Ostwald’s process produce nitric acid of 60% concentration using raw materials ammonia and air. In Ostwald process, 95%of ammonia is converted into nitric acid. To produce the 163 MTPD nitric acid, ammonia required is 1566 Nm3/hr and air 13500 Nm3/hr.
Three major steps considered in nitric acid manufacturing process flowsheet
- Ammonia splitting by oxidation to produce nitric oxide (adiabatic reactor)
- Nitric oxide oxidation to produce dinitrogen tetraoxide
- Dinitrogen tetraoxide absorption with water to produce nitric acid
Chemical reactions for each step:
- 4 NH3 + 5O2 → 4NO + 6H2O +216.7 kcal/mole
- 2NO + O2 → N2O4
- 3N2O4 + 2H2O → 4HNO3 + 2NO
Oxidation step mole balance around the converter of nitric acid manufacturing process flowsheet:
The above composition is taken as feed to the burner(converter) for 163 metric ton of nitric acid production in a day. Bases on the reactions the mass balance give the burner outlet composition if NH3 conversion is 95%.Oxidation of NO to NO2 occurs inside the burner around 4.6% of NO is being converted into NO2. Even a side reaction occurs to produce nitrogen from ammonia and this leads to increase nitrogen composition in the outlet.
Nitric acid manufacturing process flowsheet by Ostwald and Brauer Method