A client came to us with a difficult blending problem. The firm needed to blend a highly segregating mixture, consisting of relatively large plastic pellets and small beads, to a high degree of uniformity. Before coming to us, they had gone to a supplier of commercial V-blender equipment.

After several weeks of testing equipment, they found that a V-blender could not provide the required close blending uniformity. Samples taken from the blender indicated that the mix was not adequately blended. Furthermore, samples taken from the blender outlet indicated that significant segregation [220K QuickTime video] occurred during discharge from the blender. The equipment supplier had no ideas on how to modify the blender to improve its performance.

We started by building a model of the commercial blender and confirmed that it indeed was not capable of producing the required blend uniformity. We then experimented with a series of inserts in this unit, which, while significantly improving its operation, still did not meet the client's requirements. We then optimized a BLENSERT® tumbler (a cone-in-cone design that has improved segregation control over a typical mass flow container), to produce a configuration which fully satisfied our client's requirements for the material discharged from the blender.

Following this model study, we were contracted to produce a detailed design of a full scale unit having a live capacity of 200 cu. ft. Since the project was fast-track and needed to be done right the first time, we were subsequently awarded a contract to fabricate and supply three of these units. This equipment has been operating for several years with excellent results. Blend uniformity is as designed, and the blend remains intact through downstream equipment.