Comparison of macro-mixing characteristics of a stirred tank with different impellers

doi:10.11949/j.issn.0438-1157.20180948

Abstract

Abstract:

In order to enrich the data of centripetal impeller performance, the macro-mixing characteristics of stirred tanks installed with centripetal impeller, Rushton impeller, three pitched blade impeller and punched blade impeller were systematically studied. The influence of impeller speed, impeller off-bottom clearance, impeller type on mixing time, power and mixing efficiency of the stirred tank was investigated. The results show that the mixing time of the four impellers are all decreased with increasing impeller speed, and the power are all increased. At the same impeller speed, the power of the Rushton impeller is the highest, and the three pitched blade impeller is the lowest. The power of centripetal impeller is only a little higher than that of the three pitched blade impeller. However, the macro-mixing time of the four impellers shows different trends with increasing the impeller off-bottom clearance. The importance of the factor affecting the macro-mixing efficiency is impeller speed >impeller type > impeller off-bottom clearance. Among the four impellers, the overall evaluation of the macro-mixing efficiency of the centripetal impeller is the highest. The research results of this paper can accumulate experimental data for the industrial application of new impellers such as centripetal impeller, and provide theoretical basis for its optimization design and scale-up.

Key words: stirred vessel, centripetal impeller, mixing, power, mixing efficiency, optimal design

摘要：

为了丰富对向心桨的混合特性的认识，比较了向心桨、Rushton桨、三斜叶桨和穿流桨的单层桨搅拌槽内的宏观混合特性，考察了搅拌转速、桨叶离底高度对搅拌槽混合时间和功率特性的影响。结果表明，四种桨的宏观混合时间均随着搅拌转速的增加而减少，搅拌功率均随转速的增加逐渐增大。当转速相同时，四种桨型中Rushton桨的功率消耗最大，三斜叶桨功率消耗最小，向心桨的功率消耗仅仅比三斜叶桨高。桨叶离底高度的变化对四种桨型的混合时间和功率的影响不尽相同。混合效率的影响因素大小顺序为：搅拌转速>桨型>桨叶离底高度。在考察的四种桨型中，向心桨的混合效率最高。研究成果可为向心桨等新型搅拌桨的工业应用积累实验数据，为其优化设计和放大提供理论依据。

关键词: 搅拌容器, 向心桨, 混合, 功率, 混合效率, 优化设计

CLC Number:

TQ 028.8

Ting LI, Zhuotai JIA, Qinghua ZHANG, Chao YANG, Zaisha MAO. Comparison of macro-mixing characteristics of a stirred tank with different impellers[J]. CIESC Journal, 2019, 70(1): 32-38.

李挺, 贾卓泰, 张庆华, 杨超, 毛在砂. 几种单层桨搅拌槽内宏观混合特性的比较[J]. 化工学报, 2019, 70(1): 32-38.

Figures/Tables 11

Fig.1 Experimental setup

Fig.2 Structure of four impellers

Fig.3 Effect of impeller speed on mixing time

Fig.4 Effect of impeller speed on power

Fig.5 Effect of impeller speed on power number

Fig.6 Correlation between impeller speed and WV

Fig.7 Effect of impeller clearance on mixing time

Fig.8 Effect of impeller clearance on power

Fig.9 Effect of impeller clearance on power number

Fig.10 Correlation between impeller clearance and WV

Fig.11 Correlation between mixing time and PV

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