Coupling Solvent Extraction Units to Cyclic Adsorption Units
Table 1
Relation between SLA and LLE equilibrium and kinetic coefficients. Application to the extraction of oleic acid with methanol from sunflower oil and the adsorption of oleic acid from methanol over a solid adsorbent (activated carbon).
Concept
Adsorption
L-L extraction
Equilibrium distribution between the two phases
= = concentration of impurity in the solid phase, mol kg−1
= concentration of impurity in the liquid phase, mol L−1
= concentration of oil in the liquid phase, mol L−1
= concentration of impurity (oleic acid) in the raffinate phase (sunflower oil) mol L−1
= concentration of methanol in the liquid phase, mol L−1
= concentration of impurity (oleic acid) in the extract phase (methanol), mol L−1
= Langmuir constant for OA adsorption, L mol−1
= saturation capacity for OA over the adsorbent, mol kg−1
, = Freundlich constants for specific adsorbent and adsorbate
= Henry’s constant for adsorption of OA
Relation between flux densities and interfacial gradients
= flux across the film surrounding the particle (eq. )
= flux due to diffusion (eq. ). Both fluxes are equal at steady-state
= film coefficient
= surface concentration of adsorbate
= film coeff., MeOH side
= concentration of impurity on the surface of the adsorbent
= film coeff., oil side
= function that gives the value of from the value of concentrations in the liquid phase (eq. )
= impurity molar flux, molecules per unit time and area
= bulk density of the adsorbent particle
int = interface
= net diffusivity of the adsorbate inside the adsorbent particle
Relation between fluxes and driving forces
= average adsorbate concentration in the adsorbent particle
= surface concentration
= overall transfer coefficient
= effective film coefficient for intrapellet diffusion
= overall transfer coefficient
= equilibrium adsorbate concentration for (eq. )
eq = equilibrium
= linear driving force mass transfer coefficient for adsorption
Mass transfer coefficients
= porosity of the adsorbent particle
= radius of the adsorbent particle
= film transfer coefficient.
= film transfer resistance
= hold-up of the disperse phase (oil)
= intrapellet diffusion resistance
= average Sauter diameter
= slip velocity between phases
= viscosity of the continuous phase
= volume of the disperse phase
= volume of the continuous phase
= mass transfer coefficient, continuous phase
= mass transfer coefficient, disperse phase
Mass balance: batch unit perfectly mixed
= volume of adsorbent
= interfacial area per unit volume of whole liquid phase
= weight of adsorbent
Mass balance: continuous contact tower equations
= bed porosity
= superficial velocity
= fluid phase concentration of the impurity
= axial coordinate, height of the column
= solid phase concentration of the impurity
= average interfacial area per unit volume of the contactor vessel
