Abstract
Fluid catalytic cracking (FCC) processes have been used widely in petroleum refineries. FCC regenerators play important roles for maintaining catalyst activity and supply the reaction heat. The regenerator efficiency is mainly connected to the hydrodynamics of the fluidized bed, because the gas and solid behaviors are very important factors in mass and heat transfer. The void properties, such as chord length, rising velocity, frequency, and fraction, have been determined in a large cold flow model (0.48 m-ID × 6.4 m-high) of the FCC regenerator, which was geometrically scaled down from a commercial FCC unit. The local void chord length, rising velocity, frequency, and fraction exhibit their maximum value along the radial direction of the bed. The cross-sectional mean void chord length, rising velocity, and fraction increase and the cross-sectional mean void frequency decreases with height in the bed. The variation of void properties in the FCC regenerator with turbulent fluidized bed exhibit similar trends to those in a bubbling fluidized bed. The void properties in the FCC regenerator have been correlated with the experimental parameter on the basis of bubbling bed concept. The predicted void velocities based on the correlations agreed well with the experimental data from present and previous studies. A modified bubbling fluidized bed model could describe the void properties in the regenerator operated in turbulent fluidized bed regime.
Highlights
Fluid catalytic cracking (FCC) processes have been used widely in petroleum refineries to convert the high-molecular weight hydrocarbons into more valuable propylene, gasoline, and gas oil, etc. [1].In the process, an FCC regenerator is utilized to burn off the coke deposit on catalysts surface with air for maintaining catalyst activity at a useful level and supply heat for the FCC reaction in the riser
The obtained area-mean void chord lengths from this study and literature in Table 2 on the turbulent fluidized bed with FCC particles have been correlated with experimental parameters as following
An existing bubbling bed model was found to be sufficient to describe the void properties in the dense bed of the regenerator operated at turbulent fluidization regime
Summary
Fluid catalytic cracking (FCC) processes have been used widely in petroleum refineries to convert the high-molecular weight hydrocarbons into more valuable propylene, gasoline, and gas oil, etc. [1]. The non-intrusive methods such as laser sheet, tomography, and nuclear magnetic resonance techniques measure the whole image of the particles flow in a wide range [11]. They are mostly used for small diameter column due to the limitation of signal penetration [5]. The void properties in the turbulent fluidized bed have been determined by the optical fiber probe technique in a large cold flow model, which was geometrically scaled down from the two-staged regenerator in a commercial 58,000 B/D FCC unit. The obtained void properties have been correlated with the experimental parameters from present and previous studies
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