Improvements in or relating to the manufacture of dinitrogen tetroxide

摘要

Dinitrogen tetroxide is prepared by cooling a hot gas mixture containing NO to a temperature above its dew point, passing the cooled gas through a reactor in countercurrent to nitric acid, cooling the gaseous effluent to condense water and HNO3, and cooling the remaining gas to condense N2O4 from N2 and O2. Gas from the oxidation of NH3 with air at 900-1000 DEG C. is cooled in a waste heat boiler to 300-600 DEG C. and enters plate, or packed, tower reactor 4 at 2. The gas at 50-150 p.s.i.g. pressure flows up tower 4 countercurrent to 60-70% HNO3 entering at 6 at 0-100 DEG C. The effluent gas at not more than 120 DEG C. passes to water-cooled condenser 10 whence condensed HNO3 and H2O is returned through 12 to tower 4 as reflux. Remaining gas at 25-50 DEG C. passes to brine cooler 22, whence N2 and O2 is withdrawn at 28, while condensed N2O4 passes to receiver 26. The N2O4 passed to plate, or packed, distillation column 32, while 98% HNO3 is fed into the steam-heated still pot from 64 to ensure an acid concentration of at least 70% to prevent N2O3 formation during distillation. The effluent gas from column 32 passes to water-cooled condenser 36 whence part of the condensate is returned through 40 to column 32 as reflux, and the remainder is recovered through brine-cooled condenser 44 as N2O4 product. Remaining gas from condenser 36 is vented through brine-cooled condenser 48.