Fluidized Bed Conversion_a Challenge Of Simulation Presentation)
This document was uploaded by user and they confirmed that they have the permission to share it. If you are author or own the copyright of this book, please report to us by using this DMCA report form. Report DMCA
Overview
Download & View Fluidized Bed Conversion_a Challenge Of Simulation Presentation) as PDF for free.
More details
- Words: 1,064
- Pages: 32
CD-Laboratory for Chemical Engineering at High Temperatures
Fluidized Bed Conversion – A Challenge for Simulation Franz Winter
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Fluidized Bed Reactors gas – solid contact
Grace et al. 1997
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Circulating Fluidized Bed Reactors complex two-phase flow
Horio et al. 1997
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Fluidized Bed Boilers
Kaiser et al. 2004
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Solid Fuel Combustion complex chemistry 200
4
160 3
120
NO
N2O 2
Char Combustion
HCN
CO2
80
1 40
0
0 0
200
400
600
800
1000
1200
1400
1600
1800
time [s]
Institute of Chemical Engineering
2000
CD-Laboratory for Chemical Engineering at High Temperatures
Solid Fuel Combustion complex chemistry NO
NCO hom.
hom. hom. HCN
N2O NO hom.
hom. TAR - N
N2O NO
hom.
hom.
hom.
N2O
hom.
NH3
N2
hom. hom. het. VOLATILE N
N2O NO
Char Surface het. CHAR - N
hom.
NO hom. HCN hom.
FUEL - N
hom.
NCO
hom.
hom. NH3
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Solid Fuel Combustion CO oxidation - main reactions • CO – Oxidation: – Initiation H2O O2 + M – Propagation CO + OH – chain H + O2 O + H2O – Termination CO + O H + O2 + M
= =
OH + H 2O+M
=
CO2 + H
= =
OH + O 2 OH
= =
CO2 HO2 + M
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures CH4 +O, +H, +OH
Solid Fuel Combustion
+O
+H
+HO2
CH3
CH3O +H +O
CH4 oxidation reaction paths
+OH
+O CH2O
CH2(S)
C2H6 +O, +H, +OH +O2
+H
+O2
+N2 +H
+O HCO
+O
C2H5
CH
CH2
+O2 +O2 +O2 +O2 CH2CHO CO
C2H4
+O
+OH
CH2CO
+O2 CO2
C2H3
+H
+H
+O2
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Chemistry – problems with different time scales
time scales for chemical reactions (10-10s to >1s )
Warnatz et al. 2001
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Chemistry – problems with different time scales are there two or more different scales (time) of the independent variable on which the dependent variables are changing:
=> stiffness occures.
example of an instability encountered in integrating a stiff equation (schematic).
=> implicit integration methods Press et al. 1992
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Model for Ash Deposition Aim: Prediction of the Location of Ash Deposition
Müller et al. 2003, 17-FBC Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Model for Ash Deposition - Turbulence: k-ε model - Radiative heat transfer: discrete ordinate model - Turbulence chemistry interaction: Eddy-Dissipation Combustion Model - Software: Fluent
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Model for Ash Deposition Chemistry • 4-Step Approach: CxHyOz + aO2
=
CxHyOz + eH2O=
bCO + cH2 + dH2O fCO + gH2 + hH2O
H2 + 0.5O2
=
H2O
CO + H2O
=
CO2 + H2
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Model for Ash Deposition Meshing: structured - unstructured
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Model for Ash Deposition Mass flows: bed and freeboard, fuel split
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Model for Ash Deposition CO Distribution
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Model for Ash Deposition Temperature Distribution
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Model for Ash Deposition Ash Particle Hitting Maps
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: Semi-Empirical Models
Aims: - Prediction of NO Emissions - Effect of Particle Size
Kallio et al. 2004, 11-Fluidization Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: Semi-Empirical Models - Flow and mixing simplified - Zones defined
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: Semi-Empirical Models NO Profiles comparison with measurements
Different models considered: A – Attrition, SF – Sec. Fragmentation
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Simulation of a Single Bubble Visual observations of bubble flow cold conditions sand bed
Peirano et al. 2002, Powder Technology Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Simulation of a Single Bubble Eulerian model: - gas-phase (continuous phase): Turbulence: k-ε model - particle-phase (discrete phase): kinetic theory of granular flow
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Simulation of a Single Bubble
Calculation time: - 500 hours on a CRAY 90 for 20 s of real time with 2.3x105 nodes
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Simulation of a Single Bubble
Calculated particle volume fraction
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Simulation of a Single Bubble Calculated and measured pressure spectra for high pressure drop distributer
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Simulation of a Single Bubble Calculated and measured pressure spectra for low pressure drop distributer
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Simulation of a Single Bubble
Time averaged gas velocity field for low pressure drop distributer
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Conclusions • The current status is: - CFD simulation of two-phase flow is very limited - Flow is simplified with semi-empirical zone models - Chemistry is simplified, reduced models are used - Heat transfer is simplified based on Nusselt number
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Conclusions • Future challenges are: - Simulation of full chemistry - Development of reduced mechanisms - CFD simulation of two-phase flow - Heat transfer models (based on local flow conditions)
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Thank you for your attention!
