four de calcination

OBS: calcination: The operation of heating an ore or a refractory material to a high temperature but without fusing in order to effect useful physical and chemical changes.
OBS: [calcination] differs from roasting because air is not supplied to the charge during heating. The essential difference between calcining and roasting is that roasting involves a chemical reaction between the gas and the solids, but in calcination the surrounding hot gas serves merely to provide the necessary heat.