Electro-Melting of Special Glasses
Development of Electro-Melting Technique of Glasses Containing Volatile and Chemical Reducible Agents
Tech Area / Field
- MAT-SYN/Materials Synthesis and Processing/Materials
3 Approved without Funding
Institute of Electronic Materials, Armenia, Yerevan
- CNRS / Université de Rennes 1, France, Rennes\nUniversita' Degli Studi di Modena / Dipartimento Ingegneria dei Materiali e dell'Ambiente, Italy, Modena
Project summaryThe Project's purpose is development of glass-melting technique in a new pilot design's all-electric glassmelters equipped with metal electrodes without water cooling as well as with ceramic electrodes providing reliable hot contact with current-carrying cable. Such glass processing is intended for glasses containing volatile and chemical reducible agents.
Application of electric melting as a progressive and environmentally appropriate technology for glasses, which are containing volatile and easily reducible agents (B2O3, As2O3, Sb2O3, R2O (Li2O, Na2O, K2O), P2O5, F, S, Se, NiO, CoO, Cr2O3, CuO, TiO2 etc.) enables to sharply reduce a scarce materials losses and a toxic emissions (10-20 times greater than in case of a gas-flame melting), to finely control a melting temperature conditions, to increase a furnace efficiency and to produce an articles with guarantee of required glass homogeneity. Electrical glass-melting’s processes are nevertheless connected with a number of shortcomings. At use of molibdenic water-cooled electrodes the refractory materials are under severe environment conditions (high temperatures, corrosive liquid melts and thermal gradients), that give rise to early aging as well as to occurrence of various type's cracks and furnace service life decrease. At use of ceramic electrodes the cardinal problem lies in a reliable hot contact's assurance of an electrode with current-carrying cable. The refractory masonry of flow channels is under intensive mechanical stream's action of hot fluid glass and fails quickly.
Thus there are some restrictions at a choice of glass composition for electro-melting:
- Low glass attack resistance of electrode and refractory materials at melting of compositions with a high content of volatile components,
- Absence of a reliable method of measurement of high-melting glass’s resistivity in temperature ranges 1200-1800 C. Last factor is important for all-electric glassmelter's designing. Function dρ/dT > t (the self-regulated ability of glass melts) is a defining technological parameter of electro-melting process.
The decision of the listed problems is the major task of the present Project.
In present Project the development of technological basis of electro-melting of some basic compositions of known technical glasses is provided for:
a) during use of molibdenic electrodes:
- alkali-alumina-borosilicate compositions, which are containing (1-30)% B2O3, (3-15)% R2O (Li2O, Na2O, K2O),
- glasses, which are containing: (3-10)%F, (1-3)%As2O3, (1-3)%Sb2O3, (1-4)% Se;
b) during use of SnO2 electrodes:
- the glasses, which are containing oxides of elements of variable valency: more than 4% Fe2O3, more than 0,5% CuO, more than 1% NiO, more than 2% Cr2O3, more than 2% MnO and 1-7% TiO2.
Before to start electro-melting it is necessary to test electroconductivity, viscosity and density of glasses of the mentioned compositions, especially in a melting and forming temperature range. At the same time the mechanisms of dependences of the indicated properties from temperature and glass composition will be revealed, and also the glass attack resistance of refractory and electrode materials will be investigated. Processing of the received results will give an opportunity of precise modeling and a choice of all-electric glassmelter's design, and of receiving maximum of the theoretical and practical conclusions, which are generalizing the phenomena taking place at electro-melting.
In present Project the development of electro-melting of the some above mentioned basic compositions of small-scale and -tonnage special glasses in a pilot all-electric glassmelters of new designs with using of molibdenic electrodes without water cooling and ceramic SnO2 electrodes with current-carrying elements, which will allow realization of melting of glasses with various self-regulated abilities, is provided for.
In furnaces with use of metal electrodes without water-cooling it will be possible to save a lot of electric power, to exclude emergencies, to avoid use of the expensive ponderous equipments, that are traditional for water-cooling system, to reduce temperature heterogeneity and connected with it self-regulated ability, and also to increase durability of refractory materials. For appraisal of self-regulated ability the development of a high-temperature method for determination of specific resistance in a temperature range 1200-1800ºC is provided for.
In case of use of ceramic electrodes development and application of current-carrying cables, that are ensuring reliable hot contact with electrodes, is provided for.
In this Project the development of principles of protection of flow channels against corrosion, which is connected with intensive influence of hot glass flow, is provided for.
In the course of realization of the project the following theoretical results are expected:
- Analysis of high-temperature processes of glass making. Testing of their basic properties (physicochemical, electrical, thermal, mechanical and optical). Researches of theory for definition of self-regulated ability of glass melt, what is important in process of furnace modeling.
- Theoretical study of electroconductivity of glasses of various matrixes and revealing of mechanism of change of electroconductivity, viscosity and density of melts in a wide temperature range.
- Analysis of redox process in the presence of easily reducible components in glass.
- Research of physicochemical processes of volatilization of various components during electro-melting of glasses of various matrixes.
- Research of the nature of electrochemical processes of high-temperature interaction of various electrode and refractory materials with the melt depending on composition of glasses, current density and temperature.
- Research of processes of protection against high-temperature corrosion of electrode and refractory materials at electro-melting of glasses.
- Research and choice of optimal design of molibdenic and others metallic electrodes without water cooling.
- Research and choice of optimal design of high-temperature current-carrying cables of ceramic electrodes.
- Modeling and choice of optimal design of all-electric glassmelters.
- The method of measurement of electroconductivity of glasses in wide temperature range (1200-1800ºC) will be developed.
- The metal electrode's design without water cooling for glass electro-melting will be developed.
- The design of high-temperature current-carrying cables of ceramic electrodes for glass electro-melting will be developed.
During of the Project execution the following practical results will be received:
According to the purposes and tasks of ISTC the project will promote:
- reorientation of highly skilled scientists on the solving of peace problems;
- integration of scientists into the international community;
- facilitation to the Commonwealth of States in environmental problems solving, that are occurring at glass making;
The staff of scientists of Scientific Industrial Enterprise of Science of Materials long time has been engaging in development and manufacture of glasses and glass-ceramic materials. The authors of the Project invite scientists, research organizations, and also private experts from USA, the countries of European Community, Japan, Korea, and Norway to collaboration. We also offer to hold joint seminars and scientific research.
The International Science and Technology Center (ISTC) is an intergovernmental organization connecting scientists from Kazakhstan, Armenia, Tajikistan, Kyrgyzstan, and Georgia with their peers and research organizations in the EU, Japan, Republic of Korea, Norway and the United States.
ISTC facilitates international science projects and assists the global scientific and business community to source and engage with CIS and Georgian institutes that develop or possess an excellence of scientific know-how.