Analysis on the Influence of Coal Properties on NOx Emissions of Large-Scale Boilers Equipped with Advanced Low-NOx Combustion Systems

The fast development and application of low-NOx combustion technologies have significantly influence on the operation performance of coal-fired utility boilers. With the application of advanced low-NOx combustion technologies, the characteristics of NOx emissions from pulverized coal-fired furnace and the trends of various factors influencing on the emissions may also be different from understandings from the experiences of using the previous technologies. It is well known that coal properties are among the most important factors to affect NOx emission levels. However, the modern low NOx combustion technologies are all based on controlling coal particle combustion process but fitting with the properties of the fired coals. Therefore, the influence of coal properties on NOx emissions of modern large-scale boilers, particularly those equipped with advanced low-NOx combustion systems, is worthy of a further study.

In the present work, extensive in-situ measured NOx emission data as well as coal properties of more than 40 pulverized coal- fired units with the installed capacity of 300–1,000 MW were collected and analyzed to establish the correlation between NOx emission and coal properties. When comparing the impacts of coal volatile content and N content on NOx emission concentrations between different boilers, it was found that, for the boilers burning high volatile bituminous coals, the impacts of coal properties on the NOx emissions of the boilers equipped with advanced low-NOx combustion systems are not long significant. When considering coal properties impact on a certain boiler equipped with advanced low-NOx combustion system, its NOx emission was found in general to decrease with the increases of the coal N and volatile contents. It implies that, for a certain boiler considered, coal properties are still the main factor influencing the NOx emission concentration. The present work presented the further understanding of the influence of coal quality on NOx emission of modern pulverized coal-fired boilers. The data and results will be detailed in the full manuscript.