Osamu Sakamoto

An innovative energy-saving in-flight melting technology and its application to glass production.

Abstract The conventional method used for glass melting is air-fuel firing, which is inefficient, energy-intensive and time-consuming. In this study, an innovative in-flight melting technology was developed and applied to glass production for the purposes of energy conservation and environmental protection. Three types of heating sources, radio-frequency (RF) plasma, a 12-phase alternating current (ac) arc and an oxygen burner, were used to investigate the in-flight melting behavior of granulated powders. Results show that the melted particles are spherical with a smooth surface and compact structure. The diameter of the melted particles is about 50% of that of the original powders. The decomposition and vitrification degrees of the prepared powders decrease in the order of powders prepared by RF plasma, the 12-phase ac arc and the oxygen burner. The largest heat transfer is from RF plasma to particles, which results in the highest particle temperature (1810 °C) and the greatest vitrification degree of the raw material. The high decomposition and vitrification degrees, which are achieved in milliseconds, shorten the melting and fining times of the glass considerably. Our results indicate that the proposed in-flight melting technology is a promising method for use in the glass industry.

Interaction of water with glass at very high temperature under dynamic condition and the properties of the obtained glass surface

Abstract A conventional soda–lime–silicate glass-melt was treated with water vapor during the course of cooling from 1300 to 600 °C in less than a minute. The water vapor was generated spontaneously from a wet porous carbon substrate beneath the glass-melt. Within the treated glass surface, sodium was found to be depleted more and deeper than calcium. The morphology of the treated surface was found to be very smooth and homogeneous without defects (mean roughness Ra=0.26 nm ), unlike the water treatment at lower temperatures where the glass surface suffers from corrosion. As a consequence of the lower alkali concentration and homogeneous morphology, water vapor-treated surface showed improved chemical stability. The results are considered to be brought about by the combined effects of the alkali ion depletion through ion-exchange with hydronium ion, hydration, followed by the repeated hydrolysis and reformation of SiOSi bond. These processes are believed to be accelerated significantly at high temperatures.