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In the previous work, a new NOx prediction model for pulverized coal combustion has been developed; the concentrations of CO and H2 were used to represent the fraction of CHi to quantitatively describe NOx gas phase reduction; by making codes, the new NOx model and char burning model considering gasification reactions were implemented with Fluent. Based on this, a drop tube furnace (DTF) and a one-dimensional furnace were updated and the combustion experiments of different coals under different conditions were conducted to collect experimental data of high quality. The parameter database of the new NOx model was built via the simulations of such basic experiments. Finally, the developed NOx model was successfully applied in the CFD simulations of tangential fired boiler, opposed firing boiler and W shaped flame boiler. Simulation results of three types of boilers under different operational conditions indicate that the new NOx model is able to accurately simulate the effects of different coals, different boiler types and different operational conditions on NOx evolution. This work provides a model basis for the further design, modification and optimization of low NOx burner and boiler. [ABSTRACT FROM AUTHOR]

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 H2O 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 updated 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. [ABSTRACT FROM AUTHOR]