Effects of flue gas internal recirculation on NOx and SOx emissions in a co-firing boiler

Jun Li, Xiaolei Zhang, Weihong Yang, Wlodzimierz Blasiak

Research output: Contribution to journalArticle

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Abstract

Volumetric combustion has been developed to realize a high substitution ratio of biomass in co-firing boilers, which features an intensive flue gas internal recirculation inside furnace. However, the characteristics of NOx and SOx emis-sions in large-scale boilers with volumetric combustion were not fully clear. In this paper, an Aspen Plus model of volumetric combustion system was built up based on a co-firing boiler. In order to characterize the reductions of NOx and SOx, three biomass substitution ratios were involved, namely, 100% biomass, 45% biomass with 55% coal, and 100% coal. The effects of flue gas recirculation ratio, air preheating temperature, oxygen concentration, and fuel types on pollutants emission in the volumetric combustion system were investigated. According to the results, it was con-cluded the higher substitution ratio of biomass in a co-firing boiler, the lower emissions of NOx and SOx. Moreover, flue gas internal recirculation is an effective pathway for NOx reduction and an increased recirculation ratio resulted in a significant decreasing of NOx emission; however, the SOx increased slightly. The influences of air preheating tem-perature and O2 concentration on NOx emission were getting weak with increasing of recirculation ratio. When 10% or even higher of flue gas was recycled, it was observed that almost no NOx formed thermodynamically under all studied conditions. Finally, to reach a low emission level of NOx, less energy would be consumed during biomass combustion than coal combustion process for internal recirculation of flue gas.
Original languageEnglish
Pages (from-to)13-21
Number of pages9
JournalInternational Journal of Clean Coal and Energy
Volume2
Issue number2
DOIs
Publication statusPublished - May 2013

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Boiler firing
Flue gases
Biomass
Substitution reactions
Coal
Preheating
Coal combustion
Air
Boilers
Furnaces
Oxygen

Keywords

  • flue gas internal recirculation
  • SOx
  • NOx
  • co-firing

Cite this

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title = "Effects of flue gas internal recirculation on NOx and SOx emissions in a co-firing boiler",
abstract = "Volumetric combustion has been developed to realize a high substitution ratio of biomass in co-firing boilers, which features an intensive flue gas internal recirculation inside furnace. However, the characteristics of NOx and SOx emis-sions in large-scale boilers with volumetric combustion were not fully clear. In this paper, an Aspen Plus model of volumetric combustion system was built up based on a co-firing boiler. In order to characterize the reductions of NOx and SOx, three biomass substitution ratios were involved, namely, 100{\%} biomass, 45{\%} biomass with 55{\%} coal, and 100{\%} coal. The effects of flue gas recirculation ratio, air preheating temperature, oxygen concentration, and fuel types on pollutants emission in the volumetric combustion system were investigated. According to the results, it was con-cluded the higher substitution ratio of biomass in a co-firing boiler, the lower emissions of NOx and SOx. Moreover, flue gas internal recirculation is an effective pathway for NOx reduction and an increased recirculation ratio resulted in a significant decreasing of NOx emission; however, the SOx increased slightly. The influences of air preheating tem-perature and O2 concentration on NOx emission were getting weak with increasing of recirculation ratio. When 10{\%} or even higher of flue gas was recycled, it was observed that almost no NOx formed thermodynamically under all studied conditions. Finally, to reach a low emission level of NOx, less energy would be consumed during biomass combustion than coal combustion process for internal recirculation of flue gas.",
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Effects of flue gas internal recirculation on NOx and SOx emissions in a co-firing boiler. / Li, Jun; Zhang, Xiaolei; Yang, Weihong; Blasiak, Wlodzimierz.

In: International Journal of Clean Coal and Energy, Vol. 2, No. 2, 05.2013, p. 13-21.

Research output: Contribution to journalArticle

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