Dynamic evolution of the particle size distribution in multistage olefin polymerization reactors

Abstract

A wide range of polyolefins are produced in catalytic particulate polymerization reactors (e.g., loop, continuous-stirred tank, horizontal stirred bed and fluidized-bed reactors). In each of these reactor configurations, the dynamic evolution of the particle size distribution (PSD) is a key variable that affects both the reactor operability and the end-use properties of the final product. In the present study, a comprehensive population balance model is developed to predict the evolution of particle size distribution in multistage olefin polymerization reactors. Specifically, the PSD is considered to evolve in time under the combined effect of particle aggregation and growth mechanisms. Two different numerical methods (i.e., the orthogonal collocation and the Galerkin on finite elements) are employed for solving the population balance equation. The performance of the two numerical methods is assessed in terms of accuracy, stability and computational efficiency of each method. It is shown that the dynamic evolution of PSD is highly affected by the operating conditions and the selected reactor configuration. Furthermore, it is shown that particle agglomeration can significantly affect the evolution of PSD in a multistage reactor configuration.