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Homework 01 - Textbook Scan Ch 1

Homework 01 - Textbook Scan Ch 1 - E xercises l3 b oth an a...

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Exercises l3 both an art and a science, Process understanding and the experience and preferences of the design team are key factors. Computer simulation of the controlled process is used to screen alternative con- trol strategies and to provide preliminary estimates of appropriate controller settings. Finally, the control system hardware and instrumentation are selected. ordered, and installed in the plant. Then the control system is tuned in the plant using the preliminary estimates from the design step as a starting point. Controller tuning usually involves trial-and-enor procedures as described in Chapter 12, SUMMARY In this chapter we have introduced the basic concepts of process dynamics and process control. The process dynamics determine how a process responds during transient conditions. such as plant start- ups and shutdowns, grade changes, and unusual disturbances. Process control enables the process to be maintained at the desired operating conditions, safely and efficiently, while satisfying environmental and product quality requirements. Without effective process control, it would be impossible to operate large-scale industrial plants. Two physical examples, a continuous blending system and a distillation column, have been used to introduce basic control concepts, notably, feedback and feedforward control. We also motivated the need for a systematic approach for the design of control systems for complex processes. Control sys- tem development consists of a number of separate activities that are shown in Fig, 1.9, [n this book we advocate the design philosophy that, for complex processes, a dynamic model of the process should be developed so that the control system can be properly designed. A hierarchy of process control activities was presented in Fig. l.7, Process control plays a key role in ensuring process safety and protecting personnel, equipment. and the environment. Controlled vari- ables are maintained near their set points by the application of regulatory control techniques and ad- vanced control techniques such as multi variable and constraint control. Real-time optimization can be employed to determine the optimum coritroller set points for current operating conditions and con- straints. The highest level of the process control hierarchy is concerned with planning
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