A dynamic model for level prediction in aerated tanks
File(s)
Accepted version
Author(s)
Shean, B
Hadler, K
Neethling, S
Cilliers, JJ
Type
Journal Article
Abstract
Stirred aerated tanks are a key unit operation in many industries, including froth flotation. Reliable and robust level control is of great importance in maintaining steady operation for successful implementation of higher level optimising control strategies, particularly when such tanks are arranged in series. When changes are made to the rate of aeration, there is a corresponding change in the pulp bubble size and gas holdup (the volume fraction of air in the tank), and consequently the pulp height. Stable operation of flotation tanks must, therefore, include the effect of air rate on pulp height in level control systems, especially if air rate is being actively controlled. In this paper, a model is developed from first principles to link the change in gas holdup with variation in air rate under dynamic conditions, accounting for the variability in gas holdup with height that results from differences in gas compressibility. This is validated experimentally. In order to test the model, experiments were carried out using a 70 L laboratory tank comprising water and reagent systems. For both simple and complex changes in air rate, the model showed good agreement with the experimental results when predicting the change in pulp height at steady state. Under dynamic conditions, the experimental system exhibited a slightly slower response than is predicted by the model; this is likely to be due to the well mixed assumption not being adequately met. This model provides a method to improve the operating stability of aerated tanks through better modelling of the dynamic pulp height changes that result from changes in air flowrate. In flotation tanks, this will enable greater control over froth height, which has been found to affect significantly mass pull, froth stability and flotation performance.
Date Issued
2018-08-15
Date Acceptance
2018-05-26
Citation
Minerals Engineering, 2018, 125 (1), pp.140-149
ISSN
0892-6875
Publisher
Elsevier
Start Page
140
End Page
149
Journal / Book Title
Minerals Engineering
Volume
125
Issue
1
Copyright Statement
© 2018 Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/
Sponsor
Technological Resources PTY Ltd
Identifier
https://www.sciencedirect.com/science/article/pii/S0892687518302565?via%3Dihub#!
Grant Number
Project EF
Subjects
Science & Technology
Technology
Physical Sciences
Engineering, Chemical
Mineralogy
Mining & Mineral Processing
Engineering
Froth flotation
Flotation control
Gas holdup
Level control
Bubble size
MECHANICAL FLOTATION CELLS
GAS DISPERSION
BUBBLE-SIZE
FROTH DEPTH
CONTROL-SYSTEM
AIR RECOVERY
PERFORMANCE
CONCENTRATORS
0306 Physical Chemistry (incl. Structural)
0904 Chemical Engineering
0914 Resources Engineering and Extractive Metallurgy
Mining & Metallurgy
Publication Status
Published
Date Publish Online
2018-06-15