Heat transfer from glass melt to cold cap: Gas evolution and foaming

Hrma, Pavel R.; Kloužek, Jaroslav; Pokorný, Richard; Lee, Seung Min; Kruger, Albert A.

doi:10.1111/jace.16484

Cited by 16 publications

(22 citation statements)

References 54 publications

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“…The FET curves allow obtaining the minimum volume, V FO , to which the feed shrinks as foaming starts at the foam onset temperature, T FO , and the maximum volume, V FM , reached at the foam collapsing temperature, T FM . The solid green data points in Figure mark the FET curve for a foaming segment to which we fitted a third‐order polynomial function of the form V / V G = a 0 + a 1 ( T /1000) + a 2 ( T /1000) 2 + a 3 ( T /1000) 3 , where V G is the final glass melt volume ( V / V G is the normalized volume), and a 0 , a 1 , a 2 , and a 3 are fitted coefficients . The values of T FO and T FM then are T FO =

1000 (- a_{2} + \sqrt{a_{2}^{2} - 3 a_{1} a_{3}}) / 3 a_{3}

and T FM =

1000 (- a_{2} - \sqrt{a_{2}^{2} - 3 a_{1} a_{3}}) / 3 a_{3}

, and the maximum porosity is ψ M = 1 − V G / V FM .…”

Section: Resultsmentioning

confidence: 99%

“…The feed‐to‐glass mass ratio was obtained using TGA. DSC data were used to estimate the reaction heat, H R , for the temperature interval from 100°C to T FO . Table lists the pertinent property values for the feeds selected.…”

Section: Resultsmentioning

confidence: 99%

“…As soon as T MO is reached, the melt fraction is close to 100% and the viscosity is close to that for which the glass was formulated. Recollect that the foam collapsing temperature, identified as the maximum foam temperature measured by FET, and the cold‐cap bottom temperature are assumed equal, that is, T B = T FM . Accordingly, the T FM represents the cold‐cap bottom temperature (this is acceptable for melter feeds exhibiting moderate and elevated foaming; EGA data are needed to assess foam collapsing temperature for vigorous, turbulent foams).…”

Section: Resultsmentioning

confidence: 99%

“…The TBL is a region of thickness d B = Δ T /[d T /d y | y =0 ], where y is a vertical coordinate with the origin under the cold‐cap bottom and Δ T = T MO − T B is the difference between the melter operating temperature, T MO , and the cold‐cap bottom temperature, T B . The Δ T ranges from 200 to 450 K. The temperature difference across the primary foam (between T B and the foam onset temperature, T FO , see Figure ) varies from 70 to 360 K . Consequently, within both the TBL and the primary foam layer, melt viscosity changes drastically.…”

Section: Introductionmentioning

confidence: 99%

“…[37‐40] and compared the results to actual feed and glass viscosities measured by rotating‐spindle viscometer. The feed expansion test (FET) and evolved gas analysis (EGA) allowed us to determine the T FO and T B values. Using a thermogravimetric analyzer with differential scanning calorimetry (TGA‐DSC) and X‐ray diffraction (XRD), we were able to estimate the melt composition.…”

Section: Introductionmentioning

confidence: 99%

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Viscosity of glass‐forming melt at the bottom of high‐level waste melter‐feed cold caps: Effects of temperature and incorporation of solid components

et al. 2019

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During the final stages of conversion of melter feed (glass batch) to molten glass, the glass‐forming melt becomes a continuous liquid phase that encapsulates dissolving solid particles and gas bubbles that produce primary foam at the bottom of the cold cap (the reacting melter feed in an electric glass‐melting furnace). The glass‐forming melt viscosity plays a dominant role in primary foam formation, stability, and eventual collapse, thus affecting the rate of melting (the glass production rate per cold‐cap area). We have traced the glass‐forming melt viscosity during the final stages of feed‐to‐glass conversion as it changes in response to changing temperature and composition (resulting from dissolving solid particles). For this study, we used high‐level waste melter feeds—taking advantage of the large amount of data available to us—and a variety of experimental techniques (feed expansion test, evolved gas analysis, thermogravimetric analyzer‐differential scanning calorimetry, X‐ray diffraction, and viscometer). Starting with a relatively low value at the moment when the melt connects, melt viscosity reached maximum within the primary foam layer and then decreased to its final melter operating temperature value. At the cold‐cap bottom—the boundary between the primary foam layer and the thermal boundary layer—where physicochemical reactions of a melter feed influence the driving force of the heat transfer from the melt to the cold cap, the melt viscosity affects the rate of melting predominantly through its effect on the temperature at which primary foam is collapsing.

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