Effect of NO and O{sub 2} concentration on N{sub 2}O formation during coal combustion in a fluidized-bed combustor: Modeling results
- Massachusetts Inst. of Technology, Cambridge, MA (United States). Dept. of Chemical Engineering
This paper addresses the issue of the understanding the NO and N{sub 2}O formation kinetics during char combustion in a fluidized-bed combustor. A single-particle numerical model that simulates the combined internal diffusion and reaction equations is developed. Kinetic parameters for the char oxidation, CO and CO{sub 2} formation, NO formation and destruction both by char and by a char-catalyzed CO reaction, and N{sub 2}O formation and destruction reactions have been estimated using fractional order kinetics. Modeling results have been compared with the experimental data. Primarily, N{sub 2}O is formed by the reaction of NO with char nitrogen in the presence of O{sub 2}. Formation of N{sub 2}O increases with increases in the bulk NO concentration. N{sub 2}O, however, is not formed in the absence of oxygen, as oxygen is required to release the char nitrogen bound in aromatic rings. A higher O{sub 2} concentration in the feed gas gives higher concentrations of NO and N{sub 2}O. The instantaneous conversion of char nitrogen to N{sub 2}O increases, whereas the conversion to NO decreases, with increases in bulk O{sub 2} concentration. The char-catalyzed NO/CO reaction at low temperatures and high O{sub 2} concentrations is the dominant destruction mechanism for NO. At high temperature, NO is destroyed mainly by its heterogeneous reaction with char.
- OSTI ID:
- 93256
- Report Number(s):
- CONF-940711--
- Country of Publication:
- United States
- Language:
- English
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