Multiphase solid-liquid and solid-liquid-gas mixing in stirred tanks

Author

Jessyca Susanto, New Jersey Institute of Technology

Document Type

Thesis

Date of Award

5-31-1989

Degree Name

Master of Science in Chemical Engineering - (M.S.)

Department

Chemical Engineering, Chemistry and Environmental Science

First Advisor

Piero M. Armenante

Second Advisor

Dana E. Knox

Third Advisor

Gordon Lewandowski

Abstract

A number of investigations can be found in the literature on the effect of mixing parameters on solid-liquid dispersions in agitated systems. However, the determination of the effect of impeller clearance on minimum suspension speed has received little attention. This work is mainly focused on the determination of the effect of the impeller clearance on N_js (the minimum agitation speed required for complete solid-liquid dispersion) and its corresponding power consumption, using both radial and axial impellers in stirred tanks. In addition, the effect of other significant parameters on N_js was also investigated.

The importance of the impeller clearance is also significant in three-phase, solid-liquid-gas mixing, which has been far less investigated than the solid-liquid case. Thus, the study of the effect of impeller clearance has been extended in this work to three-phase systems. A comparison between the two- and three- phase systems is also reported.

The investigations of mixing parameters for solid-liquid-gas systems have been carried out only by a few researchers, and the relationships obtained so far (if any) are only empirical. In this work, an equation for the calculation of the minimum suspension speed under gassed condition was developed. The final equation obtained is of the form:

ΔN_js = N_js((P_o/P_g)^1/3 - 1)

where: ΔN_js = N_jsg - N_js

N_js = minimum suspension speed without air

N_jsg = minimum suspension under gassed condition

P_o = Power dissipation at N_js condition

P_g = Power dissipation at N_jsg condition

From this equation, the incremental speed requirement, ΔN_js, due to the presence of air can be obtained, provided that the Power dissipation under both aerated and unaerated conditions is known.

A comparison between the experimental results obtained in this work and the values for Nisg predicted by the above equation showed a good agreement. This equation also agrees satisfactorily with the few experimental results previously reP_orted in the literature.

Recommended Citation

Susanto, Jessyca, "Multiphase solid-liquid and solid-liquid-gas mixing in stirred tanks" (1989). Theses. 2913.
https://digitalcommons.njit.edu/theses/2913