Abstract: The combination of centrally fuel rich swirl burners with over fire air technology formed a centrally fuel rich swirl burner with multi-stage combustion technology for getting higher efficiency and controlling NOx emission. The theory and characteristics of this technology is introduced and analyzed. This technology owns the following characters：Low NOx emission, high combustion efficiency, slagging resistance and high temperature corrosion resistance. Laboratory and Industrial experiments and tested the theory. Single-phase cold flow air experiments on a centrally fuel-rich swirl burner are carried out to investigate the influence of the over fire air ratios and the outer secondary air angle on the flow characteristics in the laboratory and real boiler. The results show that a stable central recirculation zone is formed when an over fire air ratio of 25% and the size of the zone increase with the angle decreasing. A three-component particle-dynamics anemometer is used to measure flow characteristics in the near-burner region in the laboratory. The result show that the peak value of the relative particle number locates the burner centerline. Measurements are taken for a 600 MW wall-fired pulverized-coal utility boiler that is retrofitted with centrally fuel rich swirl coal combustion burners and multi-stage combustion technology. The result show that the burner has good performance when a over fire ratio of 25%. Some applications are given.

Key words: boiler, centrally fuel rich swirl burner, low NOx emission, multi-stage