Development and validation of CFD models for gas phase reactions in biomass grate furnaces considering gas streak formation above the packed bed

Ali SHIEHNEJADHESAR, Robert Scharler, Ramin Mehrabian, Ingwald Obernberger

Research output: Contribution to journalArticleResearchpeer-review

Abstract

State-of-the-art packed bed models supply continuous concentration profiles as boundary conditions for subsequent CFD simulations of gas phase, leading to pre-mixed combustion conditions. However, in reality the "porous" nature of the packed bed leads to streak formation influencing gas mixing and combustion. Therefore, in the present work, in order to account for the influence of the streaks on gas phase combustion, a gas streak model based on a correlation between the local gas residence time and a mixing time has been developed based on numerical simulations. Finally, the streak model was linked with an in-housed developed hybrid gas phase combustion model suitable for laminar to highly turbulent flow conditions and applied for an under-feed pellet stoker furnace (20 kWth) concerning the simulation of gas phase combustion and NOx formation. The results in comparison with a simulation without the streak formation model show that the flue gas species prediction can be improved with the proposed streak formation model. Especially, in the region above the fuel bed (in the primary combustion chamber), this is of special importance for NOx reduction by primary measures.

Original languageEnglish
Pages (from-to)142-158
Number of pages17
JournalFuel processing technology
Volume139
DOIs
Publication statusPublished - 22 Apr 2015

Fingerprint

Gas furnaces
Packed beds
Computational fluid dynamics
Biomass
Gases
Stokers
Combustion chambers
Flue gases
Turbulent flow
Furnaces
Boundary conditions
Computer simulation

Keywords

  • Biomass
  • CFD modelling
  • Combustion
  • Grate furnace
  • Hybrid model
  • Streak formation model

ASJC Scopus subject areas

  • Fuel Technology
  • Energy Engineering and Power Technology
  • Chemical Engineering(all)

Cite this

Development and validation of CFD models for gas phase reactions in biomass grate furnaces considering gas streak formation above the packed bed. / SHIEHNEJADHESAR, Ali; Scharler, Robert; Mehrabian, Ramin; Obernberger, Ingwald.

In: Fuel processing technology, Vol. 139, 22.04.2015, p. 142-158.

Research output: Contribution to journalArticleResearchpeer-review

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AU - Obernberger, Ingwald

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AB - State-of-the-art packed bed models supply continuous concentration profiles as boundary conditions for subsequent CFD simulations of gas phase, leading to pre-mixed combustion conditions. However, in reality the "porous" nature of the packed bed leads to streak formation influencing gas mixing and combustion. Therefore, in the present work, in order to account for the influence of the streaks on gas phase combustion, a gas streak model based on a correlation between the local gas residence time and a mixing time has been developed based on numerical simulations. Finally, the streak model was linked with an in-housed developed hybrid gas phase combustion model suitable for laminar to highly turbulent flow conditions and applied for an under-feed pellet stoker furnace (20 kWth) concerning the simulation of gas phase combustion and NOx formation. The results in comparison with a simulation without the streak formation model show that the flue gas species prediction can be improved with the proposed streak formation model. Especially, in the region above the fuel bed (in the primary combustion chamber), this is of special importance for NOx reduction by primary measures.

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