Recovery of Tungsten from Ferrotungsten-V

The effect of particle size on the oxidation rate of ferrotungsten was determined using a procedure similar to the method used to evaluate the effect of temperature on the oxidation rate. In this set of experiments, the furnace temperature was maintained at a constant 950° C. and the crucibles were removed at approximately 1 hour intervals. The ferrotungsten was separated into five fractions by sieving through a series of screens. The screens sizes were "big," 1/4 mesh, 10 mesh, and 30 mesh. The "big" screen had diamond shaped opening measuring 5/16 by 7/8 inches. The oxidation curves for the different fractions are given in FIG. 2. The finer fractions (-30 mesh, +30 to -10 mesh, and +10 to -1/4) appear to completely oxidize in about 9.5 hours. The two larger fractions require a much longer time, approximately 23 hours. Accordingly, it is desirable to reduce the particle size of the ferrotungsten to -1/4 mesh in order to minimize the time required to completely oxidize the ferrotungsten.

Two additional sets of experiments were conducted in a laboratory tube furnace to determine the effect of the gas flow rate and oxygen content of the gas on the rate of oxidation. Collectively, both parameters dictate the amount of oxygen present in the furnace atmosphere during oxidation.


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