Production of molybdic trioxide by high-temperature oxidation of molybdenite in a cyclone reactor

Abstract

A process to obtain high-purity molydic oxide by oxidizing molybdenite concentrates in a cyclone reactor is being developed. Dry molybdenite concentrate and oxygen are fed continuously into a cyclonic reactor where a fast oxidation takes place at 1200–1600°C, a temperature at which gaseous MoO₃ is directly formed. The off gases, containing SO₂, oxygen and gaseous MoO₃, are quenched with cool air to 500–550°C to condense the molybdic oxide, which is then recovered in high temperature filters. The gases are further washed in a venturi scrubber to recover the rhenium volatilized during the oxidation of molybdenite.

Impurities, such as copper and iron are collected in the lower section of the reactor in the form of a slag, which contains molybdenum as copper and iron molybdates. This slag is treated separately to recover the molybdenum.

The molybdic oxides produced, as a fine dust with particle size less than 5 microns, contain from 98 up to 99.5% MoO₃.