Solid particles, Geldart classification

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... 

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...

Geldart (1973) was the first to classify the behavior of solids fluidized by gases into four clearly recognizable groups characterized by the density difference between the particles and the fluidizing medium, (pp — pf) and by the mean particle size, d. Geldart s classification has since become the standard to demarcate the types of gas fluidization. The most easily recognizable features are... 

Apart from density and particle size, several other solid properties, including angularity, surface roughness and composition may also significantly affect the quality of fluidization. However, in many cases Geldart s classification chart is still a useful starting point to examine, fluidization quality of a specific gas-solid system. 

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