Sandia LabNews

Glass research advanced

Review clarifies priorities for glass research partnerships

The adage "waste not, want not" underlies research geared to increase efficiencies in one of the most energy-intensive manufacturing industries — glassmaking.

In 1996, leaders in the glass industry partnered with DOEs Office of Industrial Technologies to foster the development and use of advanced technologies and processes. Researchers are investigating ways to sustain high-quality yield while decreasing energy use and protecting the environment.

About 70 glass-manufacture researchers from around the country recently met at the Sandia’s Combustion Research Facility for the industry’s sixth annual review of programs, in which projects significance to industry needs is assessed. In the future, greater emphasis will be focused on grand challenges and on crosscutting technologies, which will provide greater energy savings and synergies across multiple industries, said Elliott Levine, glass team leader in DOEs Office of Industrial Technologies.

Since 1998, glass companies have joined together through an umbrella organization, the Glass Manufacturing Industry Council (GMIC, The DOE began supporting small research projects at the national labs several years ago; the number has grown from three in FY00 to 12 in FY02, said GMIC executive director Michael Greenman.

Among the 17 talks were four presentations about work by Sandia CRF investigators and their industrial partners. Mark Allendorf (8361) and Jill Aaron of the Pittsburgh-based PPG Industries, Inc. discussed their studies to understand and optimize glass coatings. Pete Walsh (8361) described the conceptual design and engineering of a glass-melting laboratory proposed for the CRF. Mark also discussed modeling and analysis of corrosion affecting the longevity of glass-melting furnaces. Pete, meanwhile, presented a fourth project detailing studies of how combustion and chemistry variations affect both emissions and corrosion of a commercial glass-melting furnace operated by a major California wine producer.

Aaron pointed out that 110 million square feet of flat glass is coated each year — mainly for low-emissivity and solar-control windows, but also for solar cells, computer screens, windshields, and photocopy machines. Most of the coating is produced by a process called chemical vapor deposition. Her three-year project with Mark is intended to identify a process design that would double the current efficiency. (The main issues are that only 11 percent of the chemicals are deposited, leading to some $23 million costs a year for waste disposal, and deposition defects lead to about 15 percent of the coated glass being discarded.)

Mark said that studies of the reacting flow of tin oxide, the main coating for flat glass (also used for containers), have led to real insight into how the reactions are occurring. The investigators have calculated accurate predictions of the chemical process for more than 75 different kinds of tin compounds, and will try to optimize process conditions using this knowledge (possibly through real-time, online process monitoring).

The work is significant, Mark said, because coated glass is a "very highly value-added product," and the results will be available to benefit the industry as a whole.

A proposed glass-melting laboratory at the CRF just completed engineering design. The lab’s focus evolved in a 1999 survey of needs from glass quality to examination of heat transfer issues, Pete said. The DOE funded a conceptual design, and PPG contributed significant in-kind services to complete the engineering design.

As envisioned, the industrial research lab would produce up to 25 tons of glass a day in a 6-by-13-foot melting area. Advanced, noninvasive optical diagnostic equipment would be mounted to one side of the melting area, and more traditional sampling equipment would be deployed from the other side.

To build out, the lab would require just under an estimated $10 million, Pete said, and could deliver its first results to industry in 18 months.

The pilot-scale research lab would offer several benefits, Pete said. It could explore the use of oxygen firing, which has been adopted widely in the past decade for greater efficiency and reduced emissions (but which accelerates furnace corrosion). "The full potential of oxygen firing for increased efficiency and productivity in large furnaces has not yet been realized," he said.

The work on heat transfer could be carried over to industries such as aluminum, which also employs oxygen firing, thus benefiting other energy-intensive industries.

Oxygen firing was also a topic of investigation by Mark. Principal investigator George Pecoraro of PPG said in the first four years of the five-year project, they’ve been able to identify factors leading to corrosion and predict reaction rates.

"If you can put equations on anything as complicated as this," Pecoraro said, "you really start to understand it, and we’ve really been pleased with the work."

Mark said they’ve learned there are at least five processes contributing to corrosion of the brick ceilings of the glass-melting furnace. Corrosion is accelerated by the presence of water and sodium hydroxide above the melt (whose concentrations vary with temperature). The findings have been submitted to the Journal of Glass Science and Technology.

"We’ve learned it doesn’t take much of a fluctuation (in sodium hydroxide) to either turn on, or turn off, corrosion," Mark said. The problem affects overall efficiencies, Pecoraro said, since faster corrosion leads to more frequent furnace rebuilds — at a cost of about $10 million each time.

For slightly more than a year, several Sandians under Pete’s guidance have been working with Gallo Glass to prototype diagnostic equipment for process control so emissions and corrosion will be lessened.

The equipment under investigation is a continuous monitor that detects metals in the flue gas. Field tests (two have been conducted so far for a total of 2.5 weeks) correlate the presence of metals such as sodium or potassium in the flue gas with overall observed efficiencies and operating conditions.

Based on the results of earlier work at Gallo Glass during 1997 and 1998, the researchers also developed a model to assess tradeoffs from modifying operation to minimize development of corrosive gases (such as sodium hydroxide) and thus reduce ceiling corrosion rates.

Pete has accepted a faculty position at the University of Alabama at Birmingham, so Linda Blevins (8361) will continue to oversee the remaining 18 months of this three-year research project.