Effect of Time on Formation of Phases in the Slag during Tin Production




Abstract: Most cassiterite ores contain a certain amount of niobium and tantalum, which report to the slag during tin production. The reduction time is said to enhance the formation of some phases which preferentially dissolve some metals than others. The current paper investigates the effect of time on the phases that form in the slag during reduction and the preferential dissolution of Nobium and Tantalum in some phases. XRD, XRF, SEM-EDS were used to analyse the head sample and the products of the smelting process. The basicity was kept at 1 with the addition of dolomite. Carbon was used as reducing agent and an alumina tube furnace for the reduction. Graphite crucible was used and CO was blown in the furnace to minimise the reaction between the sample and the crucible. Experiments were conducted at different reduction times. The time varied from 30minutes to 2hours with 30 minutes intervals at 1400oC. Results showed that Nobium and Tantalum are preferentially dissolved in Monticellite, Ferrocolumbite, Fayalite, Tantalum oxide and Niobium oxide, the two oxides reaching 5% in the slag while the purity of metal reached a maximum of 99% of Sn and 1% Fe.

Authors: David Ilunga Mutombo, Michel Kalenga Wa Kalenga, and Willie Nheta

Keywords: Cassiterite, Smelting, Reduction time, Nb-Ta

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9 pages


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