NOx Abatement is a Non-Selective Catalytic Reduction (NSCR) technology that has a long and proven track record for controlling NOx emissions from nitric acid manufacturing plants. It can be used to alter the NO to NO2 balance (decolourization) or to eliminate NOx through catalytic reaction with a fuel as a reductant.
Nitric Acid Production
The first part of the nitric acid process involves the reaction of ammonia and air under pressure over rhodium-platinum gauze to give nitric oxide:
After the process gases have been cooled in a series of heat exchangers, boilers and steam super-heaters, they pass into an oxidizing adsorption tower where, with air and water, they react to form nitrogen dioxide and subsequently nitric acid.
The residual nitric oxide is, in practice, re-oxidized to nitrogen dioxide for further conversion to nitric acid. There is an economic limit to the size of the absorption tower that is practical and the adsorption efficiency achieved is generally in the range 98.2 to 99.3%. It is the residual concentrations of nitrogen dioxide and nitric oxide (commonly referred to as NOx) that give rise to the pollution problem in the vent stack.