(194f) Extraction of Particle-Scale Cohesion Parameters from Straightforward Bulk Measurements

Inter-particle cohesion significantly affects the flow behavior of particulate and multiphase systems. Therefore, accurate prediction of inter-particle cohesion is crucial for efficient design and optimization of various industrial unit operations. The state-of-the-art methods to develop cohesion models rely on atomic force microscopy analysis of individual particle surface under specific humidity conditions, which are time consuming, expensive and require specialized training. These methods are not conducive to an industrial setting where feedstock and ambient conditions change frequently. Therefore, exploring possible methods to extract inter-particle cohesion from straightforward bulk measurements is desired. In recent work carried out by Liu et al.[1], defluidization is identified as one example of a bulk behavior that can provide particle-level cohesion. In their work, a simplified square-force cohesion model is proposed, and with the help of discrete element method (DEM) simulations, it is demonstrated that the parameters for the square-force model can be extracted from the defluidization (pressure drop) curve. This defluidization-based approach is restricted to lightly cohesive particles since more cohesive particles result in an erratic defluidization curve. In this work, a similar approach is taken for more cohesive particles – i.e., a system with energy added in order maintain smooth defluidization, namely a rheometer with a rotating geometry, is utilized on particles with mild to moderate levels of cohesion [2]. Additionally, the rheometer can operate with fewer particles, such that corresponding DEM simulations as needed for square-force parameter extraction, is computationally feasible. To accurately extract the inter-particle cohesion parameters, the measured values of the other particle-scale properties (e.g., coefficient of friction, coefficient of restitution) were used as inputs to the DEM simulations. Finally, the same particles were used in a separate experimental system in order to test the validity of square-force model parameters outside of the system from which they were extracted.

[1] P. Liu, C.Q. LaMarche, K.M. Kellogg, C.M. Hrenya, A square-force cohesion model and its extraction from bulk measurements, AIChE Journal. 82 (2018) 1156–11. doi:10.1002/aic.16089.

[2] I. Mishra, P. Liu, A. Shetty, C.M. Hrenya, On the use of a powder rheometer to probe defluidization of cohesive particles, Chem Eng Sci. 214 (2020) 115422. doi:https://doi.org/10.1016/j.ces.2019.115422.