With the advent of readily-available high-performance computing hardware, the use of computational fluid dynamics (CFD) in the design and scale-up of gas-solid flow reactors and process equipment has become commonplace. In research-oriented studies, reactors are generally smaller-scale facilitating comparison with experimental data and computational tractability owing to smaller mesh sizes. In contrast, the industrial practitioner is most interested in simulating industrial-scale equipment either to understand full-scale performance in the context of new development or to troubleshoot and remediate under-performing production assets. Literature suggests that the mesh resolution used in simulating rapid gas-solid flows should not exceed ten particle diameters if standard interphase drag models are used and solution accuracy is to be preserved. For the industrial practitioner seeking to simulate full-scale process equipment, the recommended mesh size poses a formidable simulation challenge.
Filtered gas-solid flow models offer relief from the large computational loads required for accurate simulation of commercial-scale equipment. The filtered model seeks to replace the traditional micro-scale drag laws with drag laws better suited for the larger cell sizes required for timely commercial-scale simulations. The development of such meso-scale drag laws is done by performing simulations in a periodic domain and filtering the results using filters of various sizes. These filtered results are consolidated into a composite drag relation that can be used across various cell sizes without compromising accuracy.
In this presentation, industrial experience involving the use of a filtered two-fluid model for simulating reacting gas-solid flows in chemical processes will be discussed. The discussion will emphasize hardware modifications conceived with the aid of CFD analysis and before-and-after comparisons of performance.
