METHOD FOR REDUCING NOx DURING COMBUSTION OF COAL IN A BURNER BY OPTIMIZING COMBUSTION AIR FLOW

摘要

An initial coal feedstock comprised of primary or second coal is cleaned so as to reduce its ash content by at least about 20% in order to yield a refined coal product that produces fewer NOx emissions. The reduced NOx emissions result primarily from the ability to use less primary combustion air in order to maintain the pulverized refined coal in a suspended condition within the feeder pipes of a coal burner compared to the minimum quantity of air required to maintain pulverized coal from the initial coal feedstock in a suspended condition within the feeder pipes. Reducing the primary combustion air reduces the amount of oxygen in the primary combustion zone that would otherwise be available for converting fuel nitrogen into NOx. Instead, more of the fuel nitrogen is converted into N₂. Reducing the primary combustion air also reduces the temperature of the core flame, reducing thermal NOx formation. Increasing the amount of secondary and/or tertiary combustion air to compensate for the reduced primary combustion air results in an overall decrease in NOx formation, as thermal NOx formation is reduced as combustion is completed in the cooler secondary and/or tertiary combustion zones.