Plant and process for the thermal treatment of electronic scrap (Pilot scale 40 kg/h, planned technical scale 3000 to/a). The nature of this result is an apparatus for the thermal treatment of electronic scrap, in general of polymeric materials with a high content of inert materials and metals as well as halogenated compounds. Based on this new apparatus a process has been worked out to realize a separation of such feeds in de-halogenated oil fractions, post process-able residues and fractions containing the harmful substances.
The apparatus is a gas tight rotary kiln with conveyor screw and steel spheres. The conveyor screw and the spheres are used to mix the material and to realize a good heat transfer. Furthermore, the residue material is more or less grinded by the spheres during processing. A post-processing, for example electrolysis of precious metals is possible.
The reactor units can be coupled to a cascade to obtain different oil fractions, for example monomer fractions or oil fractions for fuel substitution or to be used as phenolic glue. The halogenated compounds are separated or decomposed and treated separately.
For example a housing fraction of computer towers and monitors with a chlorine- and bromine content of 2,4 wt-% in total can be decomposed by stripping with inert gases (nitrogen) at a pyrolysis temperature of about 400°C without forming significant amounts of chlorinated biphenyls PCBs, dioxins PCCDs and furans PCDFs, even a significant amount of oxygen and phenols are apparent during the pyrolysis (Determination of PCBs, PCCDs and PCDFs based on USEPA Method 8280 Rev 1, Dec. 1996 at center of environmental science & technology, university of Missouri-Rolla, Prof. S. Kapila.
All mentioned compounds are below detection limit of several ng/g in case of PCCDs and PCDFs (Example: 4 ng/g (2,3,7,8-T4CDD); 50 ng/g (O8CDF)) and 1 mg/g in case of PCBs.)To prevent or control the formation of polybrominated dioxins and furans the temperature levels and residence times have to be worked out carefully. A post-treatment procedure of the oil fractions helps to decompose those components