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AN INVESTIGATION OF THE EFFECT OF BUBBLE DIAMETER ON THE PERFORMANCE OF GAS-SOLID FLUIDIZED BED REACTOR AND TWO-PHASE MODELING OF BUBBLING FLUIDIZED BED REACTOR IN MELAMINE PRODUCTION

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Author(s): Amir Farshi | Houman Javaherizadeh | M.A. Hamzavi –Abedi

Journal: Petroleum and Coal
ISSN 1337-7027

Volume: 50;
Issue: 1;
Start page: 11;
Date: 2008;
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Keywords: Bubble diameter | Fluidized bed | Modeling | Two-phase | Bubble coalescence | Bubble splitting

ABSTRACT
Bubble diameter is an important parameter in the modeling of gas-solid fluidized bed reactor and plays an importantrole in the performance of the fluidized bed reactor. Determination of the actual bubble diameter in the fluidizedbed is very important. Bubble diameter starts at the initial bubble diameter er ( b0 D ) and grows by coalescence andsplitting phenomena, until it reaches the stable bubble diameter at the bed.Variation of bubble diameter with bed height has been expressed as linear, exponential, and fractionalrelationships. The linear relationship of Yasui et al. [34] predicts the highest value, while the relationship of Park et al. [21]predicts the lowest value and the relationship of Mori and Wen [19] yields an intermediate value. Computation of meanvalue of bubble diameter is especially important, because it is usually necessary in relationships for determinationof bubble velocity. For investigation of the performance of fluidized bed reactor, the two-phase model of Werther [31,32] wasused. The results of modeling, including variations of raw material conversion fraction with gas velocity weredrawn for various equations of bubble diameter and were compared to experimental conversion fractions.The results show that the diameter relationships of Mori and Wen [19] and Rowe [23] provide a better fit of data thanother equations. For this reason, the equations of Mori and Wen [19] and Rowe [23] are the best relationships forestimation of bubble diameter.Other relationships, like Darton et al. [5] provide a suitable estimation of bubble diameter in some situations. On the otherhand, some equations, like Geldart [8] and Werther [14] do not yield appropriate predictions for bubble diameter.
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