Laminar and turbulent shear-induced flocculation of fractal aggregates

system in a stirred tank are compared to the model results. Good agreement is found for both aerage-size eolution and steady-state size distribution using only one fitting para- () meter and assuming binary breakage. The aerage polystyrene-Al OH aggregate size 3 initially increases before reaching a constant steady-statealue during coagulation) fragmentation in a stirred tank. Increasing the applied shear rate increases the coagula- tion and fragmentation rates, decreasing the steady-state aerage aggregate size, and the time lag before steady state. The model deeloped in this work is applied to laminar shear data from the literature, showing excellent agreement.

[1]  R. J. François.  Strength of aluminium hydroxide flocs , 1987 .

[2]  Benoit B. Mandelbrot,et al.  Fractal Geometry of Nature , 1984 .

[3]  P. Saffman,et al.  On the collision of drops in turbulent clouds , 1956, Journal of Fluid Mechanics.

[4]  M. Smoluchowski.  Versuch einer mathematischen Theorie der Koagulationskinetik kolloider Lösungen , 1918 .

[5]  Patrick T. Spicer,et al.  Coagulation and fragmentation: Universal steady‐state particle‐size distribution , 1996 .

[6]  Bruce E. Logan,et al.  Fractal dimensions of aggregates determined from steady-state size distributions , 1991 .

[7]  S. Pratsinis,et al.  Effect of shear schedule on particle size, density, and structure during flocculation in stirred tanks , 1998 .

[8]  U. Baltensperger,et al.  Scaling behaviour of physical parameters describing agglomerates , 1990 .

[9]  Mark R. Wiesner,et al.  Kinetics of aggregate formation in rapid mix , 1992 .

[10]  Karel Antonius Kusters,et al.  The influence of turbulence on aggregation of small particles in agitated vessels , 1991 .

[11]  W. Russel,et al.  Structure and breakup of flocs subjected to fluid stresses: II. Theory , 1987 .

[12]  Robert M. Ziff,et al.  On the stability of coagulation--fragmentation population balances , 1989 .

[13]  P. Adler.  Heterocoagulation in shear flow , 1981 .

[14]  David G. Thomas.  Turbulent disruption of flocs in small particle size suspensions , 1964 .

[15]  D Dirk Thoenes,et al.  Aggregation kinetics of small particles in agitated vessels , 1997 .

[16]  R. Probstein,et al.  The Effect of Coalescence on the Average Drop Size in Liquid-Liquid Dispersions, , 1976 .

[17]  Ica Manas-Zloczower,et al.  The influence of structural heterogeneities on the cohesivity and breakup of agglomerates in simple shear flow , 1992 .

[18]  A. A. Potanin.  On the mechanism of aggregation in the shear flow of suspensions , 1991 .

[19]  N. Tambo.  Physical aspect of flocculation process—I: Fundamental treatise , 1979 .

[20]  R Hogg,et al.  Effects of flocculation conditions on agglomerate structure , 1986 .

[21]  Benoît B. Mandelbrot,et al.  Die fraktale Geometrie der Natur , 1987 .

[22]  Motion and Rupture of a Porous Sphere in a Linear Flow Field , 1979 .

[23]  W. Russel,et al.  SIMULATIONS OF COAGULATION IN VISCOUS FLOWS , 1991 .

[24]  S. Pratsinis,et al.  Shear-induced flocculation: The evolution of floc structure and the shape of the size distribution at steady state , 1996 .

[25]  M. Hounslow,et al.  A discretized population balance for nucleation, growth, and aggregation , 1988 .

[26]  V. Oles.  Shear-induced aggregation and breakup of polystyrene latex particles , 1992 .

[27]  P. Adler.  Streamlines in and around porous particles , 1981 .

[28]  W. Russel,et al.  Structure and breakup of flocs subjected to fluid stresses: I. Shear experiments , 1986 .

[29]  Norihito Tambo,et al.  Physical characteristics of flocs—I. The floc density function and aluminium floc , 1979 .

[30]  Joseph R. V. Flora,et al.  Floc restructuring in varied turbulent mixing , 1991 .