A Hierarchical Optimization Approach to Optimal Production Scheduling in an Industrial Continuous Olefin Polymerization Reactor

The time‐optimal grade‐transition policies, as well as the selection of the optimal grade production sequence, are calculated for a gas‐phase ethylene/but‐1‐ene copolymerization FBR. The tuning parameters (i.e., proportional gain and integral time) of the feedback PI process controllers, as well as the time‐optimal trajectories of the feedforward controllers, are treated as decision variables. A two‐level decomposition approach is applied for solving the optimal‐grade transition‐scheduling problem, taking into account the impact of both transient operation and the sequence of grade transitions on the overall amount of off‐spec polymer and overall transition time.