Extruding attrition resistant alumina particles

Claim 1

THE METHOD OF PREPARING ATTRITION RESISTANT ALUMINA PARTICLES HAVING MINIMUM DIMENSIONS WITHIN THE RANGE OF FROM ABOUT 2 TO 13 MM., WHICH INCLUDES THE STEPS OF IMPREGNATING AN ALUMINA TRIHYDRATE POWDER WITH AN AQUEOUS SOLUTION CONTAINING NITRIC ACID, THERE BEING FROM ABOUT 5 TO ABOUT 9 POUNDS OF 100% NITRIC ACID PER 100 POUNDS OF IMPREGNATED POWDER, SAID IMPREGNATED POWDER HAVING POWDERY CHARACTERISTICS BY REASON OF ITS LOW WATER CONTENT, CAUSING THE NITRIC ACID TO REACT WITH THE ALUMINA FOR MORE THAN ONE HOUR TO FORM ALUMINUM NITRATE AS A MINOR COMPONENT DISTRIBUTED THROUGHOUT THE POWDERY IMPREGNATED ALUMINA TRIHYDRATE; SUBJECTING SAID IMPREGNATED AND REACTED POWDER TO MECHANICAL PRESSURE, MIXING AND EXTRUDING TO FORM PARTICLES SUFFICIENTLY COHESIVE TO TO HANDLED; QUICKLY SUBJECTING SAID PARTICLES TO A CHAMBER MAINTAINED BELOW 300*F. AND ABOVE 220*F. FOR FROM 10 TO 60 MINUTES FOR RAPID DRYING UNDER LOW HUMIDITY CONDITIONS, A DRY AUXILIARY GAS STREAM BEING PASSED THROUGH THE PARTICLES AT A SPACE VELOCITY GREATER THAN 10 V./V./HR.; SUBJECTING THE THUS DRIED PARTICLES TO A TEMPERATURE INCREASING TO ABOUT 800*F. AT A CONTROLLED SLOW RATE OF. TEMPERATURE INCREASE FOR SEVERAL HOURS IN THE PRESENCE OF MORE THAN 50% STEAM, THE STEAM BEING WITHDRAWN BY A STREAM OF AUXILIARY GAS AT A LOW SPACE RATE, WHEREBY A PORTION OF THE HYDRATE WATER IS REMOVED FROM THE PARTICLES, AND WHEREBY THE PARTICLES DEVELOP GAMMA-ALUMINA CHARACTERISTICS, AND WITHDRAWING PARTICLES OF ATTRITION RESISTANT GAMMA-ALUMINA PARTICLES HAVING MINIMUM DIMENSIONS WITHIN THE RANGE OF FROM ABOUT 2 TO 13 MM.

Claim 2

THE METHOD OF PREPARING ATTRITION RESISTANT ALUMINA PARTICLES HAVING MINIMUM DIMENSIONS WITHIN THE RANGE OF FROM ABOUT 2 TO 13 MM., WHICH INCLUDES THE STEPS OF IMPREGNATING AN ALUMINA TRIHYDRATE POWDER WITH AN AQUEOUS SOLUTION CONTAINING NITRIC ACID, THERE BEING FROM ABOUT 5 TO ABOUT 9 POUNDS OF 100% NITRIC ACID PER 100 POUNDS OF IMPREGNATED POWDER, SAID IMPREGNATED POWDER HAVING POWDERY CHARACTERISTICS BY REASON OF ITS LOW WATER CONTENT, CAUSING THE NITRIC ACID TO REACT WITH THE ALUMINA FOR MORE THAN ONE HOUR TO FORM ALUMINUM NITRATE AS A MINOR COMPONENT DISTRIBUTED THROUGHOUT THE POWDERY IMPREGNATED ALUMINA TRIHYDRATE; SUBJECTING SAID IMPREGNATED AND REACTED POWDER TO MECHANICAL PRESSURE, MIXING AND EXTRUDING TO FORM PARTICLES SUFFICIENTLY COHESIVE TO TO HANDLED; QUICKLY SUBJECTING SAID PARTICLES TO A CHAMBER MAINTAINED BELOW 300*F. AND ABOVE 220*F. FOR FROM 10 TO 60 MINUTES FOR RAPID DRYING UNDER LOW HUMIDITY CONDITIONS, A DRY AUXILIARY GAS STREAM BEING PASSED THROUGH THE PARTICLES AT A SPACE VELOCITY GREATER THAN 10 V./V./HR.; SUBJECTING THE THUS DRIED PARTICLES TO A TEMPERATURE INCREASING TO ABOUT 800*F. AT A CONTROLLED SLOW RATE OF. TEMPERATURE INCREASE FOR SEVERAL HOURS IN THE PRESENCE OF MORE THAN 50% STEAM, THE STEAM BEING WITHDRAWN BY A STREAM OF AUXILIARY GAS AT A LOW SPACE RATE, WHEREBY A PORTION OF THE HYDRATE WATER IS REMOVED FROM THE PARTICLES, AND WHEREBY THE PARTICLES DEVELOP GAMMA-ALUMINA CHARACTERISTICS, AND WITHDRAWING PARTICLES OF ATTRITION RESISTANT GAMMA-ALUMINA PARTICLES HAVING MINIMUM DIMENSIONS WITHIN THE RANGE OF FROM ABOUT 2 TO 13 MM.