Scaling Rules for Tumbling Blenders

The ensuing discussion will revolve around experiments run in 14, 56, and 300 L tote blenders using two mixtures a free-flowing binary 50 50 w/w% mixture of 400 ttm sand particles and a cohesive mixtme of 3% micronized acetaminophen ( 30 ttm) in a 50 50 w/w% matrix of PH102 Avicel and Fast-Flo lactose. All experiments were run at 60% of blender capacity at a rotation rate of 10 rpm. In raw form the acetaminophen was extremely cohesive and agglomerates (up to 0(1 cm) in diameter) formed in the bulk mixtme. The effect of blender scale on the breakup of these agglomerates is an important consideration for scale-up of tumbling blenders. 

Probably the most important rule governing the basic dynamics of mixing in tumbling blenders is that the loading protocol has the most direct impact on the mixing rate. When the blender is symmetrically loaded in a top/bottom fashion. 

All experiments were run at the same rotation rate, making it appear that shear energy scales with vessel size at constant rotation rate. Particle velocities in the flowing layer have been shown to scale with the radial length of the blender 

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