(104a) Strategies to Establish Mechanistic Liquid Transport Models for Wet Granular Matter

Johannes G. Khinast and Stefan Radl

Wet granular matter plays a significant role in both nature and industry. Unfortunately, these materials are intrinsically hard to model due to the fact that three phases interact. Examples documenting these challenges are (i) the counter-intuitive fluid depletion in sheared granular materials,¹ or (ii) the spontaneous formation and growth of agglomerates in wet fluidized beds.² Relevant phenomena arise due the interplay of (i) liquid-particle interactions (e.g., the redistribution of liquid on particles), (ii) particle-particle collisions (i.e., aggregation and separation dynamics³), and (iii) heat and mass transfer (i.e., evaporation of liquid).

We summarize recent advances related to the above phenomena, and that ultimately aim on predicting the amount of liquid adhering to individual particles. Specifically, in Part I we discuss experimental routes, focusing on the observation of individual liquid-particle interactions. In Part II, modeling strategies are discussed, including (i) sub-particle-scale models (i.e., models on the droplet and pore scale), (ii) inter-particle models necessary to describe clustering and aggregation dynamics (a focus will be on bridge filling models^4,5), as well as (iii) equipment scale models that account for evaporation and heat exchange⁶ in industrially-relevant devices. Part III is devoted to simulation strategies that are needed to solve the model equations. Specifically, topics related to (i) improving numerical schemes (e.g., the voidage calculation algorithm), as well as (ii) improving the speed of calculations (e.g., by using multi-core CPU clusters or graphics processing units) are discussed.

Finally, we provide an outlook, focusing on advanced sub-particle-scale models that consider the liquid morphology on individual particles. Also, we summarize the most recent activities in the field by providing a tentative regime map for liquid transport rates in wet granular matter. This map is thought to be useful for predicting the behavior of wet fluidized beds without a rigorous model or simulation. Extensions to large-scale systems and simulations by our groups are shown as well.

References

1. Mani, R. A., Kadau, D., Or, D. & Herrmann, H. J. Fluid depletion in shear bands. Phys. Rev. Lett. 109, 248001 (2012).

2. Boyce, C. M. et al. Growth and Breakup of a Wet Agglomerate in a Dry Gas-Solid Fluidized Bed. AIChE J. 63, 2520–2527 (2017).

3. Donahue, C. M., Davis, R. H., Kantak, A. A. & Hrenya, C. M. Mechanisms for agglomeration and deagglomeration following oblique collisions of wet particles. Phys. Rev. E - Stat. Nonlinear, Soft Matter Phys. 86, 21303 (2012).

4. Wu, M., Khinast, J. G. & Radl, S. The Effect of Liquid Bridge Model Details on the Dynamics of Wet Fluidized Beds. AIChE J. submitted, (2017).

5. Mohan, B., Kloss, C., Khinast, J. G. & Radl, S. Regimes of Liquid Transport through Sheared Beds of Inertial Smooth Particles. Powder Technol. 264, 377–395 (2014).

6. Askarishahi, M., Salehi, M. & Radl, S. Full-Physics Simulations of Spray-Particle Interaction in a Bubbling Fluidized Bed. AIChE J. 63, 2569–2587 (2017).