Environmentally Safe Fluoride Cycle in Tungsten Technology. Substantiation of the Production Cycle with Fluorine and Hydrogen Recycle

A fluoride cycle in tungsten technology is based on three processes: (i) electrochemical decomposition of HF in the KHF2 + HF melt at 80-100 degrees C with the separate evolution of gaseous fluorine and hydrogen; (ii) fluorination of the tungsten powder with evoluated fluorine at 300-350 degrees C with the condensation of formed WF6 in a liquid form at t = 2.5-3.0 degrees C, and (iii) reduction of gaseous WF6 with evoluated hydrogen at t = 580-600 degrees C with the condensation of formed HF at + 1 degrees C and its use for the fluorine and hydrogen production, thereby ensuring their recycling in the cycle. The optimization of mentioned processes resulted in hardware-process implementations providing the formation of a large-scale plane and cylindrical billets in the industrial scale for deformation, as well as pipes, crucibles, and other products of various sizes made of tungsten with productivity of one process line of similar to 4.3 kg/h (> 34 t/yr) with the fulfillment of environmental requirements. In contrast with the methods of powder metallurgy, the described technology ensures the formation of dense half-finished products and products made of pure tungsten with finer grain structures and almost unlimited sizes. Herewith, the specific power consumption for 1 kg of production lowers by a factor of 2.0-2.5. To increase the production efficiency, the simultaneous operation of four process lines in an automated mode is recommended.