Selection of Oxygen Carriers for Chemical-Looping Combustion

Adánez, Juan; Diego, Luis F. de; Garcı́a-Labiano, F.; Gayán, Pilar; Abad, Alberto; Palacios, J.M.

doi:10.1021/ef0301452

Cited by 680 publications

(507 citation statements)

References 12 publications

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“…The active metal oxides used in this study are nickel-, copper-, and iron-oxides, which have been widely suggested as the most promising OC candidates for CLC (e.g., nickel [20][21][22][23], copper [16,20,23,24], and iron [20,25,26]). Important physical and chemical properties of these metal oxides are summarized in Table 1.…”

Section: Oc Designmentioning

confidence: 99%

Design of a rotary reactor for chemical-looping combustion. Part 2: Comparison of copper-, nickel-, and iron-based oxygen carriers

Zhao

Ghoniem

2014

Fuel

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Chemical-looping combustion (CLC) is a novel and promising option for several applications including carbon capture (CC), fuel reforming, H 2 generation, etc. Previous studies demonstrated the feasibility of performing CLC in a novel rotary design with micro-channel structures. Part 1 of this series studied the fundamentals of the reactor design and proposed a comprehensive design procedure, enabling a systematic methodology of designing and evaluating the rotary CLC reactor with different OCs and operating conditions. This paper presents the application of the methodology to the designs with three commonly used OCs, i.e., copper, nickel, and iron.The physical properties and the reactivities of the three OCs are compared at operating conditions suitable for the rotary CLC. Nickel has the highest reduction rate, but relatively slow oxidation reactivity while the iron reduction rate is most sensitive to the fuel concentration. The design parameters and the operating conditions for the three OCs are selected, following the  Corresponding author. Tel.: +1 617 253 2295. E-mail address: ghoniem@mit.edu (A.F. Ghoniem) 2 strategies proposed in Part 1, and the performances are evaluated using a one-dimensional plugflow model developed previously. The simulations show that for all OCs, complete fuel conversion and high carbon separation efficiency can be achieved at periodic stationary state with reasonable operational stabilities. The nickel-based design includes the smallest dimensions because of its fast reduction rate. The operation of nickel case is mainly limited to the slow oxidation rate, and hence a relatively large share of air sector is used. The iron-based design has the largest size, due to its slow reduction reactivity near the exit or in the fuel purge sector where the fuel concentration is low. The gas flow temperature increases monotonically for all the cases, and is mainly determined by the solid temperature. In the periodic state, the local temperature variation is within 40K and the thermal distortion is limited. The design of the rotary CLC is also scaled to different pressures and inlet temperatures. The method of scaling is discussed and desirable operational performances are obtained.

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Section: Oc Designmentioning

confidence: 99%

Design of a rotary reactor for chemical-looping combustion. Part 2: Comparison of copper-, nickel-, and iron-based oxygen carriers

Zhao

Ghoniem

2014

Fuel

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“…Figure 2 shows the reactivity data obtained during the first redox cycle in the TGA with both oxygen carriers, NiO18-Al and NiO21-Al, at 1223 K using 15 vol. % of CH 4 , H 2 or CO as fuels. As can be seen, in the case of NiO18-Al, the reduction of the oxygen carrier particles proceeded in two stages.…”

Section: Kinetic Modelmentioning

confidence: 99%

“…The major advantage of this process is that heat needed for converting CH 4 to H 2 is obtained without costly oxygen production and without mixing the air with carbon-containing fuel gases.…”

Section: Introductionmentioning

confidence: 99%

Reduction and oxidation kinetics of nickel-based oxygen-carriers for chemical-looping combustion and chemical-looping reforming

