Iron ore sintering involves the movement of a flame front down a particulate bed, and a series of physico-chemical reactions over a large temperature range. In the literature simple and more sophisticated iron ore sintering models have been reported. In this paper a more comprehensive numerical model which incorporates most of the significant processes and heat transfer modes proposed in earlier models is given. Therefore, sub-models are available to describe the relationship between airflow rate through the bed and flame front speed, the evaporation and condensation of water ahead of the front, the calcination of fluxes nearer to the front, the reactions that occur in the front and cooling of the bed with the departure of the front. Improvements were made to several areas -such as coke combustion, and the melting and solidification processes -to more accurately quantify the phenomena involved. More recent progress in understanding the fundamentals of sintering from BHP Billiton studies have also been incorporated into the model. To date, twelve sinter pot tests have been used for validation studies. Reasonably good agreement was obtained between predicted and measured results -in areas such as bed temperature profiles and waste gas temperature and compositions. Work is continuing to further improve the model, and broaden the validation work to include other bed temperature profile parameters.

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Computational fluid dynamics (CFD) investigations have been carried out to understand the combustion and NO x emission characteristics in a 1000 MW pulverized-coal boiler, which is equipped with a dual-circular tangential-firing system in a single furnace. One group of separated over fire air (SOFA) nozzles has been widely studied and used in controlling the NO x emissions in a pulverized-coal boiler. In this work, a multi-group of SOFA nozzle arrangement is investigated for the NO x control and reduction. The predicted results agree well with the measured information from the full-scale boiler. The flow field, temperature distribution, species concentration, and char burnout are discussed. The relationship between the NO x formation and the SOFA arrangement are analyzed. The numerical results show that the multi-group of SOFA nozzle arrangement is an efficient method to control the NO x emissions in the pulverized-coal boiler, with few unfavorable effects on the coal burnout. The arrangement of the two-group of SOFA nozzles being in service presents better ability than the one-group arrangement in reducing the NO x emissions. The distance between the two groups of the SOFA nozzles should be longer for a better result of NO x reduction. The technology of air-staging combustion presented in this work is good to enhance the understanding of the NO x formation characteristics and useful for the NO x control and reduction in pulverized-coal boilers.

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A new numerical iron ore sintering model was developed recently. It takes into account most of the significant physico-chemical processes in sintering. In this study results from the model are compared with experimental results from twenty five sinter pot tests. Results indicate that the model can simulate the iron ore sintering process, as reasonable correlations between predicted and measured results were obtained in many areas. The good comparisons also indicate that the key sub-models, which have significant effects on results, viz., coke combustion, fluxes calcination, drying and condensation as well as heat and mass transfer, describe the sub-processes well. The phenomena of steady-state waste gas composition (SSWGC) and steady-state waste gas temperature (SSWGT) were simulated and analyzed by the model. A total of nine important input variables were identified and their influence on sintering time and three critical parameters which determine heat transfer during sintering were considered in the sensitivity studies. Results showed that bed bulk density, solid and gas thermal capacities, coke level and diameter and post-ignition airflow rate have the greatest influences on sintering time and the temperature profile parameters. This paper also gives suggestions on how the model can be improved.