The results of research for improving physical-chemical and agrochemical properties of phosphate  flour, obtained by phosphate various deposits enrichment, by increasing its grinding fineness, as well as  mechanical activation in the presence of various physiologically active substances, also through its partial activation incomplete stoichiometry norm of the hydrochloric and nitric acids are represented

Goncharik, I. I.

Gotto, Z. A.

Mozheyko, F. F.

Potkina, T. N.

Shevchuk, V. V.

The results of research for improving physical-chemical and agrochemical properties of phosphate flour, obtained by phosphate various deposits enrichment, by increasing its grinding fineness, as well as mechanical activation in the presence of various physiologically active substances, also through its partial activation incomplete stoichiometry norm of the hydrochloric and nitric acids are represented

Belarusian State Technological University

Chemistry and Technology of Inorganic Materials and Substances 75  УДК 622.364:622.765 F. F. Mozheyko, D. Sc. ( Chemistry), professor, Corresponding Member  of the National Academy of Sciences, leading researcher (IGIC NASB); I. I. Goncharik, PhD (Engineering), senior researcher (IGIC NAS of Belarus); Z. A. Gotto, researcher (IGIC NAS of Belarus); T. N. Potkina, PhD (Chemistry), senior researcher (IGIC NAS of Belarus); V. V. Shevchuk, D. Sc. ( Chemistry), head of the department of mineral fertilizers (IGIC NASB) PHOSPHATE ROCK: METHODS OF PREPARING AND APPLICATION  The results of research for improving physical-chemical and agrochemical properties of phosphate flour, obtained by phosphate various deposits enrichment, by increasing its grinding fineness, as well as mechanical activation in the presence of various physiologically active substances, also through its par-tial activation incomplete stoichiometry norm of the hydrochloric and nitric acids are represented. Introduction. The main raw materials for the production of phosphate fertilizers are natural phosphorite and apatite ores, differing not only in mineralogical composition, conditions of forma-tion, but also technological properties. Ascertained phosphate ore reserves are accounted for more than 60 countries and currently estimated at 63 067 mil-lion tons Р2O5, including 57 807 million tons of phosphate (91 wt. %) and 5.26 million tons of apa-tite (9 wt. %) ores [1–3]. The situation analysis in the global market of phosphate raw materials allows revealing the fol-lowing adverse trends that will only grow and have a significant impact on producers and consumers of phosphate fertilizers: – Export decline in phosphate raw materials by its traditional suppliers and increase in the propor-tion of phosphate raw materials processed by local producers of phosphate fertilizers; – Deterioration of phosphate raw material qual-ity as a result of depletion of high-quality ores; – The emergence of an imbalance between supply and demand by reducing the growth rate of extraction of phosphate raw materials while in-creasing the demand for phosphate fertilizers. These trends make it necessary to search and use alternative sources of phosphate raw materials. Main part. Phosphate fertilizers are divided into three main groups according to the degree of solubility: water-soluble – ammoniated superphos-phate, double superphosphate, ammophos, diam-mophos; not soluble in water, but citrate- and le-monsoluble – precipitate Thomas slag, Martin phosphate slag, thermal phosphates; sparingly so-luble phosphates – phosphate rock. Phosphate rock was the first phosphorus fertilizer, widely used in different agro-climatic regions. Its industrial output in Russia was initiated thanks to the works of A.N. Engelgrad. This is due to several factors, the most important of which are: – A unit of Р2О5 in phosphate rock is 2–4 ti-mes cheaper than in any water-soluble phosphate fertilizers; – Production of phosphate rock eliminates the production of large-tonnage environmentally ha-zardous waste; – Phosphate fertilizer is made from the most af-fordable phosphate raw material – phosphate rock; – Phosphate rock as opposed to water-soluble fertilizers is slowly soluble one with a long lifespan. In addition, phosphate rock is produced by simple technology without formation of burden-some large-tonnage production wastes such as phosphogypsum.  