Process Intensification of Absorption of Nitrogen Oxides in the Manufacturing of Nitric Acid and Techno-economic Assessment: Use of Ozone

In the manufacturing of nitric acid, the absorption column occupies the dominant place. The NO oxidation rate falls when NO concentration goes below 5000 ppm, making it difficult to meet stringent norms for NOX at the outlet. Nitric oxide and ozone react instantaneously to give NO2, and NO2 reacts with ozone to give N2O5, which has the highest solubility in water among the nitrogen oxides. When ozone is introduced, the gas phase mass transfer of N2O5 becomes the rate-controlling step instead of NO oxidation when using air. N2O5 reacts with water to give nitric acid as the product. The current work has investigated the techno-economic advantage of ozone in nitric acid manufacturing. The use of ozone has the benefits of (a) the size reduction of the absorption column, (b) the possible elimination of pollution control systems, and (c) the recovery of practically all the reactive nitrogen to nitric acid and reduction in the NOX emissions.