Method of producing fine tungsten powder from tungsten oxides

摘要

The present invention relates to an improvement in the method and the apparatus for reducing tungsten oxide powder to tungsten metal powder. The method produces more uniform particle size distribution by decreasing the variability of temperature and inconsistency of reductant gas flow during the reduction process. The method includes the steps of: providing powder particles of WOx in a unique reaction boat with a low aspect ratio to a multi-tube furnace; (a) contacting particles of WOx, wherein x is at least 2.5, with hydrogen and water vapor under fluid bed conditions at a temperature in the range of about 600 degrees to about 1000 degree Centigrade and at a water partial pressure equal to or greater than the equilibrium partial pressure, whereby said particles of WOx are reduced essentially to particles of WO2 with substantially no formation of tungsten metal, and (b) reducing the partial pressure of water in the fluid bed to a level sufficient to achieve reduction of said particles of WO2 to tungsten metal while continuing to maintain said bed at a temperature which is substantially equal to or higher than said first temperature but not over about 1000 degree Centigrade.