Modeling post-flame sulfation of KCl and KOH in bio-dust combustion with full and simplified mechanisms

Michella R. Mortensen, Hamid Hashemi, Hao Wu, Peter Glarborg*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The gas-phase interaction between alkali volatiles and sulphur oxides has important implications for deposition and corrosion in combustion of biomass. In the present study, gas-phase transformation of KOH and KCl in the post-flame zone in bio-dust combustion has been studied by detailed chemical kinetic modeling for a woody and a herbaceous biomass, respectively. For both biomasses K > Cl on a molar basis, and KOH is the major alkali species at high temperature. The modeling indicates that KOH is readily converted to K2SO4 in the presence of SO2 at temperatures below 1500 K. Below 1100 K, gaseous K2SO4 nucleates homogeneously, promoting further sulfation. For the woody biomass, where K < Cl + 2S, the sulfation process is kinetically limited due to the competition with chlorination. For the herbaceous biomass, with K > Cl + 2S, the excess KOH facilitates internal equilibration among the alkali species. For both biomasses, the KCl concentration remains constant during sulfation, because any KCl consumed is rapidly replenished by the reaction KOH + HCl  KCl + H2O. The consequence is that the sulfation process under the investigated conditions does not help to remove the main corrosive agent, KCl. For use in CFD, a skeletal model for the gas-phase sulfation of KCl and KOH has been developed, based on systematic reduction of the detailed chemical kinetic model. However, for fuels with excess K compared to Cl + 2S, a simple equilibrium calculation may yield satisfactory results.
Original languageEnglish
Article number116147
JournalFuel
Volume258
ISSN0016-2361
DOIs
Publication statusPublished - 2019

Keywords

  • Biomass
  • Combustion
  • Potassium
  • Sulfation
  • Kinetic model
  • Skeletal mechanism

Cite this

@article{c19d2388581e421c9dedffded2b3d4b0,
title = "Modeling post-flame sulfation of KCl and KOH in bio-dust combustion with full and simplified mechanisms",
abstract = "The gas-phase interaction between alkali volatiles and sulphur oxides has important implications for deposition and corrosion in combustion of biomass. In the present study, gas-phase transformation of KOH and KCl in the post-flame zone in bio-dust combustion has been studied by detailed chemical kinetic modeling for a woody and a herbaceous biomass, respectively. For both biomasses K > Cl on a molar basis, and KOH is the major alkali species at high temperature. The modeling indicates that KOH is readily converted to K2SO4 in the presence of SO2 at temperatures below 1500 K. Below 1100 K, gaseous K2SO4 nucleates homogeneously, promoting further sulfation. For the woody biomass, where K < Cl + 2S, the sulfation process is kinetically limited due to the competition with chlorination. For the herbaceous biomass, with K > Cl + 2S, the excess KOH facilitates internal equilibration among the alkali species. For both biomasses, the KCl concentration remains constant during sulfation, because any KCl consumed is rapidly replenished by the reaction KOH + HCl  KCl + H2O. The consequence is that the sulfation process under the investigated conditions does not help to remove the main corrosive agent, KCl. For use in CFD, a skeletal model for the gas-phase sulfation of KCl and KOH has been developed, based on systematic reduction of the detailed chemical kinetic model. However, for fuels with excess K compared to Cl + 2S, a simple equilibrium calculation may yield satisfactory results.",
keywords = "Biomass, Combustion, Potassium, Sulfation, Kinetic model, Skeletal mechanism",
author = "Mortensen, {Michella R.} and Hamid Hashemi and Hao Wu and Peter Glarborg",
year = "2019",
doi = "10.1016/j.fuel.2019.116147",
language = "English",
volume = "258",
journal = "Fuel",
issn = "0016-2361",
publisher = "Elsevier",

}

Modeling post-flame sulfation of KCl and KOH in bio-dust combustion with full and simplified mechanisms. / Mortensen, Michella R.; Hashemi, Hamid; Wu, Hao; Glarborg, Peter.

In: Fuel, Vol. 258, 116147, 2019.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Modeling post-flame sulfation of KCl and KOH in bio-dust combustion with full and simplified mechanisms

AU - Mortensen, Michella R.

AU - Hashemi, Hamid

AU - Wu, Hao

AU - Glarborg, Peter

PY - 2019

Y1 - 2019

N2 - The gas-phase interaction between alkali volatiles and sulphur oxides has important implications for deposition and corrosion in combustion of biomass. In the present study, gas-phase transformation of KOH and KCl in the post-flame zone in bio-dust combustion has been studied by detailed chemical kinetic modeling for a woody and a herbaceous biomass, respectively. For both biomasses K > Cl on a molar basis, and KOH is the major alkali species at high temperature. The modeling indicates that KOH is readily converted to K2SO4 in the presence of SO2 at temperatures below 1500 K. Below 1100 K, gaseous K2SO4 nucleates homogeneously, promoting further sulfation. For the woody biomass, where K < Cl + 2S, the sulfation process is kinetically limited due to the competition with chlorination. For the herbaceous biomass, with K > Cl + 2S, the excess KOH facilitates internal equilibration among the alkali species. For both biomasses, the KCl concentration remains constant during sulfation, because any KCl consumed is rapidly replenished by the reaction KOH + HCl  KCl + H2O. The consequence is that the sulfation process under the investigated conditions does not help to remove the main corrosive agent, KCl. For use in CFD, a skeletal model for the gas-phase sulfation of KCl and KOH has been developed, based on systematic reduction of the detailed chemical kinetic model. However, for fuels with excess K compared to Cl + 2S, a simple equilibrium calculation may yield satisfactory results.

AB - The gas-phase interaction between alkali volatiles and sulphur oxides has important implications for deposition and corrosion in combustion of biomass. In the present study, gas-phase transformation of KOH and KCl in the post-flame zone in bio-dust combustion has been studied by detailed chemical kinetic modeling for a woody and a herbaceous biomass, respectively. For both biomasses K > Cl on a molar basis, and KOH is the major alkali species at high temperature. The modeling indicates that KOH is readily converted to K2SO4 in the presence of SO2 at temperatures below 1500 K. Below 1100 K, gaseous K2SO4 nucleates homogeneously, promoting further sulfation. For the woody biomass, where K < Cl + 2S, the sulfation process is kinetically limited due to the competition with chlorination. For the herbaceous biomass, with K > Cl + 2S, the excess KOH facilitates internal equilibration among the alkali species. For both biomasses, the KCl concentration remains constant during sulfation, because any KCl consumed is rapidly replenished by the reaction KOH + HCl  KCl + H2O. The consequence is that the sulfation process under the investigated conditions does not help to remove the main corrosive agent, KCl. For use in CFD, a skeletal model for the gas-phase sulfation of KCl and KOH has been developed, based on systematic reduction of the detailed chemical kinetic model. However, for fuels with excess K compared to Cl + 2S, a simple equilibrium calculation may yield satisfactory results.

KW - Biomass

KW - Combustion

KW - Potassium

KW - Sulfation

KW - Kinetic model

KW - Skeletal mechanism

U2 - 10.1016/j.fuel.2019.116147

DO - 10.1016/j.fuel.2019.116147

M3 - Journal article

VL - 258

JO - Fuel

JF - Fuel

SN - 0016-2361

M1 - 116147

ER -