Peter the Great St. Petersburg Polytechnic University (St. Petersburg, Russia):

M. R. Konevsky, Dr. Eng., Prof., e-mail: chemmet2008@yandex.ru
P. V. Kovalev, Cand. Eng., Associate Prof., e-mail: kovalev_pv@spbstu.ru
S. V. Ryaboshuk, Senior Lecturer, e-mail: ryaboshuk_sv@spbstu.ru
A. A. Kur, Cand. Eng., Associate Prof., e-mail: kur_aa@spbstu.ru

The reasons for the complete or partial rejection of the phosphorous iron ores (PIO) usage in ferrous metallurgy contrary to a shortage of iron ore raw materials are considered. Dephosphorization of metal from high-phosphorous cast irons leads to the complication of technology and deterioration of the production economics because of high intensity of the converter smelting and increasing requirements for the purity of steel. Limitation of PIO share in the blast furnace charge and decrease of phosphorus contents in cast irons led to a deterioration of the steel phosphate slag (PS) quality as fertilizers, which results in its disposal to the dump. Information on the opposite foreign practice of obtaining satisfactory phosphate slags is given, which is an increase in cast iron phosphorus contents by addition of ferrophosphorus. The reasons for abandoning this practice are analyzed. The authors studies aimed at increasing of phosphorus concentration in phosphate slags to bring PS conditions up to the requirements for specially produced by the chemical industry fused fertilizing phosphates and/or an intermediate product for the production of yellow phosphorus are described. On the basis of research and a technical and economic assessment, the feasibility of returning to the use of ferrophosphorus after making appropriate adjustments was substantiated. According to the proposed technology, phosphorous ferroalloy is used as a direct reagent in relation to substandard phosphate slags using their physical heat and exothermic reaction. The process is feasible outside the main metallurgical units and does not require the complication of steelmaking technology. It is possible to use ferrophosphorus as a by-product of the phosphorus industry due to its excess in the world market. It could also be obtained by reduction smelting of dump PS or current discharge slag. Phosphorous iron ores deep processing and the associated production of expensive chemical products will rise economic viability of “phosphorus-infected” iron ores usage.

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