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Monitoring the Dynamics of Concentrated Suspensions by Enhanced Backward Light Scattering
Author(s) -
Spicer Patrick T.,
Pratsinis Sotiris E.,
Willemse Alexander W.,
Merkus Henk G.,
Scarlett Brian
Publication year - 1999
Publication title -
particle and particle systems characterization
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.877
H-Index - 56
eISSN - 1521-4117
pISSN - 0934-0866
DOI - 10.1002/(sici)1521-4117(199910)16:5<201::aid-ppsc201>3.0.co;2-h
Subject(s) - flocculation , coagulation , particle size , chemistry , steady state (chemistry) , shear rate , particle (ecology) , chemical engineering , materials science , chromatography , rheology , composite material , psychology , oceanography , organic chemistry , psychiatry , engineering , geology
The shear‐induced flocculation of kaolin‐polymer flocs in a stirred tank is investigated at medium to high solids concentrations (ϕ=1−10% w/w). The evolution of the average floc size is monitored by the change in intensity of laser light scattered in the 180° direction. The measurements reflect the change in particle number concentration as flocculation proceeds. As flocculation begins, coagulation dominates and the floc size increases (total particle number decreases) and then levels off at a steady state value as fragmentation becomes significant and balances coagulation. At steady state, the measurements indicate the extent of flocculation. Increasing the shear rate increases the coagulation and fragmentation rates, resulting in smaller floc sizes at steady state. Increasing the flocculant concentration increases the steady state floc size by strengthening the bonds between primary particles to resist fragmentation. At constant shear rate and flocculant concentration, increasing the solids fraction decreases the steady state floc size indicating formation of weakly bonded flocs. Flocculant mixing was the most important factor for flocculation efficiency at high solids concentrations.