Numerical comparison of two modes of gas-solid riser operation: Fluid catalytic cracking vs CFB combustor--颗粒学报PARTICUOLOGY

Mei, Y., Zhao, M., Lu, B., Chen, S., & Wang, W. (2017). Numerical comparison of two modes of gas-solid riser operation: Fluid catalytic cracking vs CFB combustor. Particuology, 31, 42-48. https://doi.org/10.1016/j.partic.2016.05.007

Numerical comparison of two modes of gas-solid riser operation: Fluid catalytic cracking vs CFB combustor

Yifeng Mei ^{a d 1}, Mingzhao Zhao ^{a b 1}, Bona Lu ^a, Sheng Chen ^c, Wei Wang ^{a d *}

a State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
b School of Chemical Engineering, Sichuan University, Chengdu 610065, China
c State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, China
d University of Chinese Academy of Sciences, Beijing 100049, China

10.1016/j.partic.2016.05.007

Volume 31, April 2017, Pages 42-48

Received 12 March 2016, Revised 22 April 2016, Accepted 5 May 2016, Available online 27 August 2016, Version of Record 9 March 2017.

E-mail: wangwei@ipe.ac.cn; chesacas@qq.com

Highlights

• FCC and CFBC modes of operation were compared through CFD simulation.

• FCC mode of operation needs longer time to reach steady state during the choking transition.

• FCC mode is easier to cause operation instability in particular for longer risers.

Abstract

Two modes of gas-solid riser operation, i.e., fluid catalytic cracking (FCC) and circulating fluidized bed combustor (CFBC), have been recognized in literature; particularly in the understanding of choking phenomena. This work compares these two modes of operation through computational fluid dynamics (CFD) simulation. In CFD simulations, the different operations are represented by fixing appropriate boundary conditions: solids flux or solids inventory. It is found that the FCC and CFBC modes generally have the same dependence of solids flux on the mean solids volume fraction or solids inventory. However, during the choking transition, the FCC mode of operation needs more time to reach a steady state; thus the FCC system may have insufficient time to respond to valve adjustments or flow state change, leading to the choking. The difference between FCC and CFBC systems is more pronounced for the systems with longer risers. A more detailed investigation of these two modes of riser operation may require a three-dimensional full loop simulation with dynamic valve adjustment.

Graphical abstract

Keywords

Fluidization; Computational fluid dynamics; Simulation; Fluid catalytic cracking; Circulating fluidized bed; Choking

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