Li2CO3 Na2CO3 K2CO3 Research Articles

Enhanced thermal properties of Li2CO3–Na2CO3–K2CO3 nanofluids with nanoalumina for heat transfer in high-temperature CSP systems

Nanofluids of Li2CO3–Na2CO3–K2CO3 improved by three nano-Al2O3 samples are firstly prepared by means of two-step aqueous method to enhance thermal properties for high-temperature heat transfer, when used as heat transfer fluids and thermal energy systems for concentrating solar power systems. Specific heat of ternary carbonates containing Al2O3 of 0.2, 0.4, 0.8, 1.0, 1.4 and 2.0 mass% is measured, and nanofluids with 1.0 mass% of 20-nm Al2O3, 1.0 mass% of 50-nm Al2O3 and 0.8 mass% of 80-nm Al2O3 are selected as superior candidates. The maximum enhancement of specific heat is 18.5% in solid and 33.0% in liquid, 17.9% in solid and 22.7% in liquid, 13.2% in solid and 17.5% in liquid for nanofluids containing 20-, 50- and 80-nm Al2O3. Thermal conductivity is, respectively, improved by 23.3, 28.5 and 30.9% under the addition of Al2O3. New chemical bonds and crystals are scarcely formed in composites through FT-IR and XRD determination. SEM images certify that nano-Al2O3 are homogeneously mixed into nanofluids and this structure may be a critical incentive for enhancing thermal properties. There are no significant changes with respect to the heat flow, melting/freezing point and latent heat after the 30 circles of determination. Briefly, it can be speculated that these nanofluids will exhibit tremendous potential in the coming applications of heat transfer and thermal storage for concentrating solar power systems.

Development of bioceramic bone scaffolds by introducing triple liquid phases

Abstract

Specific features of the interaction of α- and γ-modifications of Al2O3 with carbonate and carbonate-chloride melts

Data on reactivities of α- and γ-Al2O3 finely dispersed powders in a melted carbonate eutectic (Li2CO3–Na2CO3–K2CO3)eut and carbonate-chloride mixture 0.72(Li2CO3–Na2CO3–K2CO3)eut–0.28NaCl were obtained. The methods of synchronous thermal and X-ray phase analyses and Raman spectroscopy confirmed that, in contrast to γ-Al2O3, α-Al2O3 does not chemically interact with the melted carbonate eutectic and carbonate-chloride mixture (Li2CO3–Na2CO3–K2CO3)eut–NaCl can be recommended as a thickening agent for a carbonate fuel cell.

Determination and evaluation of the thermophysical properties of an alkali carbonate eutectic molten salt.

The thermal physical properties of Li2CO3-Na2CO3-K2CO3 eutectic molten salt were comprehensively investigated. It was found that the liquid salt can remain stable up to 658 °C (the onset temperature of decomposition) by thermal analysis, and so the investigations on its thermal physical parameters were undertaken from room temperature to 658 °C. The density was determined using a self-developed device, with an uncertainty of ±0.00712 g cm(-3). A cooling curve was obtained from the instrument, giving the liquidus temperature. For the first time, we report the obtainment of the thermal diffusivity using a laser flash method based on a special crucible design and establishment of a specific sample preparation method. Furthermore, the specific heat capacity was also obtained by use of DSC, and combined with thermal diffusivity and density, was used to calculate the thermal conductivity. We additionally built a rotating viscometer with high precision in order to determine the molten salt viscosity. All of these parameters play an important part in the energy storage and transfer calculation and safety evaluation for a system.

The compressibility of CaCO3–Li2CO3–Na2CO3–K2CO3 liquids: application to natrocarbonatite and CO2-bearing nephelinite liquids from Oldoinyo Lengai

