Viscous deformation as a measure of heat work during coal ash fusibility testing

Hsieh, Peter Y.

doi:10.1016/j.fuel.2020.118723

Cited by 7 publications

(13 citation statements)

References 45 publications

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“…Heat work was measured in pyrometric cones by the viscous deformation. 29,30 Pyrometric cones demonstrate that soaking a furnace at a lower temperature generated a densification result similar to that observed for a shorter time at higher temperature. The amount of heat work, or thermal energy, required for viscous sintering to occur should be similar for all heating rates.…”

Section: Resultssupporting

confidence: 54%

Section: Resultsmentioning

confidence: 99%

“…The combined effect of temperature and time is termed “heat‐work.” 29 Pyrometric cones were invented to assess the heat work in the firing of traditional ceramic bodies such as porcelain and stoneware. Heat work was measured in pyrometric cones by the viscous deformation 29,30 . Pyrometric cones demonstrate that soaking a furnace at a lower temperature generated a densification result similar to that observed for a shorter time at higher temperature.…”

Section: Resultsmentioning

confidence: 99%

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The role of heating rate on the sintering of glass powders

Stevens

Carty

2022

Int J of Appl Glass Sci

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It is proposed that heating rate affects the apparent sintering temperatures of glass powders. The accumulation of thermal energy over time, or heat work (K s), is calculated over the range from the glass transition temperature to sintering temperature with the logarithm of time for heating rates from 1 to 60 K/min. The required heat work is independent of heating rate for two silicate glass powders but shows a decreasing heat work requirement for increasing heating rates for a borosilicate glass powder. Small cylindrical powder compact samples were used to minimize heat-transfer problems and were observed thermoanalytically using a hot-stage microscope. The densification temperature, defined as the peak in the shrinkage versus temperature curve, increases with increasing heating rate and is sensitive to the initial compact density. The use of mechanically pressed compacts with similar compact densities minimizes the contribution of initial density, allowing the comparison of sintering behavior as a function of heating rate.

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Section: Resultssupporting

confidence: 54%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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The role of heating rate on the sintering of glass powders

Stevens

Carty

2022

Int J of Appl Glass Sci

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“…It has been used previously to study the viscous deformation of pyrometric cones 15 and the fusibility of coal ash. 16 Lastly, the Einstein-Roscoe equation 17 is used to calculate the effective viscosity of subliquidus melts as a function of the intrinsic viscosity and solid volume fraction. The equilibrium viscosity of fully molten and partly molten raw glazes can thus be estimated readily as a function of composition, temperature, and oxygen activity.…”

Section: Introductionmentioning

confidence: 99%

“…The modified quasichemical model (MQM) 14 is a promising candidate, as it is based on the molten phase structure, specifically the molar fraction of free, bridging, and non‐bridging oxygen atoms present. It has been used previously to study the viscous deformation of pyrometric cones 15 and the fusibility of coal ash 16 . Lastly, the Einstein‐Roscoe equation 17 is used to calculate the effective viscosity of subliquidus melts as a function of the intrinsic viscosity and solid volume fraction.…”

Section: Introductionmentioning

confidence: 99%

Thermophysical modeling of raw glaze liquidus temperature and viscosity

Hsieh

2022

Int J of Appl Glass Sci

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Raw glazes, which do not contain pre‐melted glass frits, are widely used due to their low cost. The natural variability of the mineral compositions used in raw glazes affects their viscosity during firing. Molten glaze viscosity plays an important role in determining the final surface quality; therefore, it is important to determine how raw glaze composition and firing conditions affect viscosity. Thermophysical modeling provides a way to evaluate the liquidus temperature and viscosity of molten glazes as a function of composition and oxygen activity. Equilibrium phase volume fraction and composition of 242 raw glaze recipes were evaluated under oxidizing and reducing conditions. Undissolved or precipitation of solid phases explains the secondary flux transition from anti‐fluxing to fluxing near the liquidus temperature. The liquidus temperature and viscosity of iron glazes decrease as a function of increasing iron content under a reducing atmosphere. The empirical probability distribution of molten glaze viscosity follows a lognormal distribution, with lead glazes having significantly lower viscosity compared with glazes without lead. The peak firing temperature viscosity of lead‐free glazes is near the working point of glass. Multiple linear regression analysis shows that the peak firing temperature viscosity and liquidus temperature significantly predict the viscosity factor.

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