Production of phosphate fertilizer includes pre-liminary coarse crushing of clean ore on hammer or jaw crushers, drying with flue gases in rotary dryers, subsequent secondary crushing and dry grinding. Secondary crushing is done on the roller or hammer mills. For fine grinding ball or air-jet mills are used. The separation of finished phos-phate fertilizer from the larger particles to be re-turned to the regrinding is carried out in an air se-parator [4]. At present, the utilization of nutrients of ap-plied fertilizers is insufficient and ranges between 20–60 wt. %. Unlike nitrogen and potassium which losses are mainly due to the leaching with ground- and rain waters, low utilization of phosphorus (18–25 wt. % per year) is caused by its immobilization in the soil or Р2О5 retrogradation, which is deter-mined primarily by soil acidity and by content of free aluminum and iron ions in it, as well as active sesquioxides. Aluminosilicate and iron phosphates are spa-ringly soluble in water compounds. Their forma-tion  begins immediately after application in soil high-concentration water-soluble phosphate ferti-lizers. Most crops (cereals, potatoes, sugar beets) assimilate phosphorus with a maximum speed only 2–4 months after sowing. By this time most of concentrated water-soluble fertilizers such as am-mophos change on the acidic soils into marginally soluble compounds of iron and aluminum and con-cerning agrochemical efficiency their effect on crop yields is close to the action of phosphate fertilizer. 76 ISSN 1683-0377. Proceedings of BSTU. 2014. No. 3. Chemistry and Technology of Inorganic Substances The Mstislavl field is the most promising ac-cording to conditions for the occurrence and ex-traction of phosphate rock. Mstislavl phosphorite ore refers to the subtype of poor ores with low iron content of nodular type with Р2О5 content from 8 to 15 wt. %. Extensive researches on washability of phos-phate ores from Mstislavl deposits carried out over a number of years showed that Belarusian phos-phates are finely disseminated ores difficult for concentration. It is established that as a result of the primary concentration conducted by a dry or wet ore crushing, separation by size pieces on screens and by waste rock washing with water, Р2О5 content in the concentrate increases to 15–16 wt. %. Then the concentrates of primary enrich-ment are exposed to deeper secondary concentra-tion by flotation. In the circle of basic flotation the concentrate was obtained containing 20–22 wt. % of Р2О5, and after three recleanings Р2О5 content in the finished product increases to 27–28 wt. % at recovery of 80–90 wt. %, that can be used in the preparation of compound fertilizers. The resulting products, both in the first and second concentration contain indigestible for plants form Р2О5. Transforming them into mineral phosphate fertilizers is their transitions from an indigestible Р2О5 form into digestible. Nowa-days many ways to activate and to upgrade them have been proposed. This is usually done by de-composition of phosphate raw materials with min-eral acids: sulfuric, nitric, phosphoric and hydroch-loric acid. But for the acid treatment high-quality phosphate rock is required. This process is compli-cated, labor and energy intensive and is accompa-nied by the formation of large waste amounts, in particular phosphogypsum which disposal is now a big problem. It was studied the impact of mechanochemical activation on the phosphate rock to increase its component dilution, it was investigated the effect of physiologically acidic additives (eg, ammonium sulfate) on the mechanochemical activation process, the kinetic parameters of the process, in-cluding the content of water- and citrate soluble phosphate salts depending on the activation condi-tions, the type and the ratio of physiologically acid additives etc were determined. (Table 1). A number of factors on the activation of phos-phate rock of various fineness in the presence of adjuvants were studied Ammonium sulfate, am-monium chloride and potassium and mixtures the-reof were used as suitable physiologically acidic additives. The concentrate obtained at the first enrichment (Р2О5 content of 15.6 and 16.2 wt. %) from Mstislavl phosphate rock deposits and Pol-pinski phosphorite rock field (Р2О5 – 18.9 wt. %). were used as a phosphate raw material.  