(83c) Simulation of a Radial Flow Gas Induction Agitator System

Hoffman et al. (2022) presented performance data for a gas induction impeller. This data was collected over three different laboratory scales (tanks of 0.4445 m, 0.5969 m and 1.524 m) and used as part of the validation and verification effort with M-Star CFD that will/was presented at the joint NAMF-Mixing XXVIII and ISMIP 11 conference in June 2024. (Janz, Myers, Athanasiou, 2024).

Ultimately, the CFD method's usefulness is examining the performance of industrial scale applications where measurement of the actual flow rates or just induced speeds are much more difficult than at the lab and pilot scales. Not only are the process gases regularly hazardous (e.g. hydrogen, chlorine, bromide), the processes are typically carried out under significant pressure. Using a viewing port on vessel top, an investigator may be able to identify when gas starts to evolve from the liquid surface, or a relative intensity of the gas being evolved but not quantitative values.

In this study, an industrial application of a radial flow gas induction impeller is analyzed via CFD using M-Star CFD. From plant observations, the minimum induction speed for this process is known but other details are limited. Using method from the Janz, et al. an immiscible fluid model will be used with a Eulerian immiscible fluid to Lagrangian particle conversion method to allow simulation of the induction process and bubble transport in a reasonable time from (hours to days on dedicated desktop hardware).

The objectives of this study are to:

• Accurately predict the just induced speed based on the plant operating parameters.
• Develop a correlation for the gas induction speed given liquid height and fluid conditions.
• Develop a correlation for gas flow rate after the agitator speed has exceeded the just induced speed.

References:

1. Hoffman, Shannon M., Eric E. Janz, Kevin J. Myers, and Nicholas A. Brown. 2022. Performance Characteristics of an Axial‐Flow Gas Induction Impeller. The Canadian Journal of Chemical Engineering 101 (3): 1371–86. https://doi.org/10.1002/cjce.24556
2. Janz, Eric. E., Kevin. J Myers, & Panagiotis Athanasiou, P. Simulation of an Axial-Flow Gas Induction Impeller.Mixing XXVII.