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Show ~ j \ / \ SECONDARY COMBUSTION Figure SECONDARY FUel .. . ~' " . . . PRIMARY FUel CONNECTION HIGH AIR TO FUel RATIO IN PRIMARY ZONE . ' . .' ,0 . SECONDARY FUel CONNECTION John Zink Staged Fuel LoNoxTM Burner EXPERIMENT AL SETUP The John Zink Company International Research Center includes eight test furnaces of various sizes and configurations that allow testing of burners ranging from less than 1 million Btu per hour heat release to over 250 million Btu's per hour. The boiler burner development work was conducted on several prototype burners with design heat release rates of 25 to 100 million Btu's per hour. Furnace heat absorption rates were controlled during these tests to provide exit gas temperatures in the range of 2200 to 2500 deg F, which are typical of boiler combustion chambers, Furnace No.3, used for these tests, is a 10 foot diameter horizontal cylinder, 29 feet in length. It is equipped with ten sample/sight ports spaced along one side and three sight ports at the back end. Preheated combustion air for burners up to 100 million Btu's per hour is provided by an indirect air heater capable of preheating fresh air up to 600 deg F. Figure 2 shows a schematic view of the test setup. Figure 2 Staged Fuel Boiler Installation Schematic 346 Natural gas was used as the fuel and the flow rate was measured with a Singer positive displacement gas meter, Rockwell turbine meter or a Brooks rotameter. The furnace draft and windbox pressures were measured with manometers. A suction pyrometer was used to measure gas temperatures in the furnace and stack and a water cooled probe was used to obtain gas samples. A Thermo Electron sample conditioning system was used to dry and filter the sample. NOx was measured with a Thermo Electron Chemiluminescent Model 10 analyzer, oxygen with a Teledyne Model 326A analyzer, and carbon monoxide with an Anarad Non-dispersive Infrared analyzer model AR-500R or Teledyne model 926 analyzer. BURNER DESCRIPTION Figure 3 shows a cross-sectional cut away view of the John Zink staged fuel boiler burner. The burner is equipped with an adjustable air register that allows a full range of air mixing control from axial flow to high swirl. The bulk of the combustion air enters the burner through this register and passes through the central air tube to the burner throat. At the throat the primary fuel is injected into the combustion air and the primary combustion zone flame is stabilized. In order to provide low NOx operation over a wide range of operating conditions the primary gas tips are provided with special air diffusers and gas tip drilling patterns. Figure 3 Cutaway View 0/ John Zink Staged Fuel Boiler Burner The primary combustion zone is rooted in the burner tile and extends into the boiler combustion chamber. The secondary fuel injectors are located at the periphery of the burner tile and inject the remainder of the fuel into the end of the primary flame. Flame shaping is accomplished by controlling the axial / tangential air momentum, burner tile configuration, primary fuel injection pattern and secondary fuel injection pattern. Each of these factors also effect the NOx emission rates. DESCRIPTION OF TESTS AND RESULTS All of the test results presented here are for burners operating at design rate and a draft loss in the range of 4 to 8 inches water column. Carbon monoxide measurements for all test points were less than 100 ppm and generally less than 50 ppm. Data were also taken with conventional design burners to provide a baseline for comparison with the staged fuel designs. |