Table1 Effect of activation duration and physiologically acidic additives on the content of lemon soluble  Р2О5 form (fraction –0.063 mm) phosphorite rock from Mstislavl field (Р2О5 total content – 16.25 wt. %) Fertilizer  composition Time min Composition wt. % Р2О5LS/ Р2О5total, % Р2О5total Р2О5LSAmmonium sulfate : phosphate rock = 1 : 1 5 9.08 7.63 84.0 Ammonium sulfate : phosphate rock : potassium chloride =  = 1 : 1 : 1 5 7.73 7.00 90.6 Ammonium sulfate : phosphate rock R = = 1 : 1 10 9.08 7.75 85.4 Ammonium sulfate : phosphate rock : potassium chloride =  = 1 : 1 : 1 10 7.73 7.04 91.07 Ammonium sulfate : phosphate rock = 1 : 1 15 9.08 7.94 87.5 phosphate rock: po-tassium chloride = 1 : 1 15 12.95 8.59 66.3 Ammonium sulfate : phosphate rock po-tassium chloride =  = 1 : 1 : 1 15 7.73 7.44 96.25 Ammonium sulfate : phosphate rock = 1 : 1 30 9.08 7.92 87.2 phosphate rock : potassium chloride = = 1 : 1 30 12.95 8.59 66.4 Ammonium sulfate : phosphate rock : potassium chloride =  = 1 : 1 : 1 30 7.73 7.43 96.1 The above data clearly show that the interac-tion of physiologically acidic additive agents with phosphate rock, or rather with its phosphate com-ponent, the activation of the latter occurs, which promotes the transfer of phosphorus compounds into  a more mobile form, as evidenced by a significant increase in the relative content of Р2О5 lemon soluble form. Increasing the mixing time leads to the rise of the phosphate fertilizer activation in the presence of only ammonium sulfate or potassium chloride, and at their combined intro-duction, the maximum value is attained at 15 min interaction. Further experiments were conducted at the activation time 15 min. Activation of phosphate rock under the influ-ence of nitrogenous fertilizers, particularly ammo-nium sulphate is considerably more effective than when exposed to potassium chloride, which can be attributed to the higher acidity of ammonium Chemistry and Technology of Inorganic Materials and Substances 77  sulphate in comparison with potassium chloride (Table 2). The content of digestible Р2О5 form in relationship to the total Р2О5 when activated with  ammonium sulfate at a ratio of N : Р2О5 = 1: 1 reaches up to 87.5 wt. against 66.3% wt. % with  potassium chloride at the same ratio of components and the same time of activation. The most phos-phate activation is observed in the ternary systems. In this case the synergism of activating effect be-comes apparent. Combined nitrogen and potassium fertilizer introduction activates phosphate fertiliz-ers much more significantly on the basis of phos-phorite rock  than each individually Table 2  Influence of the composition, the ratio  of componentsin the mixture, the grind size  on the activation of washed phosphorite concentrate from Mstislavl deposit (Р2О5total content – 15.6 wt. %, the mixing time 15 min) Fertilizer  composition Size, mm content in the mixture, wt. % Р2О5LPS/ Р2О5total, % Р2О5total Р2О5LSPAmmonium sulpha-te : phosphate rock = = 1 : 1 –0.16 8.58 7.25 84.5 phosphate rock : potassium chloride = = 1 : 1 –0.16 12.24 6.13 50.0 Ammonium sulpha-te : phosphate rock : potassium chloride = = 1 : 1 : 1 –0.16 7.43 6.75 90.8 phosphate rock : pota-ssium chloride = 1 : 2 –0.16 6.30 5.75 91.3 phosphate rock : pota-ssium chloride = 1 : 2 –0.16 10.60 7.63 72.2 phosphate rock : potassium chloride = = 1 : 1 –0.063 8.58 8.00 93.2 phosphate rock : potassium chloride = = 1 : 1 –0.063 12.24 8.50 69.4 Ammonium sulpha-te : phosphate rock : potassium chloride = = 1 : 1 : 1 –0.063 7.43 7.00 94.5 phosphate rock : potassium chloride = = 1 : 2 –0.063 6.30 6.25 99.2 