Entwicklung eines Recyclingprozesses zur simultanen Rückgewinnung von Wertmetallen aus Reststoffen der Blei- und Zinkindustrie
Research output: Thesis › Doctoral Thesis
In the present PhD thesis an innovative recycling process for the simultaneous recovery of valuable metals like lead, zinc and silver from residues, generated in the primary lead- and zinc-production, is developed. Due to the varying production processes of both base metals, the generated waste materials are quite different, whereby the lead- respectively the lead-zinc-residue is a slag, generated by pyrometallurgical processes and the zinc-residue is a mixture of leaching- and leach purification-remainders, generated by hydrometallurgical processes. The recycling of dumped residues, like the described lead-blast furnace slag with a concentration of 22.50 wt.-% zinc, 9.30 wt.-% lead and 1000 ppm silver is beside the recycling of currently generated residues, an option for the conservation of primary resources. The characterization of the waste materials in conjunction with the evaluation of already developed hydrometallurgical and pyrometallurgical recycling processes shows that an ecological processing can only be done by a pyrometallurgical process. As technical and economical requirements the valuable metals have to be recovered in different fractions, where each one represents a saleable intermediate product. In course of the developed “lead-bath recycling process” the residue is charged on a lead bath and the containing valuable compounds of zinc, lead and silver are reduced by a carbothermal reduction. The products are a lead alloy in which silver and lead are collected, a dust with a high content of zinc oxide and an inert-slag with a low concentration of disturbing heavy metals. Depending on the process temperature the reduced zinc evaporates and leaves the process through the off-gas system. The zinc-vapor is post-combusted with air and the generated dust is collected in the bag house filter. For the oxide slags of the primary lead production, respectively for the in detail studied Imperial-Smelting-slag, the reduction on the lead bath is directly done without pretreatment or previous enrichment of the valuable metals. The residue of the hydrometallurgical zinc production contains several mineralogical phases, so a previous enrichment of silver and lead by flotation is investigated. Furthermore these residues contain a lot of sulfur, which has to be removed by a thermal pretreatment step. For the determination of the optimum parameters for the “lead-bath recycling process”, a process simulation as well as laboratory scale trials are carried out for both residues. According to this a process evaluation for technical scale trials in a Top-Blown-Rotary-Converter (“In-Bath” reactor) and in a DC-Submerged-Arc-Furnace (“In-Bed” reactor) are studied. The results show that the TBRC is the more appropriate aggregate to separate the valuable metals in different product fractions and is also the better choice for the selective reduction.
|Translated title of the contribution||Recycling process for the simultaneous recovery of valuable metals from residues of the primary lead and zinc industry|
|Publication status||Published - 2015|