Fractionation and decontamination of scrap processing residues, employs successive wet screening drums with sedimentation and recycling of process water

摘要

Contaminated material (a) is fed successively into separate screening drums (1, 2) with process water in the ratios 1 : 1.5 to 1 : 3. The first, 6-14 mm mesh drum, turns at 5-20 rpm. The washwater suspension containing fine grains is fed to a further screening drum. This 0.5-3.5 mm mesh drum, turns at 20-40 rpm. Each drum separates a washed coarse fraction and an aqueous fine fraction. The coarse material is removed separately from each stage. The aqueous fine fraction finally reaches a sedimentation tank (3). Separated water is treated in one or more low-pressure, wet-oxidation plants (5). It is returned directly to the treatment tank, for recycling. A variant based on the foregoing principles is described. Nozzles and lifting flights are employed in drum-washing of the material. Water from the first drum is introduced into the second. In a variation, only prepared process water is supplied as washwater to the drums. In the sedimentation tank, fines (arising in the ratio 100 : 3 with respect to the input quantity) are deposited or supplied to a conventional biological treatment plant. An independent claim is included for the corresponding plant.