Experimental and molecular dynamics study of particles removal in the effect of heterogeneous condensation agglomeration enhanced by surfactants

Heterogeneous condensation agglomeration is a promising pretreatment technology for enlarging fine particles, which is helpful to enhance the particle removal capacity of conventional equipment. The interaction between water vapor and particles is a significant factor influencing the enhancement effect. In this study, two kinds of particles with different surface wettability and three types of surfactants were applied to study the effect and mechanism of particles removal in the surfactant enhanced heterogeneous condensation agglomeration. The experiment was carried out based on CAP system in which the cyclone was enhanced by heterogeneous condensation agglomeration. The results show that SiO2-OH particles with better wettability had better removal effect than SiO2-CH3 particles. Adding surfactant can promote the condensational growth and agglomeration of particles by promoting the wetting effect between water vapor and particles, thereby increasing the removal efficiency. The improvement effect is influenced by particle surface properties and surfactant types. Cationic surfactant CTAB is most effective for SiO2-OH particles, while nonionic surfactant OP-10 is most effective for SiO2-CH3 particles. Wettability modification was investigated by molecular dynamics simulations, and the results shows that as a result of the different polarity of the surface functional groups, the strong electrostatic interaction is dominated between SiO2-OH and water, while the weak van der Waals interaction between SiO2-CH3 and water is the dominant. The head group of CTAB can form strong electrostatic interaction with SiO2-OH surface, while the long tail chain of OP-10 is adsorbed on SiO2-CH3 particles through van der Waals interaction, leading to the reduce of solid-liquid interaction energy and improves the wetting effect of water on particle. This work is beneficial for selecting suitable surfactant for heterogeneous condensation agglomerations technology.