Document Type

Honors Thesis

Publication Date

Spring 5-8-2026

Abstract

San Rafael is currently the only mine producing tin (Sn) in Peru, operating two concentrators. In the first, called the San Rafael plant, tin concentrate is produced through gravity separation circuits consisting of jigs, spirals, and Mozley tables, followed by reverse flotation, where sulfides are floated while cassiterite (78.77% theoretical tin content) is depressed. Material containing tin values is then directed to a desliming circuit, where the pulp density is adjusted prior to sulfide reverse flotation. The tailings from this stage are subsequently processed through another flotation circuit but, in this case, the Sn is floated. Cycloning is applied throughout the different stages of the process. In this plant, overall tin recovery is approximately 93% with 82% coming from gravity concentration and another 11% coming from flotation. This plant has a processing capacity of 3,000 tons per day, with an average head grade of 2.6% Sn. The final concentrate totals 190 MT per day at 41% Sn grade. On the other hand, the second concentrator, called the B2 plant, treats historical tailings with an average head grade of 1.27% Sn, producing a tin concentrate grading approximately 31% Sn at an overall recovery of 71%. The plant operates at a processing capacity of 2,500 metric tons per day and generates about 70 metric tons of tin concentrate daily. Substantial amounts of cassiterite remain in the final stages of the first process plant. After gravity concentration, the material undergoes a reverse flotation process in which sulfides are floated while cassiterite is depressed, followed by a cassiterite flotation stage. The stream then passes through a cyclone, and the cyclone fines are directed to Thickener No. 70, from which the sample being examined was collected. This sample has a P80 of 8 μm, with a head assay of 7.2% Sn and a mineralogical content of 9.2% cassiterite. According to TIMA mineralogical analysis, the degree of liberation for this sample is 43%. For the study, several processing methods were evaluated, including magnetic separation, cyclosizing, electrocoagulation, leaching, agglomeration flotation, traditional flotation, and a combination of Reflux classification/flotation. Tin recovery and grade results are presented as a function of different process parameters for each method. Sample characterization was carried out using XRD and TIMA for mineralogical composition; AA, ICP, CSA, and XRF for elemental assays; zeta potential to determine surface charge, and laser particle size analysis to correlate with TIMA and determine P80. While results are encouraging, the best metallurgical performance was found by cyclosizing, acid leaching siderite and cyclosizing to solid residue to yield tailings that equate to 30.7% recovery and 25.7% Sn grade.

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