Binary fluidization

Voidage Distribution Ahead of a Bubble in a Fluidized Bed, 154 Binary Fluidization, 155... 

An alternative approach makes use of two-phase flow momentum conservation equations. Doubtless, such an approach forms a more sound foundation for the theoretical study of polydisperse and, in particular, binary fluidization. In principle, this approach may be based on the same notions and concepts as the fluid dynamic theory of monodisperse coarse suspensions developed in the present article. However, a number of new problems arise which are specific for polydisperse particulate mixtures. Among these new problems are ... 

After that, the Langevin equation for a single particle can be averaged over all the particles to yield an equation for W . This equation resembles the last Equation 7.1. It supplements the fluctuation equations resulting from the mass and momentum conservation laws for the ambient fluid. These equations have to be treated exactly in the same way as in Sections 7 and 8. As a result, we arrive at a representation for fluctuation temperature in a binary fluidized bed and to expressions for the pressures and stresses associated with particles of both species [76]. 

Ci j and V j respectively. In accordance with the theoretical basis of the kinetic theory of dilute gases, these properties are transported by short-term collisional contacts. For this reason, the KTGF models including the total particle-particle drag model, Fij = Ffj + f(J represent the solid flow dynamics for dilute binary fluidized beds. However, for dense beds, additional frictional effects need to be considered. An extra frictional particle-particle drag term, f(P must be taken into account. The... 

Chao Z, Wang Y, Jakobsen JP, Femandino M, Jakobsen HA (2012) Investigation of particle-particle drag in a dense binary fluidized bed. Powder Technol 224 311-322 Chao Z, Wang Y, Jakobsen JP, Femandino M, Jakobsen HA (2012) Multifluid modeling of density segregation in a dense binary fluidized bed. Particuology 10 62-71... 

Lu H, Gidaspow D (2003) Hydrodynamics of binary fluidization in a riser CED simulation using two granular temperatures. Chem Eng Sci 58 3777-3792... 

A schematic diagram of the experimental apparatus is shown in Fig. 1. A rotating fluidized bed composes of a plenum chamber and a porous cylindrical air distributor (ID400xD100mm) made of stainless sintered mesh with 20(xm openings [2-3]. The horizontal cylinder (air distributor) rotates around its axis of symmetry inside the plenum chamber. There is a stationary cylindrical filter (ID140xD100mm, 20(o.m openings) inside the air distributor to retain elutriated fine particle. A binary spray nozzle moimted on the metal filter sprays binder mist into the particle bed. A pulse air-jet nozzle is also placed inside the filter, which cleans up the filter surface in order to prevent clogging. 

In order to tailor the physical properties of nano-particles, wet granulation was conducted. Hydroxypropylecellulose (HPC-L) 5% aqueous solution was sprayed onto nano-sized Ti02 particles through a binary nozzle. Fluidization air velocity was set at approximately 1.5 times as large as the minimum fluidization air velocity. 

Catalyst powders with carefully specified particle size distribution have been known to possess good fluidization characteristics. Generally, addition of fine particles to coarse particles tends to improve the latter s fluidization characteristics. Experiments were thus conducted on binary particle mixtures, each consisting of a fairly close particle size distribution. 

Figure 52 plots the dimensionless subsidence time for the six sets of Group A-A and Group B-A binary mixtures for different fractions of fines, Xp showing that the improvement of fluidizing characteristics by addition of fine particles increases monotonically with increasing percentage of the fines. 

Guardiola, J., Ramos, G., and Romero, A., Electrostatic behaviour in binary dielectric/conductor fluidized beds, Powder Technol., 73 11-19 (1992)... 

Moritomi, H., Yamagishi, T. and Chiba, T. Chem. Eng. Sci. 41 (1986) 297. Prediction of complete mixing of liquid-fluidized binary solid particles. 

The simplest case for polydisperse systems is a binary mixture of a coarse and a fine size fraction of the same material, each considered to be uniform in size. The generalized fluidization equation for the coarse particles, with subscript 1, is (Kwauk, 1975 Huang et at., 1982)... 

The nonideal nature of G/S fluidization, shown as the bulging curve for zero solids flow in the voidage-velocity plot of Fig. 60, is considered to be caused by gas aggregation at low velocities and solids aggregation at high velocities. Alternately, the G/S system may be visualized to be equivalent to a binary mixture of the aggregated gas bubbles with a volume fraction of (e — 0) on the one hand, and of the aggregated solid particles in the form of clusters with a volume fraction of (1 — e) on the other. At low gas velocities,... 

Idealization of particulate fluidization provides the essential concept towards a basic understanding of fluid-particle systems in terms of the most significant factors, L/S in particular and G/S after appropriate corrections. The nature of fluid-particle motion cannot be properly understood, e.g., the preferential arrays of particles, L/S versus G/S, without supplementary studies of the basic mechanisms. Of immediate interest from a practical point of view is how to adapt the relatively simple relations derived for ideal fluidization to G/S systems, as already exemplified for fast fluidization. For polydisperse systems, the problem was oversimplified to the binary case, and... 

Cheung, L., Nienow, A. W., and Rowe, P. N., Minimum Fluidization Velocity of a Binary Mixture of Different Sized Particles, (Shorter Commun.) Chem. Eng. Sci. 29, 1301-1303 (1974). 

Moritomi, H Yamagishi, T., and Chiba, T., Prediction of Solid Mixing in Liquid Fluidized Beds of Binary Solid Particles, Proc. Second China-Japan Symp. Fluidization, April, 1985, pp. 238 - 249 (1985). 

Xia, Y., and Kwauk, M., Micro-Visualization of Fluidizing Behavior of Binary Particle Mixtures," Intern. Symp. Heat Transfer, Beijing, 1985, Hemisphere (1985). 

Asif, M. and Ibrahim, A. A, Minimum fluidization velocity and defluidization behavior of binary-solid liquid-fluidized beds. Powder Techno 2002, 126 (3), 241-254. 

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