ABSTRACT
LDS (formerly Laser Detect Systems, now Laser Distance Spectrometry) earlier constructed and produced an industrial LIBS machine, which enables online measurement of the Mg, Fe, Al, Si, Ca and P2O5 content of phosphate rock on a moving conveyer belt. It allows real time shipping and discarding decisions based on sound analytical data. Two LIBS machines are working in the Florida phosphate industry (Mosaic). While this allows for sorting of phosphate rock after mining pumping and separation, there is an advantage to doing the rock characterization much sooner in the process, not only to eliminate the cost of mining, pumping and separation, but also to reduce the possibility of discarding good rock rather than mining it. This required the construction of a remote LIBS unit capable of identifying rock quality from a distance of up to 25 meters. To prove the feasibility of a remote real-time LIBS analyzer of phosphate rocks that could be used for rock analysis at the mine face, rock in the dragline bucket or rock prior to sluicing it into the pumping pit, LDS constructed and successfully tested in real field conditions a remote LIBS (ReLIBS) unit capable of performing phosphate rock analysis at 5-25 m distances. As a next step, an industrialized unit was constructed and tested, capable of constant functioning in the real-life conditions of an open phosphate mine. This remote LIBS device proved the feasibility of distant real-time chemical analysis of phosphate rocks excavated by dragline machine in that it:
1. Differentiated between overburden, matrix and bottom materials
2. Determined the P2O5 content
3. Determined the MgO and iron content in the matrix samples
4. Initially, the optimum position (considering safety and mechanical feasibility)
of the ReLIBS was determined to be at the washing pit before the matrix is slurried
with water to pump to the beneficiation plant
After successful field testing of the machine, it was determined that a more optimum location would be on the dragline boom, looking down at the contents of the dragline bucket prior to dumping of its contents.
LASER DISTANCE SPECTROMETRY Petach Tikva, Israel and R SQUARED S, INC. Lakeland, FL