Pressurized calcium looping in the presence of steam in a spout-fluidized-bed reactor with DFT analysis

Calcium looping is a high-temperature solid-looping process for CO2 capture, exploiting cyclical carbonation of CaO. Previous work investigating the effects of steam on the carbonation reaction has produced conflicting results, with the majority of work conducted using thermogravimetric analyzers (T...

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Bibliographic Details
Published in:Fuel processing technology 2018-01, Vol.169, p.24-41
Main Authors: Fan, Yaming, Yao, Joseph G., Zhang, Zili, Sceats, Mark, Zhuo, Yuqun, Li, Liangliang, Maitland, Geoffrey C., Fennell, Paul S.
Format: Article
Language:English
Subjects:
Adsorption
Analyzers
Calcium
Calcium looping
Calcium oxide
Carbon sequestration
Carbonation
Computational chemistry
Computer simulation
Density functional theory
Fluidized bed
Fluidized beds
Kinetics
Molecular chains
Pressure
Reaction kinetics
Reactors
Steam
Surface chemistry
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Summary:Calcium looping is a high-temperature solid-looping process for CO2 capture, exploiting cyclical carbonation of CaO. Previous work investigating the effects of steam on the carbonation reaction has produced conflicting results, with the majority of work conducted using thermogravimetric analyzers (TGA). Here, pressurized carbonation kinetics in the presence of steam in a 3kWe pressurized spout-fluidized bed reactor, gives a rigorous insight into the effects of steam. Pseudo-intrinsic kinetics were determined using an effectiveness factor model along with activation energies and kinetic expressions. The mechanism in which steam promotes CO2 adsorption on the surface of CaO was investigated using density functional theory (DFT). The molecular-scale changes on the CaO surface owing to the presence of steam compared to the base case of CO2 adsorption on a ‘clean’ (without steam) surface were simulated with the Cambridge Serial Total Energy Package (CASTEP) software. The results suggest that steam promotes CO2 adsorption via the formation of surface OH groups on the CaO surface. •This is the first article on the effects of pressure on the CaO-CO2 reaction in the presence of steam inside a reactor.•The presence of steam improves carbonation kinetics.•This is the first time DFT theory has been applied to the CaO-CO2 reaction in the presence of steam.•How steam improves carbonation rate is explained by a surface model.
ISSN:0378-3820
1873-7188
DOI:10.1016/j.fuproc.2017.09.006