58 MW煤粉炉高效低氮燃烧研究OA

This study focuses on a 58 MW pulverized coal hot-water boiler to investigate the causes of high unburned carbon content in fly ash.Initial analysis supported by statistical data from the weigh hopper and boiler oxygen levels revealed that the average oxygen content was merely 2.7%.The standard deviation is 1.67 from 120 oxygen content samples indicated significant instability in pulverized coal delivery,leading to insufficient air distribution and oxygen-deficient combustion,which was identified as the primary cause of the high unburned carbon.Following the replace-ment of the feeder,the average flue gas oxygen content increased to 6.6%,with the standard deviation decreasing to 1.27 across 120 samples.This improvement in combustion stability resulted in a reduction of unburned carbon in fly ash to the range of 10%～15%.Building on this improvement and leveraging the characteristics of the swirl counter-flow burner,a strategy was proposed to enhance the mixing of combustible components and air within the furnace by introducing vertically injected tertiary and qua-ternary air streams into the flame.Numerical simulation was employed to study the effects of the ratio between tertiary and qua-ternary air on improving combustion efficiency and reducing nitrogen oxides(NOx).The simulation results demonstrated that the deployment of tertiary air increased the combus-tion efficiency to 99.76%,while NOx emissions were reduced from 581 mg/m3 to 547 mg/m3.The subsequent intro-duction of qua-ternary air further reduced the combustion efficiency to 99.23%and lowered NOx to 511 mg/m3.How-ever,when the qua-ternary air flow rate was increased from 17 900 m3/h to 19 094 m3/h,a trade-off was observed:while NOx emissions decreased further to 482 mg/m3,the combustion efficiency dropped to 98.75%.Finally,the boiler was retrofitted with the tertiary and qua-ternary air systems and operated under the optimized conditions(Oper-ating Condition 3).This implementation successfully reduced the unburned carbon in fly ash to below 5%with the in-itial NOx emissions maintained at approximately 500 mg/m3.