Fig. 18 illustrates the calculated and measured values for the
reflux ratios for all the extraction experiments for the separation
palmitic/(oleic + linoleic) acids from palm fatty acid mixtures. The
reflux ratio was calculated using the McCabe-Thiele method. The
results show that the calculated and measured values for the reflux
ratio are very close when the countercurrent column operates with
low reflux mass flow rates. However, the difference between the
calculated and measured values increases when the column operates
with reflux ratios higher than one. The absolute error between
measured and calculated reflux ratios lies between 20 and 50%. This
may be due to uncertainty (±10%) of phase equilibrium measurements
which provide the basis for the stage-to-stage computation
with both the McCabe-Thiele and Ponchon-Savarit methods and
errors associated to the measure of the reflux mass flow rate. The
mass flow meter used to recycle the extract into the top of the
column is not appropriate to measure mass flow rates lower than
120 g/h (manufacture specifications). The lower the reflux mass
flow rate, the higher the measurement error. Since the equilibrium
solubility of palm fatty acids distillates in supercritical carbon dioxide
is low at the operating conditions used to carry out extraction
experiments (22 g/kg), it would be necessary to operate with a feed
flow rate of at least 150 g/h in order to provide the minimum mass
flow rate requirements. In this case, a solvent flow rate of approximately
8 kg/h would be necessary to completely dissolve the solute
in the gaseous phase. However, at those conditions, the column can
no longer operates in countercurrent mode.
Fig. 18 illustrates the calculated and measured values for thereflux ratios for all the extraction experiments for the separationpalmitic/(oleic + linoleic) acids from palm fatty acid mixtures. Thereflux ratio was calculated using the McCabe-Thiele method. Theresults show that the calculated and measured values for the refluxratio are very close when the countercurrent column operates withlow reflux mass flow rates. However, the difference between thecalculated and measured values increases when the column operateswith reflux ratios higher than one. The absolute error betweenmeasured and calculated reflux ratios lies between 20 and 50%. Thismay be due to uncertainty (±10%) of phase equilibrium measurementswhich provide the basis for the stage-to-stage computationwith both the McCabe-Thiele and Ponchon-Savarit methods anderrors associated to the measure of the reflux mass flow rate. Themass flow meter used to recycle the extract into the top of thecolumn is not appropriate to measure mass flow rates lower than120 g/h (manufacture specifications). The lower the reflux massflow rate, the higher the measurement error. Since the equilibriumsolubility of palm fatty acids distillates in supercritical carbon dioxideis low at the operating conditions used to carry out extractionexperiments (22 g/kg), it would be necessary to operate with a feedflow rate of at least 150 g/h in order to provide the minimum massflow rate requirements. In this case, a solvent flow rate of approximately
8 kg/h would be necessary to completely dissolve the solute
in the gaseous phase. However, at those conditions, the column can
no longer operates in countercurrent mode.
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