β Scribed by H. F. Johnstone; J. D. Batchelor; C. Y. Shen
No coin nor oath required. For personal study only.
The oxidation of ammonia in the presence of manganous oxide-bismuth oxide catalyst supported on small alumina spheres was studied in both fixed and fluidized beds in the temperature range from 205" to 250Β°C. The column used was 4% in. in diameter and 43 in. high. The experiments were made so that the transport effects in the fluidized bed might be separated from the chemical kinetic effects.
In accordance with the theory of two-phase fluidization proposed in a previous paper, comparison is made between the reaction rate associated with the discontinuous phase and that associated with the continuous phase as estimated from the results in the fixed bed. The over-all reaction-rate constants in the fluidized bed can be related to those in the fixed bed by an exponential term in the superficial gas velocity, Vn; n is a constant which depends on the reaction system and the size and type of the reactor.
Little information has been published on reaction kinetics in fluidized beds. Gilliland, Mason, and Oliver i-eported that a t the same space velocity a fluidized bed gives a lower conversion for a homogeneous gas reaction than does a fixed bed ( 4 ) . This was attributed to mixing and by-passing in the bed. On the basis of pressure drop studies, Toomey and Johnstone ( 1 0 ) suggested that a fluidized bed may be considered to be composed of two phases: a continuous phase consisting of uniformly dispersed particles in a supporting gas stream and a discontinuous phase consisting of pure gas in the form of bubbles, channels, or slugs. On this basis an equation was developed for the variation of pressure drop with gas velocity.
I n a fluidized catalytic reactor the two-phase concept implies that J. D. Batchelor's present address is Pittsburgh Consolidation Coal Company, Library Pennsylvania; C . Y. Shen is with Monsanto) Chemical Company, Dayton, Ohio.
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