On the prediction of suspension viscosity, grain morphology, and agitation power in SPVC reactors

Abstract

AbstractThe role of primary and secondary stabilizers in the suspension polymerization of VCM and their effect on grain morphology (i.e., particle size distribution, grain porosity, and bulk density) is critically discussed. Using the modified Mooney equation, the time‐varying viscosity of the suspension in an SPVC reactor is calculated in terms of the volume fraction of the dispersed monomer/polymer phase, the ratio of the viscosity of the dispersed phase over the viscosity of the continuous aqueous phase, and the maximum packing volume fraction of SPVC grains. A population balance equation is numerically solved to calculate the dynamic evolution of particle size distribution (PSD) in an industrial batch suspension VCM polymerization reactor. A porosity model is postulated to calculate the dynamic evolution of the PVC grain porosity with respect to monomer conversion and the extent of primary particle fusion. Finally, the underlying theory regarding the calculation of the required agitation power in SPVC reactors is detailed. It is shown that the time‐varying viscosity of the suspension can be calculated and the PVC grain morphology (i.e., extent of particle agglomeration) can be accessed via the on‐line estimation of the effective volume fraction of the dispersed phase using on‐line power agitation measurements obtained from an industrial‐scale SPVC reactor.