Method for recovering useful metals from dust discharged from metal refining metallurgical furnace

In the method for recovering useful metals from dust discharged from a metal refining metallurgical furnace which contains Fe.sub.2 O.sub.3, Zno and PbO, which comprises:

• charging into the entry of a rotary kiln, a granular carbonaceous reducing agent, and said dust containing Fe.sub.2 O.sub.3, ZnO and PbO;
• the amount of said granular carbonaceous reducing agent being equal to the amount necessary to reduce the ZnO and PbO contained in said dust, to reduce the Fe.sub.2 O.sub.3 contained in said dust to FeO, and an amount necessary as fuel to supply the heat required for said reductions;
• moving said dust and said reducing agent toward the exit of said rotary kiln;
• the atmosphere in the interior of said rotary kiln comprising a reducing atmosphere zone for a major portion of said interior starting from the entry section of said rotary kiln and an oxidizing atmosphere zone which is a minor portion of said interior including at least a part of the exit section of said rotary kiln, the temperature of said interior of said rotary kiln being increased by the combustion of a fuel horizontally ejected from at least one burner installed at said exit section of said rotary kiln toward said interior of said rotary kiln;
• reducing said ZnO to Zn, said PbO to lead Pb and said Fe.sub.2 O.sub.3 to FeO in said reducing atmosphere zone, and vaporizing said Zn and said Pb to separate said Zn and Pb from said dust;
• reoxidizing, in said oxidizing atmosphere zone, said Zn and said Pb thus separated;
• and, discharging the resultant ZnO and PbO, together with exhaust gases produced in said rotary kiln, from said rotary kiln, and recovering said ZnO and PbO;
• the improvement comprising
• reoxidizing said FeO into Fe.sub.3 O.sub.4 and Fe.sub.2 O.sub.3 in said oxidizing atmosphere zone thereby lowering the amount of said reducing agent used as the fuel by an amount corresponding to the heat obtained from the reoxidation heat of said FeO.