Agglomeration in Spray Drying Installations (The EDECAD Project): Stickiness Measurements and Simulation Results

Abstract

Spray drying is used for the manufacture of many consumer and industrial products such as instant dairy and food products, laundry detergents, pharmaceuticals, ceramics, and agrochemicals. During spray drying, agglomerates of powder particles are formed that determine the instant properties of the powder. Agglomeration during spray drying is considered to be a difficult process to control. The main cause of this is the complex interaction of the process variables: the atomization process, the mixing of spray and hot air, the drying of suspension droplets, and the collision of particles, which might lead to coalescence or agglomeration. As a consequence, agglomeration during spray drying is operated by trial and error. In an EC-sponsored project, named the EDECAD project and coordinated by NIZO food research, an industrially validated computer model, using CFD technology, to predict agglomeration processes in spray drying machines is developed. A Euler-Lagrange approach with appropriate elementary models for drying, collision, coalescence, and agglomeration of the dispersed phase is used. The main result of the EDECAD project is a so-called design tool, which establishes relations between the configuration of the drying installation (geometry, nozzle selection), process conditions, product composition, and final powder properties. The design tool has been validated on pilot plant scale and industrial scale. This article presents the setup and results of dynamic stickiness tests and some CFD simulation and validation results.

Keywords:

• Agglomeration: Computational fluid dynamics
• Stickiness
• Modeling
• Spray drying

ACKNOWLEDGEMENTS

This work is sponsored by the European Commission in the frame of the EC Fifth Framework Programme within the research programme “Competitive and Sustainable Growth” (contract G1RD-CT-2000-00340, http://www.edecad.com). The authors thank the other project partners Armor Protéines, Royal Numico, Anhydro A/S, University of Manchester, Bremen University, TU Darmstadt, and Martin-Luther-Universität Halle-Wittenberg for their participation and for supplying the products studied.

Notes

Copyright from Verdurmen et al. ^[29] . Reproduced with permission from EDP Sciences.

*Relative span is defined as [d (v, 0.9) − fd (v, 0.1)]/d (v, 0.5).