Effect of particle hydrophilicity on the separation performance of a novel cyclone

Using water mist or vapor to help collect fine particles has been attracting increasing attention in separation and purification. A new fine particle separation technology which combines the centrifugal force field with the supersaturated vapor was recently proposed to realize the high collection efficiency of PM2.5 in gas cyclones. In this and similar technologies the interaction between particles and vapor is vital to the collection efficiency. Therefore, this paper investigated the effect of the dust hydrophilicity in such purification process. Six kinds of particles with different hydrophilicities were tested in the new cyclone. The overall and grade separation efficiencies were measured, which were significantly improved when the vapor was added, and the particles with better hydrophilicity showed a greater improvement. The improvement can be attributed to the particle growth in the supersaturated vapor and the gas flow in the cyclone, which were shown by the SEM analysis of the morphology change of the particles. Additionally, theoretical analysis shows that the nucleation rate and activation probability of heterogeneous condensation are both higher for the particles with better hydrophilicity, thus these particles should be easier to be activated as condensation nucleus and hence grow in size. Based on the condensational growth, an analytical model was established which can quantify the effect of hydrophilicity on the grade efficiency curve of the new cyclone.