Hydrodynamics of Polyolefin Slurry Loop Reactor: CFD Analysis

In recent years, large amounts of polyolefins such as polypropylene and polyethylene are produced in slurry loop reactors (Total length in the range of 200-400 m, diameter in the range of 0.3-0.6 m). In this technique solid (catalyst particles) and liquid (monomer) are circulated in array of vertical tubes interconnected with elbows, using one or two internal axial pumps (circulation velocity 6 – 10 m/s).  For efficient design and scale-up of these reactors, understanding the hydrodynamics of the slurry mixture is essential. Using the Two Fluid Model (TFM) we are investigating the hydrodynamic interactions of solid and liquid to make the reactor more energy efficient and productive. The goal is to understand the phase distributions near the impeller exit zones and near the bends and their dispersion characteristics.

To validate the mechanisms of axial dispersion in loop reactor, simulations of a pilot plant were carried out. With this simulation results we validated the present multi-fluid Eulerian CFD model by favorably comparing the simulated results with the pilot plant measurements. After 13 cycles the pilot plant experimental value of the pulse width at the half maximum is 0.55 sec and the simulated value is 0.52 sec. We also performed full-scale unsteady simulations of 6 leg slurry loop reactor which provided a valuable insight of the reactor and useful especially in understanding of the phase distributions across the length of the reactor.