Question: The design in Figure is proposed for an isothermal, well-mixed CSTR with a single reaction A → B with rA = -kCA. The main disturbance is a steplike disturbance in the feed flow rate, and real-time measurement and control of the compositions is not possible. Evaluate the control performance (i.e., the deviation of the composition) for (a) perfect PI control of the level (the level exactly remains at its set point at all times) and (b) P-only control of the level. Which approach gives a smaller deviation for the compositions from the initial conditions at the final steady state? Does your answer depend on the tuning of the P-only controller? If so, what is the best value of the controller gain?
