Process and furnace for the continuous production of aluminum nitride

Claim 1

PROCESS FOR THE CONTINUOUS PRODUCTION OF ALUMINUM NITRIDE COMPRISING THE FOLLOWING STEPS: FORMING PARTICULATE MATERIAL COMPOSED OF ALUMINUM OXIDE, CARBON AND A CALCIUM ALUMINATE BINDER; CONTINUOUSLY PASSING THE PARTICULATE MATERIAL DOWNWARD BY GRAVITY INTO AN ELONGATED, EXTERNALLY HEATED REACTION ZONE WHEREIN THE PARTICULATE MATERIAL IS HEATED UNIFORMLY TO A TEMPERATURE NOT IN EXCESS OF ABOUT 1750*C.; CONTINUOUSLY PASSING A CURRENT OF NITROGEN UPWARDS IN SAID ZONE COUNTERCURRENT TO THE DESCENDING HEATED PARTICULATE MATERIAL AND THEREBY FORMING ALUMINUM NITRIDE; CONTINUOUSLY REMOVING AND RECOVERING THE FORMED ALUMINUM NITRIDE AT A POINT BELOW THE LOWER END OF SAID REACTION ZONE; PASSING REACTION GASES FROM THE UPPER END OF THE REACTION ZONE THROUGH AN EXPANSION ZONE MAINTAINED AT TEMPERATURE CONDITIONS WHEREIN ANY CALCIUM CONTAINED IN SAID REACTION GASES WILL BE CONDENSED AND DEPOSITED; REMOVING THE CONDENSED DEPOSIT FROM SAID EXPANSION ZONE, AND CONTINUOUSLY REMOVING GASES FROM THE TOP OF THE EXPANSION ZONE.