A device for carrying out mechanical, chemical and/or thermal processes in a housing (3) having mixing and cleaning elements (5) on shafts (1, 2), wherein the mixing and cleaning elements (5) of the shafts (1, 2) engage into each other when rotating about the axes thereof and two mixing and cleaning elements (5) are arranged at least one shaft (1, 2) consecutively in the axial direction in a 180° rotation-symmetrical manner about the axis (A) of the shaft (1, 2). Each mixing and cleaning element (5) comprises a disc element (6) and the disc element (6) has an outer edge (7) running in a radius (r) in an arch segment of approximately 90° or slightly bigger about the axis (A) of the shaft (1, 2) and wherein side edges (8.1, 8.2) abut on both sides toward the shaft (1, 2), wherein one or more bars (9.1, 9.2) sit on the edge (7).