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Show AFRC Fall 1990 When furnaces utilize natural draft for supplying combustion air it is difficult for the furnace operators to control excess air , so it was necessary to ensure the ability to control N Ox over a wide range of excess air levels. Therefore tests were run over excess oxygen levels ranging from 1 % to 6% 02. The furnace temperatures were measured at the outlet of the firebox with a suction pyrometer. Other instrumentation used included a ThermoElectron Model lOA Chemiluminescent NOx analyzer, ThennoElectron Model 48 Gas Filter Correlation CO analyzer and a Teledyne Model326B Paramagnetic Oxygen analyzer. --:' ,DEVELOPMENT TEST RESULTS Figure 2 provides data for the self-recirculating staged fuel ND R burner firing natural gas and a "refinery fuel gas mixture". The data shoVlS the variation of NOx with excess oxygen and the difference between natural gas and the refinery fuel gas. The refinery fuel has an adiabatic flame temperature that is higher than natural gas which contributes to a higher NOx emission rate. The data show that SCAQNID Rule 1146 (approx. 0.05 Ib/M:MBtu) can be met with either fuel. Rule 1109 (0.03 Ib/M:MBtu) could be met when firing natural gas over a wide operating range, but could be achieved with this refinery fuel gas mixture only below 2% excess 02. Figure 3 ShOVlS the benefits of injecting steam into the primary combustion zone under these same conditions. This data shoVlS that a small amount of steam, properly injected, provides a significant benefit. In this case an injection rate of only 0.1 Ib of steam per lb of fuel is required to achieve NOx levels of less than 0.03Ib/M:MBtu. Figure 4 shoVlS the steam injection rates necessary to reduce NOx at three excess oxygen levels from 3% to 6%. This figure shoVlS that increasingly greater steam injection rates are required at higher and higher excess oxygen levels. In each case, however, it is possible to reduce N Ox emissions to meet Rule 1109 and even for the worst case shown (6% Ov the steam usage is less than 0.2 lb of steam per lb of fuel. As a comparison, the steam rates shown are similar to typical steam consumption rates for oil fired burners. FIELD TEST RESULTS , Based on development and demonstration.tests at the John Zink Research Facility, AReO Products Company deCided to install the NDR burner in a mid-sized heater at the ARCO Refinery in Carson, CA The heater selected for the installation was a 39 M11Btu/br bottom fired vertical cylindrical heater. The burners were installed in a close packed circle of five burners at 7.8 :Nf11Btu/hr mamnUITI heat release per burner. The furnace heats a naphtha hydrocarbon stream in the radiant section in preparation for a hydrodesulfurization process. Boiler feed .. 3 |