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Design of Impeller Blades for Intensification of Gas-Liquid Dispersion Process in a Stirred Tank

  • Deyin Gu , Zuohua Liu EMAIL logo , Changyuan Tao EMAIL logo , Jun Li and Yundong Wang
Published/Copyright: October 5, 2018

Abstract

Gas-liquid dispersion characteristics were experimentally investigated by measuring largest Lyapunov exponent (LLE), relative power demand (RPD), and local gas holdup in a stirred tank with rigid impellers, rigid-flexible impellers, and punched rigid-flexible impellers. Results showed that punched rigid-flexible impeller could enhance the value of LLE, namely, the chaotic mixing degree of gas-liquid system compared with rigid impeller and rigid-flexible impeller. RPD for punched rigid-flexible impeller was higher than that for rigid impeller and rigid-flexible impeller. The local gas holdup of punched rigid-flexible impeller system was higher than those of rigid impeller system and rigid-flexible impeller system at the same Pg,m. In addition, a long flexible connection piece length could improve the chaotic mixing degree, RPD, and local gas holdup. The aperture diameter of 8 mm and free area ratio of 12 % of punched rigid-flexible impeller were particularly suitable for the gas-liquid dispersion process in this work.

Acknowledgements

The study was supported by the National Natural Science Foundation of China (21576033, 21636004), National key research and development project (2017YFB0603105), National Sci-Tech Support Plan (2015BAB17B01), Chongqing Special Social Undertakings and People's Livelihood Security Science and Technology Innovation (cstc2015shmszx100024), and Central University of Basic Scientific Research Special Project (106112017CDJQJ228808).

Nomenclature

H

liquid height, m

H0

impeller spacing, m

Z

axial distance, m

T

stirred tank diameter, m

D

impeller diameter, m

L1

blade length of rigid impeller, m

L2

rigid blade length of rigid-flexible impeller/punched rigid-flexible impeller, m

L3

flexible connection piece length of rigid-flexible impeller/punched rigid-flexible impeller, m

LLE

largest Lyapunov exponent

m

embedded figure

τ

delay time, s

X1, X2, …, XK, …, XN

time series

Y(t0)

initial point

Y0(t0)

nearest neighbor point

L0

distance between the initial point and the nearest neighbor point

ε

fixed value >0

Q

end point of the time series

M

total iterative number of the tracking evolution process

ti

tracking time, s

ε

local gas holdup

t1i

ith (i = 1, 2, … ) bubble passage time in sensor 1, s

t2i

ith (i = 1, 2, … ) bubble passage time in sensor 2, s

Fr

Froude number, N2D/g

Vs

gas velocity, m·s-1

Pg,m

power consumption per unit mass, W·kg-1

P0

ungassed power consumption, W

Pg

gassed power consumption, W

Np

ungassed power number

Npg

gassed power number

N

impeller rotational speed, s-1

Flg

gas flow number, Qg/ND3

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Received: 2018-02-02
Revised: 2018-04-24
Accepted: 2018-09-22
Published Online: 2018-10-05

© 2018 Walter de Gruyter GmbH, Berlin/Boston

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