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This study employs the discrete element method (DEM) to investigate the impact of the widths of lognormal particle size distributions (PSDs) with the same mean particle diameter on hopper discharge behaviors, namely, discharge rate, particle velocities, and size‐segregation. Results reveal that (i) the hopper discharge rate decreases as PSD width increases; (ii) the mean discharge rates are constant with time, but the fluctuations increase as the PSD width increases; (iii) the overall size‐segregation increases with PSD width; (iv) the overall mean particle diameters of the narrower PSDs do not exceed the initial mean of 5 mm, whereas that of wider ones do; (v) the relationship between PSD width and particle velocities is non‐monotonic with no consistent trends; and (vi) no direct correlation exists between particle velocity and size‐segregation. The results here provide valuable insights on the behavior of the prevalent polydisperse mixtures in hoppers. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1174–1190, 2018

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In recent years, the solution enhanced dispersion in supercritical fluids (SEDS) technique is widely applied to produce fine and small particles of drugs and other active ingredients. However, this technique still cannot be used to generate particles in the submicrometer range for specific compounds, such as carotenoids. In this study, a modified SEDS technique is explored and applied in the preparation of β-carotene nanoparticles with relatively narrow size distribution. This novel technique, termed SEDS-EM, combines a traditional SEDS technique with ultrasonication from the supercritical antisolvent with enhanced mass transfer precipitation technique (SAS-EM). For this new technique, the β-carotene solution is premixed with the antisolvent (supercritical CO 2 ) in a coaxial nozzle; then the mixed solution is sprayed from the coaxial nozzle onto a surface vibrating at an ultrasonic frequency. The solution jet is dispersed by the coaxial nozzle and further atomized into very small droplets by the ultrasonic vibrating surface. This combination of a coaxial nozzle and the ultrasound field enhances the mass transfer between the solution and the antisolvent. The resultant β-carotene particles decreased in size from the micrometer range (2À5 μm) by SEDS to the nanometer range (20À205 nm) by SEDS-EM. This smaller particle size can be controlled by the power supplied from the attached ultrasound transducer utilized in SEDS-EM. The size and morphology of the particles are observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The effects of the process parameters on the β-carotene yield are discussed. The crystallography transformation of the processed and unprocessed β-carotene is characterized by XRD and FTIR. The particle precipitation in sub and near critical regions of the DCM-CO 2 binary system is also discussed.

Despite the advancement on the understanding on the unwelcome phenomenon of hopper jamming, the influence of the particle‐size distribution (PSD) width of the ubiquitous continuous PSDs remains unknown. Accordingly, this study investigated using discrete element method a range of PSD widths (10%≤σ/μ≤50%) of lognormal PSDs with a constant mean particle diameter of 10 mm in a three‐dimensional hopper. Results indicate that, although the monodisperse particles of 10 mm diameters do not jam, the wider PSDs (σ/μ≥30%) jam. The flatter arches and higher mass‐averaged force that are linked to the denser packing of wider PSDs underlie the propensity to jam. To reduce the jamming probability, the friction coefficient and initial fill height can be reduced, but not changes in particle density. The results here highlight that the mean particle diameter alone is an insufficient parameter to predict jamming and the impact of PSD width is non‐negligible. © 2018 American Institute of Chemical Engineers AIChE J, 65: 512–519, 2019