Russian Academy of Natural Sciences, Moscow, Russia:

V. Zh. Arens, Vice-President, Professor, Doctor of Engineering Sciences
+O. M. Gridin, Professor, Doctor of Engineering Sciences
G. Kh. Khcheyan, Academic Secretary, Mining and Metallurgy Section, Doctor of Engineering Sciences, mogmsraen@mail.ru

State Institute of Mine-Chemical Raw Materials, Lyubertsy, Russia:

N. N. Derbunovich, Head of Laboratory, Doctor of Engineering Sciences

Cropping needs fertilizers based on phosphorus compounds to enrich soil. The demand for the fertilizers continuously grows. This article describes phosphate reserves entered in the State Balance of the Russian Federation. It follows from the State Balance than much phosphorus reserves occur as nodular phosphorites. The major part (92 %) falls at low-grade nodular ore of the Vyatka-Kama and Egorievsky deposits yet non-exploited to produce standard soluble fertilizers. The objective set is to create a technology to extract phosphates from the mentioned ore chemical conversion of the products into soluble fertilizers later on. The basis was assumed as the mining-popular method of underground leaching and the research object was the Vyatka-Kama deposit ore with the high content of Р₂О₅ in nodules (up to 26 %) and possessing high solubility in diluted acid solutions. Nitric acid was selected as the leaching agent. Leaching of phosphorites was complicated by the presence of acid-soluble admixtures—calcium and magnesium carbonates, iron and aluminium oxides and other compounds. The experiments showed that the higher Р₂О₅ recovery was reached with 5–10 % nitric acid. The commercial trial was executed in the test field of the Vyatka-Kama deposit. The productive stratum was represented by a coarse-nodular layer 0.4–0.45 m thick. The drilling pattern 1010 m consisted of 16 holes. The process flow chart included total circulation of solutions and maximum utilization of leaching products. All in all, at the solution consumption of 900 m³, 5 t of fertilizers were produced with the higher content of ferric phosphate. The studies have proved the efficiency of the underground leaching method for low-grade phosphorites.

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