CFD study: Effect of pulsating flow on gas-solid hydrodynamics in FCC riser
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Gas-solid flow in a fluid catalytic cracking (FCC) riser exhibits poor mixing in the form of a core-annulus flow pattern and a dense bottom/dilute top distribution of solids. To enhance gas-solid mixing, studies on dense fluidized beds have suggested using a pulsating flow of gas. The present study investigates the effect of pulsating flow on gas-solid hydrodynamics inside the FCC riser employing computational fluid dynamics. Two flow conditions are investigated: a cold flow of air-FCC catalyst in a pilot-scale riser and a reactive flow in an industrial-scale FCC riser. In the cold-flow riser, pulsating flows cause the slug flow of solids and thus increase the average solid accumulation in the flow domain and solid segregation towards the wall. In the industrial FCC riser, pulsating flows produce radial profiles that are more homogeneous. Pulsating flows further improve the conversion and yield in the initial few metres of height. At 7. m, the conversion from pulsating flow is 59%, compared with 44% in without pulsating flow. The results and analysis presented here will help optimize flow conditions in the circulating fluidized bed riser, in not only FCC but also applications such as fast pyrolysis and combustion.
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Shah, Milinkumar T. (2011)Gas-solid risers have been extensively used as multiphase reactors in circulating fluidized bed (CFB) system such as fluid catalytic cracking (FCC) and Circulating fluidized bed combustion (CFBC). In FCC, a riser facilitates ...
Shah, Milin; Utikar, Ranjeet; Pareek, Vishnu; Evans, G.; Joshi, J. (2016)Design and scale-up of fluid catalytic cracking (FCC) riser is still largely empirical, owing to limited understanding of inherent multiphase flow in this equipment. The multiphase flow of FCC riser has therefore been ...
Shah, Milin; Utikar, Ranjeet; Pareek, Vishnu; Tade, Moses; Evans, G. (2014)Gas–solid flows in a riser have often been investigated by using the Eulerian–Eulerian (E–E) model. The E–E model consists of mass and momentum conservations equations, along with equations for boundary conditions and ...