NO Emission Characteristics of Low-Rank Pulverized Bituminous Coal in the Primary Combustion Zone of a Drop-Tube Furnace

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Author list: Fei J, Sun R, Yu LB, Liao JA, Sun S, Kelebopile L, Qin YK

Publisher: American Chemical Society

Place: WASHINGTON

Publication year: 2010

Journal: Energy and Fuels (0887-0624)

Journal acronym: ENERG FUEL

Volume number: 24

Issue number: 6

Start page: 3471

End page: 3478

Number of pages: 8

ISSN: 0887-0624

eISSN: 1520-5029

Languages: English-Great Britain (EN-GB)

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Abstract

Experiments were conducted in a drop-tube furnace (DTI-7) to investigate NO emission characteristics of low-rank bituminous coal burning in the primary combustion zone. The combustion tests were performed under high-stoichiometric-ratio (SR) combustion conditions (SR >= 1) and low-SR combustion conditions (SR < 1). Along the length of the furnace, concentrations of flue gas species, such as NO, HCN, NH3, CH4, CO, CO2, and O-2, were carefully measured during pyrolysis and different SR combustion conditions. The results for high-SR combustion conditions show that high concentrations of O-2 favor the conversion of volatile N and char N into NO, with extensive NO formation taking place in the initial stages of combustion. Reducing species, such as CH4, C2H6, and NH3, in volatile matter were mostly oxidized and generated little effect on NO elimination. Results from low-SR combustion conditions show that there is insufficient 02 for oxidization of combustibles, allowing more hydrocarbons to react with NO. For the coal tested in these experiments, the conversion ratio of fuel N to NO, R-fuel N, N. yielded the lowest minimum values around SR = 0.9 among all such ratios because of a larger fraction of fuel N being decomposed from coal particles through pyrolysis, as well is char oxidization being reduced to N-2. For lower SR conditions, the total fixed nitrogen (TEN), which includes NO. NH3, and HCN. can be reduced to N, by homogeneous reactions, so that the remaining N in char becomes the major contributor of NO emissions in the burnout zone.

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