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Numerical simulations using the Gidaspow and Syamlal-O'Brien drag models have been performed based on the National Energy Technology Laboratory small scale challenge problem for three test cases. Validation tools including statistical moments, spectral analysis, and the autocorrelation function are used to analyze the pressure drop fluctuations. The analyses using these tools reveal a regime change from bubbling/slugging to turbulent flow with increasing superficial gas velocity. 1D discrete wavelet analysis is utilized in the study of the distribution of energy between the macro-, meso-, and microscales and also in the characterization of turbulence quantified in terms of the flatness factor. 1D fast Fourier transform energy spectra are constructed from the predicted and measured particle velocity data and compared. Predicted and measured granular temperatures are found to be in reasonable agreement with literature values. [ABSTRACT FROM AUTHOR]

• Agitation results in a constant bed voidage with periodically fluctuation. • Axial gas mixing can be described by the "open" vessel dispersion model. • Gas flow is divided into two regions by the inner diameter of the helical ribbon. • Flow regimes are classified with an empirical correlation of Re and Fr number. The gas–solid vertical single helical ribbon agitated reactor is widely used in the polypropylene industry. The gas flow and mass transfer determine the heat transfer capacity and product quality. In this work, the pressure drop was measured below and above minimum fluidization velocity (u mf). Then, the axial and radial dispersion coefficients (D L and D R) were estimated below u mf by measuring the step residence time distribution and the stationary radial tracer profiles, respectively. Pressure analysis show the agitation significantly reduces the bed pressure drop, changing the fixed bed below u mf and bubbling bed above u mf to an agitated bed with a periodic voidage. The D L was proportional to the gas velocity, with little influences of the stirring speed. The radial tracer profiles show the bed is divided by the inner diameter of the helical ribbon into the peripheral ascending region and the central descending region, without gas exchange between them. Furthermore. the tracer profiles in the descending region are classified into two types. For type I, the D R , calculated by the plug flow model with radial dispersion, is proportional to the gas velocity, with little effects of stirring speed. Type II shows uniform profiles due to the deflection of the gas flow toward the low pressure area at the inner diameter of helical ribbon. The causes of the two types are explained by the relative size of particle circulation and gas flux. These two flow regimes are quantitatively clarified with an empirical correlation of Re and Fr as flow regime transition boundary, namely dispersed plug flow and perfect mixing flow. With lower Re and higher Fr , it changes from dispersed plug flow to perfect mixing flow. [ABSTRACT FROM AUTHOR]

An induction heating fluidized bed with liquid injection was designed to mimic the exothermic process of particles in industrial olefin polymerization fluidized beds. The effects of liquid injection flow rate on agglomeration behaviors were investigated through the characterization of agglomerate size and mass. Agglomeration mechanisms were proposed based on the experimental data of bed pressure drop, axial temperature distribution, and microscale visualization. Results have revealed that, with the increase of liquid injection flow rate, the agglomeration mechanism was controlled by the solid bridge force, the liquid bridge force, and the cooperative action of them, respectively. Wet agglomerates caused by the liquid bridge force induced local dead zones and provided a good environment for the occurrence of a hot spot and growth of solid bridge, and thus the formation of solid agglomerates. Besides, elevating the liquid injection position and increasing the induction heating power can widen the operation range of the liquid injection flow rate for fluidized bed reactors. [ABSTRACT FROM AUTHOR]