Abstract: A method for the removal of nitrogen oxides from the off-gases of a nitric acid manufacturing facility. The off-gases containing the nitrogen oxides are first contacted at atmospheric pressure and at a temperature below about 90.degree. F with a countercurrently flowing stream of about 10 to about 35% by weight nitric acid to absorb the nitrogen oxides. The rate of flow of the nitric acid is controlled so that the partial pressure of the nitrogen oxides absorbed in the nitric acid is lower than the partial pressure of the nitrogen oxides in the off-gas feed stream. The nitric acid containing the absorbed nitrogen oxides is then countercurrently contacted with a small amount of air at a temperature between about 60.degree. and about 120.degree. F to liberate the absorbed nitrogen oxides so that they can be returned to the reactor section of a nitric acid plant. The nitric acid being recycled to absorb more nitrogen oxides.

Abstract: A process for the preparation of nitric acid from nitrogen oxides, oxygen and water which utilizes an aqueous stripping liquid having a nitric acid content within a specified range which passes through a reaction zone. By controlling the process parameters within specified ranges three regions are provided with the reaction zone.

Abstract: DISCLOSED IS A TWO STAGE process AND APPARATUS for preparation of NITRIC AICD characterized by efficient use of heat liberated by the conversion of NITROGEN OXIDES TO NITRIC ACID.