Application Note

Recommended Blending Equipment For Powdered Detergents

Source: Charles Ross and Son Company

Ross Ribbon Blenders are well proven in the manufacture of detergents and intermediate compositions. Granular and powdered raw materials are loaded into the U-shaped trough and mixed by a horizontal solid-shaft agitator consisting of inner and outer helical ribbons. A full load usually corresponds to a product level around the outer ribbon’s tip, allowing enough headroom for the materials to be vigorously blended. Minor liquid ingredients, if any, are gradually added to the blend through atomizing nozzles installed in a spray bar. This step is normally performed while the dry components are being agitated to ensure uniform coating and prevent the formation of undesired lumps.

The position and precise pitch of each ribbon in a Ross Blender are designed to produce a well-balanced axial and radial flow pattern: the outer ribbon moves material in toward the center, and the inner ribbon moves them out toward the walls. At the same time, the difference in the ribbons’ speeds causes product to move along the blender’s horizontal axis in two opposite directions. Fast and thorough mixing is achieved despite differences in particle shape, size and density among the batch ingredients. Maximum tip speeds in the neighborhood of 300 ft/min are typical but with variable speed control, the blending action can be fine-tuned to match the characteristics of a particular recipe.

Ross Ribbon Blenders are fabricated to close tolerances for accurate mixing. Clearances between the agitator and the trough surfaces typically fall within the 1/8” to 3/16” range. This enhances mixing performance by preventing materials from stagnating in any part of the blender during the mix cycle. Installing scrapers in strategic parts of the agitator is an option worth considering for formulations that tend to pack in corners.