Kinetics of Chromium Oxide Transformations in Glass Melting

The kinetics of chromium oxide transformations in glass batch under heating and in glass melt has been studied. The different degrees of transformation of CrO₃ and Cr₂O₃ is demonstrated. The conditions of equilibrium between chromium oxides in the case of their simultaneous presence in glass melt is determined. The conditions of the interaction between chromium and iron oxides in the glass melt are investigated, including the surface layer in which an equilibrium between the colorant oxides can be achieved in accordance with the reaction conditions and the composition of the gaseous atmosphere. The low reaction velocities in the glass melt are due to its high viscosity and low values of diffusion coefficients. __________ Translated from Steklo i Keramika, No. 8, pp. 3 – 5, August, 2005.     

Influence of the melting temperature and rate of cooling the melt to the glass making temperature on the redox equilibria Fe2+ ? Fe3+ and Cu+ ? Cu2+ in aluminum potassium barium phosphate glasses

This paper reports on the results of the investigation of aluminum potassium barium phosphate glasses that contain copper and iron additives and have compositions similar to the composition of the matrix of the KGSS 0180/35 neodymium phosphate glass used for fabricating large-sized active elements intended for high-power laser amplifiers with a high output energy. The redox equilibrium of iron ions has been studied as a function of the melting temperature of the glass (850, 1100, and 1300°C). The redox equilibrium of iron or copper ions and their contributions to the nonactive absorption coefficient of glasses prepared at the melting temperature (1100°C) or after cooling of the glass melt at different rates to the glass making temperature (850°C) have been investigated. It has been established that a decrease in the melting temperature of the glass leads to a shift in the redox equilibrium of iron ions toward the formation of Fe³⁺ ions. During cooling of the glass melt from 1100 to 850°C, the redox equilibrium of copper (iron) ions shifts toward the formation of Cu²⁺ (Fe³⁺) ions; in this case, the lower the rate of cooling the melt, the larger the shift. At the minimum rate of cooling the glass melt (250°C for 180 min), the contribution of copper ions to the nonactive absorption coefficient increases by 25%, whereas the corresponding contribution of iron ions decreases by 40%.     

耐高温抗侵蚀低着色二氧化锡电极

玻璃电熔具有节能、减排、高热效率等优点,正以全电熔和电辅助加热用于玻璃熔窑。钼是广泛用做玻璃电熔窑的电极材料,易还原的元素将严重腐蚀钼电极。二氧化锡陶瓷具有氧化气氛使用、抗玻璃侵蚀能力强的特点,适用于含Pb、As、Sb、F等玻璃。二氧化锡电极的基础系统是SnO2-Sb2O3-CuO。广州市岭南耐火材料有限公司生产二氧化锡电极的技术进步包括:减少或去除CuO以降低对玻璃的污染;双重或多重掺杂施主杂质以增加导电率;引入高熔点氧化物以降低升华、改善高温性能,发展了4种不同类型抗侵蚀性能优越的二氧化锡电极。已用于铅晶质玻璃、高光透过光学玻璃、光伏玻璃和光电子学玻璃。     

Intensification of fining of glass melt with centrifugal forces

The basic technological parameters for organization of fining of glass melt in a centrifugal force field were analyzed. The numerical values of the parameters which can accelerate glass melt fining by one order of magnitude in comparison to the rate of the process in ordinary glass melting furnaces were reported.     

The effect of equilibrium of heterovalent forms of iron on melting temperature and glass homogeneity in industrial production

The integrated analysis of iron equilibrium in industrial glass-melting float systems of different efficiencies is performed. The close correlation of iron concentration in glass, its melting temperature, and its homogeneity is demonstrated. Reasons for deteriorated glass melt homogeneity in continuous production are analyzed, and practical recommendations are issued. __________ Translated from Steklo i Keramika, No. 6, pp. 6–9, June, 2006.     

