Nitric acid manufacturing process flowsheet

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:

ComponentsINPUTINTERMEDIATEOUTPUT
KmolKmol%KmolKmol%KmolKmol%KmolKmol%
N2449.469.06449.4467.42449.4468.48451.12668.65
O2116.717.9437.055.5526.7274.1124.2123.68
H2O17.52.68113.07316.96113.07317.2118.099517.98
NH367.0710.323.3530.503.3530.5
NO63.71659.5543.076.5643.07066.55
NO220.6453.1520.6453.14
Total650.67100657.1531100

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
 Nitric acid manufacturing process development 2D drawing

Production of nitric acid from ammonia using catalytic oxidation