NOx CONTROL

The major contributors to NOx emissions are thermal NOx and, if fuel bound nitrogen is present, fuel NOx. Most refinery process heaters in the US are fueled by refinery fuel gas and, thus, thermal NOx is the primary concern. As noted previously, thermal NOx is strongly influenced by peak flame temperatures and the key to controlling thermal NOx is to moderate peak flame temperatures.

Historically, thermal NOx control techniques have included excess air control, air or fuel combustion staging and flue gas recirculation. Low excess air operation provides only limited benefit. However, it is compatible with, and can be used together with, most of the other NOx control techniques. Combustion staging and flue gas recirculation have proven to be more beneficial. The combination of fuel staging and flue gas recirculation has proven to be the most beneficial combination until recent developments. Low NOx industrial burners have been developed utilizing these NOx control techniques