NaCl KCl Research Articles

Study on the corrosion behavior of 316H stainless steel in molten NaCl–KCl–MgCl2 salts with and without purification

Study on the corrosion behavior of 316H stainless steel in molten NaCl–KCl–MgCl2 salts with and without purification

How cell design affects the performance of sodium-antimony-bismuth liquid metal batteries

Low-cost sodium-based liquid metal batteries are attractive candidates for grid-scale stationary energy storage. In this study, the performance of Na//SbBi9 test cells with molten salt electrolyte LiCl–NaCl–KCl (61-3-36 mol%) is evaluated for different cell designs. Cells with a metal foam hosting the negative electrode (5–6 Ah nominal capacity) and cells without foam are investigated. Additionally, the amount of electrolyte and the material used as positive current collector (PCC) are varied. The self-discharge current is only ∼0.35 mA/cm2 and depends reasonably on electrode distance and operating temperature. Contact resistances are 10 mΩ in total and thus smaller than the ohmic resistance of the electrolyte. The cell voltage is not affected by cell design, operating temperature, or cell age. Long-term cycling tests show a capacity decrease, which can be attributed to evaporation of Na. An additional capacity loss observed in cells with stainless steel PCC can be avoided by using Mo as PCC.

Core design study of the Wielenga Innovation Static Salt Reactor (WISSR)

This paper presents the design features and preliminary design analysis results of the Wielenga Innovation Static Salt Reactor (WISSR). The WISSR incorporates features that make it both flexible and inherently safe. It is based on innovative technology that controls a nuclear reactor by moving molten salt fuel into or out of the core. The reactor is a low-pressure, fast spectrum transuranic (TRU) burner reactor. Inherent shutdown is achieved by a large negative reactivity feedback of the liquid fuel and by the expansion of fuel out of the core. The core is made of concentric, thin annular fuel chambers containing molten fuel salt. A molten salt coolant passes between the concentric fuel chambers to cool the core. The core has both fixed and variable volume fuel chambers. Pressure, applied by helium gas to fuel reservoirs below the core, pushes fuel out of a reservoir and up into a set of variable volume chambers. A control system monitors the density and temperature of the fuel throughout the core. Using NaCl-(TRU,U)Cl3 fuel and NaCl–KCl–MgCl2 coolant, a road-transportable compact WISSR core design was developed at a power level of 1250 MWt. Preliminary neutronics and thermal-hydraulics analyses demonstrate the technical feasibility of WISSR.

INVESTIGATION OF THE MECHANISM OF LANTHANUM IONS ELECTROREDUCTION ON NICKEL ELECTRODE IN CHLORIDE MELT

The electrochemical behavior of lanthanum ions on a nickel electrode has been studied using various electrochemical methods such as cyclic voltammetry, chronopotentiometry, open circuit chronopotentiometry (on-off curves), and square wave voltammetry in an equimolar melt of potassium and sodium chlorides at 973 K. The cyclic voltammetry curves has several reduction waves on the cathodic branch and corresponding oxidation waves on the anodic branch. The first wave A is located in the potential region –(0.0–0.1) V, where the reduction of Ni2+ ions takes place. The second wave B is in the region of potentials –(1.72–1.77) V, on it occurs electroreduction of ions \({\text{LaCl}}_{6}^{{3 - }}\) on nickel electrode with certain depolarization with formation of intermetallide of lanthanum with nickel LaxNiy. The appearance of the third wave C in the potential region –(2.09–2.13) V, we associate with the electroreduction of chloride complexes \({\text{LaCl}}_{6}^{{3 - }}\) on intermetallide LaxNiy with the formation of metallic lanthanum. On the basis of the obtained data it is shown that during the electroreduction of lanthanum chloride complexes in KCl–NaCl melt at T = 973K the nickel electrode interacts with the released lanthanum, causing a significant depolarization of the process of electroreduction of the chloride complex, also formation of intermetallide with Ni electrode occurs.

Molecular dynamics simulation on thermophysical properties and local structure of ternary chloride salt for thermal energy storage and transfer system

Ternary chloride salt (NaCl–KCl–MgCl2) is considered as a potential high temperature thermal storage material owing to its low melting point, excellent thermal properties and low cost. However, the thermophysical properties of ternary chloride salts are difficult to measure under high-temperature conditions. In this study, the microscopic model of ternary chloride salt is constructed by Materials Studio software. The ratio of Na ions, K ions, Mg ions and Cl ions in the simulation system is determined according to the molar ratio of NaCl–KCl–MgCl2 eutectic ternary chloride salt. The total number of ions is identified based on computational resources and the accuracy of simulation results, and the number of the four ions in the system is finally determined. LAMMPS software is used to simulate the microstructure and calculate the thermal properties. Simulation results indicate that as the temperature increases, the distance between cluster ions increases, while the coordination number decreases, resulting in the ion association weakens. Simulation results of thermophysical properties are in good agreement with the experimental measurements. The decrease in density and viscosity is attributed to the weakening of ion association with increasing temperature. All the results are expected to provide reliable guidance for the design and preparation of next-generation concentrating solar thermal energy storage materials.

