Molten salts viscosity

Janz GJ, Yamamura T, Hansen MD (1989) Corresponding- states data cmrelations and molten salts viscosities. Inti J Thermophys 10 159-171... 

As in die case of die diffusion properties, die viscous properties of die molten salts and slags, which play an important role in die movement of bulk phases, are also very stiiicture-seiisitive, and will be refeiTed to in specific examples. For example, die viscosity of liquid silicates are in die range 1-100 poise. The viscosities of molten metals are very similar from one metal to anodier, but die numerical value is usually in die range 1-10 centipoise. This range should be compared widi die familiar case of water at room temperature, which has a viscosity of one centipoise. An empirical relationship which has been proposed for die temperature dependence of die viscosity of liquids as an AiTlienius expression is... 

Molten salt investigation methods can be divided into two classes thermodynamic and kinetic. In some cases, the analysis of melting diagrams and isotherms of physical-chemical properties such as density, surface tension, viscosity and electroconductivity enables the determination of the ionic composition of the melt. Direct investigation of the complex structure is performed using spectral methods [294]. 

The National Institute of Standards and Technology (NIST) molten salts database has been designed to provide engineers and scientists with rapid access to critically evaluated data for inorganic salts in the molten state. Properties include density, viscosity, electrical conductance, and surface tension. Properties for approximately 320 single salts and 4000 multicomponent systems are included, the latter being primarily binary. Data have been abstracted from the literature over the period 1890-1990. The primary data sources are the National Bureau of Standards-National... 

The molten salt standard program was initiated at Rensselaer Polytechnic Institute (RPI) in 1973 because of difficulties being encountered with accuracy estimates in the NBS-NSRDS molten salt series. The density, surface tension, electrical conductivity, and viscosity of KNO3 and NaCl were measured by seven laboratories over the world using samples distributed by RPI. The data from these round-robin measurements of raw properties were submitted to RPI for evaluation. Their recommendations are summarized in Table 2. 

Some 30 years ago, transport properties of molten salts were reviewed by Janz and Reeves, who described classical experimental techniques for measuring density, electrical conductance, viscosity, transport number, and self-diffusion coefficient. 

G. J. Janz, J. Phys. Chem. Ref Data 9 (1980) 791 Molten Salts Data as Reference Standards for Density, Surface Tension, viscosity and Electrical Conductance KN03 and NaCl, American Chemical Society-American Institute of Physics-National Bureau of Standards, Washington, DC, 1980. 

Janz, G. J., Thermodynamic and Transport Properties for Molten Salts Correlation Equations for Critically Evaluated Density, Surface Tension, Electrical Conductance, and Viscosity Data. 1988, New York American Institute of Physics. 

MSO is unsuited for treating materials with high inert content, such as asbestos, concrete, soils, and rubble. There is concern over emissions from MSO relating to particulate mercury content and radioactivity. MSO is inappropriate for wastes with high tritium levels. MSO pilot programs have encountered problems with carbon monoxide (CO) emissions. The corrosion of reactor materials by molten salt has remained a concern for the long-term operability of the system. The viscosity and volatility of the melt have to be controlled. There have been problems with material from the melt plugging air exhaust and feeder systems. 

Ionic liquids are a class of solvents and they are the subject of keen research interest in chemistry (Freemantle, 1998). Hydrophobic ionic liquids with low melting points (from -30°C to ambient temperature) have been synthesized and investigated, based on 1,3-dialkyl imidazolium cations and hydrophobic anions. Other imidazolium molten salts with hydrophilic anions and thus water-soluble are also of interest. NMR and elemental analysis have characterized the molten salts. Their density, melting point, viscosity, conductivity, refractive index, electrochemical window, thermal stability, and miscibility with water and organic solvents were determined. The influence of the alkyl substituents in 1,2, 3, and 4(5)-positions on the imidazolium cation on these properties has been scrutinized. Viscosities as low as 35 cP (for l-ethyl-3-methylimi-dazolium bis((trifluoromethyl)sulfonyl)amide (bis(triflyl)amide) and trifluoroacetate) and conductivities as high as 9.6 mS/cm were obtained. Photophysical probe studies were carried out to establish more precisely the solvent properties of l-ethyl-3-methyl-imidazolium bis((trifluoromethyl)sulfonyl)amide. The hydrophobic molten salts are promising solvents for electrochemical, photovoltaic, and synthetic applications (Bon-hote et al., 1996). 

Molten salts are ionic liquids and as such can be utilized in a wide range of electrochemical applications where high conductivity and ionic mobility are required (Papa-georgiou et al., 1996). Their ionic nature renders them negligibly volatile in the liquid state. These properties as well as relatively low viscosity, the large electrochemical window, thermal stability, miscibility with solvents or other salts and hydrophobicity are a few of the desirable qualities found in certain molten salts. 

Cross-flow filters behave in a way similar to that normally observed in crossflow filtration under ambient conditions increased shear-rates and reduced fluid-viscosity result in an increased filtrate number. Cross-microfiltration has been applied to the separation of precipitated salts as solids, giving particle-separation efficiencies typically exceeding 99.9%. Goemans et al. [30] studied sodium nitrate separation from supercritical water. Under the conditions of the study, sodium nitrate was present as the molten salt and was capable of crossing the filter. Separation efficiencies were obtained that varied with temperature, since the solubility decreases as the temperature increases, ranging between 40% and 85%, for 400 °C and 470°C, respectively. These workers explained the separation mechanism as a consequence of a distinct permeability of the filtering medium towards the supercritical solution, as opposed to the molten salt, based on their clearly distinct viscosities. 

There are some density data for solid salts above ambient temperature which are given in the form of thermal expansion coefficients. These have been listed when they seemed reliable. Above the melting point, density data are scarce. Most are available for alkali halides but those available for salts are taken from the critically evaluated compilation Janz, G.J., Thermodynamics and transport properties for molten salts, correlation equations for critically evaluated density, surface tension, electrical conductance, and viscosity data,./. Phys. Chem. Reference Data, 17, Suppl. 2, 1988. 

We have fitted the viscosity of ionic liquids using hole theory [123]. The theory was developed for molten salts but has been shown to be very useful for ionic liquids. It was shown that the value of En is related to the size of the ions and the size of the voids present in the liquid [103]. The viscosity of ionic liquids is... 

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