ABSTRACT
The Chapter describes the basics and process of green pelletization, which is executed in a drum/disc pelletizer. The driving force, mechanism involved, and stages pertaining to the formation of green balls, first nuclei on addition of water, and their growth due to collision on rolling are outlined. The significance of moisture in seed formation and ball growth is briefed. Different states of saturation in liquid bonded granules are schematically shown. The capillary force theory for wet agglomerate strength in particulate systems and the relationship for the tensile strength is derived as a function of the voids filled by binder liquid. The viscosity effect added by binder gains its importance once the green pellets are dried. The Chapter mentions the binding mechanism in dried pellets that is being facilitated by a combination of the capillary force and cohesive force at low binder dosage. The strength of the superficial network, growth rate, the elastic and plastic deformation of green pellets, and their dependence on (binder liquid) viscosity are outlined, The Chapter describes the property requirements of the binder, bentonite, as the binder and its characteristics, including ball-ability, activation, and substitution. The mechanism and stages of the agglomerate formation, their growth, kinetics, and governing equations, are described. The characteristic S-shaped curve is obtained when the diameter of pellets is plotted against the time. The Chapter also gives an outline on the process and operational variables, such as the speed of the pelletizing disc and its inclination, which influences the ball growth and agglomerate strength.