Dueso

Ortiz

Abad

et al. 2012

Chemical Engineering Journal

168

114

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The kinetics of reduction with CH 4 , H 2 and CO and oxidation with O 2 of two NiO-based oxygen carriers prepared by impregnation, NiO18-Al and NiO21-Al, for chemicallooping combustion (CLC) and chemical-looping reforming (CLR) was investigated in this work. The experimental tests were carried out in a thermogravimetric analyzer using different reacting gas concentrations (5-20 vol. % for CH 4 , 5-50 vol. % for H 2 and CO and 5-21 vol. % for O 2 ) and temperatures (1073-1223 K). The reduction stage using both materials proceeded in two steps: a first period of high reactivity attributed to the presence of free NiO and then a low reactivity period that corresponded to NiAl 2 O 4 reduction. Therefore, the kinetic parameters for NiO and NiAl 2 O 4 reduction were determined separately for each oxygen carrier and each reacting gas. An empirical linear model was developed to describe NiO reduction. The solid conversion was a function of the fuel concentration and NiO content in the solid. The effect of temperature was low (E a ~ 5 kJ mol -1 ) although a chemical reaction rate controlled by diffusional processes was dismissed. The shrinking core model for spherical grain 2 geometry was used to obtain the kinetic parameters of the NiAl 2 O 4 reduction working with both NiO-based oxygen carriers. Chemical reaction control was assumed for NiO18-Al whereas diffusion through product layer was also considered when NiO21-Al was used as oxygen carrier. 82-472 kJ mol -1 activation energies were obtained with NiO18-Al particles. The activation energies were 237 and 373 kJ mol -1 for the kinetic constant and 200-281 kJ mol -1 for the diffusion coefficient, respectively, in the case of NiO21-Al oxygen carrier. Reduction reaction of NiO21-Al with CO was extremely slow and the kinetic parameters were obtained for comparison purposes with chemical control of the reaction rate. In this case, the reaction order was 1 and the activation energy 89 kJ mol -1 . The combined model for consecutive reduction of NiO and NiAl 2 O 4 in the NiO18-Al particles with the kinetic parameters obtained in this work predicted adequately the experimental results. The oxidation step of both oxygen carriers was fast and complete until reaching the initial condition. An empiric linear model, which assumes a linear relation between time and conversion, was developed to determine the kinetics of Ni oxidation. The reaction order of oxidation was about 0.8 for NiO18-Al and NiO21-Al and the activation energies were low, 22 kJ mol -1 in both cases. 

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“…These oxygen carriers have shown adequate reactivity under atmospheric [10][11][12] and pressurized [13] conditions and high reactivity with CO and H 2 , and do not present thermodynamic limitations to fully convert CH 4 4 can be formed as a reduced compound and also achieve complete combustion of gas to CO 2 and H 2 O [14][15][16][17]. Thus, the oxygen transport capacity of the oxygen carrier is increased three times in comparison with the Fe 2 O 3 -Fe 3 O 4 redox couple.…”

Section: Introductionmentioning

confidence: 99%

Kinetic determination of a highly reactive impregnated Fe2O3/Al2O3 oxygen carrier for use in gas-fueled Chemical Looping Combustion

Cabello

Abad

Garcı́a-Labiano

et al. 2014

Chemical Engineering Journal

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114

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The objective of this work was to determine the kinetic parameters for reduction and oxidation reactions of a highly reactive Fe-based oxygen carrier for use in chemical looping combustion (CLC) of gaseous fuels containing CH 4 , CO and/or H 2 , e.g. natural gas, syngas and PSA-off gas. The oxygen carrier was prepared by impregnation of iron on alumina. The effect of both the temperature and gas concentration was analysed in a thermogravimetric analyser (TGA).The grain model with uniform conversion in the particle and reaction in grains following the shrinking core model (SCM) was used for kinetics determination. It was 2 assumed that the reduction reactions were controlled by two different resistances: the reaction rate was controlled by chemical reaction in a first step, whereas the mechanism that controlled the reactions at higher conversion values was diffusion through the product layer around the grains. Furthermore, it was found that the reduction reaction mechanism was based on the interaction of Fe 2 O 3 with Al 2 O 3 in presence of the reacting gases to form FeAl 2 O 4 as the only stable Fe-based phase. The reaction order values found for the reducing gases were 0.25, 0.3 and 0.6 for CH 4 , H 2 and CO, respectively, and the activation energy took values of between 8 kJ mol -1 (for H 2 ) and 66 kJ mol -1 (for CH 4 ). With regard to oxidation kinetics, the reacting model assumed a reaction rate that was only controlled by chemical reaction. Values of 0.9 and 23 kJ mol -1 were found for reaction order and activation energy, respectively.Finally, the solids inventory needed in a CLC system was also estimated by considering kinetic parameters. The total solids inventory in the CLC unit took a minimum value of 150 kg MW -1 for CH 4 combustion, which is a low value when compared to those of other Fe-based materials found in the literature.

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Selection of Oxygen Carriers for Chemical-Looping Combustion

Cited by 680 publications

References 12 publications

Design of a rotary reactor for chemical-looping combustion. Part 2: Comparison of copper-, nickel-, and iron-based oxygen carriers

Design of a rotary reactor for chemical-looping combustion. Part 2: Comparison of copper-, nickel-, and iron-based oxygen carriers

Reduction and oxidation kinetics of nickel-based oxygen-carriers for chemical-looping combustion and chemical-looping reforming

Kinetic determination of a highly reactive impregnated Fe2O3/Al2O3 oxygen carrier for use in gas-fueled Chemical Looping Combustion

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