Thermal Conductivity Measurements of Some Synthetic Al2O3-CaO-SiO2 Slags by Means of a Front-Heating and Front-Detection Laser-Flash Method

Hasegawa, Hiroki; Hoshino, Yoichiro; Kasamoto, Takeshi; Akaida, Yuuki; Kowatari, Takaya; Shiroki, Yasuhiro; Shibata, Hiroyuki; Ohta, Hiromichi; Waseda, Yoshio

doi:10.1007/s11663-012-9702-y

Cited by 29 publications

(18 citation statements)

References 31 publications

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“…10 [24]. In the case of series slag A, lines represent fixed molar ratios between CaO and SiO 2 together with lines representing fixed molar ratios between CaO and Al 2 O 3 [25][26][27]. For series slag B and C, the chemical composition are also selected to fix molar ratios of components as shown in Fig.…”

Section: Selected Resultsmentioning

confidence: 99%

Recent Development in the Investigation on Thermal Conductivity of Silicate Melts

Hasegawa¹,

Ohta

Shibata

et al. 2012

High Temperature Materials and Processes

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Accurate values of thermal conductivity of the silicate melts systematically measured as a function of chemical composition are necessary to understand a mechanism of heat transfer in the silicate melts. Hot wire method and laser flash methods have been used to measure thermal conductivity or thermal diffusivity of oxides melts at high temperatures. Laser flash method has been improved to measure thermal diffusivity of oxides melts with high accuracy. However the effects of radiative heat transfer and low electrical resistivity of samples have been made it difficult to derive precise values. To over come these difficulties, a frontheating frontdetection laser flash method with use of high time resolution detec tor has been proposed. The temperature response at the bottom surface of thin platinum cell containing sample irradiated by pulse laser is measured. The measurement techniques used for measurement oxide melts are com pared. Then, thermal conductivity of Al 2 O 3 Na 2 OCaOSiO 2 silicate melts was measured at temperature up to 1830 K. Thermal conductivity of the molten silicate shows insig nificant temperature dependence for all investigated melts. A fairly good correlation has been found between the thermal conductivity and the value of NBO/T (NonBridging Oxygen ions/Tetrahedrally coordinated cation) calculated from the chemical composition. The thermal conductivity increases with decrease of NBO/T for small NBO/T value and becomes constant for larger NBO/T value.

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Section: Selected Resultsmentioning

confidence: 99%

Recent Development in the Investigation on Thermal Conductivity of Silicate Melts

Hasegawa¹,

Ohta

Shibata

et al. 2012

High Temperature Materials and Processes

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“…Recently, Hasegawa et al pointed out that even in case of a molten CaO-Al2O3-SiO2 slag, current leakage may occur during thermal conductivity measurements using the hot wire method. 20,39) To elucidate the possibility of current leakage from a Pt-Rh hot wire during thermal conductivity measurement of various molten slags, the resistivity of the Pt-Rh wire has been estimated at their respective measurement temperatures. 40) In spite of the low resistivity of molten slag (0.01-0.05 Ohm·m), 41) the current passing through the slag sample is expected to be much less than that through the hot-wire (resistivity of 5.0-6.0 × 10 -7 Ohm·m).…”

Section: Non-steady-state Methodsmentioning

confidence: 99%

“…20,39) According to several previous researches using the laser flash method, the negligible temperature dependence of thermal conductivity of molten silicate was attributed to the constant mean free path, which will be equal to the unit cell size in fully depolymerized structure. In the laser flash method, however, the radiation effect on the heat transfer might be underestimated, resulting in the considerable difference in the temperature dependence.…”

Section: Temperature Dependence Of Thermal Conductivitymentioning

confidence: 99%

Thermal Conductivity of Molten Slags: A Review of Measurement Techniques and Discussion Based on Microstructural Analysis

Kang¹,

Morita²

2014

ISIJ Int.

