Granular material thermal cleaning system

摘要

The system is for material containing a small amount of water, esp. earth, this being heated sufficiently to vaporise impurities contained. In a first stage it is brought into direct contact and in contraflow with a heating inert gas flowing in a closed circuit. This expels volatile ingredients from the material, these being enriched in the middle part of the stage and discharged in a small gas current. In a second stage the material is cooled by direct contact with a contra-flowing gas current. The inert-gas current flows in succession through the second and first stages, additional heating gas being blown into it between the stages. Hot exhaust gas can be used as the additional gas, and dust can be extracted from the inert-gas current after leaving the inert gas the first stage, it being then passed to the second stage.