Fluidized bed classifier

Claim 1

A PROCESS FOR SEPARATING A MASS OF PARTICULTE SOLIDS OF MIXED SIZES INTO A FIRST FRACTION CONSISTING ESSENTIALLY OF PARTICLES SMALLER THAN A PRESELECTED SIZE OF SEPARATION AND A SECOND FRACTION CONSISTING ESSENTIALLY OF PARTICLES LARGER THAN SAID PRESELECTED SIZE TO SEPARATION, WHICH COMPRISES ESTABLISHING A FLUIDIZED BED OF PARTICLES FROM SAID MASS OF PARTICULATE SOLIDS WITH A FLUIDIZING GAS RISING THROUGH THE BED MAINTAINED AT A SHALLOW DEPTH RELATIVE TO A SUBSTANTIAL HEIGHT OF A FREEBOARD ZONE ABOVE IT, CONTROLLING THE RATE OF GAS FLOW THROUGH THE BED SO THAT THE GAS VELOCITY IN GREAT ENOUGH TO PROJECT FROM SAID BED INTO THE FREEBOARD ZINE PARTICLES OF AN INTERMEDIATE SIZE SIGNIFICANTLY LARTER THAN SAID PRESELECTED SIZE OF SEPARATION, MAINTAINING IN THE FREEBOARD ZONE A RELATIVELY LOWER UPWARD GAS VELOCITY SUFFICIENT ONLY FOR SUSTAINING AND CARRYING AWAY PARTICLES SUBSTANTIALLY NOT GREATER THAN SAID SIZE OF SEPARATION WHILE SAID PROJECTED LARGER INTERMEDIATE SIZE PARTICLES LOSING THEIR MOMENTUM IN THE UPPER PORTION OF SAID FREEBOARD ZONE FALL BACK INTO THE FLUIDIZED BED THROUGH AN INTERMEDIATE ZONE CONSTITUTING THE TRANSITION BETWEEN THE FREEBOARD ZONE AND THE RELATIVELY CONSTRICTED FLUIDIZED BED, WITH INTERMEDIATE SIZE PARTICLES RETURNING TO THE BED; CONTINUOUSLY SUPPLYING SAID PARTICULATE SOLIDS TO SAID FLUIDIZED BED, CONTINUOUSLY REMOVING FROM SAID FREEBOARD ZONE THE PARTICLES COMPRISING THE FIRST FRACTION SUSPENDED IN THE FLUIDIZING GAS, CONTINUOUSLY REMOVING FROM SAID FLUIDIZED BED THE PARTICLES COMPRISING SAID SECOND FRACTION INCLUDING SAID PROJECTED AND RETURNED INTERMEDIATE PARTICLE SIZE, AND CONTROLLING THE EFFECTIVE TOP LEVEL OF SAID BED IN THE FLUIDIZED STATE SO AS TO MAINTAIN SAID LEVEL AT AN ELEVATION SUBSTANTIALLY CONSTANT AT THE INTERFACE BETWEEN SAID BED AND SAID INTERMEDIATE ZONE.