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in Wiley InterScience (www.interscience.wiley.com).The results of a combined experimental and simulation study on the flow regimes that can be encountered during spout-fluid bed operation are reported. A regime map for a three-dimensional (3D) spout-fluid bed was composed, employing spectral analysis of pressure drop fluctuations and fast video recordings. In addition, 3D Euler-Lagrangian computations were performed to assess the capability of the model to reproduce the experimentally observed flow regimes. Spectral analysis of pressure drop fluctuations revealed that for most investigated regimes the model is able to predict the appropriate regime. The frequency at which the largest power is found is overpredicted by the model in most cases. The remaining differences between the simulated and the experimentally observed bed behavior are most probably related to the representation of the effective fluid-particle interaction in the model, which relies on local spatial homogeneity. The simulation results were compared with velocity maps determined from particle trajectories acquired using positron emission particle tracking. The model accurately reproduces measured particle velocities, including their root mean square, for all investigated conditions and is therefore able to capture the details of the particle flow in various flow regimes.

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Spout fluidized beds are frequently used for the production of granules or particles through granulation. The products find application in a large variety of applications, for example detergents, fertilizers, pharmaceuticals and food. Spout fluidized beds have a number of advantageous properties, such as a high mobility of the particles, which prevents undesired agglomeration and yields excellent heat transfer properties. The particle growth mechanism in a spout fluidized bed as function of particle-droplet interaction has a profound influence on the particle morphology and thus on the product quality. Nevertheless, little is known about the details of the granulation process. This is mainly due to the fact that the granulation process is not visually accessible. In this work we use fundamental, deterministic models to enable the detailed investigation of granulation behaviour in a spout fluidized bed. A discrete element model is used describing the dynamics of the continuous gas-phase and the discrete droplets and particles. For each element momentum balances are solved. The momentum transfer among each of the three phases is described in detail at the level of individual elements. The results from the discrete element model simulations are compared with local measurements of particle volume fractions as well as particle velocities by using a novel fibre optical probe in a fluidized bed of 400 mm I.D. Simulations and experiments were carried out for two different cases using Geldart B type aluminium oxide particles: a freely bubbling fluidized bed and a spout fluidized bed with the presence of droplets. It is demonstrated how the discrete element model can be used to obtain information about the interaction of the discrete phases, i.e. the growth zone in a spout fluidized bed. Eventually this kind of information can be used to obtain closure information required in more coarse grained models.