(358c) Fundamental Prediction of Agglomeration and Entrainment Rates for Cohesive Powders in a Riser Flow

Predictions of entrainment rates of non-cohesive powders in fluidized bed systems given by empirical models can vary by several orders of magnitude for a given system (Chew et al 2015). For flows of cohesive particles, agglomerates can form and break, leading to further uncertainty in the entrainment rate. In this work, a fundamental approach is used to predict the agglomerate fraction and entrainment rate. Specifically, the population balance is coupled with kinetic theory balances. This new continuum framework utilizes fundamental closures for the birth and death rates due to aggregation and breakage in the population balance (Kellogg et al 2017). These novel closures take into account the effect of impact velocity (granular temperature) on the outcome of a collision as agglomeration, rebound, or breakage. Here, the agglomerate fractions and entrainment rates predicted by the new continuum framework are compared to discrete element method (DEM) simulations. The effect of the critical velocity of aggregation (cohesive energy) and the solid volume fraction on the agglomerate fraction and entrainment rate are explored. Preliminary comparisons with experiments will also be discussed.

Chew, J.W., Cahyadi, A., Hrenya, C.M., Karri, R. and Cocco, R.A., 2015. Review of entrainment correlations in gas–solid fluidization. Chemical Engineering Journal, 260, pp.152-171.

Kellogg, K.M., Liu, P., LaMarche, C.Q. and Hrenya, C.M., 2017. Continuum theory for rapid cohesive-particle flows: general balance equations and discrete-element-method-based closure of cohesion-specific quantities. Journal of Fluid Mechanics, 832, pp.345-382.