Thermal Hazards for Autocatalysis and Stability in CSTR: Decomposition of Solution from Nitrolysis of Hexamethylenetetramine

Abstract

AbstractNitrolysis solution is a kind of spent acid, obtained after the nitration and ripening of hexamethylenetetramine (HA). Its decomposition is generally spontaneous and hazardous. Therefore, the thermal hazards of a real nitrolysis solution were studied here. The prepared nitrolysis solution was analysed by isoperibolic experiments, differential thermal analysis (DTA), accelerating rate calorimetry (ARC), and a bursting point test. We employed non‐linear regression and ordinary differential equation (ODE) fitting methods to obtain kinetic parameters, such as 120.73 kJ mol−1 of the activation energy (E), 36.388 s−1 of the natural logarithm of the pre‐exponential factor (lnA), 1.155 of the reaction order, and 0.6615 of the catalytic index. Based on these kinetic parameters, thermal safety parameters were obtained to evaluate the hazards of a real nitrolysis solution from four aspects: severity, thermal stability, process hazards, and thermal sensitivity. The results indicate critical severity, high process hazards and thermal sensitivity, and very low thermal stability. The hazards due to real nitrolysis solution are higher than those of nitric ester explosives and azos. Further, the value of the initial mass ratio between the concentrated nitric acid and HA could severely pose safety risks during the nitration process. Additionally, the sensitivity analyses of the four process parameters (space‐time of CSTR, τCSTR; feeding temperature, T0; ambient temperature, Ta; specific cooling capacity, hS/V) were performed under the critical conditions for thermal stability in a continuous stirred tank reactor (CSTR). The suited margin of Ta could be 333.15–342.81 K with other determined process parameters.