|Non-Contacting Flow Solution
for Heap Leach Mining
How do you measure the flow rate
of a highly corrosive
solution in a partially full pipe?
|The Process||In the heap leaching process, crushed sulfide ore is heaped onto lined leach pads where an acidic solution is sprinkled onto the ore. It percolates down through the heap until it reaches the liner at the bottom. The leach solution containing the dissolved metal flows out of the heap through partially full pipes (16” to 42” HDPE pipes) at velocity rates between 1-3 m/sec. Monitoring flow in the collection pipes contributes to better control of the process, increased mineral recovery and reduced leach cycles.|
Shut down of the leaching process was not an option for Minera
Escondida. So the flow meter had to be designed so that it could be
installed with continuous flow in the partially filled pipes. It
also had to be noncontacting so that it would not be affected by the
highly corrosive acidic solution. Francisco Southernland, Senior
Engineer at Minera Escondida, turned to VSI Ltda of Chile, the
representative for Greyline Instruments, for a solution to monitor
flow in this difficult application.
Greyline AVFM 5.0 Area-Velocity Flow Meter with
Non-contacting Ultrasonic Level and Clamp-on Velocity Sensors
VSI and Greyline Engineer Jose Castro configured Greyline's AVFM 5.0
Area-Velocity Flow Meter with a combination of two nonintrusive
sensors: a clamp-on Doppler velocity sensor to monitor the flow
velocity, plus a down-looking ultrasonic level sensor to measure
level. Both sensors work from the outside of the pipe so there is no
obstruction to flow and no contact with the fluid. Stand pipes were
added to the pipes so that the non-contacting ultrasonic level
sensors were elevated above the flowing solution. By measuring
velocity and level of the flowing solution, and knowing the pipe
diameter, the Greyline AVFM 5.0 Area-Velocity Flow Meter is able to
accurately monitor the flow rate. The flow meter displays, totalizes
and transmits the flow rate in real time to the mine's control
The first Greyline meters were installed in January 2013 and since then 44 AVFM 5.0 Area-Velocity Flow Meters have been deployed in the project. Engineers at Minera Escondida now have a better understanding and greater control of mass balance, evaporation and other physical mechanisms controlling this complex process which will increase the amount of copper recovered and reduce the time of leach cycles. Greyline's AVFM 5.0 with a combination of two nonintrusive sensors: a clamp-on Doppler velocity sensor plus a down-looking ultrasonic level sensor has proved to be a unique, safe and effective solution.
AVFM 5.0 Area-Velocity Flow Monitor
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