Authors: S. Moffatt a, S. Ramchandran a, P. Zhao b, and K . Williams b
a Ascend Performance Materials, LLC
b CPFD Software, LLC
Source: This paper was first presented at the 10th International Conference on Circulating Fluidized Beds and Fluidization Technology in 2011.
Abstract: Accurate entrainment rates are important in fluidized bed reactors for several reasons, including determination of cyclone loadings and efficiencies, sizing of diplegs, and inputs to population balance models. Entrainment correlations exist in the literature and from other sources to predict entrainment rates from fluidized beds, but they can vary by orders of magnitude. In addition, many correlations do not take into account effects of internals which are present in many types of industrial reactors. A study was undertaken to better understand entrainment rates from Sohio- type acrylonitrile fluidized bed reactors containing catalyst classified as a Geldart type A powder. As part of this study, full scale CFD models were developed using the Barracuda® computational particle fluid dynamics (CPFD®) software and validated with the help of data collected from multiple plant reactors. These models compared two different sizes of industrial-scale reactors and included all major internals including cooling coils, cyclones, cyclone diplegs and gas spargers.
Data on the pressure profile and actual entrainment rate to the cyclones generated by the Barracuda models were compared to the measured pressure data and derived entrainment rate in the plant reactors. The results showed good agreement. Additionally, evaluation of using the slip factor in the model to compare the particle volume fraction in the freeboard to the actual entrainment rate was done to determine if this technique could be used in the plant setting. The slip factor as calculated by Barracuda was between 1.55-1.95 which is similar to other values in the literature.