On the negative activation energy for limestone calcination at high temperatures nearby equilibrium

Valverde, José Manuel

doi:10.1016/j.ces.2015.04.027

Cited by 48 publications

(36 citation statements)

References 40 publications

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“…, since the values of θ are known. The calculated values of ∆ 1 G 0 + ∆G * for the calcination of pure CaCO 3 and limestone were of −22.6 and −20 kJ/mol, respectively, which are close to those reported by Valverde for natural limestone calcination near to thermodynamic equilibrium. Based on the foregoing, it follows that the two‐step reaction mechanism considered by Valverde et al is correct; therefore, Eq.…”

Section: Analysis and Resultssupporting

confidence: 86%

“…must be modified by a factor

\frac{1}{1 + λ P_{normalC O_{2}}}

, where λ is an empirical temperature‐dependent parameter. Recently, Valverde et al carried out several detailed studies on the limestone calcination near to equilibrium by considering a two‐step reaction mechanism. In the first step, chemical decomposition of CaCO 3 into a metastable CaO* and CO 2 takes place.…”

Section: Analysis and Resultsmentioning

confidence: 99%

“…Then, in the second step, metastable CaO* is transformed into stable CaO while the CO 2 is desorbed. From the above reaction mechanism, the following expression was derived

italicf ((), {italicP}_{C {normalO}_{2}}) = ((), \frac{{italicP}_{normaleq} - {italicP}_{C {normalO}_{2}}}{P_{eq}}) \times ((), 1 - italicθ)

where θ is the fraction of filled sites with adsorbed CO 2 , which is approximately given by

italicθ \approx 1 - \frac{1}{1 + exp ((), - \frac{∆_{1} G^{0} + ∆ G^{*}}{R_{g} italicT}) ((), \frac{P_{normalC O_{2}}}{P_{eq}})}

where ∆ 1 G 0 is the standard free energy change of decomposition and ∆G * is the free Gibbs energy of formation of CaO* from stable CaO. Under experimental conditions far from thermodynamic equilibrium

true(\frac{P_{C {normalO}_{2}}}{P_{eq}} ≪ 1 true)

, the aforementioned second reaction step (transformation of metastable CaO* into stable CaO and desorption of CO 2 ) occurs so quickly that calcination is only controlled by the chemical decomposition .…”

Section: Analysis and Resultsmentioning

confidence: 99%

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Effect of the CaO sintering on the calcination rate of CaCO₃ under atmospheres containing CO₂

et al. 2018

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For the calcination of CaCO3 under CO2‐containing atmospheres, a mathematical model taking into account the CO2‐catalyzed sintering of the CaO product layer is developed. In this model, a modified shrinking core model is coupled with a population balance‐based sintering model. By comparing model predictions with experimental data, it is found that CO2 strongly affects the overall calcination rate both at high temperature and CO2 partial pressure, since under these conditions CaO densification considerably reduces the effective diffusivity of CO2 within product layer. It is observed that for large particles, the CO2‐catalyzed sintering of CaO can produce the “die off” phenomenon, which takes place when the reaction stops due to the blockage of pores within product layer. Finally, it was determined that limestone impurities do not significantly affect the calcination reaction under atmospheres containing CO2, because CO2 causes a much greater increase of the CaO sintering rate than limestone impurities do. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3638–3648, 2018

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Section: Analysis and Resultssupporting

confidence: 86%

“…must be modified by a factor

\frac{1}{1 + λ P_{normalC O_{2}}}

Section: Analysis and Resultsmentioning

confidence: 99%

“…Then, in the second step, metastable CaO* is transformed into stable CaO while the CO 2 is desorbed. From the above reaction mechanism, the following expression was derived

italicf ((), {italicP}_{C {normalO}_{2}}) = ((), \frac{{italicP}_{normaleq} - {italicP}_{C {normalO}_{2}}}{P_{eq}}) \times ((), 1 - italicθ)

where θ is the fraction of filled sites with adsorbed CO 2 , which is approximately given by

italicθ \approx 1 - \frac{1}{1 + exp ((), - \frac{∆_{1} G^{0} + ∆ G^{*}}{R_{g} italicT}) ((), \frac{P_{normalC O_{2}}}{P_{eq}})}

true(\frac{P_{C {normalO}_{2}}}{P_{eq}} ≪ 1 true)

Section: Analysis and Resultsmentioning

confidence: 99%

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Effect of the CaO sintering on the calcination rate of CaCO₃ under atmospheres containing CO₂

et al. 2018

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“…This choice follows the Debye relaxation, i.e., χ ∼ 1/ 1 + ω 2 τ 2 46 , where ω is a constant (the probing frequency), and τ is temperature-dependent relaxation time. For a thermally activated process, the relation between τ and T is often specified by the Arrhenius law, i.e., 1/τ = A exp (−E a /T ), where E a > 0 is the activation energy 36,54,55 . In this case, the susceptibility will be χ ∼ 1/ 1 + A 2 ω 2 exp 2E a T , which is discussed by Jonscher 56 .…”

