4. Two-support furnace

By increasing precalcination to 65% of the total fuel flow, a decarbonation rate of 90-95% was achieved. This made it possible to reduce the length of the furnace's decarbonation zone, where exchange conditions between fumes and material are poor.

In recent years, the L/D ratio (length to diameter) of pre-calcined dry furnaces has, as we have seen § 1 , been reduced from around 14/18 to between 10 and 13, enabling furnaces to be designed with two supports instead of three, thus...