An energy and exergy analysis of biomass gasification integrated with a char-catalytic tar reforming system

David Buentello-Montoya, Xiaolei Zhang

Research output: Contribution to journalArticle

Abstract

Adequate tar removal is a recurrent challenge for biomass gasification. Materials such as char and activated char are promising catalysts for tar reforming because of their activity, inexpensiveness and constant production during gasification. Although the behaviour of char and activated char as catalyst has been previously studied, an evaluation of the thermodynamic efficiencies of the tar reforming process using char as a catalyst still lacking. This work analyses the performance of a two-stage system, where gasification is followed by tar reforming using char catalysts. For the study, a model based in a combination of equilibrium thermodynamics and chemical kinetics was developed. The first stage, where gasification occurs, was simulated with a thermodynamic equilibrium model. Gasification equilibrium models available in literature only predict the fractions of H2, CO, CO2 and CH4; the model developed for this work also predicts the formation of three model tars with different characteristics (benzene, toluene and naphthalene), providing information on the stability of formed tars. The second stage, simulated using kinetics from literature, consists on reforming the tars with catalysts made of residual char. The effects of the reactor temperature, equivalence ratio, and residence time were assessed via the gas quality, based on the gas lower heating value and tar concentration, and process efficiency, based on the energy and exergy efficiencies. Results showed that using char or activated char catalysts increases the heating value of the gas while reducing its tar concentration. Moreover, the process benefits thermodynamically (i.e. less exergy is destroyed) from low gasification temperatures and high reforming temperatures. Simulations indicate that a tarless gas with a lower heating value of more than 8 MJ/Nm3 can be produced from gasification at 1023K with an equivalence ratio of 0.15 and subsequent reforming at 1123K with a residence time in the catalyst bed of 1 second.
LanguageEnglish
Pages8746-8757
Number of pages12
JournalEnergy and Fuels
Volume33
Issue number9
Early online date13 Aug 2019
DOIs
Publication statusPublished - 19 Sep 2019

Fingerprint

Tars
Exergy
Tar
Reforming reactions
Gasification
Biomass
Catalysts
Gases
Thermodynamics
Heating
Toluene
Carbon Monoxide
Naphthalene
Benzene
Reaction kinetics
Temperature
Kinetics

Keywords

  • thermodynamic equilibrium model
  • tar reforming
  • char catalyst
  • gasification
  • exergy analysis

Cite this

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abstract = "Adequate tar removal is a recurrent challenge for biomass gasification. Materials such as char and activated char are promising catalysts for tar reforming because of their activity, inexpensiveness and constant production during gasification. Although the behaviour of char and activated char as catalyst has been previously studied, an evaluation of the thermodynamic efficiencies of the tar reforming process using char as a catalyst still lacking. This work analyses the performance of a two-stage system, where gasification is followed by tar reforming using char catalysts. For the study, a model based in a combination of equilibrium thermodynamics and chemical kinetics was developed. The first stage, where gasification occurs, was simulated with a thermodynamic equilibrium model. Gasification equilibrium models available in literature only predict the fractions of H2, CO, CO2 and CH4; the model developed for this work also predicts the formation of three model tars with different characteristics (benzene, toluene and naphthalene), providing information on the stability of formed tars. The second stage, simulated using kinetics from literature, consists on reforming the tars with catalysts made of residual char. The effects of the reactor temperature, equivalence ratio, and residence time were assessed via the gas quality, based on the gas lower heating value and tar concentration, and process efficiency, based on the energy and exergy efficiencies. Results showed that using char or activated char catalysts increases the heating value of the gas while reducing its tar concentration. Moreover, the process benefits thermodynamically (i.e. less exergy is destroyed) from low gasification temperatures and high reforming temperatures. Simulations indicate that a tarless gas with a lower heating value of more than 8 MJ/Nm3 can be produced from gasification at 1023K with an equivalence ratio of 0.15 and subsequent reforming at 1123K with a residence time in the catalyst bed of 1 second.",
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An energy and exergy analysis of biomass gasification integrated with a char-catalytic tar reforming system. / Buentello-Montoya, David; Zhang, Xiaolei.