Shrinkage of an oxygen bubble rising in a molten glass

The mechanisms controlling the evolution of a bubble surrounded by molten glass are important to understand in order to improve melting in glass furnaces, particularly during a change in composition. In order to provide insight into this phenomenon, the behavior of an isolated bubble rising in molten glass is examined both experimentally and numerically.An experimental procedure developed specifically to observe, in situ, a rising bubble is described. Two soda-lime-silica compositions are tested, with low and high iron content, respectively.The numerical model used to describe bubble shrinkage is based on the results recently proposed in Pigeonneau (2009). A specific mass transfer coefficient is used for oxygen where the oxidation–reduction reaction of iron oxides is taken into account.A comparison between the experimental and numerical results shows the importance of the oxidation–reduction reaction of iron in the mass transfer of oxygen. The shrinkage rate of a pure O₂ bubble is enhanced with reduced molten glass iron content.     

Cr2O3含量对玻璃熔体黏度和熔化特性的影响

为了保证玻璃液顺利浇注成型,并为高炉渣和铬铁合金渣协同制备CaO-MgO-Al₂O₃-SiO₂-Cr₂O₃体系建筑微晶玻璃提供基础的工艺技术参数,采用FactSage7.1热力学软件绘制CaO-MgO-Al₂O₃-SiO₂-Cr₂O₃玻璃体系的五元相图,并通过试验探究基础玻璃熔体的黏度和熔化特性。结果表明,在FactSage7.1绘制的相图中,随着Cr₂O₃含量的增加,相图的液相区范围不断缩小,表明玻璃的进一步熔化受到阻碍。晶核剂 Cr₂O₃的质量分数由0.85%增加到2.05%的过程中,玻璃熔体黏度逐渐减小,熔化性温度逐渐升高,在采用熔融法制备CaO-MgO-Al₂O₃-SiO₂-Cr₂O₃体系基础玻璃时应使熔融温度高于1 469 ℃。Cr₂O₃含量增加会使基础玻璃熔化温度升高,具体表现为各组试样的软化温度、半球温度和流动温度均不断升高,因此应尽量降低基础玻璃原料配比中Cr₂O₃的含量。     

钠钙玻璃熔体电阻率测量影响因素及边界条件研究

玻璃熔体电阻率是设计玻璃电熔窑或电助熔窑的关键参数之一,研究玻璃熔体电阻率测量的边界条件对获得精确电阻率值极其重要。本文基于欧姆定律,构建玻璃熔体电阻率测量装置,探讨了馈入电压、交流电频率、试样颗粒尺寸和填充率等因素对钠钙玻璃熔体在900~1 450 ℃电阻特性的影响。结果显示,当馈入电压为2~10 V,交流电频率为1 kHz,试样颗粒尺寸为830~1 700 μm,填充率为80%,降温速率为2 ℃/min时,电阻率测量结果的误差在各温度段都小于1。该研究可以为玻璃熔体电阻率测量提供参考,进而支撑玻璃电熔窑及电助熔窑电加热系统的设计,实现难熔及易挥发玻璃的熔化。     

SELENIUM BLACK GLASS*

A black glass was made by melting a soda-lime-silica glass under a reducing atmosphere with the addition of 0.6% of selenium and 0.1% of cobalt carbonate, CoCO_s. The light absorption of a specimen about 0.01 inch thick in the range of 400 to 750 mp was superior to that of commercial black glass. The maximum transmission was 27% at 750 mp. The use of nickel and iron oxides is less effective than cobalt oxide for obtaining selenium black glass.     

Bi2O3对钠钙硅玻璃熔体性质的影响研究

浮法玻璃的熔化是在非常高的温度下进行的,且熔化和澄清占总能耗的60%左右。本文以降低浮法玻璃熔化温度为出发点,研究氧化铋的引入对浮法玻璃熔体性质、熔化温度、玻璃结构的影响。研究表明:在浮法玻璃组成中引入氧化铋,加入0.5%～2%的氧化铋后,未改变玻璃的基本结构。加入Bi₂O₃后玻璃熔体的粘度明显降低,在玻璃熔体粘度为Lgη=1.35 Pa·s时,A₅玻璃试样的对应温度与A₁相比,降低约30℃。     

Synthesis of Mullite from Slime of Normal Electrocorundum and Kaolin

Phase transformations in slime of normal electrocorundum upon heating in air and its high-temperature interaction with kaolin in steady and interspersing layers are studied. Preliminary oxidation of lower titanium oxides contained in slime is a necessary condition for obtaining mullite. The properties of mullite and retained glass are studied in detail. Mullite has a nonstoichiometric composition and forms solid solutions with titanium and iron oxides. It is assumed that their intensifying action in synthesis is a result of the lower viscosity of the alumosilicate melt.     

