Bond WI as a parameter for the evaluation of ore variability in current grinding plant design practice
Authors • Douglas M. Mazzinghy a, Vladmir K. Alves a, Claudio L. Schneider b* • (a) Vale – Centro de Desenvolvimento Mineral, Brazil • (b) Cetem – Centro de Tecnologia Mineral, Brazil
MOTIVATION Design and scale-up of grinding plants for Green Field projects at Vale’s CDM • Copper ores • Iron ores • Apatite ores • Other projects
OBJECTIVES • To characterize the ore body for milling design • To design a grinding circuit that attends 80% of the ore body • To be able to design the milling circuit using modern simulation and scale-up techniques
The Bond WI • Single parameter that can be easily incorporated in variability analysis • Parameter is required for over 150 drill core samples • Time frame for all grinding tests and conceptual design is usually less than one year
The Bond WI • A good lab can perform 1.5 Bond tests per day totaling 100 days of continuing testing • Sample requirements is large for drill core campaigns • Use of simplified procedures may reduce time requirements significantly (and costs) as well as sample requirements
The Bond WI • The “Anaconda” procedure has been shown to produce statistics that are equal to the complete Bond test (the distributions of BWI have the same average, standard deviation, form, etc….) • Anaconda requires only about 1kg of crushed drill core sample
The Bond WI • A good lab can perform ten Anaconda tests per day
Calculation of the distribution of BWI fr a subset of drill core samples from GFPA
The variability of Anaconda BWI for all drill core samples from project GFPA BWI80 = 19 kWh/t
Q: While the BWI variability campaign is being run do we need to wait for its results to run H-F scale up tests? A: No. We run H-F scale-up tests in a number of samples right at the beginning of the variability campaign. For these samples we also run BWI standard tests.
We pick the sample with the measured BWI that is closest to the value of BWI80 from the variability campaign
And we scale-up the grinding circuit for 80% of the ore body using these parameters
Discussion • The correction is feasible because both parameters (BWI and S1E) are multiplied by mill power at scale-up so that the amount of additional power that would be required by both methods are exactly equal.
Conclusion • BWI may be used as a parameter in assessing ore body variability with advantage. • Simplified BWI techniques can be used as all that is required is the value of BWI80, not the sample that generated this BWI80
Acknowledgements • This work was sponsored by Vale.