The solubility (gas load) ofpalmfatty aciddistillates insupercritical
CO2 and the selectivity ˛i,j =
KC16/KC18.1+C18.2
as a function
of gas phase density are illustrated in Fig. 10, which shows how the
equilibrium properties (solubility and selectivity) may be used to
chose feasible operating regions in order to optimize process variables
(number of stages, solvent-to-feed ratio, and flooding) for the
separation of palmitc/(oleic + linoleic) acids from palm fatty acid
distillates mixtures in multistage countercurrent columns using
supercritical CO2. Fig. 10 shows the existence of two constraint dot
lines (flooding and solubility). The solubility constraint line was
defined to be 1.0 wt.%. Lower solubilities in the gaseous phase are
associated with high solvent to fed ratios and hence large amounts
of solvent(high compression and regeneration costs)to achieve the
desired separation task. Furthermore, columns with higher internal
diameter would be necessary to assure high solvent mass flow
rates. The flooding constraint line can be compute from density
data ofthe coexisting liquid and gaseous phase. Since the density of
the coexisting liquid phase varies in the range L ∼= 850–900 kg/m3
for the system under investigation, it is, therefore, easy to calculate
the maximum allowable solvent density (G ∼= 700 kg/m3) at
which the column could still operates in countercurrent mode.
Fig. 10 shows also that flooding can also be avoided by increasing
the operating temperature. However, high operating temperatures
resultin degradation ofthermally labile substances (e.g. processing
of biomaterials). Thus, the temperature itself can be also a process
constraint. In this since, points A, B, and C are the only remaining
experimental conditions that meets solubility and flooding constraint
lines.
The solubility (gas load) ofpalmfatty aciddistillates insupercriticalCO2 and the selectivity ˛i,j = KC16/KC18.1+C18.2as a functionof gas phase density are illustrated in Fig. 10, which shows how theequilibrium properties (solubility and selectivity) may be used tochose feasible operating regions in order to optimize process variables(number of stages, solvent-to-feed ratio, and flooding) for theseparation of palmitc/(oleic + linoleic) acids from palm fatty aciddistillates mixtures in multistage countercurrent columns usingsupercritical CO2. Fig. 10 shows the existence of two constraint dotlines (flooding and solubility). The solubility constraint line wasdefined to be 1.0 wt.%. Lower solubilities in the gaseous phase areassociated with high solvent to fed ratios and hence large amountsof solvent(high compression and regeneration costs)to achieve thedesired separation task. Furthermore, columns with higher internaldiameter would be necessary to assure high solvent mass flowrates. The flooding constraint line can be compute from densitydata ofthe coexisting liquid and gaseous phase. Since the density ofthe coexisting liquid phase varies in the range L ∼= 850–900 kg/m3for the system under investigation, it is, therefore, easy to calculatethe maximum allowable solvent density (G ∼= 700 kg/m3) atwhich the column could still operates in countercurrent mode.Fig. 10 shows also that flooding can also be avoided by increasingthe operating temperature. However, high operating temperatures
resultin degradation ofthermally labile substances (e.g. processing
of biomaterials). Thus, the temperature itself can be also a process
constraint. In this since, points A, B, and C are the only remaining
experimental conditions that meets solubility and flooding constraint
lines.
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