Performance analysis of optical and X-Ray transmitter sensors for limestone classification in the South of Brazil

The present study aims to evaluate the use of sensor-basedin the classification of marble ore. These dolomite marbles are quite particular due toa series of felsic and mafic intrusions and syngenetic metapelitic intercalation. In the present study, all the variants of ore and sterile that exists in the deposit were quantified using 3D mapping of mine’s surface. Three particles sizes were tested with the sorting equipment in the laboratory: −25 + 9.5 mm, −50 + 25 mm, and −70 + 50 mm. We use indices of recovery, in terms of Calcium Carbonate Equivalent and mass balance, but also performance indices as accuracy, sensitivity, and specificity for interpretation. Recovery values were between 35 and 85% in the lowest sieve range and between 91 and 98% in the larger range in the sorting tests withan optical sensor. Accuracy is between 43 and 85% in the lowest range and 97 and 98% in the largest. Same results occurred with the sensitivity and specificity, which had better separations while increasing the particle size. It was concluded that the X-ray sensor did not perform well and was considered not applicable to the case under analysis. The optical sensor was shown to be applicable in all tested situations, with recoveries between 35% and 98%, depending on the condition and particle size of the feed. The grain size was the primary factor influencing the separation performance, implying variations of up to 30% in the accuracy indexes.