Development of Rotary Drum Dryer for Oil Palm Sterilization

Abstract

In the small oil palm industry, the sterilization process consumes a lot of energy during heating. The purposes of sterilization process are to soften fruit, inactivate enzymes, reduce water content in fruit and facilitate oil extraction. During the sterilization process in conventional drying, it was found that oil palm did not heated uniformly between the top and the bottom layers of the drying chamber, and the process take about 30 hours. Therefore, the rotary drum dryer is being developed as a new device for drying oil palm, to solve problem of over-drying, to maintain good quality and accelerating the drying process. This research aims to design and develop a rotary drum dryer for oil palm sterilization. The outcome of research is to perform an important model of drying technology that can be adopted in the sterilization process in the oil palm industry for increasing sterilization process efficiency and minimizing energy consumption. The fixed parameter of this research was drying temperature in the drum at 120°C which was the same to conventional dryer whereas the variable parameters were rotation speeds varied in the range of 1.68, 4.14, and 8.34 rev/h and the number of ventilation holes of the drum varied for each side lid in the range of 9, 18 and 36 holes, respectively. Therefore, the moisture ratio (MR) of oil palm, energy consumption and CPO quality (color and FFA) of rotary drum drier compare to batch drier were evaluated in this research. Additionally, the flow behavior and heat transfer of rotary drum dryer were also studied by using Computational Fluid Dynamics (CFD). For the case of CFD, the ventilation holes were studied at various holes for each side lid namely, 6, 8, 12 and 18 holes. At 1,400 and 1,600 seconds for 12 ventilation holes showed the uniform temperature distribution for the whole inside the drum. In this study, variation of rotation speeds and ventilation holes give small effect on moisture ratio in every experimental cases. For energy consumption, rotation speed of 1.68 rev/h with ventilation hole of 36 and rotation speed of 8.34 rev/h with ventilation hole of 36 showed the lowest fuel consumption of 0.49 kgLPG per hour. For specific energy consumption value, rotation speed of 8.34 rev/h with ventilation hole of 9 shows the highest specific energy consumption (SEC) value of 9.326 MJ/kgdried palm. Whereas, batch drying presents the lowest specific energy consumption (SEC) value 4.496 MJ/kgdried palm. Moreover, for specific moisture evaporation rate value, rotation speed of 4.14 rev/h with ventilation hole of 18 represents the highest specific moisture evaporation rate (SMER) value of 2.829 MJ/kgwater removed/hour. And then, batch drying shows the lowest specific moisture evaporation rate (SMER) value of 0.501 MJ/kgwater removed/hour. For dried palm quality, at first for color appearance at rotation speed of 1.68 rev/h with ventilation hole of 36 drying period of 9 hours perform cook dried palm. At the same time, for dried palm quality of batch dryer bottom layer performed cooked palm with colorless of kernel and brownish color of mesocarp. Second, FFA percentage of rotary drum dryer has higher value than that of batch dryer. In factory, the drying process take time about 30 – 40 hours to achieved good condition of dried palm. For future, it needs to consider energy cost compared to factory. This study also suggested that velocity flow and temperature distribution with different ventilation holes and temperature variations have to be studied further.