A PDF modelling of precipitation reactors

Efforts to model precipitation processes in chemical reactors need to combi ne fluid mechanics with precipitation processes description. The main diffi culty is to consider together micromixing phenomena, which are known to pla y an important role, with complex reactions kinetics and particles size dis tribution in the Row. In the present study, a probability density function (PDF) method is presented to calculate the evolution of the particles size distribution. The main advantage of the method is to include a micromixing model based on a Lagrangian frame where chemical reactions are treated with out modelling and which requires minimal computational resources. The micro mixing model considered is the interaction and exchange with the mean (IDM) . Precipitation reactions are nucleation, growth and aggregation. Because o f the nature of the powerful numerical technique used. based on Monte-Carlo simulations, the method is able to produce, at any point in the Row, react ants concentration and supersaturation fields, and the particles size distr ibution field, by simple moments method. The main advantage of the method o ver traditional population balance solvers is its capability to treat multi -dimensional (e.g. size, crystal morphology, chemical properties, etc.) pop ulation balances just as efficiently as it treats high-dimensional PDF. The PDF code is coupled with the commercial CFD package FLUENT which is used f or the turbulent calculation of the Row (classical k-epsilon turbulence mod el), where the presence of the solid phase is assumed nut to affect the Row field. An example is presented in the case of silica particles aggregation . The influence of initial reactants concentration and hydrodynamics parame ter are investigated. (C) 2001 Elsevier Science Ltd. All rights reserved.