Thermodynamic calculations and experimental studies of ternary molten salts for high-temperature thermal energy storage

Chloride, fluoride, and carbonate salts act as potentially promising thermal storage media for high-temperature thermal energy storage (TES) systems. In this study, the eutectic components of three ternary molten salts; i.e., NaCl–KCl–LiCl, NaCl–KCl–NaF, and NaCl–KCl–Na2CO3 were first predicted by using thermodynamic calculations and the accuracy was further verified by differential scanning calorimetry. Next, the melting point, thermal conductivity, latent heat, specific heat, and TES density of the three eutectic salts were determined and calculated by thermal analysis methods and compared with those of Solar and Hetic salts. The results show that the eutectic salt NaCl–KCl–Na2CO3 exhibits the highest TES density, which is 1.87 and 1.31 times higher than that of the Solar salt and Hetic salt, respectively. Moreover, the costs of the three eutectic salts were calculated and analyzed herein, and the cost per unit TES density of the eutectic salt NaCl–KCl–Na2CO3 accounted for only 17.01 % and 29.75 % of the cost of the Solar salt and Hetic salt, respectively. The three eutectic salts exhibit good thermal stability even at a high temperature of 700 °C, and thus act as potential candidates for thermal storage materials for the next-generation concentrating solar power plants.

Corrosion Behaviour of Fe-Based and Ni-Based Alloys in Wet CO2 Gas with and without Chloride Deposits at 750 °C

Corrosion behaviours of Fe–25Cr, Fe–25Cr–2Mn–1Si, Fe–25Cr–20Ni, 310SS, Ni–25Cr, and Ni–25Cr–2Mn–1Si (all in wt%) with and without NaCl–KCl deposits in Ar–60%CO2–20%H2O gas at 750 °C were studied. Without salt deposits, Fe–25Cr performed protectively, while Fe–25Cr–20Ni and Ni–25Cr underwent breakaway oxidation with multilayered scales formed. Adding alloy elements Si + Mn increased the corrosion resistance of all alloys by forming additional Mn-rich oxides and silica. Surface deposits of NaCl–KCl accelerated corrosion, forming porous Fe-rich oxide nodules for Fe–25Cr and thick, porous scales and internal oxidation zones for all other alloys. The protective effect of Si + Mn alloying disappeared in the presence of chlorides. Limited intergranular carbides were observed for all alloys in the gas-only condition. The extent of carburisation increased with the presence of chloride deposits for all Fe-based alloys, but remained unchanged for Ni-based alloys. Corrosion of these alloys at 750 °C is compared with that at 650 °C. The effect of chlorides in volatilising metals at 750 °C is discussed.

LUMINESCENT DETERMINATION OF EUROPIUM AND CERIUM IN THE JOINT PRESENCE IN SOLUTIONS – MELTS OF EQUIMOLAR MIXTURES NaCl–KCl

Europium and Cerium belong to lanthanides of variable valency and have similar chemical properties. Luminescent method was proposed for the analytical determination of Eu(III) and Ce(III) with the simultaneous presence in the sample of [EuF3–CeF3 (1:1)]–[NaCl–KCl] (2:8), which is a promising material for detecting UV-solar radiation. Determination of Eu(III) was carried out by the method of sensitized 4f-4f luminescence in a complex with nalidixic acid at an emission wavelength of 613 nm, λex =351 nm. During complexation, a standard ratio of Stark components to Europium is observed in the luminescence spectra, in contrast to the spectrum of the sample solution without the reagent. This fact indicates that the formation of complexes not only increases the intensity of Eu(III) luminescence, but also reduces the effect of Cerium present in the solution. To determine Ce(III), its own luminescence caused by 5d-4f electronic transitions was used at an emission wavelength of 351 nm, λex =263 nm. The presence of Europium ions in the solution does not affect the nature of the luminescence excitation spectra and Ce(III) luminescence spectra. For the quantitative determination of these lanthanides, the additive method was used, which allows to level the mutual influence of ions, as well as the influence of Ce(IV) on the determination of Ce(III). It was found that the content of Eu(III) in the melt is 2.44–2.53% weight, which is in good agreement with the data obtained earlier when studying the EuF3 – [NaCl–KCl](1:9) system. Compared to EuF3, the solubility of CeF3 ((0.028–0.032)% weight) is significantly lower than that predicted by previous thermodynamic calculations. The obtained data allow us to conclude that the solubility of fluoride systems containing Eu in the NaCl–KCl melt is almost the same, and the presence of Ce(III) does not significantly affect the EuF3 dissolution process, and therefore does not affect the properties of the systems [EuF3 – CeF3] – [NaCl–KCl] as detectors of ultraviolet solar radiation.

