SOLIDS DISTRIBUTION IN STIRRED SLURRY REACTORS: INFLUENCE OF SOME MIXER CONFIGURATIONS AND LIMITS TO THE APPLICABILITY OF A SIMPLE MODEL FOR PREDICTIONS

Abstract The features of solids concentration distribution were investigated in baffled and unbaffled tanks of high aspect ratio, stirred with multiple radial, mixed-flow or axial impellers. In the baffled tanks the average profiles can be predicted with the sedimentation-dispersion model regardless of impeller type - in spite of slight systematic departures from the average trend at the impeller plane and/or midway between the impellers. This is hardly possible for the unbaffled tanks due to lack of physical foundation of this simple model. When the unbaffled tank is stirred with hydrofoil impellers, an inverted profile is even obtained. The mentioned departures and this last anomalous behaviour are qualitatively discussed with reference to particle-turbulence interaction.

[1]  R. King,et al.  Fluid mechanics of mixing : modelling, operations, and experimental techniques , 1992 .

[2]  Giorgio Micale,et al.  CFD Simulation of Particle Distribution in a Multiple-impeller High-Aspect-Ratio Stirred Vessel , 2000 .

[3]  John B. Shoven,et al.  I , Edinburgh Medical and Surgical Journal.

[4]  Franco Magelli,et al.  Solids concentration distribution in slurry reactors stirred with multiple axial impellers , 1991 .

[5]  Jamshid M. Nouri,et al.  Particle velocity characteristics of dilute to moderately dense suspension flows in stirred reactors , 1992 .

[6]  František Rieger,et al.  Distribution of solid particles in a mixed vessel , 1990 .

[7]  Vladimír Kudrna,et al.  Stochastic model of the flow mechanically stirred solid-liquid system , 1980 .

[8]  G. Zhou,et al.  Distribution of Energy Between Convective and Turbulent-Flow for 3 Frequently Used Impellers , 1996 .

[9]  H. A. Nasr-El-Din,et al.  Local solids concentration measurement in a slurry mixing tank , 1996 .

[10]  M. F. Edwards,et al.  Mixing in the process industries , 1985 .

[11]  Petr Kadlec,et al.  Distribution of energy dissipation rate in an agitated gas-liquid system , 1993 .

[12]  Vladimír Rod,et al.  Concentration distribution of suspension in a mixed vessel , 1978 .

[13]  Ivan Fořt,et al.  A probability form of the diffusion equation and its use to describe the distribution of the solid phase particle concentrations in a mechanically agitated charge , 1986 .

[14]  Michael Yianneskis,et al.  Hydrodynamic characteristics of dual Rushton impeller stirred vessels , 1996 .

[15]  Yoshinobu Morikawa,et al.  LDV measurements of an air-solid two-phase flow in a vertical pipe , 1984, Journal of Fluid Mechanics.

[16]  H. G. Schwartzberg,et al.  Fluid and Particle Motion in Turbulent Stirred Tanks. Particle Motion , 1968 .

[17]  Kei Miyanami,et al.  Solids suspension in mixing tanks , 1982 .

[18]  P. Shamlou,et al.  Solids suspension and distribution in liquids under turbulent agitation , 1989 .

[19]  M. Nocentini,et al.  Solid distribution in vessels stirred with multiple impellers , 1990 .

[20]  Sanjoy Banerjee,et al.  Particle behavior in the turbulent boundary layer. II. Velocity and distribution profiles , 1995 .

[21]  A. Brucato,et al.  Particle drag coefficients in turbulent fluids , 1998 .

[22]  John R. Fessler,et al.  Preferential concentration of heavy particles in a turbulent channel flow , 1994 .

[23]  M. Nocentini,et al.  Solid Distribution in Slurry Reactors Stirred with Multiple Impellers: Continuous Flow Systems , 1992 .

[24]  J. Davies,et al.  Particle suspension and mass transfer rates in agitated vessels , 1986 .

[25]  K. Riet,et al.  The behaviour of gas—liquid mixtures near Rushton turbine blades , 1973 .

[26]  R. Kuboi,et al.  Fluid and particle motion in turbulent dispersion—II , 1974 .

[27]  J. C. Godfrey,et al.  CFD Simulation of Particle Distribution in Stirred Vessels , 2000 .

[28]  A. Barresi,et al.  Solid dispersion in an agitated vessel , 1987 .

[29]  M. Bohnet.  Distribution of Solids in Stirred Suspensions , 1980 .

[30]  Alberto Brucato,et al.  An application of the network-of-zones model to solids suspension in multiple impeller mixers , 1991 .

[31]  Michel Cournil,et al.  Solid Particles Concentration Profiles in an Agitated Vessel , 1999 .

[32]  O. Levenspiel,et al.  A short note on the drag correlation for spheres , 1986 .

[33]  R. Clift,et al.  Bubbles, Drops, and Particles , 1978 .

[34]  N. I. Heywood,et al.  A Comparison of the Efficiency of Five Agitator Designs for Solids Suspension Duties at High Solids Concentrations , 1992 .

[35]  Gary B. Tatterson,et al.  Stereoscopic visualization of the flows for pitched blade turbines , 1980 .

[36]  S. Kresta,et al.  Impact of tank geometry on the maximum turbulence energy dissipation rate for impellers , 1996 .

[37]  H. Yamazaki,et al.  Concentration profiles of solids suspended in a stirred tank , 1986 .

[38]  Matthias Bohnet,et al.  Untersuchungen zur Verteilung der dispersen Phase in Fest/Flüssig-Rührreaktoren , 1995 .

[39]  Franco Magelli,et al.  Solids concentration profiles in a mechanically stirred and staged column slurry reactor , 1985 .