Air; Liquid ammonia

nitric acid

To produce nitric acid (80-99% HNO3) from ammonia and air using the SABAR process. Does not require oxygen, refrigeration energy, dehydrating agents (sulfuric acid or magnesium nitrate). Nitric oxides in the tail gas can be reduced by absorption to below 200 ppm. Weak acid at any rate and concentration can be produced simultaneously

Description: Gaseous ammonia is mixed with air and converted to nitric oxides in the reactor (1) on platinum-rhodium catalysts. Ammonia conversion is at atmospheric pressure so that the reaction water-most of which must be passed out of the process can be condensed with minimum absorption of nitric oxides. The atmospheric pressure conversion gives low platinum loss and a high yield. The reaction heat is used to produce steam and to preheat the tail gas prior to expansion. The reaction gases are finally cooled in the gas cooler condenser (2) where the main portion of the rection water is separated as 2% nitric acid condensate. After addition of secondary air which contains recycled nitrogen dioxide the nitrous gas is compressed (3) to between 6-13 bar abs.
   The compressed gas enters the chemical absorption column (4) where superazeotropic acid is formed. Nitrogen dioxide remaining in the gas is physically absorbed in nitric acid, which takes place in the physical absorption column (5). The nitric acid loaded with nitrogen dioxide flows to the desorption column (6) where the nitrogen dioxide is stripped by secondary air, which is recycled to the main gas stream ahead of the compressor. Tail gas from the physical absorption is freed (7) from nitric acid vapors, heated and expanded in the tail gas turbine.
   The superazeotropic acid is stripped (8) by secondary air to remove nitrogen dioxide and is sent to rectification (9) where it is separatd into high concentrated and azeotropic acid. The latter is recycled to the absorption section (5,4).

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