Membrane degumming of crude vegetable oil

Abstract

Crude vegetable oils contain various minor substances like phospholipids, coloring pigments, and free fatty acids (FFA) that may affect quality of the oil. Reduction of energy costs and waste disposal are major concerns for many oil refiners who are looking for alternative methods to improve conventional refining methods. During the last decade, energy efficient membrane separation technology has evolved dramatically. This thesis reports a study on degumming crude vegetable oil using membrane separation. In the bench-scale study, two membranes were evaluated for their flux and rejection properties. Process parameters including pressure, temperature, feed velocity and volumetric concentration factor were examined. A 99.6% rejection of phospholipids and a flux of 22.4 LMH were achieved at pressure 300 psi, temperature 40'C and feed velocity 220 1/hr using DS-7 membrane, and significant reduction of the coloring pigments was observed as well. In the pilot-scale study, the spiral wound DS-7 membrane was found effective for 100% rejection of phospholipids with a permeate flux of 57.6 LMH. The rejection rates of phospholipids, Mg and Ca were 100%, 99.6% and 54.6%, respectively. Resistance-in-series model of the membrane system was also studied. The membrane resistance, the fouling resistance, and the polarization resistance for the pilotscale system were 0.29, 0.043, and 4.49, respectively. Evaluation on membrane fouling and cleaning showed that flux decreased rapidly during the first several hours and membrane cleaning presented no significant problem. The pilot-scale study confirmed results of the bench-scale system and provides useful data for commercializing membrane refining process in the near future. KEY WORDS: Membrane separation, crude vegetable oil, degumming, phospholipids.