TABLE OF CONTENTS The objectives for this chapter are to help the user identify advanced process control (APC) opportunities, estimate benefits, select the best technology, sustain the solution, and track the benefits. Industry is driven by cost and benefits analysis and is generally not interested in a great technology looking for an application. This chapter combines the methods that have been used extensively to identify opportunities for APC in the chemical and the pulp and paper industries [3.1] [3.2] [3.3] [2.4] [2.5].
There is an interaction between steady-state design and controllability. As the thermodynamic efficiency is increased, the controllability is decreased [3.6]. The driving forces, such as pressure drops and temperature differences, available for manipulation by the control system are minimized. The result is an increased variability and an optimum that is more difficult to hold. Also, the existing plants in the petroleum and chemical industry are pushed to run at twice the original plant nameplate capacity. The result is shifting bottlenecks and unforeseen equipment constraints and operating conditions.
Yet, process design as taught and practiced focuses on steady-state operation. Engineering companies design exclusively for the steady state and have essentially no experience with variability or dynamics. The emphasis on minimizing changes in design to minimize risk and maintain the budget and schedule often results in a plant built just like the last one. Not surprisingly, plant variability audits show that most plants have the same problems. On top of this, people in the plants are resistant to change
