Answer to Question #233520 in Chemical Engineering for Lokika

Question

Explain the production of nitric acid by ammonia oxidation process with a neat flow sheet.

Answer 1

This process utilizes a tail gas reactor installed after the absorber and before the tail gas expander (turbine). Improvements regarding reduction of the nitrogen oxide emissions can be realized by devising efficient catalysts for the decomposition of NO and N₂O. The best available technology (BAT) for tail gas treatment of nitric acid production is based on SCR and NSCR processes. It has the capacity to stay stable up to 600 C and are more environmentally friendly, since higher conversions can be achieved at the same reaction temperature and no toxic element such as vanadium can enter into the atmosphere. The recommended operation temperature range of the used commercial Fe-ZSM-5 catalyst (DeNOx) is between 200 • C and 520 • C, with the optimum decomposition temperature for both nitrogen oxides and dinitrogen oxide around 420 • C. The conversion rates are up to 98%. The V 2 O 5 /TiO 2 catalyst is a medium temperature-operating catalyst (300-450 • C), but the recommended temperature window is 300-400 • C, since above this temperature, the catalyst loses its selectivity. The flow chat below shows the process of nitric acid production through ammonium oxidation: