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

摘要

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