The energy intensive glass industry accounts for approximately 1% of total industry energy consumption.*1
Taking this fact seriously, the AGC Group is proactively implementing measures to save energy in its manufacturing process, in addition to contributing to prevent climate change through its glass technology.
As a result of improving the process, CO₂ emissions from Asahi Glass (unconsolidated) decreased by 36% in fiscal 2008 from the fiscal 1990 level.
We cannot, however, deny the fact that there is a limit to such improvements. Accordingly, we will review the glass manufacturing method itself and strive to reform it drastically to reduce our use of energy in a substantial manner.

*1 Actual result in Japan

Glass manufacturing process (float method)

Glass manufacturing gives the biggest impact on the environment mainly due to the process of melting materials, such as silica sand and soda ash, by fuel oil to produce chemical reactions, as well as the process of keeping the melted materials in the melting tank for long hours to manufacture homogenous glass without air bubbles. During these processes, the large melting tank of over several ten meters in length, has to be kept at a high temperature for many hours.

Reducing CO₂ Emissions by Improving the Manufacturing Process

Fuel conversion

Some of our facilities have replaced heavy oil used for glass melting with natural gas. Through the use of natural gas, we can reduce CO₂ emissions from combustion by 20% compared with the use of heavy oil. Moreover, we can reduce the emissions of sulfur oxide (SOx) from glass melting to nearly zero, which will in turn reduce the total emissions of SOx.

All-electric melting

In the all-electric melting method, electric current is directly applied to glass materials to melt them. This method is suitable for relatively small furnaces. Materials are heated directly instead of indirectly by the heat radiated from the combustion flame, and this improves the energy efficiency. At present, we are operating all-electric furnaces in Japan, Thailand, and other regions.

Total oxygen combustion

The total oxygen combustion method uses only oxygen for fuel combustion in glass manufacturing. This method is more energyefficient because it does not heat nitrogen, which accounts for approximately 80% of air and is not necessary for combustion.
Also, this method is effective in reducing NOx because the combustion gas contains almost no nitrogen, thus helping to curb NOx generation itself. Asahi Glass introduced this method to the Keihin Plant in 2001, a first in flat glass production in Japan. This has resulted in reducing energy consumption and CO₂ emissions per unit production of glass by about 30% each.

• Effects of the Total Oxygen Combustion Method

Taking on the Challenge of Halving CO₂ Emissions from Glass Melting

In-flight melting

In-flight melting is a method of melting glass materials in air using plasma combustion flames, that could reach up to 10,000°C. This method enables the instant completion of the melting process, which usually consumes a lot of energy. Specifically, granular materials with pre-adjusted composition are injected into the furnace from above and the materials pass through between the electrodes to be instantly melted by plasma combustion flames.
By adopting in-flight melting to change the glass manufacturing method itself, we will be able to halve CO₂ emissions from glass manufacturing. Also, we will be able to downsize the melting tank to a width of several meters.

* Research has been conducted since 2005 to develop innovatively energy-saving glass melting technology (in-flight-melting technology), commissioned by the New Energy and Industrial Technology Development Organization (NEDO). In 2008, we launched a project, targeted for completion by 2013, to identify the equipment necessary for practical use of the technology, and to study possible glass quality and the feasibility of mass production by the new melting method.

Mechanism of in-flight melting