MEMBRANE APPLICATIONS AND RESEARCH IN THE EDIBLE OIL INDUSTRY - AN ASSESSMENT

Commercial sources of edible oils and fats include oil-seeds, fruit pulps, animals and fish. Oilseeds processing typically consists of the following steps: i) seed preparation; ii) solvent extraction of flakes and/or extruded collets; iii) desolventization of the meal;iv) recovery of solvent by distillation; and v) degumming, refining, bleaching, and deodorizing of the crude oil. The process consumes large amounts of energy-in the forms of electricity, natural gas and fuel oils-to heat and cool the oil between individual processing steps and to generate high vacuum. Steam requirements for producing edible oil from crude oil range from 2000 to 4000 Btu/lb depending on the type of oil processed. The processing of cottonseed, corn, peanut and soybean oils alone consumes approximately 64.7 trillion Btu/yr of energy in the United States (based on 15.1×109 Ib crude oil processed). Electricity requirements for a typical refinery are between 120,000 kWh and 160,000kWh/yr (based on 1400 to 1800 kWh/22,000 Ib crude oil processed/hr). Current membrane separation research, as applied to miscella distillation; vapor recovery; condensate return; wastewater treatment; degumming, refining, and bleaching; hydrogenation catalyst recovery; oilseed proteins; and nitrogen production, is reviewed in this paper. The greatest potential for energy savings of 15 to 21 trillion Btu/yr exists in replacing or supplementing conventional degumming, refining, and bleaching processes. Decreased oil losses and decreased bleaching earth requirements are other potential advantages of membrane processing. Approximately 2 trillion Btu/yr could be saved using a hybrid membrane system to recover solvents in extraction of crude oils. Although marginal success has been reported to date, the development of hexane-resistant membranes may make this application viable. © 1990 AOCS Press.