Dynamic simulation of technical precipitation processes

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Precipitation is an important operation of interconnected solid processes. Precipitation dynamics originate from the complex coupling of fast primary processes (mixing, nucleation, growth...) with secondary processes (agglomeration, ripening, ...) and instationary operating conditions on a wide-stretched timescale. The stirred-tank reactor, which is often used in industrial processes, exhibits inhomogeneity in turbulence, flow field and in the composition. For this reason, numerical description is difficult and depicting relevant process times (minutes or hours) for technical precipitation processes in closed simulations is not possible. Hybrid methods are required. Therefore, the aim of this project is the development of a new methodology for the simulation of complex technical precipitation processes.In the current second funding period a hybrid module for the flow sheet simulation of precipitation in stirred-tank reactors was developed. This model is based on a compartment method. The described complex system is depicted by interconnected compartments (mixing- and residence-time-compartment) integrated in the framework program (Dyssol), which is developed by the central project in SPP 1679. This method allows the decoupling of the primary processes in the area of feed inlet from the complex flow field- or mixing conditions and secondary processes in the reactor. Experiments in the second funding period for one operating point prove impressively the validity of the compartment method.In the third funding period the research is now focused on the extension of the compartment model over the whole width of technical relevant process operating points. The mixing compartment is therefore approximated as a 'Jet in Cross Flow' arrangement with variable parameters. Besides own methods from the first funding period, methods from the group Segets/Peukert are considered for this model. For a separate validation of the numerical model for the 'Jet in Cross Flow' arrangement precipitation experiments, PIV and LIF measurements shall be done for this arrangement. The predictive abilities of the whole hybrid model shall be investigated with experimental and literature data of the bulk-reactor. Transfer to different crystal substances is tested. The influence of the apparatus size (scale up) shall be investigated through the choice of different exchange streams between the compartments based on fluid dynamic considerations. By connecting with the resulting flow sheet module 'decanter centrifuge' (group Nirschl) dynamics and the performance of Dyssol for an interconnected, precipitation-exceeding, dynamic process with recirculation of particles shall be demonstrated.