DESIGN OF A FURNACE FOR ANNEALING OPTICAL GLASS1

Design of a natural-gas furnace for annealing optical glass.—Most of the furnaces built for annealing regular glassware are unsuitable for optical glass due to irregularity and inequality of temperatures. Working drawings are given for a successful optical glass annealing furnace operated by natural gas. The design is novel in the placing of the flues and burners in such a manner as to supply the heat and remove it in a symmetrical manner, thus obtaining uniformity of temperature.     

OPERATION OF LEERS1

The muffle and open types of leers are compared. The latter has the following advantages: (1) More uniform temps. in the annealing chamber; (2) prevents ingress of cold air beside pans and thus avoids consequent cracking of the ware; (3) better control of temp. and greater reliability of pyrometric indications; (4) less fuel per gross of ware. Size of leers: Leers 8 ft. wide and 65 ft. from center to center of sprockets are recommended for the average glass. Leer chains: Chains having a working strain of 5800 Ibs. at 200 ft. per minute are recommended. In the discussion, L. H. Adams points out that the exact annealing schedule required for any glass can be computed from the annealing constants of the glass which are known or can be determined in the laboratory.     

Fine Annealing of Optical Glass

Since the most important characteristic of optical glass is the uniformity of its refractive index, which is itself a function of fictive temperature, any fine annealing treatment must be such as to bring about substantial uniformity in fictive temperature. Methods of accomplishing this are reviewed. In terms of total required time in the annealing process, the most efficient method consists of soaking the glass for a short time at a temperature near the annealing point and cooling at a constant rate to a temperature below the annealing range and at an increased rate to room temperature. Formulas are given for specifying the parameters in the annealing schedule in terms of the final condition of the glass as to stress and index. The several outstanding advantages of this method of annealing are discussed.     

High-precision molding simulation prediction of glass lens profile for a new lanthanide optical glass

Precision glass lens molding (PGLM) is a recently developed method for fabricating glass optical components with high precision in large volumes. Lanthanum optical glasses are extensively used as optical materials owing to their superior optical properties, such as high refractive index, low dispersion, and high transparency. However, the transformation temperature of currently available high refractive index glass is generally above 650 °C and poses a challenge in manufacturing ultra-hard molds, durable coatings, and high-temperature molding equipment using PGLM. In this study, a preparation method for obtaining high refractive index, low -melting -point lanthanide optical glass (B-ZLaT198) used in PGLM was developed to reduce the transformation temperature. The developed method also characterizes the glass refractive indices and thermal-mechanical properties. To achieve the high-precision prediction of a molding shape in a simulation, a viscoelastic constitutive model of glass was established based on a micro-deformation uniaxial compression creep test. Moreover, by solving the Tool-Narayanasway-Moynihan model parameters based on the specific heat capacity fitting of optical glass at different heating and cooling rates, the input parameters of the structural relaxation model (SRM) for simulation prediction of aspheric glass lens profile deviation in the annealing stage were obtained. Finally, the profile deviation of the aspheric lens was predicted using a finite element model simulation. The results showed that the simulation’s predicted profile of an aspheric lens using the SRM model was in good agreement with that of experimental molding profile. In addition, using the SRM provided a higher prediction accuracy than that of the thermal expansion model in the annealing stage. Adopting the SRM was necessary for the annealing simulations of molding pressing and also verified the accuracy of the proposed viscoelastic characterization method for calculating the thermomechanical parameters of optical glasses.     

玻璃光纤传像束排丝设备控制系统的改进

传像束排丝设备是制作玻璃光纤传像束的关键设备,通过对原有排丝设备的简述,了解到它的局限性。根据市场的需求提出了全新排丝设备的设计思想,不仅能够制作常规传像束还能够制作大截面的光纤传像束。经过设计安装调试,在实际的应用中效果良好,扩大了产品的制做种类,提高了产品的质量。     

Maintenance repair of the refractory lining of glass furnaces

The problem of increasing the service life of glass furnaces with the aim of reducing expenses is solved most effectively by using the method of depositing refractory powders onto the internal surface of fractured regions by an oxygen torch. The high efficiency of the facing has been confirmed by the service life of glass furnaces of different design, output, and purpose with the thus repaired roofs, walls, and other parts. The repair is performed using domestic equipment and powders. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 6, pp. 44–45, June, 2000.     

