Improved Control of Dense Medium Cyclones

The project aimed to improve the control of dense medium cyclone operations in coal preparation plants through evaluation of the feasibility of on-line measurement of dense medium cyclone efficiency via the monitoring of cyclone differentials, cyclone separation density (D50) and cyclone yield and examining their relationships to efficiency measurements including Ep. Coal producers will gain maximum profitability through continuous efficiency measurement as an indication of the rate of decline in circuit efficiency with time thus providing a diagnostic tool to plan interventions such as maintenance.

The project has examined the relationship between Ep yield and D50 over a range of D50's to determine if the slope of the partition curve can be measured. Simple computer simulations of these parameters indicated that the measurement of an efficiency parameter (the slope of the partition curve) on-line was feasible. Direct measurements at BHP Coal washeries at Port Kembla however demonstrated that the relationship between Ep, yield and D50 contains greater variability than was expected from computer modelling and previous measurements.

Following this work, it was determined that further investigation into understanding the sources and effect of variability in Ep and medium and separation density was required to determine if the concept has value to the industry in realistic operating environments. JK Tech were involved through application of a new dense medium cyclone model that incorporates turbulence rather than particle size alone. The model shows that it is possible to determine a change in Ep from graphs of yield versus separation density but, for many of the simulations over a range of parameters, the differences in Ep and hence the differences in the relationship between yield and separation density, could not be measured using the model unless yield could be measured to better than 1% and separation density to better than 0.01 RD units.

In-plant cyclone circuits have a wider range of Ep's than the model suggests and some indications of efficiency changes were observed in plant measurements but the full development of a protocol for measurement requires more development than the project scope permitted.