| Nitrogen oxides produced by coal-fired boilers leads to serious environmental pollution ,and slagging problem in boilers strongly influences the operation security and economy. Numerical studies were carried out towards these problems in this paper.Based on commercial CFD software, a numerical model of a 300MW utility boiler was set up to study the combustion behavior and pollutant emission of coal blends. Different factors influencing NO_x emissions were studied, turns out excess air ratio is the most important factor, amount of SOFA, coal type and pulverizer position also influence NO_x emission.Then a numerical model coupled with the combustion code to predict ash deposition was developed. Simulation results show serious slagging is mainly on 20 to 25 meter height of the front wall, because of the more rapid gas flow and higher temperature, and burning Shenmu coal will result in more slagging than Zibo coal. The predictions indicate slagging can be alleviated by proper operating conditions and using low slagging-tendency coals. |
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