Кинетика нейтрализации азотно-кислотного раствора, полученного из низкосортного фосфорсодержащего сырья

Abstract

This work is devoted to the kinetics of the neutralization process of an acid solution obtained by decomposition of the phosphate glauconite concentrate from the Novo-Amvrosievsky deposit (Ukraine) with the use of nitric acid. The direction of the reactions and the nature of the reaction products depend on the concentration of the mixture components, the value of pH of the medium and the temperature. Ammonia neutralization of the nitric acid solution (NAS) reduces the molar ratio of CaO/P₂O₅ which ensures the production of water-soluble ammonium phosphates. The main reactions in the NAS–NH₃–H₂O–H₂O system are revealed with due regard for the equilibrium in aqueous solutions H₃PO₄, NH₃·H₂O etc. The influence of pH and the protonation degree of phosphate ions on the composition of products and the reception of digestible forms of fertilizers are determined. The reaction time for the neutralization of nitric acid solution is established. The reaction time should be 20–25 min to achieve a pH value of about 4–5. A kinetic model of the process of the neutralization of nitric acid solution is developed. The model was proposed in the form of a system of algebraic equations that describes the chemical interactions in the course of the neutralization reactions; the rate constants of reactions occurring in various directions are determined. The obtained kinetic model is confirmed by experimental data and can be recommended for computation of the process of the neutralization of nitric acid solution in the following ranges of technological parameters: Ñ(NH₃·H₂O)=2–5, T=60–800Ñ, Re=250–350.