Tortuosity variation in a low density binary particulate bed

The importance of particle size ratio and particle composition in the properties of a mixed bed is well known. Nevertheless, the dependence of the bedchanneltortuosity Tontheporosity eintheform T=1/e n ,where nisassumedtobeaconstant,showsthatthevalueof ndependsontheproperties of the packed bed. For loose packing, experimental data for binary mixtures of glass beads of a size ratio from 1 up to 53.8 was analysed in terms of porosity, tortuosity and permeability. The packing procedure was performed without intensive compacting methods e.g. vibration, etc. Obtained results show that the parameter n is a function of the volume fraction of large particles xD and, for spherical particles, lies in the range 0.4‐0.5. The explanation for this variation is (1) a distortion effect on the small particles arrangement occurring near the large particle surface; (2) in the region of minimum porosity, near contact points of large particles, the occurrence of dead zones that are free of small particles. A relationship accounting for this effect is proposed that may be useful for the analysis of transport phenomena in granular bed filters, chromatographic columns, etc.

[1]  Bouvard,et al.  Correlation between random dense parking and random dense packing for determining particle coordination number in binary systems. , 1992, Physical review. A, Atomic, molecular, and optical physics.

[2]  N. Standish,et al.  Estimation of the Porosity of Particle Mixtures by a Linear-Mixture Packing Model , 1991 .

[3]  Jacob Bear,et al.  Fundamentals of transport phenomena in porous media , 1984 .

[4]  Douglas M. Smith,et al.  Knudsen diffusion in bidisperse mixtures of uniform spheres , 1987 .

[5]  Tatsuo Tanaka,et al.  Porosity of a mass of solid particles having a range of sizes , 1981 .

[6]  Ka Ming Ng,et al.  A generalized Blake‐Kozeny equation for multisized spherical particles , 1991 .

[7]  E. C. Childs.  Dynamics of fluids in Porous Media , 1973 .

[8]  Charles N. Satterfield,et al.  Mass transfer in heterogeneous catalysis , 1969 .

[9]  F. Ho,et al.  A variational calculation of the effective surface diffusion coefficient and tortuosity , 1981 .

[10]  M. Renaud,et al.  Transport phenomena in multi-particle systems—I. Limits of applicability of capillary model in high voidage beds-application to fixed beds of fibers and fluidized beds of spheres , 1997 .

[11]  Kroll,et al.  Simulation of Flow in Bidisperse Sphere Packings. , 1999, Journal of colloid and interface science.

[12]  Ricardo P. Dias,et al.  Particulate binary mixtures : dependence of packing porosity on particle size ratio , 2004 .

[13]  Dongfang Wu,et al.  Effect of the mechanical failure of catalyst pellets on the pressure drop of a reactor , 2003 .

[14]  Aibing Yu,et al.  Modifying the linear packing model for predicting the porosity of nonspherical particle mixtures , 1996 .

[15]  Don W. Green,et al.  Perry's Chemical Engineers' Handbook , 2007 .

[16]  J. Teixeira,et al.  Preparation of controlled particulate mixtures with glass beads of different sizes , 2004 .

[17]  F. Muzzio,et al.  A simple correlation for predicting effective diffusivities in immobilized cell systems. , 2010, Biotechnology and bioengineering.

[18]  Lutz Riepe,et al.  Interlayer conductivity of rocks — a fractal model of interface irregularities for calculating interlayer conductivity of natural porous mineral systems , 1987 .

[19]  J. Quirk,et al.  Permeability of porous solids , 1961 .

[20]  A. Revil,et al.  Ionic Diffusivity, Electrical Conductivity, Membrane and Thermoelectric Potentials in Colloids and Granular Porous Media: A Unified Model. , 1999, Journal of colloid and interface science.

[21]  J. Currie,et al.  Gaseous diffusion in porous media. Part 2. - Dry granular materials , 1960 .

[22]  P. Schneider,et al.  Effect of size and shape of catalyst microparticles on pellet pore structure and effectiveness , 1981 .

[23]  Tian C. Zhang,et al.  Evaluation of tortuosity factors and effective diffusivities in biofilms , 1994 .