The microscopic modelling of hydrodynamics in industrial crystallisers

In this contribution a method for the calculation of crystal-crystal collisions in the flow field of an industrial crystalliser is proposed. The method consists of two steps. The first step is to simulate the internal Row of the crystalliser as a whole. For this purpose, the simulation of the internal Row of an 1100 1 draft tube baffled crystalliser at a Reynolds number of 240,000 is presented. This simulation was done with a lattice-Boltzmann scheme with a Smagorinsky sub-grid-scale turbulence model (c(s) was 0.11) on approximately 35.5 x 10(6) grid nodes. The second step of the method consists of simulating individual crystals in a fully periodic box with turbulent conditions that represent the conditions in a point of the crystalliser. Thus collision frequencies and intensities of the crystals under the local hydrodynamic regime can be obtained. In this contribution a feasibility study of this second step is described. A theoretical framework is established to identify the key parameters that determine the relationship between the crystalliser flow and the box simulations. Based on this framework, conditions for box simulations representing three monitor points in the simulated crystalliser are calculated. Finally, to demonstrate the method of predicting the motion of individual particles, sedimentation and consecutive collision of a single sphere with a solid wall is simulated. (C) 2001 Elsevier Science Ltd. All rights reserved.