Por: Jorge Diaz Panuera y Agustín Lozano Cubas, Minsur.

Abstract

The San Rafael Mining Unit is the main tin producing mine in South America and is considered the third largest producer worldwide; it is located in the eastern Andean mountain range at 4,500 meters above sea level, in the Puno region. The concentrator plant processes 3,200 TPD, the tin recovery is done by gravimetric and flotation processes, the concentrate obtained is sent to its smelter and refinery located in the city of Pisco. Tailings have been disposed of in different storage facilities: B1 and B2; currently they are disposed in B3 and inside the mine as paste backfill.

The B2 tailings storage facility has an average depth of 22 meters, with a minimum of 3 meters and a maximum of 39 meters. The mineralogy is associated with tin ore formation, which is predominantly quartz, as well as minor amounts of other silicate minerals. The dominant tin mineral is cassiterite; other associated minerals include iron oxides and sulfides of iron, copper, and zinc.

The tin mineral resource estimate for the B2 storage facility is based on information from drilling campaigns and studies conducted by Amec Foster Wheeler in 2004 and Hatch in 2013.

The mining plan considers potentially mineable resources amounting to 7.6 Mt of measured and indicated material, with an average grade of 1.03 % Sn to feed the concentrator plant.

To define the tin recovery process, a series of laboratory tests were carried out with different equipment and configurations of gravimetric concentration and flotation. Three phases of pilot plant tests were carried out: tests to confirm the process, optimization tests, and variability tests. The overall results obtained were 66 % recovery: 44 % in gravimetric concentration and 22 % in flotation. The metallurgical tests carried out in the pilot plant allowed obtaining the necessary information to carry out the scaling up for the industrial plant.

Smelter recovery was determined from tests with concentrate produced in the pilot plant and synthetic concentrate.