Expansion of the glass sand base with noncapital-intensive technologies

Even insignificant fluctuations (fractions of a percent) of such components as iron and aluminum oxides in glass melts cause serious changes in the rheological properties of the melt and heat-exchange conditions in the furnace and in the forming units. Noncapital-intensive technologies for concentration of the feedstock that improve the quality of glassware are proposed.     

漫谈高硼玻璃的电熔

阐述了高硼玻璃的熔制特性,通过对窑内玻璃液流温度分布的分析,认为用全电熔窑熔化高硼玻璃比较理想,并提出了相关注意事项.     

铁磷熔体的氧化还原态和导电性能

用电导率电池测量了含钠铁磷模拟放射性核废料（HLW）熔体的电阻率,并分析了相应玻璃的Moessbauer谱,计算了铁离子的价态和氧化还原比,分析了温度、时间和氧化钠含量对熔体电阻率和玻璃氧化还原比的影响。结果发现：在Na2O含量低的熔体中,升温和降温过程的电阻率的变化是不可逆的：随着Na2O含量增加,不可逆性消失,熔体的电阻率随时间轻微下降。同时发现：Na2O3含量低的铁磷熔体的导电机理是电子性的,并且氧化还原比解释了其电阻率－温度曲线的不可逆性。铁磷模拟HLW熔体的电阻率类似于相近Na2O含量的钠铁磷系统熔体的电阻率。     

Mass transfer of a rising bubble in molten glass with instantaneous oxidation-reduction reaction

The mass transfer around a rising bubble has been studied within the field of glass melting processes. Due to the large value of liquid viscosity, creeping flow was used. The rising bubble is assumed to have a clean interface with a total mobility and the exact solution of Hadamard or Rybczynski was used to define the velocity field around the bubble. The mass transfer of oxygen in the soda-lime-silica glass melt where oxidation-reduction reactions of iron oxides occur is also described.The dimensionless mass transfer coefficient, Sherwood number, was determined as a function of the Péclet number based on the terminal rise velocity of the bubble. Two different techniques have been used: the first based on the boundary layer theory and the second using a finite element method.In order to take into account the oxidation-reduction reaction in a unified framework, a modified Péclet number has been defined as a function of two dimensionless numbers. The first is strongly linked to the equilibrium constant of the chemical reaction and the second is the glass saturation, defined as the ratio of oxygen concentration in the bulk to that at the bubble surface. The Sherwood number, taking into account the chemical reactions, increases with iron content as well as with glass reduction (i.e. small saturation level).From an application point of view, the determination of a modified Péclet number is important because it is possible to use a similar expression (determined without the reaction) by replacing the classical Péclet number by the modified one proposed herewithin.     

Effect of network connectivity on behavior of synthetic Broborg hillfort glasses

There is wide industrial interest in developing robust models of long-term (>100 years) glass durability. Archeological glass analogs, glasses of similar composition, and alteration conditions to those being tested for durability can be used to evaluate and inform such models. Two such analog glasses from a 1500-year-old vitrified hillfort near Uppsala, Sweden have previously been identified as potential analogs for low concentration Fe-bearing aluminosilicate nuclear waste glasses. However, open questions remain regarding the melting environment from which these historic glasses were formed and the effect of these conditions on their chemical durability. A key factor to answering the previous melting and durability questions is the redox state of Fe in the starting and final materials. Past work has shown that the melting conditions of a glass-forming melt may influence the redox ratio value (Fe⁺³/∑Fe), a measure of a glass's redox state, and both melting conditions and the redox ratio may influence the glass alteration behavior. Synthetic analogs of the hillfort glasses have been produced using either fully oxidized or reduced Fe precursors to address this question. In this study, the melting behavior, glass transition temperature, oxidation state, network structure, and chemical durability of these synthesized glass analogs is presented. Resulting data suggests that the degree of network connectivity as impacted by the oxidation state of iron impacted the behavior of the glass-forming melt but in this case does not affect the chemical durability of the final glass. Glasses with a lower degree of melt connectivity were found to have a lower viscosity, resulting in a lower glass transition temperature and softening temperature, as well as in a lower temperature of foam onset and temperature of foam maximum. This lower degree of network connectivity most likely played a more significant role in accelerating the conversion of batch chemicals into glass than the presence of water vapor in the furnace's atmosphere. Future work will focus on using the results from this work with outcomes from other aspects of this project to evaluate long-term glass alteration models.     

