Research On Primaryair And Secondaryair Parameters In A 600MWe Supercritical Dowm-Fired Boiler

At present the low quality and low volatile coal occupied 40% of the total coals for electricity generation in China, so the down fire boiler which burning hard-to-burn coals has its unique advantages and develop rapidly in China. The MBEL technology down fire boiler which adopting direct flow split burners as one of the genre, in the actual operation exist unstable combustion, high carbon content in fly ash and high NOx emission. For the MBEL technology W-shaped flame boiler' problem, the Institute of combustion Engineering of Harbin Institute of Technology raises a new combustion technology——multi-stage combustion with multi-ejection, and has been applied in the 600MWe supercritical down fire boiler. To the boiler as the prototype, build the coal modeling test-bed with the ratio of 1:20.6. Used the constant-temperature anemometer system and in different conditions to research the aerodynamic field in the furnace.Under the experimental conditions of the tertiary air angle is 45°and the proportion of the fuel-rich flow and fuel-lean flow is 4:6, when the ratio of tertiary air is 0% and 35%, in the furnace center, the upward flow deflect to the front wall, the dimensionless vertical speed, turbulence intensity and the downward airflow's dimensionless penetrating depth which on the tertiary air nozzle center plane of the furnace wall distribute asymmetric; When the ratio of tertiary air is 10%, 20% and 25%, the flow field is symmetrical, but when the ratio of tertiary air is 10% and 20%, the dimensionless penetrating depth of rear wall is too large, easily to cause slag on the hopper, when the ratio of tertiary air is 25%, the downward airflow of furnace wall penetrate moderate and the symmetry is good. In considering the flow field and appropriate airflow reach, hopper slag, the downward airflow of furnace wall's penetrate distance and the symmetry, an optimal rate setting of the tertiary air was 25%.Under the experimental conditions of the ratio of tertiary air is 25% and the proportion of the fuel-rich flow and fuel-lean flow is 4:6, when the tertiary air angle is 0°and 50°, in the furnace center, the upward flow deflect to the front wall, the dimensionless vertical speed, turbulence intensity and the downward airflow's dimensionless penetrating depth distribute asymmetric, and the penetrate depth is too shallow when the tertiary air angle is 0°, resulting in waste the hopper space. When the tertiary air angle is 15°, 30°, 40°and 45°, the deflection phenomenon of the flow field disappeared basically, the flow field in the furnace form a"W", but when the tertiary air angle is 15°, 30°and 40°, the furnace wall penetrate depth and symmetry can not compare with 45°. In considering the flow field, penetrate depth and the symmetry, an optimal angle of the tertiary air was 45°.Under the experimental conditions of the tertiary air angle is 45°and the ratio of tertiary air is 25%, when the proportion of the fuel-rich flow and fuel-lean flow is 4:6 and 6:4, the flow field is symmetrical, but when the proportion of the fuel-rich flow and fuel-lean flow is 6:4, the downward airflow of rear wall sweep the wall slightly and the dimensionless penetrating depth of the front wall downward airflow is low in some sort;When the proportion of the fuel-rich flow and fuel-lean flow is 8:2 and 10:0, the flow field of the furnace deflect in evidence, the recirculation zone of front wall disappear under the squeeze of rear wall upward airflow, the dimensionless penetrating depth of the front wall downward airflow is low in some sort, otherwise exist the downward airflow sweep the wall, easily lead to the rear wall slagging when the boiler in operation. In considering the flow field, penetrate depth and the symmetry, the slag of wall, an optimal proportion of the fuel-rich flow and fuel-lean flow is 4:6.