| OCR Text |
Show - 2 - Self inspirating, premix burners burners are often used for this type of application. They are generally sized for maximum firing rates ranging from 600,000 Btu/hr to 1,250,000 Btu/hr. The burner is mounted on the furnace sidewall and projects through the wall. The fuel is injected into a venturi eductor which inspirates combustion air. The resulting fuel/air mixture then exits the burner tip perpendicular to the burner axis through radial slots or holes in the tip. The fuel/air mixture is ejected parallel to the furnace wall forming a flame immediately adjacent to the wall. This flame heats the furnace wall in a circular pattern around each burner tip. These premix burners have been successfully used to burn a wide variety of hydrocarbon fuels including some containing up to 80 mole percent hydrogen. Hydrogen levels this high are especially challenging for premix burners due to the increased potential for flashback. Despite the high furnace temperatures, this type of burner produces relatively low NOx emissions. A conventional, self inspirating, premix burner typically emits about 50 to 80 PPM of NOx, depending on conditions. Various low NOx burners have been developed which reduce these levels by about 50% . The low NOx, self inspirating, premix burners developed by John Zink utilize INFURNOx™ technology.1 This NOx control technology is described in a paper presented at the Second International Conference on Combustion Technologies for a Clean Environment held in Lisbon in July of 1993. Figure 1, taken from that paper, shows that NOx emissions are significantly reduced for both premix and diffusion flames under fuel rich conditions with inert flue gas or furnace gas recirculation (FGR) and are similarly reduced for lean premix flames with inert gas recirculation. Very low NOx levels can be achieved by forming a lean premix flame with furnace gas recirculation using part of the fuel and then injecting the remaining fuel in a manner forming a fuel rich secondary combustion zone, also including furnace gas recirculation. By properly organizing the primary and secondary combustion zones and |
