REDUCTION OF TUNGSTEN HALIDES- 2

Chlorination of scheelite or wolframite ore concentrates according to the equations

2CaWO₄ + 3C + 6C₁₂→2CaCI₂ +2WOC₁₄ + 3CO₂

2FeWO₄ + 3C+ 7C₁₇→2FeC_I3 +2WOC₁₄ + 3CO₂

and subsequent treatment of the chlorides offers a selective separation of most other chlorides formed with the exception of molybdenum but bears certain disadvantages: 

*It mainly yields in the formation of WOC₁₄ and not in the desired WC₁₆.

*Therefore, an additional conversion step from WOC14 to WC₁₆ is necessary; the separation from other chlorides can be done only in the WCI₆ stage by fractional distillation.

*Calcium as well as iron or manganese form molten chlorides at the reaction temperature causing difficulties in reactor design.

*Finally, hazards associated with HCI, C1₂, COCI₂, and chlorides as well as environmental considerations are further limiting factors.

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