| One of the most important characteristics of a polymer is its molecular weight distribution (MWD). Until recently, inappropriate measures of this property were specified. From the extensive kinetic and process modeling studies that have been compiled to date, and the variety of control strategies available, the rewards have been twofold: a better understanding of the process, and the ability to set and maintain tighter limits on important polymer properties (e.g. molecular weights).;A multiple-input/multiple-output (MIMO) control strategy is applied to the solution polymerization of methyl methacrylate in a CSTR. The strategy will be investigated at the simulation level only, and its capability tested by introducing unmeasured disturbances (reactive impurities). In particular, two MIMO control laws are implemented and compared. These are the Vogel-Edgar controller and an optimal control law which is derived from a quadratic performance criterion. The manipulated variables are the initiator concentration in the feed and the reactor jacket temperature. By varying independently these two input variables, different levels of control can be achieved over the production rate (i.e. monomer conversion) and more importantly the polymer molecular weights, while at the same time maintaining robustness (insensitivity to process/model mismatch). |
