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Introduction At high temperatures CO 2 is known to dissociate into CO and O. A prototype unit using only solar energy has achieved a 4-6 mole percent CO conversion from CO 2 . The prototype device was modeled using two different modeling programs (PCGC-3 and Fluent). Objectives - PowerPoint PPT Presentation
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Modeling the Direct Solar Conversion of COModeling the Direct Solar Conversion of CO22 to CO to CO
Ralph Price, David Morse, Steven Hardy, Thomas FletcherRalph Price, David Morse, Steven Hardy, Thomas FletcherBrigham Young University, Provo, UTBrigham Young University, Provo, UTScott HillScott Hill Reed JensenReed Jensen
Combustion Resources, Provo, UTCombustion Resources, Provo, UT Renewable Energy Corporation, Los Alamos, NMRenewable Energy Corporation, Los Alamos, NM
Objectives Used Fluent and PCGC-3 to predict the following:
Flow profiles
Temperature profiles
Reaction kinetics
Reaction mechanisms
Thermodynamic equilibrium
Photolysis reaction
Prototype Apparatus
Converter in sun 6 m2 solar mirrors
Silver solar converter 8 cm zirconia rod
Prototype Description Mirrors focus sunlight into
converter.
Zirconia rod in converter is heated by sunlight to
approximately 2350°C.
CO2 stream is passed over hot rod causing CO2 to dissociate into CO and O2.
Product stream (4-6 mole percent CO) is cooled quickly.
CO is separated and used in water-gas shift reaction.
Fluent Profiles
Predicted temperature Predicted CO mole profile with reactions fraction profile
Predicted radially- Predicted velocity averaged temperature profile versus axial distance
Introduction At high temperatures CO2 is known to dissociate into CO and O.
A prototype unit using only solar energy has achieved a 4-6 mole percent CO
conversion from CO2.
The prototype device was modeled using two different modeling
programs (PCGC-3 and Fluent).
PCGC-3 Profiles
Predicted temperature Predicted CO mole profile with reactions fraction profile
Predicted radially- Predicted CO mole averaged temperature fraction from versus axial distance photolysis
Conclusions Fluent model accurately
predicted experimental CO conversion.
PCGC-3 model was accurate in modeling formation of CO, but not cooling.
Residence time and temperatures in the throat
were too low to permit significant photolysis.
The formation of CO occurs only in the throat area and not upstream of the rod.
Solar conversion of CO2 to CO has the potential to provide a useable fuel from a CO2 stream.
ACERC
AcknowledgementsThis work was sponsored by
Renewable Energy Corporation Los Alamos,
NM
Elementary Reactions
The following reversible elementary reactions are known to occur in the converter.
CO2 + M CO + O + M
CO2 + O CO + O2
O2 + M O + O + M
CO2 + hν CO + O (photolysis)
Reaction Kinetics and Equilibrium
Parameters were found for the equation:
k=A*Tb*exp(-Ea/RT)
Reaction rate parameters
Equilibrium species fractions
1.0
0.8
0.6
0.4
0.2
0.0
Mol
e F
ract
ion
300028002600240022002000180016001400
Temperature (K)
CO2 O2 O CO