In: Energy and Fuels, Vol. 33, No. 9, 19.09.2019, p. 8746-8757.

Research output: Contribution to journalArticle

TY - JOUR

T1 - An energy and exergy analysis of biomass gasification integrated with a char-catalytic tar reforming system

AU - Buentello-Montoya, David

AU - Zhang, Xiaolei

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N2 - Adequate tar removal is a recurrent challenge for biomass gasification. Materials such as char and activated char are promising catalysts for tar reforming because of their activity, inexpensiveness and constant production during gasification. Although the behaviour of char and activated char as catalyst has been previously studied, an evaluation of the thermodynamic efficiencies of the tar reforming process using char as a catalyst still lacking. This work analyses the performance of a two-stage system, where gasification is followed by tar reforming using char catalysts. For the study, a model based in a combination of equilibrium thermodynamics and chemical kinetics was developed. The first stage, where gasification occurs, was simulated with a thermodynamic equilibrium model. Gasification equilibrium models available in literature only predict the fractions of H2, CO, CO2 and CH4; the model developed for this work also predicts the formation of three model tars with different characteristics (benzene, toluene and naphthalene), providing information on the stability of formed tars. The second stage, simulated using kinetics from literature, consists on reforming the tars with catalysts made of residual char. The effects of the reactor temperature, equivalence ratio, and residence time were assessed via the gas quality, based on the gas lower heating value and tar concentration, and process efficiency, based on the energy and exergy efficiencies. Results showed that using char or activated char catalysts increases the heating value of the gas while reducing its tar concentration. Moreover, the process benefits thermodynamically (i.e. less exergy is destroyed) from low gasification temperatures and high reforming temperatures. Simulations indicate that a tarless gas with a lower heating value of more than 8 MJ/Nm3 can be produced from gasification at 1023K with an equivalence ratio of 0.15 and subsequent reforming at 1123K with a residence time in the catalyst bed of 1 second.

AB - Adequate tar removal is a recurrent challenge for biomass gasification. Materials such as char and activated char are promising catalysts for tar reforming because of their activity, inexpensiveness and constant production during gasification. Although the behaviour of char and activated char as catalyst has been previously studied, an evaluation of the thermodynamic efficiencies of the tar reforming process using char as a catalyst still lacking. This work analyses the performance of a two-stage system, where gasification is followed by tar reforming using char catalysts. For the study, a model based in a combination of equilibrium thermodynamics and chemical kinetics was developed. The first stage, where gasification occurs, was simulated with a thermodynamic equilibrium model. Gasification equilibrium models available in literature only predict the fractions of H2, CO, CO2 and CH4; the model developed for this work also predicts the formation of three model tars with different characteristics (benzene, toluene and naphthalene), providing information on the stability of formed tars. The second stage, simulated using kinetics from literature, consists on reforming the tars with catalysts made of residual char. The effects of the reactor temperature, equivalence ratio, and residence time were assessed via the gas quality, based on the gas lower heating value and tar concentration, and process efficiency, based on the energy and exergy efficiencies. Results showed that using char or activated char catalysts increases the heating value of the gas while reducing its tar concentration. Moreover, the process benefits thermodynamically (i.e. less exergy is destroyed) from low gasification temperatures and high reforming temperatures. Simulations indicate that a tarless gas with a lower heating value of more than 8 MJ/Nm3 can be produced from gasification at 1023K with an equivalence ratio of 0.15 and subsequent reforming at 1123K with a residence time in the catalyst bed of 1 second.

KW - thermodynamic equilibrium model

KW - tar reforming

KW - char catalyst

KW - gasification

KW - exergy analysis

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DO - 10.1021/acs.energyfuels.9b01808

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SP - 8746

EP - 8757

JO - Energy and Fuels

T2 - Energy and Fuels

JF - Energy and Fuels

SN - 0887-0624

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