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Effect of solid particles on gas holdup in flotation columns
By
Samad Banisi
Published in
On-line phase holdup measurement and analysis in flotation columns, McGill University
at
1994
Direct link:
http://kmpchemmat.ir/pii/32085
Abstract
Gas holdup (volume fraction of gas) is a key parameter for the scale-up, design and performance evaluation of flotation columns. Gas holdup in gas-water and solid-gas-water systems was determined in a continuously operating column (10 cm in diameter and 447 cm in height) by an isolating technique and a conductivity method. The effect of concentration (0-15% v/v), size (95% -53 μm, 90% +75 μm) and type (hydrophilic (quartz, calcite), hydrophobic (coal)) of solid particles on gas holdup was investigated. The presence of solids significantly decreased the gas holdup, by up to 40% relative. The gas holdup decrease increased with increasing solids concentration and decreasing particle size and hydrophilic particles had more effect than hydrophobic ones. Possible mechanisms to explain the effect of solid particles were evaluated based on bubble coalescence, slurry density/viscosity changes, radial profiles, and wake structure effects. It was experimentally shown that bubble coalescence due to the presence of solids was not responsible for the gas holdup reduction. Using the drift flux model it was shown that the slurry density/viscosity changes could not explain the observed gas holdup reduction.
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