Supercritical water oxidation of ammonia with methanol as the auxiliary fuel: Comparing with isopropanol

The co-oxidation behavior of methanol on ammonia in supercritical water was investigated in a continuous tubular reactor under a range of methanol concentration (10-800 mmol/L), ammonia concentration (50-400 mmol/L), oxidation coefficient (1.05-1.7) and preheating temperature of 400 and 415 degrees C. Calculation based on a mechanism-based model for supercritical water oxidation of methanol/ammonia showed that the synergy between the kinetics action to supply radicals and the thermal action to elevate the reaction temperature of methanol would improve the efficient decomposition of ammonia at relatively moderate reaction conditions. Specifically, near complete conversion of ammonia (97.5%) can be achieved at [CH3OH](0) = 800 mmol/L, preheating temperature of 415 degrees C and oxidation coefficient of 1.5. The influence of reaction conditions on the co-oxidation behavior and the formation of nitrate were examined experimentally. Methanol and isopropanol served as the auxiliary fuel for ammonia were compared by the positive effect and exothermic performance, which reached that methanol was superior to isopropanol. (C) 2019 Published by Elsevier B.V. on behalf of Institution of Chemical Engineers.