The hydrodynamics of low-density particles and optimization of the EMMS calculation process

Abstract

Different reaction technology determines different catalytic materials and solid density affects the hydrodynamics behavior in a fluidized bed. An efficient hydrodynamics study is, therefore, highly desirable, even for evaluating the assumptions through pilot-scale investigation. To develop new fluidized bed technology that requires low-density particles (e.g., the vapor-phase Beckman rearrangement to produce ε-caprolactam), the authors thoroughly studied the hydrodynamics of low-density particles (true density 750 kg/m3, packing density 450 kg/m3) in a turbulent fluidized bed. Pilot-scale cold experiments were conducted in an ∅800 mm column with optical fiber probes. The TFM was adopted, where the Wen&Yu model, EMMS model, and six filtered models were coupled, respectively. The solution of the EMMS model is often challenging because of the iterative solution of nonlinear equations. In this work, the calculation process of the EMMS model was optimized, saving one global search for every possible state solution, and a set of nonlinear equations can be linearized. Comparisons between experiment and simulation results revealed that the EMMS models gave the best prediction. This work can provide a research model and guidance for the design of industrial fluidized bed reactors using low-density particles.