Method of recycling fine refractory metal particles until particles grow to the desired size

Claim 1

IN A PROCESS FOR PRODUCING A REFRACTORY METAL SELECTED FROM THE GROUP CONSISTING OF NIOBIUM, TANTALUM, MOLYBDENUM AND TUNGSTEN BY THE VAPOR PHASE REDUCTION OF A CHLORIDE OF SAID METAL AT A REACTION TEMPERATURE OF ABOUT 700 TO 1200*C. WITH A REDUCING GAS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN AND ZINC VAPOR, THE IMPROVEMENT WHICH COMPRISES INTRODUCING SAID REDUCING GAS INTO A REACTION ZONE UPWARDLY FROM AN OPEN END TUBE AT A VELOCITY OF ABOUT 100 TO 200 FEET PER SECOND, SAID REDUCTION GAS BEING DIRECTED TO PASS THROUGH AN INWARDLY TAPERED PATH, MIXING SAID REDUCING GAS WITH A GAS SELECTED FROM THE GROUP CONSISTING OF A REFRACTORY METAL CHLORIDE AND A REFRACTORY METAL CHLORIDE-REDUCING GAS MIXTURE AT A POINT ABOVE THE TERMINATION OF SAID TAPERED PATH, THE METAL CHLORIDE BEING REDUCED TO FORM METAL PARTICLES THAT DROP DOWNWARDLY BELOW SAID REACTION ZONE WHEREBY A LARGE PARTICLE FRACTION OF SUFFICIENT SIZE AND DENSITY DROPS INTO A COLLECTION ZONE AND A FINE PARTICLE FRACTION IS CARRIED BACK INTO THE REACTION ZONE BY SAID REDUCING GAS, THEREBY CONTINUOUSLY CIRCULATING SAID FINE PARTICLES BACK TO THE REACTION ZONE UNTIL SAID PARTICLES ARE OF SUFFICIENT SIZE TO BECOME PART OF THE LARGE PARTICLE FRACTION DROPPING INTO THE COLLECTION ZONE.