Kenichi Ochi

LES of Pulverized Coal Combustion Furnaces

LES (large eddy simulation) is applied to combustion simulations of two large scale pulverized coal-fired furnaces. One application is a boiler furnace with the coal feed rate of 3,000 kg/h. The results of LES show good agreement in not only distributions of temperature, NO concentration, and CO concentration on the vertical center line but also NO and CO emissions and UBC (unburned carbon in ash). The calculation error of NO emission is 10%. The other application is a horizontal furnace with a low NOx burner with the coal feed rate of 560 kg/h. LES predicts temperatures and oxygen concentrations accurately; but the standard k-e model does not. The flame width calculated by the standard k-e model is narrower than that by LES. These calculated results indicate that the drawback of the standard k-e model is its low calculation accuracy for the coal jet flame decay and lift-off height.Copyright

Modeling of NOx and CO Reactions for Commercial Scale Pulverized Coal Firing Boilers

The NOx-CO reaction model was developed for commercial scale pulverized coal firing boilers. The model was used to decide optimize combustion performance and it featured simplified sub models of NOx reduction, pyrolysis and CO oxidation. To improve combustion performance of commercial scale pulverized boilers, it is most important to predict the distribution of NOx and CO concentrations and search for the best conditions in a short time. The NOx reduction sub model was developed for both volatile and char combustion. The pyrolysis sub model was developed from a comparison of Distributed Activation Energy Model results and experimental data. The CO oxidation sub model was characterized by its consideration of the effect of hydroxide radicals. The simulation gave a lower CO oxidation rate for a long reaction time, the same as the actual result. The NOx-CO reaction model successfully analyzed NOx and CO concentration distributions of commercial scale boilers for power plants (260–1000MW).Copyright