
Reaction temperature (
°
C)
60, 80
D
Molar Ratio Molar ratio of ethanol :FFA
20, 30
E
% Amp.
% Amplitude of acoustic power 35, 75
The esterification reactions were carried out in the
glass reactor which placed in a circulated water bath. The
sonotrode was dipped into the reaction solution at 20 mm.
of submerged depth. Reaction temperature was controlled
UP400S
Ultrasonic
Processor
Sonotrode
Glass
Reactor
Cooling
Bath
Thermometer
Probe
Cooling
Bath
Water
Pump
60.
Digital
Therm
ometer
Water
outlet
Water
inlet
O-ring
