Abstract: A process for the firing and sintering of granular material in a gas or oil heated shaft furnace is disclosed in which the material, fed from the top of the furnace passes downwards successively through an entry zone, a preheating zone, a firing zone in which burners are disposed around the furnace wall, and a cooling zone, and in which the feeding of the material at the top of the furnace is so effected that a central depression is maintained in the upper surface of the material in the entry zone, said surface sloping downwardly from the periphery of the entry zone into the central depression, so that segregation of the material occurs automatically, the coarser pieces of material rolling into the central depression, whereby a column of the coarser material is maintained along the vertical axis of the furnace.