Solid-liquid equilibrium in liquid compound fertilizers

Liquid compound fertilizers (LCF) are aqueous salt solutions which nourish the soil. They contain nitrogen, phosphorus, potassium, sometimes calcium, magnesium and micronutrients. An LCF solution has practically no insoluble residue and contains the elements in a fully digestible form and is a high-speed, highly effective fertilizer. It is important to assess the equilibrium in the solid-liquid system when creating liquid compound fertilizers, since their basic properties, concentration and crystallization temperature, depend on it. The aim of the study was to determine properties of a liquid multicomponent (K+, NH4 +, Cl- and PO4 3-) system. This liquid multicomponent system, which was obtained as a by-product in the conversion of KCl and NH4H2PO4, can be used as a liquid fertilizer. This work investigates liquid fertilizers’ chemical composition and their physicochemical properties, such as crystallization temperature, pH, density, viscosity and corrosivity. In order to increase nitrogen concentration, ammonium nitrate was added. Composition of the solid phase obtained by crystallization was identified by methods of chemical and instrumental analysis (radiography, infrared molecular absorption spectroscopy and optical microscopy). The results show that all properties of liquid fertilizers are best when the concentration of NH4NO3 in liquid solutions equals 8%