Apparatus for pelletizing powdered solid substance in a fluidized bed

Claim 1

Apparatus for pelletizing a powdery solid substance by causing agglomeration to produce pellets of a predetermined minimum size, the combination of, a fluidizing vessel enclosing a fluidizing zone comprising side walls surrounding the periphery of said zone and a bottom wall structure defining the bottom of said zone, said vessel having a bottom pellet-discharge opening and said bottom wall structure extending downwardly toward said opening from said side walls at an acute angle to the horizontal, said bottom wall structure having gas-discharge openings for fluidizing gas, means to supply fluidizing gas through said gas discharge openings, means providing a vertical passageway extending upwardly to and concentric with said pellet-discharge opening, means directing a stream of fluidizing gas upwardly through said passageway at a controlled rate, means for delivering the powdery solid substance at a controlled rate into said vessel, means to deliver an agglomerating liquid to a zone within said vessel remote from said side walls and bottom wall structure, said stream of fluidizing gas being effective to produce an upward flow of gas from said pellet discharge opening and said first-mentioned fluidizing gas cooperating therewith to produce and maintain a fluidizing gas pattern throughout said fluidizing zone with the flow being upwardly from said pelletdischarge opening and thence horizontally to the upper portion of said side wall structure and thence downwardly past said side wall structure and thence along said bottom wall structure generally toward said pellet-discharge opening to complete the path, whereby the powdery solid substance and said liquid are entrained into said fluidizing gas and the liquid wets and agglomerates the powdery solid substance to form pellets the size of which is increased by surface wetting and contact with additional fragments of the solid substance, said stream of fluidizing gas flowing upwardly through said passageway at a controlled rate such that pellets which are smaller than said minimum size are carried upwardly into said fluidized zone and pellets of said minimum size are discharged through said passageway by the action of gravity.