2009 Volume 21 Issue 1 Pages 69-76
PID control methods remain popular in industrial applications. However, due to their poor ability to react appropriately in an unsteady operational environment, they sometimes fail to control the actual plant, including operations such as feed oil changing and process line changing. On the other hand, well-experienced operators can easily manage these operations by appropriately manipulating the set points or adjusting the output of the PID controller using their experience and knowledge. In an ethylene plant, the decoking operation of the cracking furnace is highly unstable. To mimic the well-experienced operator's procedures, we have developed a hierarchical system that consists of an intelligent sequence control and a PID control. The intelligent sequence control plays the role of the well-experienced operator. We applied the hierarchical system to the decoking process in ethylene plant in order to demonstrate its effectiveness.
