Journal of Shandong University(Engineering Science) ›› 2021, Vol. 51 ›› Issue (4): 71-76, 83.doi: 10.6040/j.issn.1672-3961.0.2020.296

• Mechanical, Energy and Power Engineering • Previous Articles     Next Articles

Gas-liquid mixing in a dual grid-disc impeller stirred vessel

Cuixun ZHANG1(),Mingjian CAO1,Fengling YANG2,*()   

  1. 1. Shandong Tianli Energy Co., Ltd., Jinan 250100, Shandong, China
    2. School of Mechanical Engineering, Shandong University, Jinan 250061, Shandong, China
  • Received:2020-07-22 Online:2021-08-20 Published:2021-08-18
  • Contact: Fengling YANG E-mail:zhangcx1208@163.com;fly@sdu.edu.cn

Abstract:

In order to improve the gas-fluid mixing efficiency in the stirred vessel, by replacing the solid disc of standard Rushton impeller (RT) with a grid disc, the grid-disc Rushton impeller (RT-G) was designed. Grid independence test was completed. Gas holdup distributions of dual RT were numerically studied by the computational fluid dynamics (CFD) technique and compared with the literature data so as to validate the reliability of the numerical model and simulation method. The same numerical strategy was used to investigate the gas-liquid hydrodynamics of dual RT-G. Results were compared with those of dual RT and it was found that, under the operating condition studied here, dual RT-G had the same double-circulation flow field structure as RT. However, fluid axial velocity around the two RT-G impellers and axial pumping capacity could be enhanced, which contributed to improve the gas distribution state especially in regions adjacent to the impellers, between the upper and lower impeller, as well as in the top area of the stirred vessel. In terms of power consumption, the power number of dual RT-G before gassing was about 5% lower than that of dual RT, which indicated that RT-G was more energy-saving. The relative power demand (RPD) of dual RT-G after gassing was about 8% higher than dual RT, and accordingly was more efficient in gas dispersing.

Key words: stirred vessel, grid-disc impeller, gas-liquid flow, CFD, power consumption

CLC Number: 

  • TQ027

Fig.1

The stirred system and grid-disc impeller"

Fig.2

Grid independence test"

Fig.3

Comparisons of the gas holdups at r=77.75 mm in the mid-baffle plane of the dual RT stirred vessel"

Fig.4

Comparisons of the folw patterns in the mid-baffle plane of the stirred vessel"

Fig.5

Comparisons of axial velocities in the mid-baffle plane of the stirred vessel"

Fig.6

Gas holdups in the dual RT stirred vessel"

Fig.7

Gas holdups in the dual RT-G stirred vessel"

