 a 12% increase in pull rates, increased machine speeds averaging one to two bottles per minute, and a slight increase in pack, as well as an increased surface brilliancy and sheen of the final product.2
In other parts of the world, glass manufacturers were also starting to realize the benefits of lithium. In the late 1980s and early 1990s, trials at container glass manufacturing plants in Asia, the UK, Germany, Switzerland, Italy and France all showed that lithium additions between 0.03 and 0.20% by weight provided energy savings in the range of 4-10%, as well as increased production speed and reduced defects. In 1990, Kirin Brewery in Japan reported a 7.5% increase in pull without increased energy consumption using 0.2 wt% glass-grade spodumene.3 In 1994, trials at a container glass manufacturing plant in Central America showed that production was increased 11% with a 3% reduction in energy and equivalent quality compared to the glass without the lithium addition, while trials at a North American container glass manufacturing plant showed increased quality (decreased checks) along with a 5% savings in energy consumption at the same production levels used prior to the lithium addition.4
More recent trials at glass container and tableware manufacturing plants have further substantiated the idea that lithium can provide energy savings, increased product quality, higher throughput and other benefits in glass manufacturing.
Over the last several years, a number of glass container and cosmetic glass manufacturers in Asia have begun using spodumene in production and have increased their furnace capacities by 20 to 25%, reduced their rejection rates and eliminated the problem of weathering in glass. These manufacturers have also achieved enhanced glass brightness and a lower seed count, which has enabled them to increase sales.
According to Sheth, 0.1 wt% Li2O can provide approximately the same melting effect as a 10% cullet addition to the glass. With the unavailability of high-quality cullet in some countries, lithium is gradually becoming accepted as a better choice since it also provides other benefits that are not achieved with cullet.
"The increased batch costs are typically recovered through a higher glass yield; thus the unit cost of bottles remains largely unchanged or lower, depending on the location and the costs of other raw materials and fuel," Sheth said.
Why Isn't Everyone on Board?Despite the success stories from manufacturing facilities around the world, many glass manufacturers have been reluctant to consider the use of lithium as an energy-saving solution. A number of the manufacturers that ran lithium trials early on have gone out of business or been acquired by other companies, and today's companies don't appear to be eager to change their product formulations. "[The U.S. industry] seems fixated on the ‘hardware' of glass and ceramic manufacturing and so far has shown no inclination to consider energy reduction improvements through batch adjustments," said Merivale.
Part of the problem is the cost-and perceived cost-of lithium. When many of the early trials were conducted, lithium was considered too costly to implement on a regular basis. However, suppliers have noted that the price of lithium carbonate has dropped considerably over the past several years, and other lithium-bearing ores have also become more affordable. Additionally, data from a number of plant trials have indicated that the energy savings and other benefits that can be achieved with the lithium additions often more than make up for any added material cost.
Another concern for many glass producers is the effect of lithium additions on the refractories inside the furnace. However, a European glass research lab has shown that small additions of lithium-up to 0.3 wt% Li2O-in glass does not corrode refractories at same furnace load or temperature used previously, and in fact can enhance refractory life when it is used to replace soda or potash in the glass batch. Additionally, lithium does not volatilize and therefore poses no threat to the fu