Computer Simulation of Molten Li2CO3-K2CO3Mixtures

Kondo, Takahiro; Kawase, S.; Tamaki, Shigeru; Ebisuzaki, Toshikazu

doi:10.1143/jpsj.69.3291

Cited by 29 publications

(26 citation statements)

References 10 publications

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“…Because of the larger size of the K + ion, in K 2 CO 3 we find a cage of six oxygen atoms around the metal ion, suggesting that it occupies an octahedral site. The same coordination numbers in Li 2 CO 3 and K 2 CO 3 were also found from simulation by Koishi et al 74 .…”

Section: Structural Propertiessupporting

confidence: 84%

Molecular Dynamics Simulations of Metal/Molten Alkali Carbonate Interfaces

et al. 2017

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Interfaces between molten carbonates M 2 CO 3 (M=Li, Na and K) and planar metal walls have been investigated by molecular dynamics based on a rigid-ions force field (Janssen and Tissen, Mol. Simul. 5, 83-98, (1990)). Simulations cover the temperature range 1200 K ≤ T ≤ 1500 K at a moderate (∼ 15 kbar) overpressure to compensate for a slight overestimate of the system volume by the force field model. Most of the simulations represent neutral electrodes, but shorter computations have been carried out for systems with a low surface charge distribution on the metal side of the interface. The results provide an intriguing view of the interplay among ion packing, oscillating screening, anisotropic correlations and ion dynamics at the interface. The mass and charge density profiles display prominent peaks at contact, and tend to their constant bulk values through several oscillations, whose amplitude decays exponentially moving away from the interface.Oscillations in the charge density profile, in particular, limit the value of the interfacial dipole, and increase the capacitance of the interface. Ion-ion correlations are enhanced in proximity of the metal surface, but retain the exponentially-decaying oscillatory form of their bulk counterpart.Diffusion is slower in the molecularly thin layer of ions next to the interface than in the bulk.The analysis of interfaces is completed by the computation of structural properties of bulk phases, and by the estimate of transport coefficients such as self-diffusion, electrical conductivity, and especially thermal conductivity, which is seldom computed by simulation. All together, the results of our simulations for homogeneous and inhomogeneous molten carbonates provide crucial insight on systems and properties relevant for advanced devices such as fuel cells, that, in turn, might play a prominent role in future power generation strategies.

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Section: Structural Propertiessupporting

confidence: 84%

Molecular Dynamics Simulations of Metal/Molten Alkali Carbonate Interfaces

et al. 2017

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“…However, significantly fewer studies have been conducted on this topic in comparison to its structure at ambient pressure (Tissen and Janssen, 1990;Koura et al, 1996;Koishi et al, 2000). Molecular dynamics simulations of molten alkali carbonates reported by Tissen and Janssen (1990) suggest that the calculated coordination of K by oxygen at ambient pressure is between 5.36 and 6.5.…”

Section: Discussionmentioning

confidence: 99%

The K2CO3 fusion curve revisited: New experiments at pressures up to 12 GPa

Wang

Liu

Inoue

et al. 2016

Journal of Mineralogical and Petrological Sciences

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The melting temperatures of K 2 CO 3 were experimentally determined to be 1220 ± 20°C (4.0 ± 0.5 GPa), 1290 ± 10°C (9.0 ± 0.5 GPa), and 1313 ± 10°C (11.5 ± 0.5 GPa) in a 2000 ton split-sphere apparatus and 1195 ± 15°C (5.0 ± 0.5 GPa) in a 1000 ton uniaxial split-cylinder apparatus. The fusion curves of K 2 CO 3 were calculated up to~12.0 GPa for various K 0 ′ (pressure dependence of bulk modulus) values of the liquid, according to the thermodynamic properties for crystalline and liquid K 2 CO 3 . On the basis of these experimental results and fusion curves of K 2 CO 3 , the K 0 ′ for liquid K 2 CO 3 is constrained to be~14.4 ± 1.1 at pressures lower than 5.0 GPa in a third-order Birch-Murnaghan equation of state (EOS). However, the results at pressures above 9.0 GPa deviate from this trend, which suggests a possible phase transformation in either the crystalline or liquid phase of K 2 CO 3 between 5.0 and 9.0 GPa. Determination of liquid K 0 ′ allows the density of K 2 CO 3 liquid to be calculated to high pressure. In comparison with other common carbonates, K 2 CO 3 is shown to have the lowest melting temperature.

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“…Lithium-, potassium-, and sodiumcarbonate melts are employed as electrolytes in molten carbonate fuel cells (MCFCs), which operate at high temperatures (923 K), for the production of CO 2 -emission-free electricity. For this reason MCFCs are considered one of the most promising sources of green power production in the near future (Koishi et al 2000). In this context, it has been demonstrated that the physical properties of molten alkali carbonates employed in the MCFCs affect the cell performances and durability (Reeve and Tseung 1996 and references therein;Yoshiba et al 2004).…”

Section: Introductionmentioning

confidence: 99%

An advanced rotational rheometer system for extremely fluid liquids up to 1273 K and applications to alkali carbonate meltsk

Genova

Cimarelli

Hess

et al. 2016

American Mineralogist

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A high-temperature rheometer equipped with a graphite furnace, characterized by an air-bearingsupported synchronous motor, has been enhanced by a custom-made Pt-Au concentric cylinder assembly. With this adaptation, viscosity measurements of highly fluid melts can be achieved at high temperatures, up to 1273 K.Due to the air-bearing-supported motor, this apparatus can perform measurements of extremely low torque ranging between 0.01 μNm and 230 mNm (resolution of 0.1 nNm), extending the typical range of viscosity measurements accessible in the present configuration to 10 -3.5 -10 3.5 Pa·s and shear rates up to 10 2 of s -1 .We calibrated the system with distilled water, silicone oils, and the DGG-1 standard glass. We further present new data for the viscosity of Na 2 CO 3 , K 2 CO 3 , and Li 2 CO 3 liquids. Finally, a comparison between our results and literature data is provided, to illustrate the effect of chemical composition and oxygen fugacity on the viscosity of alkali carbonate melts, which serve as analogs for both carbonatitic melts and molten carbonates of industrial relevance.This study substantially improves the database of alkali carbonate melts and dramatically increases the accuracy with respect to previous measurement attempts. The very low viscosity range data and their temperature dependence also helps to constrain very well the activation energy of these highly fluid systems and confirms the estimate of a universal pre-exponential factor for non-Arrhenian viscosity-temperature relationships.

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Computer Simulation of Molten Li₂CO₃-K₂CO₃Mixtures

Cited by 29 publications

References 10 publications

Molecular Dynamics Simulations of Metal/Molten Alkali Carbonate Interfaces

Molecular Dynamics Simulations of Metal/Molten Alkali Carbonate Interfaces

The K<sub>2</sub>CO<sub>3</sub> fusion curve revisited: New experiments at pressures up to 12 GPa

An advanced rotational rheometer system for extremely fluid liquids up to 1273 K and applications to alkali carbonate meltsk

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