EXERCISES cal ch) COM (C) not sume that D-4 12. Consider the distillation column shown in Fig 122. It wodd be reasonable to control the liquid level in the reflux dun. hy by manipulating either reflux flow rate, or distil Iste low rate, D. How would the nominal value of the refus atio (RD) influence your choice? As a specific example, as 11.2 Astirred tank blending system with a trypass stream pierwn in Fig. E12.2. The control objective is to control the certposition of a key component in the exit stream, I. The chose disturbance variables are the mass fractions of the key component in the Inlet streams, and xy Using the following formation, discuss which flow rate should be selected as the manipulated variable: inlet flow rate. (ii) the bypass fraction or (ii) exit flow rate. Your choice should relect both steady-state and dynamic considerations (d) 12.0 be SO trol a) att 11 - 1 e) bet cho 12 lati w be W tho Figure E12.2