Predicting agglomerate fragmentation and agglomerate material survival in fluidized beds

In fluid coking, agglomeration is undesirable because it causes heat and mass transfer limitations which increase reactor fouling and increase coke formation. Fluid coking efficiency is reduced because valuable product yields decrease. Agglomeration is desirable in some industries where it is used to reduce dust problems and stabilize mixtures of various particulate components. This technology is used for the commercial production of pharmaceuticals, detergents, specialty chemicals, fertilizers and food. In both cases, it is important to know whether agglomerates and granules that form during fluidization fragment or remain intact and whether they increase or decrease in size. The objective of this study was to determine methods to predict agglomerate behavior during fluidization. Breakage behavior was predicted using the Stokes deformation number, fluidized bed shear rate, and agglomerate strength. After the properties of the breakage product were estimated, the growth/reduction behavior was estimated using two approaches: polynomial approximation and non-dimensionalization. The predictions were compared with experimental data obtained from previous studies conducted in the absence of reaction. The experimental results were predicted fairly well and the correlations can be used as a predictive tool for agglomerate behavior.

The objective of this study was to derive a simple tool that would predict approximate agglomerate size after fragmentation and the amount of agglomerate material recovered from a fluidized bed. The amount of agglomerate material after fluidization was predicted. Spherical and non-spherical particles were used and no reaction was occurring in the system.Figure optionsDownload as PowerPoint slideResearch highlights
► Liquid-solid agglomerates are undesirable in the fluid coking process.
► Methods were developed to predict agglomerate behavior during fluidization.
► Breakage predicted using deformation number, shear rate, and agglomerate strength.
► Predictions agreed well with measured breakage rates.