The efficient use of pulverized coal is crucial to the utility industries. The use of computational fluid dynamics (CFD)-based numerical models has an important role in the design of new boiler furnaces or in retrofitting situations. The results of CFD simulations can be used to better understand the complex processes occurring within the boiler furnace. The use of these results to support boiler operation and training of operators requires that the CFD models can be easily accessed and the results are easily analysed. This paper discusses two ways to simulate the heat transfer process in boiler furnaces. The method directly applying CFD results is employed, in which the grid for solving the energy equation is the same as the flow grid in the CFD simulation while radiation heat transfer is solved in another relatively coarse grid. Comparison of the prediction results between CFD and Heat Transfer code (Simple model) is performed under boiler full load (100%) with one side wall fouling, as well as for different boiler loads (100, 98 and 95 per cent boiler full load, respectively). Finally, the flexible use of the results of CFD and the simple model for pulverized coal-fired boilers is presented. To facilitate the use of the system, a user-friendly interface was developed which enables the user to manipulate new calculations and to view results, namely performing'what-if' analysis. Copyright ~ 2000 John Wiley & Sons, Ltd.

The mechanism of detailed chemical reactions in combustion is very complicated, especially when the formation of pollutant such as NOx is considered. Based on Glarborg's and Bilger's full model (Glarborg P. et al., Combustion and Flame, 65, 177; (1986), Bilger R. W., Starner S.H., Kee, R.J., Combustion and Flame, 80, 135 (1990)), a simplified model of the mechanism of NOx formation in a CH4/Air system is presented. Sensitivity calculation and eigenvalue-eigenvector analysis fprincipal component analysis (Vajda S., Valko P., Turanyi T., Int. J. Chemicaf Kinetics, 17: 55 (1985)) are used in the model. Compared with the conventional methods of simplification of chemical reaction mechanisms such as quasi. steady-state approximation, the eigenvalue-eigenvector analysis can indicate the important reactions efficiently without providing any balance hypothesis. The new model consists of only 15 elementary reactions, which is simpler than the full model composing 39 reactions. The deviations in NOx concentration and other major species between the simplified and the full model are rather small over a wide range of fuel-air ratio．Meanwhile, the calculated NOx concentrations by the simplified model are in quite good agreement with Bartok's experimental data (Bartok W. et al., AICHE Symp. Ser. 126 (1972)), especially in the fuel-lean region.

The mechanism of detailed chemical reactions in combustion is very complicated, especially when the formation of a pollutant such as NOx is considered. Based on regression analysis, a simplified fuel-NOx model is developed for premixed flame. The new model iS available for a wider range of temeperature and fuel-air ratios compared with De Soete's (1975) fuel NO model. The reduction CHi species on NO iS considered so that the model can be used in both fuel-lean and fuel-rich combustion systems. After a great simulation of a one-dimensional premixed flame system using Miller and Bowman'S (1989, Prog. Energy Combust. Sci., 15, 287) detailed elementary reaction model, the calculation of all the reaction rates is presented based on regression analysis.Copyright