Barium sulfate precipitation in jet reactors: Large eddy simulations, kinetics study and design considerations

Abstract

The paper presents an application of large eddy simulations (LES) to predict the course of barium sulfate precipitation carried out in jet reactors and basic guidelines for a reactor design. The reactors in question were of different geometries and made in different sizes in order to achieve high mixing intensities and low residence times in a mixing chamber, thus enabling to reflect and understand the effects of process conditions and influence of mixing on the course of precipitation better. The system’s behavior is explained using experimental and simulation results. Simulations were validated by comparing LES model predictions with experimental data, as well as the k-ε model supplemented with the multiple-time-scale mixing model. The BaSO4 precipitation results obtained with a CFD based precipitation model are in a very good agreement with experiments and are used to distinguish the jet reactors that allow obtaining a product with favorable characteristics, i.e., the smallest mean particle size. In general, the smallest studied reactors are found to best meet this criterion. A special attention is given to precipitation kinetics models, the choice of which can significantly affect predictions’ accuracy. Several literature precipitation kinetics models were tested and the ones working best in jet reactors were identified. Finally, a time-scale analysis of process controlling mechanisms is highlighted and the assumption of negligibility of the subgrid closure for precipitation in LES is validated.