Coal Preparation » Fine Coal
The objective of this project was to investigate the potential to improve the desliming performance of fine coal flotation by using a Reflux Flotation Cell (RFC), and to establish increased certainty in the scalability from a laboratory scale unit to a pilot scale unit for future construction of a full scale RFC unit. The RFC applies a fluidization approach to the delivery of wash water and utilises a system of inclined channels below a fluidized bed of bubbles to provide a powerful mechanism for segregating gas bubbles from the downward liquid flow that exits the vessel. The enhanced segregation capacity provided by the inclined channels permits vastly higher rates of wash water and bubble interfacial surface than presently possibly in industry, and superior counter-current washing of the rising bubbles to obtain high quality desliming.
The RFC at both laboratory and pilot scale repeatedly demonstrated a robust separation performance obtaining combustible recovery in accordance with the tree flotation curve for a variety of flotation feeds sourced from hydrocyclone overflow, and other well characterised, difficult to deslime coal streams. Notably, the knee of the tree curve was shown to be readily targeted through independent control of the overflow liquid flux and wash water flux, made possible due to the unique hydrodynamics within the RFC.
The findings of this project address a key problem facing many New South Wales and Queensland coal operations concerning the recovery of fine coal, by demonstrating an effective method for readily rejecting fine slimes from flotation product. Further, the RFC could be extended to the production of ultra-low ash coal. The unique hydrodynamic environment in the RFC allows for the treatment of very fine, high mineral matter coal feeds, such as hydrocyclone overflow, which would otherwise be discharged to tailings dams. The knowledge gained from the pilot trial has provided a confident platform for future construction of a full scale RFC.