Section: B Rationale For Eq (9)mentioning

confidence: 99%

Insights into the dielectric response of ferroelectric relaxors from statistical modeling

Liu

Zeng

et al. 2017

Phys. Rev. B

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Ferroelectric relaxors are complex materials with distinct properties. The understanding of their dielectric susceptibility, which strongly depends on both temperature and probing frequency, has been a challenge to researchers for many years. Here we report a macroscopic and phenomenological approach based on statistical modeling to investigate how the dielectric response of a relaxor depends on temperature. Employing the MaxwellBoltzmann distribution and considering temperature dependent dipolar orientational polarizability, we propose a minimum statistical model and specific equations to understand and fit numerical and experimental dielectric responses versus temperature. We show that the proposed formula can successfully fit the dielectric response of typical relaxors, including Ba(Zr,Ti)O 3 , 0.87Pb(Zn 1/3 Nb 2/3 ) 0.87 O 3 -0.13PbTiO 3 , 0.95Pb(Mg 1/3 Nb 2/3 )O 3 -0.05Pb(Zr 0.53 Ti 0.47 )O 3 , and Bi-based compounds, which demonstrate the general applicability of this approach.

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“…This is absolutely required for the mass transfer that is fluid and particle displacements. CO 2 flow in porous media generates a high degree of supercritical heat transfer (Zhalan et al 2014), but extreme temperatures in limestone rock leads to calcination and thermal decomposition (Valverde 2015). The condition for maximum heat transfer rate in porous media due to carbon dioxide gas flow can be written as follows:…”

Section: Resultsmentioning

confidence: 99%

Subcritical CO2 effects on kaolinite fines transport in porous limestone media

Mahalingam¹,

Pranesh²,

Kanimozhi

et al. 2019

J Petrol Explor Prod Technol

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Carbonate reservoirs account for 60% share in global oil reserves, and CO 2-EOR process is employed in these carbonate fields for effective oil recovery and retention as well. Recent research reports that fines migration may lead to reservoir formation damage in oil bearing limestone and dolomite rocks. Although carbonate reservoirs are poor in clay minerals, some mass of clay fines existence in certain carbonate formations will cause severe damage to permeability and well productivity. This paper reports the single-phase flow of subcritical CO 2 in porous limestone rock core containing kaolinite clay fines. Fines are natural reservoir minerals (example, quartz) and clay particles such as kaolinite, illite, feldspar, smectite, and montmorillonite. But, this paper explores this CO 2-clay fines behavior in limestone rock as a function of kaolinite. So, two sets of core flood experiments were performed in the rock temperatures 120 °C and 160 °C. Initially, kaolinite clay has been injected into the limestone core in the form of suspension and then dried for hours in order to retain the solid fines in the internal pore chambers of the core. After that, the CO 2 under subcritical condition has been injected into the porous limestone core for fines mobilization and injected gas recovery. The major observations that are reported from the experimental tests are there is an increase in gas saturation for increasing injection time. Steady rise of heat transfer coefficient and enthalpy was noted for increasing gas saturation and time. Concentration of fines linearly soars with respect to elevating PVI and permeability declines for rising time. Pressure in the limestone core shows abnormal and nonlinear variation. Finally, gas discharge rate declines for increasing injection time. Experimental data are tested against the statistical model (regression), and the outcome indicated good agreement. Overall, this paper has successfully established the CO 2 effects on kaolinite clay fines behavior and its impact on oil recovery in carbonate fields.

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On the negative activation energy for limestone calcination at high temperatures nearby equilibrium

Cited by 48 publications

References 40 publications

Effect of the CaO sintering on the calcination rate of CaCO₃ under atmospheres containing CO₂

Effect of the CaO sintering on the calcination rate of CaCO₃ under atmospheres containing CO₂

Insights into the dielectric response of ferroelectric relaxors from statistical modeling

Subcritical CO2 effects on kaolinite fines transport in porous limestone media

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On the negative activation energy for limestone calcination at high temperatures nearby equilibrium

Cited by 48 publications

References 40 publications

Effect of the CaO sintering on the calcination rate of CaCO3 under atmospheres containing CO2

Effect of the CaO sintering on the calcination rate of CaCO3 under atmospheres containing CO2

Insights into the dielectric response of ferroelectric relaxors from statistical modeling

Subcritical CO2 effects on kaolinite fines transport in porous limestone media

Contact Info

Product

Resources

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Effect of the CaO sintering on the calcination rate of CaCO₃ under atmospheres containing CO₂

Effect of the CaO sintering on the calcination rate of CaCO₃ under atmospheres containing CO₂