Scale-up technology in low-velocity slug-flow pneumatic conveying

To design a low-velocity slug-flow pneumatic conveying system, not only should we predict total pipeline pressure drop, but also locate upper and lower dense-phase boundaries [R. Pan, P.W. Wypych, and J. Yi, Design of Low Velocity Slug-Flow Pneumatic Conveying Systems, 6th International Conference on Bulk Materials Storage, Handling and Transportation, Wollongong, NSW, Australia, 28-30 September, 1998, pp. 211-217]. The pressure drop is used to carry the slugs. and the boundaries are to control tire air velocity for achieving a slug-flow along the pipeline. Based on powder mechanics and packed bed model, an accurate procedure that predicts the total pipeline pressure drop has been developed and verified [Powder Technol. 94 (1997) 123]. However, the method to locate the boundaries has not yet been developed properly. In this paper, the mechanisms involved at the boundaries were investigated. Based on the understood mechanisms. a small and specific test rig was designed and built. As long as a sample of the conveyed product is tested in such test rig, the boundaries for tire product can be determined directly and accurately. Hence, by combining the procedure for predicting the total pipeline pressure drop and the method for locating the boundaries, a simple and reliable scale-up technology is presented for the design of low-velocity slug-flow pneumatic conveying systems. A relationship between the material properties and the locations of boundaries was also examined. Although such a relationship will need to be verified by more actual test data, it is certain that this relationship is very useful for understanding and design purpose, (C) 2002 Elsevier Science B.V. All rights reserved.