Solid-liquid equilibrium of water-soluble ammonium polyphosphate-urea ammonium nitrate-potassium chloride system at 5 °C.

The solid-liquid equilibrium data of APP (ammonium polyphosphate, 18-58-0)-[CO(NH2)2-NH4NO3]-KCl-H2O system and its subsystems (APP(18-58-0)-[CO(NH2)2-NH4NO3]-H2O, KCl-[CO (NH2)2-NH4NO3]-H2O, APP(18-58-0)-KCl-H2O) at 5 °C were respectively determined by the dynamic method. The phase composition of the equilibrium solid phase was analyzed by XRD. The results show that the APP(18-58-0)-[CO (NH2)2-NH4NO3]-H2O, KCl-[CO (NH2) 2-NH4NO3]-H2O and APP (18-58-0)-KCl-H2O systems respectively contain two single crystal-phase regions [(NH4)3HP2O7, (NH4)4P2O7; KNO3, KCl; (NH4) 3HP2 O7, KCl], a co-satUrated crystalline region [(NH4) 3HP2O7 + (NH4) 4P2O7; KNO3 + KCl; (NH4)3HP2O7 + KCl]. APP( 18-58-0)-[CO( NH2)2-NH4NO3] -KCl-H2O system contains four single crystal regions of (NH4) 3HP2OC, (NH4)4P2O7, KNO3 and KCl. The maximum and minimum contents of N + P2O5 + K2O content in this system were 46.18%, 14.46% . With the increase of solutes in the APP(18-58-0)-[CO(NH2)2-NH4NO3]-KCl-H2O system, the content of water in saturated solution decreased gradually. The change trend of water content is consequently opposite to that of N + P2O5 + K2O content. However, the density is consistent with the evolution of N + P2O5 + K2O content. The obtained results provide reference value for the preparation of liquid fertilizer with different proportions of NPK. [ABSTRACT FROM AUTHOR]