GB661976A - Improvements in industrial processes for extracting rhenium - Google Patents

Abstract

<PICT:0661976/III/1> Molybdenite concentrates, obtained by selective flotation of copper-molybdenum sulphide ores, are treated for the extraction of rhenium present by heating in an oxidizing atmosphere at 500-600 DEG C. until all the sulphur has been eliminated, and thereupon heating in the presence of oxygen at above 550 DEG C. but below the temperature of volatization of molybdenum oxide to volatilize rhenium as Re2O7, entrainment of molybdenum oxide in the evolved gases being precluded by fusing together of the oxide particles. Two forms of apparatus are shown. In Fig. 2, the concentrate passes down a multihearth furnace 14, the gases from the upper hearths passing to cyclones 6, 6\sv, 6" to separate molybdenite dust which is returned to the furnace, and the gases from the lower hearths passing to multicyclone(s) 9, cooling air being admitted at 8 although the multicyclone is kept at a sufficiently high temperature, say 250-300 DEG C. so that rhenium oxide cannot condense, an atomizer 10 in which the oxide is dissolved in water or a highly diluted base such as ammonia, and an electrostatic separator 13. Separated material is passed to tank 12, whence, with the solution from atomizer 10, it is circulated to the top of the latter. When a diluted base is employed, its concentration is such as to maintain the pH of the solution at less than 7. Molybdic acid is discharged at 26. In the other apparatus, the concentrate is dried and passed to a rotary kiln, the gases first evolved being treated to separate the molybdenite dust and being thereafter diverted to the rhenium oxide-separation circuit.