To constrain the compressibility of natrocarbonate liquids, sound-speed measurements were made on 11 liquids in the CaCO3–Li2CO3–Na2CO3–K2CO3 quaternary system from 808 to 1323 K at 1 bar with a frequency-sweep acoustic interferometer. CaCO3 concentrations range from 15 to 50 mol% in four of the experimental liquids. The sound-speed data for all liquids were converted to isothermal compressibility (β T ), which were fit to an ideal mixing model with respect to composition; the average residual is 1.2 %. Fitted values (±1σ) of the partial molar compressibility (10−2 GPa−1) at 1100 K were derived for CaCO3 (5.36 ± 0.13), Li2CO3 (8.09 ± 0.06), Na2CO3 (10.62 ± 0.07), and K2CO3 (14.09 ± 0.06); these values translate to bulk modulus values of 18.7, 12.4, 9.4, and 7.1 GPa, respectively, reflecting the relatively large compressibility of carbonate liquids. The data are additionally used to estimate the partial molar volume and compressibility of the CO2 component dissolved as carbonate in nephelinite liquids; the density of this dissolved component at 1423 K and 1 GPa ranges from 1.62, 1.71 to 1.83 g/cm3 when it is complexed with K+, Na+, and Ca2+, respectively, and is estimated to be ~2.05 and 2.14 g/cm3 when complexed with Fe2+ and Mg2+, respectively. The results from this study can be applied to natrocarbonate liquids, such as those erupted from Oldoinyo Lengai volcano in Africa, and indicate a melt density of ~2.19 g/cm3 at 1150 °C and 1 GPa, which is ~18 % less dense than the average melt density (~2.67 g/cm3) calculated for associated Mg-poor nephelinite liquids at the same conditions and volatile-free. However, the dissolution of 10.1 wt% H2O and 8.7 wt% CO2 in the average nephelinite melt (based on volatile contents reported in the literature for these magmas) reduces its density to ~2.14 g/cm3 at 1150 °C and 1 GPa, eliminating the buoyancy contrast with the natrocarbonate melt. In turn, it is highly likely that the natrocarbonatite melts contained significant amounts of dissolved H2O and, as an example, the addition of 10 wt% H2O lowers the melt density by ~14 % to ~1.88 g/cm3, and therefore re-establishes a large density contrast with the volatile-rich nephelinite melts.

Mixed metal carbonates/hydroxides for concentrating solar power analyzed with DSC and XRD

Li2CO3–Na2CO3–K2CO3 molten salt mixtures are potentially suitable for high temperature thermal energy storage in the concentrating solar power. We investigated the LiNaK carbonate salt with hydroxides of lithium (LiOH), potassium (KOH), or calcium (Ca(OH)2) by using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). From the repeated heating DSC curves, lower melting points with excellent reproducibility were found when 10wt% LiOH or KOH was added into 40wt%Li2CO3–20wt%Na2CO3–40wt%K2CO3. Based on the characterization of XRD patterns, the molten eutectic mixtures consisted of LiKCO3, LiNaCO3, and residual Li2CO3 when the ternary carbonate salt was heated at the temperature above the melting point and cooled rapidly. In the system of LiNaK carbonate salt with additives of LiOH or KOH, more LiKCO3 and LiNaCO3 with lower melting point can be formed by substitution reaction. Thus, optimal molar ratio for the mixed molten salts with low melting point could be quickly obtained by studying the composition of the resulting eutectic mixtures.

Effects of applied voltage and temperature on the electrochemical production of carbon powders from CO2 in molten salt with an inert anode

With a SnO2 inert anode, amorphous carbon powders were successfully deposited on a nickel cathode by electrochemical conversion of CO2 in Li2CO3–Na2CO3–K2CO3 eutectic melt in the temperature range of 450°C to 650°C and under the electrolysis voltages of 3.0V to 6.0V. The effects of electrolysis temperature and cell voltage on the morphology and structure of the produced carbon, and on the energy consumption of the process were systematically investigated. The morphologies and particle size of the carbon products were proven to be affected by the electrolysis cell voltage and temperature. As the electrolysis condition varied, the deposited carbon exhibited different forms, including nanoparticle, nanoflake, nanosheet and heart-shape nanostructured cage, etc. The particle sizes of the obtained carbon ranged from av. 2μm to 50nm, and smaller particles were obtained at higher cell voltage and lower electrolysis temperature. The carbon product obtained at 450°C under 5.5V exhibited the highest BET surface area of 868.3m2g−1. FTIR analysis demonstrated that oxygen-containing functional groups presented on the surface of the carbon product, which was most likely due to the active dangling bond on the carbon materials. The optimized energy consumption for producing 1 kg of carbon is as low as 35.59kWh with a current efficiency of 87.86% at 450°C under a constant cell voltage of 3.5V.

