| The behavior of particles in suspension is of great importance in many industries such as mineral processing, paints and water and wastewater treatment. Flocculation is an essential stage in water and wastewater treatment processes where particle growth is required. To better understand and properly model flocculation, it is necessary to utilize concepts from both surface chemistry and fluid dynamics. An improved understanding of flow characteristics in stirred tanks has been achieved by utilizing laser-Doppler velocimetry. It was shown that the local dissipation rate per unit mass near the blade tips exceeds the mean tank value by an order of magnitude or more, which emphasizes the importance of breakage in modeling flocculation process.; Experimental and theoretical studies have been performed for both kaolin-Fe(3+) and kaolin-polymer floc systems. A stochastic model has been successfully applied to floc breakage phenomena by classifying particle sizes into eight classes. Separate simulation algorithms have been developed for aggregation and breakage and combined to model the dynamic behavior of particle size distribution in batch and continuous flocculation systems. The changes of macro-molecular conformation in polymer flocs and the effects of incorporation of interstitial water upon aggregation were reflected in this simulation procedure. The applicability of the simulation procedure was supported by good agreement between simulation results and experimental data. |
