Design and development of palm fresh fruit bunch thresher for the productivity improvement of palm oil production process.

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.