Staged Fluidized Leaching SFL

A method for designing SFL has been developed (Kwauk, 1979a), but it will not be discussed in this short presentation. 

The phenomenon of bubbling has attracted much attention from fluidization technologists to theorize on the origin and mechanics of bubbles and to elaborate on their mathematical modeling, but it has not been sufficiently recognized as indicative of the need for devising better modes of G/S contacting in which bubbles are suppressed or even totally eliminated. 

For G/S particle systems, enhancement in convective heat transfer is achieved at the expense of increased pressure drop in moving the gas at higher velocities. A measure of the relative benefit of enhanced heat transfer to added expenditure for fluid movement can be approximated by an effectiveness factor, E, defined as the ratio of the heat transfer coefficient to some kind of a pressure drop factor. For G/S systems in which particles are buoyed by the flowing gas stream, this pressure drop factor is expressed by the Archimedes number Ar, and E can be written 

These considerations of contact efficiency and pressure drop in relation to bubbles in fluidization points to an area of endeavor where bubbles are absent. 

The following four species of bubbleless G/S contacting will be dealt with in this chapter  

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