An investigation into the effects of time and shear rate on the spreading of liquids in coating and granulation processes

摘要

A series of experiments was performed to determine the effects of mixing rate, mixing time, and liquid iscosity on the spreading of a liquid binder on to the surfaces of sugar (nonpareil) particles. The particles were initially coated with a layer of anhydrous magnesium sulfate to absorb the water from the aqueous solutions of PEG (poly ethylene glycol) 4000 that was used as the model binder solution. A blue dye was used as a visual marker of the binder solution. The distribution of the binder on the batch of particles was found to be independent of the mixing time (10 to 80 s) for the three mixing speeds (600, 900, and 1,200 rpm). For the high viscosity binder (50% PEG 4000, mu ～ 100 cP) the mixing speed was found to affect the RSD (relative standard deviation) of the distribution of binder on the particles. The RSD was unaffected by the binder viscosity for the highest mixing time. The mass of agglomerated material was found to decrease with the mixing time, mixing speed, and with decreasing viscosity of the liquid binder solution.