Design of a Hierarchical System Using PID Control with an Intelligent Sequence Controller and Its Application to Ethylene Plants in Unsteady State
Tetsuji TANI, Takeshi TAKEUCHI
A hierarchical system is developed that consists of an intelligent sequence controller and a PID controller, where the intelligent sequence controller supervises the PID controller. In other words, the intelligent sequence controller plays the role of a well-experienced operator and mimics the operator's procedures. In an ethylene plant, the decoking operation of the cracking furnace makes the ethylene plant highly unstable. We apply this hierarchical system to the decoking process in an ethylene plant in order to demonstrate its effectiveness. As a result, the number of operational interventions in the decoking process is reduced by 95%, and the levels of the towers and the overhead temperatures of the towers can be satisfactorily stabilized during the decoking process.