MICROMIXING OF SOLIDS AND FLUID IN AN AGGREGATING PRECIPITATOR

A lab-scale precipitator of alumina trihydroxide (gibbsite) is simulat ed for three extreme cases of micromixing, these being: the familiar c ases of Maximum Mixedness and Complete Segregation, and a third case i n which the fluid is mixed but the solids are segregated. Through this novel third case, the effect of segregated fluid on the particle size distribution is distinguished from the effect of segregated solids. I t is found that these two effects are sometimes in opposition to each other, and the latter is dominant in a system undergoing aggregation b ut not nucleation. Few other simulations have considered this. Conclus ions are drawn on the relevance of micromixing to simulating crystalli sation, especially when aggregation is significant. (C) 1998 Elsevier Science Ltd. All rights reserved.