Rotates a tube that internally tumbles the material. Hot gas is passed through the tube. ![](https://www.zkcomp.com/upload/images/2025/12/9d46ba646e1fc2f0.jpeg) ![](https://www.zkcomp.com/upload/images/2025/12/4d92c2648fd31591.jpeg) ![](https://www.youtube.com/watch?v=312wyuX2lFc)