(627d) Continuous Emulsification in 3DP Fixed Beds: Drop Size Distribution and Emulsification Efficiency

Multiphase processes are important in a wide range of industries, including cosmetics and consumer products, automotive and petrochemicals, and fine chemicals and pharmaceuticals. Process intensification, PI, is a framework of improving the efficiency and reducing waste of processes, ranging in scope from a single unit operation to entire processes. A key principle in PI is to provide molecules with the same process experience. Multiphase processes present numerous challenges in accomplishing a uniform process experience; continuous processing is one approach used to address these challenges. Nearly all approaches that leverage continuous processing encounter issues that arise from the hydrodynamics associated with a unit operation. Therefore, it is advantageous to consider strategies that seek to optimize the hydrodynamics.

Different applications in multiphase processing require customization. One approach to customizing device hydrodynamics is the use of additive manufacturing (AM). A distinct advantage to AM is that it affords nearly independent variation of the geometric parameters of a design. Therefore, using AM, it should be straightforward to customize the hydrodynamics of a unit operation.

We built and tested fixed bed reactors capable of dispersing two immiscible phases using three dimensional printing (3dP). We characterized the hydrodynamics of these reactors in emulsification operations using pressure drop, drop size distribution, residence time distribution, and computed properties such as tortuosity and dispersion efficiency.

We establish key relationships among fixed bed design variables and process performance metrics. In emulsification operations, other factors such as the concentration of emulsifying agent, oil to water volume ratio, and total volumetric flow rate also play a role. In this study, we report the effect of bed internal geometry and void fraction on emulsification efficiency and dispersion drop size distribution.

As expected, the lower the void fraction, the higher the pressure drop and the smaller average drop size, see Figure 1. Total volumetric flow rate showed a similar trend. Although the residence time distribution in single phase flow through the 3dP fixed bed is uniform, multiphase flow results in non-uniform distributions. Fixed bed geometry was found to have a large effect on the capacity of the fixed bed to disperse one phase into another. Some geometries were shown to be prone to channeling resulting in extremely low pressure drops and no recognizable emulsification. Oil to water volume ratio showed little effect on parameters such as pressure drop and drop size distribution, see Figure 2. We discuss a balance of heuristic design principles and a quantitative modeling frameworks to guide the design of fixed beds for dispersing one liquid into another.