1 NIENOW A W . Stirring and stirred-tank reactors[J]. Chemie Ingenieur Technik, 2014, 86 (12): 1- 13.
2 MONTANTE G , LEE K C , BRUCATO A , et al. An experimental study of double-to-single-loop flow pattern transition in stirred vessels[J]. Canadian Journal of Chemical Engineering, 1999, 77 (4): 649- 659.
doi: 10.1002/cjce.5450770405
3 MONTANTE G , LEE K C , BRUCATO A , et al. Numerical simulations of the dependency of flow pattern on impeller clearance in stirred vessels[J]. Chemical Engineering Science, 2001, 56 (12): 3751- 3770.
doi: 10.1016/S0009-2509(01)00089-6
4 SMITH J M. Reversible mixing impeller: US5316443[P]. 1999-05-31.
5 BAKKER A, OHIO D. Impeller assembly with asymmetric concave blades: US5791780[P]. 1998-08-11.
6 GELVES R , DIETRICH A , TAKORS R . Modeling of gas-liquid mass transfer in a stirred tank bioreactor agitated by a Rushton turbine or a new pitched blade impeller[J]. Bioprocess and Biosystems Engineering, 2014, 37 (3): 365- 375.
doi: 10.1007/s00449-013-1001-8
7 GU D , LIU Z , TAO C , et al. Numerical simulation of gas-liquid dispersion in a stirred tank agitated by punched rigid-flexible impeller[J]. International Journal of Chemical Reactor Engineering, 2019, 17 (4): 20180196.
8 熊黠, 刘作华, 谷德银, 等. 刚柔组合桨强化粉煤灰酸浸搅拌槽内固液混沌混合[J]. 化工学报, 2019, 70 (5): 1693- 1701.
XIONG Xia , LIU Zuohua , GU Deyin , et al. Chaotic mixing process of fly ash in acid leaching tank intensified by rigid-flexible impeller[J]. CIESC Journal, 2019, 70 (5): 1693- 1701.
9 LUESKE J , KAR K , PIRAS L , et al. Power draw and gas-liquid mass transfer characteristics of a stirred tank reactor with draft tube configuration[J]. Chemical Engineering and Technology, 2015, 38 (11): 1993- 2001.
doi: 10.1002/ceat.201500071
10 FALLEIRO L H , ASHRAF A B . Computational modeling of hydrodynamics and mixing in a batch stirred vessel[J]. Chemical Engineering Communications, 2021, 208 (6): 883- 892.
doi: 10.1080/00986445.2019.1694919
11 FOUNTAIN G O , KHAKHAR D V , OTTINO J M . Visualization of three-dimensional chaos[J]. Science, 1998, 281, 683- 686.
doi: 10.1126/science.281.5377.683
12 ALVAREZ M M , ARRATIA P E , MUZZIO F J . Laminar mixing in eccentric stirred tank systems[J]. Canadian Journal of Chemical Engineering, 2002, 80 (4): 546- 557.
13 WANG S , WU J , OHMURA N . Inclined-shaft agitation for improved viscous mixing[J]. Industrial and Engineering Chemistry Research, 2013, 52 (33): 11741- 11751.
doi: 10.1021/ie401003s
14 OLDSHUE J Y , HIRSCHLAND H E , GRETTON A T . Blending of low-viscosity liquids with side-entering mixers[J]. Chemical Engineering Progress, 1956, 52 (11): 481- 484.
15 KOMODA Y , INOUE Y. HIRATA Y . Mixing performance by reciprocating disk in cylindrical vessel[J]. Journal of Chemical Engineering of Japan, 2000, 33 (6): 879- 885.
doi: 10.1252/jcej.33.879
16 LAMBERTO D J , MUZZIO F J , SWANSON P D , et al. Using time-dependent RPM to enhance mixing in stirred vessels[J]. Chemical Engineering Science, 1996, 51 (5): 733- 741.
doi: 10.1016/0009-2509(95)00203-0
17 YAO W G , SATO H , TAKAHASHI K , et al. Mixing performance experiments in impeller stirred tanks subjected to unsteady rotational speeds[J]. Chemical Engineering Science, 1998, 53 (17): 3031- 3040.
doi: 10.1016/S0009-2509(98)00116-X
18 YANG F L , ZHOU S J , ZHANG C X . Turbulent flow and mixing performance of a novel six-blade grid disc impeller[J]. Korean Journal of Chemical Engineering, 2015, 32 (5): 816- 825.
doi: 10.1007/s11814-014-0255-4
19 ALVES S S , MAIA C I , VASCONCELOS J M T . Experimental and modelling study of gas dispersion in a double turbine stirred tank[J]. Chemical Engineering Science, 2002, 57 (3): 487- 496.
doi: 10.1016/S0009-2509(01)00400-6
20 KERDOUSS F , BANNARI A , PROULX P . CFD modeling of gas dispersion and bubble size in a double turbine stirred tank[J]. Chemical Engineering Science, 2006, 61 (10): 3313- 3322.
doi: 10.1016/j.ces.2005.11.061
21 RANNADE V V , PERRARD M , XUREB C , et al. Influence of gas flow rate on the structure of trailing vortices of a Rushton turbine[J]. Chemical Engineering Research and Design, 2001, 79 (8): 957- 964.
doi: 10.1205/02638760152721190
22 NG K , FENTIMAN N J , LEE K C , et al. Assessment of sliding mesh CFD predictions and LDA measurements of the flow in a tank stirred by a Rushton impeller[J]. Chemical Engineering Research and Design, 1998, 76 (6): 737- 747.
doi: 10.1205/026387698525315
23 DERKSEN J J , DOELMAN M S , VAN DEN AKKER H E A . Three-dimensional LDA measurements in the impeller region of a turbulently stirred tank[J]. Experiments in Fluids, 1999, 27 (6): 522- 532.
doi: 10.1007/s003480050376
24 TAGHAVI M , ZADGHAFFARI R , MOGHADDAS J , et al. Experimental and CFD investigations of power consumption in a dual Rushton turbine stirred tank[J]. Chemical Engineering Research and Design, 2011, 89 (3): 280- 290.
[1] Xin LIU,Fengling YANG. Vibration characteristics of flexible-blade Rushton impeller [J]. Journal of Shandong University(Engineering Science), 2020, 50(5): 50-55.
[2] Meiting LI,Wei LI,Xiaoguang LI,Fengling YANG. Laminar flow field characteristics in the stirred vessel equipped with an eccentric-shaft impeller [J]. Journal of Shandong University(Engineering Science), 2019, 49(4): 93-98, 107.
Viewed
Full text


