Abstract: Thin-layer evaporators are described in which evaporation cylinders and a cylindrical vapor-collection vessel of the same height are mounted to expand in parallel between horizontal base and top plates joined by a vertical jacket surrounding the cylinders and vessel and confining together with the plates a steam jacket. Rotors in the cylinders apply thin layers of the substance to be dried to the inner surfaces of the cylinders, from the tops of which vapors are discharged to the top of the vessel. A collecting conduit leads vapor from the bottom of the vessel to a compressor that delivers the compressed vapor to join a supply of super-heated steam passing into the steam jacket. Droplets separated in the vessel are discharged from the vessel through an outflow conduit. Solids and/or concentrates fall out of the evaporation cylinders into a clearing chamber from which they are evacuated into a trap by a rotary scoop.