Student Exercises—Feed-Forward and Cascade

17	Consider again the reactor control system from Exercise 8. If there is also a measurement of the concentration of the reactor feed stream (before it enters the heat exchanger), show how it can be used in a feed-forward-control strategy (using the previously developed cascade type of strategy). Show this on both the control instrumentation diagram below and the control block diagram.
18	Design a feed-forward/cascade control strategy for the following level control problem. Draw the instrumentation directly on the figure. Draw a control block diagram, labeling all the signals on the diagram
19	Consider the heater shown in Exercise 9. Now consider implementing feed-forward and cascade control when process flow disturbances can occur, as shown below. For a change in the inlet process flow rate of 1,000 Bbl/day, there is a change of –10°F in the outlet temperature. Also, the dynamic behavior can be described by a first-order lag of 5 minutes and a one minute time delay. Use the information from Exercise 9 to design a feed-forward/feedback/cascade-control strategy, and perform simulations for a step feed flow rate disturbance of 2,000 Bbl/day.