DILUTE RAINING FLUIDIZATION

One method of improving G/S contacting consists of showering solids in dilute suspension from the top into an upflowing gas stream. Experiments verified that gas/solid heat transfer coefficient for such a system is essentially the same as for the discrete particles, and that pressure drop for gas flow is extremely low. 

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The mechanism of interaction between catalyst and gas in a large fluidized bed is complex and is not well correlated with design factors. In the bed itself, large bubbles of a foot or more in diameter form and are irrigated with a rain of catalyst particles. This process occurs in parallel with a well-mixed fluidized bed. Above the bed level and before the entrained catalyst is recovered in cyclones, the reaction continues in dilute phase plug flow. Since even the physical behavior of fluidized beds is not well understood, the design of such... 

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