Quarry Southern Africa November 2018 - Page 20

WINNING QUARTZITE QUARRY SHINES ENVIRONMENTALLY By Eamonn Ryan NPC Sterkspruit Aggregates is a combination quartzite aggregate quarry and adjacent ready-mix concrete batch plant, operating as a subsidiary of Natal Portland Cement Company in the Outer West area in Durban. Its tough quartzite has an especially high silica content. A vin Mandass, quarry manager at NPC Sterkspruit Aggregate, explains that the quartzite aggregate mined at the Sterkspruit Aggregate quarry – with its high silica content – is an abrasive, hard material which is only slightly less hard than other quarry materials such as granite. “It breaks easier but it’s very high wearing – so the all the machinery and equipment has to be exceptionally hardy.” For dust suppression, Sterkspruit uses a water tanker at the quarry and has water sprays at different points in the plant. “The process uses a lot of water and given the drought that KwaZulu-Natal has recently been through we try and minimise our water consumption as much as possible. In 20_QUARRY SA| NOVEMBER/DECEMBER 2018 the quarry itself we’ve created a sump which we use to supply the water tanker. For the crushing plant we draw water from the river. We are in the process of getting our water use licenced. In 2010 we upgraded our wash plant and one of the main criteria upon which we based our final decision was that it be able to recycle the water,” says Mandass. “As a result, the quarry recycles about 80% of the water it uses in its washing process. We currently average 4 000m3 a month. If it wasn’t for the recycling this would exceed 10 000m3 a month.” The standard practice at Sterkspruit is that if there’s an issue with the plant, then the plant is immediately shut down so that it never runs empty for more than about 10 minutes. “We save electricity as far as possible by, for instance, making sure that the crushers are always running at capacity. We monitor and benchmark our electricity usage against our sister quarries in South Africa and elsewhere in the world, so that if any of them are controlling their electricity consumption better than us then we can learn from and follow their example,” says Mandass. Blasting process to extract rock material The quarrying process is divided into different phases: drilling and blasting; load and haul; crushing and stockpiling. “We drill and blast by cleaning off the bench and removing as much of the loose