Three-stage roasting of bulk material - in internally heated predryer and externally heated rotary pre-roast and final roast tunnels

摘要

The installation is intended for roasting bulk material as preparation for further treatment. It comprises a rotary tunnel containing an axial burner to pre-dry the material at around 100-105 deg. centigrade, the resulting vapour and combustion gas passing to a precipitator. The pre-dried material is fed to a rotary pre-roast tunnel externally heated to around 850 deg., and from there to a rotary final roasting tunnel externally heated (15) to around 1350 deg. The vapours developed in the tunnels are extracted and together pass to a separate precipitator, whilst the combustion gas from their respective heating chambers is extracted (at around 800 deg.) and together pass (23) to the pre-drying tunnel (2). Appts. is used for roasting bulk material in preparation for further treatment. The amound of vapour (7,13) to be seeded with precipitation agent and handled by the precipitator is considerably reduced.