St. Petersburg State Polytechnic University (St. Petersburg, Russia):

Konevskiy M. R., Dr. Eng., Prof., e-mail: chemmet2008@yandex.ru

Phosphorous iron ores, containing 0.2–2.5% (mas.) of phosphorus pentoxide (P₂O₅), traditionally used in the steelmaking due to lack of impurities-free iron ores. Before invention of the basic oxygen metallurgy (BOS), the processing of phosphorus-containing cast iron was made in Thomas converters and tilting open-hearth furnaces. This in fact was a complex processing of raw material, producing high concentration P₂O₅ slags widely used in agriculture along with metal products. In recent decades, the problems have accumulated in this area due to the incompatibility of the increasing requirements to quality of steel with phosphorus-containing cast iron processing in modern highperformance BOFs. Accordingly, a transition to mixed furnace charge with decreased phosphorous ores content is being made on blast furnaces, thus giving a phosphor percent in cast iron at 0.2–0.6% (mas.). This facilitates the control of phosphorus, however, increased production costs and reduced production rates of BOFs are not covered by the revenue from slags due to the low concentration of nutrient chemicals. Proposed measures for the rational use of depleted phosphate slags: by reduction of slag to ferrophosphorus and its use as a reducing agent of the rest of the slag. Thus the slag is enriched by P₂O₅ and refined from the oxides of iron. The process uses the heat accumulated by liquid slag and the heat of oxidation of phosphorus. Enriched phosphate slag can be applied not only as a fertilizer, but as a intermediate for the production of yellow phosphorus. Thus, the conditions can be created for deep processing of phosphorous iron ores and reducing the burden on the environment by reducing the amount of slags exported to dump waste.

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