Abstract:

The NOx emissions of the double tangential firing boiler in 1 000 MW ultra-supercritical unit are systematically investigated based on on-site combustion tuning tests, on which the effects of excess oxygen level, boiler load, quantities of over-fired airs, burner air amount and distribution of the main combustion zone, mill groups in service, burner tilting angle, and coal property are studied. For the boiler equipped with advanced low-NOx combustion system, it is shown from the tests that the coal property, excess oxygen level and boiler load are important factors affecting NOx emission. The NOx emission increases linearly with increasing oxygen level. However, the burner air amount and distribution of the main combustion zone have weak influences on NOx emission concentration when multi-level combustion is achieved by keeping large quantity of over-fired airs. Based on this, the empirical correlations between NOx emission concentration and main operation factors are established by multiple linear regression, which can be applied to predict the boiler NOx emissions and guide NOx combustion control during operation.