Minimizing water consumption in oil palm sterilization using direct steaming: Effects of sterilization pressure and time

Abstract

In a palm oil mill, Fresh Fruit Bunches (FFB) must undergo sterilization before oil extraction. In a conventional industrial sterilization system, a boiler and a sterilizer performing the steaming are separated but connected with piping. This process consumes a very large amount of water. The specific water consumption of a conventional sterilizer is 0.256 kg-water/kg-FFB. In order to minimize water consumption by eliminating piping and continuous heating to maintain specific sterilization conditions, in an integrated design, the boiler and the sterilizer would be combined into one unit. Therefore, this work studies combining the boiler and the sterilizer into one unit. FFB were sterilized in a mini sterilizer by direct steaming at 0.5, 1.5, 2.5, or 3.5 bars for 30, 45, 60, or 75 min. The results show that the sterilization time, especially in the range of 30–45 min, affects fruit-bunch separation more than the choice of pressure. The optimal conditions for good fruit-bunch separation with acceptable free fatty acid (FFA) and Deterioration of Bleachability Index (DOBI) of crude palm oil (CPO) standard, as well as low water consumption, was 2.5 bars and 60 min. At this operating point, the specific water consumption was 0.0587 kg-water/kg-FFB, which is about 4.34 times less than the conventional consumption. An empirical correlation of specific water consumption is reported for these operating conditions. • Novel method of FFB sterilization by direct steaming was reported. • Water consumption of direct steaming was 4 times less than that of a conventional sterilizer. • An empirical correlation of specific water consumption was constructed.