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Conference on Small-scale Combustion 18-20 November 2004, Vienna
www.semaco.co.at/dvv
Institute of Chemical Engineering
Fluidized Bed Conversion – A Challenge for Simulation Franz Winter
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Fluidized Bed Reactors gas – solid contact
Grace et al. 1997
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Circulating Fluidized Bed Reactors complex two-phase flow
Horio et al. 1997
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Fluidized Bed Boilers
Kaiser et al. 2004
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Solid Fuel Combustion complex chemistry 200
4
160 3
120
NO
N2O 2
Char Combustion
HCN
CO2
80
1 40
0
0 0
200
400
600
800
1000
1200
1400
1600
1800
time [s]
Institute of Chemical Engineering
2000
CD-Laboratory for Chemical Engineering at High Temperatures
Solid Fuel Combustion complex chemistry NO
NCO hom.
hom. hom. HCN
N2O NO hom.
hom. TAR - N
N2O NO
hom.
hom.
hom.
N2O
hom.
NH3
N2
hom. hom. het. VOLATILE N
N2O NO
Char Surface het. CHAR - N
hom.
NO hom. HCN hom.
FUEL - N
hom.
NCO
hom.
hom. NH3
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Solid Fuel Combustion CO oxidation - main reactions • CO – Oxidation: – Initiation H2O O2 + M – Propagation CO + OH – chain H + O2 O + H2O – Termination CO + O H + O2 + M
= =
OH + H 2O+M
=
CO2 + H
= =
OH + O 2 OH
= =
CO2 HO2 + M
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures CH4 +O, +H, +OH
Solid Fuel Combustion
+O
+H
+HO2
CH3
CH3O +H +O
CH4 oxidation reaction paths
+OH
+O CH2O
CH2(S)
C2H6 +O, +H, +OH +O2
+H
+O2
+N2 +H
+O HCO
+O
C2H5
CH
CH2
+O2 +O2 +O2 +O2 CH2CHO CO
C2H4
+O
+OH
CH2CO
+O2 CO2
C2H3
+H
+H
+O2
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Chemistry – problems with different time scales
time scales for chemical reactions (10-10s to >1s )
Warnatz et al. 2001
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Chemistry – problems with different time scales are there two or more different scales (time) of the independent variable on which the dependent variables are changing:
=> stiffness occures.
example of an instability encountered in integrating a stiff equation (schematic).
=> implicit integration methods Press et al. 1992
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Model for Ash Deposition Aim: Prediction of the Location of Ash Deposition
Müller et al. 2003, 17-FBC Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Model for Ash Deposition - Turbulence: k-ε model - Radiative heat transfer: discrete ordinate model - Turbulence chemistry interaction: Eddy-Dissipation Combustion Model - Software: Fluent
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Model for Ash Deposition Chemistry • 4-Step Approach: CxHyOz + aO2
=
CxHyOz + eH2O=
bCO + cH2 + dH2O fCO + gH2 + hH2O
H2 + 0.5O2
=
H2O
CO + H2O
=
CO2 + H2
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Model for Ash Deposition Meshing: structured - unstructured
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Model for Ash Deposition Mass flows: bed and freeboard, fuel split
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Model for Ash Deposition CO Distribution
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Model for Ash Deposition Temperature Distribution
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Model for Ash Deposition Ash Particle Hitting Maps
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: Semi-Empirical Models
Aims: - Prediction of NO Emissions - Effect of Particle Size
Kallio et al. 2004, 11-Fluidization Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: Semi-Empirical Models - Flow and mixing simplified - Zones defined
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: Semi-Empirical Models NO Profiles comparison with measurements
Different models considered: A – Attrition, SF – Sec. Fragmentation
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Simulation of a Single Bubble Visual observations of bubble flow cold conditions sand bed
Peirano et al. 2002, Powder Technology Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Simulation of a Single Bubble Eulerian model: - gas-phase (continuous phase): Turbulence: k-ε model - particle-phase (discrete phase): kinetic theory of granular flow
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Simulation of a Single Bubble
Calculation time: - 500 hours on a CRAY 90 for 20 s of real time with 2.3x105 nodes
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Simulation of a Single Bubble
Calculated particle volume fraction
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Simulation of a Single Bubble Calculated and measured pressure spectra for high pressure drop distributer
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Simulation of a Single Bubble Calculated and measured pressure spectra for low pressure drop distributer
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Example: CFD Simulation of a Single Bubble
Time averaged gas velocity field for low pressure drop distributer
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Conclusions • The current status is: - CFD simulation of two-phase flow is very limited - Flow is simplified with semi-empirical zone models - Chemistry is simplified, reduced models are used - Heat transfer is simplified based on Nusselt number
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Conclusions • Future challenges are: - Simulation of full chemistry - Development of reduced mechanisms - CFD simulation of two-phase flow - Heat transfer models (based on local flow conditions)
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Thank you for your attention!
Institute of Chemical Engineering
CD-Laboratory for Chemical Engineering at High Temperatures
Conference on Small-scale Combustion 18-20 November 2004, Vienna
www.semaco.co.at/dvv
Institute of Chemical Engineering
Related Documents
Fluidized Bed Conversion_a Challenge Of Simulation Presentation)
November 2019 6
Fluidized Bed
June 2020 7
Fluidized Bed Reactor
June 2020 6
