Coal Preparation

Full Scale Trial of the REFLUX™ Flotation Cell

Coal Preparation » Fine Coal

Published: October 23Project Number: C23045

Get ReportAuthor: Simon Iveson, Joshua Sutherland, Matthew Cole, Daniel Borrow, James Zhou, Kevin Galvin | The University of Newcastle

A 2 m diameter REFLUX Flotation Cell™ (RFC™) was installed at a Hunter Valley mine site and successfully operated during several campaigns in 2021 and 2022. The technology delivered strong performance comparable to or better than the tree flotation curve across a wide range of feed flowrates up to 450 m3/h, which is approximately four times the feed rate of similarly sized conventional flotation technologies.

There are two key findings from the work - functionality and performance:


Functionality: A unique feature of the RFC™ when compared with conventional flotation technologies is the decoupling of the underflow rate from the gas flux. This work has been successful in clearly demonstrating the powerful nature of this decoupling in the full‐scale unit, with the ability to limit the excess water reporting to the product (with strong wash water), and hence secure low product ashes while maintaining consistent recovery. In effect, the approach permits the operator to shift the separation from high to lower product ashes by adjusting the product volumetric rate.


Performance: When operated correctly, the unit performed better than the industry standard tree flotation curve test (AS 4156.2.1 conducted by an external testing laboratory). The unit demonstrated robust consistent performance across a wide range of feed rates, with only a modest drop in performance as the feed rate increased from 200 m3/h up to over 400 m3/h (the highest feed rate used was 460 m3/h due to capacity limitation of the underflow pump). Across the 2 m diameter of the unit, these rates are equivalent to feed fluxes of 2 to 4 cm/s, significantly higher than the ~ 1 cm/s feed flux limitation of conventional flotation technologies. The unit consistently produced clean products. Combustible recoveries of above 60 % were obtained at < 250 m3/h feed rates. At higher feed rates, recoveries were of the order 50 %, on what were mostly high‐ash feeds.

The full report outlines more broadly the operational performance observed across a wide range of conditions covering different feed rates, gas rates, and frother dosages. There was no discernible effect identified when the frother dosage was varied above 10 ppm. Certain other unexpected issues, unrelated to the technology itself, were also identified and reported. Overall, based on the earlier laboratory work, the RFC™ performed as expected.


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