Capillary force between two micron-sized particles bound by a convex liquid bridge in agglomeration for atmospheric environmental protection

Fine particles are agglomerated by calcium-based solution in Wet flue gas desulphurisation (WFGD) system for atmospheric environmental protection. The agglomeration of micron-sized particles bound by a convex liquid bridge is common in WFGD, in which the capillary force plays a key role. However, research on capillary force and liquid bridge stretching process is insufficient, especially for unequal sized particles in particles removing. An arc liquid bridge model was adopted between equal or unequal micron-sized spherical particles to calculate the capillary force comprising wetting and Laplace forces. Then, we obtained the curve of the forces between particles wetted by deionised water or water with surfactant from particle contact to zero capillary force. The study results showed that the stretching distance decreased with the liquid bridge volume, which is the key factor determining the stretching distance in the calculated range. The wetting force was found to be attractive or repulsive depending on the liquid bridge volume, while the Laplace and capillary forces were always repulsive. A smaller particle size limited the size of liquid bridge volume and capillary force.