矿物原料对SiO_2-Al_2O_3-MgO玻璃熔制的影响研究

目前SiO_2-Al_2O_3-MgO系统的S级高强玻璃纤维生产主要以石英砂、氧化铝、重质氧化镁等化工级原料分别引入玻璃组分中的各氧化物实现。这些化工原料纯度高,有助于提高产品成分和性能的稳定性,但这些原料在熔制过程中需要更高的熔制温度,具有能耗大、玻璃液的澄清及均化困难等缺点。为改善SiO_2-Al_2O_3-MgO系统S级高强玻璃的熔制工艺性能,开展了在玻璃原料中引入高岭土、滑石粉的熔制实验,研究矿物原料对高强玻璃熔制的影响规律。通过DSC分析了玻璃的特征温度点,利用XRD表征了熔制过程中配合料的物相变化情况,并在快速升温炉中进行了配合料的熔制实验观测,同时进行了新生态玻璃纤维的强度测试。研究表明:采用矿物原料能显著降低配合料的熔制温度,降低熔制能耗,改善特种玻璃熔制的工艺性能,形成玻璃的温度降低50℃以上;同时也发现矿物原料中的Fe~(2+)含量较大,增加了玻璃液的温度梯度,玻璃液表面温度低,不利于玻璃液的澄清,因此需要采取措施降低矿物原料中Fe~(2+)的含量,以改善玻璃液的澄清效果,避免玻璃纤维的性能受到影响。     

瓶罐玻璃生产关键工艺性能测量方法与应用

综述了瓶罐玻璃生产制备过程中的关键工艺性能的测量表征方法和适用的仪器设备。涉及的关键工艺性能主要包括熔解特性、熔体特性和温黏特性等。熔解特性的分析包括原料成分分析、粒度分析、熔化均匀性分析、澄清分析等;熔体特性的测量包括表面张力测量、高温电阻率测量、羟基含量测量等;温黏特性测量主要包括高温黏度(熔融温度T_m、工作点T_w、液相线T_L)测量、中温黏度(软化点T_s)测量、低温黏度(膨胀软化点T_d、退火点T_a、转变点T_g和应变点T_st等)测量。上述工艺性能精确测量和表征,对制备高质量瓶罐玻璃制品具有重要意义。     

硅砂对高碱铝硅酸盐玻璃熔解特性的影响研究(英文)

通过固定熔制工艺制度,研究了硅砂原料粒径大小、分布情况、颗粒形态对高碱铝硅酸盐玻璃熔解特性的影响关系。研究结果表明:在玻璃配合料熔制过程中,白色未熔物的产生与石英砂密切相关,石英砂粒径处于45-150μm范围熔化效果最好,石英砂粒度分布为正态分布的熔化效果优于均匀分布,经过粒化处理的石英砂比破碎处理的熔化特性更优,可促进玻璃的熔化。     

Interaction between a UO2+x -ZrO2-Fe(Cr, Ni)Oy melt and a concrete based on ZrO2

The results presented below concern the process of interaction between molten oxidized corium and zirconia concrete. Experiments were performed with the use of induction melting of corium in a cold crucible. Experimental data on the ablation rate are presented. The experimental data are used to propose a simplified model for evaluating the ablation rate under the assumption that it is proportional to the degree of nonsaturation of the melt. An empirical dependence of the coefficient of proportionality on the corium temperature and the initial concentration of iron oxides in the melt is presented. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 1, pp. 28–32, January, 2000.