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.