Elucidation of mass transfer mechanisms in pellet formation by spheronization

2021 ◽  
Vol 160 ◽  
pp. 92-99
Author(s):  
Maria Evers ◽  
Amelie Mattusch ◽  
Dominik Weis ◽  
Edwin Garcia ◽  
Sergiy Antonyuk ◽  
...  
AIChE Journal ◽  
2016 ◽  
Vol 63 (6) ◽  
pp. 2394-2408 ◽  
Author(s):  
Matthieu Roudet ◽  
Anne‐Marie Billet ◽  
Sébastien Cazin ◽  
Frédéric Risso ◽  
Véronique Roig

Author(s):  
Irina V. Alexandrova ◽  
Dmitri V. Alexandrov ◽  
Eugenya V. Makoveeva

The Ostwald ripening stage of a phase transformation process with allowance for synchronous operation of various mass transfer mechanisms (volume diffusion and diffusion along the block boundaries and dislocations) and the initial condition for the particle-radius distribution function is theoretically studied. The initial condition is taken from the analytical solution describing the intermediate stage of a phase transition process. The present theory focuses on relaxation dynamics from the beginning of the ripening process to its final asymptotic state, which is described by the previously constructed theories (Slezov VV. et al. 1978 J. Phys. Chem. Solids 39 , 705–709. ( doi:10.1016/0022-3697(78)90002-1 ) and Alexandrov & Alexandrova 2020 Phil. Trans. R. Soc. A 378 , 20190247. ( doi:10.1098/rsta.2019.0247 )). An evolutionary behaviour of particle growth rates dependent on various mass transfer mechanisms and time is analytically described. The boundaries of the transition layer, which surround the blocking point, are found. The fundamental and relaxation contributions to the particle-radius distribution function are derived for the simultaneous occurrence of various mass transfer mechanisms. The left branch of this function is shifted to smaller particle radii whereas its right branch extends to the right of the blocking point as compared with the asymptotic universal distribution function. The theory under consideration well agrees with experimental data. This article is part of the theme issue ‘Transport phenomena in complex systems (part 1)’.


1985 ◽  
Vol 17 (8) ◽  
pp. 1469-1471
Author(s):  
H. Siegrist ◽  
W. Gujer

The diffusion coefficient of three different chemical species in naturally grown, heterotrophic biofilms have been measured. The mechanical structure of the biofilm matrix reduces the molecular diffusion to about 50 to 60 % of the value in pure water. Depending on the roughness of the biofilm surface and the flow conditions eddy diffusion increased the mass transfer into the biofilm near the surface. The influence of the diffusion potential and the donnan potential on the ions have been evaluated by comparing the diffusion coefficients of a positively and negatively charged ion and a neutral molecule in experiments with different background electrolyte concentrations. Mass transfer effects by electrostatic forces are negligible at the ionic strength of waste water and tap water.


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