Fluidized bed apparatus and process

In an apparatus for contacting a mass of fluidized solids with a gaseous medium and withdrawing heavy solid particles from said mass while maintaining lighter solid particles in said mass wherein the apparatus comprises a fluidizing chamber, a sloping, perforated grate in the lower portion of said fluidizing chamber to support said mass of fluidized solids and having means for passing a gaseous medium through said grate to assist in maintaining said mass in a fluidized state and means for withdrawal of said heavy solid particles, the improvement comprising;

• said grate being sloping and perforated for passage of gas and retention of said solids and having at least one substantially continuous open slot sufficiently wide for passage of said heavy solid particles and in communication with a withdrawal conduit for preferentially removing the heavy solid particles from the fluidizing chamber and returning lighter solid particles to said mass of fluidized solids, said withdrawal conduit having a reduced cross section portion spaced from said grate open slot, and wherein said at least one open slot is:
• (a) an annular shaped opening in said grate and said grate comprises a conical central portion having its apex upward and an inverted truncated conical outer portion, both conical portions symmetrical about a common center line, said annular open slot being located at the intersection of the downwardly sloping conical portions, or (b) at least one straight open slot extending across substantially the entire width of said grate and said grate comprises multiple downwardly sloping portions with said at least one straight open slot located at the intersection of two downwardly sloping portions.