X-ray Computed Tomography Evaluation of Crushed Copper Sulfide Ore for Pre-concentration by Ore Sorting

A large portion of the energy consumed in copper concentrators is used to reduce the particle size of the feed by crushing and grinding. The cost of metal production could be reduced if low-grade particles of cm size were removed prior to further processing. Two copper sulfide ore samples (3 x 1 cm) from Arizona were analyzed by micro X-ray computed tomography (Micro-XCT) to determine the grade of copper sulfide in each particle. For copper ore sample A, a significant number of particles contained very low amounts of copper, while some particles had copper sulfide grains of mm size. Based on Micro-XCT, it was expected that 85% of the copper for sample A could be recovered at 65% of mass rejection during pre-concentration by sorting. However, in sample B (a different copper ore), distribution of copper sulfide was dispersed primarily in each ore particle, so for the particle size class of 3 x 1 cm, liberation of copper sulfide and gangue minerals was not significant. In view of the XCT results, dual energy (DE) X-ray radiography was used as a basis for sorting. Previous DE X-ray radiography of a drill core sample demonstrated that this rapid detection method can be used to identify rich or poor Cu-bearing coarse particles. Pilot scale X-ray sorting of sample A (10 x 1 cm) showed 31% rejection of a 0.08% Cu gangue product with a corresponding recovery of 90% copper.

Automated summary

The energy consumed in copper concentrators is largely used to reduce particle size, with potential cost savings by removing low-grade particles before further processing. Micro-XCT and DE X-ray radiography can effectively analyze copper distribution and facilitate metal recovery and mass rejection pre-sorting.