61. The Mechanisms and Applications of NO_x Reduction by Low-NO_x Burner Coupling Deep Air-Staging Technology in Pulverized Coal

In order to reduce the original NOx emission from coal combustion, and lighten the excessive redeucer used in the De-NOx post-treatment which will lead to the corrosion of steam heat exchanger tube and economical efficiency, a new De-NOx technology combined with the De-NOx combustor and the deep air stage combustion was developed, and the technology was testified by theory, numerical simulation, pilot experiment, and industrial experiment. FR/ED (Finite Rate/Eddy Dissipation) model which considering the chemical reactions involved in the gasification process is used in the simulation, and it showed a sufficient accuracy with the experiment results. A strong reductive atmosphere including CO and CH₄ was detected with a low stoichiometric ratio both by numerical simulation and experiment in a 7 MW double-cone De-NOx burner, the CO and H₂ contents could be 15.457% and 0.992 for SR of 0.456, respectively, while no NOx content was detected at the burner outlet. Method Oxygen-enriched air used in the burner could intensify the reductive atmosphere, and the CO content at the center burner increased form 9.54 to 20.258%, when the oxygen content increased from 21 to 28.3%. For the 7 MW pilot boiler system, the initial NOx emission of the boiler can reach to 159 mg/m³, and the total reduction of NOx generation was more than 70.9%, when the oxygen content in secondary air was 28.3% and the proportion of staged air in tertiary air was 41.2%. Utilization of De-NOx technology in long-term industrial experiment for 40t/h steam boiler showed near no influence on the boiler operation, original NOx of less than 200 mg could be reached at the extreme condition. When the original NOx emission reduced from 697 to 300 mg/m³, the heat loss was less than 0.5%, and more than 50% of ammonia water was saved for SCR, which leading about 1 yuan per ton steam saving of the cost.