Solid particles, Geldart

Although most of the experimental data reported here were obtained with large particles, Geldart Class B and D powders, it is believed that the concept can equally be applied for any fine aeratable and lfee-flowing solids, Geldart s Class A powders. 

Figure 49 shows a set of bed collapsing curves for a Geldart Group A-A (for Geldart s classification of solid particles, see Geldart, 1972, 1973) binary solids mixture, two closely sized alumina powders, of average particle diameter 104 and 66 microns, respectively. The curve on the extreme left with 0% fines represents the pure coarse component, which is... 

Based on extensive studies involving a variety of solid particles and fluids with a wide range of properties, Geldart (1973) classified the fluidization behavior of systems under four categories of particles A, B, C, and D (Figure 9.2). Class B particles conform strictly to the two-phase theory of fluidization described earlier the gas in excess of that needed... 

Fig. 10.2 Flow regime map of gas-soUd contacting, a Characteristics of turbulent flow regime, b Characteristics of spouted beds, bubbling fluidized beds, fast fluidized beds and pneumatic transport regimes. In the figure notation the ordinate u = U p / n(pp — pg)g) is a dimensionless gas velocity, the abscissa d = dp[pg pp — Pg)glp ] a dimensionless particle size, the terminal velocity of a particle falling through the gas (m/s), and Umf the gas velocity at minimum fluidization (m/s). Letters A, B, C and D refer to the Geldart classification of solid particles. Reprinted from [49] with permission from Elsevier...

Types of Solids Geldart [Fowder TechnoL, 7, 285-292 (1973)] has characterized four groups of solids that exhibit different properties when fluidized with a gas. Figure 17-j shows the division oi the classes as a function of mean particle size, d,, Im, and densitv difference, (p, — P/ ), g/cm, where p, = particle density and p = fluid density... 

The phenomenon is represented by Figs. 17-40 and 17-41 for Geldart-type A and B solids, respectively (see beginning of Sec. 17). The initial efficiency of a particle size cut is found on the chart, and the parametric hue is followed to the proper overall solids loading. The efficiency for that cut size is then read from the graph. 

The validity of extrapolating the data obtained in a semicircular model to a circular one is also of concern. Not much research was carried out in this area Preliminary research results by Whiting and Geldart (1980) indicated that, for coarse, spoutable solids similar to the particles... 

Geldart, D., Behavior of Fine Particles in a Fluidized Bed of Coarse Solids, EPRI Report CS-2094, Electric Power Research Institute, Palo Alto, CA. (1981)... 

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