Modeling of pyrolysis of ammonium dinitramide sublimation products under low-pressure conditions

To clarify the kinetic mechanism proposed previously for the description of the chemical structure of ADN flame, the chemical processes in thermal decomposition products and ADN flame with a pressure of 10 torr and 3–40 atm were numerically simulated. Results of numerical simulation of pyrolysis of ADN sublimation products in a flow reactor in a temperature range of 373–920 K for a pressure of 10 torr are presented. Specific features of numerical simulation of NH$_3$ reaction with HN(NO$_2$)$_2$ under conditions of high temperatures and low pressures and the reasons for significant differences in results calculated with the use of known one-dimensional models are discussed. A technique is proposed, which allows adaptation of one-dimensional numerical algorithms to fast processes and qualitative estimation of the contribution of the heating zone to chemical processes. Based on a comparison of numerical and experimental data, the contributions of individual stages and components to the pyrolysis process and the values of rate constants are estimated. A conclusion is made that the ADN sublimation process follows the dissociative mechanism: ADN$_c$ $\to$ NH$_3$ + HN(NO$_2$)$_2$.