Optimization of molecular weight distribution using batch-to-batch adjustments

A batch-to-batch optimization methodology for producing a desired MWD using an approximate model is presented. A measurement of the molecular weight distribution (MWD) at the end of the batch is used to update manipulated variable trajectories for the next batch, thus iterating into a good operating policy. The optimization approach is then extended for use as an online control method. A multivariable statistical process control (MSPC) monitoring scheme is developed for deciding when a new batch optimization is required. The optimizer remains on, but dormant while the desired MWD is being produced, and re-optimizes the process quickly if the process changes and poor quality polymer is produced. The combined MSPC/batch-to-batch optimizer is demonstrated on a simulated semi-batch polystyrene reactor