Improving fluidization behavior of cohesive Ca(OH)2 adsorbent using hydrophilic silica nanoparticles: Parametric investigation

Abstract

Hydrophilic silica nanoparticles were used to enhance the fluidization behavior of Ca(OH)2 powder and its CO2 adsorption. The strong electrostatic forces were decreased by fluidizing adsorbents modified by hydrophilic SiO2 in the presence of alcohol vapors. A Taguchi experimental design was used to identify the optimal characteristic parameters of the modified adsorbents to improve their fluidization. Four parameters, including SiO2 mass percentage, type of alcohol, sieved size of SiO2, and sieved size of Ca(OH)2 particles, were selected for conducting experiments in a fluidized bed. Analysis of variance showed that sieved size and mass percentage of SiO2 nanoparticles (accounting for 73.88% and 19.01% of the total contributions, respectively) were the most significant parameters determining fluidization quality of the modified adsorbents. Fluidization experiments confirmed the effectiveness of these two parameters. Based on bed expansion results, fluidization of Ca(OH)2 modified by hydrophilic silica nanoparticles in the presence of alcohols was considerably better than that modified by hydrophobic nanoparticles. CO2 adsorption tests, which were carried out by measuring the pH variation of pure water during adsorption, revealed that improved Ca(OH)2 fluidization enhanced the carbonation reaction.