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Show material of construction. This was substantially lower than the temperature of an actual diesel exhaust stream. Another problem posed by liquid fuel firing under reducing conditions with a low oxygen stream was the potential for soot formation. Although equilibrium calculations for the composition and temperature range of the afterburner indicated that carbon would not be formed, we knew, based on our experience with conventional burners, that soot formation was likely to occur. We had been successful in firing propane fuel with diesel exhaust as the combustion oxygen source in our testing in Japan. We did not know, however, if we could successfully fire number 2 fuel oil under the same operating conditions. The HI burner shown schematically in Figure 3 was chosen for this application because Zink had successfully demonstrated that liquid fuels could be fired stably under reducing conditions with minimum soot formation. The burner had not been fired, however, with low oxygen combustion air. Therefore, an element of doubt still existed concerning the ability to fire a low oxygen combustion air source under reducing conditions in this burner. As a result of the simulated exhaust stream's lower temperature, not only was flame stabili~y at risk, but the resulting overall afterburner operating temperature was lower than the temperature achieved in the tests in Japan. For applications using actual diesel exhaust, the afterburner will operate at approximately 2500 0 F compared to the 1700 to 1750 0 F achieved in the Japan tests and, therefore, should achieve even better results than those demonstrated. Results of these proof-of-concept tests indicated that stable burner operation was achieved using the John Zink HI burner to combust a 440 to 455°F simulated diesel exhaust stream containing 10.5 to 11.4% oxygen. In addition, levels of combustibles (CO and H2) ranged from 2.5 to 5.0% with minimum soot formation in the range of 4 to 5 mg/Nm3 resulting. This level of soot formation is low compared not onlj to the levels in conventional diesel exhaust (80 to 100 mg/Nm ) but a!so to the levels in the afterburner effluent (10 to 20 mg/Nm ) measured in previous Hybrid Low NOx tests using propane as the afterburner fuel. A comparison of the afterburner chambers viewed from the exit are presented in Figure 3. -5- |