Computational Fluid Dynamic Modeling of a 1 m~(3) Draft Tube Baffle Crystallizer with Fines Removal

摘要

The commercial software ANSYS CFX10.0 has been used to model fluid flow, heat transferand boiling in a 1m~(3) Draft Tube Baffle (DTB) crystallizer with fines removal, used for the crystallization of salt. The crystallizer contains several sections with very different flow and heat transfer conditions, including a draft tube, an annular space for down-flow of liquid outside the draft tube, and an annular settling zone separated from the main body by a baffle, which is used for fines removal. The feed, and the flow of the dissolved fines, are fed directly under an upflow impeller located at the base of the draft tube. A variety of parameters in the crystallization process were varied in the course of the study, including the power input to the impeller, the total rate of heat transfer in the crystallizer, and flow rates of the feed stream, and fines removal stream. The results demonstrate the relationship between the operating conditions and the flow regimes in different sections of the crystallizer, and also the boiling behavior, vapor flow, and phase separation at the free surface of the crystallizer. Of special importance to the operation of the crystallizer is the predicted effect of the fines removal rate on the fines cut-size, which could have a significant impact on the overall product particle size distribution.