1). You are initially tasked with developing a basic process control strategy that ensures the safety and operability of this plant and maintains important process variables close to normal operating values. 

Provide an updated schematic that shows all control loops you propose to use. Justify the reasoning for the need to include each controller, briefly explaining how it contributes to the plant’s safety and operability. 

2). Across this plant section, steam is used as a heating medium. During operation, it has been observed that the pressure of the steam pipelines used as heating medium experiences oscillations that cause unacceptable deviations from setpoints of the controlled variables. 

Update the basic process control scheme from part 1 to account for the latter issue. The proposed design should achieve its objective while ensuring the smooth operation of the plant and the possibility of operator errors

3).  Strong market demand suggests operating the plant at maximum production level. There are however three possible factors that could limit the operation of this plant and need to be considered during plant throughput maximization: 

a) Heating medium availability for the reactor 

b) Maximum flow of vapor product from the flash drum

c) Maximum reboiler duty possible in the distillation tower. 

You are tasked with enhancing the control strategy of the plant from part 2 by designing a control system that achieves as primary objective the highest production rate in steady state. Secondary objectives of the design are its smooth dynamic response that accounts for possible errors of operators.

 Analyse how your proposed control design monitors and ensures that the three limitations above are not violated. Further discuss how the control scheme accounts for these limitations simultaneously while aiming at maximizing production and provide an updated schematic of your proposed control design. Clearly explain the reasoning behind all design decisions taken, including setpoints chosen (e.g. their magnitude or relation to other variables’ values), to demonstrate the functioning of the scheme. Update the process diagram to include the new control scheme. 

4). It has been identified that variations in the feed rate of the distillation column have an unacceptable impact on the composition of the overhead product. There are historical data on two step tests available, one on the effect of the column feed flow rate (via v6 manipulation) on the overhead product composition, and one on the effect of the reflux flow rate (via v8 manipulation) on the overhead product composition. Results of these tests are summarized in the tables in the Appendix below, where in both cases a unit step change in kg/min had been implemented to the respective flow rate.

The distillation column feed flow rate measuring device is calibrated in a range of 0 to 50 kg/min, and the reflux flow rate measuring device is calibrated in a range of 0 to 100 kg/min. The output signals of both devices are linear to the respective flow rates and can be assumed to cover the entire range of these flow rates. First, draw the block diagram of the existing closed loop process developed in previous parts showing all relevant transfer functions.

Use the available data to determine, or approximate where necessary, the transfer functions for the block diagram, showing the numerical values of all parameters and explaining clearly how the latter were obtained. For any controllers implemented in previous parts, use a generic PI transfer function.

Using the block diagram and respective transfer functions, design a suitable feedforward controller that can compensate for the feed disturbance on the composition of the overhead product. Provide the values of all parameters of the proposed controller and show clearly how they were obtained. Update the process diagram and block diagram to include the new feedforward control scheme. 

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