phosphate rock : potassium chloride = = 1 : 2 –0.063 10.60 8.13 76.6 Furthermore, in all cases studied the content of lemon soluble Р2О5 form both in absolute and in relative expression significantly increases with the rising dispersion of phosphorite rock. Thus, if at activation of washed phosphorite concentrate with overall size 0.16 mm in a binary mixture with am-monium sulfate or potassium chloride at a ratio of N : Р2О5 and Р2О5 : K2O   1 : 1 or N : Р2О5 : K2O 1 : 1 : 1 the content of lemon soluble Р2О5 form is 7.25, 6.13, 6.75 wt. % respectively, so in the case of activation of the fraction –0.063 mm – 8.00, 8.50, and 7.00 wt. % respectively. Relative digesti-bility of fine fraction phosphorus at activation with ammonium sulfate, potassium chloride, or a mixture thereof is 93.2, 69.4 and 94.5 wt. % vs. 84.5, 50.0 and 90.8 wt. % respectively, for a frac-tion of size 0.16 mm (Table 2). From these data it follows that in this case i.e. at activation fine fraction rock –0.063 mm ob-tained when grinding the initial ore of total coarseness –0.16 mm, the fine-dispersed milling of phosphorite concentrate is at the chemical acti-vation advantages. Elevated levels of ammonium sulphate and potassium chloride enhance phos-phorite rock activation.  Thus, if at the ratio P : N and P : K 1 : 1 the relative solubility is 84.5 and 50.0 wt. % respec-tively, then at the ratio of 1: 2, this figure has risen to 91.3 and 72.2 wt. % respectively (the fraction – 0.16 mm). For samples of P : N and P : K 1 : 2  (–0.063 mm fraction) relative digestibility increased up to 99.2 and 76.6 wt. vs. 93.2% and 69.4 wt. % rrespectively, at a component ratio of 1 : 1. Similar activation results were obtained when used as a phosphorite component in NPK-phosphate fertilizers from Polpinski field. Thus, it was found that pre-mixing of ground phosphate rock with physiological acidic additives can be regarded as one of the methods of improv-ing the effectiveness of phosphate rock. This is confirmed by agrochemical tests of mixtures of ground phosphate rock from Mstislavl phosphate deposits with ammonium sulfate. It is shown that its effectiveness both on sod-podzol loamy and on sandy soils increases to the level of the best forms of phosphorus water-soluble fertilizers (ammophos and ammoniated superphosphate). Another unconventional method of obtaining phosphate fertilizers from poor phosphate raw ma-terial is its treatment with inorganic acids, but in much smaller quantities than it is required for the complete decomposition of phosphate rock. In this case the so-called under- or partial decomposition of phosphates are formed. Agrochemical phosphate fertilizer efficiency, untreated and treated with acids, was compared with that of water-soluble phosphates. The interac-tion of water soluble phosphate with the soil re-duces its availability to plants while the treated with small amounts of acids phosphorite under these conditions, becomes both absolutely and relatively more effective. 78 ISSN 1683-0377. Proceedings of BSTU. 2014. No. 3. Chemistry and Technology of Inorganic Substances Table 3  The chemical composition of the ground phosphate rock,  obtained by concentration of phosphates from Polpinski field P2O5 CaO MgO Fe2O3 Al2O3 SiO2 F SO3 H2O Н.о. P.p.p 18.9 29.4 0.63 2.29 1.61 3.36 2.5 2.3 1.05 0.55 7.51  The best results were obtained with embodi-ments of phosphoric acid; the effectiveness of the products of incomplete decomposition of phos-phate rock with hydrochloric and nitric acids was lower. Harvest of some embodiments of expe-rience as a result of the phosphorite activation in-creased more than twice compared with the harvest assisted by the untreated phosphate rock. The optimal dose of phosphoric acid for treatment is 7.8 wt. % from weight of phosphate rock. When phosphate rock processing with phosphoric acid it has been additionally absorbed from it almost two times more phosphorus than from not processed phos-phate rock. Thus the efficiency of the agent used for the partial decomposition is 5–8 times higher than for soluble phosphate. In order to process