Kinetics Analysis of Cu-Zr Oxygen Carrier for Chemical Looping Oxygen Production

doi:10.3724/SP.J.1077.2014.13321

Abstract

Abstract:

2 oxygen carrier was prepared by mechanical mixing. BET, SEM and XRD were used to analyze the specific surface area, surface morphology and phases of oxygen carrier. The phases of oxygen carrier are only CuO and ZrO₂. There is no agglomeration in the surface of oxygen carrier. The BET values increase with the increase of weight ratio of binder. The mechanism experiments were carried out in STA409PC thermal analyzer and the temperature programmed thermogravimetry was used to investigate the effects of gas flow, sample mass, heating rate and weight ratio of binder on reduction and oxidation reactions. The results show that the CuO/ZrO₂ oxygen carrier has high reactivity of releasing and adsorbing oxygen. When the gases flows are higher than 30 mL/min and sample mass is less than 10 mg, the reaction rates are not controlled by the internal and external diffusion through gas film around the particle. Besides the start and end points, all peaks of DTG curves of reduction-oxidation reactions move forward to high temperature with an increase heating rate. The time for overall conversion decreases with the increase of weight ratio of binder. Based on the experimental data, the kinetics of the CuO/ZrO₂ oxygen carrier was determined by the isoconversional model. The differences of distributed activation energy, calculated at different conversion ratios, are all very small. The reduction-oxidation reactions of CuO/ZrO₂oxygen carrier are one-step and the mechanism functions can be explained by nucleation and nuclei growth theory. The kinetics equations of reduction and oxidation reaction are]]>

Key words: chemical looping oxygen production, oxygen carrier, mechanism experiment, distributed activation energy, kinetic mechanism

CLC Number:

TQ174

WANG Kun, YU Qing-Bo, QIN Qin, LI Jiu-Chong, WANG Zhi-Mei. Kinetics Analysis of Cu-Zr Oxygen Carrier for Chemical Looping Oxygen Production[J]. Journal of Inorganic Materials, 2014, 29(3): 301-308.

Figures/Tables 11

References 27

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Number	Mechanisms	Symbol	f(α)	g(α)
1	1-dimensional diffusion	D₁	0.5α^-1	α²
2	2-dimensional diffusion	D₂	[-ln(1-α)]^-1	α+(1-α)ln(1-α)
3	3-dimensional diffusion (cylinder)	D₃	1.5[(1-α)^-^1/3-1]^-1	(1-(2/3)α)-(1-α)^2/3
4	3-dimensional diffusion (sphere)	D₄	1.5(1-α)^2/3[1-(1-α)^1/3]^-1	[1-(1-α)^1/3]²
5	Nucleation and nuclei growth (n=1)	A₁	1-α	-ln(1-α)
6	Nucleation and nuclei growth (n =1.5)	A_1.5	1.5(1-α)[-ln(1-α)]^1/3	[-ln(1-α)]^2/3
7	Nucleation and nuclei growth (n =2)	A₂	2(1-α)[-ln(1-α)]^1/2	[-ln(1-α)]^1/2
8	Nucleation and nuclei growth (n =3)	A₃	3(1-α)[-ln(1-α)]^2/3	[-ln(1-α)]^1/3
9	Phase boundary reaction (n =1)	R₁	(1-α)	α
10	Phase boundary reaction (n =2)	R₂	2(1-α)^1/2	1-(1-α)^1/2
11	Phase boundary reaction (n =3)	R₃	3(1-α)^2/3	1-(1-α)^1/3
12	Power low (n =1.5)	C_1.5	2(1-α)^3/2	(1-α)^-1/2
13	Power low (n =2)	C₂	(1-α)²	(1-α)^-1-1
14	Power low (n =3)	C₃	(1-α)³	0.5[(1-α)^-2-1]

Number	Mechanisms	Symbol	f(α)	g(α)
1	1-dimensional diffusion	D₁	0.5α^-1	α²
2	2-dimensional diffusion	D₂	[-ln(1-α)]^-1	α+(1-α)ln(1-α)
3	3-dimensional diffusion (cylinder)	D₃	1.5[(1-α)^-^1/3-1]^-1	(1-(2/3)α)-(1-α)^2/3
4	3-dimensional diffusion (sphere)	D₄	1.5(1-α)^2/3[1-(1-α)^1/3]^-1	[1-(1-α)^1/3]²
5	Nucleation and nuclei growth (n=1)	A₁	1-α	-ln(1-α)
6	Nucleation and nuclei growth (n =1.5)	A_1.5	1.5(1-α)[-ln(1-α)]^1/3	[-ln(1-α)]^2/3
7	Nucleation and nuclei growth (n =2)	A₂	2(1-α)[-ln(1-α)]^1/2	[-ln(1-α)]^1/2
8	Nucleation and nuclei growth (n =3)	A₃	3(1-α)[-ln(1-α)]^2/3	[-ln(1-α)]^1/3
9	Phase boundary reaction (n =1)	R₁	(1-α)	α
10	Phase boundary reaction (n =2)	R₂	2(1-α)^1/2	1-(1-α)^1/2
11	Phase boundary reaction (n =3)	R₃	3(1-α)^2/3	1-(1-α)^1/3
12	Power low (n =1.5)	C_1.5	2(1-α)^3/2	(1-α)^-1/2
13	Power low (n =2)	C₂	(1-α)²	(1-α)^-1-1
14	Power low (n =3)	C₃	(1-α)³	0.5[(1-α)^-2-1]

ZrO₂	20wt%	40wt%	60wt%
Reduction	163.27±2.36	152.94±5.12	160.37±4.04
Oxidation	38.52±2.23	37.74±3.45	42.24±2.25

ZrO₂	20wt%	40wt%	60wt%
Reduction	163.27±2.36	152.94±5.12	160.37±4.04
Oxidation	38.52±2.23	37.74±3.45	42.24±2.25