| With the increasingly serious environmental problems, it is becoming more important to reduce NO_x emissions, enhance the adaptability of coal variety, and prevent slagging in furnace to ensure the safety and stability of boiler units adopting swirl coal combustion techniques. In view of this, studies are conducted on central-fuel-rich swirl coal combustion burner with bituminous and double-swirl flow burner designed by Ishikawajima-Harima Heavy Industries (IHI) Co., Ltd in Japanese. The mechanisms of two swirl burners are revealed through Single phase experiments, smog tracer tests, gas-particle two phase experiments and numerical simulation, while industrial tests are carried out simultaneously to study the characteristics of combustion and NO_x emissions of them.An IFA300 constant-temperature hot-film anemometer system is used to study flow characteristics at the nozzle region of central-fuel-rich and IHI double-swirl flow burner. The three-dimension flow field and turbulence intensity distribution at the nozzle region are investigated concerning with different structures and operational parameters.Through thermal transfer analogy and visualization used for the research on mixing characteristics of primary air and secondary air of central-fuel-rich burner, we obtain the mixing characteristics and the correlations between fractal dimension and turbulence intensity at the boundary of the primary air in different structures and operation parameters.A three-dimensional particle-dynamics anemometer (PDA) system is used to study gas-particle flow characteristics of central-fuel-rich burner with different secondary air flux, tangential vane angles and ratios of inner/outer secondary air. The particle diameter, altoge ther with volume flux and relative number concentration, are comparatively large in the central region outside the burner nozzle.The influence of outer secondary air vane angles on the gas-particle flow characteristics of IHI double-swirl flow burner are investigated by the three-dimensional PDA system. The IHI double-swirl flow burner has a small ring recirculation zone near the burner nozzle. And there are two peak values of particle volume flux and particle relative number concentration in the secondary air region and near-wall region while the particles in the center of burner are small.As to the conditions and parameters of the PDA experiments, Realizable k-εmodel and Lagrangian stochastic trajectory model are used in the numerical simulation of gas-particle flow characteristics at the nozzle region of central-fuel-rich burner. The simulation results and experiments data coincide well.Both cold air flow experiments and industrial tests are conducted in a 1025 t/h, bituminous fired boiler before and after 8 burners at the bottom row are retrofitted to the central-fuel-rich burners. Gas temperature, gas composition and char burnout are measured in the burner region. For the boiler with enhanced ignition-dual register burners before the retrofit, coal combustion efficiency is 96.73% and the NO_x emission is 843.55mg/m~3 (O2=6%) while the lowest load without auxiliary oil is 180 MWe under the condition of stable operation. After central-fuel-rich burners are adopted, coal combustion efficiency increases to 97.09% and the NO_x emission decreases to 727.67mg/m~3 (O2=6%) , while the boiler could be operated stably at a load of 110 MWe without auxiliary oil.Industrial tests are also conducted in a 670 t/h, bituminous fired boiler which adopts the IHI double-swirl flow burners. Gas temperature, gas composition and char burnout in the burning region are measured under different loads, over-fire air damper openings and outer secondary air vane angles, as well as the furnace temperature distribution, heat flux distribution, NO_x emission and boiler efficiency.
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