Modeling and Scale-Up of Tumble Blenders for Highly Segregating Materials

摘要

Tumble blenders are one of the simplest and most common types of blenders for mixing powdersand granular materials. Tumblers are commonly used for batch blending in a wide range ofindustries when low-shear, gentle mixing is sufficient to blend the formula components. Materialssuitable for tumble blending are generally easy flowing, non-cohesive materials that don't formagglomerates when tumbled. By their nature these types materials are generally easy to mix, but theyalso represent a class of materials that can have strong segregation tendencies. Tumble blendingbinary or multi-component mixtures of granular solids with a wide size distribution can presentunique challenges because the blending mechanisms at work in a tumbler (primarily shear anddiffusion) are the same mechanisms that cause segregation. Shear that occurs during discharge of atumble blender can cause demixing of materials that may be overlooked if samples are collectedfrom the blender only before discharge. Blending materials such as plastic pellets and granularpolymer materials for plastics compounding and solid surface manufacturing present some of themost extreme challenges for achieving blending and controlling segregation. Modeling the blendingprocess using actual materials and correct sampling methods is the best way to ensure successfulscale up to a production process. Two applications for blending coarse, free flowing plastic materialswere modeled in pilot scale to determine optimum blender configuration and process parameters forblending. Scale-up parameters were applied to determine the full scale operating parameters and, inone case, testing the full scale equipment was done to confirm performance. The process led tosuccessful scale-up and avoided the potential for significant problems that could have resulted fromsegregation.