Abstract: A gas stream containing nitrogen oxides, such as the tail gas from a nitric acid plant, is treated to reduce the nitrogen oxides content thereof. The method results in the production of an aqueous solution of ammonium nitrate. In a liquid-gas contact apparatus, the gas stream is first reacted, under steady state conditions, in counter-current flow, with an aqueous solution of ammonium nitrate at a pH of about 0.01 to about 0.5. The gas stream is then further reacted with an aqueous solution of ammonium nitrate at a pH of about 8.1 to about 8.5; and thereafter with water, preferably slightly acidified to a pH of 6.0 to 6.5. The resulting gas stream of reduced nitrogen oxides content may be safely discharged to the atmosphere without causing air pollution, the nitrogen oxides content being below imposed standards.

Abstract: A gas stream containing nitrogen oxides, such as the tail gas from a nitric acid plant, is treated to reduce the nitrogen oxides content thereof. The method results in the production of an aqueous solution of ammonium nitrate. In a liquid-gas contact apparatus, the gas stream is reacted, under steady state conditions with an aqueous solution of ammonium nitrate at a pH of about 0.1 to about 3.5. The gas stream can be further reacted with an aqueous solution of ammonium nitrate at a pH of about 7.5 to about 8.5; and thereafter with water, preferably slightly acidified. The resulting gas stream of reduced nitrogen oxides content may be safely discharged to the atmosphere without causing air pollution, the nitrogen oxides content being below imposed standards.