Prediction of NOx during pulverized coal combustion:Model development and its implementation with Fluent

A new NOx prediction model for pulverized coal combustion was developed. Based on experimental data of different coals pyrolysis,the equation describing the distribution of fuel-N in volatile and char was proposed. To solve the quantitative description of NOx gas phase reduction,the concentrations of CO and H2 were used to represent the fraction of CHi species. Using “Define_DPM_LAW” macro in Fluent,the char gasification reactions with CO2 and H2 O were added to simulate the evolution of CO and H2 during the whole combustion process. The new NOx model was then implemented with Fluent by making user defined function (UDF) file to accomplish the coupling calculation of upda- ted NOx model with advanced turbulence model and radiation model. Comparing with the current models,the new NOx model can reasonably distinguish different NOx evolution characteristics with different conditions,regular combustion or air-staged combustion,which is helpful to justify the effect of different structure designs and operation conditions on NOx emission.