CFD study: Effect of pulsating flow on gas–solid hydrodynamics in FCC riser--颗粒学报PARTICUOLOGY

Shah, M. T., Utikar, R. P., & Pareek, V. K. (2017). CFD study: Effect of pulsating flow on gas–solid hydrodynamics in FCC riser. Particuology, 31, 25-34. https://doi.org/10.1016/j.partic.2016.07.002

CFD study: Effect of pulsating flow on gas–solid hydrodynamics in FCC riser

Milinkumr T. Shah ^*, Ranjeet P. Utikar, Vishnu K. Pareek

Department of Chemical Engineering, Curtin University, WA, Australia

10.1016/j.partic.2016.07.002

Volume 31, April 2017, Pages 25-34

Received 15 April 2016, Revised 1 July 2016, Accepted 20 July 2016, Available online 28 October 2016, Version of Record 9 March 2017.

E-mail: milinkumar.shah@curtin.edu.au; milinkumar.shah@gmail.com

Highlights

• Effect of pulsating flow on gas–solid flow and performance of FCC riser was investigated.

• CFD simulations of both cold flow and reactive flow in FCC riser were conducted.

• Pulsating flow resulted in a slug flow of solids with more homogeneous radial profiles.

• Pulsating flow also significantly increased feedstock conversion in initial riser height.

Abstract

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.

Graphical abstract

Keywords

Fluid catalytic cracking; Riser; Pulsating flow; Computational fluid dynamics

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