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Manufacturing Method of Ferromolybdenum from Molybdenite-Summary

An object of the present invention is to provide a manufacturing method of ferromolybdenum capable of reducing an amount of reducing agent by carrying out a direct reduction without carrying out an oxidation process when compared with a metallothermic reduction method of the related art, and in particular, directly using molybdenite with high copper content as a raw material.

The present invention relates to a manufacturing method of ferromolybdenum from molybednite. The manufacturing method directly manufactures the ferromolybdenium without roasting the molybdenite. In this case, in a method of removing the sulfur and impurities such as copper, and a reducing agent, i.e., aluminum metal is added to the molybdenite and reacted at high temperature in a heater.

More specifically, the manufacturing method of the ferromolybdenum according to the present invention includes: a) adding iron and aluminum metal in molybdenite with 0.5 to 10% copper content and mixing them; b) reacting the mixture in a heater at a temperature of 1100 to 2000° C. under an argon gas atmosphere; and c) naturally cooling the mixture at ambient temperature and obtaining reaction products.

At step A, a weight ratio of the mixture obtained by adding the iron and aluminum metal to the molybdenite may have 60 to 70 wt % molybdenite, 15 to 20 wt % iron, and 10 to 20 wt % aluminum metal. If the weight ratio of the mixture exceeds the above-mentioned values, the removal of sulfur and impurities may not be performed smoothly and the copper distribution in a slag layer of aluminum sulfide may be lowered.

Step B may be carried out for 10 to 30 minutes and the temperature of a heater including a direct or indirect heating furnace may be 1400 to 2000° C. If the heater exceeds the above-mentioned temperature, it is difficult to obtain targeted reaction products.

The heater uses an induction heating method, more preferably, an direct heating method due to an induction coil on the outside of a crucible using a high frequency generator, but is not limited thereto.

In this case, the atmosphere in the heater may be an argon gas atmosphere. The argon gas flux at the outside of the heater may be controlled according to the air-tightness degree of the apparatus required and may be sufficiently supplied in order to block the introduction of external air.

The ferromolybdenum having copper content less than 0.5% may be manufactured at the lower portion of the heater by the reaction and the slag layer including aluminum sulfide (Al2S3) as a main component and a small amount of iron sulfide (FeS) is formed at the upper portion thereof.

The reaction formula may be represented by the following Formula 1. 
3MoS2+4Al+xFe→2Al2S3+FexMo3 (1)

In the reaction, the affinity of the copper and the sulfur is large such that the sulfides exist in most of the slag layer and the distribution ratio depends on the redox potential, i.e., the addition of aluminum.

The following Table 1 represents heat of reaction, deviation of Gibb's free energy, and reaction equilibrium constant when the molybdenite and the aluminum metal react at 1100 to 2000° C. As can be appreciated from the equilibrium constant values of Table 1, it can be expected that the concentration of molybdenum in the slag generated is very low in the equilibrium state. However, the heat of reaction is not large, such that the adiabatic reaction temperature is about 1000° C. As a result, heat should be applied from the outside in order to melt the ferromolybdenum and to carry out the phase separation.


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