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Show There is also considerable improvement in NO predictions when applied to the no coal spreader case, while the results for the FSR bumer show some improvement. It is interesting that for this case, and the basline case, the modelled and predicted values have similar shapes (two peaks). For the current case, the first peak has become larger and doser to the fumace wall. A possible explanation is that the hydrocarbon reburn mechanism is incorrectly converting NO in the fuel rich region to HCN, which is then reoxidized to NO. CONCLUSIONS 1. There is reasonable agreement between the predicted and measured oxygen concentrations; but there is an apparent overprediction of peak gas temperatures by up to 200 K along the axial centreline of the bumer. 2. With HCN taken as the only primary nitrogenous volatile product (the baseline model), both the local and overall predictions of NO concentrations are good. 3. When ammonia chemistry is added to the baseline NOx model, the NO concentrations are overpredicted. 4. Inclusion into the baseline NOx chemistry of both the hydrocarbon rebum mechanism and ammonia as a NOx precursor improves NO predictions. REFERENCES 1. Mereb, J.B., and Wendt, J.O.L., Air staging and rebuming mechanisms for NOx abatement in a laboratory coal combustor, Fuel, 1994, Vol. 73,1020-1026 2. Wendt, J.D.L., Mechanisms goveming the formation and destruction of NOx and other nitrogenous species in coal combustion systems, Second International Conference on Combustion Technologies for a Clean Environment, Calouste Gulbenkian Foundation, Lisbon, Portugal, 1993, 1-12 17 |