Quantification of the Performance of Agitators In Stirred Vessels (original) (raw)
Related papers
2016
NOVEL EXPERIMENTAL METHOD FOR THE DETERMINATION OF THE MINIMUM AGITATION SPEED FOR SOLIDS SUSPENSION IN FLATBOTTOMED STIRRED TANK REACTORS By Shriarjun Shastry Knowledge of the minimum agitation speed, Njs, required to suspend finely divided solids in vessels stirred by an impeller is a critical parameter to properly operate industrial tanks in a large number of industrial operations. The most common experimental approach to measure Njs is that of Zwietering’s (Chem. Eng. Sci., 1958, 8, 244-253), consisting of visually inspecting the tank bottom and visually determining the impeller agitation speed at which the solids are observed to rest on the tank bottom for no more than 1-2 seconds before being swept away. This method is quite reliable, but a method not relying on the operator would clearly be preferred. Therefore, the main objective of this work was to develop a simple, repeatable, and observer-independent method to determine Njs for a variety of agitation systems and agitation...
Liquid-Liquid Mixing in Stirred Vessels: A Review
Chemical Engineering Communications, 2013
Liquid-liquid mixing is a key process in industries that is commonly accomplished in mechanical agitation systems. Liquid-liquid mixing performance in a stirred tank can be evaluated by various parameters, namely minimum agitation speed, mixing time, circulation time, power consumption, drop size distribution, breakup and coalescence, interfacial area, and phase inversion. The importance of these liquid-liquid mixing parameters, the measurement method, and the results are discussed briefly. Input parameters such as impeller type, power number, flow pattern, number of impellers, and dispersed phase volume fraction, in addition to physical properties of phases such as viscosity and density, are reviewed. Scale-up aspects are also included. © 2013 Copyright Taylor and Francis Group, LLC. http://www.tandfonline.com/doi/pdf/10.1080/00986445.2012.717313
Particle distribution in unbaffled stirred vessels
Chemical engineering transactions, 2017
The present work is devoted to providing an insight into the solid-particle distribution within top-covered unbaffled stirred tanks via purposely collected local experimental data. Experiments were carried out on a labscale unbaffled stirred tank by making use of a recently introduced technique named Laser Sheet Image Analysis (LSIA). In its original formulation, the technique includes an image post-processing procedure to delete reflection effects on results. In the framework of the present work, a method combining the use of purposely produced fluorescent particles and a suitable camera high pass filter was devised and presented. Results collected with (new method) and without (old fashion) fluorescent particles were compared for comparison purposes and a satisfactory agreement was found, thus validating both the procedures devised to delete reflections. LSIA technique in the novel version was used to investigate the distribution of solid particles at different agitation speeds in...
An experimental and CFD investigation into the mixing in a closed system stirred vessel
2014
An investigation has been undertaken into the mixing mechanisms involved in a closed tank stirred vessel utilising a wide paddle agitator, for fluids in the viscosity range of 1 to 5.5 mPa s. In particular, the effect of fill depth on the mixing time has been considered, as this has a direct impact on the usability of the mixing process equipment for scaled-down batch production. Experimental work has been undertaken and this has been used to develop a suitable computational fluid dynamics (CFD) model which implements the Multiple Reference Frame (MRF) approach with the addition of a virtual tracer used to calculate mix time. A study into whether laminar or turbulent models are required and an appropriate method for the implementation of turbulence has been established. The results allow identification of the optimum ratio of fill depth to paddle height to be established. Additionally, the developed CFD model will allow for further investigation into the effects of other process par...