Numerical simulation research that modelled the behaviour of particles on a conventional banana screen has been leveraged to make fundamental improvements to Kwatani’s design.
Kwatani said that its adaptations were so important that it was able to double the throughput of a competitor’s problematic dewatering screen on a customer’s mine, where excessive water carry-over was limiting production potential.
According to Kenny Mayhew-Ridgers, chief operating officer at Kwatani, the company’s depth of mechanical and metallurgical expertise underpins its ability to apply what it learns from research and field testing.
“This specific research, which was done by Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO) and the University of Queensland, highlighted that the traditional feed-end slopes of banana screens were generally too steep,” said Mayhew-Ridgers. “At around 34 degrees, these slopes create material velocity in excess of 3 m/s – too high for efficient screening.”
Mayhew-Ridgers considers that a more suitable slope at the feed-end is 25 degrees, leading into five or six deck slopes in the screen and ending with a discharge slope of just 5 degrees or even 0 degrees. This would ensure that the material velocity was less than 0.5 m/s at the discharge end. The drive angle, operating speed and stroke are also significant factors, he said.
“Our analysis allowed us to address a challenge that a customer was experiencing with their de-grit screens,” he said. “Water carry-over from the screen to the conveyor belt was limiting throughput to only 250 tph, and the mine needed more than that.”
Kwatani’s changed the screen feed-end slopes and incorporated a long discharge-end decline slope of 3 degrees. The drive angle was also increased to 50 degrees to improve the dewatering performance of the screen. These adaptations were possible within the constraints of existing chute work, motor base position and support structure.
The size of the screen – measuring 3,66m wide – meant that a considerable load needed to be supported on the screen deck, so circular hollow sections provided improved strength in place of the H-profile deck beams usually employed.
“The modifications were successful,” said Mayhew-Ridgers. “The mine’s plant manager was able to confirm that the feed rate had been increased to 500 tph with very little water carry-over, and this performance was consistently maintained.”
The application of the new design was outlined in a peer-reviewed paper by Mayhew-Ridgers and Kwatani director Derrick Alston, which was presented at an international mineral processing conference.