Method for recovering useful metals from dust discharged from metal

Abstract

In a method for recovering zinc and lead from a dust containing ferric oxide, zinc oxide and lead oxide discharged from a metal refining metallurgical furnace, the dust is charged into the entry of a rotary kiln together with a granular carbonaceous reducing agent. The atmosphere of the interior of the kiln comprises a reducing atmosphere zone accounting for a major portion of the interior including the entry section of the kiln and an oxidizing atmosphere zone accounting for a minor portion of the interior including at least a part of the exit section of the kiln. The temperature of the interior of the kiln is increased by the combustion of a fuel from at least one burner installed at the exit section of the kiln directed toward the interior of the kiln. The dust is reduced in the reducing atmosphere zone to vaporized zinc and lead, and also to reduce the ferric oxide into ferrous oxide. The resultant zinc and lead are reoxidized in the oxidizing atmosphere zone, and discharged from the kiln, together with exhaust gases produced in the kiln to recover zinc and lead. The method includes the characterizing step of reoxidizing the ferrous oxide into the ferric oxide in the oxidizing atmosphere zone. The characterizing step has an effect enabling saving an amount of the reducing agent used as the fuel which corresponds to the amount necessary to generating the heat corresponding to that obtained by the reoxidation heat of the ferrous oxide.