Using the Quasi-Steady-State Approximation to Reduce the Computation Time of the Polymeric Flow Model for Olefin Homopolymerization

In this article we propose a novel way to solve the Polymer Flow Model (PFM) using the quasi steady-state approximation (QSSA). The accuracy of the QSSA model was quantified by comparing polymerization rates, particle growth factors, mass transfer efficiencies, and molecular weight distributions simulated at different Thiele modulus values with the predictions from two different non steady-state (dynamic) solutions of the PFM. The QSSA model predictions become increasingly more accurate after the first few minutes of polymerization for catalysts with low to medium Thiele moduli. Even though the proposed QSSA method deviates more significantly from the PFM dynamic solution at high Thiele modulus values, from a practical point of view this is of little relevance since this condition corresponds to high levels of mass transfer limitations that are avoided in industrial processes. Finally, the computation time of the QSSA method is drastically faster than those of dynamic models, making the proposed approach ideal for integration with large-scale industrial models that must describe whole polymer particle populations instead of single particles.