Effect of Fuel Composition on Emissions from Ultra Low NOx Burners

Process heaters in refineries and chemical plants utilize a wide variety of waste gases as fuels. These waste gases come from several sources at each plant and can continuously vary in composition and flow rate. The waste gases generally contain various concentrations of hydrocarbons ranging from C1 to C6, hydrogen and possibly inerts such as nitrogen and carbon dioxide. The individual waste gas streams are typically blended together with natural gas into one or more fuel gas systems and distributed to the furnaces. The fuel gas composition has a significant effect on burner performance because it directly affects the temperatures in the flame zone. The effects of fuel composition on NOx emissions has been evaluated for each generation of low NOx burners as they have been developed. The current generation of ultra low NOx (less than 30 ppm) burners has exhibited NOx emission relations with fuel composition that differ from the trends seen with previous low NOx burner designs. Several ultra low NOx burners of differing designs have been tested with a variety of fuel mixtures. This new data provides additional insights regarding the relative importance of various NOx formation mechanisms for these burners.