As an example let us consider a binary distillation column designed to separate water from nitric acid. Top composition is controlled by manipulating reflux (see Figure 20.1) while the base composition is controlled by adjusting steam flow. The following transfer functions were derived via the stepping technique:
ol ol ol ol
The time constants are in minutes.
From these we find that the large top block of Figure 20.6 becomes [equation (20.7)]:
Correspondingly, the large block in the bottom loop of Figure 20.6 [Equation (20.8)] becomes:
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