Experiment and rate equation modeling of Fe oxidation kinetics in chemical looping combustion

Bao, Jinhua; Li, Zhenshan; Sun, Hongming; Cai, Ningsheng

doi:10.1016/j.combustflame.2012.12.010

Cited by 33 publications

(33 citation statements)

References 37 publications

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“…The CO, CO 2 , O 2 concentrations with time and the oxygen yield γ o with mass based conversion of ilmenite ω for cycle1,5,10,20,30,40 with ∼50 g raw ilmenite as the bed material.…”

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confidence: 99%

Promoting the Reduction Reactivity of Ilmenite by Introducing Foreign Ions in Chemical Looping Combustion

Bao

Cai

2013

Ind. Eng. Chem. Res.

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120

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A new kind of ilmenite oxygen carrier was prepared by impregnating the raw ilmenite particles with K 2 CO 3 , Na 2 CO 3 , or Ca(NO 3 ) 2 . The cyclic reduction reactivity of the new oxygen carrier was investigated in a fluidized bed reactor. It has been found that the addition of foreign ions can significantly promote the reduction reactivity of ilmenite. The effect of foreign ions on enhancing the reduction reactivity of ilmenite is in the sequence of K + > Na + > Ca 2+ . The effect of the loading amount of K + on increasing the ilmenite reactivity is in the sequence of 15 wt % K + > 10 wt % K + > 5 wt % K + . The reduction reactivity of the ilmenite impregnated with 15 wt % K + can be improved ∼8 times faster than that of the activated raw ilmenite. This reactivity reaches up to the same level of the synthetic Ni-based carrier. The modified ilmenite obtains a porous structure caused by the migration of K or Na ions. One possible explanation for the reactivity enhancement of ilmenite with the addition of foreign ions, especially K + and Na + , is the migration of K + or Na + . Another explanation may be the active principle of the alkali-rich phase formed between the foreign ions and titanium iron oxides, that is, K 1.46 Ti 7.2 Fe 0.8 O 16 or Na 2 Fe 2 Ti 6 O 16 . This study proves that the reduction reactivity of the natural ilmenite can be promoted significantly by impregnating ilmenite with K + .

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“…The CO, CO 2 , O 2 concentrations with time and the oxygen yield γ o with mass based conversion of ilmenite ω for cycle1,5,10,20,30,40 with ∼50 g raw ilmenite as the bed material.…”

mentioning

confidence: 99%

Promoting the Reduction Reactivity of Ilmenite by Introducing Foreign Ions in Chemical Looping Combustion

Bao

Cai

2013

Ind. Eng. Chem. Res.

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120

126

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“…It exhibited that there was an activation process of the lean iron ore. The activation period and its mechanism have been found and investigated in previous literatures [41][42][43][44]. This was attributed to the porosity increase of oxygen carrier particles in the initial cyclic reactions.…”

Section: Investigation On Multi Cyclesmentioning

confidence: 89%

Performance Evaluation of a Chinese Lean Iron Ore as the Oxygen Carrier in Multi and Short-Time Redox Cycles

Wang

et al. 2018

Applied Sciences

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Abstract:The performance of a Chinese lean iron ore as the oxygen carrier in chemical looping combustion was investigated in a fixed bed reactor. Considering the short contact time between the fuel gas and oxygen carrier in the sub-pilot experimental setup, the short injection time of CO was employed in the reactor to simulate this event. The injection time of CO was set to 60 s, 50 s and 40 s respectively, to investigate its effects on the reactivity of the oxygen carrier. A total of 100 cyclic reactions under each condition were carried out to test the reactivity stability of the oxygen carrier. The oxygen carriers prior and after reactions were characterized using SEM, XRD and BET. Results showed that there was an activation process of the reactivity during initial cycles. The extension of the reaction time was beneficial to the diffusion of CO into the oxygen carrier and could improve the conversion of CO. Also, it could form larger pore volumes for gas diffusion in the oxygen carrier. However, it led to the formation of the Fe 2 SiO 4 and severe sintering on the surface, which was harmful to the stability of the oxygen carrier's reactivity.

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“…By using atomic force microscopy (AFM) and a single crystal sample, it has been proposed in several studies that during the gas-solid reaction process, the solid product grows as dispersed, three-dimensional islands rather than a uniform continuous product layer [25,26,27,28]. All islands show similar shape, which can be explained by the Wuff construction theory [36], and the size of islands increases with the oxidation reaction time [25]. Recently, a rate equation theory of metal oxidation was developed to calculate the solid product nucleation and growth rates [25].…”

Section: Mathematical Modelmentioning

confidence: 99%

“…The calculated results showed that the presence of oxygen vacancy on the surface exhibited a strong chemical reactivity towards the dissociation of O 2 . Recently, it was found that the solid product showed dispersed and three-dimensional morphology on the solid reactant surface [25,26,27,28]. In addition, a rate equation theory for Fe oxidation was developed to describe the nucleation and growth process of the solid product [25].…”

Section: Introductionmentioning

confidence: 99%

“…Recently, it was found that the solid product showed dispersed and three-dimensional morphology on the solid reactant surface [25,26,27,28]. In addition, a rate equation theory for Fe oxidation was developed to describe the nucleation and growth process of the solid product [25]. However, the above research at microscopic scale did not consider the steps involved at the particle scale, such as particle structure change, external mass transfer, and internal mass transfer, thus could not explain the phenomenon at the macroscopic scale and the controlling mechanism of the reaction.…”

Section: Introductionmentioning

confidence: 99%

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A Multiscale Model of Oxidation Kinetics for Cu-Based Oxygen Carrier in Chemical Looping with Oxygen Uncoupling

Wang

Cai

2019

Materials

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Copper oxide is one of the promising oxygen carrier materials in chemical looping with oxygen uncoupling (CLOU) technology, cycling between Cu2O and CuO. In this study, a multiscale model was developed to describe the oxidation kinetics of the Cu-based oxygen carrier particle with oxygen, including surface, grain, and particle scale. It was considered that the solid product grows with the morphology of disperse islands on the grain surface, and O2 contacts with two different kinds of grain surfaces in the grain scale model, that is, Cu2O surface (solid reactant surface) and CuO surface (solid product surface). The two-stage behavior of the oxidation reaction of the Cu-based oxygen carrier was predicted successfully using the developed model, and the model results showed good agreement with experimental data in the literature. The effects of oxygen partial pressure, temperature, and particle structure on the oxidation performance were analyzed. The modeling results indicated that the transition of the conversion curve occurs when product islands cover most part of the grain surface. The oxygen partial pressure and particle structure have an obvious influence on the duration time of the fast reaction stage. Furthermore, the influence of the external mass transfer and the change of effectiveness factor during the oxidation reaction process were discussed to investigate the controlling step of the reaction. It was concluded that the external mass transfer step hardly affects the reaction performance under the particle sizes normally used in CLOU. The value of the effectiveness factor increases as the reaction goes by, which means the chemical reaction resistance at grain scale increases resulting from the growing number of product islands on the grain surface.

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Experiment and rate equation modeling of Fe oxidation kinetics in chemical looping combustion

Cited by 33 publications

References 37 publications

Promoting the Reduction Reactivity of Ilmenite by Introducing Foreign Ions in Chemical Looping Combustion

Promoting the Reduction Reactivity of Ilmenite by Introducing Foreign Ions in Chemical Looping Combustion

Performance Evaluation of a Chinese Lean Iron Ore as the Oxygen Carrier in Multi and Short-Time Redox Cycles

A Multiscale Model of Oxidation Kinetics for Cu-Based Oxygen Carrier in Chemical Looping with Oxygen Uncoupling

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