Fault-tolerant control of a polyethylene reactor

Fault-tolerant nonlinear control of a gas phase polyethylene reactor was studied. The feed to the reactor consisted of ethylene, comonomer, hydrogen, inerts, and catalyst. A stream of unreacted gases flowed from the top of the reactor and was cooled by passing through a heat exchanger in counter-current flow with cooling water. Initially, a family of candidate control configurations, characterized by different manipulated inputs, were identified. For each control configuration, a bounded nonlinear feedback controller, that enforces asymptotic closed-loop stability in the presence of constraints, was designed, and the constrained stability region associated with it was characterized using Lyapunov-based tools. Closed-loop system simulations demonstrate the effectiveness of the fault-tolerant control strategy. This is an abstract of a paper presented at the AIChE Annual Meeting and Fall Showcase (Cincinnati, OH 10/30/2005-11/4/2005).