Search

Positron emission particle tracking (PEPT) is a non‐invasive technique that can be used for following the trajectories of particles in fluidized beds, so increasing understanding of solids motion in fluidized bed processes. We describe how PEPT is applied, how its performance is optimized, and how trajectory information can be built up into instantaneous and time‐averaged measures of particle movement. Choices and pitfalls in data processing are explained and illustrated by reference to the travelling fluidized bed (TFB) collaboration initiated by Professor John Grace. [ABSTRACT FROM AUTHOR]

Gas adsorption is widely used in air pollution control, with mainly activated carbon and zeolites used as adsorbents. Although physical and chemisorption can be used, most air pollution applications involve physical adsorption, now also increasingly investigated for CO2 abatement from combustion gas. Empirical adsorption treatments have been presented since many decades, but solely rely on the comparison of adsorbate feed and exhaust concentrations of the adsorption bed. In-situ measurements, to study the absorbate/adsorbent interactions in real time, are compared in the present review when performed by a three-dimensional (3D) Positron Emission Tomography of an adsorbing 11CO2 radioactive tracer on activated carbon versus a zeolite adsorbent. The overall results are validated by conventional exit gas analysis. Results are defining both the time-dependent adsorption parameters, such as the progressing adsorption front and Mass Transfer Zone along the adsorbent bed length, and enable to assess previous semi-empirical adsorption correlations toward their optimum validity in predicting adsorption isotherms, kinetics and mechanisms. [ABSTRACT FROM AUTHOR]

Gas adsorption is widely used in air pollution control, with mainly activated carbon and zeolites used as adsorbents. Although physical and chemisorption can be used, most air pollution applications involve physical adsorption, now also increasingly investigated for CO2 abatement from combustion gas. Empirical adsorption treatments have been presented since many decades, but solely rely on the comparison of adsorbate feed and exhaust concentrations of the adsorption bed. In-situ measurements, to study the absorbate/adsorbent interactions in real time, are compared in the present review when performed by a three-dimensional (3D) Positron Emission Tomography of an adsorbing 11CO2 radioactive tracer on activated carbon versus a zeolite adsorbent. The overall results are validated by conventional exit gas analysis. Results are defining both the time-dependent adsorption parameters, such as the progressing adsorption front and Mass Transfer Zone along the adsorbent bed length, and enable to assess previous semi-empirical adsorption correlations toward their optimum validity in predicting adsorption isotherms, kinetics and mechanisms. [ABSTRACT FROM AUTHOR]

In dry granulation, fine cohesive powders are compacted into large multi‐particle entities, i.e., briquettes, flakes, or ribbons. The powder compaction is generally followed by milling, a size reduction process, which is crucial to obtain the desired granule size or properties. Abrasion and impact are two primary mechanisms of comminution in ribbon milling, but they are not completely understood. The aim of this article was hence to investigate numerically the fragmentation process induced by abrasion during ribbon milling. The discrete element method (DEM) was employed to simulate abrasion tests, for which three‐dimensional parallelepiped ribbons were generated using auto‐adhesive elastic spheres. The fragmentation rate, and the fragments size and number were determined for various surface energies and abrasive velocities. The DEM results showed that the mass‐equivalent fragment size distributions were bi‐modal, similar to the experimental observations and the numerical results for impact‐dominated ribbon milling reported in the literature. In addition, two quantities were determined from the DEM analysis, i.e., the number of large fragments and the fraction of fines, which was then integrated into the population balance models (PBM) so that a DEM–PBM multiscale modeling framework was developed to predict the granule size distribution during ribbon milling. The DEM–PBM results were compared with the experimental results reported in the literature, and a broad agreement was obtained, implying the proposed DEM–PBM can be used to analyse the ribbon milling behavior. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1191–1204, 2018 [ABSTRACT FROM AUTHOR]