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Title	Air Staging and Reburning Mechanisms for NOx Abatement in a Laboratory Coal Combustor
Creator	Wendt, J. O. L.; Mereb, J. B.
Publisher	Digitized by J. Willard Marriott Library, University of Utah
Date	1991
Spatial Coverage	presented at Honolulu, Hawaii
Abstract	Mechanisms that govern the formation and destruction of nitrogenous species in fuel rich zones caused by air staging and reburning were explored in a laboratory coal combustor. The objective was to determine whether the same simplified, but fundamentally based mechanism would predict time resolved profiles of all nitrogenous species, for both NOx abatement procedures. Experimentation was conducted on a 17 kW down-fired pulverized coal combustor, burning a variety of coals, under various air staged and fuel staged configurations. Heterogeneous effects on HCN formation due to the slow release of nitrogen from the coal residue were of minor significance. HCN formation and destruction in fuel rich regimes were governed by homogeneous gas phase kinetics alone. The fixation of N2 by hydrocarbons to form HCN, together with reactions of hydrocarbons radicals with either NO or N atoms, could explain HCN formation, during both air and fuel staging. The inter-conversion of nitrogenous species in the fuel rich zones of air or fuel staging configurations could be adequately described by a simplified mechanism based on known detailed gas phase reactions and partial equilibrium assumptions. Profiles of NO, HCN and NH3 were adequately predicted for both NOx abatement configurations, and the proposed mechanism should prove useful for incorporation into more complicated furnace models to predict NO emissions from practical coal combustion systems.
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Format	application/pdf
Language	eng
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ARK	ark:/87278/s69g5qcn
Setname	uu_afrc
ID	6994
Reference URL	https://collections.lib.utah.edu/ark:/87278/s69g5qcn

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Title	Page 10
Format	application/pdf
OCR Text	Show CONCLUSIONS In the study of fuel rich regimes in reburning and air staging configurations, heterogeneous effects were minor contributors to HCN formation in the far coal post flame. Consequently, the inter-conversion of nitrogenous species in fuel rich regimes could be adequately described by homogeneous gas phase kinetics. Gas phase hydrocarbon reactions which include Fenimore (1973) N2 fixation reaction and reactions of hydrocarbon radicals with NO and N were successful in describing HCN formation in fuel rich regimes in both reburning and au staging configurations. Hydrocarbons were critical in destroying NO throughout the fuel rich zone. Reactions of NO with 1'~ lJOG I 2IMI > E ~tOO o Z , I&.-""---'~--" , tOO :ato JOG 400 . NO. ppmv - ",.Iured 1 100 ~ I eo ~ % • "--'~---'~ o so 100 eo :ato HQ(, ppmv - ... osured CHi and NHi radicals were both essential in NO decay Figure 7 Natural Gas Reburningmechanism in fuel rich regimes in both reburning and Comparison of Measurements and staging configurations. The exclusion of NO Predictions. destruction by hydrocarbon radicals can only be justified under conditions where hydrocarbon concentrations are low (less than 0.1 %). These results do not concur with the previous conclusions of Bose and Wendt (1988), with respect to the role of heterogeneous effects on HCN formation and the relative significance of NO destruction by hydrocarbon radicals. A simple mechanism, based on homogeneous gas phase kinetics, known kinetic parameters and partial equilibrium assumptions, was successful in describing the fate of nitrogenous species in fuel rich regimes in both reburning and staging configurations. ACKNOWLEDGEMENT This work was supported by the U.S. 1800 > 100 E Q. Q. M .!! 400 .u, Q. III Z x 200 o run. ua sa - 0." run. ua • - 0.61 , , ~ \ 0 0 or: .•••..•. ~·!f:j;i·O 6·tri.7 ·6 0.0 0.' U La 1..4 0.0 0.' U La 2.4 l .O Residence TIm .. s Residence Tim., s o ....... _.. 10 D........ ICII ............ n, -h.4.1u" 10 -~l&t" ICII -'n4.1u"., Department of Energy, Pittsburgh Energy Figure 8: Air staging- measured and predicted Technology Center under Contract No. profiles. Bituminous coal. DE-AC22-87PC78850. 10
Setname	uu_afrc
ID	6991
Reference URL	https://collections.lib.utah.edu/ark:/87278/s69g5qcn/6991