Abstract: Applying the liquid bridge theory,the physical law and variation of velocity with granule＇s distance in the separation process of wet granules are investigated. Velocity condition for the separation of wet granules has been presented from the view of dynamics. It has been found that separation movement of wet granules causes the stretch of liquid bridge and separation velocity decreased rapidly with the enlargement of granule surface distance. If the separation velocity of granule decays to zero before the rupture of liquid bridge,separation can not happen. Separation needs a critical normal initial velocity. Employing 4 /5 order of Runge- Kutta- Fehlberg arithmetic,initial velocities of 100 types of wet granules needed in the separation are calculated and listed,which can be loaded to wet granules by collision,vibration or pneumatic components in industry. The major reason why the separation of wet granule gets difficult with increasing moisture lies in the hard rupture of liquid bridge,not in increasing liquid force as widely believed.

Key words: granular materials, kinetic theory, algorithm, separation, powder technology