Elutriation system

Claim 1

IN A PROCESS WHEREIN A BODY OF GRANULAR MATERIAL HAVING AN AVERAGE PARTICLE SIZE IN THE RANGE OF ABOUT 4 TO 10 MESH IS CONTINUOUSLY CIRCULATED UNDER CONDITIONS CONDUCTIVE TO ATTRITION OF THE SOLID PARTICLES RESULTING IN THE PRODUCTION OF FINES, THE METHOD OF REMOVING SAID FINES FROM SAID BODY WHICH COMPRISES THE STEPS OF: INTRODUCING A COMPACT MOVING STREAM OF SAID GRANULAR MATERIAL AT AN INTERMEDIATE LEVEL WITHIN A CONFINED ELUTRIATING ZONE; WITHDRAWIGN GRANULAR MATERIAL FROM THE BOTTOM OF SAID ZONE AT A RATE ADAPTED TO MAINTAIN SAID GRANULAR MATERIAL WITHIN SAID ZONE AS A COMPACT, NON-TURBULENT GRAVITATING BED RECEIVING SAID STREAM OF GRANULAR MATERIAL DIRECTLY UPON A PORTION OF ITS SURFACE; FLOWING THE TOP PORTION OF SAID BED LATERALLY DOWNWARD FROM THE ZONE OF SOLIDS INTRODUCTION AS A SUPPORTED SHALLOW LAYER OF UNIFORM DEPTH; PASSING GAS UPWARDLY THROUGHOUT SAID MOVING LAYER AT A VELOCITY SUFFICIENT TO SUSPEND AND CARRY UPWARDLY THROUGH THE COMPACT REMAINING PORTION OF SAID LAYER ONLY SAID FINES; AND DISCHARGING THE SUSPENSION OF GAS AND FINES FROM THE REGION OF SAID ELUTRIATING ZONE ABOVE SAID MOVING LAYER, THE RATE OF FLOW OF SAID SUPPORTED LAYER BEING CONTROLLED BY THE RATE OF SAID WITHDRAWAL OF GRANULAR MATERIAL FROM THE BOTTOM OF SAID ELUTRIATING ZONE.