Combustion properties of coal-char blends: NO{sub x} emission characteristics
Journal Article
·
· Preprints of Papers, American Chemical Society, Division of Fuel Chemistry
OSTI ID:420567
- Illinois State Geological Survey, Champaign, IL (United States); and others
Nitric oxide formation in hydrocarbon flames occurs primarily through three mechanisms; thermal NO (the fixation of molecular nitrogen by oxygen atoms produced at high temperatures), fuel NO (the oxidation of nitrogen contained in the fuel during combustion), and prompt NO (the attack of a hydrocarbon radical on molecular nitrogen). Of these three mechanisms, fuel NO is by far the most significant source of NO in practical coal flames. It has been suggested that NO{sub x} produced early in pulverized coal flames is subsequently reduced to N{sub 2} by char/NO{sub x} interactions. NO{sub x} can be both produced and reduced by heterogeneous char reactions. For some cases, as much as half of the fuel nitrogen remains in the coal after devolatilization. The amount retained apparently is a function of the reactor stoichiometry. Heterogeneous NO{sub x} often accounts for 20-30 percent of the total NO{sub x} formed. The exact amount appears to be dependent on the temperature and extent of devolatilization. The rate of heterogeneous NO{sub x} reduction has been investigated by many researchers. Essentially, char reduction of NO{sub x} begins only after oxygen is locally depleted in the reactor. The heterogeneous destruction reactions have been determined to be significant in fuel-lean conditions for char combustion, but for fuel-rich coal combustion, the reduction reactions in the gaseous phase appears to control reaction rate. CO enhances NO{sub x} reduction due to surface catalysis of the NO/CO reaction. In the absence of CO{sub 2} the char-NO{sub x} reduction rate is controlled by the dual-site mechanism of absorbed NO{sub x}. In the presence of CO{sub 2} the controlling step is the reaction of gaseous NO{sub 2}, and absorbed NO{sub x}, at an active site to form N{sub 2}, CO{sub 2}, and an oxide complex. Water and O{sub 2} were reported to inhibit the reaction due to the buildup of a chemisorbed layer of oxygen on the char surface.
- OSTI ID:
- 420567
- Report Number(s):
- CONF-960807--
- Journal Information:
- Preprints of Papers, American Chemical Society, Division of Fuel Chemistry, Journal Name: Preprints of Papers, American Chemical Society, Division of Fuel Chemistry Journal Issue: 3 Vol. 41; ISSN ACFPAI; ISSN 0569-3772
- Country of Publication:
- United States
- Language:
- English
Similar Records
Role of char during reburning of nitrogen oxides. First quarterly report, October 1, 1993--December 31, 1993
NO/sub x/-char reactions: Kinetics and transport aspects: Quarterly technical progress report, 1 January 1988-31 March 1988
A Mechanistic Investigation of Nitrogen Evolution and Corrosion with Oxy-Combustion
Technical Report
·
Thu Dec 30 23:00:00 EST 1993
·
OSTI ID:10133918
NO/sub x/-char reactions: Kinetics and transport aspects: Quarterly technical progress report, 1 January 1988-31 March 1988
Technical Report
·
Thu Dec 31 23:00:00 EST 1987
·
OSTI ID:6910302
A Mechanistic Investigation of Nitrogen Evolution and Corrosion with Oxy-Combustion
Technical Report
·
Tue Dec 30 23:00:00 EST 2008
·
OSTI ID:952456