Study of the Float Glass Melting Process: Combining Fluid Dynamics Simulation and Glass Homogeneity Inspection

Zhao, Feng; Li, Dongchun; Qin, Guoqiang; Liu, Shimin

doi:10.1111/j.1551-2916.2008.02606.x

Cited by 25 publications

(17 citation statements)

References 10 publications

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“…The mass balances of the condensed phase and the gas phase are (1) (2) where t is the time, p the spatial density, v the velocity, r the mass source associated with reactions, and the subscripts band 9 denote the condensed phase and the gas phase, respectively. The mass fluxes,jb andjg, respectively, are ib = -Pb Vb (the minus sign in is used because the condensed phase moves in the negative direction) and j g = P g V g • The energy balance for the condensed phase is: (3) where Tis the temperature, e is the heat capacity, q is the heat flux, H is the internal heat source, and. To solve the energy balance equation, we used, for the sake of simplicity and comprehensibility, the finite difference method.…”

Section: Theorymentioning

confidence: 99%

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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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Section: Theorymentioning

confidence: 99%

“…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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“…It is better that glass flow is twodimensional in melter, and involves side current to the minimum in working end. 4) In usual float furnace, thermal convection in depth, z, and longitudinal direction, x, has a dominant role to transport heat or chemical species in glass melt. Molten glass flow is divided into upstream and downstream circulation.…”

Section: Mathematical Modelmentioning

confidence: 99%

“…1), 2) Glass flow plays an important role to nucleate, transport, and decrease bubbles. Many researchers have tried to solve glass flow 3), 4) and related the numerical result to bubble quality. 5) Mathematical model of glass flow is necessary to design and operate the furnace, but it is not a sufficient tool to predict bubble quality.…”

Section: Introductionmentioning

confidence: 99%

Mathematical model of bubble number density in glass tank furnace

Oda

Kaminoyama

2009

J. Ceram. Soc. Japan

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There have been innumerable contributions to clarify bubble behaviour in glass melt, where various approaches have been carried out. Experimental results show bubble quality is represented by bubble number density, bubble diameter, and standard deviation of the diameter, which depend on time and temperature. The latest experiment implies growth of bubble is strongly dependent on temperature, and the standard deviation is independent of time and temperature. Not only appeared location but also number density of small bubble (seeds) is of major concern for manufacturers to produce high quality glass. A new mathematical model is developed to predict bubble number density, which quantifies effect of both fining and refining on the density by introducing an exhausting effect of bubbles from upstream of the highest temperature area, i.e. hot spot, and the downstream in melter, i.e. stagnant. Inlet bubble number density with melting down is extrapolated from the published data. Monitored diameter obtained in experiment is applied to calculation. Calculated bubble number density is compared with measured one in an actual flat glass furnace, which makes it clear that the mathematical model is valid to predict order of the density in the glass melt. Numerical simulation gives reasonable suggestion about fining effect.

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“…But if the viscosity of glass is too low, glass belt will become thinner and be quickly pulled off, so the temperature in flatting and polishing region can not be too high. Therefore, according to the flatting time of soda-lime-silica float glasses [7][8][9][10][11] , and considering cost and production efficiency, the flatting time of LAS glass should be selected in the range of 1 250 ℃ to 1 300 . -- Fig.4 The connection between flatting time and surface/visicosiy ratio…”

mentioning

confidence: 99%