(690c) CFD Analysis of Sparger Design and Bubble Formatoin, Breakup, and Coalesence.

In liquid phase reactions with gas sparging, both sparger design and agitation influence bubble area and mass transfer between the gas and liquid phases. In bubble columns, sparger design is the only influence; in stirred tanks, agitator design dominates. However, even in stirred tanks, non-uniform flow from the sparger can substantially impact the process. We show that modeling the sparger flow as a single phase system can predict non-uniform flow but ignores two phase interactions and fails to predict anything about bubble sizes. Using a fully resolved, two-phase Lattice Boltzmann method, where the interface between gas and liquid is explicitly modeled, we look at uniformity of flow in sparged systems including the effects of gas and liquid interactions. We look at breakup and coalescence of gas bubbles based on gas flow rate and agitation in the fully . We compare this to Eulerian-Lagrangian models where the gas phase is modeled as spherical bubbles with breakup and coalesence kernels based on dimensional analysis, which have previously been shown to predict mass transfer coefficients between gas and liquid within about 20% of experimental results. We also test the ability of these models to predict gas flooding in a Rushton turbine. We show that capturing coalesence behavior is essential in predicting the power drop in an agitated system upon flooding.