Abstract: Residual metallurgical materials which contain zinc and lead are reprocessed by a thermal treatment in a circulating fluidized bed. The required heat is generated in that solid carbon is combusted in the fluidized bed reactor of the circulating fluidized bed. A solid carbon content of 5 to 30% is maintained in the lower part of the fluidized bed. Oxygen-containing gases are supplied to the upper part of the fluidized bed reactor, and CO.sub.2 is formed only in such an amount that zinc metal will not be reoxidized. Substantially all solids are removed from the discharged suspension in a recycle cyclone and are recycled. The gas is cooled to a temperature at which zinc metal is oxidized to ZnO. The dustlike compounds of zinc and lead are separated from the gas.

Abstract: A waste pickle which has been formed in the surface treatment of rolled stock consisting of steel and contains metal salts and acids and specifically contains nitric and hydrofluoric acids and nickel salts, chromium salts, and iron salts is subjected to an acid dialysis and a membrane electrolysis. To permit a recycling of free acids at a high rate and a recovering of the metals in a form in which they can directly be used in the melting process, the acid dialysis performed for a recovery of the free nitric acid and hydrofluoric acids is succeeded by a membrane electrolysis, in which the metals are recovered from the depleted effluent from the acid dialysis, which effluent has been depleted of free acid, and the enriched effluent from the acid dialysis, which enriched effluent has been enriched with free acids, and the effluent from the membrane electrolysis, which effluent has been depleted of metals, are subjected to an evaporation.

Abstract: A zinc- and lead-containing residue from a metallurgical plant is reprocessed by a thermal treatment in a circulating fluidized bed system. A major part of the heat demand is satisfied by a combustion of solid carbonaceous material in the fluidized bed reactor of the circulating fluidized bed system. A reducing fluidizing gas, which is virtually free of free oxygen, is fed to the lower part of the fluidized bed reactor. A solid carbon content of from 5 to 30% is adjusted in the fluidized bed in the lower portion of the fluidized bed reactor, which is supplied in its upper portion with oxygen-containing gases and in which CO.sub.2 is formed only at such a rate that zinc metal is not reoxidized. Substantially all solids are removed in a recycling cyclone from the suspension discharged from the reactor and the removed solids are recycled. The gas is cooled to a temperature at which zinc metal is oxidized to ZnO. The dust-like zinc compounds and lead compounds are removed from the gas.