Studies On Treatment Of Nitrogen Oxides Gases In Chemical Industry By Wet Process At Normal Pressure

In chemical industry, NOX gases are largely let off from nitric acid plants, oxalic acid plants, nitro amine plants, dynamite plants and other plants which manufacture or apply nitric acid, which not only waste useful resource, but also represents a serious hazard for the human being and ecosystem. As a result, considering social and economical benefit of the plants, studies on the treatment of nitrogen oxides by wet process at normal pressure appears to be an increasingly important theoretical and practical significance for the prevention of environmental pollutants.Nitrogen oxides can form nitric acid by absorption into water; reclaimed nitric acid can be used again by production shop, so nitrogen oxides absorption into water is the treatment technology which belongs to clean chemistry. But up to now, there is little theoretical guidance except for nitric acid manufacture model. Therefore, based on two-film theory, through the analysis of the absorption process, the mathematical model for nitrogen oxides from exhaust gases into nitric acid solution was established by the method of mass transfer velocity. Experimental validation showed that simulation results were consistent with experimental results. The model provides theoretical basis for absorption process design.In order to improve nitrogen oxides absorption effect, removal of nitrogen oxides with alkaline solutions in packed column was studied, the influence of absorbing agent concentration, spraying density, temperature, oxidativity on nitrogen oxides absorptivity were studied. The results showed that the optimum operating conditions were as follows: alkaline concentration 20~40g/L, spraying density 10~12m3/(m2·h), oxidativity of Nitrogen oxides 50%. The results provide credible parameters for improving absorptivity of nitrogen oxides. In addition, taking HNO3, H2O2 and KMnO4 as the oxidants, the method of oxidation-alkaline solutions absorption were investigated in this paper, the results showed that the absorptivity of NOX could enhance remarkably by using oxidants, and KMnO4 was the best of three oxidants, the absorptivity of nitrogen oxides can reach to 99%.The operational conditions of nitrogen oxides absorption into urea solutions were studied, the results showed that the optimum operational conditions were as follows: the concentration of urea solutions 10%, pH value 1～3, temperature 30℃, reaction time 10s. In order to enhance the effect of nitrogen oxides absorption, hydrogen...