Abstract: The invention comprises a sinter belt and a collector, vacuum chambers, a gas cleaning device, an air purifying device, and an exhauster mounted adjacent the belt. Above the sinter belt are mounted assemblies for loading a bed and a charge, and an ignition hearth. Downstream from the sinter belt are mounted a sinter breaker and an inclined chute wherein are mounted vibrating screens communicating with a cooler for a sinter return and for the bed, and an air classifier. The air classifier comprises a fan, a diffuser, a movable grid for varying the speed of the air produced by the fan, and a partition member forming a settling chamber together with the chute. Within the settling chamber is mounted a device for settling coarse fines, said device communicating with the collector through the air purifying device, and with the cooler for the sinter return.