Strategies to Stabilize Dalbavancin in Aqueous Solutions; Section-1: the Effects of Metal Ions and Buffers.

The effect of monovalent (Na+ and K+) and divalent (Ca2+, Mg2+, and Zn2+) metal ions combined with citrate or acetate buffers (pH 4.5) on the stability of dalbavancin in aqueous solutions was investigated. RP-HPLC and HP-SEC were used to evaluate the stability of aqueous solutions of dalbavancin in different combinations of buffers and metal ions after four weeks of storage at 5°C and 55°C. A long-term study of formulations with divalent metal ions was conducted over six months at 5°C., 25°C and 40°C using RP-HPLC. All formulations in citrate buffered solutions precipitated. Dalbavancin solutions in 10mM acetate buffer at 55°C were more stable in 10mM CaCl2, 5mM ZnCl2 and 10mM MgCl2 than those containing 2mM NaCl or 5mM KCl, although the MgCl2 formulations precipitated slightly. No significant effect was observed for any of the divalent metal ions at 40°C for six months. Dalbavancin's stability in solution was improved by a combination of acetate and divalent metal ions at 55°C for four weeks. No effect was observed with acetate or metal ions alone, and no effect was observed after six months at 40°C suggesting that acetate and divalent metal ions together interact with dalbavancin via a thermally activated step to inhibit hydrolysis of the drug.

Thermal conductivity measurement using modulated photothermal radiometry for nitrate and chloride molten salts

Molten salts are being used or explored for thermal energy storage and conversion systems in concentrating solar power and nuclear power plants. Thermal conductivity of molten salts is an important thermophysical property dictating the performance and cost of these systems, but its accurate measurement has been challenging, as evidenced by wide scattering of existing data in literature. The corrosive and conducting nature of these fluids also leads to time consuming sample preparation processes of many contact-based measurements. Here, we report the measurement of thermal conductivity of molten salts using a modulated photothermal radiometry (MPR) technique, which is a laser-based, non-contact, frequency-domain method adopted for molten salts for the first time. By unitizing the advantages of front side sensing of frequency-domain measurements and the vertical holder orientation, the technique can minimize the natural convection and salt creeping effects, thus yielding accurate molten salt thermal conductivity . The MPR technique is first calibrated using standard molten materials including paraffin wax and sulfur. It is then applied on measuring pure nitrate salts (NaNO3 and KNO3), solar salt (NaNO3–KNO3 mixture), and chloride salt (NaCl–KCl–MgCl2). The measurement results are compared with data from literature, especially those obtained from laser flash analysis (LFA). Our results demonstrate that the MPR is a convenient and reliable technique of measuring thermal conductivity of molten salts. Accurate thermal conductivity data of molten salts will be valuable in developing the next-generation high-temperature thermal energy storage and conversion systems.

Development and demonstration of a rolling ball viscometer for molten salts with near-minimum liquidus NaCl–KCl

Development and demonstration of a rolling ball viscometer for molten salts with near-minimum liquidus NaCl–KCl

Comprehensive thermal properties of ternary eutectic molten salt/nanoparticles composite phase change materials for high–temperature thermal energy storage

Chlorine and fluorine salts are very promising thermal storage media for high–temperature thermal energy storage (TES) systems. In this study, NaCl–KCl–NaF/nanoparticles composite phase change materials (CPCMs) were employed by an advanced high–temperature and high–pressure reactor. NaCl–KCl–NaF was adopted as the BS, while CuO and Al2O3 nanoparticles have been uniformly dispersed in different ratios to generate CPCMs from the base salt (BS). Microscopic characterization, thermal properties characterization, and economic analysis of CPCMs and the BS were performed. The findings revealed that the best results were obtained when the BS was added with 0.5 wt percent Al2O3 and 0.5 wt percent CuO nanoparticles, CPCMs have improved solid/liquid thermal conductivity by a factor of 3.70 and 1.84, and TES density by a factor of 1.13, while reducing the cost per unit of TES density by approximately 26.8%. In addition, the CPCMs and BS possess excellent operating temperature range and thermal stability, whereby they are applicable in high–temperature TES systems.

