Development of a Low NOx Burner for Gas Fired Firetube Boilers

Low NOx fiber matrix burners have been developed for use in gas-fired firetube boilers. The fiber burner is a matrix of ceramic fibers vacuumformed into the appropriate burner configuration. In operation, premixed natural gas and air pass through the fiber matrix and are ignited, burning only on the outer surface. The surface radiates energy flamelessly to the firetube wall, controlling the combustion temperature to levels below thermal NOx formation temperatures. Two types of vacuum-formed ceramic fibers have been tested, showing NOx emissions in the range of 10 to 20 ppm. These materials have been fabricated into subscale burners to characterize operating range and emissions and into full size burners for retrofit into a small firetube boiler. The burner fits into the first pass of the firetube boiler and occupies approximately the same volume as the conventional flame. Boiler tests have verified the low NOx characteristics of the burner with concurrent potential for increased boiler efficiency. Additional testing will verify burner durability for implementation in existing boiler systems.