ELECTRIC ANNEALING OF GLASS*

The total and distribution heat requirements are discussed in general as well as the manner in which electric leers economically meet these requirements based on actual determinations and calculations.     

VARIATIONS CAUSED IN THE HEATING CURVES OF GLASS BY HEAT TREATMENT1

The variations produced in the heating curves of a glass by previously subjecting it to different heat treatments are often fully indicative of the nature of these previous treatments, and they also bear a relation to changes caused in numerous other characteristics of glass by this same means. The differences in the heating curves arise from differences in the thermal properties of the glass and especially from changes in the magnitude and character of the exothermic and endothermic effects. The physico-chemical processes causing the endothermic are the reverse of those producing the exothermic, i.e., the two effects are related as in the case of the similar and well-known phenomena observed at an inversion point such as is found in many crystals. They are, however, not confined to the usual relatively narrow temperature ranges and are also much more subject to undercooling and superheating. Apparently this resistance to the physico-chemical processes increases rapidly as the temperature is lowered making it possible by rapid cooling to suppress the exothermic processes to a great extent and thereby prepare the way for relatively large exothermic effects on subsequent heating. Since the preparatory exothermic activity is insufficient, the endothermic effects in the heating curves of chilled glasses are never pronounced but may become quite large in these curves if in the annealing, the exothermic processes have the opportunity to continue their activity into the range of relatively low annealing temperatures. During annealing the exothermic activity progresses more and more slowly toward a limit which may be advanced by reducing the annealing temperature. The physicochemical condition which the glass would have if the limit for any given annealing temperature were reached is termed the equilibrium condition of the glass for that temperature and such an equilibrium is presumably kinetic in character. The continuous series made up of all these equilibrium conditions corresponding to the various temperatures in the annealing range is called the equilibrium sequence. It is shown that about any portion of such a sequence, a glass may be made to follow any number of apparently closed cycles and that in traversing these cycles it passes through a series of intermediate conditions which in general do not coincide with the equilibrium sequence except where this is practically insured by very thorough annealing at constant temperatures. At ordinary atmospheric temperatures, the usual type of glass is always in such an intermediate series since in ordinary practice it is impossible to extend the realizable equilibrium sequence tci temperatures much below the lower limit of the practical annealing range. In this range, however, very low rates of cooling or heating will cause a glass to follow its equilibrium sequence with relative closeness after coincidence has once been practically established. In view of the present insufficient knowledge concerning the constitution of glass, the particular processes involved in these changes of physico-chemical condition are presumably too complex and varied for analysis. Apparently, however, the activity of the exothermic type gives rise to a series of molecular readjustments which often limit the ability of the glass to reach other conditions having possibly greater stability especially at relatively low temperatures. In some cases these readjustments may insure a greater permanency to the vitreous state as long as the glass is not heated above the temperatures producing them. A relatively clear conception of these readjustments and of the general behavior of glass in the annealing range may be gained from a consideration of the changing conditions in any physico-chemical system, e.g., a solution, where the equilibrium condition depends upon the temperature but normally does not change simultaneously with it. From the standpoint of investigating certain properties and characteristics, systems like glass yield advantages since their reaction rates are low and give opportunity for many observations during any change of importance and also since the thermal effects caused by superheating and undercooling are readily detectable. The relation which the changes in physico-chemical condition bear to certain problems in practical annealing is also considered, and from the discussion it is evident that annealing procedures may often be manipulated so that the resultant changes in certain propertics (notably the refractivity) will cause a glass to meet standards of requirement which it would normally fail to reach if annealed according to a fixed schedule prescribed for its general type. Although the tolerances of present-day standards are so lenient that adjustments of this character are seldom required or employed, it is believed that the time is rapidly approaching when an extended use will be made of them especially in those cases where a highly-standardized production of optical instruments of great precision is attempted. More important from the optical instrument standpoint, however, is the need of always annealing a glass in such a way that the physicochemical condition is fully uniform throughout the whole piece or blank from which an optical part is produced. In many cases gradients no greater than a small fraction of a degree will, if they exist during annealing, produce nonuniformities which cause greater disturbances than strains of considerable magnitude.     

