Investigations about the effect of fractal distributors on the hydrodynamics of fractal packs of novel plate and frame designs

Flow distributors are extensively adopted by chemical industry to distribute process fluid for the downstream equipment. Conventional flow distributors in general have limited number of outlets. Their low outlet densities cannot distribute the incoming process stream uniformly and efficiently, which consequently undermine the overall equipment performance. In contrast, fractal distributors can achieve high outlet densities because of their inherent self-similarity feature. In this study, we fabricated two fractal packs of novel plate and frame designs. Each fractal pack was comprised of a fractal distributor, a resin bed and a fractal collector. The fractal distributors/collectors in these two fractal packs have 256 and 16 outlets/inlets, respectively. In this study, we carried out both CFD modeling and experiments to understand the effect of outlet density on the hydrodynamics of the downstream resin bed. By comparing the predicted velocity fields and the measured residence time distribution (RTD) curves, we noticed that a fractal distributor of high outlet density can distribute the process stream uniformly at a low pressure drop to the resin bed. The process streams entering the resin bed reach plug flow profile within a short bed depth. As a result of the uniform flow distribution, mal-distribution such as channeling and dead space are minimized, and the process streams have a uniform RTD in the fractal pack. In comparison, the fractal distributor of low outlet density, which mimics some aspects of a conventional distributor, is found to have severe mal-distribution in the resin bed and consequently poor RTD inside the fractal packs. In addition, the RTD analysis confirms that the fractal distributor of high outlet density shows consistently good distributing performance for a wide range of operating flow rates. This study confirms the advantages of fractal distributors over conventional ones and demonstrates the benefit of fractal distributors in improving the overall performance of chemical equipment, indicating that fractal distributors are promising to enable process intensification for the chemical industry.