Simulation of agglomeration in spray dryers: the EDECAD project

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 agrochemi- cals. During spray drying, agglomerates of powder particles are formed, which 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 par- ticles 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 pro- ject and co-ordinated by NIZO food research, an industrially validated computer model, using Com- putational Fluid Dynamics (CFD) technology, to predict agglomeration processes in spray drying machines is developed. An Euler-Lagrange approach with appropriate elementary models for dry- ing, collision, coalescence and agglomeration of the dispersed phase is used. The main result of the EDECAD project is a so-called Tool, which establishes relations between the configura- tion of the drying installation (geometry, nozzle selection), process conditions, product composition and final powder properties. The Design Tool is being validated on pilot-plant scale and industrial scale. It will provide a tool for improved design and optimisation of spray drying and agglomeration equipment, to improve the quality of products and to increase the productivity of such equipment. This paper introduces the approach of the project and some preliminary results. spray drying / agglomeration / computational fluid dynamics / modeling