Limestone

Blue and white limestone can be seperated from waste efficiently to reduce selective mining and upgrade product quality.

White limestone is used for filler and therefore achieves higher prices if the product is bright. The Secondary COL separates white limestone from a ROM with 30% dilution with a purity of approx 99%.

In blue limestone volcanic dykes reduce the quality and make selective mining inevitable. The blue limestone concentrate produced with a Secondary COL has typically >95% blue limestone. Additionally, the reject or tails of the sorter are suitable for aggregate plants as they contain >82% volcanic dyke.

Limestone sorting case study

Limestone is mined near Daniëlskuil in South Africa. The African company Idwala Lime has its largest production facility for high grade limestone here, which is delivered to the building materials and chemical industries. The largest limestone plant of the African company produces a million tons of quicklime a year. The quality requirements are high – the silicate content must be under one percent. 75 percent of the deposits is a low-grade quality limestone. Those parts which do not meet the product specification have until now been disposed of at a large waste rock dump. However, 60 percent of this wasted material consists of high grade limestone. This has been a loss in two respects. On the one hand, work and energy has been expended to mine these limestone deposits and, on the other, valuable raw material has remained unused.

With the installation of a CommodasUltrasort machine Idwala Lime took multiple steps towards increasing its production efficiency. Optical sorting now allows limestone to be extracted from the previously discarded layers of low-grade limestone. The sorting plant has thus significantly increased the limestone reserve in so far as the lifetime of the mine has doubled. Nowadays less material needs to be mined in order to obtain the same quantity of quicklime, the final product. As a result, the production facility has improved significantly and the amount of waste rock to be hauled and dumped has also halved.

The greater yield through the use of sensor-based sorting machines does not only bring more profit, it also preserves the environment through the reduction of emissions and energy consumption. This is an excellent way to treat our Earth responsibly in the face of limited supplies of raw materials.

More than 220,000 tons of valuable white limestone was extracted from the waste rock dump of a limestone quarry in Finland, thanks to the use of optical sorting technology from CommodasUltrasort. An investment that not only paid for itself, but also allowed the limestone plant to operate profitably again.