Question: Discuss the performance of Designs I and II and propose better alternative designs, if possible, for the following situations. Each situation is to be considered separately, not cumulatively.

(a) The reactor temperature, T$, must be maintained constant to obtain the best product selectivity. Is there an alternative reactor environment variable that can be adjusted? If yes, design a control strategy to meet the objectives.

(b) The analyzer for the reactor concentration is quite expensive. Is there another variable that can be used in its place?

(c) The control objectives are changed to include tight control of the product flow rate F5. The disturbances are unchanged. How should the control strategy be changed?

d) The daily total production of product B must be satisfied as close to its target as possible. How can the design be modified to satisfy this requirement?

(e) The recycle pump has been replaced with a spare pump of smaller capacity. Modify the control design to produce as much product as possible.