Abstract: Solid materials are efficiently calcined in a single column kiln by effecting said calcination through a plurality of vertically arranged zones, by means of a method comprising the steps of feeding said solid materials to a preheating zone wherein the materials are preheated countercurrently with combustion gases, allowing said preheated materials to fall to an air preheating zone to which primary air is fed in parallel flow with said falling preheated materials, allowing said materials to fall to a calcining zone to which fuel is admitted in parallel flow with said preheated air, allowing the thus calcined materials to fall to a cooling zone to which secondary cold air is fed countercurrently with said falling materials, exhausting the combustion gases produced in the calcining zone together with said secondary air which was preheated by the calcined materials, at a point between said calcining and cooling zones, and feeding said combustion gases and secondary air as a mixture to the preheating zone.

Abstract: A burning cell for solid waste fuel materials comprises a lower cylindrical chamber where a pile of said waste fuel is burned with the aid of a plurality of horizontal arrays of tuyeres that feed the air against said pile, and an upper cylindrical chamber separated from said lower chamber by a centrally opened partition, said upper chamber having a helical array of downwardly inwardly and sidewardly inclined tuyeres to produce an outer descending whirlpool of air which reverses direction at said partition to form a central ascending whirlpool of air, said upper chamber having a centrally opened roof for exhausting said air, whereby the large particle fuel is totally burned in said pile in the lower chamber, whereas the partially burned fines are entrained by the air from said lower chamber tuyeres and passed upwardly into the central ascending whirlpool through said upper chamber to furtherly burn said fines without any contact between said fines and the walls of said upper chamber.