ABSTRACT
Vegetable oil processing has been identified as one of the potential nonaqueous applications of membrane technology. Membrane-based processing has been largely attempted on individual steps of the conventional refining process with reasonable success. With the advent of organic-solvent-nanofiltration, membrane desolventizing of hexane oil miscella has received greater attention, revitalizing the prospects of integrated membrane processing. A practical evaluation of membrane augmented desolventizing revealed that approximately 65% energy savings towards solvent evaporation could be achieved in an industrial environment. Further, a pragmatic appraisal advocated that an integrated membrane process with a focus on pretreatment and desolventizing along with physical refining would be a desirable approach for fortifying the benefits. The present review intends to channelize the efforts to overcome the current limitations and highlights the importance of developing better membranes, process evaluation under appropriate practical conditions, and developing suitable cleaning protocols for stable performance. In the case of alternate solvents to hexane, membrane solvent recovery would be a favorable approach to overcome the limitation of associated higher thermal energy requirements. Nevertheless, solvent selection should be based on a composite evaluation of extraction and membrane desolventizing, specific to the type of oil. Finally, a comprehensive process scheme has been proposed to realize the benefits in extraction-refining plants. In this direction, a few pilot demonstration plants need to be established and operated for 1-2 years to understand and overcome the practical difficulties and limitations of the technology, leading to its industrial adoption.
