Investigation on the decrease in the reduction rate of oxygen carriers for chemical looping combustion

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Uittreksel

Copper oxide on alumina is often used as oxygen carrier for chemical looping combustion owing to its very high reduction rates at lower temperatures and its very good mechanical and chemical stability at not too high temperatures. In this work, the redox kinetics of CuO/Al2O3 have been measured and analysed with many consecutive reduction (50% H2, 50% N2) and oxidation (air) cycles at different temperatures using thermogravimetric analysis. In all the redox cycles, a cyclic steady state in the redox kinetics is observed after several redox cycles, where a sudden decrease in the reaction rate is observed after a certain solids conversion, typically around 75%, depending in particular on the operating temperature. Models developed in the literature fail at predicting these redox kinetics and they are mostly shrinking core/grain type models with an ad-hoc combination and modification of chemical reaction and gas phase diffusion. The oxygen carrier was characterized in detail with different techniques including N2 physisorption, XRD and SEM-EDX to investigate morphological changes in the particle over the redox cycles in order to better understand why all the models developed in literature fail. After the study we can conclude that i) gas-phase diffusion is not playing a limiting role on the redox kinetics despite significant morphological changes in the particle; ii) migration of copper from the inside of the particle to the surface of the particle does not occur or does not influence the kinetics; iii) oxygen uncoupling is not influencing the kinetics being equally fast for Cu2O and CuO, although it can be significant for the final maximum particle conversion; iv) solid phase oxygen diffusion limitations may be responsible for the observed drop in reaction rate.
TaalEngels
Pagina's429–439
Aantal pagina's11
TijdschriftPowder Technology
Volume301
DOI's
StatusGepubliceerd - nov 2016

Vingerafdruk

Oxygen
Kinetics
Reaction rates
Gases
Temperature
Physisorption
Copper oxides
Aluminum Oxide
Mechanical stability
Chemical stability
Oxidation-Reduction
Thermogravimetric analysis
Copper
Energy dispersive spectroscopy
Chemical reactions
Alumina
Oxidation
Scanning electron microscopy
Air

Citeer dit

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title = "Investigation on the decrease in the reduction rate of oxygen carriers for chemical looping combustion",
abstract = "Copper oxide on alumina is often used as oxygen carrier for chemical looping combustion owing to its very high reduction rates at lower temperatures and its very good mechanical and chemical stability at not too high temperatures. In this work, the redox kinetics of CuO/Al2O3 have been measured and analysed with many consecutive reduction (50{\%} H2, 50{\%} N2) and oxidation (air) cycles at different temperatures using thermogravimetric analysis. In all the redox cycles, a cyclic steady state in the redox kinetics is observed after several redox cycles, where a sudden decrease in the reaction rate is observed after a certain solids conversion, typically around 75{\%}, depending in particular on the operating temperature. Models developed in the literature fail at predicting these redox kinetics and they are mostly shrinking core/grain type models with an ad-hoc combination and modification of chemical reaction and gas phase diffusion. The oxygen carrier was characterized in detail with different techniques including N2 physisorption, XRD and SEM-EDX to investigate morphological changes in the particle over the redox cycles in order to better understand why all the models developed in literature fail. After the study we can conclude that i) gas-phase diffusion is not playing a limiting role on the redox kinetics despite significant morphological changes in the particle; ii) migration of copper from the inside of the particle to the surface of the particle does not occur or does not influence the kinetics; iii) oxygen uncoupling is not influencing the kinetics being equally fast for Cu2O and CuO, although it can be significant for the final maximum particle conversion; iv) solid phase oxygen diffusion limitations may be responsible for the observed drop in reaction rate.",
author = "{San Pio Bordeje}, M.A. and I. Roghair and F. Gallucci and {van Sint Annaland}, M.",
year = "2016",
month = "11",
doi = "10.1016/j.powtec.2016.06.031",
language = "English",
volume = "301",
pages = "429–439",
journal = "Powder Technology",
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publisher = "Elsevier",

}

Investigation on the decrease in the reduction rate of oxygen carriers for chemical looping combustion. / San Pio Bordeje, M.A.; Roghair, I.; Gallucci, F.; van Sint Annaland, M.

