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Show DILUTE OXYGEN COMBUSTION H.M. Ryan, A.W. Francis, M.F. Riley and H. Kobayashi Applications Research and Development Praxair, Inc. Tarrytown, NY 10591 ABSTRACT A novel burner system, in which fuel (natural gas) and oxidant (oxygen or air) are separately injected into a furnace, shows promise for achieving ultra-low NOx emissions for commercial furnace applications. The dilute oxygen combustion (DOC) burner concept achieves ultra-low NOx through in-furnace dilution of the oxidant stream prior to combustion, resulting in low flame temperatures, thus inhibiting thermal NOx production. The results of a fundamental and applied research effort on the development of the DOC burner system are presented. The fundamental aspects of the burner development program involved examining the entrainment and flame lift-off characteristics of a natural gas jet in a high-temperature (-1366 K) oxidant (7-27% O2 vol. wet). The measured entrainment rate of the fuel jet decreased with increasing oxygen content in the surrounding high-temperature oxidant. As expected, the flame lift-off height decreased with increasing oxygen content and increasing temperature of the surrounding gas. Several DOC burner configurations were tested in a laboratory -scale furnace at fIring rates of 185 kW (0.6 MMBtu/h). The flue gas composition was recorded as a function of furnace nitrogen content, furnace temperature and burner geometric arrangement. NOx emissions increased with increasing furnace nitrogen content and furnace temperature. NOx emissions below 5.10-3 g/MJ (10 ppmd-air equivalent at 3% O2 dry) were obtained for furnace temperatures below 1533 K (2300°F) and furnace nitrogen levels between 1 and 40%. CO emissions were typically low ( < 35 ppmd). INTRODUCTION Effective nitrogen oxide(s) (NOx) emission control strategies are highly sought after due to strict emission standards articulated by various regulating committees. Many current NOx control strategies attempt to limit NOx production through the design parameters of the particular combustion device (e.g., burner) involved. A similar approach has been taken here in the development of an ultra-low NOx burner system for commercial furnace applications. In essence, the novel technique, termed dilute oxygen combustion (DOC), involves introducing the fuel and oxidant separately into a furnace and achieving sufficient in-furnace dilution of the oxidant with combustion products to lead to low flame temperatures and, consequently, low NOx• Copyright © 1996 Praxair Technology, Inc. All Rights Reserved. 1 |
