Parameters Influencing Agglomeration

The kinetics of agglomeration can be understood as a quasi-bimolecular reaction. If only particles of one size are concerned, the kinetics can be described by Equation 4.1, with N as density of these particles. Here, a denotes the efficiency of the bimolecular collisions  

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Constant product quality requires an even feed rate, homogeneous bulk density of the material to be treated, uniform densification, and reproducible maximum pressure. This statement is true for all pressure agglomeration methods. However, while these conditions can be met relatively easily in die and roller presses with proper feed preparation and specific equipment parameters, it is rather difficult to achieve in extrusion. The reason for this is that densification and maximum pressure depend on the resistance to flow in the die channel or holes. Small variations in feed homogeneity or frictional properties can yield major differences in equipment performance and product quality. Wear or buildup in the extrusion die are among the most important parameters influencing the back-pressure which, in turn, is responsible for the amount of densification prior to extrusion. 

Parameters Related to Particles Building an Agglomerate. The most important particle related parameters that influence agglomerate structure are ... 

Kinetic studies deal with theoretical and experimental investigations of the motion in agglomeration equipment, the growth mechanisms caused by these movements, and the operating and equipment parameters influencing the process. To be able... 

Among all parameters influencing RS content, crystal texture is of utmost importance. It is evident that a crystal exhibiting a porous texture will enable the easy escape of a solvent while a compact and dense crystal will retain the solvent inside its structure whatever the type of particles monocrystalline (i.e., monoparticular) or polycrystalline . The term polycrystalline particles will be employed to designate elementary particles that can be composed of agglomerates, spherolites or spherical crystals according to Kawashima. ... 

The model is able to predict the influence of mixing on particle properties and kinetic rates on different scales for a continuously operated reactor and a semibatch reactor with different types of impellers and under a wide range of operational conditions. From laboratory-scale experiments, the precipitation kinetics for nucleation, growth, agglomeration and disruption have to be determined (Zauner and Jones, 2000a). The fluid dynamic parameters, i.e. the local specific energy dissipation around the feed point, can be obtained either from CFD or from FDA measurements. In the compartmental SFM, the population balance is solved and the particle properties of the final product are predicted. As the model contains only physical and no phenomenological parameters, it can be used for scale-up. 

Figure 4.12 Influence of kinematic parameter of flow A and viscosity on the dispersion degree of Ti02 agglomerates in silicone oil (trials with a single screw extruder) [151...

Equation (1) indicates the influence of the major parameters which determine the tensile strength of an agglomerate with bonding localized at the points of contact. It requires knowledge of the tensile strength of a single... 

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