Study On Reaction Mechanism And Mixing Characteristics Of SNCR Technique

Nitrogen oxides is one of the three most important pollutants discharged from coal power plant. As the national and local environmental policy strictened, post combustion NOx control technology becomes an obvious choice. The experiences of the development of NOx controlling technology abroad indicate that SNCR technique is low-cost, easily retrofitted and free of byproduct pollution. And SNCR technique is well suited for use in combination with other NOx reduction technologies. The performance and cost of SNCR make this technology attractive for developing countries. In China, the controlling strategy and technology for NOx starts relatively late, however, a economical and moderate controlling strategy is practical.The author regards that all three paths of NOx reduction in the process of coal combustion is realized eventually through the reactions between NO and the radical nitrogen species like NH₃,HCN to form benign N₂. Therewithal, we conduct flow reactor experiments on the reaction kinetics of NH₃/NO under various atmospheres. The scopes included NH₃/NO reaction under various O₂,CO,SO₂ concentration, various NSR(Normalized Stoichiometric Ratio), and various resident time.Afterward, 5 classdic kinetic mechanisms for selective noncatalytic NH₃/NO reactions were used to stimulate the reaction conditions in our flow reactor studies. Both the experiments and prediction indicated that the most NOx reduction was achieved under ultra low oxygen concentration. Staged combustion can supply the ideal atmosphere for SNCR. The combined technology is a promising development direction for SNCR.Sensitivity analysis was preformed to identify the most important reactions which have the most influence on the NO profile. From the mentioned most important reactions, we set up a 14 steps reduced mechanism, which can predict the experimental results well and is consist with the original complete model. The reduced model can later be used to combine with CFD software to simulate the actual boiler SNCR application.Various SNCR reagents like ammonia, urea and ammonium bicarbonate were tested to determine their characteristic of NOx reduction. Their cost and flexibility were also summarized to supply a comparision of the suitable SNCR reagents for real-scale application in China. Addition of sodium additives can broaden the temperature window and reduce the nitrous oxide emission. SNCR reagents were also added to the reburning pulverized coal to study the nitrogen component's effect on...