Coal Preparation » Fine Coal
A proprietary water injector (WI) was installed and tested on a 1000 mm diameter hydrocyclone (classifying cyclone) at Rix's Creek Coal Preparation Plant in the Hunter Valley, NSW.
Water injection rates of up to 60% of the cyclone underflow water flow rate were evaluated.
No measureable influence of WI was detected, other than a decrease in the underflow percent solids when WI was operational.
The literature review highlighted that previous reported WI data was only for 100 mm cyclones, and operating improvements were generally reported for higher relative density ores. The literature also identified that cyclone geometry and installation orientation had the potential for a larger beneficial influence on cyclone operation than WI.
The literature identified that for cyclone diameters typically employed in coal preparation operations (380 to 500 mm diameter), large operational improvements (increased separation efficiency and underflow percent solids), could be achieved by inclining the cyclone to near-horizontal. This challenges the "conventional" orientation of near-vertical around a central distributor.
Consideration of overall data for large diameter hydrocyclones suggests that they are not well suited to coal preparation applications, since large amounts of coarse (up to 1 mm) particles are misplaced into the cyclone overflow stream. This is likely to have negative impacts on downstream operations like flotation, and result in plant yield losses.