(222u) Modeling of Liquid-Liquid Equilibrium for Extraction of Free Fatty Acids (FFAs) in Corn Oil

Modeling of Liquid-Liquid Equilibrium for Extraction of Free Fatty Acids (FFAs) in Corn Oil.

Removal of free-fatty acids (FFA’s), whose content in crude corn oil and other sustainable vegetable oils varies from 3% to 40% [Srivastava and Prasad, 2000; Ma and Hanna, 1999], is an essential process for creating refined products that can be subsequently used in food and other important applications. The method chosen for oil extraction depends on the nature of the raw material, as well as on the capacity of the industrial plant. Pressing followed by solvent extraction is the method most widely employed for handling a wide variety of oilseeds [Young et al., 1994], which contribute nearly 50% of the total vegetable oil produced in the world. The crude oil that is extracted from the oilseeds is a mixture of FFA, mono-, di-, and triglycerides, phosphatides, pigments, sterols and tocopherols.

Several approaches for removal of the FFA’s can be used that are based on non-reactive and reactive solvent extraction.  In non-reactive extraction, for example, either pure methanol (MeOH) or MeOH-water mixtures are commonly used to selectively extract the FFA’s from the crude oil.  Reactive extraction involves contacting the crude oil with a solution of MeOH with dissolved sodium hydroxide (NaOH) to form the sodium salts of the corresponding acids.  Design of either non-reactive or reactive extraction contactors requires accurate predictions of thermodynamic phase equilibrium properties.  

In this poster, experimental liquid-liquid equilibrium data for ethanol-water-corn oil and pure ethanol-corn oil are used as the basis for discrimination between two solution–phase thermodynamic models. The resulting parameters are then used as the basis of an Aspen simulation for extraction of FFA’s from corn oil using ethanol and ethanol/water mixtures as extraction solvents.

The liquid-liquid extraction is modeled using the Non-Random Two Liquids (NRTL) and the UNIversal QUAsi Chemical models in which the interaction parameters for both models are obtained by regression analysis of experimental liquid-liquid extraction data. It is shown that the NRTL model provides the best agreement between experimental and model-predictions. Simulation of the extraction using this models shows that realistic predictions for the concentration profiles for the various species.  It also provides information needed to evaluate the performance of simultaneous reaction with extraction for the case where NaOH is added to the solvent. 

References

1. Srivastava, A., Prasad, R., 2000. Triglycerides-based diesel fuels. Renew.Sustain. Energy Rev. 4, 111–133.

2. Ma, F., Hanna, M.A., 1999. Biodiesel production: a review. Bioresour. Technol. 70, 1–15.

3. Young, F. V. K., Poot, C., Biernoth, E., Krog, N., Davidson, N. G. J.,& Gunstone, F. D. (1994). Processing of fats and oils. In F. D. Gunstone, J. L. Harwood, & F. B. Padley (Eds.), The lipid handbook (2nd ed., pp. 249–276). London, UK: Chapman & Hall.