浮法玻璃四支撑输送辊道的安装与调试

浮法玻璃生产线冷端四支撑辊道由2组2支撑结构的辊道组成,两侧辊道之间的辊子用梅花联轴器相连。由于四支撑辊道的架子由4条大梁组成,所以辊子全部组装后我们不能在精调辊子的过程中对误差较大的某区域单独调节;而且4支撑辊道发生跑偏时修正工作量大、难度高。本文就如何保证四支撑辊道安装精度、预防玻璃跑偏,针对放线、架子组装、辊子组装及调试等工作提出了一些方法。     

THE FLOW OF GLASS IN TANKS*

The paper deals with the flow of glass in tank furnaces. Reference is given to previous work on this subject. Experimental data are given for water and other liquids and the physical principles are discussed. Illustrations indicate the direction of flow in a glass tank.     

模拟技术在新池窑设计中的实际应用

设计一个运行性能优良、可控性好的熔窑，是玻璃熔窑设计师追求的重要目标。单纯凭经验设计难以达到这一目标，借助于模拟技术有可能做到这一点。本文报道运用模拟技术设计玻璃池窑的一个实例。文中简要介绍了模拟技术本身必须的改进或发展以及模拟技术实施的步骤，图示了若干模拟结果。按照模拟技术提供的优化方案建成的玻璃池窑，经过近2年时间的运行，性能相当令人满意。该池窑具有滴料后调整时间短、可控性好、运行稳定、抗干扰能力强、熔制玻璃质量高等优点。     

玻璃熔制过程三维数学模拟的运用

采用所建立的玻璃的熔制过程的三维数值模型对彩色显微管玻璃熔窑进行模拟,详细研究了不同壁面散热和两通道引出量不对称条件对玻璃熔制过程的影响。三维数值模拟的结果可以真实地反映玻璃熔池实际运行过程,有助于加深对玻璃熔制机理的认识和指导实际生产。     

Recent Development in Improving Energy Efficiency of Glass Furnaces

The energy required for continuous glass melting usually accounts for about 30 -75% of the total energy consumptions supplied to the glass industry, and the energy cost contributes to about 10 25% of total glass manufacturing cost depending upon the type of glass and manufacturing efficiency. Typically, energy efficiency of glass furnaces offers major opportunities for manufacturing cost reduction. Significant rising of energy cost, environmental requirements for clean air and pressure for reducing global warming and carbon dioxide emissions, as well as the cost of capitals are main drivers for the technology developments. In this paper, energy efficiency of glass furnaces is discussed. Technology developments in selective batching, oxy -fuel firing with preheating batch and cullet, non - conventional advanced melting systems, such as segmented glass melting and submerged combustion melting, as well as using math modeling to optimize fuel distribution for energy savings are presented.     

Refractories Quality Improvement for Glass Industry Upgrading

1 Glass Industry and Refractories Industry Closely Connect1.1 Glass Development Drives Refractories ProgressRefractories are indispensable to glass industry; the rapid development of glass industry drives the     

