Modeling the size of hydrophilic nanoparticles during fluidization with emphasis on the role of vapor of polar materials

In this study, a comprehensive force balance model is developed to estimate the equilibrium size of agglomerates formed during the fluidization of nanoparticles with considering the importance of hydrogen bond, van der Waals and gravitational forces. Also, the influence of vapor of different polar materials (including methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol and ammonia) on the size of hydrophilic silica nanoagglomerates and consequently their fluidization behavior is studied by experiments in a gas-solid fluidized bed. The results show that using vapor of these polar materials (with hydroxyl groups in their formula) improves the fluidization behavior of hydrophilic silica nanoparticles significantly and results in a higher bed expansion. To justify the improving effect of different vapor of polar materials on fluidization behavior, the electrostatic repulsion force is added to the model and size of agglomerates are calculated in the presence of this force. It is obtained that the results of model are in good agreement with the experimental observations, so that, among all used materials methanol, 2-propanol and ethanol have the most effective impact on fluidization improvement and the smallest size of agglomerates is estimated using physical properties of these three alcohols as well. Finally, the size of agglomerates calculated by the model shows error less than 11% compared with the size of agglomerates measured experimentally by laser. This error is lower than the previous reported ones in the literature.