Effect of Needle-Like Crystal Shape on Measured Particle Size Distributions

The effect crystal morphology has on measured particle size distributions (PSDs) is explored, with a focus on particles exhibiting a needle-like habit. An idealized in silico study was performed, targeted at modeling the measurement principles of various particle sizing devices, namely laser diffraction, Coulter counter, focused beam reflectance measurement, a single and a dual projection imaging devices. The evolution of a crystal population is measured, allowing for an evaluation of the introduced biases. Further, the consequences of these biases are highlighted by demonstrating how the real growth mechanism may be incorrectly interpreted depending on the chosen particle sizing technique. It is found that techniques which utilize a one-dimensional PSD are incapable of simultaneously describing the concentration profile and average length; in contrast, imaging techniques are able to reproduce both quantities. Finally, the dual projection imaging device is shown to be the only instrument to yield a nearly bias-free measurement. (C) 2016 American Institute of Chemical Engineers