B. Sirin et al., THE EFFECT OF SULFUR ON TUNGSTEN RECOVERY FROM SCHEELITE CONCENTRATESBY ALKALI FUSION, Canadian metallurgical quarterly, 33(4), 1994, pp. 313-318
A low-grade scheelite concentrate, obtained from Uludag Tungsten Plant
(Bursa, Turkey), was used in this study. It contained approximately 3
5% WO3, 5.2% S and 27% Fe. The optimum conditions of alkali fusion wer
e: a temperature of 900-degrees-C, twice the stoichiometrically requir
ed Na2CO3, and 1 h treatment time. Tungsten was dissolved with a maxim
um efficiency at the end of 1 of leaching with water at a solid/liquid
weight ratio of 1/5 at 80-degrees-C under continuous stirring. A diss
olution efficiency of 97% was obtained when the sulphur content of sch
eelite concentrate was decreased to 0.7% by roasting in a rotary furna
ce operating at 750-degrees-C and with 100% excess amount of air, whil
e only 78% of tungsten dissolution efficiency could be reached when th
e original scheelite concentrate was not roasted prior to the alkali f
usion. Phase analyses showed that the sulphur in concentrate has forme
d a matte phase as Na3FeS3 and confined some part of the tungsten as C
aWO4, during the alkali fusion, and decreased its dissolution efficien
cy.