Polymer Reactor Design, Optimization and Control in Latex Production Technology

Abstract

<p>During continuous emulsion polymerization of many monomers (e.g. vinyl acetate, vinyl chloride), sustained oscillations (limit cycles) occur in conversion and all the latex and polymer properties. This creates severe problems with the commercial application of continuous reactors. As shown by Pollock (1984) advanced control theory is inadequate for controlling these reactors. However, it was shown that the limit cycle behaviour could be eliminated through redesign of the reactor train configuration. The redesigned production train was shown via simulation to be free of oscillations and to offer greatly increased flexibility in controlling particle size and monomer conversion.</p> <p>In this thesis the mathematical model of Kiparissides (1978) and Pollock (1984), based on a particle age distribution analysis and incorporating detailed chemistry and physics of the polymerization phenomena involved, is modified and is used to simulate the dynamic behaviour of these reactors for different modes of process operation (batch, semi-batch and continuous train) and monomer systems (PVAc, PVc).</p> <p>Experimental studies which demonstrate the improved dynamic performance of the redesigned reactor system are carried out in a pilot plant stainless steel reactor train with on-line monitoring of monomer conversion with a set of on- line densitometers. Control of the final latex particle size and conversion is achieved through manipulation of the initiator feed rate to the first particle nucleating reactor, and the split of the monomer and water flow rates between the first two reactors of the train.</p> <p>The effect of monomer arid water soluble impurities on the emulsion polymerization of Case I monomers is further investigated both theoretically and experimentally. Experimental identification and verification of the main source of stochastic disturbances in these systems was thus obtained.</p>