Analysis of Lab-Scale Column

Another simple model problem can be stated by assuming an infinite number of stages and an infinite reflux ratio. This oo/oo-analysis has been introduced originally by Petlyuk and Avetyan [82] and extensively applied for the analysis of non-reactive and RD columns by Morari and coworkers [8, 34, 35] and Marquardt and Miiller [76], If applied to RD, not only phase equilibrium but also chemical equilibrium have to be assumed. 

Reder et al. [88] have applied this analysis technique to study distillation of the methyl formate system. They report unique steady state solutions for all possible feeds, if distillation of the (hypothetical) non-reactive quaternary system MeOH/ FA/MF/W is considered. In contrast, steady state multiplicity can be found for the reactive system in the distillation region formed by MF, MeOH, Wand the binary azeotrope but not for the distillation region formed by FA, MeOH and the binary azeotrope. In fact, an infinite number of steady states with different distillate concentrations can be found for some critical bottom flow rate B. Fig. 10.4 shows the distillate concentration as a function of B varying from zero to its maximum value. 

The infinite number of steady states occurring in the limit of the oo/oo-analysis is not peculiar to the methyl formate system. Rather, a similar situation can be expected for other kinds of esterifications with a similar topology in the space of transformed concentrations. 

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