Mathematical modeling of the equilibrium between nitrogen(II) and (IV) oxides in the combined process of metals extraction from the spent catalysts

Abstract

The paper gives the results of the study of equilibrium between nitrogen(II) and (IV) oxides under the conditions of the combined process of nitrogen oxides chemisorption from their mixtures with air and the extraction of metals from spent catalysts by an aqueous solution that contacts with the catalyst and the extractant. The mechanism of the combined process was established and the mathematical model was created that takes into account the interaction between nitrogen oxides and water with the formation of nitric acid, its subsequent interaction with the reactive component of the spent catalyst and the extraction of the formed metal nitrates. The investigation was performed and the mathematical model was developed for the determination of the equilibrium composition of nitrogen oxides in the production of nitric acid and the calculation of the equilibrium concentration and conversion degree of nitrogen oxides in the combined process. DIAP-3-6N catalyst was used as an example and the algorithm was proposed for the calculation of the time variation of the composition of a three-phase system "solid–liquid–gas". A mathematical model of the process was created that takes into account the dependence of the equilibrium conversion degree of nitrogen oxides on the consumption rate of the produced nitric acid in the extraction of metals from the catalyst.