Modelling of the mixing characteristics and flotation kinetics of the collection zone in flotation columns

• Main Author: Mills, Peter John Temple
• Other Authors: O'Connor, Cyril T
• Format: Doctoral Thesis
• Language: English
• Published: University of Cape Town 2016
• Subjects: Chemical Engineering
• Online Access: http://hdl.handle.net/11427/21987

Bibliography: pages 181-189. === Column flotation has gained worldwide acceptance in the minerals processing industry in the past decade. This has been due the operating characteristics of flotation columns which can produce improved grades and recoveries over conventional cells. Added to this, flotation columns are both simple to operate and generally less expensive than the equivalent requirement of conventional cells. Flotation columns are able to produce improved results due to a deep washed froth phase and a quiescent pulp phase in which the pulp interacts countercurrently with the air bubbles. Models describing the behaviour of particles in both of these phases have been developed over the past decade. The present study focusses specifically on the pulp phase and models presently used to describe the pulp zone hydrodynamics and kinetics are evaluated and improved. The hydrodynamics of the pulp or collection zone are evaluated using data obtained from three residence time distribution (RTD) studies performed on two pilot columns (5.4cm and 5.8cm diameter) and an industrial column (120cm diameter). Sodium chloride liquid tracers as well as radioactively labelled solid and liquid tracers were used in the RTD studies. In the study performed on a pilot column using the salt tracer the degree of mixing was found to increase both with increasing gas rate at constant bubble size and decreasing bubble size at a constant gas rate. This increase in mixing is attributed to the increase in the number of bubble$ and the subsequent increase in the tracer-bubble interactions. By extrapolating this result to industrial columns it is clear that flotation columns, which have smaller and substantially more bubbles, will be more mixed than bubble columns.