Multistage-optimized kinetics-diffusion modeling for solid-liquid denitrification: From predictive control to model validation

To analyze the effects of temperature, concentration, and reaction time on the denitration rate of double based spherical gun propellant (DBSGP) and to investigate the denitration reaction-diffusion coupling process for achieving precise denitration rate prediction, experiments measuring denitrification rates were conducted using the “one-pot method” and “crossing-method,” reducing experimental system errors and the number of trials under different reaction parameters. Concurrently, the denitrification mechanisms of different energy-containing components within DBSGP were compared. Results indicate that nitrocellulose reacts exclusively with hydrazine hydrate, whereas nitroglycerin and triethylene glycol dinitrate undergo parallel hydrolysis reactions with hydroxide ions. Based on this, the shrinking core model was employed to fit experimental data, confirming that chemical reactions dominate within the initial 100 min. At 80 °C, the denitration process transitioned to an internal diffusion-controlled stage after 150, 120, and 100 min when hydrazine hydrate concentrations were 7.5 %, 10 %, and 12.5 %, respectively. Based on the multi-stage coupling concept, the subsequently established reaction-diffusion coupled prediction model achieved a relative prediction error δ below 10 % at 70–80 °C and below 25 % at 50–60 °C. When concentrations varied, 79 % of the unperturbed samples exhibited δ values less than 10 %. This study provides a methodology for modeling solid-liquid non-catalytic systems which exhibiting reaction-diffusion coupling characteristics.