product news
57
07.13
Hurricane air cannons solve
blockage problem at Phola
A high-volume coal handling operation in South Africa has solved
material build-up problems in the transfer chute feeding its export
silo and discard bin with a strategically-timed series of air cannons
that blast the accumulation from chute and vessel walls, preventing
bottlenecks and maintaining throughput rates.
A 50:50 joint venture between Anglo American Inyosi Coal (AAIC)
and BHP Billiton Energy Coal South Africa (BECSA), the Phola coal
processing plant – where the cannons have been installed – is fed
equally by AAIC’s Zibulo colliery and BECSA’s Klipspruit mine. The
twin-module coal washing operation delivers a throughput of nearly
1 200 t/h from each module.
Like many newer facilities, the plant does not maintain its fines
in a wet slurry for environmental reasons, instead filtering the dry
fugitive particles and pressing them into cakes.
Soon after the plant went online, the process began delivering
a throughput of more than a million tonnes per month, well on the
way to its target of 16 million annually. On its busiest day of that first
year, the facility completely loaded eight 100-car trains, each car
with a capacity of 84 t.
But as the high-volume operation ramped up, engineers started
noticing bottlenecks. They traced the slowdown to material build-
up in the chute feeding the export silo and discard bin. Operators
determined that the freshly-pressed cakes were sticking to the
walls of the chute, narrowing the space for product transfer and
leaving ‘rat holes’ which restricted flow. As the blockage grew, it
would cause the vessels to fill with material and eventually trip the
high level indicator, shutting off the conveyors and forcing down-
time for manual cleanout.
Phola immediately began researching possible solutions. Opera-
tors met with representatives from Martin Engineering South Africa,
who recommended using 70-litre Hurricane air cannons, placed in
strategic locations, to knock down the filter cake within the chute.
Positioning of the cannons and nozzles is critical to their success,
and the technicians installed the four units at a 35 deg downward-
facing angle for maximum effectiveness in this application.
The patented design is engineered to enhance material flow with
greater force and faster cycling than traditional valve designs. The
cannons fire only when the exhaust valve opens in response to a
positive surge of air sent by a solenoid or PLC control. This positive-
acting valve amplifies the discharge, providing up to 50 % more
force than a standard air cannon of the same size. In addition, the
improved air path fills the reservoir three to four times faster than
typical designs.
With production rates continuing to rise, Phola has commissioned
another series of cannons to further improve the material flow inside
the discard bin. The company is currently awaiting installation of a
larger air compressor to manage the additional load.
Martin Engineering SA, tel (+27 13) 656-5135
To address the blockage issue, Martin Engineering recommended 70-litre air
cannons, strategically placed to knock down the filter cake within the chute.
