MINING CHEMICALS kinetics , high reliability , smaller plant footprint ( capital expense savings ) and a lower unit price than competitors .
The Imhoflot system also has a positive effect on the application of flotation reagents .
The concentrate froth from an Imhoflot cell looks different to the froth from a conventional mechanical cell . While this can take some adaption from the plant operations team when considering dosing , it does bring with it additional flotation performance , according to the company .
“ The finer air bubbles generated in the pulp provide significantly higher bubble surface area per volume of air , resulting in higher bubble loading capacity with which to carry minerals from the pulp to the froth , thus maximising recovery of the collected particles for a given air volume ,” Maelgwyn said .
The Imhoflot cell also only requires a very short residence time due to increased bubbleparticle attachment kinetics and superior froth draining . This minimises the depth of froth required to achieve the needed grade , meaning the operational froth depth is shallower than a mechanical cell requires .
The “ tight froth ” reduces the “ plateau border ” where the froth projects over the launder , which results in lower water recovery and carry-over of entrained gangue , according to Maelgwyn . This entrained water carriage of gangue is a significant factor to consider when floating fine particles .
The quick draining and improved concentrate froth-flowing characteristics mean froth washing and launder water is rarely needed with the Imhoflot . This reduced water content of the fine concentrate cuts capital requirements for downstream solid-liquid separation , while reducing the requirement for de-frothing agents to prevent losses in concentrate thickeners .
Bubble size distribution Maelgwyn ’ s Imhoflot aerator design is based on the three industry-accepted mechanisms for bubble break-up : n Rayleigh-Plateau instability of bubbles in shear flow ; n Impact of liquid accelerated flow inertia according to the Kolmogorov-Hinze approach ; and n Richtmyer-Meshkov instability of bubbles under high acceleration . The patented design generates a spectrum of fine bubble size , resulting in a very high bubble surface area per slurry volume and , thus , high mineral carrying capacities , Maelgwyn said .
The high-intensity environment not only produces very fine bubbles , but , most importantly , creates an intensely turbulent environment to enhance bubble-particle collision frequency and efficiency of the attachment interactions .
“ This gives the reagent-conditioned mineral surface more opportunity to attach to the bubble or for surface nucleation to occur , and hence lower reagent dosing may be required for the same flotation effect ,” Maelgwyn said .
Imhoflot bubble-particle collision occurs within a high-shear zone where the bubbles are still “ young ” and not yet “ contaminated ” with adhered fine gangue minerals , the company explained . This improves the selectivity of reagents as the “ active mineral surface ” is unhindered and reduces the entrainment of fine gangue particles – both of which provide a higher-grade froth concentrate by increasing gangue rejection .
Due to the higher energy conditions used in the Imhoflot compared with other pneumatic cells , there is a high degree of dissolved gas molecules that nucleate to form nano-bubbles in both the gas-saturated pulp and at ultrafine mineral surfaces . This means both historic pathways for bubble-particle attachment are used within the Imhoflot , which benefits the flotation of ultrafine mineral particles .
Particle surface cleaning and reagent optimisation Mineral flotation is a surface-chemistry reaction where reagents interact with the exposed surface of minerals . Therefore , ensuring a clean mineral surface , thinning the film boundary layers and breaking up any surface-adhered mineral phases are key requirements for the selective adsorption of flotation reagents .
The Imhoflot aerator focuses the energy release from the pulp into high-shear zones to generate high-speed turbulent eddies to polish the surface of the particles , removing the
A typical bubble size distribution generated by an Imhoflot reactor for the FineFuture project
boundary film , oxidised minerals and slime coatings from the surface . This optimised reaction environment means lower doses of more selective reagents can be used to achieve superior flotation performance , according to the company .
It is this opportunity to use the higher performance reagents from Axis House at lower
Built for the Toughest Mining Applications
• Designed for High Vibration
• 3.21MP SONY Starvis Sensor
• H . 265 Triple Streaming
• IP67 Water / Dust Resistant
www . opticomintl . com
MAY 2021 | International Mining 55