Fluidized-bed calciner with combustion nozzle and shroud

In a fluidized-bed calciner for the processing of liquids containing solidifiable material to form dry solid particles, wherein said calciner comprises a vessel having walls defining an internal chamber, fluidizable solid particles within said chamber, means for passing an upward gas flow through said vessel to fluidize said solid particles, and nozzle means for injecting a fuel mixture for combustion into said internal chamber of said vessel, said nozzle means includes a first conduit for passing liquid fuel terminating with a venturi section towards said internal chamber of said vessel, said venturi section having a generally central constricted portion, a second conduit generally coaxially disposed about said first conduit to define an annulus for passing an oxygen-containing gas, said second conduit terminating around said venturi section and said venturi section including radial passageways at the constricted portion thereof whereby oxygen-containing gas from said second conduit is caused to flow into and atomize said liquid fuel, the improvement comprising an elongated, tubular shroud with one open end, disposed generally coaxially about said nozzle means, said nozzle means terminating at a location about flush with said vessel walls and said tubular shroud extending beyond the end of said nozzle means at said open end into said internal chamber to provide an antechamber within said shroud end portion between said open end and said nozzle means for the combustion of said fuel, said antechamber having a length-to-diameter ratio of about 2:1 to 5:1 extending into said internal chamber and supply means communicating with said shroud for supplying an oxygen-rich gas with a higher oxygen concentration than air to said antechamber.