Salt composition and physicochemical processes in the volume of fertilizer granules at the storage stage

The results of studies of the salt composition and physicochemical processes occurring in separate layers (volume) of granules of complex fertilizers based on ammonium phosphates at the stage of storage in the interval up to 180 days are given. The data of chemical and physicochemical studies, as well as the analysis of microphotographs and element-by-element composition of granules showed the absence of a significant gradient of concentrations of individual components in the volume of granules when they arrive from the technological process. The course of secondary conversion processes in the volume of granules during 3 and 6 months of storage was established, leading, in particular, to a significant decrease in the content of ammonium dihydrogen phosphate in the product from 25.41-27.91 to 1.23-3.25 % and urea, as well as the formation of newdouble salts and adducts: (K_χ,(NH₄)_1-χ)•H₂PO₄, CO(NH₂)₂•NH₄Cl. The change in the phase composition of the product during long-term storage and the associated chemical interaction between the layers of individual granules is accompanied by an increase in caking. It is established that during 3 and 6 months of storage, the content of the liquid phase increases, which leads to a partial decrease in the content of individual components. The most active process of sorption of water vapor proceeds in the 1st (outer layer) of granules, while fluctuations in its content in deeper layers are within the margin of error. The dependence of the caking of the product on the type of injected nitrogen-containing component and the forms of nitrogen content in it has been established. The results of the study made it possible to recommend ways to reduce caking and improve the physical and mechanical properties of complex fertilizers during their storage and transportation: increasing the molar ratio at the ammoniation stage to values corresponding to the formation of diammonium phosphate; increasing the ratio of ammonium to the amide form of nitrogen; an increase in the proportion of granular urea in the composition of the fertilizer, followed by the complete exclusion of prilled urea.

1. Klassen P. V., Gryshal' Y. G. Main processes of the technology of mineral fertilizers. Moscow, Khimiya Publ., 1990. 304 p. (in Russian).

2. Norov A. M., Sukhodolova V. Y. Applying the experience and scientific potential of JSC “NIUIF” to create and implement the best available flexible technologies for complex phosphorus-containing fertilizers. Trudy NIUIF. T. 2 [Proceedings of the NIUIF. Vol. 2]. Vologda, Drevnosti severa Publ., 2019, pp. 250-261 (in Russian).

3. Kononov A. V., Sterlyn V. N., Edokymova L. Y. Fundamentals of complex fertilizer technology. Moscow, Khimiya Publ., 1988. 320 p. (in Russian).

4. Lehr J. R. Crystallographic Properties of Fertilizer Compounds. Chemical engineering bulletin, 1967, no. 6, pp. 37.

5. Kolpakov V. M., Kochetova Y. M., Norov A. M., Sokolov V. V. Comparative analysis of properties of granular NPK-fertilizers obtained by various methods. Trudy NIUIF. T. 2 [Proceedings of the NIUIF. Vol. 2]. Vologda, Drevnosti severa Publ., 2019, pp. 191-199 (in Russian).

6. Dormeshkin O. B. Features of chemical transformations occurring at the stage of granulation and drying of complex fertilizers in the presence of KCl. Trudy BGTU. Ser. III. Khimiya i tekhnologiya neorganicheskikh veshchestv [Proceedings of BSTU. Series 3: Chemistry and Technology of Inorganic Substances], 2016, no. 3, pp. 54-59 (in Russian).

7. Dormeshkin O. B., Vorob'ev N. I., Cherches G. Kh., Hauryliuk A. N. Low-waste technology for producing new types of sulfur-containing complex NPKS fertilizers. Trudy BGTU. Ser. III. Khimiya i tekhnologiya neorganicheskikh veshchestv [Proceedings of BSTU. Series 3: Chemistry and Technology of Inorganic Substances], 2007, no. 15, pp. 3-8 (in Russian).

8. State Standard 20851.2-75. Phosphorus content determination methods. Moscow, State Committee for Standards of the USSR. Publ., 1983. 39 p. (in Russian).

9. State Standard 30181.4-94. Method for determining the mass fraction of amide nitrogen in complex fertilizers. Minsk, Belarusian State Institution of Standartization and Sertification Publ, 1996. 9 p. (in Russian).

10. State Standard 30181.5-94. Mineral fertilizers. Method for determining the mass fraction of amide nitrogen in complex fertilizers. Minsk, Belarusian State Institution of Standartization and Sertification Publ., 1996. 5 p. (in Russian).

11. Kuvshinnikov I. M., Makarevich V. M., Levshina A. A., Osherovich R. Kh., Nepomnyashchaya N. A., Vinnik M. M. Methods of analysis of phosphate raw materials, phosphorus and complex fertilizers, feed phosphates. Moscow: Khimiya Publ., 1975. 218 p. (in Russian).

12. State Standard 20851.3-75. Mineral fertilizers. Methods for the determination of potassium content. Moscow, Standards Publishing House, 1983. 22 p. (in Russian).

13. Kreshkov A. P. Fundamentals of Analytical Chemistry. Moscow, Goskhimizdat Publ., 1961. 635 p. (in Russian).

14. State Standard 21560.1-82 - 21560.3-82. Mineral fertilizers. Test methods. Moscow, USSR State Comission for Standartization Publ., 1985. 19 p. (in Russian).

15. Dormeshkin O. B., Vorob'ev N. I., Cherches G. Kh., Gavrilyuk A. N. Study of the composition of products of JSC “Gomel Chemical Plant” exported to the EU countries and subject to registration in accordance with the REACH regulation. Trudy BGTU. Ser. III. Khimiya i tekhnologiya neorganicheskikh veshchestv [Proceedings of BSTU. Series 3: Chemistry and Technology of Inorganic Substances], 2009, no. 17, pp. 92-97 (in Russian).

16. Kolpakov V. M., Kochetova I. M., Norov A. M., Sokolov V. V. Comparative analysis of the properties of granular NPK-fertilizers obtained by various methods. Trudy NIUIF. T. 2 [Proceedings of the NIUIF. Vol. 2]. Vologda, Drevnosti sev-era Publ., 2019, pp. 191-199 (in Russian).

17. Gorbovsky K. G., Norov A. M., Kochetova I. M. Study of structural and mechanical properties of granules of mineral fertilizers. Trudy NIUIF. T. 2 [Proceedings of the NIUIF. Vol. 2]. Vologda, Drevnosti severa Publ., 2019, pp. 213-222 (in Russian).

18. Ando J., Akijama T., Morita M. Magnesium Ammonium Phosphates, Related Salts and Their Behavior in Compound Fertilizers. Bulletin of the Chemical Society of Japan, 1968, vol. 41, no. 7, pp. 1716-1723. https://doi.org/10.1246/bcsj.41.1716

19. Silverberg J., Lehr J. R., Hoffmeister G. Fertilizer caking, microscopic study of the mechanism of caking and its prevention in some granular fertilizers. Journal of Agricultural and Food Chemistry, 1958, vol. 6, no. 6, pp. 442-448. https://doi.org/10.1021/jf60088a00120

20. Tereshchenko A. G. Hygroscopicity and caking of soluble substances. Tomsk, Tomsk Polytechnic University Publishing House, 2011. 79 p. (in Russian).