ISSN 0040-5795, Theoretical Foundations of Chemical Engineering, 2013, Vol. 47, No. 3, pp. 225–230. © Pleiades Publishing, Ltd., 2013. Original Russian Text © L.L. Tovazhnyansky, V.P. Meshalkin, P.O. Kapustenko, S.I. Bukhkalo, O.P. Arsenyeva, O.Yu. Perevertaylenko, 2013, published in Teoreticheskie Osnovy Khimicheskoi Tekhnologii, 2013, Vol. 47, No. 3, pp. 279–285. 225 INTRODUCTION A major problem for the industry of producing phos- phate fertilizers as a whole is the formation of large-ton- nage and burdensome waste, i.e., phosphogypsum. The amount of phosphogypsum alone obtained as a waste product of wet-process phosphoric acid that goes into garbage dumps exceeds the worldwide production of natural gypsum. Thus, investments into making surface dumps of phosphogypsum on the ground with a water circulation system may run to about 8% of the invest- ments into the manufacture of phosphoric acid, and the costs of maintaining these dumps of phosphogypsum may be as large as 3.9% of total operating costs [1]. In recent years, the industry of phosphate fertilizers has decreased its output. For example, the Ukraine has been faced with total disappearance of plant available forms of phosphates from the soils; these phosphates had been accumulated in soils over the years of inten- sive chemicalization. Thus, an 80% reduction in the dosages for applying phosphate fertilizers compared to those in 1990 resulted in a decrease in the weighted average content of labile phosphorus in the soils by 1.1—1.4 mg over the last 10 years. [2]. The effective- ness of the agricultural production depends on the timely application of the required amount of mineral fertilizers in order for the losses of the active substance with the cut crop to be compensated for. In Ukraine, the area of arable lands with low and medium contents of labile phosphorus is nearly 57% of the total area of arable land [3]. Due to the low supply of the soils with phosphorus potentially available to plants, the recoup- ment of phosphate fertilizers may presently be rather high because, on average, 1 kg of P 2 O 5 provides an increase of 4–5 kg of grain or 30–40 kg of root crops of sugar beets. The process flow charts used to manufac- ture fertilizers from phosphate rock are mainly based on the decomposition of an enriched material with either acid or acid mixtures. When the most generally employed method of treating the apatite concentrate with sulfuric acid is used (Fig. 1), about 94% of phos- phorus, 10–20% of fluorine in the form of compounds, and part of the phosphogypsum being formed are extracted from the raw materials. The following properties of phosphorus are major obstacles to its conversion: radioactivity and the pres- ence of impurities (P 2 O 5 in soluble, cocrystallized forms; fluorine compounds; SiO 2 ; Al 2 O 3 ; Fe 2 O 3 ; Na 2 O; and organic substances.) Phosphogypsum, in which the radium content does not exceed 10 pCi/g, is considered to be nonradioactive and can be used to produce build- ing materials [2]. The development and introduction of the efficient technologies of phosphogypsum conversion can be helpful when solving the problem of the utilization and conversion of gypsum that is formed as waste in other production processes. In the complex technologies of phosphogypsum conversion, stages of the high-temper- ature treatment of materials take place. For example, in the production of ammonium sulfate, chalk, which is used to manufacture manufacturing cement and lime, and concentrates of rare-earth elements, calcium car- bonate is subjected to roasting; as a result, calcium oxide is produced, which takes part in a number of chemical reactions. The aim of the study is also the formulation of the general approaches to the establishment of general approaches to the development of waste-free integrated production processes, the main principles of which can be formulated as follows: – the development of energy-process flow charts that involve the total reprocessing of raw materials and Energy Efficiency of Complex Technologies of Phosphogypsum Conversion L. L. Tovazhnyansky a , V. P. Meshalkin b , P. O. Kapustenko a , S. I. Bukhkalo a , O. P. Arsenyeva a , and O. Yu. Perevertaylenko a a National Technical University Kharkiv Polytechnic Institute, Kharkiv, Ukraine b Mendeleev University of Chemical Technology, Moscow, Russia e-mail: bis.khr@gmail.com Received September 14, 2012 Abstract—The paper describes the feasibility of increasing the energy efficiency of the technologies of the comprehensive phosphogypsum conversion. The main directions in obtaining target products are reported. The classification of the phosphogypsum conversion technologies based on the level of energy con- sumption is suggested. The main variants of the development of energy-saving technologies of phosphogyp- sum conversion using the methods of integrating thermal processes and the state-of-the-art heat-power equipment are proposed. DOI: 10.1134/S0040579513030135