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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.

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Dryspec2 (DRYer System for Property and Energy Control) is an interactive computer program for use in making calculations relative to a two‐stage dryer for dairy products. The program indicates the relationship between the energy consumed by the drying process, the process parameters and the properties of the raw material and of the powder produced. To develop Dryspec2, simple model representations of both drying stages were made. Moreover, known physical relations were used to the maximum possible extent. Sorption isotherms form an essential part of the total drying model. The model can be attuned to the situation prevailing in actual practice by taking two model parameters of the first drying stage and one parameter of the second drying stage from data associated with the drying installation concerned. This gives the model a high degree of flexibility. Dryspec2 can be applied for such purposes as finding the optimum process conditions needed to produce a powder that must satisfy specific quality requirements at the lowest possible energy consumption. Dryspec2 is also suitable for use in designing or modifying a spray drying plant. Incorporation of the drying model underlying Dry spec2 into on‐line process control is currently under development.