(679a) An Exploratory Study of the Use of Combined Lattice Boltzmann – Discrete Element Method Modeling of Agitated Solid-Liquid Suspensions
AIChE Annual Meeting
Monday, November 15, 2021 - 3:30pm to 3:55pm
One of the most fundamental parameters to be provided by simulation of an agitated system is impeller power draw because of its impact on both process and mechanical design. Simulations currently provide accurate results of impeller power draw in liquid-only systems, but results in multiphase systems are lacking. Extensive experimental data that illustrate the effects of impeller type and solid characteristics on impeller power draw in these systems* provide the opportunity to critically evaluate the capabilities of simulation tools and determine if they are developed to the point that they can be successfully and confidently applied on a routine basis for agitator design.
Examples of experimental data that will be used to test the simulation results include the following:
- Addition of settling solids that increase suspension density have been found to increase the power number of all impellers (when power number is based on liquid density); however, the increase in power number with suspension density is less with flat impeller blades that generate large trailing vortices (e.g. â pitched-blade and Rushton turbines) than with profiled impeller blades that generate small trailing vortices (e.g. â hydrofoils).
- Addition of large neutrally-buoyant particles that do not alter suspension density would not be expected to affect impeller power draw. This lack of effect has been observed with a Rushton turbine, but the power draw of pitched blade turbines and narrow-blade hydrofoils increased dramatically with increasing solid content.
- Large settling solid particles increase the power number of a pitched-blade turbine more than small particles.
*K. J. Myers, E. E. Janz, T. Bao, and M. M. Heigl, âImpeller Power Draw During Turbulent Operation in Solid-Liquid Systemsâ, Canadian Journal of Chemical Engineering, Volume 97, pages 2662 â 2670 (2019).