Effects of support pore structure on carbon dioxide permeation of ceramic-carbonate dual-phase membranes

Dual-phase membranes consisting of an ionic or mixed conducting ceramic phase and a molten carbonate phase are permeable only to carbon dioxide at high temperatures. This paper studies the effects of the pore structure of ceramic supports on carbon dioxide permeation properties of dual-phase membranes consisting of La0.6Sr0.4Co0.8Fe0.2O3−δ (LSCF) and eutectic Li2CO3–Na2CO3–K2CO3 carbonate phase. Porous LSCF supports with different pore structures were prepared by pressing LSCF powders followed by sintering at various temperatures. The porosity to tortuosity and solid fraction to tortuosity ratios for the porous LSCF supports were characterized by helium permeation and electrical conductivity measurements. The direct infiltration method allows complete filling of the ceramic support pores by the carbonate. CO2 permeance of the dual-phase membranes increases, and after reaching a maximum, decreases with increasing support sintering temperature or support porosity (carbonate fraction). A total conductance in terms of the effective carbonate and ionic conductivities (intrinsic conductivity modified by the carbonate or solid fraction to tortuosity ratio) is introduced and used to explain experimental results. The results show that the CO2 permeance of the dual-phase membrane is controlled not only by the intrinsic carbonate and oxygen ionic conductivities of the carbonate and ceramic phases, but also the carbonate or solid fraction to tortuosity ratio. Adjusting pore and solid microstructure of ceramic support is critical to maximize CO2 permeance of the dual-phase membranes.

Mass transfer in molten salt and suspended molten salt in bubble column

Recently, the practical uses of bubble columns and slurry bubble columns at elevated temperature have attracted much attention. However, there is less knowledge of mass transfer in high temperature slurry bubble column, even though mass transfer data is essential to design bubble column and slurry bubble column. In this study, the CO2 mass transfer in eutectic mixtures of molten carbonate in bubble column at elevated temperature was investigated. CO2 was chosen as gas species, eutectic mixtures of Li2CO3–K2CO3 (38:62mol%) binary molten carbonate and Li2CO3–Na2CO3–K2CO3 (43.5:31.5:25mol%) ternary molten carbonate were used as liquid phase. In those eutectic mixtures, CO2 solubilities were determined at the temperature from 673K to 1173K. The values of solubilities increased with increasing temperature. It was suggested that CO2 dissolved into binary and ternary molten carbonate with chemical interaction, CO2+CO32−↔C2O52−. Increasing the temperature shifted this equation to the right and then more CO2 chemically dissolved into molten carbonates as C2O52−. From the CO2 gas absorption rate in molten carbonates, CO2 liquid phase volumetric mass transfer coefficients, kLa were determined and the influence of temperature and superficial gas velocity on kLa was also investigated. The kLa decreased with increasing temperature. And the kLa increased linearly with increasing superficial gas velocity. Regardless of unusual conditions in molten salt in bubble column at high temperature, where viscosity, surface tension and gas diffusivity were relatively high, it was suggested that the superficial gas velocity was most important operation condition in common with aqueous bubble column at ambient temperature.

The Thermal Stability of Molten Lithium–Sodium–Potassium Carbonate and the Influence of Additives on the Melting Point

The thermal stability of a molten LiNaK carbonate salt, potentially suitable for thermal energy storage, was studied up to a temperature of 1000 °C. The salt investigated was the eutectic Li2CO3–Na2CO3–K2CO3 in the proportions 32.1–33.4–34.5 wt. % and the study was done by simultaneous differential scanning calorimetry (DSC)/thermogravimetric–mass spectrometric (TG–MS) analysis in gas atmospheres of argon, air, and CO2. It was found that (i) under a blanket gas atmosphere of CO2 the LiNaK carbonate salt is stable up to at least 1000 °C. (ii) In an inert atmosphere of argon, the salt evolves gaseous CO2 soon after melting and begins to decompose at between 710 °C and 715 °C with acceleration in the CO2 evolution rate from the melt. An increase in the rate of weight loss is also observed after 707 °C. (iii) Under a blanket atmosphere of air, the gaseous CO2 evolution from the salt is observed to commence at 530 °C, the onset of decomposition detected by DSC analysis at 601 °C and the rapid rate of weight loss determined by TG analysis at 673 °C. The melting point of the LiNaK carbonate studied was between 400 °C and 405 °C. Thermodynamic modeling with Multi-Phase-Equilibrium (MPE) software developed in CSIRO Process Science and Engineering indicated that additives such as NaNO3, KCl, and NaOH lower the melting point of the LiNaK carbonate eutectic, and this was experimentally verified.