Corrosion behavior and mechanism of 316 stainless steel in NaCl–KCl–FeCl3 molten salt and vapor at 300°C

AbstractThe corrosion behavior of 316 stainless steel (316 SS) in NaCl–KCl–FeCl3 molten salt and vapor was studied at 300°C for 150, 300, and 500 h in Ar. The weight change, the micromorphology, element distribution, and crystal structure of the 316 SS alloy were analyzed by scanning electron microscopy, energy‐dispersive spectroscopy, and X‐ray diffraction. 316 SS alloys suffered from weight loss, significant visible corrosion shedding, and corrosion holes. The corrosion holes and corrosion shedding block of the 316 SS alloys become more and more serious with the increase in corrosion time. The corrosion depth of the corroded 316 SS alloys in NaCl–KCl–FeCl3 molten salt and vapor for 500 h can even reach up to 20.0 and 14.0 μm, respectively. 316 SS alloys in NaCl–KCl–FeCl3 molten salts underwent a more serious corrosion attack than that in the NaCl–KCl–FeCl3 vapor at 300°C due to the strong oxidizing compound FeCl3 in the molten salt. It not only offers a new insight into the corrosion behavior of 316 SS alloys in the chloride salts and corresponding vapor but also enriches the corrosion databases of the chloride salts.

Electrochemical Behavior of Neodymium Ions and Their Combined Electroreduction with Nickel Ions in the KCl–NaCl–CsCl Eutectic Melt

Electrochemical Behavior of Neodymium Ions and Their Combined Electroreduction with Nickel Ions in the KCl–NaCl–CsCl Eutectic Melt

Experimental Investigation into Interaction between Amphibole and Highly Saline H2O–NaCl–KCl Fluid at 750°C, 700 MPa: Implications to Alkaline Metasomatism of Amphibole Rocks

Experimental Investigation into Interaction between Amphibole and Highly Saline H2O–NaCl–KCl Fluid at 750°C, 700 MPa: Implications to Alkaline Metasomatism of Amphibole Rocks

Production of Al–Mn/WC Composite Coatings with Electrodeposition in AlCl3–NaCl–KCl–MnCl2 Molten Salts

The hardness and wear resistance of amorphous Al–Mn alloy coatings can be improved by incorporating ceramic particles into them to extend their application. In this paper, Al–Mn/WC composite coatings have been prepared with electrodeposition in stirred AlCl3–NaCl–KCl–MnCl2 molten salts at 180 °C with the addition of WC particles. The effects of stirring speed (400–700 rpm) and cathode current density (15–75 mA/cm2) on the produced Al–Mn/WC composite coatings have been studied. At 600 rpm and 700 rpm, the Al–Mn/WC composite coatings exhibited the best uniform distribution of the embedded WC particles, with the tested microhardness value up to 650 HV0.1, compared with 530 HV0.1 of the Al–Mn alloy. Moreover, under various cathode current densities, the best quality of the Al–Mn/WC composite coating was obtained at 55 mA/cm2, with a homogeneous distribution of WC particles and the highest microhardness value (670 HV0.1). It is expected that this method could be extended to be applied for the preparation of aluminum-based and magnesium-based ceramic composite coatings.

Phase Assemblage of the Li+,Na+,K+||F–,Cl–,Br– Five-Component Reciprocal System and Its LiF–KCl–KBr–NaBr–NaCl Stable Pentatope

The phase assemblage of the Li+,Na+,K+||F–,Cl–,Br– five-component reciprocal system was studied for the first time. The phase tree obtained by partition of the phase assemblage into stable elements is linear. It consists of the following stable elements: the LiF–NaF–KF–KBr–KCl pentatope, LiF–NaBr–NaCl–KCl–KBr–NaF hexatope, and NaCl–KCl–KBr–LiBr–LiCl–LiF–NaBr heptatope, linked by the LiF–NaF–KCl–KBr stable tetrahedron and the LiF–KBr–NaBr–NaCl–KCl square pyramid (pentatope). Phase equilibria in the LiF–KCl–KBr–NaBr–NaCl stable pentatope were studied by differential thermal analysis (DTA). Monovariant phase equilibrium L ⇄ LiF + NaClxBr1 – x + KClyBr1 – y occurs in the pentatope, where NaClxBr1 – x and KClyBr1 – y are continuous solid solutions (css) between NaCl and NaBr, KCl and KBr salt pairs, respectively. The composition of the mixture at point Min◻ 591 and the lowest monovariant equilibrium temperature were determined. A 3D computer model was designed as a projection of the phase assemblage on the LiF–KCl–KBr–NaBr–NaCl pentatope in KOMPAS-3D software. The volumes of crystallizing equilibrium phases were outlined.

