For the modeling of orange peel EO microwave assisted
extraction, a model that takes into account the influence of the
process parameters considered in the factorial design (Section 2.3)
was used. The model was proposed by Xavier et al. (2011), which is
based on the concept of broken and intact cells and considers two
extraction periods, the first one governed by phase-equilibrium,
while the second one is limited by internal diffusion in the particles.
The first part of the extraction curve is associated to the
extraction of the free solute from broken cells. In this extraction
step (hypothetical case with negligible external mass transfer
resistance), the fluid phase is in equilibrium with solid phase
throughout the extractor. The second period is controlled by the
solute diffusion from inner cells of vegetal structure and corresponds
to the diffusion from intact cells. In Xavier et al. (2011)
model, mass transfer properties of recovered oil were considered
constant throughout the process. The general equations considered
in this model are the mass balances per unit volume extraction bed
consist of equations for the solute in fluid and solid-phases
described by (eqs. 3.1 and 3.2)