Optimising liquid potassium fertiliser composition
N. S. KISTANOVA1, O. S. KUDRYASHOVA2, YU. A. CHISTINA1
1Perm State National Research University, Perm, Russia
2Perm State National Research University, Natural Science Institute, Perm, Russia
Keywords: liquid fertilisers, potassium nitrate, potassium dihydrophosphate, potassium sulphate, potassium chloride, phase diagrams
Abstract
When formulating liquid fertilisers, a key challenge is identifying the highest possible concentration of components in the solution, as this affects storage and transportation conditions, usage guidelines, and pricing. A method for optimisation of the compositions of liquid potassium fertilisers using phase diagrams of polycomponent water-salt systems formed by KNO3, KH2PO4, KCl and K2SO4 has been proposed and implemented. Optimisation criterion was chosen to be solution concentration and the specific combination of salts that enable the production of the most concentrated fertiliser with a specific N : P2O5 : K2O ratio. The diagrams facilitate the determination of the liquid fertiliser composition to fall within the homogeneous region, thereby ensuring its stability throughout the shelf life. Experimental findings regarding the solubility of salts in the systems KNO3-KH2PO4-KСl-H2O, KNO3-KH2PO4-K2SO4-H2O, KCl-KH2PO4-K2SO4-H2O, KСl-K2SO4-KNO3-H2O and KCl-KH2PO4-KNO3-K2SO4-H2O at 25 °C are presented. The composition of saturated solutions for various combinations of salts was determined. Analysis of the acquired data indicates that the maximum saturation level (37.1 wt% of salts) corresponds to the solution that is saturated with nitrate, dihydrogen phosphate, and potassium chloride. A methodology for calculating the composition of a saturated solution with a given ratio of N : P2O5 : K2O is proposed and theoretically validated.
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