Reaction of Oxygen with Uranium (IV) Chloride in Fused Alkali Chlorides

Reaction of oxygen with solutions of uranium(IV) chloride in fused LiCl and three alkali chloride eutectic mixtures (LiCl–KCl, NaCl–KCl–CsCl, NaCl–CsCl) was investigated at 550–750 °C. Bubbling oxygen or oxygen-containing gas mixtures (O2–H2O, O2–Ar, O2–H2O–Ar) through LiCl–UCl4 melts resulted in significant precipitation of uranium (up to 87%) in the form of oxides and alkali uranates. Increasing mean radius of the solvent melt cations decreased the degree of uranium precipitation and uranyl chloride (soluble in the melt) became the main product of the reaction. High temperature spectroscopy measurements were employed to determine the kinetic parameters of the reaction in LiCl–KCl, NaCl–KCl–CsCl and NaCl–CsCl melts. Reaction rates, order, rate constants and activation energy values were estimated. Increasing temperature led to increased reaction rates but the effect of uranium chloride concentration depended on the cationic melt composition. Oxygen reacts with uranium(IV) containing melts much faster than with the melts containing rare earth chlorides and oxygen sparging can be implemented for separating uranium and rare earth fission products in pyrochemical reprocessing of spent nuclear fuels.

Optimization of Dimensions of Smooth and Twisted-Tape-Inserted Tubes for Heat Transfer with NaCl/KCl/MgCl2 Molten Salts by Principle of Entropy Generation Minimization

Abstract The entropy generation minimization principle is used as the criterion to optimize the flow and heat transfer of solar collectors and heat exchangers that use molten salts NaCl–KCl–MgCl2 and KCl–MgCl2. The Gnielinski correlation for the Nusselt number versus Reynolds number, as well as the Moody friction factor given by Petukhov, was used for the calculation of the convective heat transfer coefficient and pressure loss due to friction in smooth tubes. For twisted-tap-inserted tube, equations of Nu and friction factor provided by Manglik and Bergles were used. The objective function, the entropy generation rate of the heat transfer system, was expressed as the function of Reynolds number, Prandtl number, heating flux, tube diameter, etc. As a result of the analysis, the optimum Reynolds number was determined and thereby to determine the optimum Nusselt number, convective heat transfer coefficient, friction factor, and tube diameter, which also allows the calculation of optimum flow velocity. The analysis was conducted in the fluid temperature range of 500–700 °C, which covers the operation temperature for supercritical CO2 power cycles in concentrated solar power (CSP) system. Optimized results from the smooth tube and twisted-tap-inserted tube are compared, which is important to the design of solar receivers for CSP systems.

Thermal energy storage biogel with good biodegradability for solar energy powered heavy oil recovery

For cleaner production of heavy oil with lower fossil fuel consumptions, solar thermal enhanced oil recovery (Solar TEOR) technologies are increasingly researched nowadays. However, the intermittency of solar radiation and inferior energy efficiency of steam flooding restricted industrial applications of Solar TEOR methods in oilfield. In this work, the eutectic NaCl–KCl and graphite were loaded into the biomass gelling matrix (crosslinked methylcellulose network) through supramolecular interactions. Then, a thermal energy storage biogel (NaCl–KCl)@G/MC with high thermal conductivity (2.06 W m−1·K−1), latent heat storage capacity (melting enthalpy: 112.4 J g−1 at 352.4 °C) and thermal reliability (melting enthalpy retention up to 94.4% after 30 cycles), was synthesized for improving the continuousness of solar thermal supply and energy efficiency of steam flooding. From the experimental results, the proposed oil recovery method — solar powered steam flooding in daytime + the thermal-storage biogel heated N2 flooding in nighttime — can meet the all-weather 24/7 production of heavy oil and improve energy efficiency (oil-steam ratio and thermal efficiency up to 0.56 and 62.1%). With (NaCl–KCl)@G/MC biogel assistance, energy consumption of oil production was decreased from 153.1 J·(mL oil)−1 to 9.9 J·(mL oil)−1 as the cost reduction of 19.8% in comparison with intermittent solar steaming. This study offers a candidate design to achieve a continuous thermal recovery of heavy oil entirely powered by solar energy, promoting the solar thermal technologies in oil industry operations.