Regular Solution Approach to Modeling the Supercritical Fluid Extraction of Two-Component Solutes from Ground Oilseeds

The extract obtained at supercritical fluid extraction from plant raw material is essentially multicomponent. A multicomponent mass-transfer model at the particle scale is developed to account for the non-ideality of the chemical interactions between solute components. The oil is represented by two pseudo-components, and the gradient of the chemical potential is considered the driving force for the mass transfer. The model is based on the regular solution and Gibbs energy approaches to the thermodynamic modeling of phase equilibria that take place in the raw material with a high initial oil content. The Stefan–Maxwell approach is used to balance the drag effect/chemical interactions and the driving force of diffusion in a non-equilibrium multicomponent solution. It is demonstrated that the two solute components may act as “co-solvents”, thus facilitating the extraction of each other, or as “anti-solvents”, thus decreasing the overall extraction rates. At least a 60% relative error in the overall flux from the particle surface is observed when the developed model is compared against a simplified approach that considers the solution as an ideal system. It is found that while the flowing fluid accumulates the extracted solute, the phase separation may take place in the pore volume of the packed bed. Possible conditions of phase separation in the pores of the packed bed are discussed.