Abstract
Near-infrared (NIR) spectroscopy sorting technology is incorporated in an
automated optical mineral sorter that can discriminate between materials
using the differences in characteristics when exposed to near-infrared
radiation. During September 2014 to April 2015, a pilot plant that utilized
NIR technology to discriminate between kimberlite and waste materials
was commissioned to determine the viability of including this technology
in the diamond winning process flow sheet at Cullinan Diamond Mine. The
plant was used to minimize the waste content in the size fraction -70+35
mm that reports to the crushing section and then to the dense media
separation process. This paper describes the initial test work, conducted at
Mintek, that led to the decision to conduct a pilot-scale study. The
mineralogical characterization of the feed and product streams to establish
the sorting criteria and the operational data obtained during the pilot plant
campaign are described. The results indicated a good possibility of discriminating
between the kimberlite and waste material using NIR technology.
However, the consistency of discrimination was not good enough to avoid
the risk of potential diamond loss. Furthermore, a lower than expected
availability of the machine reduced the throughput capabilities.