Studies On Absorption Of Nitrogen Oxides

Nitrogen oxides (NO_x) are major air pollutants. The prensence of NOx in the atmosphere represents a serious hazard for the ecosystem. In this paper, several methods of removal of NO_x from exhust gases were reviewed; the current application, characteristics and existing problems of these methods were analyzed and the prospective trend of the removal of NOx were discussed also.The chemical equilibrium and reaction mechanism of absorption of NO_x exhaust gas into alkaline solutions in the packed column were researched, including chemical reaction in gas phase, mass transfer in gas phase, equilibrium in the gas-liquid interface, chemical reaction in liquid phase and so on. On the basis of above motioned theories, the mathematical model of NOx absorption in alkaline solution was put forward in this paper. The compositions of NO,NO₂,N₂O,N₂O₃,N₂O₄ and N₂O₅ were taken into account fully, and HNO₂ and HNO3 in the presence of water vapor was considered in this model.The operating conditions of NOx absorption into alkaline solutions was explored, the influences of temperature, airflow rate, oxidation ratio of NOx, concentration of absorbing agent and different packings on absoptivity of NOX were investigated.The experimental results showed that the absoptivity of NO_X decreased with the increase of temperature and the main absoption was happened in the entrance and foreside of the packed column; the optimum operating conditions was achieved, as follows: sodium hydroxide concentration was 3%, oxidation ratio of NOx was 50%, QL/QG was 30L/m3.