Laser-induced fluorescence is an optical method whereby high-energy lasers induce characteristic fluorescence in diverse minerals, and where fast optoelectronics read the fluorescent signals, with computers evaluating the information.
“The LIF system was developed specifically for mines with high-bulk production, where the emphasis is on rock identification to control dilution by waste-rock,” says LIF executive Dr Heribert Broicher.
The design of the LIF-analyser includes the application of remote sensing techniques, such as optical systems for irradiation and observation of the material surface, which operates over variable distances. “The analysers operate in a noncontact and real-time mode, with individual measurement taking only microseconds. “In addition, measuring frequency can be designed from low levels up to 20 Hz and more, if necessary,” says Broicher. He adds that the data is evaluated and compared to quality standards set by the mines, whereupon immediate decisions can be made on where to direct the material.
The analysers can be installed above belt conveyors, or be suspended from high structures, where they look down onto the load. “When installed above belt-conveyors, the information provided by the device may be used for simple quality-control and recording, improving downstream processing by controlling the amount of reagents for floatation, sorting by controlling a diverter at the end of the conveyor, as well as blending, by controlling the speed of the conveyor.
“The LIF-analyser for optical sampling of vehicle-loads can provide the driver with information on where to drive and tip the ore within a split-second,” says Broicher. He concludes that the system can add substantially to a mine’s operating cost, while simultaneously enhancing productivity.
LIF is a special form of photoluminescence, which is defined as the emission of visible light during and after excitation with ultraviolet light.