Reactive Distillation Technology - Process Intensification for Green Chemistry - page 264

Figure 9.9 Flow sheet configuration and control strategy of the dual RD setup. Reprinted from
Dimian et al. # 2009, with permission from Elsevier.
the top and the bottom of the RDC. In contrast, control structures fixing the feed rates
of all reactants (acid, light and heavy alcohol) will not work in the presence of small
control implementation errors, the failure manifesting in the accumulation or depletion
of one reactant [58].
Figure 9.10 (top) compares the temperature profiles for the base case and for a 10%
increase of the lauric acid flow rate with and without temperature control [48]. Accurate
control of the lauric acid concentration in the bottom stream is achieved by using a
concentration controller that prescribes the set point of the temperature controller in a
cascade structure. For this control configuration, the change in the lauric acid feed flow rate
leads to a change in the methyl-ester production rate. In contrast, when both flow rate ratios
(i.e. lauric acid feed/methanol entering the column and lauric acid feed/heavy alcohol
reflux) are constant, the change in the lauric acid feed flow rate leads to changes in both the
methyl-ester and ethyl-hexyl ester production rates.