Optimization of pressed palm mesocarp fiber residue oil hexane extraction plant

Abstract

Operating hexane extraction plant to recover residue oil from pressed palm mesocarp fiber (PPMF) is one of the efforts done by oil palm millers in Malaysia and Indonesia in order to improve their overall oil extraction efficiency. Recovery is done in hexane extraction plant which consists of an extractor to extract residue oil from PPMF and distillation station to separate mixture of oil and hexane after the extraction process. However, oil yield of this plant is low whereby only up to 70 % of the available residual oil could be recovered. Besides, there is also a significant volume of hexane loss during distillation. Thus, an effort was made to optimize a commercial size hexane extraction plant to optimize its oil recovery with minimal hexane loss and least effect to oil quality and nutrient contents. The optimizations were done in phases whereby Phase 1 focused on optimization of extraction process by varying the extractor speed, hexane temperature and hexane flowrate and Phase 2 focused on optimizing the distillation process by varying flash evaporators, oil scrubber and oil dryer’s temperature and pressure. Response surface methodology was used to optimize the extraction process with the experiments designed using Design Expert software. ANOVA shows p-value < 0.011 confirming the experiment model while all selected experiments factors were also found to be significant towards oil yield. The optimum condition for extraction process was 20 Hz extractor speed, 14 m3/hr hexane flowrate and 60 °C hexane temperature. Distillation process optimization was done using Aspen Plus software which was also cross-checked with actual running plant. The optimum condition for distillation process was as follows: Flash evaporator no. 1 at 80 °C and 380 mm Hg; Flash evaporator no. 2 at 130 °C and 420 mm Hg; Flash evaporator no. 3 at 148 °C and 510 mm Hg; Oil scrubber at 120 °C and 590 mm Hg; Oil dryer at 80 °C and 640 mm Hg. The above exercise resulted in increase of overall oil extraction efficiency by 18.8 % with no effect on hexane loss, oil quality and nutrient content. The improvement if expressed in monetary value translates to an additional income of RM 33,725 per month for the plant involved.