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Show -12- dependent. This was a consequence of velocity m~x~ng scaling being used, since these were the factors relevant for NOx production. In FCT' s experience HCN is not seen outside the flame envelope unless there is severe flame quenching. This is very unlikely in high temperature rotary kilns so HCN emissions should be zero. Changing to low NOx burners would be expected to result in a small increase in CO and unburnt hydrocarbon emissions. 4. CONCLUSIONS 1. The current NOx emissions of the production kilns studied correlate well with the CEMFLAM results for the mono-channel burner extrapolated to the higher levels of primary air used. 2. The above correlation gives a high degree of confidence that the CEMFLAM results can be used to predict the NOx emissions of kilns but it does not represent a true validation of the CEMFLAM results. 3. A substantial reduction in NOx emissions in the order of 35% to 65% could be achieved by installing a multi-channel burner together with an indirect firing system on the kilns studied. 4. Change of fuel to gas firing is unlikely to make possible any further reduction in NOx emissions compared with a solid fuel low NOx burner, but the use of high volatile coal may improve emissions slightly. REFERENCES 1. Zeldovich, Y.B., Sadovnikov, P.Y. and Frank-Kamenetski, D.A., Oxidation of Nitrogen in Combustion (Translated by M. Shelef), Academy of Sciences of USSR, 1947. 2. Janaf Thermochemical Tables (2nd Ed) DOW Chemical Company, Washington, 1971. 3. Jungten, H., Coal Characterisation in Relation to Coal Combustion. Erdol und Kohle - Erdgas - Petrochemie Vol. 40, 204, 1987. |