Winning
The mine comprises three pits : A- , B- , and C-pit . Operations started at A-pit in the 1950s . 2010 .
aggregate . Traditionally an Iscor operation , the focus has predominantly been on metallurgical supply to the steel producers . However , over the past couple of years , the focus has shifted to the aggregate market , says Hattingh . “ There is a focus on growing the aggregate market for ready-mix and concrete blocks , among others .”
The nature of the reserve is interesting . One could almost draw a straight line down the middle of the three pits , with all the metallurgical material on the western side of the pit and all the aggregate material to the eastern side .
The most significant difference between metallurgical and aggregate product is the silica content . In metallurgical applications , the requirement is 3 % or less . If the silica material exceeds 3 %, it is classified as aggregate .
Currently the metallurgical products produce a silica content average of 1 – 1.5 %.
“ The focus for us is to continue metallurgical products , but then push the aggregate market to grow ,” says Hattingh .
The mining and the processing of the two products are the same and it is almost impossible to differentiate between the products with the naked eye . “ When we drill in areas that we suspect have low silica content , we take the drill chippings to the lab , have it sampled , and confirm the quality . Therefore , we know if it ’ s metallurgical or aggregate product before we blast . Some of our people have also worked in the quarry for years , and thus have experience in the geology .”
The plant produces approximately 1.5 – 1.6 million tonnes of product per year and moves another 250 000 – 300 000 tonnes of overburden . Additionally , it moves 100 000 tonnes of washed slimes material , bringing the total tonnages of material moved at Glen
Douglas mine to approximately two million tonnes per year .
Unique rail set-up
The plant comprises a primary circuit with a big Allis Chalmers gyratory crusher . The capacity of the plant is in excess of 1 000 tonnes per hour , but the operation is not currently running at full capacity .
The secondary plant consists of a washing plant with two Kawasaki cone crushers running at a capacity of 500 tonnes per hour . “ We are only running two shifts on the primary , secondary , and tertiary crushers , so there is additional shift hours available ,” says Hattingh .
The feed from the secondary plant would go to either the aggregate stockpile or the metallurgical stockpile . The tertiary plant splits the metallurgical and aggregate product with a kidney conveyor .
The plant produces approximately 1.5 – 1.6 million tonnes of product per year and moves another 250 000 – 300 000 tonnes of overburden .
QUARRY SA | march 2017 _ 21