Abstract: Summary: Method and system for processing a substance in a retort (1) wherein the retort comprises at least one flow deflector internal to the retort. A substance (8) is loaded into the retort (1), the retort (1) is positioned or located in an oven (9), a first (10) and second (11) duct are attacked to the retort, a heat carrier fluidum is passed through the substance (8) in the retort (1) for drying and/or heating the substance inside the retort, an indirect heat is transfer is applied over the wall (3) of the retort (1) and process progress is controlled by means of a controlled indirect heat transfer and/or a flow provided into the retort inlet comprising a heat carrier fluidum.