浮法玻璃生产线设备监造实务

介绍了浮法玻璃生产线设备退火窑及过渡辊台的监造过程,同时为我国的浮法玻璃生产设备进入欧洲市场提供了一定的质量保证,为以后的设备监造积累了经验。     

REFINED METHOD OF CONTROL OF CORDINESS AND WORKABILITY OF GLASS DURING PRODUCTION*

Many glass plants obtain daily measurements of the density or specific gravity of the glass in each furnace. Small daily fluctuations of about ±0.0010 density unit are usually taken for granted, while pronounced changes within a two- or three-day period are a matter of concern; but heretofore neither criteria of permissible variability nor rules for interpretation of the data have been in general use. In the present work, the control-chart method of statistical analysis of past data has been applied to data from ten glass furnaces. Small daily fluctuations of density are found to be statistical in character, and the predominant cause of large variations is found to be in the batch house. The rational subgroup sample to be used in analyzing such variations and in operating a control chart is found to be a subgroup of three consecutive daily density values obtained from a particular furnace. Using this subgroup, the average 3-day range of density for the ten furnaces varied from 0.0006 to 0.0023, and the corresponding 3-sigma limits for daily variation from the central line density were ±0.0011 to ±0.0040. A typical value for the average 3-day range of density is 0.0012 and a value no larger than this is a reasonable goal for a glass container plant. The use of control charts for maintaining a state of statistical control of density during production is illustrated for four furnaces over a 2- to 6-month period. Many assignable causes of variation were found in the batch house, usually in the scales; other assignable causes were changes in cullet and in raw materials, changes in firing of the furnace, and laboratory errors in measurement of the density. Present experience indicates that it is difficult to maintain a state of statistical control with the types of batch-weighing equipment in use in some plants. The importance of control, however, was demonstrated for two furnaces in two different plants by the fact that cordiness increased with increasing 3-day range of density. When the density was not maintained under statistical control in one plant, trouble was experienced with checks in the ware. The use of control charts for keeping lack of control within tolerable limits is discussed for one furnace where the variations were small and the control limits narrow. The range was held under control, but the density showed “trends” and went out of control. In this instance, the 3-sigma control limits for variation of daily values from the central line density were ±0.0011, corresponding to ±0.09% replacement of lime by silica. Inasmuch as composition changes in excess of ±0.09% are tolerable in the present state of the art, a modified control limit corresponding to a composition change of approximately ±0.25% is suggested, the corresponding density limits being ±0.0030. When the 3-sigma limits for density are less than, this value, modified limits may be used, although the 3-sigma limits for range are retained. When the 3-sigma limits are greater than ±0.0030, it is most desirable to maintain strict statistical control, and efforts should be made to reduce the variability; otherwise there may be excessive cordiness and other difficulties in fabrication of the ware. In some instances, a reduction in variability will require major repair of batch handling and weighing equipment or a new batch-house weighing installation. Other subgroup methods and other sources of variability are also discussed. Control charts on density are of practical utility to plants. “Assignable-cause” variations are easily distinguished from unimportant, normal variations. The use of 3-sigma action limits keeps investigation of fluctuations to a minimum, and sets troubleshooting, when it is necessary, on the right track. The charts, furthermore, are a useful guide toward a permanent reduction of the variability. They should be helpful to management in striking an economic balance among tonnage pulled, glass quality, and capital expenditures for improvement of batch mixing and handling and other changes. The time required to maintain a chart for one furnace is about one day for past-data analysis, one minute each day for plotting, and not more than one day per month for current analysis, review, and adjustment.     

全氧燃烧玻璃熔窑耐火材料的研究进展

全氧燃烧熔窑可节约燃料,减少NOX排放,降低对环境的污染,提高玻璃质量,提高火焰温度、熔窑熔化能力及熔窑产量,并降低了熔窑的建设费用,提高了熔窑使用寿命。优质浮法玻璃和高附加值特种玻璃也要求采用更为先进的燃烧工艺和玻璃熔制工艺。分析了全氧燃烧窑内大量碱蒸气和水蒸气的增加对胸墙、池壁、大碹等关键部位耐火材料的侵蚀及全氧燃烧熔窑耐火材料选材,对600 t/d浮法玻璃熔窑耐火材料使用进行对比分析,并对全氧燃烧玻璃熔窑耐火材料现状及前景进行了展望。     

全氧燃烧技术在玻璃窑上的应用

全氧燃烧技术在玻璃窑上的应用于云林，周志豪（上海建材学院０２２４３４）ＦｕｌｌＯｘｙ－ＦｕｅｌＣｏｍｂｕｓｔｉｏｎＴｅｃｈｎｃｌｏｇｙ￥ＹｕＹｕｎｌｉｎ；ＺｈｏｕＺｈｉｈａｏ（ＳｈａｎｇｈａｉＩｎｓｔｉｔｕｔｅｏｆＢｕｉｌｄｉｎｇＭａｔｅｒｉａｌｓ）...