Integrated membrane process for pretreating and desolventizing hexane-soybean oil miscella – A pilot plant study

Abstract

The study aimed to develop a membrane desolventizing technology for solvent recovery in vegetable oil extraction. Pretreatment of crude miscella is a prerequisite for an organic solvent nanofiltration (OSN) based desolventizing process. Solvent-resistant ultrafiltration (SRUF) membrane employed in micelle-enhanced ultrafiltration (MEUF) of hexane-crude soybean oil miscella displayed high phospholipids (PL) rejection (98.5%) and productivity (∼28 L/m2/h), accompanied with a moderate oil rejection (∼22%). The PL-rich retentate fraction was alkali-treated to recover the oil in the stream (8.8%). This complementary pretreatment approach met the quality requirements and maximized the yield of treated oil (>98%) while reducing the chemicals in the process. A subsequent two-stage desolventizing of MEUF-treated miscella with solvent-resistant nanofiltration (SRNF) membrane reduced the oil-in-permeate to 1.37%, achieving the set recycling criteria (<2%). The results obtained from the pilot scale study (batch size 40 kg of crude miscella) revealed that the MEUF met the pretreatment requirements, and the subsequent OSN process recovered ∼63% of hexane through a non-thermal route for recycling in the extraction process. The pilot-scale evaluation demonstrated the technical feasibility of the proposed membrane desolventizing process employing indigenous spiral-wound SRUF and SRNF membrane modules.