Pulverized coal combustion: Fuel nitrogen mechanisms in the rich post-flame

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:7034576

Bose, A C

Chemical kinetic mechanism governing the fate of coal nitrogen in the fuel-rich state of pulverized-coal staged combustion process were investigated. Emphasis was on determination of the effects of coal rank, temperature and stoichiometric ratios on the speciation and rates of destruction of nitrogeneous species and correlation of coal data by a unified mechanism. The relative importance of homogeneous and heterogenous mechanism during post-flame interconversion reactions of the fuel nitrogen pool was quantified. Experiments with doped propane gas and a high- and low-grade coals, burned under a variety of conditions in a 2 Kg/h downflow combustor, yielded time-resolved profiles of temperature, major (H{sub 2}, CO, CO{sub 2}, O{sub 2}, and N{sub 2}), nitrogenous (NO, HCN, and NH{sub 3}) and hydrocarbon (CH{sub 4} and C{sub 2}H{sub 2}) species. A general correlation describing the destruction rate of NO was derived from data. This rate was generally valid for all coals and all conditions examined. Fuel nitrogen interconversion reactions, especially destruction of NO and HCN, was predominantly homogeneous, but no single elementary reaction was controlling. Expression for estimating the OH equilibrium overshoot as a function of the axial temperature decay along the combustor were derived both empirically and kinetically from fundamental considerations using data from doped propane gas runs. These expressions, together with available literature values of gas phase rate coefficients, could adequately describe the post-flame NO and HCN profiles of coal and gas runs. HCN profiles in the far post-flame zone of the coal flames are strongly influenced by the slow release of nitrogen from the coal residue. This devolatilization plays a critical role in supplying the HCN that derives the multistep process converting fuel N into molecular N.

• Research Organization: Arizona Univ., Tucson, AZ (USA)
• OSTI ID: 7034576
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010800 -- Coal
Lignite
& Peat-- Waste Management
014000* -- Coal
Lignite
& Peat-- Combustion
ACETYLENE
ALKANES
ALKYNES
AMMONIA
CARBONACEOUS MATERIALS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COAL
COAL RANK
COMBUSTION
COMBUSTION KINETICS
COMBUSTORS
CYANIDES
DEVOLATILIZATION
DOPED MATERIALS
ELEMENTS
ENERGY SOURCES
FOSSIL FUELS
FUELS
HYDRIDES
HYDROCARBONS
HYDROCYANIC ACID
HYDROGEN COMPOUNDS
INORGANIC ACIDS
KINETICS
MATERIALS
METHANE
NITRIC OXIDE
NITROGEN
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NITROGEN OXIDES
NONMETALS
ORGANIC COMPOUNDS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PROPANE
PULVERIZED FUELS
REACTION INTERMEDIATES
REACTION KINETICS
STAGED COMBUSTION
STOICHIOMETRY
SYNTHESIS
TEMPERATURE DEPENDENCE
THERMOCHEMICAL PROCESSES