Regime Map of Fluidization for Cohesive Powders: A Two-Fluid-Model Study

The fluidization behavior of cohesive powders was investigated using the Two-Fluid Model (TFM) approach. The aim was to obtain the regime map of fluidization through particle cohesivity for the first time. The particle cohesion has been expressed in terms of the Bond number and the tensile pressure prefactor. The particle cohesivity was modeled through the modified solids’ rheology presented by Gu et al. J. Fluid Mech. 2019. To obtain the fluidization regime, we then conducted a set of simulations for the particle cohesion levels for the particle size of 148 and 300 μ m and the fluidization number in the range of 2 − 5 . Our simulation results demonstrated the formation of five regimes, namely, i) bubbling regime, ii) bubbling-clustering regime, iii) dense-emulsion/clear-bubbling regime, iv) bubbleless expansion, and v) stationary/channeling regime. These regimes can be quantitatively demarcated via the cumulative distribution of solids’ shear-to-yield stress ratio. It was also revealed that the cumulative distribution of instantaneous solids volume fraction is a good indicator for identifying the fluidization regimes. We extended our previous regime map by extracting the dense emulsion with clear bubbling regime from bubbling-clustering regimes in its border with the stationary//channeling regime. This regime features a high solid volume fraction in the emulsion phase, and clear bubbles without any clusters inside. Our simulation results also revealed that threshold values for the demarcation of the fluidization regime are independent of the particle size and fluidization velocity. However, increasing the particle size and fluidization velocity reduces the bubbleless expansion and stationary/channeling regime, while expanding the bubbling and dense emulsion/clear bubbling regime. On the other hand, particle size and fluidization velocity have opposite effects on the bubbling-clustering regime: this regime shrinks with a rise in particle size and a drop in fluidization velocity. The analysis of solids volume fraction also revealed that increasing the Bond number reduced the bubble size in the bubbling regime, while increasing the bubble size in the bubbling-clustering regime. • Two-Fluid Modeling (TFM) of cohesive fluidized bed using modified solids rheology • Regime map of cohesive fluidized bed using TFM approach • Quantifying the regimes via shear-to-yield stress ratio independent of particle size • Instantaneous solids volume fraction cumulative distribution indicates regime map • Dense emulsion phase with clear bubbles is identified at high cohesivities