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In order to properly interpret the thermal conductivity of molten silicate slags, several different measurement methods are briefly reviewed, along with a discussion as to their respective advantages and limitations. In addition, a large number of thermal conductivity values measured by these methods are assessed, in order to evaluate their dependence on composition and temperature. The behavior of the thermal conductivity of molten silicate slags was found to show good agreement with well-focused analyses into its microstructure. Moreover, with an improved understanding of the microstructure of silicate slags, there is an apparent co-relation between thermophysical properties such as thermal conductivity, viscosity, and so forth.KEY WORDS: thermal conductivity; molten slag; silicate; hot-wire method; laser flash method.

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“…These systems are sensitive to the presence of impurity elements, such as iron and manganese in solution, and second phase particles, e.g. Fe, and gas bubbles, all of which contribute to a decrease in optical transparency [111][112][113][114]. At present it is not possible to accurately predict these effects with the available information.…”

Section: Thermal Parametersmentioning

confidence: 99%

Fundamental studies on the chemical aspects of freeze linings

Crivits¹

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The application of freeze lining technologies has been shown to be highly effective in extending the working lives of pyrometallurgical furnaces operating under aggressive process conditions and corrosive liquid melts. Freeze linings are obtained by cooling the outer furnace walls, resulting in the formation of solid protective deposits on the inner walls of the furnace linings. Of particular interest to process operators are the freeze lining thickness and the heat loss through the furnace walls, both of which are directly related to the bath-freeze lining interface temperature.In most of the predictions for thermal steady state conditions, the assumption has been made that the temperature at the freeze lining/liquid interface is equal to the liquidus temperature of the bulk slag, and that the primary phase forms a dense sealing layer at this deposit/liquid interface. As a result of recent research on these systems, there is now extensive experimental evidence to demonstrate that the interface temperature can be below the liquidus and that the primary phase is not necessarily present at the deposit/liquid interface at thermal steady state conditions. These observations clearly indicate that other factors, in addition to thermal parameters of the system, need to be taken into account in the design of freeze lining systems.In the present study, heat and mass transfer and elementary reaction steps, and the associated thermal, physical, and chemical factors that can influence freeze lining behaviour are identified.From experiments undertaken using CaCl2-H2O solutions, accurate measurements have been made of deposit growth and microstructural changes taking place in the deposit over time were directly observed. These experiments have demonstrated the importance of nucleation rate of the primary phase and the thermal history of the freeze lining.High-temperature experiments in the 'Cu2O'-'Fe2O3'-MgO-SiO2 system in equilibrium with metallic copper have clearly demonstrated that at thermal steady state, bath/freeze lining interface temperatures are lower than the liquidus temperatures, and the possibility of operating processes at subliquidus bath temperatures. These experiments also indicated that an increase in bath temperatures results in an increase of the steady state interface temperature.High-temperature experiments in the Al2O3-CaO-SiO2 system were designed to study the effect of slag viscosity. Differences in the characteristics of the deposit/liquid interface were observed, however, it was unclear whether the observed differences in freeze lining behaviour were caused by the changes in viscosity, or the differences in morphology of the primary phase. The spontaneous decrepitation of freeze linings containing the dicalcium silicate phase on cooling clearly illustrated iv the need for caution when designing freeze lining systems that may form compounds undergoing significant changes in volume due to polymorphic transformations.The research supports the view that deposit/liquid interface temperatures in ...

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Thermal Conductivity Measurements of Some Synthetic Al2O3-CaO-SiO2 Slags by Means of a Front-Heating and Front-Detection Laser-Flash Method

Cited by 29 publications

References 31 publications

Recent Development in the Investigation on Thermal Conductivity of Silicate Melts

Recent Development in the Investigation on Thermal Conductivity of Silicate Melts

Thermal Conductivity of Molten Slags: A Review of Measurement Techniques and Discussion Based on Microstructural Analysis

Fundamental studies on the chemical aspects of freeze linings

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