New density measurements on carbonate liquids and the partial molar volume of the CaCO 3 component

Density measurements on nine liquids in the CaCO3–Li2CO3–Na2CO3–K2CO3 quaternary system were performed at 1 bar between 555 and 969 °C using the double-bob Archimedean method. Our density data on the end-member alkali carbonate liquids are in excellent agreement with the NIST standards compiled by Janz (1992). The results were fitted to a volume equation that is linear in composition and temperature; this model recovers the measured volumes within experimental error (±0.18% on average, with a maximum residual of ±0.50%). Our results indicate that the density of the CaCO3 component in natrocarbonate liquids is 2.502 (±0.014) g/cm3 at 800 °C and 1 bar, which is within the range of silicate melts; its coefficient of thermal expansion is 1.8 (±0.5)×10−4 K−1 at 800 °C. Although the volumes of carbonate liquids mix linearly with respect to carbonate components, they do not mix linearly with silicate liquids. Our data are used with those in the literature to estimate the value of % MathType!MTEF!2!1!+- % feaafeart1ev1aaatCvAUfeBSn0BKvguHDwzZbqefeKCPfgBGuLBPn % 2BKvginnfarmWu51MyVXgatuuDJXwAK1uy0HwmaeHbfv3ySLgzG0uy % 0Hgip5wzaebbnrfifHhDYfgasaacH8srps0lbbf9q8WrFfeuY-Hhbb % f9v8qqaqFr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq % -He9q8qqQ8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeWaea % aakeaadaqdaaqaaiaadAfaaaWaaSbaaSqaaiaadoeacaWGpbWaaSba % aWqaaiaaikdaaeqaaaWcbeaaaaa!3D20! $$ \overline V _{CO_2 } $$ in alkaline silicate magmas (≥20 cm3/mol at 1400 °C and 20 kbar), where CO2 is dissolved as carbonate in close association with Ca. Our volume measurements are combined with sound speed data in the literature to derive the compressibility of the end-member liquids Li2CO3, Na2CO3, and K2CO3. These results are combined with calorimetric data to calculate the fusion curves for Li2CO3, Na2CO3, and K2CO3 to 5 kbar; the calculations are in excellent agreement with experimental determinations of the respective melting reactions.

Solubility and Solvation of Carbon Dioxide in the Molten Li2CO3/Na2CO3/K2CO3 (43.5:31.5:25.0 mol-%) Eutectic Mixture at 973 K I. Experimental Part

The solubility of CO2 in the molten ternary eutectic mixture Li2CO3–Na2CO3–K2CO3 (43.5, 31.5, 25.0 mol.%) at 973 K has been determined by a titration technique. From the obtained titration curve, the solubility has been found to amount to 9.5·10−2 mol·L−1 (σ= 1.0) under a pressure of CO2 of 1 atm and the pKd value of the carbonate melt has been evaluated to 5.37 (σ5 = 0.24) if the concentrations of the solutes are expressed in mol·L−1. This pKd value is in good agreement with literature data but the solubility value reported in this work is much higher than most of those reported in the literature. A chemical dissolution of CO2 as C2O52– is proposed and the consequences of the occurrence of this species on the acidobasic properties of molten carbonates are discussed. It appears from the experimental results that the CO2/C2O52– equilibrium in the carbonate melt is a slow process.

Solubility and Solvation of Carbon Dioxide in the Molten Li2CO3/Na2CO3/K2CO3 (43.5:31.5:25.0 mol-%) Eutectic Mixture at 973 K I. Experimental Part

The solubility of CO2 in the molten ternary eutectic mixture Li2CO3–Na2CO3–K2CO3 (43.5, 31.5, 25.0 mol.%) at 973 K has been determined by a titration technique. From the obtained titration curve, the solubility has been found to amount to 9.5·10−2 mol·L−1 (σ= 1.0) under a pressure of CO2 of 1 atm and the pKd value of the carbonate melt has been evaluated to 5.37 (σ5 = 0.24) if the concentrations of the solutes are expressed in mol·L−1. This pKd value is in good agreement with literature data but the solubility value reported in this work is much higher than most of those reported in the literature. A chemical dissolution of CO2 as C2O52– is proposed and the consequences of the occurrence of this species on the acidobasic properties of molten carbonates are discussed. It appears from the experimental results that the CO2/C2O52– equilibrium in the carbonate melt is a slow process.