On-line Computer Control of a Continuous Latex Reactor Train

During continious emulsion polymerization of many monomers. Mistained oscillat ions limit cycles occur in all the latex and polymer properties This creates severe problems with the commercial application of continuous reactors. A mathematical model, based on a particle age distribution analysis and incorporating detailed chemistry and physics of the Polymerization phenomena involved. is used to simulate the dynamic behaviour of these reactors Advanced control theory is shown to he inadequate for controlling these svstems. Rather. it shown that the limit cycle behaviour must be eliminated through redesign of the reactor train configuration using the dynamic model. The redesigned reactor Configuration is shown to eliminate the Oscillations . and to offer greatly increased flexibility in controlling the particle size and conversation. Experimental studies which demonstrate the improved dvnamic performance of the redesigned reactor system are carried out in a pilot plant stainless steel reactor train. On line measurements of conversion and particle size are obtained using densitometers and U.V spectrophotometers. Off line measurements of particle size are obtained by turbidity sped ra. size exclusion chromatography (SEC) and electron microskopy. and measurements of the molecular weight averages are obtained by gel permeation chromatomaphy (GPC) and low angle laser light scattring (LALLS). Multivariable computer control of the final latex particle size and thie monomer conversion is achieved using several algorithms which manipulate the feed rate of initiator to the first reactor and the split of the monomer and water feed rates between the first two reactors Control is achieved using VAX plus PDP front end system interfaced to the pilot plant reactors.