Optimization of Molybdenum Electrodes for Glass Melting

• Main Author: Liu, WenDi
• Other Authors: Diran Apelian, Advisor
• Format: Others
• Published: Digital WPI 2015
• Subjects: molybdenum; glass melting
• Online Access: https://digitalcommons.wpi.edu/etd-dissertations/208; https://digitalcommons.wpi.edu/cgi/viewcontent.cgi?article=1207&context=etd-dissertations

The U.S. glass industry is a $28 billion enterprise and millions of tons of glasses are melted each day by different heating techniques, such as conventional oil fired furnaces or via electrical heating. The share of electrical heating is bound to rise steadily because it is cleaner and more energy efficient. Due to this situation molybdenum will play a significant role in electrical glass melting, since it is the most frequently used electrode material to deliver the electricity into the glass melts. Although it has a high melting point, high electrical and thermal conductivity and a low coefficient of expansion, molybdenum electrodes fail because of lack of sustainability during the glass melting process. Melt reaction with electrodes is the fundamental barrier to higher melting temperatures. Glass manufacturers have suggested that the need for better performance of molybdenum electrodes will see a rapid advancement in the use of electric heating system in the U.S. This work first focused on post-mortem analysis on used molybdenum electrodes with and without the current load in order to establish failure mechanisms for molybdenum during glass melting. It was determined that service life of molybdenum electrodes are limited by poor oxidation and corrosion resistance of molybdenum with redox reactions. Various studies have shown that the failure mode for molybdenum electrodes is a complex phenomenon. It depends on chemical composition of the electrode, current density and frequency, and chemical composition of the glass melt, specifically polyvalent ions that may be present in the melt. In this work, the MoSiB coating was validated as a promising protection for molybdenum from oxidation attack. Several molybdenum and molybdenum based-alloy electrodes were tested in different molten glasses in the remelter furnace to optimize the structural characteristics that are needed in Mo electrodes. Moreover, the quantitative data and fundamental knowledge gained in this work is being applied for molybdenum electrode production to extend its service life and also improve its quality.