Blending techniques tumbling

There are currently no mathematical techniques to predict blending behavior of granular components without prior experimental work. Therefore, blending studies start with a small scale, try-it-and-see approach. The first portion of this chapter is concerned with the following typical problem a 5-ft - capacity tumble blender filled to 50% of capacity and run at 15 rpm for 15 minutes produces the desired mixture homogeneity. What conditions... 

To ensure that specifications established for critical product quality attributes are met in a large-scale operation, the formulation and manufacturing process developed in the laboratory must be transferred to production and validated. It is necessary to start with a small scale in pharmaceutical research and development. Unfortunately, small-scale mixers necessary during the early development phase will not necessarily have the same characteristics as a commercial-scale mixer. Currently no mathematical techniques exist to predict the blending behavior of multicomponent solid mixtures therefore, experimental work to ensure the proper scale-up and transfer to the production facility is required. Consider the following process parameters for a tumbling blender during scale-up trials ... 

There are three parameters that should be kept similar in scaling tumble blenders. These include geometric, kinematic, and dynamic similarity. This approach is valid for tumble blending without the use of shear (such as an intensifier bar), for low-cohesion materials. Cohesive materials have poor flow and hence blend less efficiently at smaller scales therefore, this technique may overestimate the blending time for scaling up, and underestimate the time when scaling down. 

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