Thesis
Characterization of gas dispersion in industrial flotation machines
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- Abstract
- The flotation process is designed to collect hydrophobic particles by attachment on to bubbles dispersed in slurry. The effectiveness of the flotation process depends on the properties of the bubble dispersion. For example, the ability of a machine to form small bubbles at a given flow rate of air will control the quantity of surface area available for bubble-particle collision. The gas dispersion, defined for the purposes of this thesis as bubbles suspended in slurry, is quantified by a group of "so-called" gas dispersion parameters including: superficial gas velocity (gas rate, Jg), gas holdup (epsilong), bubble size (Db) and bubble surface area flux (Sb). Cell characterization is a commonly used term in the study of gas dispersion parameters referring to any test designed specifically to increase understanding of the gas dispersion inside a particular machine, including how the dispersion can be manipulated by adjusting the operating variables and how the dispersion parameters vary with location inside a machine. Industrial tests were done to study mechanisms of manipulating the gas dispersion in forced air and self-aerated mechanical flotation machines, demonstrating that gas rate can be used to manipulate the gas dispersion in forced air machines, while froth depth, impeller speed and impeller submergence can be used to manipulate the dispersion in self-aerated machines. Facilitated by the development of the multi-Jg sensor, a technique based on gas rate mapping was developed for down-the-bank sample point selection. Experience using the sensor is described. Based on industrial tests, recommendations regarding sample point selection for down-the-bank optimization are offered. The development of an axial pressure profile sensor is described, facilitating axial investigation of variation in gas dispersion parameters. The proposed technique can be used to evaluate machine operating conditions and to resolve previously unexplained results.
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- 2022-03-18
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- All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated.
- © Jason S. Doucet, 2006
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- McGill University
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MR28592.pdf | 2019-09-20 | Public | Download |