the optimal composition of complex fertilizers, in which a portion (10–30 wt. %) of water-soluble phosphates such as ammophos will be replaced by a cheaper and affordable chem-ically activated phosphorite, we have conducted the researches on activation of nodular phospho-rites from Polpinski deposits with hydrochloric and nitric acids taken in the lower quantity than it is necessary according to the stoichiometric standard. The concentration of nitric acid was 55.7 wt. %, hydrochloric – 21.8 wt. %. The chemical composi-tion of the investigated phosphate rock is presented in Table 3. Phosphorite concentrate from Polpinski depo-sits is received after the initial ore concentration by washing, followed by primary flotation. The  chemical and X-ray analysis results showed that the main rock-forming phosphate mineral in the studied samples is fluorinecarbonateapatite. The studies found that modifying acids influ-ence simultaneously all the components of the phosphate fertilizer on the particle surface. They contribute to the degradation of impurity minerals and to the formation of water-soluble and lemon-soluble phosphates. With increasing modifying acid content, the calcium and iron ion extraction into aqueous and into 2% citric acid phosphate ex-tract increases as well.  Hydrochloric acid is a more potent activator of the phosphate fertilizer than nitric acid: data on component extraction into the aqueous extract and into 2% citric acid sample extract modified with hydrochloric acid is higher than with the nitrogen acid. It is shown that with increasing modifying acid content the degree of all component extraction increases as well. The extraction degree value into the aqueous extract Ca (from 12.1 to 37.97 wt. % (treatment HCl) and from 6.59 to 29.02 wt. % (treatment HNO3)) is higher than the recovery rate of Р2О5 (from 2, 9.88 to 66 wt. % (treatment HCl) and from 1.72 to 14.3 wt. % (treatment HNO3)). This difference means that the acids affect on im-purity minerals to a greater degree than on the ba-sic phosphate substance.  It is shown that the following Р2О5 composi-tion relations: inorganic acid: with hydrochloric acid treatment of Р2О5 : HCl = 1 : 0.2, with nitric acid treatment Р2О5 : HNO3 = 1 : 0.4 can be consi-dered as optimal conditions to improve the quality characteristics of phosphate rock. Conclusion. It was established that in the pres-ence of physiologically acidic additives, phosphate rock is activated, as evidenced by a significant in-crease in the relative lemon soluble form of Р2О5 composition. It is shown that activation of phosphate rock under the ammonium sulfate influence occurs more efficiently than in the presence of potassium chlo-ride that due to the higher ammonium sulfate acidi-ty compared to the potassium chloride. It is shown that in the presence of physiologi-cally acidic substances, numerous defects in the crystal lattices of phosphate rock phosphate miner-als are formed. Their profound transformation, phase transformations with possible partial substi-tution of calcium cations with potassium and am-monium cations, and fluorine anions with hydroxyl – and chlorine ions occur within the fluorinecarbona-teapatite structure.  References 1. Беглов Б. М., Ибрагимов Г. Г., Садыков Б. Б. Нетрадиционные методы переработки фос-фатного сырья в минеральные удобрения // Химическая промышленность. 2005. № 9. С. 453–468. 2. Перспективы обеспечения промышлен-ности минеральных удобрений фосфатным сырьем / А. И. Ангелов [и др.] // Химическая промышленность сегодня. 2006. № 7. С. 11–17. 3. Коршунов В. В., Коршунов Д. В. Рынок минеральных удобрений: долгосрочные тен-денции и текущая ситуация // Химическая про-мышленность сегодня. 2007. № 9. С. 4–10. 4. Ратобыльская А. Д., Бойко Н. Н., Кожев-ников А. О. Обогащение фосфатных руд. М.: Недра, 1979. 261 с. Received 11.03.2014 

Phosphate rock: methods of preparing and application

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Phosphate rock: methods of preparing and application

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Belarusian State Technological University