Scale-up and control of binder agglomeration processes — Flow and stress fields

This paper describes scale-up of granulation processes where a liquid binder is added to fine powder in order to form a granular product, with emphasis on the use of specific energy (energy per unit mass) as a controlling process group. The energy input is the result of applied shear in the flow field of the process, where both stress and flow fields may be coupled with the instantaneous material properties. This analysis can be relevant to both batch and continuous processes; indeed, the use of small batch experiments can be a means to derive empirical control functions and scale-up relations for larger batch and continuous processes.The technical goal of scale-up is to maintain similarity of critical product attributes as the production scale and/or throughput of a manufacturing process is increased. In this paper, a scaling framework is developed to consider critical process transformations in relation to the desired product attributes. A similar approach can be taken in developing process control strategies.In any agglomeration process, transformations can be used to describe how raw materials (typically fine powders and liquid binders) are converted into a granular product. While critical product attributes may be characterized on the scale of individual granules (e.g., size, shape, porosity, mechanical strength, etc.), industrial scale-up requires predictive relations for the sizing, design and operation of larger-scale process equipment. Considering scale-up on the basis of transformations is one way to link the macro-scale equipment decisions with micro-scale product attributes. This approach can be applied to the scale-up of batch and/or continuous granulation processes as well as transitioning from small batch prototypes to continuous production circuits. Additionally, a framework for the description and analysis of continuum flow and stress fields in mixer-granulators and the implications for scale-up of granulation processes are discussed.

Graphical abstractThis paper describes scale-up of granulation processes where a liquid binder is added to fine powder in order to form a granular product, with emphasis on the use of flow fields, stress fields and specific energy (energy per unit mass) as controlling process groups. This analysis can be relevant to both batch and continuous processes.Figure optionsDownload full-size imageDownload as PowerPoint slide