Student Exercises

1:	Consider the ratio control strategy shown in Figure 12-1b. If the blend stream has a concentration measurement and controller, construct the control instrumentation diagram where the output of the concentration controller is the desired ratio of stream B to stream A flows.
2:	Consider the high-temperature select control problem shown in Figure 12-2. Modify the control instrumentation diagram to include a cascade-control strategy, where the output of the reactor temperature controller is the setpoint to a reactor inlet temperature controller. The reactor inlet temperature controller then manipulates the flow to the preheat exchanger.
3:	Consider a gas-phase reactor where a valve on the output stream is normally regulated to maintain a desired outlet composition. Design a selector-based control strategy that switches to pressure control if the pressure is too high.
4:	Consider a waste treatment system. A pH controller may need to adjust the pH by manipulating either basic or acidic stream flow rates. Design a split-range control strategy to do this.
5:	Consider Example 12.1, where input 1 is the cold glycol make-up flow rate, and input 2 is the hot glycol make-up flow rate. The steady-state temperature is 20°C, which is also the vessel feed temperature. At steady-state the cold and hot glycol make-up flow rates are 0. The parameter values are fov = 1/30; % minutes^-1 ua = 24 ; % kcal/min deg C vrhocp = 850 ; % kcal/deg C vrhocpj = 250 ; % kcal/deg C Tjfcold = -20 ; % deg C Tjfhot = 100 ; % deg C Tjs = 20 ; % deg C vj = 250 ; % liters and the state space model matrices are Solve for the numerical values of all matrices. Design a jacket temperature controller and implement the SIMULINK diagram shown in Figure 12-7. Discuss your jacket temperature controller design and tuning procedure. Notice that the jacket temperature output has a range of 100%, constrained between –50% and +50%. The cold valve is fully open at –50% and fully closed at 0%. The hot valve is fully closed at 0% and fully open at +50%,
6:	Develop a SIMULINK diagram of a cascade control strategy, where Figure 12-7 represents the inner-loop (jacket temperature) control system. The output of the primary (outer-loop) controller that you develop should be the setpoint for the jacket temperature controller. Discuss the design and implementation (tuning) of both controllers. Use the parameter values from Exercise 5.