Rheology of simulated radioactive waste slurry and cold cap during vitrification

McCarthy, Benjamin P.; George, Jaime L.; Dixon, Derek R.; Wheeler, M.J.; Cutforth, Derek; Hrma, Pavel R.; Linn, Diana T.; Chun, Jaehun; Hujova, Miroslava; Kruger, Albert A.; Pokorný, Richard

doi:10.1111/jace.15755

Cited by 15 publications

(17 citation statements)

References 23 publications

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“…In the foam layer, which separates the reaction zone in the cold cap from molten glass under the cold cap (Figure ), heat is transferred via conduction in the liquid, thermal radiation and conduction in the gas, and local convection currents (mixing). The reacting feed layer consists of the dry core layer and the conversion layer . If melter feed is charged on the cold cap surface in the form of aqueous slurry, the boiling water periodically floods parts of the cold cap surface .…”

Section: Heat Transfer To Cold Capmentioning

confidence: 99%

“…The reacting feed layer consists of the dry core layer and the conversion layer . If melter feed is charged on the cold cap surface in the form of aqueous slurry, the boiling water periodically floods parts of the cold cap surface . After the free water evaporates, removal of chemically bonded water (dehydration) proceeds in the top portion of the core layer.…”

Section: Heat Transfer To Cold Capmentioning

confidence: 99%

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Heat transfer from glass melt to cold cap: Melting rate correlation equation

Hrma

Pokorný

Lee

et al. 2018

Int J of Appl Glass Sci

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The efficiency of all-electric melters is a hot topic not only in the waste glass melting industry, but also in the commercial melting industry, where stringent environmental regulations and rapid development of renewable energy ask for transformation of current technologies. The heat transfer for the batch conversion into molten glass is controlled by convection and conduction in the thermal boundary layer on the melt side, and by the properties of the foam layer at the batch/melt boundary. An overview of factors affecting heat transfer is presented and assessed using data from laboratory-and pilot-scale experiments. Aside from increasing the melter operating temperature, the heat flux can be enhanced by (a) lowering glass melt viscosity, (b) decreasing the temperature at which the foam collapses at the cold cap bottom, and (c) increasing the melt convection. Although the melt viscosity depends on glass composition, limited by the desired product properties, the understanding of foaming behavior can guide the selection of batch materials that foam less and melt easily. Since a rigorous formulation of the complex region at the cold cap bottom has not been developed yet, the boundary layer approach was adopted to obtain a semiempirical relationship between the melting rate and experimentally accessible feed properties. K E Y W O R D Scold cap, feed-to-glass conversion, foam layer, heat flux, melting rate, thermal boundary layer

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Section: Heat Transfer To Cold Capmentioning

confidence: 99%

Section: Heat Transfer To Cold Capmentioning

confidence: 99%

Heat transfer from glass melt to cold cap: Melting rate correlation equation

Hrma

Pokorný

Lee

et al. 2018

Int J of Appl Glass Sci

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“…Because primary foam is complex, inaccessible, and difficult to simulate in the laboratory, its rheology has not been fully investigated yet. Several attempts have been made to measure the viscosity of foaming melter feed at the stage where the glass‐forming melt has connected, but so far they only succeeded when the foam was collapsing …”

Section: Resultsmentioning

confidence: 99%

“…For viscosity measurement, ~120 g of glass batch was heated from room temperature to target temperatures (950°C, 1050°C, 1150°C, and 1250°C) at 10 K min −1 and held for 30 minutes. To measure feed and glass viscosities of two selected melter feeds (HWI‐Al‐19 and HLW‐E‐Al‐27) during increasing and decreasing temperatures, ~50 g powdered batched feed was placed in a Pt crucible, loaded in an Anton Paar FRS1600 viscometer, and heated from room temperature to 1150°C at 5 K min −1 , held for 30 minutes at 1150°C, and cooled down at 5 K min −1 …”

Section: Experimental Approachmentioning

confidence: 99%

“…Several attempts have been made to measure the viscosity of foaming melter feed at the stage where the glass-forming melt has connected, but so far they only succeeded when the foam was collapsing. 10,11,53,56,57 Figure 5 shows our most recent viscosity results for two high-alumina melter feeds. The blue lines represent the viscosity of heat-treated melter feeds that are almost completely molten (though still containing small fractions of undissolved solids; see Table 2) and contain both primary and secondary bubbles (gases evolving from batch reactions and from redox reactions, respectively).…”

Section: Feed-to-glass Mass Ratio δH R (J G −1 )mentioning

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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