Numerical Study of Fluid Flow Behaviors in an Alkali-Free Glass Melting Furnace

Yen, Chih−Hung; Hwang, Weng-Sing

doi:10.2320/matertrans.mra2007259

Cited by 10 publications

(5 citation statements)

References 7 publications

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“…Mathematical models of glass melting in an electric furnace tend to ignore the effect of the cold cap on melter performance. − A few models have considered the interactions between the reacting feed and the melt surface, , but until recently, the foam layer between the reacting feed layer and the melt has not been considered . Pokorny and Hrma ,, developed a model that accounts for these factors and their effects on glass production.…”

Section: Introductionmentioning

confidence: 99%

Temperature Distribution within a Cold Cap during Nuclear Waste Vitrification

Dixon

Schweiger

Riley

et al. 2015

Environ. Sci. Technol.

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The kinetics of the feed-to-glass conversion affects the waste vitrification rate in an electric glass melter. The primary area of interest in this conversion process is the cold cap, a layer of reacting feed on top of the molten glass. The work presented here provides an experimental determination of the temperature distribution within the cold cap. Because direct measurement of the temperature field within the cold cap is impracticable, an indirect method was developed in which the textural features in a laboratory-made cold cap with a simulated high-level waste feed were mapped as a function of position using optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. The temperature distribution within the cold cap was established by correlating microstructures of cold-cap regions with heat-treated feed samples of nearly identical structures at known temperatures. This temperature profile was compared with a mathematically simulated profile generated by a cold-cap model that has been developed to assess the rate of glass production in a melter.

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Section: Introductionmentioning

confidence: 99%

Temperature Distribution within a Cold Cap during Nuclear Waste Vitrification

Dixon

Schweiger

Riley

et al. 2015

Environ. Sci. Technol.

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“…In the glass community, the term minimum residence time is used to describe such a time delay. 16,24 Because of this behavior, the old glass product can be saved for a certain FV period of time even after a batch with a new composition is introduced into the furnace. To take this effect into account, an improved reactor model might consist of a plug flow reactor (PFR) and a CSTR in series.…”

Section: Discussion On the Current Transition Practicementioning

confidence: 99%

“…However, it is a well-known fact that the glass furnace exhibits a long time delay (typically no less than 10 h in order to make bubble-free, completely melted glass) during the product transition. In the glass community, the term minimum residence time is used to describe such a time delay. , Because of this behavior, the old glass product can be saved for a certain period of time even after a batch with a new composition is introduced into the furnace. To take this effect into account, an improved reactor model might consist of a plug flow reactor (PFR) and a CSTR in series.…”

Section: Discussion On the Current Transition Practicementioning

confidence: 99%

The Optimal Product Transition In Glass Furnaces

2009

Ind. Eng. Chem. Res.

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Product change in glass furnaces is a common and challenging industrial problem generally associated with long transition times and possible ream defects. A reduction in the product turnover time implies a higher product yield and a reduced energy consumption. This turnover time relies to a large extent on the understanding of furnace dynamics. In this work, the disadvantages of the current transition practice (based on the concepts of minimum residence time and perfect mixing) are discussed. An optimization approach that is based on the residence time distribution of the glass furnace is tailored to accommodate practical implementation issues in the product transition control. Comparisons of the current transition practice and the proposed approach are made through computer simulations, which demonstrate that significant savings in the product turnover time are expected if the latter is used.

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“…The cold cap covers 90-95% of the melt surface. Mathematical models of melters have been well developed [1][2][3][4][5] in all aspects except for the batch melting, which has rarely been addressed in other than a simplified manner [6][7][8][9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Nuclear waste vitrification efficiency: Cold cap reactions

Hrma

Kruger

Pokorný

2012

Journal of Non-Crystalline Solids

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The cost and schedule of nuclear waste treatment and immobilization are greatly affected by the rate of glass production. Various factors influence the performance of a waste-glass melter. One of the most significant, and also one of the least understood, is the process of batch melting. Studies are being conducted to gain fundamental understanding of the batch reactions, particularly those that influence the rate of melting, and models are being developed to link batch makeup and melter operation to the melting rate.Batch melting takes place within the cold cap, i.e., a batch layer floating on the surface of molten glass. The conversion of batch to glass consists of various chemical reactions, phase transitions, and diffusion-controlled processes. These include water evaporation (slurry feed contains as high as 60% water), gas evolution, the melting of salts, the formation of borate melt, reactions of borate melt with molten salts and with amorphous oxides (Fe203 and AI 2 0 3 ), the formation of intermediate crystalline phases, the formation of a continuous glass-forming melt, the growth and collapse of primary foam, and the dissolution of residual solids. To this list we also need to add the formation of secondary foam that originates from molten glass but accumulates on the bottom of the cold cap.This study presents relevant data obtained for a high-level-waste melter feed and introduces a one-dimensional (10) mathematical model of the cold cap as a step toward an advanced threedimensional (3D) version for a complete model of the waste glass melter. The 1D model describes the batch-to-glass conversion within the cold cap as it progresses in a vertical direction. With constitutive equations and key parameters based on measured data, and simplified boundary conditions on the cold-cap interfaces with the glass melt and the plenum space of the melter, the model provides sensitivity analysis of the response of the cold cap to the batch makeup and me Iter conditions. The model demonstrates that batch foaming has a decisive influence on the rate of melting. Understanding the dynamics of the foam layer at the bottom of the cold cap and the heat transfer through it appears crucial for a reliable prediction of the rate of melting as a function of the melter-feed makeup and melter operation parameters. Although the study is focused on a batch for waste vitrification, the authors expect that the outcome will also be relevant for commercial glass melting.

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Numerical Study of Fluid Flow Behaviors in an Alkali-Free Glass Melting Furnace

Cited by 10 publications

References 7 publications

Temperature Distribution within a Cold Cap during Nuclear Waste Vitrification

Temperature Distribution within a Cold Cap during Nuclear Waste Vitrification

The Optimal Product Transition In Glass Furnaces

Nuclear waste vitrification efficiency: Cold cap reactions

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