Metallgesellschaft Aktiengesellschaft

Rolf Kola

Wolfgang Fennemann

Dieter Jentsch

Disclosed is a process of removing zinc from a phosphating process sludge wherein the phosphating process sludge is mixed with an additive adapted to form slaglike compounds of iron, calcium and/or barium with the phosphorus component of the phosphating process sludges. The mixture is reacted at temperatures of at least 800.degree. C. under reducing conditions. A previous agglomeration, particularly pelletizing, of the mixture will be of advantage. For a formation of iron compounds it will be particularly desirable to employ reaction temperatures of at least 900.degree. C., preferably of at least 1000.degree. C. and most preferably of at least 1100.degree. C. Metallurgical dusts are particularly suitable additives. For a formation of iron compounds it will be desirable to select a Fe:P molar ratio of at least 1.0 in case of a reaction temperature of .ltoreq.950.degree. C., of at least 1.5 in case of a reaction temperature of 950.degree. to 1050.degree. C., and of at least 2.0 in case of a reaction temperature .gtoreq.1050.degree. C. For a formation of Ca and/or Ba compounds a molar ratio of Ca:P or Ba:P equal to or higher than 1.5 should be selected. The process can be integrated to special advantage in the waelz processing of metallurgical dusts.

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Munich, Georgia

Rolf Kola