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Show L o w - N O x no-FGR gas/oil burner improvement L. Tsirulnikov, E. Schindler, M. Gamburg, F. MacArthur, M. Brecker Todd Combustion, Shelton, C T Todd Combustion has developed and brought to market a new low-NOx burner design mostly suitable for new and existing package industrial steam boilers and hot water generators. The burner schematic is shown in Fig.l. It has consisted of the following main subassemblies: -a venturi tube positioned to direct air flow through the burner into the furnace, separating the swirled primary and straight secondary air flows from the straight tertiary air flow, passing in the space between the venturi tube and the front wall entrance in the furnace, -a primary air swirler, separating this flow from the straight secondary air flow, which is surrounding the swirled primary air flow, -internal F G R ducts, taking flue gas from the furnace comers adjacent to the front wall where the burner is installed, and distributing it in the venturi tube throat, -CFG (central fire gas gun) distributing natural gas jets in the swirled primary air flow, -outside gas injectors, distributing natural gas in the straight secondary and tertiary air flows. It can be seen from a comparison, that the air channels are the same as in the standard Todd Variflame burner. As per regular Todd requirements, the burner and windbox were modeled in order to provide required air distribution. However, unlike of the standard prototype, the burner has completely other design of the two gas supply units - the C F G and a set of the outside injectors, replacing the inside gas pokers implemented in the prototype. Also the burner contains no an external flue gas recirculation system (EFGR), and instead it utilizes the internal furnace flue gas recirculation (EFGR) characterized by hot temperature (~ 2000°F against ~600°F cold F G R ) and high concentrations (up to 8 0 % ) of incomplete combustion products (ICP). The Variflame-2 burner has currently been installed and tested on four distinct package industrial boilers. It provides high efficiency operation on natural gas and #6 oil in the load range of 100 to 25-20%, with ambient and preheated air. The tested burners heat input vary between 28 to 134 M M B T U / h . The burner does not require F G R fan. The burner does not require high gas pressure, it operates on moderate gas pressure (<6 psig) and provides the 4:1 emission turndown at a register draft loss (RDL) < 8"wc at ambient air. The following performances are achieved in full turndown with ambient air on the package industrial boilers equipped with the 28 to 84.8 M M B T U / h burners: N O x < 30 ppm, C O < 150 p p m on natural gas and N O x < 300 ppm, C O < 100 p p m and opacity < 1 |
