Abstract:
In conventional palm oil production process, fresh palm fruit bunches are sterilized before
mechanical threshing to get rid of lipophilic microbes and soften the fruits pulp for easy stripping.
The sterilization is executed at 130 °C-160 °C temperature and elevated pressure 0.15 - 0.4 MPa
for about 60-90 minute. Steaming the entire bunch followed by conventional threshing
necessitates large-capacity steam generators, bulky storage bins, and heavy machinery for
threshing. The sand and impurities carried with the whole bunch can cause cavitation in the
machinery and degrade the quality of the oil. As an alternative, this study proposed separation of
palm fruits from the bunch and sterilize only the fruits to reduce the total sterilizing mass. The
developed thresher includes 2.13m × 3m × 1m holding frame, half ellipsoidal shape loading rack
and a rotary threshing spindle with 10mm carbon steel wire loop as the threshing elements. The
machine was powered by 12Hp diesel engine with the ideal running speed of 2000 rpm. The
speed was reduced to 860 rpm to run the spindle by using 6 inches driving pulley and a 14 inches
diameters driven pulley. The threshing elements were fixed to the spindle with 40 ̊ angle to the
rotating plane. The best shape and its angle of orientation, best element height from the holding
rack, best spindle RPM were quantified by the trial-and-error method. Results show that the
triangle shape smooth edge element with 40˚ angle orientation gave the maximum speed of
threshing. The best element height from the loading track was 2 inch and gave a significant
improvement of threshing to the other heights. The invented thresher was found to be
accomplished 3.8TPH rate, which is more than double to the existing machine speed reported as
1.5TPH. The manufacturing cost including the skilled labour was 2600USD via the same capacity
thresher is valued at 5000USD. The invented thresher and the proposed methodology have
successfully demonstrated that the novel procedure is capable of avoiding the conventional bulk
sterilization process and increases the overall process productivity by saving labour, time, energy
and increasing the quality of overall crude palm oil production process.