In: Powder Technology, Vol. 301, 11.2016, blz. 429–439.

Onderzoeksoutput: Bijdrage aan tijdschriftTijdschriftartikelAcademicpeer review

TY - JOUR

T1 - Investigation on the decrease in the reduction rate of oxygen carriers for chemical looping combustion

AU - San Pio Bordeje,M.A.

AU - Roghair,I.

AU - Gallucci,F.

AU - van Sint Annaland,M.

PY - 2016/11

Y1 - 2016/11

N2 - Copper oxide on alumina is often used as oxygen carrier for chemical looping combustion owing to its very high reduction rates at lower temperatures and its very good mechanical and chemical stability at not too high temperatures. In this work, the redox kinetics of CuO/Al2O3 have been measured and analysed with many consecutive reduction (50% H2, 50% N2) and oxidation (air) cycles at different temperatures using thermogravimetric analysis. In all the redox cycles, a cyclic steady state in the redox kinetics is observed after several redox cycles, where a sudden decrease in the reaction rate is observed after a certain solids conversion, typically around 75%, depending in particular on the operating temperature. Models developed in the literature fail at predicting these redox kinetics and they are mostly shrinking core/grain type models with an ad-hoc combination and modification of chemical reaction and gas phase diffusion. The oxygen carrier was characterized in detail with different techniques including N2 physisorption, XRD and SEM-EDX to investigate morphological changes in the particle over the redox cycles in order to better understand why all the models developed in literature fail. After the study we can conclude that i) gas-phase diffusion is not playing a limiting role on the redox kinetics despite significant morphological changes in the particle; ii) migration of copper from the inside of the particle to the surface of the particle does not occur or does not influence the kinetics; iii) oxygen uncoupling is not influencing the kinetics being equally fast for Cu2O and CuO, although it can be significant for the final maximum particle conversion; iv) solid phase oxygen diffusion limitations may be responsible for the observed drop in reaction rate.

AB - Copper oxide on alumina is often used as oxygen carrier for chemical looping combustion owing to its very high reduction rates at lower temperatures and its very good mechanical and chemical stability at not too high temperatures. In this work, the redox kinetics of CuO/Al2O3 have been measured and analysed with many consecutive reduction (50% H2, 50% N2) and oxidation (air) cycles at different temperatures using thermogravimetric analysis. In all the redox cycles, a cyclic steady state in the redox kinetics is observed after several redox cycles, where a sudden decrease in the reaction rate is observed after a certain solids conversion, typically around 75%, depending in particular on the operating temperature. Models developed in the literature fail at predicting these redox kinetics and they are mostly shrinking core/grain type models with an ad-hoc combination and modification of chemical reaction and gas phase diffusion. The oxygen carrier was characterized in detail with different techniques including N2 physisorption, XRD and SEM-EDX to investigate morphological changes in the particle over the redox cycles in order to better understand why all the models developed in literature fail. After the study we can conclude that i) gas-phase diffusion is not playing a limiting role on the redox kinetics despite significant morphological changes in the particle; ii) migration of copper from the inside of the particle to the surface of the particle does not occur or does not influence the kinetics; iii) oxygen uncoupling is not influencing the kinetics being equally fast for Cu2O and CuO, although it can be significant for the final maximum particle conversion; iv) solid phase oxygen diffusion limitations may be responsible for the observed drop in reaction rate.

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DO - 10.1016/j.powtec.2016.06.031

M3 - Article

VL - 301

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EP - 439

JO - Powder Technology

T2 - Powder Technology

JF - Powder Technology

SN - 0032-5910

ER -