Abstract
Two aspects of gas injection in the flue gas entrance of the cyclone as a means of reducing nitrous oxide (N{sub 2}O) emissions from circulating fluidized bed (CFB) boilers were investigated. The first was the possible influence of an increased gas temperature on sulphur capture. Full-scale experiments showed that under normal operating conditions sulphur capture is unaffected by afterburning at injection fuel ratios up to 18%. There seems however to an upper limit in cyclone outlet temperature of about 1000 deg. C when operating at 5% O{sub 2} and 950 deg. C at 2% O{sub 2} respectively. Above these temperatures, SO{sub 2} emissions tend to increase, reflecting a reemission. The practical impact of this limit is small, since N{sub 2}O reduction ratios of 80-85% are achieved at temperatures below the limit. The second aspect was a possible reduction in efficiency of afterburning through radical quenching of particles. Calculations were performed, using a C{sub 1}/C{sub 2}/C{sub 3}/N chemical kinetic scheme, including heterogeneous reaction of radicals with carbon on the particle surface as well as recombination on the surface. Input concentrations of gas components and particles as well as particle-size distribution and flow rates were taken from full-scale experiments. The calculations showed
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Gustavsson, L;
[1]
Glarborg, P;
[2]
Leckner, B
[3]
- Swedish National Testing and Research Institute (Sweden)
- Technical University of Denmark (Denmark)
- Chalmers University of Technology (Sweden)
Citation Formats
Gustavsson, L, Glarborg, P, and Leckner, B.
Reduction of N{sub 2}O from CFB combustion with afterburning of gas. Influence of sulphur capture and modelling of the chemical reactions.
Denmark: N. p.,
1993.
Web.
Gustavsson, L, Glarborg, P, & Leckner, B.
Reduction of N{sub 2}O from CFB combustion with afterburning of gas. Influence of sulphur capture and modelling of the chemical reactions.
Denmark.
Gustavsson, L, Glarborg, P, and Leckner, B.
1993.
"Reduction of N{sub 2}O from CFB combustion with afterburning of gas. Influence of sulphur capture and modelling of the chemical reactions."
Denmark.
@misc{etde_10128493,
title = {Reduction of N{sub 2}O from CFB combustion with afterburning of gas. Influence of sulphur capture and modelling of the chemical reactions}
author = {Gustavsson, L, Glarborg, P, and Leckner, B}
abstractNote = {Two aspects of gas injection in the flue gas entrance of the cyclone as a means of reducing nitrous oxide (N{sub 2}O) emissions from circulating fluidized bed (CFB) boilers were investigated. The first was the possible influence of an increased gas temperature on sulphur capture. Full-scale experiments showed that under normal operating conditions sulphur capture is unaffected by afterburning at injection fuel ratios up to 18%. There seems however to an upper limit in cyclone outlet temperature of about 1000 deg. C when operating at 5% O{sub 2} and 950 deg. C at 2% O{sub 2} respectively. Above these temperatures, SO{sub 2} emissions tend to increase, reflecting a reemission. The practical impact of this limit is small, since N{sub 2}O reduction ratios of 80-85% are achieved at temperatures below the limit. The second aspect was a possible reduction in efficiency of afterburning through radical quenching of particles. Calculations were performed, using a C{sub 1}/C{sub 2}/C{sub 3}/N chemical kinetic scheme, including heterogeneous reaction of radicals with carbon on the particle surface as well as recombination on the surface. Input concentrations of gas components and particles as well as particle-size distribution and flow rates were taken from full-scale experiments. The calculations showed that particle quenching of radicals had little influence on N{sub 2}O levels at lean conditons. At near-stoichiometric conditions, the impact is more pronounced. Also for NO concentrations, particle quenching has a negligible effect at lean conditions. At low oxygen contents, the presence of particles potentially improves the NO reduction that can be obtained in the cyclone. Particle quenching could not however explain differences between earlier calculations and full-scale experiments. The agreement between present calculations and experimental data was on the contrary good, due to inclusion of revised kinetic data for the N{sub 2}O + OH reaction. (au) (28 refs.)}
place = {Denmark}
year = {1993}
month = {Dec}
}
title = {Reduction of N{sub 2}O from CFB combustion with afterburning of gas. Influence of sulphur capture and modelling of the chemical reactions}
author = {Gustavsson, L, Glarborg, P, and Leckner, B}
abstractNote = {Two aspects of gas injection in the flue gas entrance of the cyclone as a means of reducing nitrous oxide (N{sub 2}O) emissions from circulating fluidized bed (CFB) boilers were investigated. The first was the possible influence of an increased gas temperature on sulphur capture. Full-scale experiments showed that under normal operating conditions sulphur capture is unaffected by afterburning at injection fuel ratios up to 18%. There seems however to an upper limit in cyclone outlet temperature of about 1000 deg. C when operating at 5% O{sub 2} and 950 deg. C at 2% O{sub 2} respectively. Above these temperatures, SO{sub 2} emissions tend to increase, reflecting a reemission. The practical impact of this limit is small, since N{sub 2}O reduction ratios of 80-85% are achieved at temperatures below the limit. The second aspect was a possible reduction in efficiency of afterburning through radical quenching of particles. Calculations were performed, using a C{sub 1}/C{sub 2}/C{sub 3}/N chemical kinetic scheme, including heterogeneous reaction of radicals with carbon on the particle surface as well as recombination on the surface. Input concentrations of gas components and particles as well as particle-size distribution and flow rates were taken from full-scale experiments. The calculations showed that particle quenching of radicals had little influence on N{sub 2}O levels at lean conditons. At near-stoichiometric conditions, the impact is more pronounced. Also for NO concentrations, particle quenching has a negligible effect at lean conditions. At low oxygen contents, the presence of particles potentially improves the NO reduction that can be obtained in the cyclone. Particle quenching could not however explain differences between earlier calculations and full-scale experiments. The agreement between present calculations and experimental data was on the contrary good, due to inclusion of revised kinetic data for the N{sub 2}O + OH reaction. (au) (28 refs.)}
place = {Denmark}
year = {1993}
month = {Dec}
}