Detectability of Rare Earth Oxides by Dual-Energy X-ray Transmission
Imaging for Sensor-Based Sorting
Kilian Neubert*, Hermann Wotruba
*Unit of Mineral Processing, RWTH Aachen University, Lochnerstrasse 4-20, D-52064 Aachen, Germany,
research associate, Phone: +49-24180-96874, Email: neubert@amr.rwth-aachen.de
Unit of Mineral Processing, RWTH Aachen University, Aachen, Germany, head of department, Phone: +49241 80 96346, Email: wotruba@amr.rwth-aachen.de
Dual-energy X-ray transmission (DE-XRT) imaging is known from safety luggage inspections at airports.
The use of DE-XRT technology for sorting applications in the primary raw materials industry has been the
subject of numerous investigations. Beside other metal ores, X-ray transmission sorting is already used for
the preconcentration of tungsten ore, gold ore and coal. The applicability of DE-XRT sorting is limited to
ore types where differences in metal concentrations are detectable, based on an interpretation of X-ray
images. Metal contents in particles occur in large varieties in terms of concentration, grain sizes, spatial
distribution and mineralogy and therefore influence the X-ray absorption. As a result, each ore has to be
tested individually for its suitability for DE-XRT sorting.
The objective of current research at the Department of Mineral Processing (AMR) at RWTH Aachen
University is to assess the influences on the detectability of rare earth oxides. Two approaches were
followed: (1) Practical test work, based on artificial ore samples of defined compositions and (2)
Computer-based simulation of absorption features of identical particle compositions.
In total, more than 300 artificial samples of various compositions and metal grades were produced and Xray images from DE-XRT sorting were analysed. Results from the DE-XRT sensor were put into
correlation with metal grades and particle sizes, to analyse influences and limits on the detectability of rare
earth oxides.
In addition, a new approach was tested in which the X-ray absorption of particles of various compositions
was determined based on a Monte Carlo (MCNP) simulation. During the simulation, similar compositions,
as used for the artificial samples, were tested and the X-ray absorption behaviour during DE-XRT sorting
was determined. A comparison of results from both approaches is used to assess the applicability of the
MCNP-simulation for the prediction of the X-ray attenuation behaviour during DE-XRT sorting.
KEYWORDS
Sensor-based sorting, Dual energy X-ray transmission sorting, artificial samples, computer-based
simulation, detectability of rare earths