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Mining of zinc demands the upgrading of different residues of the refining process. A method, which had been used over a period of several years, was based on the so-called Dorschel process. From the chemical point of view, the Dorschel process is a high-temperature redox process, combined with a flash distillation (sublimation) step.This process is based on the reduction of zinc compounds with coke at elevated temperature. The metal is then evaporated, reoxidized, precipitated by filtration, and refined hydro-/electrochemically. Zinc, lead, cadmium, nickel, cobalt, germanium, and copper can be refined from solid feed material by this process.Modem waste management also needs such methods for the treatment of hazardous waste from different industrial processes, and the applicability of the Dorschel process in the upgrading of galvanic sludge, dust from steel furnaces, and scrap of portable batteries has been investigated. The feed material used for investigation has a mean zinc content of 15 to 25 wt% and a mean lead content up to 10 wt%. The presence of sulfate determines the anionic nature of feed material from galvanic sludge.The capacity of the kiln used in the investigation is about 10JOOO metric tons per year. The efficiency of zinc recovery is about 95% to 98%. The matrix substances of the feed were dissolved in neutral to caustic slag. Sulfur dioxide was recovered by absorption, purification, and condensation. 759

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der für den reduktiven anaeroben Abbau benötigt wird, und an der Anode Sauerstoff entwickelt, der für den oxidativen aeroben Abbau benötigt wird. Der mikrobielle Abbau von PER und TRI erfolgt zunächst unter anaeroben reduktiven Bedingungen (s. Abb.). Dabei entstehen als Zwischenprodukte cis-Dichlorethen (cDCE) und Vinylchlorid (VC). Der LCKW-Ab-bau unter aeroben Bedingungen beschränkt sich auf die Zwischenprodukte cDCE und VC. Die anaerobe Dehalogenierung führt ebenfalls zu den Produkten Ethen und Ethan, allerdings mit einer geringeren Abbaurate als unter aeroben Bedingungen. Eine vollständige Dechlorierung kann somit sowohl reduktiv als auch sequenziell reduktiv/oxidativ erfolgen.

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