Process for the synthesis of ammonium nitrite

Abstract

Ammonium nitrite is commercially produced by contacting a gaseous stream containing nitric oxide, nitrogen dioxide, nitrogen and oxygen with an aqueous solution containing a basically reacting ammonium compound in an absorption system. However, at normal production rates, serious problems have been encountered because of relatively low yield of ammonium nitrite and the emission of unreacted nitric oxide which causes pollution of the atmosphere. It has now been found that in situ generation of nitrogen dioxide in the absorption system by operating the absorption system under slight pressure greatly improves ammonium nitrite yield, reduces nitrogen oxide emission, reduces loss of ammonia as nitrogen and minimizes mist formation in the vent gas. Moreover, with respect to environmental pollution, we have discovered that a synergistic improvement results from an interaction effect involving use of said sight pressure in combination with late addition of controlled supplemental quantities of nitrogen dioxide to the nitrogen oxide gas while said gas is being absorbed in the absorption system.