A comprehensive model was derived based on the balance between drag, collision, and gravity as separation and van der Waals and hydrogen bond as adhesion forces to estimate the equilibrium size of agglomerates formed during the fluidization of nanoparticles. Due to the approximately less than 9% of the total amount of forces, drag and collision forces were not considered in the final model. Also, the influence of using the vapor of different alcohols on the fluidization behavior of hydrophilic silica and alumina nanoparticles was studied by experiments. To justify the improving effect of using alcohols, the electrostatic repulsion force was added to the model for the first time. Methanol and 2-propanol were the most effective alcohols on fluidization improvement, and consequently the smallest size of agglomerates was estimated using physical properties of these two alcohols. The Richardson–Zaki (R-Z) analysis indicated that the fluidization degree of cohesive hydrophilic nanoparticles can be greatly improved by adding polar alcohols to the system. The agglomerate sizes predicted based on R-Z showed a good agreement with the calculated ones by model in the presence of alcohols.

As a low-cost method, hydrophilic SiO2 nanoparticles (NPs) and fluid catalytic cracking (FCC) coarse particles were used as assistant materials to improve the fluidity of Al2O3 and TiO2 hard-to-fluidize nanopowders. To decrease the strong electrostatic forces between the hydrophilic nanopowders, prepared samples were fluidized in the presence of methanol vapor. Results revealed that the amount of SiO2 NPs, increased from 5 to 50 wt. %, has a beneficial effect on the fluidization quality of the binary (hard-to-fluidize NPs + SiO2) and ternary (hard-to-fluidize NPs + SiO2 + FCC) mixtures. However, the amount of FCC particles when it varied from 15 to 30 wt. % in the ternary mixtures should meet the optimal point, beyond which the fluidization quality was declined due to the segregation phenomenon. The laboratory results showed that the cost-effective ternary samples fluidized more homogeneously with higher bed expansions compared to the binary samples. In this regard, (Al2O3 + 20 wt. % SiO2) + 15 wt. % FCC and (TiO2 + 20 wt. % SiO2) + 15 wt. % FCC ternary samples were proposed as the alternatives of Al2O3 + 50 wt. % SiO2 and TiO2 + 50 wt. % SiO2 binary mixtures, respectively.

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