Abstract

Cited

  Shared   
  Discussed   
[1] WANG Su-yu,<\sup>,AI Xing<\sup>,ZHAO Jun<\sup>,LI Zuo-li<\sup>,LIU Zeng-wen<\sup> . Milling force prediction model for highspeed end milling 3Cr2Mo steel[J]. JOURNAL OF SHANDONG UNIVERSITY (ENGINEERING SCIENCE), 2006, 36(1): 1 -5 .
[2] ZHANG Yong-hua,WANG An-ling,LIU Fu-ping . The reflected phase angle of low frequent inhomogeneous[J]. JOURNAL OF SHANDONG UNIVERSITY (ENGINEERING SCIENCE), 2006, 36(2): 22 -25 .
[3] LI Kan . Empolder and implement of the embedded weld control system[J]. JOURNAL OF SHANDONG UNIVERSITY (ENGINEERING SCIENCE), 2008, 38(4): 37 -41 .
[4] SHI Lai-shun,WAN Zhong-yi . Synthesis and performance evaluation of a novel betaine-type asphalt emulsifier[J]. JOURNAL OF SHANDONG UNIVERSITY (ENGINEERING SCIENCE), 2008, 38(4): 112 -115 .
[5] KONG Xiang-zhen,LIU Yan-jun,WANG Yong,ZHAO Xiu-hua . Compensation and simulation for the deadband of the pneumatic proportional valve[J]. JOURNAL OF SHANDONG UNIVERSITY (ENGINEERING SCIENCE), 2006, 36(1): 99 -102 .
[6] LAI Xiang . The global domain of attraction for a kind of MKdV equations[J]. JOURNAL OF SHANDONG UNIVERSITY (ENGINEERING SCIENCE), 2006, 36(1): 87 -92 .
[7] YU Jia yuan1, TIAN Jin ting1, ZHU Qiang zhong2. Computational intelligence and its application in psychology[J]. JOURNAL OF SHANDONG UNIVERSITY (ENGINEERING SCIENCE), 2009, 39(1): 1 -5 .
[8] CHEN Rui, LI Hongwei, TIAN Jing. The relationship between the number of magnetic poles and the bearing capacity of radial magnetic bearing[J]. JOURNAL OF SHANDONG UNIVERSITY (ENGINEERING SCIENCE), 2018, 48(2): 81 -85 .
[9] WANG Bo,WANG Ning-sheng . Automatic generation and combinatory optimization of disassembly sequence for mechanical-electric assembly[J]. JOURNAL OF SHANDONG UNIVERSITY (ENGINEERING SCIENCE), 2006, 36(2): 52 -57 .
[10] LI Ke,LIU Chang-chun,LI Tong-lei . Medical registration approach using improved maximization of mutual information[J]. JOURNAL OF SHANDONG UNIVERSITY (ENGINEERING SCIENCE), 2006, 36(2): 107 -110 .